Farming Marine Shrimp in Recirculating Freshwater Systems

Farming Marine Shrimp in Recirculating Freshwater Systems

Florida Department of Agriculture and Consumer Services BOB CRAWFORD, COMMISSIONER Contract No. 4520 1999

Prepared by

Harbor Branch Oceanographic Institution Peter Van Wyk, Megan Davis-Hodgkins, Rolland Laramore, Kevan L. Main, Joe Mountain, John Scarpa

Farming Marine Shrimp in Recirculating Freshwater Systems Prepared by Harbor Branch Oceanographic Institution

Table of Contents Farming Marine Shrimp in Freshwater Systems: An Economic Development Strategy for Florida – Final Report – Peter Peter Van Wyk Introduction 1 System Descriptions 3 Production Trials 10 Results 12 Discussion 19 Recommendations 22 Literature Cited 23 Figures 24 Chapter 1

Chapter 2

Introduction - Kevan L. Main and Peter Van Wyk An Overview of the Development of Shrimp Farming New Approaches and Considerations for Shrimp Farming Freshwater Culture of Marine Shrimp Literature Cited Getting Started - Megan Davis-Hodgkins, John Scarpa and Joe Mountain Introduction Planning Your Aquaculture Business Expectations Research and Training Production Planning Market Feasibility Marketing Farm-Raised Shrimp Business Plan Executive Summary Business Description Market Analysis Management Team Financial Information Milestone Schedule Appendix Demonstration or Pilot-Scale Operation Commercial-Scale Operation Water Selection Criteria Permitting Literature Cited ii

33 33 35 36 37

39 39 39 40 40 41 44 44 45 46 46 46 46 47 47 47 47 47 48 49 50

Chapter 3

Greenhouse Construction – Megan – Megan Davis-Hodgkins Introduction Zoning and Permitting General Construction Site Preparation Anchor Layout Assembling Arches Gable Ends Covering the Greenhouse Flooring Raceway Installation Systems and Filtration Equipment

Chapter 4

Principles of Recirculating System Design - Peter Van Wyk 59 Introduction 59 The Culture Tank 59 Circular Tanks 60 Raceways 60 Racetrack Configuration 61 Water Depth 63 Artificial Substrates 64 Standpipes and Drain Structures 65 Solids Filtration 66 Sources and Types of Solid Wastes 66 Consequences of Excessive Solid Wastes 66 Solid Waste Filters 67 Sedimentation Tanks 68 Hydrocyclones 69 Tube Settlers 69 Microscreen Filters 70 Bead Filters 72 Sand Filters 73 Foam Fractionators 74 Ozone 76 Biofiltration 77 Sources of Ammonia and Nitrite 77 Ammonia and Nitrite Toxicity 78 Mechanisms for Controlling Ammonia 79 Water Exchange 79 Plant Uptake 79 Nitrification

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51 51 51 52 52 52 53 53 54 56 56 58

Chapter 4 - Continued Types of Biofilters Submerged Biofilters Trickling Biofilters Rotating Biological Contactors Bead Filters Sand Filters Fluidized Bed Biofilter Sizing a Biofilter Pumps Required Flow Rates Calculation of Friction Losses and Total Head Pump Sizing Procedure Pump Performance Curves Trimmed Impellers Literature Cited Chapter 5

Harbor Branch Shrimp Production Systems - Peter Van Wyk Design Objectives System A Greenhouses Culture Tanks Drains Pumps Sand Filters Aeration System B Greenhouses Culture Tanks Single-Phase and Three-Phase Production Systems Systems Water Treatment Systems Pumps Aeration Water Supply Retention Ponds Literature Cited

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81 81 83 84 85 86 87 90 91 93 93 95 95 95 96 99 99 100 100 101 103 104 104 105 105 106 106 107 108 110 112 112 113 113

Chapter 6

Receiving and Acclimation of Postlarvae - Peter Van Wyk Purchasing Postlarvae Preparations for Receiving Postlarval Shrimp Acclimation Systems Acclimation Equipment Requirements Acclimation Stations Receiving the Postlarvae Acclimation Procedures Acclimation in Shipping Bags Acclimation in AcclimationTanks Acclimation Schedules Calculating Water Exchange Requirements Literature Cited

Chapter 7

Nutrition and Feeding of Litopenaeus Litopenaeus vannamei in Intensive Culture Systems - Peter - Peter Van Wyk 125 Elements of a Good Feeding Program 125 Nutritional Requirements Protein Requirements 125 Lipids 127 Carbohydrates 128 Vitamins 128 Minerals 129 Shrimp Feeds 129 Formulated Diets 129 Feed Processing 130 Pellet Stability 131 Pellet Diameter 131 Feed Application 132 Feeding Rates 132 Feed Tables 133 Demand-Based Feeding 134 Feeding Frequency 135 Feed Distribution 135 Feed Conversion Ratios 136 Feed Storage 136 Sources of Shrimp Feeds 137 Literature Cited 139

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115 115 116 116 117 118 119 120 120 120 121 121 124

125

Chapter 8

Water Quality Requirements and Management – Peter Van Wyk and John Scarpa 141 Introduction 141 Water Quality Testing During Site Selection 142 Salinity 144 Temperature 146 Dissolved Oxygen 148 pH Dissolved Carbon Dioxide 152 Ammonia 153 Nitrite Nitrate Hardness 159 Alkalinity 160 Hydrogen Sulfide 160 Iron 161 Chlorine 161 Selected Literature 161

Chapter 9

Shrimp Health Management: Issues and Strategies - Kevan L. Main and Rolland Laramore Introduction Variables to Consider in Determining the Health of Your Shrimp Survival Rates Mortality Rates Growth Rates Size Variation Feed Conversion Ratio Appearance of Shrimp Effect of the Environment on Shrimp Health Health Evaluation Tests Stress Tests Gill Examination Gut Content Examination Detecting Diseases and Diagnostic Techniques Factors Leading to Losses and Disease Outbreaks During Growout

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163 163 164 164 164 164 164 164 165 165 165 165 165 165 166 166

Chapter 9 - Continued Poor Quality Postlarvae Postlarval Acclimation Procedures Management Strategies that Lead to Disease Problems Dietary Issues Human Factors Environmental Factors Factors to Consider in Disease Prevention Site Selection and Environmental Conditions Feed Quality Biosecurity Probiotics Transfers and Handling Record Keeping Personnel Practical Approaches to Disease Control Eradication of Viral Diseases Important Shrimp Pathogens Overview Common Disease Concerns During Growout Infectious Hypodermal and Hematopoietic Necrosis Virus Runt-Deformity Syndrome Taura Syndrome Virus White Spot Syndrome Virus Yellowhead Virus Vibriosis Necrotizing hepatopancreatitis Mycobacteriosis Epicommensal fouling disease Black spot disease Gas Bubble Disease Dissolved Oxygen Crisis Literature Cited

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166 166 166 167 167 167 167 168 168 168 168 169 169 169 169 170 170 170 171 171 172 172 172 173 173 174 174 174 175 175 176 177

Chapter 10

Appendix A

Appendix B

Economics of Shrimp Culture in Recirculating Aquaculture Systems - Peter VanWyk 179 Introduction 179 Baseline Assumptions 179 Facility Description 179 Investment Requirements 182 Land 182 Buildings and Improvements 182 Tanks and Sumps 183 Machinery and Equipment 184 Office Equipment 186 Total Investment Requirements 186 Process Description and Production Assumptions 188 Production Schedule 189 Expected Production 191 Production Inputs and Operating Costs 191 Seed 191 Feed 193 Labor 194 Energy 194 Maintenance 195 Marketing Assumptions 195 Revenues 196 Cash Flow 196 Income Statement 198 Breakeven Analysis 200 Investment Analysis 200 Sensitivity Analysis 201 Survival 201 Growth Rates 202 Seed Costs 204 Market Prices 206 Conclusion 207 Literature Cited 208 Ammonia Mass Balance - Peter VanWyk Ammonia Mass Balance Analysis System Ammonia Mass Balance Estimating Required Recycle Flow Rates Based On Ammonia Mass Balance Example Literature Cited Friction Loss Tables Flow Velocity & Friction Loss-Schedule 40 Pipe viii

209 210 211 213 215 216 217 218

Friction Losses Through Pipe Fittings In Terms of Equivalent Lengths Of Standard Pipe Friction Loss Nomograph

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219 220

Florida Department of Agriculture and Consumer Services BOB CRAWFORD, Commissioner

For additional production, technical or regulatory information contact:

Division of Aquaculture 1203 Governor’s Square Boulevard, Fifth Floor Tallahassee, Florida 32301 Tel: 850-488-4033 Fax: 850-410-0893

The information, procedures and conclusions described by this report are the sole responsibility of the authors. The Florida Department of Agriculture and Consumer Services does not approve, recommend nor endorse any proprietary product, material or process mentioned in this publication. 01/00

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“Farming Marine Shrimp in Freshwater Systems: An Economic Development Strategy for Florida: Final Report” FDACS Contract #4520 Principle: Investigator: Investigator: Peter M. Van Wyk Harbor Branch Oceanographic Institution 5600 Highway U.S. 1 North Ft. Pierce, Florida 34946

Introduction: In recent years there has been renewed interest in shrimp culture here in Florida due to technological developments that now make it possible to culture Litopenaeus vannamei indoors in near-freshwater near-freshwater recirculating aquaculture systems. systems. Harbor Branch and others have demonstrated in recent years that L. vannamei can be successfully produced in water with chloride concentrations as low as 300 ppm. Water with chloride levels this low is generally classified as freshwater and can be used to irrigate most crops. The significance of this is is that shrimp production production can now be practiced on cheaper, non-coastal agricultural land. New advances in the technology for producing L. vannamei indoors in high-density recirculating aquaculture systems now allows for yearround production of this species even in temperate climates with relatively cold winters. Year-round production improves the economic potential of an enterprise in several ways. The annual revenues of the operation are increased because year-round production increases annual productivity. Continuous harvesting facilitates facilitates direct marketing to retail markets, which may allow for a higher price to be received received for the product. Producing shrimp indoors in recirculating systems benefits the producer by significantly reducing the risk of exposing the shrimp to the viral diseases that have wreaked havoc in open coastal ponds throughout the world. In the wake of devastating epidemics of Taura Syndrome Syndrome Virus (TSV) and White Spot Syndrome Virus (WSSV), some shrimp farm managers in Latin America are considering switching to intenstive tank-based production systems because of the additional biosecurity these systems can provide. Indoor production systems provide the additional benefit of reducing crop loss due to predation. In addition, these systems significantly reduce the risk of accidental release of non-native shrimp into Florida’s coastal waters. The objective of the current study was to demonstrate the production technology required to successfully cultivate the marine shrimp, Litopenaeus vannamei, in freshwater recirculating aquaculture systems, and to evaluate the economic potential of this approach to shrimp culture.

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Final Report – Farming Marine Shrimp in Freshwater Recirculating Systems Production Systems:

Two different production systems were evaluated in this study: 1) a single-phase (direct stock) production system, system, and 2) a three-phase, partitioned production system. In a single phase production system shrimp postlarvae are stocked into a culture tank and remain in that same tank until final harvest. The stocking density in in the culture tank is based on the desired final harvest density plus overstock to compensate for expected mortalities. mortalities. Initially, the system biomass is extremely low relative to the carrying capacity of the system, which is only reached at the end of the production cycle. In a three-phase production system, the production process is divided into three distinct phases, each carried out in a different culture tank, or in different sections of a partitioned culture tank. The shrimp typically spend onethird of the total culture period in each of the three sections of the tank. Postlarval shrimp shrimp are initially stocked into a small nursery tank, representing 10-13% of the total culture area of the complete three-phase system. At the end of the nursery period (after 50-60 days) the juvenile shrimp are transferred to the second section of the tank, called the intermediate growout section. This section is larger larger than the nursery section, representing about 27-30% of the total culture area. The shrimp remain in in the intermediate growout section for another 50-60 days before being transferred to the final growout section, which occupies 60% of the total culture area. After another 50-60 day period the shrimp are harvested for market. The objective of a three-phase production system is to utilize the available production area more efficiently by operating closer to the carrying capacity of the system for a greater percentage of the culture period. In a single-phase system the biomass is very low relative to the carrying capacity of the tank for the first first two-thirds of the culture cycle. The number of postlarvae stocked into the nursery section is determined by the projected harvest density of the final growout section, with overstocking to account for expected mortalities. mortalities. The amount of area devoted to each phase is calculated to allow the shrimp to continue to grow until they reach the end of that phase. When the shrimp are ready to be transferred to the next section they should be approaching the carrying capacity for the section they are in. The three-phase system permits higher production levels than can be achieved in a single phase system. Each section of a three-phase system is stocked at a density which will grow to the carrying capacity for the alloted area in one-third the amount of time it takes the shrimp in in a single-phase system system to reach the carrying capacity. Tank space is used more efficiently than in a single-phase system in which culture tanks are maintained at low densities throughout throughout the early part of the growout cycle. The production of a three-phase system should, theoretically, be 1.8 times greater than the production in a single-phase system, assuming survival survival and growth rates are equivalent between the two systems. systems. Although the area harvested for each crop is only 60% of the area harvested in a single-phase system, the final growout section of the 3-phase system is harvested three times for every harvest of the single-phase system. Increasing the harvest frequency has obvious advantages from a marketing standpoint, standpoint, and may also smooth out the cash flow for for the business. The potential disadvantages of a three-phase production system are the increased risk of mortality during the transfer process and potential density-dependent reduction in shrimp growth rates and survivals.

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Final Report – Farming Marine Shrimp in Freshwater Recirculating Systems

Greenhouse Recirculating Aquaculture Systems:

The objective of the Harbor Branch Oceanographic Institution (HBOI) shrimp culture program has been to develop a cost-effective indoor, freshwater production system based on a recirculating water treatment system. The principle that guided HBOI in the development of new system designs is: is: “Keep It Simple”. The ideal system should be simple to build using inexpensive, readily available materials, and should be operable by individuals with limited training training specific to systems operation. With this in mind, HBOI focused its its efforts on designing an inexpensive system capable of growing shrimp at moderately high densities (up to 150 shrimp/m2). These densities are significantly lower than the highest densities L. vannamei in more sophisticated recirculating (>600 shrimp/m2) that have been reported for L. systems (Davis and Arnold, 1998). The shrimp production systems utilized in this project represent two generations of system design. First generation systems systems at HBOI (System A) feature above-ground raceways and sand filters. Given their their simplicity, these systems systems perform surprisingly well, supporting 3 loading rates of up to 2.25 kg shrimp/m . However, sand filters are expensive to operate because they require inefficient, high-head pumps to push the water through the compacted sand filter media and because sand filter maintenance is very labor intensive. The cost of operating the pumps on these systems can be quite high because they operate on a continuous basis. The second generation systems systems at HBOI (System (System B) feature in-ground raceways and low-head water treatment treatment systems. The in-ground raceway should be less prone to heat-loss, reducing heating costs in the winter. Pumping costs in System System B are lower because the lowhead system design cuts the horsepower requirements by more than half. A second key objective of this study was to compare the productivity and economics of these two types of recirculation systems.

System Descriptions: System A System A is housed in a 30’ x 152’ Quonset-style greenhouse. The greenhouse consists of a series of arches arches or bows made made of 2” diameter galvanized steel pipe. The bows are anchored in concrete at their bases. The arches are supported by purlins running the length of the greenhouse connected by clamps to each rib. Cross-struts span span every second arch providing additional support. A double layer layer of 6-mil clear UV-resistant polyethylene polyethylene plastic material covers the greenhouse. The space between the two layers of plastic is inflated by means of a small blower. The two layers of plastic are highly efficient at collecting and retaining solar heat. The dead air space between the layers of plastic functions as an insulating layer. During the night, greenhouses with a single layer covering lose much of the heat collected during the daytime. Nighttime heat loss is greatly reduced when a double layer of plastic is used to cover a greenhouse. The improved heat retention retention justifies the added expense of the second layer of plastic and the inflation system. system. During the summer months an 80% shade cloth covers the outside of the greenhouse. The shade cloth minimizes algal growth within the raceways. The greenhouse is ventilated by two 1.5 hp extractor fans and by one 0.5-hp -3-


extractor fan mounted on one end of the greenhouse. The ventilating air air enters at the greenhouse at the opposite end through through two two mechanical mechanical louver windows. The fans and the louvers are thermostatically activated, providing a measure of automated temperature control to the greenhouse. The System A greenhouse contains four culture tanks, each operating on separate filter systems (Figure 1). Two of the culture tanks (H5-NE and H5-SE) are set up as single-phase culture systems and two tanks (H5-NW and H5-SW) are set up as three phase systems . H5 NE (single-phase), and H5-NW (three-phase) both measure 13.5’ x 56’., while (H5-SE and H5-SE (single-phase) and H5-NW (three-phase) both measure 13.5’ x 64’. The three-phase systems are subdivided into three sections. The nursery section of H5-NW (H5-NW1) measures 13.5’ x 6.5’, with the long axis of the raceway perpendicular to the long axis of the overall growout area. The intermediate growout section section (H5-NW2) measures measures 13.5’ x 13.5’. The final growout section (H5-NW3) measures measures 13.5’ x 36’. The nursery section of H5-SW (H5-SW1) measures 13.5’ x 7’. The intermediate growout section (H5-SW2) measures 13.5’ x 18.5’. The final growout section (H5-NW3) measures 13.5’ x 38.5’. Four-inch diameter bulkhead fittings positioned at the bottom of the walls dividing the three sections all shrimp to be transferred from one section to the next without being handled. The culture tanks consist of a wooden frame supporting a black 30-mil high-density polyethylene liner. The wooden frame is two board widths high and is built using 2”x12” boards of pressure-treated lumber supported by galvanized pipe set vertically in a concrete anchor. The vertical pipe supports are set on 4-ft centers. The arches forming forming the frame frame of the greenhouse support the outside walls of the culture tanks. The culture tanks are rectangular in shape and have been set up with a "racetrack" configuration. The racetrack configuration is essentially essentially a hybrid between a circular tank and rectangular tank. Each culture tank is set up with two drain outlets at either end of the tank, centered between the end wall and the sides sides of the tank. A center divider baffle has been positioned between the two drain outlets, and functions to separate water flowing down one side of the "racetrack" from the water flowing down the opposite side. The water in the tank flows in an elongated oval pattern, travelling down one side of the tank, circling around the drain outlet at one end, then travelling up the other side of the raceway and circling around the opposite drain outlet. Baffles have been placed in the corners of the tank to prevent

in

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Figure 1: Culture tank layout in System A. Upper two culture tanks are single single phase systems. Lower tanks are three-phase systems. systems. -4-


eddies from developing in the corners. The baffles help create a semi-circular semi-circular flow pattern at each end of the tank so that the the water pivots about the drain outlets. This flow pattern pattern generates centrifugal forces as the water circles the drain, concentrating the suspended solid wastes in the area around the drains. Water is introduced into into the tank at the head of the straight runs. The incoming water mixes with the water circling circling the racetrack, creating relatively uniform water quality throughout the tank. The water enters the tank through spray bars spanning the width of the straight run of the tank. All drain outlets are 4 inches in diameter, with the exception of those in the nursery tank, which are 2 inches in diameter. All drain outlets consist of bulkhead fittings which pass through the liner and feed into a common 4-inch 4-inch central drainage pipe. A PVC standpipe is is set in each drain outlet. The height of the standpipe sets the minimum water level in the tank. The top of the standpipe is fitted with a cylindrical screen extending to 6 inches above the maximum water level in the tank. The purpose of this screen is to exclude shrimp from the drain outlets. An outer sleeve is placed over the standpipe to allow the water flowing out of the drain outlet to be drawn from the bottom of the tank. The outer sleeve consists of a PVC pipe with a slightly larger diameter than that used for the standpipe. The pipe is scalloped or screened at the bottom to allow bottom water to to pass through it. Water passing through the drain outlets empties empties into a 4-inch diameter diameter central drainage pipe. The central drainage pipe discharges into a 4’ x 3’ x 4’ polyethylene sump located on the outside of the tank at one end of the raceway. The sump serves as a settling settling basin and pump well. A 2-hp centrifugal pool pump circulates water through the system. system. The intake for the pump pump is located near the bottom of the sump and is fitted with a check valve to prevent the pump from losing its prime when it is turned off. A 36-inch diameter high-rate downflow sand filter serves as both the solids filter and the biofilter for the system. The sand filters are loaded with 500 lbs of Number 20 silica silica sand. A 2.5-hp regenerative blower supplies air to the the system. Each culture tank is provided with forty 1” x 3” medium pore diffusers. Each diffuser supplies supplies approximately 0.3 standard cubic feet per minute (scfm) of air to the raceway, providing each culture tank with a total of 12.0 scfm of air. The airstones are distributed at 3-foot intervals along the sidewalls of the culture tanks. A beltdrive blower powered by a 9-hp diesel motor serves as an emergency backup. The backup blower has a pressure-actuated switch that starts the blower motor whenever the pressure in the air system drops to zero. System B:

System B represents a second generation in HBOI shrimp shrimp production system design. The design objectives for this system were to: 1) 2) 3) 4) 5) 6)

reduce the cost of the greenhouse structure reduce the construction costs for the culture tanks make the systems more energy efficient reduce the labor required to maintain the systems increase the carrying capacity of the systems, while keeping system costs down provide for consistent circulation of water throughout the system.

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The System B culture tanks are housed in in two 30’ x 96’ Quonset-style greenhouses . These greenhouses are similar to the System A greenhouses described above, but are less expensive. The System A greenhouses are rated to be able to withstand winds of up to 120 mph, while the System B greenhouses are only rated for winds of up to 80 mph. During the summer months a 95% shade cloth was placed placed on the outside outside of the the greenhouse. This provided significantly more shade than the System A shade cloth, which provided only 80% shading. The greenhouse ventilation system consists of two 42-inch x 3/4-hp exhaust fans fans and two 51-inch shuttered windows. A single thermostat controls both the windows windows and the exhaust fans. fans. An 8’ x 8’ sliding door is located at one end of the the greenhouse. This door allows large pieces of equipment or harvest ha rvest boxes to be easily moved into the greenhouse. The culture tanks in System B are similar to those in System A, except that they are partially excavated below ground level. Instead of having the floor of the culture at ground level and the tank depth determined by the height of the wooden frame, the floor of the System B culture tanks is excavated to a depth of 18-inches below grade. grade. A wooden frame surrounds surrounds the perimeter of the excavated area, adding an additional 12-inches to the depth of the raceway. The wooden frame is similar to the frame used to create the System A culture tanks. A berm with a 1:1 slope slope extends from the bottom of the wooden frame down to the floor of the tank. The overall tank depth, when filled with water is 24-inches, or 6-inches deeper than the System A tanks. The culture tank is lined with the same 30-mil high density polyethylene liner liner material as is used in System A. There are several advantages to this approach to raceway construction. construction. Because much of the volume of the raceway raceway is below ground level there should be less heat loss from from the raceways during the winter. The raceways can be made slightly deeper without appreciably increasing the cost of construction. A deeper tank will will sustain a higher biomass, and will also have more stable temperature and water quality characteristics. Each of the System B greenhouses is occupied by two culture tanks, each with its own water treatment system. The culture tanks lie side by side in the greenhouse, sharing a common central wall. The 3-foot wide walkway walkway between the tanks has been replaced with a 1-foot wide catwalk above the tanks. In this configuration configuration approximately 90% of the available area in the greenhouse is under cultivation, compared to about 80% in System A. Reducing the number of systems per greenhouse from four to two reduces the labor requirement by half,

Figure 2: System B Single-Phase Raceways with Axial Flow Pump -6-


without sacrificing any production. One greenhouse in System B (Figure 2) contains two single-phase shrimp production systems (J1 and J2). Each single-phase single-phase culture culture tank tank measures 14.5’ x 88’. Except for the fact fact that they are in-ground culture tanks, most of the details of their construction are essentially the same as in System A. The tracks are configured in “racetrack” configuration with a central baffle and corner baffles. The second greenhouse in System B (Figure 3) contains two three-phase shrimp production systems (J3 and J4). The culture tanks in the three-phase system are layed out like the single phase culture tanks, except that they are separated into three discrete sections by divider walls. The nursery sections measures 10’ x 14.5’ (11% of the culture area). The intermediate growout section measures 14.5’ x 27’ (31% of the culture area) and the final growout section measures 14.5’ x 51’ (58% of the culture area). Four-inch diameter bulkhead fittings positioned at the bottom of the walls dividing the three sections all shrimp to be transferred from one section to the next without being handled. One of the design objectives was to build a system that was more energy efficient than our sand filter-based systems. systems. Towards this end it was was decided to incorporate into the design a low-head filtration system that flowed by gravity through the solids filter and biofilter. An upflow bead filter is used in System B to filter out solid wastes as well as for b iofiltration. The upflow bead filter consists of cylindro-conical sump (4’ diameter x 4’ deep, 1,200-liter capacity ), filled with 16 ft3 of biofilter beads. The beads are polyethylene cylinders 7 mm long by 10 mm in diameter with radiating fins that that provide additional surface surface area. These beads are positively buoyant. The tank is plumbed plumbed so that the raw water from the culture tank enters the filter tank through a 4-inch bulkhead fitting cut into the conical portion of the tank. A second bulkhead fitting is cut into the sidewall about 12-inches below the culture tank water level and connects the solids solids filter to the biofilter tank. A 4-inch pipe with 5-mm slots cut into its upper surface is inserted into upper bulkhead fitting on the inside of the tank. This pipe collects filtered water from near the surface of the water and allows it to pass into

Figure 3: System B 3-Phase Production Production Systems, powered by a 3/4 hp centrifugal pump. -7-


the biofilter tank. The water must take a tortuous pass through the filter bed before it reaches the collecting pipe at the the top of the water column. In the process settleable settleable solids and larger suspended solids are trapped on the sticky surfaces surfaces of the beads. The solids are flushed from the system once a day by plugging the raw water inlet and the filtered water and removing a 2-inch standpipe from the drain outlet in the bottom of the cone. A 6-inch diameter outer standpipe keeps the beads from beads from draining out of the system. Windows covered by a 1/4” mesh screen are located near the bottom of the outer standpipe and allow water and solid wastes to pass through the outer standpipe and out of the tank when the central standpipe is removed. An aerated, submerged biofilter receives water after it flows out of the low-head bead filter. The biofilter uses the same beads as are used in the solids solids filter, but in this application the beads are tumbled by air bubbles introduced into the bottom of the filter bed through a grid of 10 medium pore airstones. The beads are contained within a 3.5’ x 5’ x 4’ cage made of 1” Schedule 40 PVC pipe and 1/4” square-mesh polyethylene mesh screen. The cage serves to contain the beads so that they do not get sucked into the pump or go out down the drain. The cage sits in a rectangular, polyethylene sump (4’ x 6’ x 4’), two inches above the bottom of the sump. The biofilter sump doubles as a pump reservoir for the main system pump. The amount of head required to return the water to the culture tanks is minimal since there are no filter components between the pump and the culture tanks, and the elevation head that must be overcome is less than 12-inches. Two different types of low-head pumps are being used in System B. A 1/4-hp axial flow pump (designed (designed and built by Harbor Branch personnel) performs the pumping duties in the the single-phase culture systems. systems. This pump utilizes a plastic propeller as an impeller. The pump column column is made of 4-inch PVC pipe. A tee halfway up the column directs the flow out of the pump and into the culture tank. The pump inserts into a bulkhead fitting that passes through the wall of the sump and the culture tank just below the tank water surface. There is essentially zero head pressure. These axial flow pumps are capable of moving large volumes of water with very little energy expenditure. The pump discharges 160 gpm of water in this application. Despite the high discharge volume of these axial flow pumps, the water is discharged with very little little pressure or velocity. As a result, the the return flow does not generate a great deal of circulation within the culture tank. Nor does the return flow flow provide any additional aeration or degassing. The axial flow pump could not be used in the three-phase systems because the return flow had to be piped to the opposite end of the greenhouse to the nursery and intermediate growout sections. The discharge out of these axial flow pumps drops off rapidly rapidly as head pressure increases. At only 18 inches of head the pump discharge is less than one-quarter of the discharge at zero feet of head. For this reason a centrifugal pump was used with the three-phase production systems. systems. The pump selected was a low-head, high-efficiency 3/4-hp centrifugal pump. This pump will push 150 gpm of water against 10 feet of head and is much more efficient than the high-head 2-hp pool pump used in System A. The System A pump will only pump 100 gpm at this head and requires requires more than twice the horsepower.

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Using a centrifugal pump in the three-phase systems permits the return flow to be introduced through spray bars, which span span the raceways. Each spray bar consists of a 2” diameter PVC pipe drilled with 1/4” diameter orifices. The momentum of the water passing at high velocity out of these orifices is transferred to the mass of water circulating in the tank. We observed that, although the discharge of the centrifugal pumps is slightly less than that of the axial flow pumps, the velocity of water flow rate in the three-phase culture tanks is much higher. This is because the water enters the culture tank at a high velocity and its momentum sets the entire mass of water in the tank moving. This is very important because it prevents the solid wastes from settling out and accumulating on the floor of the culture tank. Another important benefit derived from spray bars is that the water is aerated as it enters the tank and excess carbon dioxide is de-gassed as the the water passes out of the spray spray bar. Whichever pumping system is used, configuring the system so that there are no filter components between the pump and the culture tank guarantees that the flow rates through the system are constant over time. This is in sharp sharp contrast to System System A, where flow rates declined by 50-75% between sand filter backwashes. A single 2.5-h.p regenerative blower supplies the air supply for the four culture tanks in System B. This blower supplies approximately 100 scfm of air against a head pressure of 50inches of water. Each system is supplied with 25 scfm of air, which is delivered through submerged 3”x1” medium pore diffusers. diffusers. A total of 44 diffusers diffusers are positioned in the culture tanks at 4-ft intervals on either side of the central baffle. Ten additional airstones are set into an air manifold at the bottom of the biofilter cage and serve to aerate and tumble the biofilter media. A belt-drive blower powered by a 9-hp diesel engine provides emergency backup aeration. This blower is twice as large as it needs to be, delivering 200 scfm of air at 50-inches of water, but was sized to accommodate future expansions. A pressure switch switch turns the diesel engine on whenever it detects a loss of air pressure in the air system. Freshwater and seawater are both supplied by wells. Wellwater is a desirable water source source because it it virtually free from bacterial, viral, or parasitic pathogens. The wellwater does, however, have some undesirable chemical characteristics. Like a lot of wellwater, HBOI’s HBOI’s wellwater is high in hydrogen sulfide, carbon dioxide, and ammonia, and is low in oxygen. Before it can be used the water must pass through a series of pretreatments. The first step in the pretreatment process is to remove the supersaturated gases such as hydrogen sulfide and carbon dioxide by passing the water through a degassing tower. The degassing tower consists of an eight-foot tall polyethylene tank with a six-foot diameter. Inside the tank is a screened plate spanning the entire entire cross-sectional area of the tank. This plate supports plastic coiled packing media, which fills the volume of the tank above the plate. The water distributed distributed over the packing media at the top of the tank trickles down through the media in thin sheets and small small droplets. A 1/4-hp blower pumps air into the bottom of the column. The column is open at the top, allowing the air to escape. By increasing the area of the air-water interface, gas-exchange between the air and the water occurs at an accelerated rate. Supersaturated gases in the well water are transferred transferred from the

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water to the air, and gases that are under-saturated in the water, such as oxygen, are transferred from the air to the water. The water passing out of the degassing tower should be close to the saturation level for all of these gases. The next step in the treatment process is to remove the majority of the ammonia that is in the water. This is accomplished accomplished by passing the the water through a 12,000 liter biofilter tank. The biofilter tank contains numberous barrels of oyster shell. Each of the barrels is provided with an airlift, which functions to circulate water through the oyster shell biofilter media. Oyster shell is lifted from from the bottom of the bed by the airlift and deposited again at the top of bed. This circulation of the oyster bed through the airlift serves to slough off biofloc from the surface of the oyster shell. The flow rate through the biofilter tank is approximately 200 liters per hour. The total residence time in the biofilter is approximately approximately one hour. During this time the ammonia is reduced from nearly 1 ppm to about 0.05 ppm. The nitrite concentration of the water leaving the biofilter is typically less than 0.01 ppm. The treated water flows by gravity into one of two 20,000-liter water storage storage reservoirs. The water storage reservoirs are enclosed polyethylene chemical storage tanks that have been given a double coat of paint to keep them dark inside to to prevent algal growth. growth. A 2-hp centrifugal pool pump draws water from the reservoirs and pumps it through a sand filter and out to the culture systems. systems. The water delivery pump operates continuously so that water is available on a demand basis. A return to the reservoir tank is provided to protect the pump when there is little or no demand. The effluent from the shrimp production tanks discharges into a sump containing chlorine tablets to kill any escaping shrimp. A submersible trash pump with a mercury float switch pumps water from the the chlorination sump to a series series of retention ponds. The retention ponds for the Harbor Branch aquaculture park consist of three one-quarter acre ponds connected in series. All effluent from the facility discharge into one corner of the first pond in the series. Overflow pipes pass through the levees separating separating each of the three ponds. The first retention pond is the primary solids settling pond, and typically has the densest growths of algae and aquatic plants. The aquatic plants absorb nitrogenous wastes from the water. Evaporation and seepage account for virtually all of the losses of water from the retention ponds. The second and third ponds in the series provide extended residence time for the water to guarantee that the water has enough time to evaporate, or seep out of the ponds. Every few years it will be necessary to pump out the sludge that collects in the bottom of the ponds. One of the advantages associated with producing shrimp in near-freshwater systems systems is that this sludge can be used as fertilizer for certain vegetable or row crops. Retention ponds similar to the ones used by Harbor Branch are likely to be required of all feed-based aquaculture operations in the state of Florida.

Production Trials Methods Three sets of paired production trials were conducted during the project. In each of the paired trials a single-phase and a three-phase culture system were stocked at the same time with postlarvae from the same cohort to permit permit comparisons to be made. One of the three- 10 -


phase culture tanks, H5-NW, was stocked on 4/12/99 in a non-paired trial. No single-phase culture tanks were available for stocking at that time. time. System H5-NE (single-phase) and system H5-NW (three-phase) were paired in the first trial trial (System A Winter Trial). These tanks were stocked November 27, 1998 and harvested on May 25, 1999, after 180 days. Systems H5-SE (single-phase) and H5-SW (three-phase) were paired in the second trial (System A Spring Trial). These tanks were stocked on February 23, 1999 and harvested harvested on August 21, 1999, after 179 days. A third production trial paired single-phase and three phase culture tanks in in System B (System B Spring Spring Trial). This study was to have been initiated at the same time as the System A Spring Trial, but was delayed by two months by unforeseen problems in obtaining building permits to construct the System B greenhouses. Post-larvae were stocked into System B during the last week of April. April. The System B trials were terminated on September 14, after only 135-140 days, in anticipation of possible landfall of Hurricane Floyd. These tanks were harvested early to prevent accidental escape of the shrimp in the event of flooding. In each of the trials stocking densities were calculated to achieve a harvest density of 150 shrimp/m2, with overstock to compensate for the expected 35% mortality from PL to harvest. The target stocking density in the single-phase systems was 230 shrimp/m2. The target stocking density in the in the nursery section of the three-phase systems was 1,250 shrimp/m2. Table 1 summarizes both stocking stocking and harvest data for each of the three trials. trials. The System B culture systems were stocked at densities that were approximately 30% less than the targeted initial densities. This was because of heavy pre-stocking mortality mortality among postlarval shrimp held in the hatchery from the originally scheduled stocking date in late February until the actual stocking stocking date in April. We wanted to give the postlarvae a head start in the hatchery to make up for the delayed startup date. Cannibalism in the hatchery tanks resulted in heavy losses, so not enough of the large postlarvae were available to permit stocking at the targeted densities. All systems were stocked with Specific Pathogen Free (SPF) postlarvae produced for the study at Harbor Branch. SPF postlarvae are guaranteed to be free free from the known viral diseases, including Baculovirus, Infectious Hypodermal Hematopoetic Necrosis Virus (IHHN), Taura Syndrome Virus (TSV), and WSSV. The postlarvae postlarvae were acclimated to near-freshwater conditions in the hatchery prior to stocking. Acclimation to near-freshwater near-freshwater conditions is possible only after the shrimp have sufficient gill development to permit osmoregulation, usually after they reach PL12. All crops were reared in near-freshwater conditions. Salinities in the growout growout tanks averaged 0.7 pppt, chloride concentrations averaged 400 mg Cl /L , total hardness averaged 400 mg/L as CaCO3, and alkalinity averaged 150 mg/L as CaCO3. The feeds used in this study were specially formulated with elevated levels of calcium, phosphorus, potassium, Vitamin Vitamin C, and other vitamins and minerals. minerals. The elevated levels of these ingredients are necessary for normal growth and development of shrimp in high density freshwater recirculating systems. systems. A variety of feeds are required to raise raise the shrimp from from postlarvae to harvest size. size. During the nursery phase we fed postlarval postlarval and juvenile diets manufactured at HBOI by Rolland Laramore. For the first five days the shrimp were fed

- 11 -


J400, a 50% protein 400µm postlarval postlarval diet. The shrimp were fed J1000, a 50% protein juvenile diet (particle size 850-1200 µm) until they reached a size of 0.2 g/shrimp. When When they reached that that size they they were weaned onto a 1.6 mm pellet (J1600). J1600 has a protein content of 45%. The shrimp remained remained on J1600 until they reached a size size of about 0.8 grams/shrimp, when when they were switched to a 3/32" 45% protein juvenile pellet. The shrimp remained on this diet until until the end of the the nursery phase. In the intermediate and final phases of the growout the shrimp were fed a 3/32” grower pellet. Until April we were feeding a diet manufactured by Burris Mill and Feed that contained 38% protein . This diet was not particularly attractive to the shrimp, and we were dissatisfied with the growth of the shrimp on this diet. In April we switched to a 35% protein Rangen diet formulated for intensive culture. This diet was more palatable to the shrimp and produced better growth rates. The shrimp were fed four times per day by hand at 8:00 A.M., 11:00 A.M., 2:00 P.M., and 5:00 P.M. The shrimp shrimp were fed according to their their appetite. Feeders were instructed to monitor feed consumption and adjust feeding rates upward by 10% if all of the feed was consumed in a 3-hour period, and downwards by 10% if significant quantities of feed remained from the previous feeding. Throughout the project records were kept on feed consumption, temperature, salinity, dissolved oxygen, total ammonia (TAN), unionized ammonia, nitrites, alkalinity, and hardness. Shrimp from each culture system were weighed on a biweekly basis to monitor growth. The daily maintenance routine included twice daily jetting and backwashing of sand filters and upflow bead filters. Dead shrimp were removed and counted whenever they were observed.

Results The production results from all trials are summarized in Table 1. System A Winter Trial

Survival in the single-phase system (H5-NE) stocked on 11/27/98 was a surprising 88%, with nearly nearly 13,800 shrimp surviving out of 15,750 shrimp stocked. The harvest density was 201 shrimp/m2. A total of 142 kg of shrimp were harvested. The biomass loading in the system was 2.25 kg/m2, which is very close to what we had hoped to produce from the system. However, the average size of the shrimp shrimp at harvest was only 10.3 grams after 180 days (Figure 4). With such a high survival, the the carrying capacity for the system system was reached before the shrimp shrimp reached an acceptable harvest size. The average growth rate for this crop was a very disappointing 0.4 grams/week. System breakdowns may also have contributed to the small size of the shrimp in the single phase tank (H5-NE). Beginning in March we encountered problems with the H5-NE sand filter. One of the laterals in the bottom bottom of the sand filter filter broke. The broken lateral caused all of the sand to be lost from the sand filter and a complete loss of biofiltration. Feed rates were sharply reduced until new sand became biologically active. The following month two valves on the sand filter broke off off on different occasions. The resulting downtime forced - 12 -


additional reductions in feed rates. Throughout April and May ammonia levels were often high (Figures 6) and oxygen levels (Figure 7) were routinely less than 5.0 mg/l. The 47% survival rate of shrimp in the three-phase system, H5-NW, was almost half that of the single-phase system. The relatively low survival survival resulted from high rates of cannibalism during the nursery and intermediate phases, and from Vibrio infection. Cold weather in December and February was followed by relatively warm period (Figure 5). These temperature fluctuations may have stressed the shrimp, precipitating the outbreak of Vibrio. With less crowding and generally good water quality conditions, the shrimp in H5-NW grew much better than those in H5-NE, reaching the size of 15.1 grams in 180 days. This corresponds to a growth rate of 0.58 grams/week. System H5-NW did not experience the same water quality problems problems late in the study that were experienced in H5-NE. Ammonia (Figure 6) levels remained low throughout the trial, and dissolved oxygen levels (Figure 7) remained high. Nevertheless, the growth rates were slower than expected. Previous experience led us to expect the shrimp would reach a harvest size of 18 grams in 180 days. A major factor contributing to the slower than expected growth rates in both systems was the cold weather in December and February. Neither the tanks nor the greenhouses were heated, so passive solar heating of the greenhouses was the only means of maintaining temperatures. In the first month of the trial a shade cloth covered the outside of the greenhouse, cutting down on the warming effect of solar radiation during the day, but doing little to prevent heat loss at night. Cold weather in December and in February (Figure 5) resulted resulted in water temperatures of 22ºC or less for extended periods periods of time. Temperatures rarely rose above 26ºC for the first 60 days of the culture period. When the water temperature is less than 22º C, the shrimp do not grow. Growth rates are significantly reduced when temperatures temperatures drop below 26ºC. System A Spring Trial:

As was the case in the Fall production trials, the survival in the single-phase production system, H5-SE (76%) was significantly higher than the survivals achieved in either of the two three-phase systems systems stocked stocked at the same time (Table 1). The survival in the two three phase studies stocked in February were 61% (H5-SW) and 40% (H5-NW). (H5-NW). The survival in H5-NW was estimated at 65% until July 7, when the air supply to the raceway was interrupted due the failure of a pipe connection. Over two thousand shrimp shrimp (20% of the population) died as a result of the low low dissolved oxygen condition. Cannibalism was frequently observed in the nursery and intermediate sections of the three-phase culture tanks. After 179 days the shrimp in the single-phase culture tank, H5-SE averaged 14.6 g and a total of 194.2 kg of shrimp were harvested. Growth rates averaged 0.57 g/shrimp/week. Shrimp harvested from the three-phase culture tanks averaged 15.3 g/shrimp (H5-SW) and 13.6 g/shrimp (H5-NW) after 180 days. The growth rates in H5-SW averaged 0.6 g/shrimp/week, while the shrimp in H5-NW grew at an average rate of 0.53 g/shrimp/week.

- 13 -

Table 1: Summary of production results

Culture System

Date Stocked

Number of Shrimp Stocked

Initial Average Wt. (g)

Culture Period (Days)

Number of Final Final Final Feed Percent Shrimp Average Biomass Density Conversion Survival Surviving Wt. (g) (kg) (Shrimp/m2) Ratio

Single-Phase

H5-NE

11/27/98

15,750

.005

180

13,798

88%

10.3

142

201

1.76

H5-SE

2/23/99

17,400

.01

179

13,300

76 %

14.6

194.2

169

1.83

J1

4/28/99

19,000

.003

135

12,807

67%

9.0

115.3

109

1.36

J2

4/26/99

20,000

.03

137 1

18,074

90%

9.5

171.7

153

1.41

Three Phase

H5-NW

11/27/98

10,000

.005

180

4,680

47%

15.1

70.7

108

1.91

H5-SW

2/23/99

11,362

.005

179

6,938

61%

15.3

106.2

142

1.61

H5-NW

2/5/99

10,450

.008

180

4,153

40%

13.7

56.9

95

2.05

H5-NW

4/12/99

9,900

.02

154

6,224

63%

14.6

90.9

144

1.67

J3

4/25/99

10,000

.02

138

8,184

82%

15.0

122.8

121

1.70

1)

Nearly all of the shrimp initially stocked on 4/26/99 died on 6/1/99 due to high nitrite levels resulting from stocking the PLs before the biofilter biofilter was conditioned. The tank was restocked restocked on 6/14/99 with 20,000 shrimp shrimp of the same same age as the survivors from the initial stocking. The re-stocked shrimp were approximately the same size (0.90 g vs. 0.99 g) as the surviving shrimp from the initial stocking. Because the restocked shrimp were the same age and size as the surviving surviving shrimp from the initial stocking, the culture period for J2 given in the table is counted from the initial stocking date (4/26/99).


Growth rates in all three of the tanks stocked in February were extremely slow during the first ninety days after stocking (Figure 8), averaging less less than 0.3 g/shrimp/week. The shrimp in all three tanks measured 4 grams or less after 90 day. For the second 90 days of the culture period, growth rates averaged between 0.80 and 0.85 g/shrimp/week in each of the three tanks. Low temperatures may be partly responsible for the slow growth observed in the spring production trials. Weekly temperature temperature averages were less than 28ºC for more more than half of the culture period (Figure (Figure 9). Growth rates begin to to be affected when temperatures temperatures drop below 28ºC. No major ammonia or nitrite problems were observed in any of the three culture tanks. Total ammonia nitrogen levels were maintained, for the most part, at a concentration less than or equal to 0.4 mg TAN/L (Figure 10). TAN concentrations were elevated in H5-NW for a period of three weeks in June, ranging between 0.8 and 1.2 mg TAN/L. Concentrations of toxic unionized ammonia ranged between 0.05 - 0.08 mg NH3-N/L during this period. These concentrations of unionized ammonia are well below the the lethal limit limit for juvenile shrimp, but could have had an impact on the growth growth rates of the shrimp. shrimp. Nitrite levels were generally less than 0.4 mg NO2-N/L in all three culture tanks. Nitrite levels levels were slightly elevated (0.8 – 1.2 mg NO2-N/L) in H5-SE during the last 2 weeks before the shrimp were harvested. However, these levels were more than an order of magnitude less than the lethal limit for adolescent shrimp. Dissolved oxygen levels dropped to about 1.5 ppm in H5-NW on July 7 when the air supply to the tank was interrupted for an undetermined period of time because of the failure of a pipe connection. This incident resulted in the loss of 2,000 shrimp. Aside from this incident, dissolved oxygen levels were maintained above 5 mg/L throughout the culture period in both of the three-phase tanks (Figure 11) . The dissolved oxygen concentrations in the single-phase tank, H5-SE, were maintained above 5 mg/L except for the final 7 weeks, when dissolved oxygen concentrations averaged between 4 and 5 mg/L (Figure 11). This may explain why the growth rate of the shrimp in H5-SE slowed during the final three weeks of the culture period (Figure 8). System B Summer Trials

The System B trials were terminated 6 weeks early on September 13 and 14 because of the threat posed by Hurricane Floyd. As a result, result, the survival survival and final harvest size data presented for tanks J1, J2, and J3 in Table 1 are not directly comparable to the System A data because the culture period was much much shorter. At the time these tanks were harvested, however, trends were already emerging. Survival in J1 after 135 days was 67%, slightly lower than had been observed in other single-phase culture systems. systems. The large majority of the mortality was observed observed during the fourth and fifth week of the study, when nitrite levels peaked at 10 mg NO2-N/L. This was due to the fact that, because of the construction delays, we stocked the system without preconditioning the biofilters. biofilters. Nitrite levels were even higher J2, which was stocked with - 15 -


larger postlarvae and was receiving more feed. J2 experienced massive massive mortality mortality four weeks after it was stocked. We restocked J2 on June 17 with juvenile shrimp of the same age as the shrimp that had been initially stocked. Survival of these animals was 90% to the end of the study. One of the three-phase systems, J4, also experienced nitrite levels above 20 mg NO2-N/L during the fourth week of the study and suffered suffered nearly 100% mortality. mortality. There were no animals available to restock this tank, so we continued the study with only one three-phase tank in System B. The survival in the remaining three-phase tank, tank, J3, was 82% after 138 days (Table 1). This survival was achieved despite the fact that these shrimp experienced nitrite levels as high as 6.0 mg NO2-N/L during the biofilter biofilter conditioning process. In contrast to what was was observed in the three-phase tanks in System A, very little cannibalism was observed in J3. The reduction in cannibalism may be related to two system modifications that reduced the encounter frequency between the the shrimp. The tank depth in the nursery section of J3 is nearly twice as deep as in the System A nursery sections. In addition, current velocities were higher in the nursery and intermediate intermediate sections of J3. Higher current velocities cause the shrimp to move off the bottom and swim in the the water column. This, combined with the increased tank depth, reduced the encounter frequency between the shrimp. The shrimp in the single-phase tanks, J1 and J2, averaged 9.0 and 9.5 g/shrimp, respectively, after 136 days (Table 1, Figure 12). These average weights are comparable to the weights observed for shrimp in the System A studies after the same time period (Figures 4 and 8). Growth rates were particularily slow during the first 90 days of the culture period. This was most likely due to the fact that throughout the second month the shrimp were on a restricted diet because of the high nitrite nitrite concentrations in the tanks. In addition, these greenhouses were covered with a 95% shadecloth, which virtually eliminated algal growth. Without adequate feed input and without significant natural productivity in the tanks, the shrimp were not adequately nourished during the first half of the two and half months of the study. In contrast, the shrimp in the three-phase tank, J3, J3, grew very rapidly and reached an average weight of 15.0 g/shrimp after only 138 days. The average growth rate rate of these shrimp over the final final 72 days of the the growout period was 1.0 g/shrimp/week. g/shrimp/week. Projecting this growth rate out over the next 42 days (to the expected harvest at 180 days), the predicted harvest weight of these shrimp would be 21 g/shrimp. Without carefully controlled experiments, it is difficult to say with certainty why the shrimp in J3 grew at a much faster faster growth rate than did all of the other tanks in this this study. It is possible that the lower stocking density (about 30% less than the the stocking density of the the System A three-phase tanks) allowed allowed for faster faster growth rates. rates. However, with the the higher 2 survival rate, the final harvest density (122 shrimp/m shrimp/m ) was intermediate in the range of final harvest densities (Table 1) for the three-phase tanks in System A (95-144 shrimp/m2). Yet the growth rates in J3 far outpaced the growth rates in any of the System A tanks. System differences such as tank depth and filtration systems might be partially responsible for some of the observed differences in growth rates. While the differences differences in the tank depth and water filtration systems could explain differences between the growth rates

- 16 -


between J3 and the System A tanks, they do not explain the pronounced difference in growth rates between J3 and the single-phase System B tanks (Figure 12). One important difference existed between the greenhouse enclosing J3 and the greenhouse enclosing J1 and J2. The shadecloth covering the J3 greenhouse was removed in the middle of June. After the loss of the shrimp in J4, system J4 was put into algae production for the clam hatchery. This required removal of the shadecloth. Following removal of the shadecloth, a dense algal bloom developed in J3, J3, which was maintained maintained until the end of the study. It is possible that the phytoplankton provided a supplemental food supply for the shrimp. Temperatures in the System B greenhouses (Figure 13) were much warmer than the temperatures that were maintained in the System B winter and spring trials (Figures 5 and 9). Temperatures were maintained above 30ºC in J3 from July until the end of the study. The temperatures in J1 and J2 were slightly warmer than in J3 through the first 60 days. During this period average weekly temperatures in J3 were less than 28ºC. Average weekly temperatures in J1 and J2 remained above 28ºC from the the end of the first month to the end of the study (Figure 13). Ammonia was not a problem during the System B trials, despite the fact that the systems were started up without preconditioning of the biofilters. Ammonia concentrations spiked, as expected, about three weeks after the systems were started up (Figure 14). The maxiumum total ammonia nitrogen (TAN) concentrations observed in any of the tanks was 1.2 mg TAN/L. TAN concentrations declined to low levels following the initial peak, and remained low throughout the rest of the studies (Figure 14). TAN levels in J1 never peaked at all. High nitrite concentrations presented the major water quality problem in the System B trials, and resulted in the loss of of two crops of shrimp. shrimp. Establishment of the Nitrobacter population on the biofilter media lagged far behind the establishment of the Nitrosomonas population. For much of the first 60 days, the majority of the ammonia that was converted into nitrite by the Nitrosomonas bacteria, remained in in the system. system. During this period nitrite levels were controlled primarily by water exchange. Initially we were rinsing rinsing and tumbling the beads in the solids filter twice a day to remove remove the solid wastes. In addition, the beads in the biofilter tank were tumbled continuously by aeration. It appears that the vigorous tumbling the beads were subjected to during this procedure interfered with establishment of the Nitrobacter population. Near the end of June we reduced rinses of the solids solids filter to to once every third day. This procedural change was quickly followed by a reduction in the nitrite levels to less than 0.5 mg NO2-N/L in all three tanks. The solids filter thereafter functioned as a biological solids filter, and was the principal site for nitrification of nitrite to nitrate by Nitrobacter . Dissolved oxygen concentrations were maintained above 6.0 mg/L for the first 90 days in all of the System B tanks (Figure (Figure 15). Dissolved oxygen concentrations were maintained maintained above 5.0 mg/L throughout the study in J1. Dissolved oxygen (DO) concentrations dropped below 5.0 mg/L in both J2 and J3 during the final month of the study. Morning DO levels occasionally dropped to as low as 3.5 mg/L in system J3, but typically would rise to about 7.0 mg/L in the afternoon. This diurnal swing in DO levels was related to the presence presence of an

- 17 -


algal bloom in this system. system. Dissolved oxygen concentrations never dropped to dangerous levels in any of the System B tanks. System A Summer Trial

The three-phase culture system H5-NW was stocked for the third time during the year on April 12. This crop was not paired with a single-phase System A crop because no single phase culture systems were available for stocking at that time. To a certain extent, the crop serves as a System A counterpart or control to the summer production trials in System B. This study was also terminated early on September 14 due to the threat of landfall by hurricane Floyd. Production data for this crop are summarized in Table 1. Survival was 63%, with with a harvest 2 density of 144 shrimp/m . Cannibalism during the nursery nursery phase and shrimp jumping out of the tank account for most of the observed mortality. mortality. Based on observations of mortality patterns in other crops, very little additional mortality would be expected if the crop had been carried on for three three more weeks. Based on the high survival survival observed during the last last three weeks in other tanks, it is likely the survival for a 180-day growout would have been above 60%. The average weight after 159 days was 15.1 grams. While growth rates averaged only 0.67 grams per week for the entire culture period, over the last 72 days of the culture period growth rates averaged 1.0 gram per week (Figure 16). If growth rates had continued at this pace for another 3 weeks, the shrimp would have averaged approximately 18 grams after 180 days. While this is slightly slightly smaller smaller than the projected harvest size of the System B three-phase crop in J3, it is much better than the growth rates that were observed in any of the winter or spring trials in System A. During the first 80 days, weekly average temperatures (Figure 17) were maintained between 26ºC and 28ºC. Weekly average temperatures were maintained between 28ºC and 29ºC during the last 80 days of the study. Warm temperatures during the latter half of the growout period coincide with the 1.0 1 .0 gram/week growth rates. For the majority of the culture period, TAN concentrations were maintained below 0.4 mg TAN/L (Figure 18). For a two-week period during the second month month of the culture culture period TAN concentrations averaged 0.8 mg TAN/L. TAN/L. During this time frame the pH averaged between 8.0 and 8.3, and unionized ammonia levels rose as high as 0.08 mg NH3-N/L. While these concentrations are well below the lethal level, they are more than double the desired upper limit of 0.03 mg NH3-N/L. Had the unionized ammonia levels remained at this level for for long, growth rates would likely likely have been affected. affected. Nitrite levels were generally less than 0.6 mg/L throughout the study. For a short period in early June, nitrite levels rose to 1.4 mg NO2-N/L. This level is slightly above the the desireable upper limit limit for nitrite, but well below the lower lethal limit for juvenile shrimp. Dissolved oxygen concentrations were maintained above 5.0 mg/L throughout the study (Figure 19). During the first first half of the study dissolved oxygen concentrations were were generally maintained above 6.0 mg/L. - 18 -


Discussion One of the objectives for this study was to compare the productivity of a single-phase production system with that in a three-phase production system. system. As part of the analysis, analysis, a comparison was made of the potential annual production of shrimp in a single-phase and a three-phase production system system (Table 2). 2). This comparison was based on average stocking densities, survival rates, and harvest weights achieved during the course of this project. This analysis indicated that, despite lower average survival rates, the total annual production of a three-phase production system system should be 60% higher per unit of production area than the annual production of a single-phase system. system. The average weight of shrimp harvested from three-phase systems during this study was actually larger than for single-phase systems. Even if the harvest weights of shrimp from three-phase and single-phase systems were equal, the annual productivity of the three-phase system would be 40% higher than that of a single phase system. If survival and final harvest weight of the two systems were equal, the threethree phase system system would out-produce out-produce a single-phase system system by 80%. These results results strongly favor the use of three-phase production systems over the traditional single-phase approach. The primary objective for this project was to quantify the key production parameters and associated costs for growing shrimp in greenhouse-enclosed freshwater recirculating systems. An economic analysis based on the data that were collected during the course of this project was performed for a hypothetical 12-greenhouse enterprise enterprise (see Appendix A). A). Because the production potential for the three-phase system was so much greater than that of a single phase system, only the three-phase system was modeled.

Table 2: Comparison of the annual production potential a single-phase and three-phase system. Culture System

Parameter

Single-Phase

2

Number of shrimp stocked/m of culture area/crop 1 Average survival survival rate to 180 days 2 Average number of shrimp harvested/m harvested/m of culture area/crop 2

Average weight of individual shrimp harvested (g) Average total weight harvested/m2 of culture area/crop (kg) Potential crops/year 2

Potential total harvest harvest weight/m weight/m of culture area/ year (kg)

Three-Phase

200 77%

120 60%

154

72

14.1

15.9

2.17

1.14

2

6

4.34

6.87

1

Predicted 180-day survival rates were used rather actual survival rates for the tanks that were harvested early due to hurricane Floyd. The 180-day survival rate was predicted predicted by projecting a straight-line straight-line survival curve from the initial stocking date to the actual harvest date out to the date when the culture period would have reached 180 days. This probably underestimates 180-day survival rates because most of the mortality occurs during the first 90 days after stocking. The survival rate of the spring trial of H5-NW, which lost 2,000 shrimp due to a disconnected airline, was adjusted upward by assuming that 80% of the shrimp lost in that event would have otherwise survived.

2

Predicted 180-day harvest weights were used rather than actual harvest weights for the tanks that were harvested early due to hurricane hurricane Floyd. The 180-day harvest weights were predicted by assuming assuming that during during the time period between the actual harvest date and 180 days the shrimp would continue to grow at the same rate as was observed for the 10-week period prior to the actual harvest.

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Based on the costs and production parameters estimated in this study, the economic model shows that culturing shrimp in systems like those demonstrated in this study would not be profitable. However, the sensitivity analysis shows that if the survival can be improved to 70%, and the growth rate improved so that 18 gram shrimp can be grown in 150 days, a 12greenhouse enterprise could generate an internal rate of return of nearly 50% (assuming the shrimp can be sold as a fresh, heads-on product for $5.24/lb). How likely is this scenario? There is good reason to believe that growth rates can be improved. As was discussed discussed earlier, the slow growth rates that were observed in many of our production trials were, at least partly related to cool temperatures in the culture tanks during significant portions of the culture period. However, the production tanks were not heated and temperatures were not optimal for growth throughout throughout much of the winter and spring trial culture periods. periods. With optimal culture temperatures there is little doubt the shrimp could be grown to a minimum harvest size of 18 g/shrimp in 180 days. This was demonstrated in the summer trials in tanks J3 and H5-NW (Table 1). We did not, however, demonstrate that shrimp can be grown in tank culture systems to 18 grams in 150 days. It is well known that in ponds, L. vannamei grows best in ponds with high levels of natural productivity (Scura, 1995). Phytoplankton and organic detritus are both important components of the shrimp’s diet (Moss, 1992). L. vannamei has a very inefficient digestive system consisting consisting of short, straight gut. Evidence is accumulating that L.vannamei does not utilize prepared diets efficiently, especially if their feces are rapidly filtered from the system. However, if their feces are allowed to remain in the system, heterotrophic bacteria will colonize the fecal material material and convert feed protein into bacterial protein. Shrimp consume the decaying fecal material and the associated bacteria. The shrimp derive significant nutritional benefits from the bacterial proteins and partially digested feed proteins during this second pass. The importance of the detrital food chain to shrimp growth was not fully appreciated until this study was nearly over. The culture tanks were shaded to control algae growth, and solid wastes were quickly removed from the system in the interest of maintaining optimal conditions for biofiltration. As a result, the shrimp were almost completely dependent upon the nutrition they could absorb from the prepared feeds in a single pass through the gut. Recent unpublished work at Harbor Branch has demonstrated that the growth rates of shrimp grown in tanks managed for optimization of the detrital food chain have been up to 50% faster than the growth rates observed in the systems modeled in this report. Similarly, Moss (1999) reported growth rates of L.vannamei cultured in a high density tank-based culture system at the Oceanic Institute (OI) in Hawaii that were double the growth rates observed in the HBOI system. The primary difference between the OI system and the HBOI system was that the OI system was a “greenwater” system, while the HBOI system was a “clearwater” system. The presence of algae and organic detritus detritus in the tanks was credited by Moss for for the rapid growth rates that were observed in the OI system. These results suggest that the mediocre growth rates observed in this study were not strictly a function of the tank environment, or the high densities that were used. Rather, the slow slow

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growth may be related to the scarcity scarcity of detritus in in the system. Better growth rates might be realized with alternative management strategies. Sand filters are probably too efficient at removing algae and fecal wastes. The filtration system used in System B allows some some of the finer particulates remain in the system. system. These are broken broken down by bacteria and are are potentially reprocessed by the shrimp. Removing the shade cloth and allowing phytoplankton blooms to develop appears to allow for much faster growth during the first 90 days of the culture period. Work is needed to to learn how to manage systems systems with dense phytoplankton blooms so that they are stable. Nevertheless, it is clear that that it is possible to to grow the shrimp to a size of 18 grams in 150 days. The possibility exists that growth rates are reduced in a freshwater culture environment. Based on our results in this study, we have no basis for evaluating the possibility that the stress of the freshwater culture environment somehow inhibits shrimp growth, because we do not have saltwater controls to compare our results to. Reports from pond culture systems shows that excellent growth is possible at salinities down to 2 ppt. At 0.5 ppt, however, the shrimp are closer to their physiological physiological limits. It is certainly plausible that the increased energy expended on osmoregulation comes at the expense of growth. This is an important question for future investigation. There is good reason to believe that survival rates can be improved in three-phase systems. A major problem encountered in our three-phase culture tanks was the high rate of cannibalism in the nursery and intermediate sections of the three-phase raceways. This is, at least in part, a density-related phenomenon. Post-larvae are very cannibalistic in high density environments, especially when underfed. The high density increases the encounter rate between individuals, individuals, increasing the opportunities for aggression to occur. Design modifications such as deeper tanks and greater water movement should help reduce cannibalism by reducing the encounter rate between postlarvae. Increasing the frequency of feedings is another management strategy that may help reduce cannibalism. Shrimp are more likely to cannibalize their their peers when they are hungry. This problem can be overcome by feeding aggressively and more frequently to make sure the shrimp are never hungry. There is growing evidence that artificial substrates can help improve both survival and growth rates of shrimp shrimp in both ponds and raceways. Artificial substrates substrates provide additional surface area, which lets the shrimp spread out more. In addition, periphyton growing on artificial substrates provides a nutritious supplement to the artificial feeds. The average survival rates achieved in our single-phase single-phase culture tanks was 77% . Survival of shrimp in our unshaded System B three-phase system system was 82%. There is good reason to believe that improved system design, use of artificial substrates, promotion of algal and detrital food chains and increased increased feeding frequencies can improve survival survival rates to 70%. If both growth and survival survival can be improved, improved, and shrimp can be sold for for at least $5.00 per pound, greenhouse culture culture of shrimp in freshwater recirculating systems systems could be a profitable business.

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Recommendations While it is clear improvements are needed, we still are confident this is a technology for the future. The following are some recommendations for for improving the technology, based on the experiences of this year: 1. Heating systems systems are required to obtain consistent growth year-round. year-round. necessary to determine the most economical system for heating a raceway.

Studies are

2. Deeper raceways with higher velocity should help improve survival, and obtain more uniform growth rates. 3. Artificial substrates should be investigated to determine if they help reduce cannibalism and if epiphytic growth can provide an additional source of natural foods. 4. Research should be conducted to determine how to create stable production systems with rich algal and detritus-based food chains. 5. More research is needed to develop nutritionally complete diets, especially for young juveniles. 6. Work on improving low-head biofiltration and solids removal systems. 7. More research is needed to determine whether or not near-freshwater systems inhibit growth due to chronic osmotic stress. stress. Additional research is need to determine determine if mineral supplements to the water are needed or beneficial. 8. Market research is needed to determine the nature of direct markets for freshwater shrimp. 9. Work is needed to determine if other types of biofiltration systems are better suited to shrimp culture (for example, systems utilizing heterotrophic bacteria, in addition to autotrophic bacteria, to control ammonia and nitrite concentrations.).

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Literature Cited Davis, D.A. and C.R. Arnold. 1998. The design, management, and production of a recirculating raceway system for the production of marine shrimp. Aquaculture Engineering 17 : 193-211. Moss, S.M. (1999). Biosecure Shrimp Production: Emerging Technologies for a Maturing Industry. Global Aquaculture Advocate 2(4/5): 50-52. Moss, S.M., G.D. Pruder, K.M. Leber, and J.A. Wyban. 1992. The relative enhancement of Penaeus vannamei growth by selected fractions of shrimp pond water. Aquaculture 101: 229-239. Scura, E.D.. 1995. Dry season production problems on shrimp farms in Central America and the Caribbean Basin. Basin. In, C.L. Browdy and J.S. Hopkins, editors. Swimming Through Troubled Waters, Proceedings of the Special Session on Shrimp Farming, Aquaculture ’95. World Aquaculture Society, Baton Rouge, Louisiana. pp. 200-213.

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Figures

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System A Winter Production Trial Growth Curve 20.0 18.0 H5-NE (Single-Phase)

16.0

H5-NW (Three-Phase)

14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0

15

30

45

60

75

90

105

120

135

150

165

180

Days After Stocking

Figure 4: System A Winter Production Trial Growth Curve.

System A Winter Production Trial Temperature 34 H5-NE (Single-Phase)

32

H5-NW (Three-Phase) 30 28 26 24 22 20 18 0

15

30

45

60

75

90

105

120

Days After Stocking

Figure 5: System A Winter Production Trial Temperature Data

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135

150

165

180


System A Winter Production Trial Total Ammonia Nitrogen 2.0 1.8

H5-NE (Single-Phase)

1.6

H5-NW (Three-Phase)

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

30

60

90

120

150

180

Days After Stocking

Figure 6: System A Winter Production Trial Total Ammonia Nitrogen Concentrations

System A Winter Production Trial Dissolved Oxygen 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 H5-NE (Single-Phase)

2.0

H5-NW (Three-Phase)

1.0 0.0 0

15

30

45

60

75

90

105

120

135

150

165

Days After Stocking

Figure 7: System A Winter Production Trial Dissolved Oxygen Concentrations

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180


System A Spring Production Trial Growth Curve 20.0 18.0 H5-SE (Single Phase)

16.0

H5-SW (Three-Phase)

14.0 12.0

H5-NW (Three-Phase)

10.0 8.0 6.0 4.0 2.0 0.0 0

15

30

45

60

75

90

105

120

135

150

165

180

Days After Stocking

Figure 8: System A Spring Production Trial Growth Curves.

System A Spring Production Trial Temperature 34 32 30 28 26 24

H5-SE (Single-Phase)

22

H5-SW (Three-Phase)

20

H5-NW (Three-Phase)

18 0

15

30

45

60

75

90

105

120

Days After Stocking

Figure 9: System A Spring Production Trial Temperature Data.

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135

150

165

180


System A Spring Production Trial Total Ammonia Nitrogen 2.0 1.8

H5-SE (Single-Phase)

1.6

H5-SW (Three-Phase)

1.4

H5-NW (Three-Phase)

1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

15

30

45

60

75

90

105

120

135

150

165

180

Days After Stocking

Figure 10: System A Spring Production Trial Total Ammonia Nitrogen Concentrations.

System A Spring Production Trial Dissolved Oxygen 10.0 9.0 8.0 7.0 6.0 5.0 4.0 H5-SE (Single-Phase

3.0

H5-SW (Three-Phase)

2.0

H5-NW (Three-Phase)

1.0 0.0 0

15

30

45

60

75

90

105

120

135

150

165

180

Days After Stocking

Figure 11: System A Spring Production Trial Dissolved Oxygen Concentrations.

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System B Summer Production Trial Growth Curve 18.0 J1 (Single-Phase)

16.0

J2 (Single-Phase)

14.0

J3 (Three-Phase)

12.0 10.0 8.0 6.0 4.0 2.0 0.0 0

15

30

45

60

75

90

105

120

135

Days After Stocking

Figure 12: System B Summer Production Trial Growth Curves. System B Summer Production Trial Temperature 34 32 30 28 26 24 J1 (Single Phase) 22

J2 (Single Phase)

20

J3 (Three-Phase)

18 0

15

30

45

60

75

90

105

Week

Figure 13: System B Summer Production Trial Temperature Data. - 29 -

120

135


System B Summer Production Trial Total Ammonia Nitrogen 2.0 1.8

J1 (Single-Phase)

1.6

J2 (Single-Phase)

1.4

J3 (Three-Phase)

1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

15

30

45

60

75

90

105

120

135

Days After Stocking

Figure 14: System B Summer Production Trial Ammonia Concentrations. System B Summer Production Trial Dissolved Oxygen 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0

J1 (Single-Phase)

2.0

J2 (Single-Phase)

1.0

J3 (Three-Phase)

0.0 0

15

30

45

60

75

90

105

120

135

Days After Stocking

Figure 15: System B Summer Production Trial Dissolved Oxygen Concentrations. - 30 -


System A Summer Production Trial Growth Curve 18.0 16.0 H5-NW (Three-Phase)

14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0

15

30

45

60

75

90

105

120

135

150

Days After Stocking

Figure 16: System A Summer Production Trial Growth Curve

System A Summer Production Trial Temperature 34 32 30 28 26 24 22

H5-NW (Three-Phase)

20 18 0

15

30

45

60

75

90

105

120

Days After Stocking

Figure 17: System A Summer Production Trial Temperature Curve.

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135

150


System A Summer Production Trial Total Ammonia Nitrogen 2.0 1.8 H5-NW (Three-Phase)

1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

15

30

45

60

75

90

105

120

135

150

Days After Stocking

Figure 18: System A Summer Production Trial Total Ammonia Nitrogen Co ncentrations.

System A Summer Production Trial Dissolved Oxygen 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 H5-NW (Three-Phase)

2.0 1.0 0.0 0

15

30

45

60

75

90

105

120

135

150

Days After Stocking

Figure 19: System A Summer Production Trial Dissolved Oxygen Concentrations.

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Chapter 1 – Introduction

Chapter 1 Introduction by Kevan L. Main and Peter Van Wyk Harbor Branch Oceanographic Institution This manual was developed to provide an overview of the production strategies for farming marine shrimp in recirculating freshwater, greenhouse-enclosed, raceway production systems. A detailed review of the design and operation of these shrimp shrimp farming production systems and an economic analysis will be presented. The manual is intended for field use by shrimp farmers, farmers, students and extension agents. The focus is on the postlarval postlarval through growout phases of the production cycle and will not address broodstock or larval rearing issues. This publication and the demonstration study was funded by a contract from the Florida Department of Agriculture and Consumer Services (FDACS Contract No. 4520). Research conducted at Harbor Branch Oceanographic Institution demonstrating the technical feasibility of growing marine shrimp in freshwater has resulted in a surge of interest in shrimp farming from the aquaculture, agriculture and business community. Florida farmers have begun to seriously consider shrimp culture as a second crop and a few Florida farms have recently begun producing shrimp. Although Florida has lagged behind South Carolina and Texas in shrimp farming, farming, there are signs that the Florida shrimp farming farming industry is on the verge of development. New technologies have been developed that make shrimp farming a viable option in Florida. Florida. The feasibility of growing L. vannameiin vannameiin Florida's hard freshwater has been demonstrated and has greatly expanded the potential sites for shrimp farming. The technology for growing shrimp in intensive, enclosed culture systems is being refined and the economic analyses indicate that shrimp farming can be profitable.

An Overview of the Development of Shrimp Farming Litopenaeus vannamei (also known as Penaeus vannamei) vannamei) is the most extensively farmed species of marine shrimp in the Western Hemisphere. L. vannamei is rapid growing, tolerates high stocking densities, has a relatively low dietary protein requirement and tolerates a wide range of salinities. It is a hardy animal that is highly adaptable to culture conditions. The natural distribution of of L. vannamei extends from the Pacific coast of Mexico to northern Peru (Dore and Frimodt 1987). The technology for culturing marine shrimp is relatively new. The initial hatchery culture technology was developed in Japan in the 1930s and 1940s with Penaeus japonicus by Motosaku Fujinaga (Shigueno 1975). Breakthroughs in shrimp hatchery technology in the 1960s and 1970s paved the way for rapid growth of shrimp farming in the 1980s and 1990s. Annual world production of farm-raised marine shrimp has grown from 92 metric tons in

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Chapter 1 – Introduction 1982 to 737,200 metric tons in 1998 (Rosenberry 1998). In many areas around the world, shrimp seedstock are still collected from the wild and stocked in large coastal ponds. In the western hemisphere, Ecuador is the leading producer of farm-raised shrimp (Rosenberry 1998). The majority of the shrimp shrimp farms in Ecuador continue to rely on extensive growout techniques. In a typical extensive growout system, stocking is accomplished by flooding the ponds and bringing naturally occurring shrimp postlarvae into the pond, along with fish, crabs and other organisms. organisms. Little or no feeding is done and shrimp shrimp growth depends on the natural productivity productivity of the pond. Extensive systems produce around 50-500 kg/ha/yr. As the shrimp industry matured, producers adopted more intensive production methods. Stocking rates are closely monitored through the use of hatchery-reared postlarvae and the shrimp are fed specially formulated feeds. Most farms in the western hemisphere use a semi-intensive pond production strategy. Semi-intensive growout systems produce around 500-5,000 kg/ha/yr and the natural food in the pond is supplemented with formulated feeds. Intensive production systems produce around 5,000-10,000 kg/ha/yr (Brock and Main 1994). Shrimp are fed large quantities of formulated feeds, pond water is frequently exchanged and supplemental aeration is provided. A two-phase production system system may be used, where juvenile shrimp are grown at high densities in small nursery ponds. Juvenile shrimp are later transferred to large growout ponds, where they are reared to harvest. One of the obstacles to the development of commercial commercial shrimp farming in the U.S. has been the lack of a reliable supply of high quality seedstock. It is critical for U.S. hatcheries to be able to rear their own broodstock to produce high-health or specific pathogen free (SPF) seedstock for U.S. farms. farms. Reliance on broodstock and seedstock from other countries increases the risk of introduction of new shrimp diseases. Broodstock that are guaranteed to be free from specific disease-causing organisms are called "Specific Pathogen Free" (SPF) broodstock. Some states, such as South South Carolina, now require that all all shrimp seedstock sold sold in the state state come from from SPF broodstock. Development of new hatcheries should help to overcome the obstacle of a short supply of L. L. vannamei seedstock in Florida. Over the past twenty years there has been a significant increase in U.S. consumer demand for marine shrimp, while the U.S. commercial catch has remained relatively constant. Increasingly the demand for marine shrimp shrimp has been met by farm-raised farm-raised shrimp. Nearly 30% of the world shrimp supply is now being provided by pond aquaculture (Browdy 1998). Until recently, commercial shrimp farming in the United States has been limited to a few farms located in south Texas, South Carolina an d Hawaii. There are several reasons why commercial shrimp culture has been slow to develop in the United States. A combination of regulatory constraints, constraints, temperate climate conditions and high labor costs have limited the development of U.S. coastal shrimp ponds. Unlike the tropics, where air and water temperatures allow for year-round shrimp production, low temperatures during the late fall and early spring limit the production of this species to one crop per year (Main and Fulks, 1990). Higher U.S. land and labor costs and are also limiting factors. - 34 -


New Approaches and Considerations for Shrimp Farming The limited growing season and higher land values have forced U.S. shrimp farmers to adopt a more intensive approach to production. Researchers and farmers in Florida have recently been investigating intensive tank or raceway recirculating aquaculture systems. These systems are often enclosed in greenhouses to allow for greater control of temperature. A full description of the steps involved in greenhouse construction is presented in Chapter 3. The system design principles for recirculating, intensive raceway or tank production systems are discussed in Chapter 4. Stocking densities in intensive raceway culture systems systems range 2 from 100-250/m . Water in the culture system is typically typically circulated through a water treatment system that removes solids and nitrogenous wastes. Ultraviolet light or ozone is often used to reduce reduce bacteria levels in in the water. Blowers or liquid liquid oxygen are used to maintain adequate levels of dissolved oxygen in the water. Recirculating aquaculture systems require a higher level of technical expertise and are more expensive to build and operate than a pond culture system. system. However, there are are several advantages associated with these types of systems. They allow shrimp to be grown commercially in locations where land is limited or land values make pond construction prohibitively expensive. The controlled controlled environmental conditions allow for year-round production in areas otherwise restricted to a limited growing season. Water reuse technology can reduce the water requirements and discharge from the culture system, minimizing the environmental impact and permitting requirements for the operation. Harbor Branch is currently evaluating a relatively low-cost, recirculating production system. The design objectives and system features are described in Chapter 5 of this volume. Providing the animals with the optimum quantities of a nutritionally complete feed is one of the most critical critical aspects of shrimp husbandry. Feeds remain the single highest expense for farmers that are operating operating intensive production systems. systems. Feeds still need to be formulated to meet the nutritional requirements of shrimp farmed in intensive raceway production systems. Chapter 7 discusses the nutritional requirements and the feeding strategies that are appropriate for intensive shrimp production. One of the biggest challenges facing the shrimp industry industry is the control of disease in farmed shrimp populations. Effective strategies to control the occurrence and spread of disease are primarily related to management of the production system. The common health problems, diseases and strategies that farmers can use to control disease in L. in L. vannamei are discussed in Chapter 9. The success of a new aquaculture business is closely correlated with careful planning. Chapter 2 addresses three issues that need to be addressed as you are getting started in shrimp farming. The first issue is business planning. Training, marketing and the preparation of a business plan are all discussed. The second issue that must be addressed is obtaining the required permits to construct and operate a business. At the time this this manual was prepared, Florida’s permitting permitting requirements were undergoing revision. revision. The state was working with the - 35 -

Chapter 1 – Introduction key stakeholder groups to develop Best Management Practices (BMPs) for each of the commodity groups, including shrimp. shrimp. A general overview of the changes that have occurred in Florida’s permitting process is also discussed in this chapter. The third issue that needs to be examined is the suitability of your water source for shrimp farming. The parameters that need to be examined are listed and the water testing process is presented. The last chapter of the manual is an analysis of the economic feasibility of culturing marine shrimp in a hypothetical freshwater freshwater production system. The analysis in Chapter 10 uses the data gathered by Harbor Branch during the experiments conducted during the demonstration study and certain key assumptions to run the economic model. The assumptions, investment requirements, production inputs and operating costs are presented.

Freshwater Culture of Marine Shrimp The Pacific white shrimp’s tolerance to low salinities has greatly expanded the potential locations for shrimp aquaculture in Florida. That information, coupled with the desire of the agriculture community to diversify their production options, has significantly increased the interest in shrimp farming in Florida. Studies have shown that L. vannameican can be successfully farmed in freshwater raceways and ponds, provided the water is hard enough and has the correct mineral balance (Scarpa and Vaughan 1998; Scarpa et. al. 1999). Other penaeid species have also been shown shown to be adaptable to low salinities. Shivappa and Hambrey (1997) found that Penaeus monodon can be grown at salinities ranging from 2-3 ppt. Maturation and postlarval production of L. vannamei still requires saltwater. Once the postlarvae reach the PL12 to PL14 stage, stage, they can be acclimated to freshwater. At this stage, the gills are developing and they can withstand the osmotic stress (Scarpa 1998). Chapter 6 describes the procedures for handling and acclimating postlarvae from saltwater to freshwater production systems. The ionic composition of the well water in a number of locations around Florida appears to be suitable to support L. support L. vannamei and the results of a water testing program are presented in HBOI’s 1999 final project report to the Department of Agriculture and Consumer Services. A full discussion of the water quality parameters and requirements for culture of L. vannamei is presented in Chapter 8. Taste tests have shown that shrimp shrimp grown in freshwater are well accepted and are difficult to distinguish from those grown in saltwater.

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Literature Cited Brock, J.A. and K.L. Main 1994. A guide to the common problems and diseases of cultured Penaeus vannamei. vannamei. World Aquaculture Society, Baton Rouge, Louisiana, USA. Browdy, C.L. 1998 Recent developments in penaeid broodstock and seed production technologies: Improving the outlook for superior captive stocks. Aquaculture 164 (1-4):3-21. Dore, I. And C. Frimodt Frimodt 1987. An illustrated guide to to shrimp of the world. world. Osprey Books, Huntington, New York. 229 pp. Main, K.L. and W. W. Fulks 1990. The culture of cold-tolerant shrimp: Proceedings of an Asian-U.S. workshop workshop on shrimp shrimp culture. The Oceanic Institute, Makapuu Point, Honolulu, Hawaii. 215 pp. Rosenberry, B. (Ed.) 1998. World shrimp farming farming 1998. Shrimp News International. Scarpa, J. 1998. Freshwater recirculating systems in Florida. In: Moss, S.M. (Ed.) Proceedings of the U.S. Marine Shrimp Farming Program Biosecurity Workshop February 14, 1998. The Oceanic Institute. pp. 67-70. vannamei, in Scarpa, J. and D.E. Vaughan 1998. Culture of the marine marine shrimp, shrimp, Penaeus vannamei, freshwater. Aquaculture '98 Book of Abstracts, pp. 473. Scarpa, J., S.E. S.E. Allen and D.E. Vaughan 1999. Freshwater culture of the marine marine shrimp, Penaeus vannamei. vannamei. Aquaculture America '99 Book of Abstracts, Abstracts, pp. 169. Shigueno, K. 1975. Shrimp culture in Japa n. Assoc. for Int. Tech. Promotion, Tokyo, Japan. Shivappa, R.B. and J.B. Hambrey 1997. Tiger shrimp culture in freshwater? INFOFISH International 4/97:32-36.

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Chapter 2 – Getting Started

Chapter 2 Getting Started by Megan Davis-Hodgkins, John Scarpa and Joe Mountain Harbor Branch Oceanographic Institution

Introduction Several steps are involved in getting started in an aquaculture business. A thorough background review of the species you are interested in farming should be done. That review should include an evaluation of the production strategies that are appropriate for your site and lifestyle and the market opportunity. The next step is the development of a business plan. The business plan will identify the variables that should be considered before you make a decision to start a new aquaculture business. Be sure to have the water resource evaluated to determine if it is suitable for shrimp farming. The water quality parameters that need to be examined are briefly discussed and the water testing process is presented in this Chapter. Finally, you will need to obtain the required permits to construct and operate an aquaculture business. A short summary summary of the changes in Florida’s permitting permitting process during during the past few years is discussed in this chapter.

Planning Your Your Aquaculture Business Planning is the key to success in any business and aquaculture is no exception. The planning of your aquaculture business has to be done by you. There is no other business exactly like yours and you are the one who understands and can evaluate your personal and business goals. This section provides you with steps that will guide you in making decisions decisions on starting a new new aquaculture enterprise. The ultimate goal of this section section is to stress the importance of a well thought out business plan and the methodology to build your business plan. The steps that should be considered before be fore starting a new enterprise are: • • • • • • •

Expectations (personal considerations) Research and Training (know your species) Production Planning (inputs and outputs) Market Feasibility (selling the product) Business Plan (financial feasibility) Demonstration or Pilot-Scale Operation (test ideas - start small) Commercial-Scale Operation (expansion to profitability)

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Chapter 2 – Getting Started Expectations

When starting a new business it is important to balance this business with your personal life style and financial capabilities. capabilities. If the aquaculture business business is a change of career, you need to ask yourself three questions: "How strongly do I want to make a change? What do I want for my future? Am I willing to take a risk in a new business?" These questions may be best answered by considering the following set of questions: qu estions: 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16)

Are you interested in shrimp culture? Does your current job or business hold your interest? Do you have skills that you are not using and would like to incorporate in an aquaculture business? How much money do you expect to make? How much income do you need to operate your household? How much money can you afford to invest? Would you risk losing your savings on the new enterprise? Are you willing to absorb occasional losses? Are you willing to borrow money to finance the new business? How will the new venture impact your family? Is your family willing to relocate? Is your family willing to live on a reduced income until you sell your crop? For how long? Does your family support your directions and the risk? Will family members work in the business? Will this new venture supplement or replace your current job? Are you willing to devote the daily time and effort required?

Research and Training

If you are new to aquaculture and/or new to shrimp aquaculture, it is important to have a complete understand of the biology and the techniques techniques used to farm shrimp. This knowledge can be acquired through several methods such as: 1) 2) 3) 4) 5) 6)

attending short courses at training institutes or college/universities experiencing daily work routines as a volunteer or employee contacting local state agencies and extension agents for information attending professional meetings and trade shows reading articles, documents, or journal papers researching the topic through the internet

A combination of all of the above is probably the best way to become familiar with the working knowledge needed to develop a business plan, produce the animals, and operate a business. Experience, through trial and error, is is the most valuable way to learn the ins and outs of the business. Setting up a demonstration or pilot-scale operation is one way to gain this valuable experience and is discussed later in this chapter.

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Chapter 2 – Getting Started Production Planning

A production plan describes each step of the production process and identifies inputs, outputs and time requirements for for each phase of the operation. It is based on assumptions assumptions that come from documented research, commercial operations or personal experience. It is the first first step in developing information about the cost of production (operating and capital costs) and the expected yield (revenues). The emphasis for this production plan discussion is based on the nursery and growout production phase for shrimp. First, it is important to decide on the production system you will be using. This decision will take into account these factors: 1) 2) 3) 4) 5)

Biological requirements (environmental and nutritional parameters) Technological and commercial viability Resource availability Environmental impact Permitting requirements

Next the key variables need to be identified. These variables will affect the inputs and outputs of the production operation. Each of these these variables need to be assigned assigned values. These values need to be as realistic as possible and based on data reported for similar facilities producing shrimp. These are some examples of key variables for the nursery nursery and growout production phases: • • • • • • • • • • • • • • •

Number of production units Production unit area or volume Stocking density Growth rates Feed type Feed conversion ratios Stocking size Harvest size Survival Water exchange rates Aeration requirements Filtration requirements Energy requirements Labor requirements Chemical requirements

Here are a few examples of how to use these variables with assigned values. Usually the inputs and outputs are based on one production unit, then the value calculated can be multiplied by the number of units in a facility. In these examples a standard standard production unit will be one shrimp raceway:

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Example 1: How many postlarval shrimp are needed neede d to stock one unit? Production unit area = 90 m2 Stocking density = 230 shrimp/m2 90/m2 x 230 shrimp/m2 = 20,700 shrimp total

Example 2: What is the survival from the beginning of the operation to the final harvest for one production unit? Number stocked = 20,700 shrimp Survival = 69% 20,700 shrimp x 0.69 = 14,283 shrimp Example 3: 3: What is the total harvest weight per production unit? Number harvested = 14,283 shrimp Average weight of shrimp = 18 grams (14,283 shrimp x 18 grams) ÷ 1000 grams = 257 kg (566 lb) Example 4: How much food is needed to feed the shrimp from stocking to harvest? Feed conversion ratio (FCR) = 2 Total weight at harvest = 257 kg (566 lb) 2 x 257 kg of shrimp = 514 kg (1131 lb) of feed Example 5: How many production cycles per p er year for a standard production unit? Days from stocking to harvest = 158 days Fallow days = 4 days 365 days/year ÷ 162 = 2.2 cycles/year

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After each of the key variables are calculated dollar values can be assigned. Here are some examples of how to apply dollar values. va lues. Example 1: What is the cost of the postlarvae to stock one production unit? Number of postlarvae = 20,700 shrimp Cost per 1000 acclimated postlarvae = $20/1000 shrimp (20,700 shrimp ÷ 1000 shrimp) x $20 = $414 Example 2: How much does the food cost to grow one crop? Amount of food needed for one crop = 1131 lb Average cost of food = $0.45/lb 1131 feed x $0.45/lbs = $509 Example 3: What is the revenue generated from one crop? Amount of shrimp harvested = 566 lb Revenue = $5.25/lb head-on shrimp 566 lb shrimp x $5.25/lb = $2972 per crop If there are two crops per year from one raceway = $5943 per raceway You can build a production plan from two two directions. You can ask yourself: yourself: How much product do I want to produce to get the desired revenue? or How much capital do I have available to invest? In either case, the revenue has to make money or a profit. The next example will assist you in determining how much production area is required to produce 30,000 kg (66,000 lb) of 18 g shrimp per year. year. Assume 2 crops/yr/raceway, crops/yr/raceway, 69% survival, 2 and an average stocking density of 230 post larval shrimp/m . Weight Harvested

= 30,000 kg/yr ÷ 2 crops/yr = 15,000 kg/crop

No. harvested

= 15,000 kg ÷ 0.018 kg/shrimp = 833,333 shrimp

No. postlarvae stocked

= 833,333 shrimp ÷ 0.69 survival = 1,207,729 postlarvae

Area required

= 1,207,729 postlarvae ÷ 230 shrimp/m2 = 5,250 m2

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Most customers will will want to have fresh shrimp delivered every week. How many production units are needed to harvest one unit per week? How big would this unit have to be? These calculations will be based on production of 30,000 kg shrimp harvested per year. 1 harvest/week x 52 weeks/yr = 52 harvests/yr No. of production units

= 52 harvests/yr / 2 harvests/yr/production unit = 26 production units

This means 26 production units would be required to allow for 1 harvest per week. In the above example it was determined that the production area to meet annual production target is 5,250 m2. Now you can calculate how large each unit should be: Area/production unit

= 5250 m2 ÷ 26 production units = 202 m2

In summary, approximately 2 raceways (90 m2 each) need to be harvested per week to meet the annual production quota of 30,000 kg of shrimp. If there are 4 raceways per greenhouse, greenhouse, then 13 greenhouses would be needed to grow 30,000 kg of shrimp per year. These examples were used to illustrate how to calculate production numbers, infrastructure size, harvest schedules, and revenue. These numbers should not be used as accurate numbers for your business plan. This is only a guide to help you in the development of your your plan. Refer to the last chapter of this volume for additional information on production figures. Market Feasibility

Production must be driven by marketing. marketing. If you cannot sell your product or sell your product at the price needed to make the business profitable, then the business will fail. The marketing plan should be developed alongside the production plan. The market analysis is usually the most difficult section because the prospect of marketing and selling your product is a long way off; between 4-6 months after stocking for farm-raised farm-raised shrimp. Planning ahead will turn your concept into a producing profitable operation with a consistently available and high quality product that people want to buy. There are five steps to market analysis: 1) define product market structure 2) determine relevant market 3) analyze demand 4) segment the market 5) determine market position

Florida farmed shrimp cannot compete with imported, fresh-frozen shrimp prices in the commodity markets. Therefore, the most feasible alternative for for Florida farmed shrimp is to sell the product directly to restaurants, retailers and consumers. This marketing strategy is - 44 -


called direct marketing and/or niche marketing. Unless a processing facility is going to be included in your business, the product forms that you will most likely be marketing are live shrimp or fresh fresh heads-on shrimp. These product forms will will require minimal processing and regulatory requirements. Any processing beyond the live live or fresh, fresh, heads-on product form will incur additional costs, effort and expertise to realize the full economic potential of producing a processed product. There is limited knowledge on the direct markets for marine shrimp raised in intensive freshwater recirculating systems. Now is the time to investigate the market for Florida farmraised shrimp. The specific areas that need to be analyzed for the shrimp marketing plan include: 1) Identify and quantify fresh shrimp direct markets. Which of the shrimp direct markets are most attractive for shrimp farmers, in terms of market size and the willingness of the purchaser to buy directly from the farmers? 2) Determine the value, demand and product characteristics for each of the direct markets. What are the product requirements (shrimp (shrimp size, size, price, shelf life, life, delivery terms) for each of the direct markets? 3) Test consumer and direct market buyer attitudes and acceptance of marine shrimp grown in freshwater versus domestically wild-harvested or imported farm-raised products, relative to sensory attributes (appearance, flavor, texture) and yield (edible cooked meat from fresh vs. frozen product). 4) Prove the shelf life and product quality/safety parameters for direct farm sales of whole, fresh shrimp. shrimp. Include handling parameters and packaging to extend shelflife, and Hazard Critical Control Point (HACCP) and Sanitation Standard Operating Procedures (SSOP) models to assure product safety. Business Plan

The next step after the production plan and market market analysis is the business plan. Why a business plan? The business plan summarizes the business opportunity. It motivates motivates you to find out all the information needed to make a successful business. This process must be done before any purchases are made. You are testing testing your ideas on paper, which minimizes mistakes and risks. risks. This point cannot be stressed enough!! If you are seeking funding from investors, a bank or venture capitalists, they will not consider your ideas without without a well thought out plan. The business plan is the principal sales tool in obtaining a loan loan or raising equity capital from investors. investors. Loan officers and investors investors want to be sure that you have thought through your plan carefully, that you know what you are doing and that you can respond effectively to problems (crisis) and opportunities that arise.

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The business plan can also also be used as a planning document. It allows you you to organize your directions and evaluate the anticipated outcome of your company. You can use your business plan to set goals and assess your progress. There are usually 7 parts of a business plan: Executive Summary, Business Description, Market Analysis, Management Team, Financial Information, Milestone Schedule, and Appendix. Each of these these parts are discussed below.

The Executive Summary is presented first, but is usually written last. The investor reads this first - it is the “first impression” of your your business. This summary must convince the reader to continue reading the plan. It should be no more more than 3 pages in length (preferable 1 page), it contains only information from the body of the business plan and the wording should be active and forward thinking. This summary needs to include: include: why the business will succeed, what is the market product, what market the product will meet, assessment of the competition, management team’s expertise, amount of money needed in terms of capital and operational expenses, the projected internal rate of return and why this venture is a good risk. This section could be prefaced with a short Mission Statement.

This is the major section section of the business plan. The business is described with with the following information: history of the company, product description, ownership, markets being served, location and site, permits and licenses, facilities and equipment, operations and culture techniques, cost breakdown and labor force. In this section, you also need to describe certain risks you may encounter. Some of the primary risks associated with most commercial aquaculture ventures are the following: drops in market price, disease, extremes in weather, management problems and electrical failure. Addressing these risks in the business plan will will assist you in determining what to do to avoid risks. risks. It shows the investors your knowledge of the business venture and how you will handle critical risks.

This part discusses discusses market size and trends, competition and regulatory requirements. The market size and trends can be supported with industry trends and graphs. The strengths and weaknesses of competing businesses should be described. These competing businesses will probably include other aquaculture ventures and the commercial fishery. Your product should be compared with the competitor’s product product ($, quality, availability). availability). The product form will dictate what regulatory permits and licenses will be required. This part should also describe what markets will be met and how ho w the product will be marketed (i.e., advertisement)

The management team needs to have a balance of skills in marketing, finances, management and production. A brief review of the duties and responsibilities responsibilities of each person needs to be outlined. It is important important to discuss discuss how each person will be compensated (salary, profit sharing, incentive sharing). Depending on the structure of the company, it may be necessary to discuss the shareholders, board members and professional services. An organizational chart is very helpful. - 46 -


The financial statements and cash flow balance sheets should include startup years and the projections should continue for 5 years after the the commercial business is fully functional. A narrative of the capital costs (land, facilities, equipment - the non recurring costs), operational costs (salaries, feed, postlarvae, electricity, insurance – costs that occur daily, weekly, yearly) yearly) and revenue is included along with the spreadsheets. A breakeven and sensitivity analysis shows you what key variables are controlling the success of the company. This is a valuable analysis to to present in your your business plan. The net present value and internal rate of return are the numbers you and your lenders or investors are most interested in.

The schedule shows the projected timeline of the business. It includes all start-up operations, production schedules schedules and harvesting times. It is typical for a start-up shrimp operation to havest the first crop 12-24 months from the time you begin to plan and build your facility.

The appendix usually includes additional details to further describe your business. Marketing studies, letters of interest, photographs and technical drawing, resumes, news clippings and character references are are a few examples examples of what can be included in the appendix. Demonstration or Pilot-Scale Operation

A demonstration or pilot-scale operation is a scaled-down version of the commercial business. It is built with the same same infrastructure and equipment, but may only include one to four greenhouses instead instead of 12-20 greenhouses. Even though a demonstration demonstration size facility facility may not make money or breakeven it will save save you money in the long run. This facility is a prototype that is used to test ideas, to learn where to make improvements, to find out the demands of the business, to learn the methodologies to culture shrimp and to test your marketing plan. A demonstration facility will prove to you and to your lenders and investors investors that you know what you are doing. It is highly recommended that this this demonstration project proceed the commercial business. This pilot-scale pilot-scale operation should either have it’s it’s own production and business plan or be part of the main business plan. Start small and scale up slowly. Learn as you go and invest as you learn. Commercial-Scale Operation

By the time you get to the commercial- or production-scale business you have done all your homework. You have written a well-thought out business plan and are demonstrating your ideas in a small-scale facility. facility. It may take 2-3 years to scale-up to a commercial size size business, but once you are there, you will be operating a production business that will continue to bring you revenue harvest after harvest.

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Water Selection Criteria When you are culturing an aquatic organism, one of the most important variables to consider is the water. In order to select the water you are going to use, you need to know what the water quality parameters are for the organism you will culture. In this chapter, we will consider the culture environment for the marine shrimp, Litopenaeus vannamei, being grown in freshwater. All the parameter levels presented here have not been experimentally evaluated for culturing L. vannamei in freshwater. Having a supply of good water is essential in aquaculture and should meet the specific environmental needs of the organism to be cultured. The following list is a synopsis on the water quality parameters that should be checked during the evaluation of the site for shrimp culture. A more detailed discussion discussion of these parameters can be found in Chapter 8 - Water Quality Requirements and Management. All water samples should be tested for pH, total ammonia nitrogen, nitrite, nitrate, total hardness, calcium hardness, total alkalinity, salinity, chloride and hydrogen sulfide. The acceptable values for each of these variables is listed in Table 2-1. Additionally, the water should be tested for heavy metal, pesticide and herbicide contamination if there is a reason to suspect that the site was previously used for agricultural or industrial purposes (see Chapter 8).

Table 2-1. Water quality variables and acceptable ranges. VARIABLE

total ammonia nitrogen nitrite nitrate total hardness calcium hardness total alkalinity salinity chloride hydrogen sulfide

RANGE

pH

7-9 <0.1 ppm <1 ppm <60 ppm >150 ppm as CaCO3 >100 ppm as CaCO3 >100 ppm as CaCO3 >0.5 ppt >300 ppm <0.002 ppm

Finally, a bioassay should be performed using the source water and shrimp postlarvae. Bioassays use living organisms as indicators. In the case of aquaculture, bioassays should be conducted using the organism to be cultured. Bioassays are an important consideration during the selection of a site for aquaculture. The use of water quality data alone, without without including a bioassay, can lead to false conclusions regarding the suitability of the water. Even after basic water quality parameters are identified, including pesticide and herbicide presence, the results of a bioassay with the intended culture organism is insurance that the site will be productive.

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Permitting Before 1990, obtaining the requisite permits to develop an aquaculture project in the State of Florida was an ordeal. Depending on the part of the State one wanted to work in, the degree of difficulty could vary greatly. In April 1990, a publication entitled "Florida Aquaculture Regulatory Sourcebook, Leasing, Licensing and Permitting Requirements for Aquaculture in Florida" was made available. It contained information information compiled by James W. Miller, Ph.D., Florida Institute of Oceanography. In its 252 pages, he attempted attempted to outline and clarify regulatory procedures affecting Florida aquaculture, and emphasized the need for and the means of obtaining the more than 50 leases, licenses and permits described therein. According to Dr. Miller, the major aquaculture activities in Florida in the late 1980’s were tropical/ornamental fish, and aquatic plant production. production. Their overall economic impact approached $150 million. He identified eighteen other types of Florida aquaculture activities involving organisms listed listed alphabetically from alligators to watercress. watercress. However, there was no mention of shrimp. In 1993, it was demonstrated that one particular species of marine shrimp , Litopenaeus vannamei, could be raised in hard "fresh water" in Florida. For the 25 years prior to this time , L. vannamei had been present in aquaculture activities in the State, but always in coastal/saltwater conditions. The fact that this species thrived, grew and tasted normally, normally, under hard "fresh water" conditions, showed that inland shrimp aquaculture was a realistic possibility. In 1999, The Florida Legislature designated the Florida Department of Agriculture and Consumer Services (Department) as the clearinghouse for aquaculture permitting. This makes the process more streamlined, i.e., one phone call to the Division of Aquaculture at (850) 488-4033 initiates the process. Each case is handled individually. The department will provide an Aquaculture Certificate of Registration application and assist you through the environmental permitting process or implementation of the Best Management Practices(BMPs) specific to your your situation. situation. The Department has adopted an Interim Rule continuing the above process until BMPs are later adopted. Federal, county and local local permitting will be the responsibility of the individual producer. The Division of Aquaculture may be able to provide some guidance. Under the proposed BMPs, shrimp producers must adopt and implement both the required sections of the General BMPs and the required sections of the shrimp specific tabbed section as the BMPs conform to the individual operation. Other suggested BMPs may be adopted to enhance the facility’s operation and production. If the required BMPs are not adopted or implemented, Environmental Resource Permits, NPDES permits and/or other required permits will be the responsibility of the producer and are prerequisites for certification of registration.

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Literature Cited Avault, J. W., Jr. Jr. 1996. Fundamentals of Aquaculture, A Step-by-Step Step-by-Step Guide to Commercial Commercial Aquaculture. AVA Publishing Co., Inc. Baton Baton Rouge, Louisiana. Harbor Branch Oceanographic Institution. 1995. Aquaculture Options for Commercial Fishermen. Prepared for Florida Department of Labor and Employment Security. Security. Stromborm, D.B. and Tweed, S.M. 1992. Business planning for aquaculture - is it feasible? feasible? Northeast Regional Aquaculture Center Fact Sheet No. 150.

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Chapter 8 – Water Quality Requirements and Management

Chapter 8 Water Quality Requirements and Management by Peter Van Wyk and John Scarpa Harbor Branch Oceanographic Institution

Introduction Water used for aquaculture is more than just H2O. Water contains many ionic and non-ionic elements that make up what is termed "water quality". The concentration of dissolved inorganic ions, dissolved gases, suspended solids, dissolved organic compounds, and microorganisms determine the the suitability of the the water for aquaculture. Simply put, a supply of good water is essential in aquaculture and good water meets the specific environmental needs of the organism to be cultured. Why is water quality so important? Water is is the environment in which aquatic organisms live. Their bodies and gills gills are in constant contact with what is dissolved and suspended in the water. Therefore, water quality directly affects the health and growth of the cultured organism. Poor water quality leads to stress, stress, disease and, ultimately, death. Water quality is not a fixed characteristic of the water. The quality of the water is very dynamic, changing over time as a result of environmental factors, and biological processes. Initially, water quality is initially initially related related to the source of the water. For example, if the water comes from a well, it may be low in dissolved oxygen and high in ammonia, iron, hydrogen sulfide, carbon dioxide, or a combination of these. Depending on mineral composition of the region, the source water may be hard and alkaline, or soft and acidic. After the water is in a culture system, its quality may be altered by biological processes such as photosynthesis, respiration, and excretion of metabolic wastes, as well as by physical processes such as temperature temperature and wind. Water quality may may even be altered by management management strategies, such as overfeeding that leads to suspended solids and eutrophication of the system. To be successful, an aquaculturist must must regularly monitor the water quality variables which are critical to the health of the organisms being cultured and understand the factors which affect these variables. Water quality requirements differ for different species and sometimes for different stages in the life cycle of the same species. For example, the salinity requirements requirements of the Pacific white vannamei, are a function of developmental stage. Adult shrimp mature shrimp, shrimp, Litopenaeus vannamei, and spawn in seawater with a salinity of at least 28 ppt. The early larval stages also require seawater. However, postlarval shrimp migrate migrate into estuaries, an environment which may may experience extreme fluctuations in salinity. salinity. By the time time the shrimp shrimp become a PL12 they can successfully acclimate to near freshwater conditions. Frequently early developmental stages of a culture organism are more susceptible to certain toxic compounds than are older animals. For example, the LC50 concentration of nitrite for postlarvae is about one-tenth of the LC50 concentration of nitrite for sub-adults. The aquaculturist must understand the water quality

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Chapter 8 – Water Quality Requirements and Management requirements of each stage in the lifecycle of the culture species, and make sure that the culture system provides water suitable for the stages being cultured.

Water Quality Testing During Site Selection The chemical characteristics of the source water is one of the most important considerations in choosing a site for an aquaculture enterprise. Some water quality parameters may be easily adjusted to bring it within acceptable limits. For example, concentrations of toxic dissolved gases, such as carbon dioxide and hydrogen sulfide, can be economically reduced to safe levels by passing the water through a degassing degassing tower. High ammonia levels in the source water can usually be reduced to safe levels by passing the water through a biofilter. biofilter. Other parameters can be modified, but at a significant cost. Salinity is a good example. While it is possible to add prepared mixes of ocean salts to freshwater to make seawater, it is not usually economical to to do this on a large scale. However, if the salinity salinity of the the source water is not too far out of range, chemical additions may not be prohibitively expensive. Some water quality parameters cannot be economically modified, so the source water must be within acceptable limits. High concentrations of toxic compounds such as pesticides, herbicides, and heavy metals disqualify a site for aquacu lture. A full range of water quality parameters should be tested before deciding to build an aquaculture facility on a given sit. Table 8-1 gives a list of water quality parameters that should be tested and the acceptable limits for shrimp culture. Table 8-1:

Recommended Range of Water Water Quality Parameters Water Quality Parameter Temperature Dissolved Oxygen Carbon Dioxide pH Salinity Chloride Sodium Total Hardness (as CaCO3) Calcium Hardness (as CaCO3) Magnesium Hardness (as CaCO3) Total Alkalinity (as CaCO3) Unionized Ammonia (NH3) – Nitrite (NO 2 ) = Nitrate (NO3 ) Total Iron Hydrogen Sulfide (H2S) Chlorine Cadmium Chromium Copper Lead Mercury Zinc - 142 -

for Shrimp Shrimp Culture

Recommended Range 28 - 32 ºC 5.0 - 9.0 ppm ≤ 20 ppm 7.0 - 8.3 0.5 - 35 ppt ≥ 300 ppm ≥ 200 ppm ≥ 150 ppm ≥ 100 ppm ≥ 50 ppm ≥ 100 ppm ≤ 0.03 ppm ≤ 1 ppm ≤ 60 ppm ≤ 1.0 ppm ≤ 2 ppb ≤ 10 ppb ≤ 10 ppb ≤ 100 ppb ≤ 25 ppb ≤ 100 ppb ≤ 0.1 ppb ≤ 100 ppb

Chapter 8 – Water Quality Requirements and Management The water from a prospective site should also be analyzed for pesticides. pesticides. Shrimp, like insects, are arthropods, and are are very susceptible to to insecticides. To the author’s knowledge, the lethal limits of many of these pesticides have not been determined for penaeid shrimp. However these pesticides are toxic to most most aquatic organisms. organisms. Table 8-2 lists the range of LC50 levels for a variety of other aquatic organisms, as well as the safe levels recommended by the U.S. Environmental Protection Agency. Table 8-2: Toxicity of Pesticides to Aquatic Organisms and Safe Levels Recommended by the U.S. Environmental Protection Agency

Range of 96-hr LC50 Safe Level* (ppb) (ppb) Aldrin/Dieldrin 0.2 - 16 0.003 BHC 0.17 – 240 4 Chlordane 5 – 3000 0.01 DDT 0.24 - 22 0.001 Endrin 0.13 - 12 0.004 Heptachlor 0.10 - 230 0.001 Toxaphene 1-6 0.005 *Recommended safe levels by the U.S. Environmental Protection Agency Pesticide

In addition to testing testing the chemical composition composition of the water, bioassays may be used to determine if the culture organisms can live in the water. Bioassays are tests that use living organisms as indicators. To test the suitabilitity of water for aquaculture, the culture organism is placed in the water being tested to determine the percentage of animals that survive over a determined time time period. Although many of the water quality requirements are known for cultured organisms, the use of water quality data alone, unless exhaustively done, may miss an essential parameter. Even after basic water quality parameters are identified, including pesticide and herbicide presence, the results of a bioassay with the intended culture organism is insurance that the site will be productive. The water quality parameters measured and bioassay results only give an indication of the potential for using a water source to culture marine shrimp. There are many variables (e.g., management, business plans, natural catastrophes) that will affect the success of such an operation that are beyond the scope of water quality and bioassay tests. tests. Following is a discussion of individual water quality parameters for culturing the marine shrimp, Litopenaeus vannamei, in freshwater. The parameter levels indicated have not all been scientifically tested for culturing the Pacific white shrimp in freshwater, but are generally accepted for culturing aquatic organisms or the Pacific white shrimp.

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Salinity 

(Requirement: >0.5 ppt or >300 ppm chloride)

Salinity is a measure of the total concentration of dissolved inorganic ions, or salts, in the water. The salinity of seawater typically ranges from about 28 - 35 parts per thousand (ppt). One part per thousand is equal to 1 gram of inorganic salts per liter of water. Freshwater is usually defined as water that has less than 1 ppt of salinity. Estuarine water is a mixture of freshwater and seawater and therefore the salinity of estuarine water is intermediate between the salinity of seawater and freshwater. The salinity of estuarine water depends on the relative amounts of freshwater and seawater in the mixture. A mixture of salts contribute to the salinity salinity of seawater. The most prevalent salt is typically sodium choride (table salt, NaCl). Salts are compounds that when dissolved in water dissociate into positively charged ions (called cations) and negatively charged ions (called + ++ anions). The most common cations in seawater are sodium sodium (Na (Na ), magnesium (Mg ), ++ + calcium (Ca ), and postassium (K ). The most common anions are chloride (Cl ), sulfate = (SO4 ), bicarbonate (HCO3 ), and bromide (Br ). There are a variety of ways to measure the salinity of the water. Three methods for measuring salinity are based on the effect of o f salinity on the physical properties of the water. A refractometer is a device that measures salinity based upon the refractive index of the water. Light waves passing through a thin film of water are refracted, or bent, by the water. The amount of refraction, called the refractive index, is proportional to the concentration of dissolved salts in the water. The higher the salinity, the higher the refractive refractive index. A refractometer consists of a prism positioned at the end of a viewing tube with a focusing ocular lens. A drop of water is placed on the surface of the prism. A transparent cover plate is placed over the water droplet and the prism pressing pressing the water into a thin film. The salinity is read by holding the refractometer up to a light source and viewing the amount of refraction through the lens at the end of the viewing tube. The viewer will see a blue field field over a lighted white field, with a sharp horizontal border between the two fields. The prism has a salinity scale etched into the glass that is visible when viewing through the viewing tube. The salinity is read by reading the salinity on the scale at the point of the border between the white and blue fields. fields. A properly calibrated refractometer has an accuracy of ± 1 ppt of salinity. It is a very easy way to measure salinity and works well for measuring salinities salinities from 2 or 3 ppt to full full strength seawater. At lower salinities other measurement techniques are required for greater accuracy. Hydrometers are devices which measure salinity based upon the specific density of the water. The density of water increases in a near linear fashion with increasing concentrations of dissolved salts. The buoyancy of objects in the water is directly directly related to the density of the water. A hydrometer is a device in which an object is floated in the water and the degree of flotation is measured. measured. How far the object sinks into the water is inversely proportional to to the salinity. A calibrated scale is etched into the object which allows the the salinity to be read. Hydrometers typically express salinity salinity as specific density. Specific density is the ratio of the - 144 -

Chapter 8 – Water Quality Requirements and Management density of the water to the density of distilled distilled water. Seawater with a salinity of 35 ppt has a specific density of 1.0282 at 4°C. 4°C. Most hydrometers hydrometers are not designed to measure small variations of the salinity of seawater and, therefore, are not useful for measuring low salinities. Conductivity meters measure the resistance of water to electrical flow, which is inversely proportional to the salinity. As salinity decreases, the resistance to electrical flow increases. -1 The resistance is measured in µmhos cm (pronounced micro moes per centimeter). A mho is the reciprocal of an ohm, which is the unit in in which electrical currents are measured. measured. A conductivity meter measures the electrical resistance to a current passing through the water between the anode and cathode of an immersed immersed electrode. Tables can be used to convert specific conductivity measurements into salinity measurements. If sodium chloride is the dominant salt in the the water, the salinity can be estimated by the concentration of chloride ions in the water. Chloride makes up approximately 55% of the weight of inorganic ions in seawater seawater at 35 ppt. Using this relationship, one can calculate the approximate salinity in parts per thousand by dividing the measured chloride concentration by 550. For example, if the chloride concentration was found to be 300 ppm (1 ppm = 1 mg/L or 0.001 g/L) the corresponding salinity would be 0.545 ppt (= 300/550). This is an accurate and inexpensive method for determining the salinity for water with very low salinities in which the dominant salt is sodium chloride. Chloride can be measured using a titration method for which simple kits can be pu rchased from any aquaculture supply catalog. Aquatic organisms may be classified according to their tolerance to changes in salinity. Stenohaline organisms are adapted to a very narrow range of salinities, while euryhaline organisms tolerate a wide wide range of salinities. Organisms that normally live in environments with very stable salinities (e.g., freshwater lakes and open ocean) tend to be stenohaline, while organisms that live in environments with variable salinities (e.g., estuaries) tend to be euryhaline. The salinity requirements requirements and tolerance to salinity variation may change throughout throughout the life cycle of an organism. organism. This is the case for most most species of penaeid shrimp. Adult shrimp mature, mate and spawn in in water with salinities salinities between 28 and 35 ppt. Early larval stages vannamei, however, are estuarine also require full strength seawater. Juvenile Litopenaeus vannamei, organisms and are extremely euryhaline, tolerating salinities ranging from less than 1 ppt to nearly 40 ppt. The physiological capability of penaeid shrimp to osmoregulate (regulate their internal salt and water balance) develops gradually while the shrimp are still in the postlarval stages. The gill filaments serve as the primary primary osmoregulatory organ in shrimp. shrimp. In low salinity water the the shrimp must selectively selectively retain salts and excrete excess water. The gills serve as the primary site for water excretion. The effectiveness of the gills as an osmoregulatory organ is a function of the developmental stage of the shrimp. Shrimp in the early postlarval stages have insufficient gill surface are to be able to osmoregulate effectively at low salinities. The osmoregulatory capability of the shrimp improves dramatically once the gills begin to branch, which usually usually occurs after PL6. PL6. By the time the shrimp shrimp are a PL12 the gills have enough surface area to allow them to be gradually acclimated to near-freshwater conditions (see Chapter 6).

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Chapter 8 – Water Quality Requirements and Management Research at HBOI indicates that 0.5 ppt total salinity is probably the minimum level for the Pacific white shrimp to survive and grow to a marketable size. Chloride ion concentrations are the best predictor of the ability of shrimp to survive at least 24 hours in freshwater from a particular source. Twenty-four hour survival rates of shrimp postlarvae (PL15+) decline when chloride concentrations drop below 200 mg/L. Many other inorganic ions, including sodium, calcium, magnesium, potassium, and bicarbonate, are also required in some minimum amount for normal growth and development of the shrimp, but at this time the minimum requirements for these ions are not clear. It appears that total hardness (the combined concentration of calcium and magnesium ions) needs to be above 150 mg/L. Freshwater that has a low chloride concentration, or total hardness, may be made suitable for shrimp culture by adding the deficient salts to the water. If the water is found to contain insufficient chloride ion, the addition of solar or marine salt to your your water may be the only modification necessary to make make your water suitable for for culture. Solar salt may may be used to bring the salinity up to the levels required by the shrimp. Make sure that the salt that does not contain yellow prussiate of soda, a non-caking agent that is highly toxic to the shrimp. Marine salt is more expensive but contains other ions and trace elements that are necessary for the health of the shrimp. Other compounds can be added to the water to supplement hardness or alkalinity (see below). To calculate the amount of salt needed, first subtract the amount of salt in your water from 0.5 ppt (if you wish wish to use a higher level, level, e.g., 0.75 ppt, you may). For example, if your water was found to contain 38 ppm chloride you would first have to calculate your total salinity (38 ppm/550 = 0.069 ppt). ppt). Therefore, 0.5 ppt minus 0.069 ppt = 0.431 ppt, which corresponds to 0.431 g salt that will need to be added per liter of water. If your tank was 2500 gallons (9450 L), you you would need to add just over 4 kilograms kilograms of salt to your system (0.431 g/L x 9450 L = 4073 grams of salt). Additional salt will need to be added when new water is added the system to replace water lost during backwash of filters. Perhaps the safest way to do this would be to adjust the salinity of the replacement water in a reservoir before adding the new water to the culture tank.

Temperature 

o

o

(Optimal: 28-32 C/82-90 F)

Litopenaeus vannamei, vannamei, like all crustaceans, is poikilothermic (cold-blooded). This means that they are not able to regulate their body temperature. temperature. The shrimp's body temperature will normally be in equilibrium equilibrium with the water temperature. temperature. This has profound consequences for the physiology of the shrimp because the rates of biochemical processes are temperature dependent. According to Van Hoff's Law, a 10ºC temperature increase will roughly double the rate of most biochemical reactions. This means that the temperature of the water directly affects the metabolism of the shrimp. As temperature increases, the metabolic rate will increase until a maximum rate rate is reached. As the temperature increases increases above that rate, the metabolic rate will decline rapidly until the temperature reaches an upper lethal limit. limit. Many important processes are affected by the metabolic rate of the shrimp. shrimp. The rates of feed

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Chapter 8 – Water Quality Requirements and Management consumption, oxygen consumption, ammonia excretion, and growth are all directly related to the metabolic rate of the shrimp. Shrimp can survive over a wide range of temperatures. The lower lethal limit is approximately 15ºC (59ºF), although shrimp may survive colder temperatures for a short period of time. The upper temperature limit limit for L. vannamei is about 35ºC (95ºF) for prolonged periods, or up to 40ºC for brief periods. The optimal temperature temperature range is much o narrower. While shrimp will survive temperatures below 24ºC (75ºF) and above 32 C o (90 F), outside of this range the shrimp will be stressed stressed and will not grow well. The temperature range for maximum growth is even na rrower, ranging from 28-32ºC (82-90ºF). In tropical environments, temperatures are suitable for shrimp shrimp culture year round. The cool winters in Florida limit the growing season for shrimp in outdoor ponds to about 220 days/year. Greenhouses can significantly extend the growing system, system, but the water must still be heated to maintain optimal growing temperatures year round. Ideally, the water temperatures within the culture tanks should be maintained within the temperature range for maximum growth (28-32ºC). The daily variation variation in temperature should never exceed 4ºC. Fluctuating temperatures are stressful for shrimp, as well as for the bacteria in the biofilters. There are many different options for heating the culture tanks, including propane-powered heat exchangers, solar-powered heat exchangers or water heaters, electrical immersion heaters, and propane-powered space heaters. As a general principle, it is usually more costeffective to heat the water directly than it is to maintain water temperatures by heating the air inside a greenhouse. Solar heating systems systems are very attractive because they are inexpensive to operate. However, the initial capital cost may be high and they may not be able to maintain temperatures temperatures during protracted periods of cold cloudy weather. Propane heat exchangers and electrical immersion heaters provide the highest degree of temperature control. If properly sized, these systems should be able to maintain temperatures to within within ±1ºC. The operating costs of a propane heat exchanger system system are likely to be cheaper than the electrical costs for immersion heaters. High water temperatures may become a problem during the summer months. In greenhouse systems, thermostatically controlled extractor fans and shuttered windows provide air exchange that helps cool the air temperatures temperatures within the the greenhouse. Without air exchange the air temperture within a greenhouse may be as much as 11ºC (20ºF) above ambient outside temperaure. Air exchange alone, however, may not be sufficient to control water temperatures in the summertime. Covering the outside outside of the greenhouse with a 90-95% shade cloth will help maintain the water temperatures within an acceptable range even on hot sunny days. The shade cloth will also limit the growth of algae within the culture system. This may be considered a benefit from the standpoint that dissolved oxygen, pH, and unionized ammonia concentrations fluctuate widely in systems with high algal densities. Some producers, however, may want to maintain controlled blooms of algae within their systems. These producers might benefit benefit from installing installing evaporative cooling panels on the opposite end of the greenhouse from the exhaust fans.

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Dissolved Oxygen 

(Optimal: > 5 mg/L or ppm)

Oxygen is required by shrimp for respiration, the physiological process in which cells oxidize carbohydrates and release the energy needed to metabolize nutrients from the feed. If oxygen is in short supply, the ability of the shrimp to metabolize feed will be limited, causing growth rates and feed conversion to suffer. Best growth and feed conversion ratios (FCRs) are obtained when dissolved oxygen (D.O.) levels are maintained at or above 80% of the saturation level (see Table 8-3). 8-3). As a general rule, no stress will be placed upon aquatic organisms (including shrimp) if dissolved oxygen (D.O.) levels are maintained above 5 ppm. Prolonged periods of low oxygen concentrations (less than 1.5 ppm) are lethal, although shrimp can survive for short periods of time time with as little as 1 ppm. If a level of 3 ppm or lower is found, measures should be taken to correct the problem. The solubility of oxygen in water is a function of temperature, salinity and altitude. As salinity, temperature, and altitude increase, the solubility of oxygen in water decrease (see o o Table 8-3). Freshwater at a temperature of 26 C (79 F) will have a D.O. of 8.1 ppm at o o saturation, but at 30 C (86 F) can only hold 7.6 ppm at saturation. The solubility of oxygen in seawater is significantly lower than in freshwater, but over a narrow range the influence of salinity is not pronounced. The effect of altitude on oxygen solubility will be negligible in Florida. Table 8-3:

Solubility of Oxygen in Water (mg/L) at Sea Level as a Function of Temperature and Salinity (after Stickney, Stickney, 1979) Salinity (ppt)

Temperature (ºC)

0

10

20

30

35

22 24 26 28 30 32 34

8.7 8.4 8.1 7.8 7.6 7.3 7.0

8.2 7.9 7.7 7.4 7.1 6.9 6.7

7.8 7.5 7.2 7.0 6.8 6.5 6.2

7.3 7.1 6.8 6.6 6.4 6.2 6.0

7.1 6.9 6.6 6.4 6.2 6.0 5.8

When the water is 100% saturated with dissolved oxygen, the rate of diffusion of oxygen from the water into the air is exactly balanced by the rate of diffusion of oxygen from the air into the water. Aquatic organisms and bacteria extract oxygen from the water for respiration, respiration, reducing the concentration of dissolved dissolved oxygen in the water. water. Water containing less than the 100% saturation concentration of oxygen is said to be undersaturated with oxygen. The difference between the concentration of dissolved oxygen in the water and the 100% saturation concentration for the existing conditions of temperature, salinity, and atmospheric - 148 -

Chapter 8 – Water Quality Requirements and Management pressure is called the oxygen deficit. The rate of net transfer of air into the water is dependent upon the magnitude of the oxygen deficit. Water can can also become supersaturated (>100%) supersaturated (>100%) with oxygen if air is injected into the water under pressure or from photosynthesis in plants. Bubbling pure oxygen gas into the water can also supersaturate supersaturate the water with respect to oxygen. Supersaturation of water with nitrogen gas from air through pipe leaks may lead to gas bubble disease and shrimp mortality. The two biological factors that affect the D.O. level are respiration and photosynthesis. Respiration removes oxygen from the water, while photosynthesis adds oxygen to the water. The rate of oxygen consumption by respiration is dependent upon water temperature and the total biomass of animals, animals, plants, and aerobic bacteria in the system. system. Accumulation of solid wastes within the system will dramatically increase the biomass of heterotrophic bacteria, resulting in a very large oxygen demand. Careful attention should be paid to to solids removal (see Chapter 4) when designing your system to avoid this problem. Phytoplankton (microalgae) carry out both respiration and photosynthesis. During the day, the rate of oxygen production by photosynthesis generally exceeds the rate of oxygen consumption by the phytoplankton. phytoplankton. At night, photosynthesis does not occur so oxygen levels will decline. In systems with heavy phytoplankton blooms blooms oxygen concentrations fluctuate fluctuate widely on a diurnal basis (Figure 8-1). The oxygen demand of the algae may deplete the oxygen in the culture tank during the early morning hours, especially after a period of warm, overcast days. If the bloom crashes, bacterial decomposition of the dead algae cells will result in a very high oxygen demand. Additional aeration, water exchange, or both may be required to prevent loss of shrimp due to oxygen depletion. 14 Light Bloom

12

Dense Bloom 10 8 6 4 2 0 6 A.M.

12 A.M.

6 P.M.

12 P.M.

6 A.M.

Time of Day

Figure 8-1: Relationship Between Between Algal Density and Diurnal Dissolved Oxygen Oxygen Fluctuations - 149 -


There are several things that can be done to prevent excessive algal growth within the culture system. The most effective method for controlling algal algal growth is to reduce the light levels inside the greenhouse. Covering the outside of the greenhouse with a 90-95% shade cloth will prevent heavy blooms from developing and will also prevent overheating of the greenhouse during summer months. If a heavy bloom does develop in spite of these precautions, then a heavy water exchange may be required to bring the bloom under control. Dissolved oxygen concentrations should be closely monitored. Minimally, dissolved oxygen concentrations should be measured twice a day: once early in the morning (before or soon after sunrise) when oxygen levels are likely to be at their lowest point, and again in the late afternoon when they are likely to be at their highest point. The frequency of monitoring should be increased if D.O. levels drop below 4.0 mg/L. A good dissolved oxygen meter is an essential piece of equipment since oxygen is such a critical water quality parameter. Digital D.O. meters that automatically compensate for altitude, temperature, and salinity salinity work best. D.O. meters should be recalibrated each time they are turned on and between measurements made at different salinities. D.O. meters are calibrated with the probe in the air because the concentration of oxygen in the air is a nonvarying function of altitude and air temperature. Continuous oxygen monitoring and alarm systems are a good investment. Aeration equipment can fail at any time. Rapid detection of these failures may prevent total crop loss. Most problems with dissolved oxygen can be avoided by providing for adequate aeration when designing your production facility. The aeration requirements requirements should be calculated based on the maximum possible shrimp biomass anticipated for each system (see Chapter 4). Remember that oxygen will be consumed consumed not only by the shrimp, but also also by the autotrophic and heterotrophic bacteria and algae living in the culture system. As a rule of thumb, you you will need to transfer at least one kilogram of oxygen to the water for each kilogram of feed 3 that you give to the shrimp. shrimp. At loading rates rates in excess of 4.0 kg shrimp/m shrimp/m (0.033 lbs shrimp/gallon) it will be difficult to maintain dissolved oxygen concentrations above 5.0 mg/liter using airstones airstones and a blower. Pure oxygen should be considered if higher higher loading rates are anticipated. Pure oxygen can be supplied either by an oxygen generator or by a liquid oxygen system.

pH 

(Acceptable range: 7.0-9.0, optimal: 7.4-7.8)

pH is defined as the negative log of the hydrogen ion concentration. Because pH is the negative log of the hydrogen concentration, low pH values indicate high hydrogen ion concentrations, while high pH values indicate low hydrogen ion concentrations. The pH scale ranges ranges from from 0-14. Each pH unit represents a ten-fold ten-fold difference difference in in hydrogen hydrogen ion -7 concentration. Water with a pH of 7 has a hydrogen ion concentration of 10 moles/L, while -8 water with a pH of 8 has a hydrogen ion concentration of 10 moles/L. Aqueous solutions with pH values less than 7.0 are considered to be acidic, while those with pH values greater - 150 -

Chapter 8 – Water Quality Requirements and Management than 7.0 are considered to be basic. A solution with a pH of 7.0 is is considered to be neutral. Freshwater usually has a pH near 7 whereas the pH of seawater is usually near 8.3. Shrimp can tolerate a pH range from from 7.0 to 9.0. Very acidic water (pH less less than 6.5) or very basic water (pH greater than 10.0) is harmful to the gills of the shrimp and growth rates will be suppressed. Although the shrimp are are not harmed by pH values in the range range from 7.0-9.0, in a recirculating culture system it is better to maintain the pH in the range from 7.2 - 7.8. This is due to the relationship between pH and the concentration of ammonia within the culture tank. Most species of nitrifying bacteria are adapted to a pH range of 7.2-7.8 so it is within this range that biofilters function most effectively. effectively. Also, the fraction of total ammonia nitrogen that is in the toxic, unionized form (NH3) is less than 5% when pH is less than 7.8. At a pH of 9.0 approximately 50% of the total ammonia nitrogen is in the form of NH3. The pH of water is strongly influenced by both respiration and photosynthesis. As a result of respiration carbon dioxide (CO2) is released into the water. Dissolved carbon dioxide (CO2) combines with water to form carbonic acid (H2CO3). A series of reversible equilibrium – reactions occur which result in the formation of hydrogen ions, bicarbonate ions (HCO3 ) and = carbonate ions (CO3 ): CO2 + H20 ↔ H2CO3 ↔ H + HCO3 ↔ H+ + CO3 +

–

=

Eq. (8.1)

When carbon dioxide is removed from the water as a result of photosynthesis by aquatic plants, the reactions described described in Equation 8.1 occur in reverse (from right to left). Free hydrogen ions in the water will react with carbonate and bicarbonate ions, reducing the overall hydrogen concentration and raising raising the pH of the water. water. Thus, photosynthesis has the effect of raising pH, while respiration has the effect of lowering pH. In systems with heavy phytoplankton blooms pH fluctuates on a diurnal basis. During the day photosynthesis consumes CO2 causing the pH to rise. In systems systems where phytoplankton blooms are particularly heavy, or which have a low alkalinity, pH may rise above 9.0 in the afternoon. During the night, respiration releases CO2 into the water causing the pH to fall. pH swings of 2 pH units are possible between early morning and late afternoon. pH swings of this magnitude are stressful for both shrimp and the nitrifying bacteria in the biofilter. Wide swings in pH can be minimized by maintaining adequate buffering capacity in the water. Certain compounds, called buffers, are capable of releasing hydrogen ions into the water at high pH levels and withdrawing hydrogen ions from the water at low pH levels. The effect of these buffers is to dampen the fluctuations in pH that would otherwise result from photosynthetic and respiratory processes. Alkalinity is a measure of the buffering capacity of the water (see section on alkalinity for a more detailed discussion). Alkalinity should be maintained above 100 mg/L as CaCO3 to minimize fluctuations in pH. The nitrification process generates hydrogen ions and consumes bicarbonate ion (a source of alkalinity). Over time, time, the net effect is a reduction in alkalinity and pH. The alkalinity consumed by the biofilter should be replaced by the addition of liming compounds or makeup water with a higher alkalinity. a lkalinity.

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Chapter 8 – Water Quality Requirements and Management A variety of techniques may be used to measure pH. The simplest method is is to dip a pH indicator strip in the water and compare the resulting color with the color scale. This method is suitable for quick analyses but is not as accurate as some other methods. Another simple method that is only slightly more accurate, is a colorimetric test in which a few drops of a pH indicator solution are added to a water sample and the resulting color change is matched to a standardized color wheel. When a higher degree of accuracy is desired a pH meter should be used. A pH meter measures the transmission transmission of an electrical electrical current through an aqueous solution using a pair of glass electrodes. The electrical potential measured is related directly to the hydrogen ion activity. pH meters must be calibrated calibrated frequently using buffer solutions of known pH that bracket the pH of the solution solution being measured. Two point calibrations are usually performed using pH 4.01 and 10.0 buffer solutions. The frequency of measurement of system pH is a function of stocking intensity and pH variability. High density systems systems and systems systems with a high degree of pH variability should be monitored daily and occasionally twice a day. The daily measurement should be made at the time of day when the pH is likely to be most critical. critical. In systems with algae blooms, pH should be measured late in the afternoon to determine the maximum daily pH, and occasionally early in the morning to determine minimum daily pH. Usually the maximum maximum daily pH is the more critical measurement because ammonia toxicity is highest when the pH is at its highest point. Ideally, pH and temperature should be measured measured whenever total ammonia nitrogen is measured so that the concentration of unionized ammonia can be calculated.

Dissolved Carbon Dioxide 

(Acceptable: <20 ppm, Optimal <5ppm)

Respiration is the source of most dissolved carbon dioxide (CO2) in the system water. Dissolved carbon dioxide concentrations often bear an inverse relation to dissolved oxygen concentrations. High concentrations of carbon dioxide interfere with the ability of shrimp to extract oxygen from the water, reducing the tolerance of the shrimp to low oxygen conditions. In extreme cases, shrimp shrimp may die from from asphyxiation even when there is adequate oxygen present in the water. The carbon dioxide produced by shrimp respiration must be unloaded across the gills from the shrimp blood to the water. Unloading of CO CO2 at the gills can only take place when the concentration of CO2 in the blood exceeds the concentration of CO2 in the water. High CO2 concentrations in the water cause a buildup of CO2 in the blood of the shrimp. High CO2 levels in the blood lower the blood pH which interferes with the ability of the blood to unload oxygen at the tissues. Carbon dioxide has no detrimental effects on shrimp at concentrations of less than 20 ppm. Concentrations in the range of 2060 ppm are not generally lethal, but do interfere with CO2 exchange across the gills and with the tolerance of shrimp to low low dissolved oxygen conditions. Carbon dioxide concentrations above 60 ppm may be life threatening. Carbon dioxide exerts an important influence on the pH of the water, as discussed in the previous section. In systems systems with with dense phytoplankton blooms carbon dioxide levels decrease during the day and rise during the night. Maintaining a high alkalinity (>100 (>100 mg/L - 152 -

Chapter 8 – Water Quality Requirements and Management as CaCO3) limits the pH shift resulting from the addition of CO2 to the water. In heavily loaded systems the high rate carbon dioxide production can lead to low system pH levels. The most effective way to prevent carbon dioxide levels from becoming dangerously high is to "degas" the excess CO2. Degassing is accomplished by expanding the amount of water surface area that is in direct contact with the air. Aeration of the water with airstones and spraybars will usually provide sufficient degassing to control carbon dioxide levels in shrimp 2 culture systems. systems. However, if very high stocking rates are used (≥ 300 shrimp/m ), a degassing column may be required (see Chapter 4). In an emergency, carbon dioxide may be removed by the addition of quicklime (CaO): CaO + CO2 → CaCO3 ↓

Eq. (8.2)

However, the situation that led to the carbon dioxide level must be corrected or it will reoccur. The quicklime should be added slowly to the water or the the pH may rise too rapidly, stressing the shrimp. shrimp. Quicklime is very caustic, caustic, so care should be exercised when handling this material. Well water is typically low in oxygen and high in carbon dioxide. Untreated well water should not be added directly to to the culture tank. A degassing column is the the most effective way of eliminating excess CO2 and aerating the water. In a degassing column, water is sprayed over a bed of plastic media with a large amount of void space and air from a fan or blower is introduced at the bottom of the column. The idea is to create a very high air:water ratio to maximize the the rate of diffusion of gases between the air and the water. Alternatively, heavy aeration or spraying of the water into the air may be sufficient to aerate the water and drive off the CO2.

Ammonia 

(Optimal: unionized form <0.03 ppm, chronic effects/lethality >0.1 ppm)

Ammonia is the principle nitrogenous waste-product excreted by shrimp and most other aquatic organisms. Much of the nitrogen from from protein in the feed that is added to a culture culture tank is converted into ammonia. Most of the feed that is is ingested by the shrimp shrimp is assimilated and the proteins are metabolized by the shrimp. Ammonia, a major by-product of protein metabolism, is excreted across the gills of the shrimp. Heterotrophic bacteria utilize uneaten feed, fecal wastes or other decaying organic material as a protein source and convert the protein nitrogen into inorganic ammonia, which is excreted. This process, in which organic nitrogen from proteins is converted into inorganic nitrogen (NH3), is called mineralization. Nearly 85% of the nitrogen in the feed fed to shrimp in the culture tanks will end up as ammonia. Ammonia levels in the culture tank must be carefully managed because ammonia can be highly toxic to the shrimp. Ammonia exists in two different forms forms in the water: as unionized + ammonia (NH3) and as ammonium ions (NH4 ). These two forms are usually present

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Chapter 8 – Water Quality Requirements and Management simultaneously in the water and are transformed from one form to another in an equilibrium reaction: NH3 + H20

↔ NH4+ + OH-

Eq. (8.3)

Only the unionized form of ammonia is toxic to the shrimp. The toxicity of ammonia is is partly a function of shrimp age. Postlarvae and small juveniles are are are less tolerant of high concentrations of unionized ammonia levels than are larger juveniles and adult. The 96-hr LC50 concentration of unionized ammonia is about 0.2 ppm for postlarvae (Chen and Chin, 1988) and about 0.95 ppm for 4.87 gram adolescents (Chen and Lei, 1990). Shrimp health and growth rates are not affected when unionized ammonia levels are maintained below 0.03 ppm. However, chronic exposure to elevated sublethal sublethal concentrations may have a number of detrimental effects on the shrimp. shrimp. Growth rates decrease and feed feed conversion rates increase. High ammonia concentrations irritate the gills of the shrimp and may lead to gill hyperplasia (i.e., swollen gill filaments) reducing the ability of the shrimp to extract oxygen from the water. In additon, high ammonia levels in the water lead lead to an increase in the ammonia concentrations in the blood. High ammonia concentrations in the blood reduce the affinity of the blood pigment (hemocyanin) for oxygen. Together, these latter two effects reduce the the tolerance of the shrimp to low oxygen conditions. conditions. Chronic exposure to high ammonia concentrations may also reduce the resistance of the shrimp to disease. Ammonia is usually measured measured as total ammonia nitrogen nitrogen (TAN). TAN is a measure of the combined concentrations of unionized ammonia and ammonium ion. The fraction of TAN that is in the unionized form is a positive function of both pH and temperature (Table 8-4). The relationship between the unionized fraction of ammonia and temperature is nearly linear, while the relationship with with pH is logarithmic. The fraction of unionized ammonia at 30ºC at pH values of 7.0, 8.0, and 9.0 increases from 0.008 to 0.075 to 0.449, respectively (Table 84). This illustrates illustrates the importance of maintaining system system pH below 8.0. This example also Table 8-4: Proportion of Total Ammonia Nitrogen in the Unionized Form as a Function of Temperature and pH pH 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 9.2 9.4 9.6 10.0

Temperature 24

26

28

30

32

0.005 0.008 0.013 0.021 0.033 0.051 0.078 0.119 0.176 0.253 0.349 0.460 0.574 0.681 0.843

0.006 0.010 0.015 0.024 0.038 0.058 0.089 0.134 0.197 0.281 0.382 0.495 0.608 0.711 0.861

0.007 0.011 0.018 0.028 0.043 0.066 0.101 0.151 0.220 0.309 0.415 0.530 0.641 0.739 0.877

0.008 0.013 0.020 0.031 0.049 0.075 0.114 0.170 0.245 0.340 0.449 0.564 0.672 0.764 0.891

0.009 0.015 0.023 0.036 0.056 0.085 0.129 0.190 0.271 0.371 0.483 0.597 0.701 0.788 0.903

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Chapter 8 – Water Quality Requirements and Management illustrates the importance of measuring pH and temperature whenever TAN is measured. Without these values, the concentration of unionized ammonia cannot be calculated. The following example explains how unionized ammonia is calculated from measurements of TAN, pH, and temperature. Example: You determine that the total ammonia nitrogen (TAN) in your system is 0.8 ppm. o The temperature is 28 C and the pH is 7.6. What is the unionized ammonia concentration? o On the table locate the column for 28 C and the row for pH of 7.6. Where these two cross is the number 0.028. This number will be multiplied by your TAN (0.028 x 0.8 ppm) to yield yield the unionized ammonia concentration (= 0.0224 ppm). This level is lower than the acceptable level (<0.03 ppm) and no corrective action would need to be taken. taken. However, if the pH of the system were only 0.2 units higher (i.e., at 7.8) then the unionized ammonia level would be 0.0344 and corrective measures may have to be taken.

Almost all ammonia testing methods yield the total ammonia ammonia nitrogen level. There are two different analytical procedures that are commonly used to test for ammonia. The salicylate method can be used for both fresh and saltwater samples. samples. The Nessler method works best with freshwater samples, samples, but the procedure can be modified modified for saltwater use. Nevertheless, we prefer the salicylate method because it is accurate and the exact same procedure is used for both fresh and saltwater. There are three basic mechanisms by which ammonia can be removed from a recirculation system: water exchange, plant uptake, and nitrification. Water exchange is an effective way to lower ammonia levels rapidly in an emergency, but should not be counted on as the primary strategy strategy for controlling controlling ammonia levels. For water exchange to be effective, effective, 50100% of the water would need to be exchanged per day. Such a high volume of effluent would require enormous effluent treatment systems. systems. However, when primary primary ammonia removal systems fail, heavy water exchange may be the only way to save the shrimp. Phytoplankton and other aquatic plants remove ammonia from the water and use it as a nitrogen source for protein synthesis. synthesis. Systems with with high exposure to sunlight will will develop dense blooms of phytoplankton. As long as the the phytoplankton population is increasing, the phytoplankton will constitute an effective nitrogen sink. sink. However, if the bloom crashes, a large amount of the nitrogen tied up in the phytoplankton will be converted back into ammonia as the the dead algae cells are decomposed by heterotrophic bacteria. Dangerously high ammonia levels typically typically follow follow crashes of phytoplankton blooms. Algal blooms can be controlled by water exchange to prevent "overblooms" from developing. Some recirculating systems systems depend upon aquatic macrophytes to control ammonia. In these systems water from the culture tank is recirculated through a separate water treatment tank or pond containing a large number macrophytes such as water hyacinths, water lilies, bullrushes, etc. Ammonia is removed removed by the macrophytes macrophytes and water low low in ammonia is returned to the culture tank. Hydroponic systems are sometimes combined with aquaculture systems. In these systems systems the the roots of vegetables or herbs absorb ammonia and other nutrients from the water coming from the aquaculture system.

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Chapter 8 – Water Quality Requirements and Management The more traditional approach to ammonia control in recirculating systems is to promote the process of nitrification within a biofilter. Nitrification is the sequential oxidation of ammonium ion to nitrite and then to nitrate by autotrophic bacteria. Nitrosomonas spp. convert ammonium ions to nitrite, while Nitrobacter spp. convert nitrite to nitrate. In addition to oxygen, the nitrifying bacteria require bicarbonate ions, which they utilize as a carbon source for cell growth. The nitrification process is represented by the following equations (EPA, 1975):

+ 55NH4

+ 76O2 +

itrosomonas – – 109HCO3 54NO2 +

→

57H2O + 104H2CO3 + C5H7 NO2

Eq. (8.4)

Nitrobacter – 400NO2 +

+ NH4

+ O2 + 4H2CO3 +

– HCO3 +

195O2 →

=

400NO3 + 3 H2O + C5H7 NO2 Eq. (8.5)

A biofilter is simply a device that provides a large amount of surface area for the nitrifying bacteria to grow (see Chapter 4 for a more complete discussion of biofilter design and operation). When a new system is is started up, the biofilter biofilter will not be active. active. Before stocking animals into the system, system, the biofilter will will need to be conditioned. During the conditioning period an inorganic source of ammonia, such as ammonium chloride, is added to the system. The rate of addition of inorganic ammonia should equal or exceed the rate at which ammonia will be generated by the quantity of feed that the animals receive on a daily basis immediately after they they are stocked. A source of inorganic nitrite, nitrite, such as sodium nitrite, can also be added to the system water to accelerate the conditioning process, but the Nitrobacter the Nitrobacter

NH3-N

NO3-N NO2-N

0

5

10

15

20

25

30

35

Days Figure 8-2 : Changes in Concentration of Total Ammonia (NH3-N ), Nitrite (NO2-N) and Nitrate over (NO3-N) Time During During the Conditioning of a Biofilter. Biofilter. - 156 -

Chapter 8 – Water Quality Requirements and Management bacteria will colonize the biofilter biofilter even without the addition of nitrite. What is typically seen during the conditioning period (Figure 8-2) is a gradual decline in the ammonia concentration as the Nitrosomonas population becomes established. As the ammonia concentration falls, the nitrite concentration concentration rises. The nitrite levels will peak and then then begin to fall as the Nitrobacter population becomes established. The biofilter conditioning is complete when both ammonia and nitrite levels can be maintained within acceptable limits even with daily ammonia input equal to the amount that will be produced at the initial feeding rates. Even with well-established biofilters, high ammonia levels may occasionally develop in a culture tank. When this occurs, the the cause of the problem must be quickly determined determined and an appropriate response must be decided upon. While water exchange may provide immediate relief from high ammonia conditions, corrective measures should be taken that address the cause of the problem. Otherwise, ammonia levels will quickly return to high levels. There are a number of reasons why the ammonia concentrations may be high. Chronic overfeeding may lead to a buildup of uneaten feed in the culture tank and in sumps and filters. filters. In addition to causing high ammonia levels, decomposing decomposing feed in a tank can serve as a substrate for Vibrio for Vibrio bacteria. bacteria. These bacteria may infect and kill shrimp, especially if high ammonia levels have weakened the disease resistance resistance of the shrimp. If accumulations of uneaten feed are observed in the tank, feeding rates should be reduced and excess feed should be siphoned or vacuumed from from the culture tank. If the shrimp shrimp are very small small it may not be possible to siphon out the feed without siphoning up some shrimp. An alternative way of removing the accumulated solid wastes is to increase the flow rate through the tank and brush the bottom of the tank to suspend the solid wastes so that they will be carried in the flow to the drain. This may need to be done several times. Accumulated solid wastes in sumps may also be source of ammonia production and biological oxygen demand (BOD). Sumps should be siphoned or flushed out to remove these accumulations. High ammonia levels may be indicative of a problem with the biofilter. The effectiveness of the biofilter can be determined determined by measuring measuring the efficiency of the biofilter. Biofilter efficiency is a measure of the percentage of ammonia (or nitrite) removed by the biofilter in a single pass: Biofilter Efficiency

=

T.A.N. in – T.A.N. T.A.N. out   T.A.N. x 100%   T.A.N. in

Eq. (8.6)

Biofilter efficiency should be monitored on a regular basis (at least weekly) so that changes in efficiency can be detected. Historical data allows changes in biofilter nitrification nitrification rates to be detected. A number of conditions must be present for a biofilter to provide reliable ammonia and nitrite control: The water should be filtered to remove the majority of suspended solids before it enters the biofilter. Solid wastes will will smother the autotrophic bacteria and provide a substrate for heterotrophic bacteria which will compete for space and oxygen. 2. The oxygen level within the biofilter should be maintained above 2 ppm. 1.

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Chapter 8 – Water Quality Requirements and Management 3.

4. 5. 6. 7.

The alkalinity of the water should be maintained above 100 ppm to minimize pH fluctuations and to provide a source of bicarbonate ions for the nitrifying bacteria. Stable temperatures should be maintained, ideally between 28ºC and 32ºC. Salinity should be kept as stable as possible. Adequate shearing forces should be present within the biofilter to slough off accumulations of dead bacteria and other organic material. Avoid exposing a biofilter to antibiotics or other po tentially toxic chemicals.

If biofilter efficiency has declined, the reason for the decline must be determined and the problem must be corrected. Even after the condition causing a decline in nitrification rates has been corrected, it may take awhile for the population of nitrifying nitrifying bacteria to recover. In the meantime it may be necessary to reduce feeding rates and increase the rate of water exchange. If unionized ammonia levels are dangerously high, it may be necessary to reduce the pH of the system by adding muriatic acid. This will reduce the the percentage of the total ammonia in the toxic unionized form. Acid should be added very slowly to the system to avoid causing a pH shock to the shrimp or the biofilter bacteria. This would only make the problem worse.

Nitrite 

(Acceptable: <1 ppm)

Nitrite is a product of the first step of nitrification, in which ammonium ion is oxidized by Nitrosomonas bacteria to form nitrite. Nitrite can accumulate in the system if the second step in the nitrification process, in which nitrite is oxidized by Nitrobacter bacteria to form nitrate, occurs at a much slower rate than the first nitrification step. Nitrite is is toxic to penaeid shrimp. The toxicity of nitrite nitrite is influenced by shrimp shrimp age and the salinity of the water. The 96-hour LC50 concentration of nitrite nitrite to Penaeus monodon postlarvae was reported by Chen and Chin (1988) to be 13.6 ppm. The 96-hour LC50 for adolescent P. adolescent P. monodon (5 grams) was reported by Chen and Lei (1990) to be 171 ppm. The LC50 P. monodon. monodon. At concentration for adolescent L. adolescent L. vannamei appears to be much lower than for P. Harbor Branch we have observed mortalities approaching 50% in tanks stocked with 10 gram L. vannamei at nitrite nitrite concentrations less than 20 mg/L. mg/L. Nitrite is more toxic at low salinities and low pH values than it is at higher values. To be safe, nitrite concentrations should be maintained below 1 mg/L. In fish, nitrite nitrite in the blood binds with hemoglobin to to form methemoglobin. Methemoglobin is unable to transport oxygen to the tissues so fish die from asphyxiation. If chloride concentrations in the water are at least six times the concentration of nitrite, then nitrite is not transported across the gill membranes and the toxic effects of nitrite are avoided. The mechanism of nitrite toxicity is not well understood in shrimp, which have a different blood pigment (hemocyanin) than fish. The mechanism may be similar, similar, since high nitrite nitrite levels reduce the tolerance of shrimp to low oxygen levels. Although a high chloride concentration provides some protection against nitrite toxicity it does not provide complete protection.

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Chapter 8 – Water Quality Requirements and Management A well-conditioned biofilter with adequate surface area is the best protection against high nitrite levels. Before stocking a new system, system, make sure that the nitrite peak has passed (see above). Some types of biofilters do not seem to support good populations of Nitrobacter and Nitrobacter and nitrite levels will tend to run high. This is especially true of bead filters filters and some submerged, moving bed biofilters. Compared to Nitosomonas, Nitosomonas, Nitrobacter is not very "sticky". When the biofilter media media is agitated, Nitrobacter agitated, Nitrobacter are are dislodged and washed out of the filter. Bead filter manufacturers manufacturers are addressing addressing this problem by using media with with recesses to protect the bacteria. Nevertheless, frequent backwashing reduces the Nitrobacter the Nitrobacter population significantly. Reducing the frequency of backwashing can help minimize this problem. Whenever high nitrite levels are encountered, the cause of the problem must be determined. Often the causes of high nitrite levels are the same as the causes of high ammonia levels (see above). Often the two problems occur simultaneously. Water exchange and reduced feeding feeding rates can provide short term relief, but unless the root causes are remedied the problems will return.

Nitrate 

(Acceptable: <60 ppm)

The biofilter contains another nitrifying bacteria, Nitrobacter, bacteria, Nitrobacter, that oxidizes nitrite to nitrate (NO3). Nitrate is virtually non-toxic. Shrimp can survive nitrate levels as high as 200 ppm, but it is not known if levels this high affect growth or disease resistance. Ideally nitrate levels should be maintained maintained less than 60 ppm. In general, your system system should be balanced in that nitrate levels may increase over the course of grow-out but not to a point that should cause worry. Although most biofilters are oxidative reactors, there are portions of the biofilter and elsewhere in a system where oxygen levels are virtually zero and anaerobic bacteria thrive. Anaerobic bacteria utilize nitrate and convert it to nitrogen gas (N2) in a process known as denitrification. During this reaction, nitrite nitrite may also be formed. formed.

Hardness 

(Acceptable: >150 ppm as CaCO3)

Hardness is the measurement of all divalent cations (i.e., those ions carrying a plus two ++ ++ charge) of which calcium and magnesium (Ca , Mg ) are the predominant species in water. These two ions may be absorbed by shrimp through their gills and thus are important not only in water quality but in the nutrition of the animal. Hardness is generally measured by titration, although color strip indicators are available, and is expressed in terms of mg/L as calcium carbonate. This expression helps in equalizing different water compositions (e.g., one with only calcium) calcium) for comparisons. Therefore, "total" hardness does not divulge the ionic makeup of the hardness. For that, calcium hardness may be determined determined and the difference assumed to be magnesium, although the only way to verify that would be through expensive analytical chemistry procedures.

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Chapter 8 – Water Quality Requirements and Management You may be familiar with hardness since many water sources have to be treated to reduce hardness so as not to build up scale scale in pipes and boilers. Water with a total hardness of 0-75 ppm is considered soft, 75-150 is moderately hard, 150-300 is hard and greater than 300 is very hard. Seawater, in which shrimp shrimp normally grow, has a total hardness of approximately 6600. Yet, marine shrimp can be grown in water with moderate hardness (150) and may be able to be grown in waters with even lower hardness levels, although no research has been done to verify the possibility. Hardness is often confused with alkalinity (describe later) because both are expressed in similar terms (mg/L as CaCO3) and often hardness and alkalinity values are similar. However, if the alkalinity is from sodium carbonate instead of calcium or magnesium carbonates it is possible to have low hardness and high alkalinity. alkalinity. High hardness and low alkalinity may occur in acidic well or surface waters. Low hardness can be increased with agricultural limestone (calcium carbonate), agricultural gypsum (calcium sulfate), or food grade calcium or magnesium chloride.

Alkalinity 

(Acceptable: >100 ppm as CaCO3)

Alkalinity is defined as the sum of exchangeable bases reacting to neutralize acid when an acid is added to water. In other words, alkalinity is the buffering capacity of water. This - buffering capacity is primarily due to bicarbonates (HCO3 ), carbonates (CO3 ), hydroxides (OH ) or a mixture of these. As mentioned earlier in the the section on pH, sufficient alkalinity will help moderate pH swings from photosynthesis and respiration. Since little water is exchanged in most high-density shrimp recirculating systems, alkalinity should be maintained at relatively high levels (>100 ppm). Seawater has an average alkalinity of 116 ppm (as CaCO3 ) and alkalinities in freshwater fish ponds typically average about 40 ppm. Alkalinity in freshwater can range from 20-300 ppm as CaCO3. Alkalinity can also be expressed as milliequivalents (1 meq/L = 50 ppm as CaCO3 = 2.92 grain/gallon CaCO3). As with hardness, alkalinity may be increased with agricultural agricultural limestone (calcium carbonate). Sodium bicarbonate may be used to increase alkalinity without increasing hardness.

Hydrogen Sulfide 

(Acceptable: None)

Hydrogen sulfide (H2S) is a colorless, toxic gas with a distinctive odor similar to rotten eggs. It is primarily primarily derived from anaerobic decomposition of organic matter. It may be found in well water or in pond bottoms composed of mud and other organic matter. Hydrogen sulfide is highly toxic in the unionized form (similar to ammonia), however, the unionized form is predominant at low pH (<8) and high temperature. At pH 7.5 approximately 14% of the sulfide is in the toxic H2S form, at 7.2 about 24%, at pH 6.5 about 61%, and at pH 6 about 83% of total sulfide is in the toxic unionized form. form. Therefore, sulfide concentrations should - 160 -

Chapter 8 – Water Quality Requirements and Management be less than 0.002 ppm. If you can smell it, then there is too too much present and it will will slow growth and eventually kill most of your shrimp. shrimp. Well water that contains hydrogen sulfide must be vigorously aerated ("degassed") before use. There are a number of kits available to test for hydrogen sulfide in your water.

Iron 

(Acceptable: <1.0 ppm, none preferred) ++

+++

Iron is found in two forms, soluble (ferrous, Fe ) and insoluble (ferric, Fe ) in well water. Iron in and of itself is not toxic, but the oxidation of the soluble form to the insoluble leads to the formation of precipitates that can irritate and clog the gills of shrimp, ultimately leading to a reduced oxygen supply, asphyxiation asphyxiation and death. Soluble iron can be removed from water by aeration and letting it oxidize to form a precipitate that can be removed by filtration or settling before use in your system.

Chlorine 

(Acceptable: None)

A common mistake in talking about chloride is the use of the word chlorine. chlorine. Chlorine and chloride are two forms of elemental chloride, however, their effect on the health of your shrimp is totally opposite. Chlorine is used for disinfection of systems and is toxic at extremely low levels (<0.05 mg/L). Municipal water sources contain at least 10-fold higher levels if not higher (0.5 - 2.0 mg/L). The addition of untreated municipal water to your system or the accidental introduction of chlorine into your system can have devastating results. Chlorine can be removed by using sodium sodium thiosulfate at a rate of 7 mg/L for each 1 mg/L of chlorine. Chloride is the ion discussed at the beginning of this section that is the predominant ion in the composition of salinity and functions in osmoregulation.

Selected Literature Ammonia by Ruth Francis-Floyd Francis-Floyd and Craig Watson. IFAS Fact Sheet FA-16 by IFAS, University of Florida, Gainesville, Florida, 4 pp. Aquaculture Engineering by Frederick Frederick W. Wheaton. 1977. John Wiley Wiley & Sons, Inc., New York, NY, 693 pp. Crustacean Farming Farming by Daniel O'C. Lee and John F. Wickins. Wickins. 1992. Halsted Press Press of John Wiley & Sons, Inc., New York, NY, 392 pp. Fundamentals of Aquaculture by James W. W. Avault, Jr. 1996. AVA Publishing Publishing Co., Baton Rouge, Louisiana, 889 pp. - 161 -


Interactions of pH, Carbon Dioxide, Alkalinity and Hardness in Fish Ponds by William A. Wurts and Robert M. Durborow. 1992. SRAC Publ. No. 464, Southern Regional Aquaculture Center, IFAS, University of Florida, Gainesville, Florida, 4 pp. Joint Action of Ammonia and Nitrite on Tiger Prawn Penaeus Prawn Penaeus monodon Postlarvae by JiannChu Chen and Tzong-Shean Chin. 1988. Journal of the World Aquaculture Society 19: 143-148. Marine Shrimp Culture: Principles and Practices Practices by Arlo W. Fast and L. James Lester. Lester. 1992. Elsevier Science Publ. Co., Inc., New York, NY, 862 pp. Practical Manual for Semi-intensive Commercial Production of Marine Shrimp by Jose R. Villalon. 1991. TAMU-SG-91-501 by Texas A&M University University Sea Grant College Program, Program, Texas A&M University, College Station, Texas, 104 pp. Principles of Warmwater Warmwater Aquaculture by Robert R. Stickney. Stickney. 1979. John Wiley and Sons, Sons, Inc., New York, NY, 375 pp. Toxicity of Ammonia and Nitrite to to Penaeus monodon Juveniles. by Jiann-Chu Chen and Shun-Chiang Lei. 1990. Journal of the World Aquaculture Society Society 21: 300-306. Understanding and Interpreting Water Quality by Michael McGee. IFAS Fact Sheet Sheet FA-2 by IFAS, University of Florida, Gainesville, Florida, 4 p p. Water Quality in Ponds Ponds for Aquaculture by Claude E. Boyd. 1990. Auburn University, University, Auburn, Alabama, 482 pp.

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Chapter 9 – Shrimp Health Management

Chapter 9 Shrimp Health Management by Kevan L. Main and Rolland Laramore Harbor Branch Oceanographic Institution

Introduction One of the most important criteria for a successful operation is to insure that the health of the shrimp is maintained. The goal of this chapter is to provide an overview of the shrimp health issues that farmers farmers will encounter during the nursery and growout culture phases. We will highlight some of the stress producing factors that promote disease in shrimp, discuss the more common disease symptoms, and explain how to evaluate the health of your shrimp. We will not discuss broodstock or larval health issues. In addition, we will not address the issues that affect traditional pond culture in saltwater systems. Those topics are already addressed in other publications on shrimp diseases (Brock and Main 1994; Fulks and Main 1992; Lightner 1988, 1993, 1996; Wyban and Sweeney 1991). Disease and production problems vary during the different phases of shrimp culture. Production shortages resulting from shrimp mortality, slow growth and high food conversion ratios occur and affect the economics of L. L. vannamei farms. Substantial losses have occurred in some farming areas due to diseases, such as Taura syndrome virus, runt-deformity syndrome, vibriosis and necrotizing hepatopancreatitis. Effective strategies to control the occurrence and spread of disease are primarily related to proper management of the production system. When shrimp are cultured in a poorly managed environment, both growth and survival rates will decrease. This is true whether farming is conducted in extensively stocked saline ponds or in intensively stocked freshwater raceways. However, as stocking densities are intensified and the animals are moved into a controlled production environment, there is a greater need to reduce stress factors. factors. To insure that the animals are under a limited amount of stress, it is necessary to establish and implement good management practices. Seasonal changes are also known to influence shrimp health and disease problems are often associated with the high summer temperatures. This chapter is intended for field use by culturists, farmers, students and extension personnel who are not formally trained in microbiology or veterinary medicine. The information presented in this chapter is drawn from a number of sources, but the primary resource was Brock and Main (1994).

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Variables to Consider in Determining the Health of Your Shrimp Farmers commonly consider a number of variables when they evaluate the health of the shrimp in the the culture system. These variables include survival rate, mortality rate, growth rate, size variation, food conversion ratio and appearance of the shrimp (Brock and Main, 1994). Survival Rates

The survival rate is an estimate estimate of the change in number of shrimp in a tank over a period of time. The validity of a survival rate value depends on the accuracy of the data. Mistakes may result from inappropriate counting techniques, human error or inexperience and variability in the counting method. Often the shrimp shrimp are miscounted when they are first added to the tank - this can lead to survival rates that exceed 100%. Mortality Rates

Mortality rate is the number of dead shrimp that are counted over a period of time. Daily, weekly or monthly counts of dead shrimp can be used to show trends in disease progression, transmission, response to treatment or other management manipulations. Occasionally survival rates are the opposite of mortality rates in shrimp production. However, you cannot assume this is the case because reduced survival does not always mean the shrimp have died. Escapement, predation, miscounting and theft theft can also result in lower survival. Growth Rates

Growth rates are a good indicator of the health of the shrimp in in your system. Growth rates are influenced by environmental, genetic, biological and nutritional factors. Water temperature is a major factor that affects growth rates and will affect weekly gains during warmer and cooler months of the year. During the first month month of growout, growth rates can th be measured as the percent increase in in body weight. By the 6 week in growout, weekly weight gains are estimated estimated to determine the growth rates. Growth rates in L. in L. vannamei can vary from 0-2.5 grams per week. Growth rates that are less than of < 0.5 grams per week are considered to be a poor rate of growth. Size Variation

Some disease or health problems can be identified by looking at the size distribution of shrimp in a raceway system. The size distribution of the shrimp does not need to be determined unless you see that there is a problem with growth rates rates or mortality. For routine management of healthy shrimp, we do not recommend calculating size variations for the shrimp in the production system. Feed Conversion Ratio

The feed conversion ratio (FCR) is a measure of the efficiency of feed utilization by shrimp. FCR values, together with other information, can be used to understand a problem with a production run. In general, the lower the FCR, the more efficient the feed utilization. Poor - 164 -

Chapter 9 – Shrimp Health Management feed quality can reduce reduce growth and increase FCR. Experimental growth trials trials can indicate if the reduced growth rate is diet related (Brock 1992). Appearance of Shrimp

Shrimp should be visually visually examined on a daily basis for changes in behavior and color. In order to identify problems, you must first be able to recognize normal appearance and vannamei. Unusual behaviors (i.e., lethargy, disorientation) can be behavior of cultured cultured L. vannamei. indications of a disease problem. Changes in appearance and color of organs (i.e., (i.e., gills, appendages, cuticle, abdominal muscle) should also be noted.

The Effect of the Environment on Shrimp Health The environment can have a significant significant impact on shrimp health, growth and production. A change in one environmental parameter can affect the other variables. It is important to look at the direction, rate and amount of change in evaluating the impact of environmental conditions on shrimp health. The types of environmental variables that have been associated with shrimp disease include temperature extremes, pH extremes, low dissolved oxygen, abrupt changes in salinity and gas supersaturation. Some environmental parameters are associated with a site (i.e., water chemistry parameters), while others are associated with management management and production strategies. strategies. Both site selection and the levels of specific environmental are important factors in determining the success or failure of an operation. The levels of specific environmental parameters are often associated with changes in behavior and eventually growth and survival.

Health Evaluation Tests Stress Tests Stress tests are widely used by shrimp farmers as a quality control measure for postlarval L. postlarval L. vannamei. vannamei. The survival of a shrimp shrimp sample following a thermal or pH shock is used to assess population health, with survival after a defined time period used as a measure of postlarval quality. Gill Examination

The physical condition or structural integrity of the gill provides an indirect assessment of the functional status of the respiratory system of the shrimp. Gill exams do not require sophisticated laboratory equipment equipment beyond glass slides and a microscope. The methods are described in Brock and Main (1994). Gut Content Examination

Gut content exams are only done when a growth or survival survival problem is encountered. This evaluation can be done by an assessment of the relative degree of fullness of the abdominal intestine. Healthy shrimp feed feed continuously, so their gut contents should be relatively full, full, unless a suitable feed is not available or there is a health problem.

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Detecting Diseases and Diagnostic Techniques There are a variety of different diagnostic tests that are used to identify shrimp diseases. Examples of the diagnostic tests used for shrimp diseases include visual examination, microscopic and histological examination, tissue culture and serum neutralization, specific gene probes (DNA probes), ELISA (Enzyme Linked Imunosorbent Assay) and PCR (Polymerase Chain Reaction). Visual and microscopic examinations can often be done by the farm manager; however, the majority of these diagnostic techniques need to be done by a shrimp health professional or veterinarian.

Factors Leading to Losses and Disease Outbreaks During Growout The factors leading to losses and disease outbreaks include poor quality postlarvae, postlarval acclimation procedures, management strategies, human factors and environmental factors. Poor Quality Postlarvae

Farmers may have problems with weak or dying postlarvae when they are received at the farm. This can happen because the postlarvae were either incubating a disease before shipment or they were in a weakened condition prior to shipment. You can also see these problems when the larvae are exposed to damaging or toxic conditions during packing and transport. When there is a problem with poor quality postlarvae, the PLs should be examined using a microscope to determine the prevalence and severity of bacterial fouling, the prevalence of larval vibriosis and black spot disease, the hepatopancreas lipid level and gut-to-muscle ratio, the prevalence and severity of BP infection, and the prevalence of postlarvae with missing appendages or body parts, parts, abdomen or appendage deformities. In addition to the microscopic evaluation, the larvae should be exposed to a stress test to assess the quality of the postlarvae. If disease symptoms are not present, the postlarvae may have been exposed to unsuitable environmental conditions. Selected physical and chemical water quality analyses (e.g., (e.g., temperature, dissolved oxygen, total ammonia, pH, nitrite and carbon dioxide) should be measured and recorded on the water in five or ten shipment bags. Postlarval Acclimation Procedures

Poor postlarval performance can also result when the shrimp are exposed to inappropriate conditions during acclimation. You need to be sure and slowly acclimate the the animals to the new environment in order to avoid stressing stressing the animals (see Chapter 6). A careful review of the acclimation procedures and monitoring records is needed and appropriate corrective actions must be taken. Management Strategies that Lead to Disease Problems

Management strategies can also lead to disease problems. problems. Overstocking or excessive densities can stress the animals and make them more susceptible to disease. High densities can also lead to injuries that develop into bacterial infections. In recirculating systems, systems, the - 166 -

Chapter 9 – Shrimp Health Management biofilter has to adequately filter out the ammonia that is being produced by the shrimp. When shrimp biomass exceeds the capacity of the biofilter, you will see a buildup in nitrite levels, which are highly toxic to to the shrimp. Overfeeding can result in a heavy accumulation of organic detritus and hydrogen sulfide in the culture system, which can become toxic to the shrimp. Underfeeding will result result in a considerable size size variation in the shrimp population in a raceway. Dietary Issues

Several shrimp diseases are known to be caused by nutritional nutritional deficiencies. In recirculating raceway systems, it is critical to provide a nutritionally complete feed because there are no other organisms living in the system system for the shrimp to consume. When there is a nutritional problem, it will likely result in a decrease in growth of all the shrimp in the system at once. Dietary deficiencies can also result in abnormal pigmentation, subcutical melanized lesions that are symmetrically distributed, muscle cramp, chronic soft cuticle, and slow growth in spite of a good appetite and weakness (Brock and Main 1994). Human Factors

Well-trained personnel are a critical element to the successful operation of a shrimp farm. The number of individuals employed on a farm varies depending on economic factors, farm size and production intensity. intensity. Worker failure to perform tasks according to directions or accidental errors can result in decreased shrimp production, animal mortality and disease outbreaks (Brock (Brock 1996). Employee training workshops and feedback discussions about improving procedures and the importance of daily tasks, are potentially effective means of reducing worker-related production losses. Environmental Factors

Changes in environmental conditions during growout will be detected by routine water quality analyses. The likely candidates are low dissolved oxygen during the night and elevated pH during the late afternoon. Low temperatures can stop or slow growth for extended periods of time.

Factors to Consider in Disease Prevention The factors that need to be considered in preventing diseases in shrimp farming include site selection and environmental condition, feed quality, biosecurity in relation to the source of seedstock, probiotics, transfer and handling procedures, accurate record keeping and training of personnel. Site Selection & Environmental Conditions

Site selection is one of the most important factors in determining the success or failure of an operation. Suitable environmental conditions must be considered as a part of site selection. Information on temperature range and suitable levels of various water chemistry parameters (see Chapter 8) need to be evaluated.

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Chapter 9 – Shrimp Health Management Feed Quality

A consistent source of high-quality feeds is needed to insure the shrimp health (see Chapter 7). Unfortunately, problems with feed ingredients are usually difficult difficult to diagnose because of complicating infectious diseases or differences in densities or biomass loading within and between raceways or ponds. These differences may mask a problem with with the feed. Feeds that are old or improperly stored can cause disease problems and may also have decreased levels of the essential lipid or water-soluble wa ter-soluble vitamins. Biosecurity

Maintaining biosecurity and preventing introduction of disease is the goal of all farm managers. Biosecurity can be defined defined as procedures that protect shrimp from contracting, carrying and spreading diseases and other health problems (Moss (Moss et. al. 1998). The best way to prevent introduction of disease is to obtain your seedstock from a supplier that has specific pathogen free (SPF) or high-health seedstock. When you bring in a group of postlarvae from a new source, those stocks should be quarantined and tested for pathogens at time of purchase or stocking. Employees must wash their hands before work if they have handled shrimp from another source. Something as simple as handling a box that contains frozen frozen shrimp in a grocery store can result in the transfer of viruses from the frozen product to the shrimp on your farm. Human traffic can spread disease from one farm to another (Moss et. al 1998). If you visit another farm, be sure to shower and change clothing and shoes before coming to work. Probiotics

In aquaculture, probiotics is a term used to signify the addition of live, beneficial bacteria to the water or feed used in the cultivation of aquatic animals. Studies conducted using fish, oysters and shrimp have added to a growing body of evidence that the use of probiotics in hatchery and growout facilities is beneficial in helping to maintain a healthy environment (Browdy 1998; Moriarty 1998). In some instances, culture conditions have been adjusted to encourage the growth of fermenting bacteria, to the detriment of the nonfermenting bacteria. Shrimp culturists have added sugar or molasses to the water to promote the growth of fermenting Vibrio sp. over the more pathogenic nonfermenting species. Several commercial probiotic products are currently marketed for use to treat the culture water prior to and during stocking and cultivation of fish and shrimp. Most of these preparations are stabilized forms of various strains of Bacillus subtilus. Trials conducted at HBOI have suggested that probiotics can reduce bacterial septicemia in raceway cultures of shrimp. Inoculums of one million to one hundred million million cells per milliliter of water have been recommended. The lower number may be used to inoculate newly stocked systems, whereas higher numbers are needed for the probiotic bacterium to gain dominance over older systems that have developed heterotrophic bacterial populations. It is recommended that the water be reinoculated every two to three weeks to maintain the desired bacterial population. - 168 -


Aside from their roll in displacing pathogenic bacteria, probiotic bacteria produce high levels of proteolytic enzymes that are useful in reducing the organic loading of the water introduced by the feed and fecal mater. This can reduce the loading of the biofiltration system. Transfers and Handling

Care must be taken during transfer and handling of shrimp to avoid stressing the shrimp and lowering their resistance to disease. In a multi-phase production system, system, the shrimp must be transferred from one section of the raceway to another several times during the growout period. To avoid losses during transfer from one section to the next, the staff need to be well trained. The shrimp must be carefully moved to avoid physical trauma and environmental extremes (e.g., high temperature, low dissolved ox ygen). Record Keeping

Careful record keeping is a must. Monitoring production variables and environmental factors will provide information information on how well the system and shrimp are doing. Changes in conditions can be detected and steps taken to alleviate problems. Personnel

Well-trained personnel is the key to operating a successful farm and disease prevention. Worker failure to perform tasks according to directions or accidental errors are common causes for decreased shrimp production. Regular evaluation by managers provides an effective, positive means for keeping workers on track.

Practical Approaches to Disease Control Once you discover that you have a disease problem there are a number of approaches that can be used to control the disease. The general tendency is for farmers and veterinarians to focus on identifying identifying the “bug” “bug” or disease identification. Keep in mind mind that diseases are caused by a number of factors and that you need to carefully review all the factors in determining the cause of the problem. We do however, need to work closely with a veterinarian in order to identify and control disease problems. Good management practices can often be used to keep a disease under control and reduce the losses. In order to determine if the management strategies are effective, you need to carefully monitor the culture system as well as the he alth of the shrimp. Quarantine infected populations, as much as possible, to avoid introduction to clean shrimp growout systems. Careful monitoring is needed to make sure that sick populations do not infect healthy shrimp. When a disease problem occurs, you may may be able to reduce the stress and complete the growout cycle by decreasing the density within a raceway. A number of diseases result from problems with the feed. Improvements in the diet can improve the health of the shrimp. shrimp. In some cases, farmers farmers have found that if they withhold feed for a period of time, the system will get in balance and the health will improve. Be sure to remove sick and dead individuals so that they are not consumed by the remaining stocks. - 169 -


Another approach to a disease outbreak is to shorten the production cycle and harvest the crop early. That will allow you to reduce your losses losses and get some income before before the disease problem becomes more severe. Depending on the disease problem, it may be necessary to destroy the infected stocks. Remember to recognize recognize and address the potential for human error. People influence both animal health and production levels. Successful operations depend on reliable decisions and appropriate activities. Production management management skills and technical implementation are critical. Eradication of Viral Diseases

Once a viral disease is present, the only proven method of control is total cleanup or complete eradication of the viral disease. disease. The clean-up process is a two two step procedure involving eradication of the infected and potentially infected shrimp stocks, followed by the clean up of the facility itself. This procedure is time consuming and expensive. But when it is done correctly, it has been effective in preventing future disease problems. The procedures, disinfectants and equipment required to eradicate a viral disease are described in Bell and Lightner (1992).

Important Shrimp Pathogens Overview

Shrimp pathogens fall into seven major categories: viruses, bacteria, fungi, protozoans, rickettsia, nutritional, toxic and environmental diseases and diseases of unknown etiology. Viral disease outbreaks often result from stress factors, such as overcrowding, abnormal temperatures or low low dissolved oxygen. The only way to prevent transfer of the virus is through strict quarantine procedures. There are NO known treatments for viral viral diseases. In order to diagnose a viral disease you need to consult with a veterinarian or expert in shrimp pathology. A variety of diagnostic techniques have been developed for the the principal shrimp viruses, but they require extensive laboratory testing, which is expensive and timeconsuming. Most bacterial infections result from from extreme stress. The most common bacterial infection in Vibrio. Vibrio infections often occur following environmental stresses or marine shrimp is Vibrio. viral diseases and are not the primary primary disease problem. They have been successfully treated treated with chemicals and antibiotics; however, these treatments are only available with a veterinarians prescription in the U.S. Protozoans are found naturally in the culture environment and can cause mortalities, but they only become a problem for shrimp farmers when the environmental conditions are poor. Common Disease Concerns During Growout

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Chapter 9 – Shrimp Health Management Shrimp are exposed to a variety of opportunistic pathogens during growout and the common disease concerns during during growout are listed in Table 9.1. Many of these pathogens are present in the environment and only become a problem when the shrimp are exposed to an environmental or biological stress. The remainder of this section will include a brief synopsis of the diseases or syndromes listed in Table 9.1, methods of diagnosis and control strategies. The diseases that are addressed are those diseases that will impact shrimp in raceway growout systems. This material is primarily primarily adapted from Brock Brock and Main (1994). vannamei. Table 9-1: Common disease concerns associated with growout of L. vannamei.

Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) Runt-deformity syndrome Taura Syndrome Virus (TSV) White Spot Syndrome Virus (WSSV) Yellowhead Virus (YHV) Vibriosis Necrotizing hepatopancreatitis Mycobacteriosis Epicommensal fouling disease Black spot disease Gas bubble disease

Infectious Hypodermal and Hematopoietic Necrosis Virus

Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) is a parvo-like virus that is commonly found in cultured and wild L. wild L. vannamei stocks. Shrimp can be affected by this virus during the larval and adult stages. stages. If shrimp are infected after the postlarval stage, the most obvious sign of the disease is cuticle deformities. deformities. Shrimp will become infected with IHHNV if they consume infected shrimp and can potentially be infected by contact with IHHNV contaminated water. Diagnosis of this disease must be done using laboratory test procedures. The most reliable means of identification is with specific gene probes that have been developed for IHHNV. These tests are usually done by a shrimp health professional. There are no treatments available for for shrimp viruses such as IHHNV. The best control strategy is prevention by use of specific pathog en free (SPF) postlarvae. Runt-Deformity Syndrome

Runt-deformity syndrome (RDS) is believed to be caused by IHHNV (Wyban and Sweeney, 1991). RDS occurs during both nursery and growout stages in in L. vannamei and primarily impacts farm yields and consequently affects affects production economics. Harvests contain large numbers of small small shrimp. The major symptoms symptoms are variations variations in size distribution (e.g., coefficient of variation = 30-60%), cuticle deformities or mottled pigmentation on the majority of small shrimp, and slightly lower survival rates. The most reliable means of - 171 -

Chapter 9 – Shrimp Health Management identification is with specific gene probes that have been developed for IHHNV. IHHNV. These tests are usually done by a shrimp shrimp health professional. professional. There are no treatments available for shrimp viruses such as IHHNV. The best control strategy strategy is prevention through the use of SPF postlarvae. Taura Syndrome Virus

TSV has had a major impact on the L. vannamei culture industry in Central and South America (Lightner 1995; Brock et. al. 1977). Shrimp are primarily affected during the juvenile stage by this noda-virus. When SPF SPF or hatchery reared juvenile juvenile L. vannamei develop TSV, it is often fatal fatal because the infection infection has a rapid onset and short course. TSV should be suspected in cases where rapid mortality of juvenile L. juvenile L. vannamei is associated with sickly animals that have soft exoskeletons and expanded chromatophores. Shrimp dying in the acute infection stage will be characteristically weak and disoriented, have a soft cuticle and expanded chromatophores. You can recognize the chronic form of TSV because the cuticle degenerates and has black spots or areas of melanization. melanization. Adult animals will either die from the infection or display the black spots and cuticle degeneration. TSV is diagnosed using histopathology, bioassay or with specific gene probes that have been developed for TSV. These tests are usually done by a shrimp health professional. There are no treatments available for shrimp shrimp viruses such as TSV. The best prevention strategy is is to use SPF postlarvae. postlarvae. There are facilities that have ongoing breeding programs for resistance to TSV. White Spot Syndrome Virus

White Spot Syndrome Virus (WSSV) has had a significant impact on shrimp farming in Asia since 1993 (Flegel et. al. 1997). It was identified in cultured shrimp in Texas in 1995 and in South Carolina in 1997. The Texas and South Carolina populations were destroyed in order to prevent the spread of this serious disease to cultured cultured and wild stocks. Research in South Carolina has suggested that WSSV may have come from wild wild populations. Over 40 species have been found to act as reservoirs for this virus, including lobsters and crabs. The symptoms of this disease vary between the eastern and western hemisphere (Lightner 1996). L. vannamei in the western hemisphere have few white spots, which is the primary symptom of the disease in the eastern hemisphere. In western shrimp, we see a reduction in feeding, a loosening of the cuticle and a pink to reddish coloration. Diagnosis is done by a health professional using histology or a specific gene probes that has been developed for WSSV. A new rapid detection method has been recently been developed for WSSV (Lightner 1999) that can be used with acutely infected shrimp. There are no treatments available for shrimp viruses such as WSSV. The best strategy is prevention by use of SPF postlarvae. If WSSV is suspected, all water exchange should be stopped and if the tests are positive, the stocks should be destroyed. Yellowhead Virus

Yellowhead virus (YHV) has caused major losses in in P. monodon farms in southeast Asia since 1992 (Flegel et. al., 1997). In 1995, YHV was identified at a farm in Texas where P. where P. setiferus were being cultured (Lightner (Lightner 1996). The close proximity proximity of shrimp processing - 172 -

Chapter 9 – Shrimp Health Management plants that were handling shrimp from Asia to the farm with the disease problem, may have resulted in the the infection diagnosed in the Texas shrimp. shrimp. ). To our knowledge, there have been no other known cases of YHV in the U.S. Research studies have shown that YHV can vannamei. infect and cause mortalities in many of the penaeid species, including L. including L. vannamei. Symptoms include an initial increase in feeding rates, followed by cessation of feeding and death. The shrimp have a reddish tail, the cephalothorax is light yellow yellow and the gills are white to pale yellow or brown in color. This virus must be diagnosed by a health professional using histopathology. Like other viruses, there is no treatment for YHV. The best strategy is prevention by use of SPF postlarvae. Vibriosis

Vibriosis has caused significant disease problems during growout of L. L. vannamei. vannamei. However, these types of bacterial infections can often been controlled or prevented by reducing stressful conditions during growout. Vibriosis has been associated with stress factors such as handling, high densities, nutritional deficiencies, extremes in temperature, cuticle injuries, and elevated levels of ammonia, ammonia, salinity or nitrogen. Environmental conditions that increase the density of a particular Vibrio spp. can often lead to vibriosis. vibriosis. It is commonly found concurrently with other viruses or microbes. The impact of vibriosis will vary depending on the severity of infection, but mortalities can exceed 70%. When infections are severe, dead and dying shrimp shrimp will be plentiful and animals will not be cannibalized. In less severe cases, shrimp shrimp may be eaten by the unaffected shrimp. The symptoms symptoms include extreme weakness (shrimp may may lay on the bottom), disoriented swimming, increased pigmentation, partial cramping of the tail, diffuse muscle opacity of the abdominal musculature, musculature, or brown or black wounds on the cuticle. To prevent vibriosis in growout, you need to provide balanced culture conditions. Be sure that the shrimp are maintained in appropriate water quality conditions and that they are getting a good quality feed. Antibiotic-medicated feeds have been used to control vibriosis, however, this can only be done when the antibiotics are prescribed by a veterinarian. Necrotizing hepatopancreatitis

Necrotizing hepatopancreatitis (NHP), previously known as Texas pond mortality syndrome, is caused by a Gram-negative, bacteria that attacks the cells of the hepatopancreas. NHP occurs in juvenile and subadult L. vannamei and causes the shrimp to stop feeding and growing. Other symptoms include a soft exoskeleton, generalized surface fouling, weakness and slow death. NHP is diagnosed by histopathology histopathology or with a specific gene probe. Losses have been reduced through early detection and rapid application of oxytetracycline medicated feed. This feed must be administered under the guidance of a veterinarian. NHP does not seem to occur when salinities are below 10 ppt and therefore, may not be a problem in freshwater systems. Mycobacteriosis

Mycobacteriosis has been occasionally identified in L. in L. vannamei broodstock populations and can occur in juvenile and subadult shrimp. Mycobacterium spp. are slow growing, acid-fast bacteria that are present present in the natural environment. Like other bacterial infections, it is - 173 -

Chapter 9 – Shrimp Health Management probably associated with poor conditions (i.e., high numbers of bacteria) in the culture environment. This bacteria can infect human cuts or abrasions. Mycobacteriosis can only be diagnosed using specialized laboratory methods. There are no outward behavioral or physical signs; however, chronic infections can result in mortalities. mortalities. Although the mode of transmission is unknown, it is probably transferred by ingestion or wound contamination. There are no known treatments for mycobacteriosis. Epicommensal fouling disease

Epicommensal fouling disease is a condition caused by a variety of agents and affects all life stages of of L. vannamei. It occurs when respiratory, feeding or locomotory functions functions are impaired by excessive colonization of the cuticle surface by bacteria, protozoans, diatoms or blue-green algae. The infestation usually involves a mixed mixed population of organisms with one dominant species. In juvenile and subadult subadult shrimp the gills are commonly commonly affected, which can inhibit respiration. Shrimp appear outwardly normal, but die rapid during or immediately following exercise, handling or exposure to low oxygen conditions. The symptoms of epicommensal fouling disease include, reduced growth, reduced feed consumption, gill discoloration, abnormal swimming behavior, intolerance to exercise or low dissolved oxygen. The agents of this condition are commonly found in the culture environment, but they will increase in numbers and cause disease problems when the environmental conditions are not suitable. High densities and high concentrations of nutrients have been associated with the occurrence of this condition. Epicommensal fouling disease can be controlled by increasing the frequency and amount of water turnover, improving water circulation, decreasing density, biomass or organic loading and providing a nutritionally balanced feed. Black spot disease

L. vannamei and is a condition where there are Black spot disease occurs in all life stages of L. one or more brown or black black spots on the cuticle. It can occur on any cuticle-covered body part and the size, shape and number of lesions or spots can vary. The spots occur as a defensive response to a break in the cuticle surface. The location of the spots on the body can provide a clue about the initial cause of the disease. In tank raised shrimp, a high frequency of black spots on the dorsal surface of the third abdominal segment suggests trauma to the cuticle from contact with the tank surface during the rapid backward escape. Multiple lesions randomly distributed over the body may indicate TSV or it can result from prolonged exposure to anoxic conditions or otherwise unhealthy water quality conditions. A few black spots mainly on the lateral body surface of the shrimp indicates that the shrimp have been transferred or held in crowded conditions and have damaged each other. Diagnosis and understanding of Black Spot disease requires observing the distribution pattern of the lesions and assessing the number of individuals affected. The best control is is prevention of black spot disease. However, if the problem is a result of overcrowding, it can be reduced by lowering the densities. Lesions associated with with poor water quality conditions may respond once environmental quality is improved.

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Chapter 9 – Shrimp Health Management Gas Bubble Disease

Gas bubble disease is a potentially lethal condition caused by the supersaturation of the water with air. The condition generally occurs when air is forced into the water under pressure. While gas bubble disease has not been much of a problem in pond culture and flow through systems it can become a problem in recirculating recirculating systems. The source of the problem is often traced to faulty plumbing of the filtration system. Often people neglect to glue the PVC fittings on the suction side of the pump. It is reasoned that since it is not under pressure, it will not separate, and not gluing makes it easier to reroute the piping if needed. However, air may be sucked in around loose fitting joints, mixing with the water, where it goes into solution under pressure. This is especially true if the water is pumped through mechanical filters, which can produce considerable backpressure on the pump. Another source of air entering the water line is through a venturi setup by low water levels at the entrance to the standpipes. The saturated water is then returned to the tank or raceway. Rapid warming of the water may also produce gas bubble disease. If the temperature increases, the blood of a shrimp will hold less nitrogen in solution allowing gas bubbles to form. This, however, is a rare occurrence that most often happens when a pump overheats. The saturated air is taken up by the shrimp through their gills. The less soluble nitrogen fraction of the air is released from the blood where it is free to form small bubbles, generally in the gill region. There it blocks the flow of blood and thus the exchange of oxygen and carbon dioxide. Gas bubble disease is generally detected by erratic, erratic, disoriented swimming swimming and by the appearance of white discolored gill tissue. Looking at gill tissue under a microscope, using low-resolution magnification, will reveal numerous gas bubbles in the gill filaments. Gas bubble disease is controlled through the prevention of exposure to conditions of nitrogen gas supersaturation. For a recirculating system, system, weekly saturometer readings for total gas pressure at several points in the system is a preventative tactic for early detection of nitrogen gas supersaturation. supersaturation. If a problem is detected, the source must be identified and corrected. Dissolved Oxygen Crisis

Dissolved oxygen crisis occurs when the oxygen demand exceeds the tank system inputs. This often occurs late in the growout cycle when you are feeding large quantities of feed and have high biomass of shrimp shrimp in the system. It can also occur in recirculating systems systems when there is a power failure failure that interferes with supplemental aeration and water exchange. When shrimp are first exposed to low dissolved oxygen conditions, they will display increased activity in the form of slow surface swimming. swimming. Affected shrimp swim swim aimlessly, have a depressed escape response and have diffuse opacity (milky loss of transparency) of the abdomen. This problem is controlled by having backup for for power failures and a monitoring system to determine dissolved dissolved oxygen levels. Once the oxygen crisis is corrected, the surviving shrimp will usually improve their condition.

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Literature Cited Bell, T.A. and D.V. Lightner 1992. Shrimp facility clean-up and restocking procedures. Cooperative Extension, College of Agriculture, University of Arizona, Tucson, Arizona, USA. Brock, J.A. 1992. Current diagnostic methods for agents and diseases of farmed marine shrimp. In: In: Fulks, W. and K.L. Main (Eds.) Diseases of cultured penaeid shrimp in Asia and the United States. The Oceanic Institute, Honolulu, Hawaii. pp. 209-231. Brock, J.A. 1996. Some consideration of human factors as variables in disease events in marine aquaculture. In: Main, K.L. and C. Rosenfeld (Eds.) Aquaculture health management strategies for marine fishes. The Oceanic Institute, Institute, Honolulu, Hawaii. Pp. 157-162. Brock, J.A. and K.L. Main 1994. A guide to the common problems and diseases of cultured Penaeus vannamei. vannamei. World Aquaculture Society, Baton Rouge, Louisiana, USA. Brock, J.A., R.B. Remedios, D.V. Lightner and K. Hasson 1997. Recent developments and an overview of Taura Syndrome of farmed shrimp in the Americas. In: Americas. In: Flegel, T.W. and I.H. MacRae (Eds.). Diseases in Asian Aquaculture III. Fish Health Section, Asian Fisheries Society, Manila, Philippines. Pp. 275-283. Browdy, C.L. 1998. Recent developments in penaeid broodstock and seed production technologies: Improving the outlook for superior captive stocks. Aquaculture 164 (1-4): p. 3-21. Flegel, T.W., S. Boonyaratpalin and B. Withyachumnarnkul 1997. Progress in research on yellow-head virus and white-spot virus in Thailand. In: Flegel, T.W. and I.H. MacRae (Eds.). Diseases in Asian Aquaculture III. Fish Health Section, Asian Fisheries Society, Manila, Philippines. Pp. 285-295. Fulks, W. and K.L. Main 1992. Diseases of cultured penaeid shrimp in Asia and the United States. The Oceanic Institute, Honolulu, Hawaii. 293 pp. Lightner, D.V. 1988 Diseases of cultured penaeid shrimp in the Americas In: Sindermann, C.J. and D.V. Lightner (Eds.). Disease diagnosis and control in North American Marine Aquaculture. Second Edition. Elsevier Scientific Scientific Publishing Co., Amsterdam. Pp. 8-113. In: McVey, J.P. (Ed.) CRC Lightner, D.V. 1993. Diseases of cultured penaeid shrimp. In: Handbook of Mariculture Crustacean Aquaculture Vol. 1, Second Edition. CRC Press, Boca Raton, Florida. Pp. 393-486.

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Chapter 9 – Shrimp Health Management Lightner, D.V. 1995. Taura Syndrome: an economically important viral disease impacting the shrimp farming industries of the Americas including the United States. In: Proceedings of the Ninety-ninth Annual Meeting, Meeting, USAHA, Reno, NV, USA. USA. Pp. 3652. Lightner, D.V. 1996. A Handbook of Shrimp Pathology and Diagnostic Procedures for Diseases of Cultured Penaeid Shrimp. World Aquaculture Society, Baton Rouge, Louisiana, USA. Lightner, D.V. 1999. Rapid method for diagnosis of WSSV in whole tissue tissue mounts. Addendum to: A Handbook of Shrimp Pathology and Diagnostic Procedures for Diseases of Cultured Penaeid Shrimp. World Aquaculture Society, Baton Rouge, Louisiana, USA. Moriarty, D.J.W. 1998. Control of luminous Vibrio species in penaeid aquaculture ponds. Aquaculture 164 (1-4): 351-358. Moss, S.M., W.J. Reynolds and L.E. Mahler 1998. Design and economic analysis of a prototype biosecure shrimp growout facility. facility. In: Moss, S.M. (Ed.) Proceedings of the U.S. Marine Shrimp Farming Program Biosecurity Workshop February 14, 1998. The Oceanic Institute. Pp. 5-17. Wyban, J.A. and J.N. Sweeney 1991. Intensive shrimp production technology – The Oceanic Institute Shrimp Manual. Oceanic Institute, Honolulu, Hawaii, USA. 158 pp.

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Chapter 10 Economics of Shrimp Culture in Recirculating Recirculating Aquaculture Systems by Peter Van Wyk Harbor Branch Oceanographic Institution

Introduction Demonstration by Harbor Branch Oceanographic Institution of the technological feasibility of culturing the marine shrimp, Litopenaeus vannamei (also known as Penaeus vannamei), in high density, freshwater recirculating aquaculture systems has generated a tremendous amount of interest. Many people are looking at this new technology as a potential investment opportunity. opportunity. The purpose of this analysis was to determine the economic feasibility of culturing marine shrimp in freshwater recirculating aquaculture systems using the data gathered by Harbor Branch during a one-year demonstration study sponsored by the Florida Department of Agriculture and Consumer Services (FDACS Contract No. 4520). In addition, an analysis was made of the sensitivity of the enterprise profitability to selected economic and production variables.

Baseline Assumptions A spreadsheet model was developed to evaluate the economic feasibility of producing Litopenaeus vannamei in freshwater recirculating production systems. systems. The model is based on the Harbor Branch Oceanographic Institution (HBOI) shrimp production facilities. We have incorporated into the model actual construction and production costs and system productivity data in an effort to make the model as realistic as possible. Facility Description

The economic model describes a hypothetical enterprise consisting of twelve greenhouses, instead of the three that are currently in operation at HBOI. This was done to take advantage of the economies of scale associated with a larger production facility. facility. The two most important economies of scale are related to the manager’s salary and the cost of feed. In a small operation the manager’s salary is divided over a relatively small amount of production. As a result, the the cost per pound of shrimp shrimp produced goes up significantly. significantly. In a larger operation the manager’s salary is divided over a much larger amount of production, and therefore has a much smaller smaller impact on the cost per pound produced. The second important economy of scale a large facility can take advantage of is the ability to buy feed in truckload quantities. Freight costs on less than truckload quantities of feed may add as much as $0.15 per pound to the cost of the feed. The feed itself is often cheaper when purchased in

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Chapter 10 - Economics of Shrimp Culture in Recirculating Systems

truckload quantities. Most manufacturers have a sliding price scale, according the volume of feed purchased. Feed purchases in excess of 20 tons may be as much as $0.05/lb cheaper than feed purchased in 1 ton lots. The combined savings associated with purchasing feed by the truckload may be as much as $0.20 per pound of feed. This may reduce the overall cost of production by $0.40/lb, assuming a feed conversion rate of 2.0. The economic model is based on a production system housed in twelve 30 ft x 150 ft greenhouses. The greenhouses are built from a commercial greenhouse kit consisting of a frame made from 14-gauge galvanized pipe, and a roof covering made from a double layer of 6-mil polyethylene plastic sheeting (see Chapter 3). A small small inflator inflator fan fills the space between the two layers of plastic with air, creating an insulating air space between them. Each greenhouse is covered with a 40 ft ft x 150 ft 95% shade cloth. The gable ends consist of a treated lumber frame frame covered with 6-mil 6-mil plastic sheeting. The greenhouses are ventilated using two 54-inch 1.5-hp exhaust fans located on one gable end and two 57-inch air inlet shutters located on the other gable end. The fans and shutters are thermostatically controlled. Each greenhouse is provided with a 300,000 BTU propane gas heater and air circulation fan to maintain suitable temperatures during the winter months. This system system is sized to be able to maintain inside temperatures temperatures up to 25°C higher than outside temperatures. temperatures. The greenhouses used in the HBOI/FDACS demonstration project were not heated. However, other greenhouses at HBOI are equipped with this type of heating system, so reliable data was available relative to the cost and performance of propane space heaters. Other types of heating systems systems could be used, and may be more economical. Generally it is more more costeffective to heat the water directly, rather than to heat the air. The model assumes each greenhouse houses two three-phase production systems similar to the System B design described in Chapter 4. The size of the tanks, filters, pumps, blowers, and ventilation system have been scaled up in the model to make sure that they give the same performance as the corresponding units in the 96-foot greenhouses. The cost of the system in the model was determined from prices actually paid for equipment items and quoted prices for equipment items that differed from those actually used in the demonstration project. Each culture tank in the model system measures 14.5 ft x 140 ft divided into three sections, each section corresponding to a different phase in the production process. The first phase is carried out in a 14 ft x 14.5 ft section at the upper end of the raceway. This section occupies approximately 10% of the culture culture area. Phase II is carried out in the middle section of the raceway, which measures 14.5 ft x 43 ft (30.7% of the culture area). The shrimp are grown up to market size in Phase III, which measures 14.5 ft x 83 ft (59.3% of the culture area). The culture tanks consist of a wooden frame supporting a black 30-mil high-density polyethylene liner (Chapter 5). The wooden frame is one board width high and is built using 2”x12” pressure-treated lumber boards supported by galvanized pipe set vertically in a concrete anchor. The vertical pipe supports are set on 6-ft centers. The ground inside inside of the wooden frame is excavated to a depth of 1.5 foot with a berm (1:1 slope) extending from the

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bottom of the wooden frame to the the floor of the tank. When filled, the culture tanks are 22’ deep. The solids filter consists of a 6-ft diameter cylindro-conical tank filled with small plastic filter beads. The beads are hollow polyethylene cylinders with short, radiating fins to enhance the surface area of the bead. The water enters the filter near the bottom and flows up through the beads and exits by gravity through a slotted pipe near the water surface. The filtered water flows into an adjacent sump that functions as the the biofilter. Solid wastes trapped in the bead bed are flushed twice a week by emptying the tank. The biofilter consists of an aerated, submerged bed of biofilter media contained in a cage constructed of PVC pipe and 1/4” extruded plastic screen material. The biofilter media consists of the same polyethylene polyethylene cylindrical beads as was used in the solids filter. filter. This 2 3 biofilter media has a specific surface area of 259 ft /ft . The biofilter media and cage are contained in a rectangular 6 ft x 8 ft x 4 ft polyethylene tank. The water is circulated using a 3/4-hp, low head, high volume centrifugal pump that delivers 130 gpm of flow at 10 feet of head. At this flow rate the water is recirculated through the water treatment system approximately every 200 minutes. Air is supplied to the system by a 3.5-hp regenerative blower, which delivers 150 cfm at a pressure of 50 inches of water. One blower is required for every two greenhouses. A 16-hp gasoline powered blower serves serves as a backup for each of the electrical blowers. These blowers are equipped with a pressure switch switch that starts up the backup blower in the event of a power loss. The air is delivered into the culture tanks through 54 3”x1” medium medium pore fused fused silica diffusers. An additional 10 diffusers are positioned in a grid located in the bottom of the biofilter tank to aerate and tumble the biofilter media. The source of water for the shrimp production facility is a freshwater well with two 3-hp centrifugal well pumps. A well water pretreatment system is required for every six greenhouses. The pretreatment system consists of a degasser, a biofilter tank, a 5,500-gallon water storage tank, and a 1.25 hp centrifugal water supply pump. The raw well water is pumped to the top of a degassing column filled filled with plastic media. Air is pumped through the degassing tower by a high volume 0.25 hp air blower. Supersaturated gases such as hydrogen sulfide and carbon dioxide are removed in the degassing column, and dissolved oxygen levels are increased. The water leaving the degassing column flows into into an aerated submerged bed biofilter consisting of a 12-ft diameter fiberglass tank filled with barrels of crushed oyster shell. shell. Water is circulated through the oyster oyster shell beds powered by airlift pumps inserted into the beds. The bed is designed to reduce Total Ammonia Nitrogen concentrations in the well water from 1.0 mg TAN/liter to less than 0.05 mg TAN/liter. The water flows from the biofilter to the water storage reservoir. The water in the storage reservoirs is recirculated through a sand filter and is available on demand to the shrimp culture tanks.

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The effluent from the solids filter drains into a concrete sump/lift station where a 1/2-hp trash pump is located. The trash pump is fitted with a mercury float switch switch that activates the pump when the sump begins to fill. The wastewater is pumped from the solids sump to a 1acre retention pond. Chlorine tablets are placed in this sump to kill any escaping shrimp. There is one concrete drain/chlorination sump for every four greenhouses.

Investment Requirements Land

The land requirement for twelve greenhouses is approximately two-and-a-half acres. An additional 1 to 1.5 acres are needed for a retention pond, and perhaps another acre for water treatment and storage tanks, feed sheds, office, and parking. A minimum of five acres would be required to house a 12-greenhouse production facility. The land should be zoned either for agriculture or for industry. The most important requirement is the quality of wellwater wellwater that is available (see Chapter 8). Minimally, the water should have a chloride concentration of at least 300 mg/l, and a Total Hardness of 200 mg/l. The water should should be free from pesticides. pesticides. The cost of land varies widely, depending on zoning, proximity to population centers and surrounding surrounding land use. For the purposes of this model I have assumed assumed a land price of $2,500 per acre. The overall investment in land is $12,500. This model assumes assumes access roads and electrical power are already available at the location. The land cost would be significantly higher if if it were necessary to build an access road or bring power lines in to the site. Buildings and Improvements

The shrimp culture tanks and recirculating water treatment systems are housed in 30-foot x 150-foot quonset-style greenhouses. These greenhouses are built using commercially available kits. The kit comes comes complete with all the necessary frame hardware, two 54" 11/2hp exhaust fans, two 57" air inlet shutters, 2 NEMA 4X thermostats, inflator fans, double polyethylene roof and sidewall covering, a man-door and an 8'x8' sliding door. Additional lumber is needed to build the frame for the gable ends. The cost for for the kit is $7,095/greenhouse ($1.58/square foot). Site preparation and construction costs add another $5,000 to the cost of a greenhouse. Each greenhouse must be equipped with a 95% shade cloth (40’ x 150’), at a price of $1,500/shadecloth. Installation of the electrical wiring costs approximately $5,000/greenhouse. Plumbing costs are placed at $2,500 per greenhouse. A 20’ x 15’ metal building with a slab floor and harvest sump sump is required for for acclimation and quarantine of newly purchased postlarvae. The acclimation/quarantine building houses two 1,500 liter fiberglass, U-shaped acclimation tanks, each supplied with air from a 1/3 hp blower. The freshwater for acclimation is is fed through an elevated head tank. The water level in this tank is maintained at a constant depth by means of a float valve. This building will cost approximately $3000, excluding the tanks and blower.

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A rodent-proof, air-conditioned feed storage building capable of storing up to 30 tons of feed is a necessity. A 1,000 square foot metal frame building built on a 6-inch concrete slab can be built for $3,000, not including the air conditioner. Well-installation is assumed to cost $1,000, but this can vary depending on the depth of the well and the type type of material the the well digger must drill through. Three one-quarter acre retention ponds, connected in series by 6-inch overflow pipes, can be built for about $1,500. The overall cost of buildings and improvements for the wells, retention ponds, greenhouses and support buildings comes to $261,640. An additional $60,000 must be spent in Years 610 to replace polyethylene greenhouse covers and shade cloth. Table 10-1 summarizes the investment requirements for buildings and improvements. Table 10-1: Summary of the capital costs for initial purchase and installation of buildings. Four greenhouses are built in each of the first three years of the project. Buildings and Improvements Improvements Item

Value Year 1

Value Year 2

Value Year 3

Units

Price

Retention Ponds

acre

$1,500

$1,500

$0

$0

Well Installation

ea

$1,000

$1,000

$0

$0

Feed & Storage Shed

ea

$3,000

$3,000

$0

$0

Acclimation Greenhouse

ea

$3,000

$3,000

$0

$0

Greenhouse Kit, complete

ea

$7,095

$28,380

$28,380

$28,380

Site Preparation

greenhouse

$1,000

$4,000

$4,000

$4,000

Greenhouse Construction Costs

greenhouse

$4,000

$16,000

$16,000

$16,000

Shade Cloth

greenhouse

$1,500

$6,000

$6,000

$6,000

Electrical Installation

greenhouse

$5,000

$20,000

$20,000

$20,000

Plumbing

greenhouse

$2,500

$10,000

$10,000

$10,000

$92,880

$84,380

$84,380

Tanks & Sumps

Table 10-2 summarizes the investment requirements for tanks and filtration equipment, which are described in detail in Chapter 4. Each greenhouse houses two culture tanks (raceways) which measure 14.5’ x 140’. Each of these raceways is partitioned into a nursery section, an intermediate growout section, and a final growout growout section. The lumber, galvanized pipe, and hardware for the raceway frame costs $1,200/raceway. A 23-ft wide roll of 30-mil HDPE liner material sells for $0.23/ft2 (delivered price). The total cost for lining one three-phase raceway is $900, or $1,800/greenhouse. Combining the cost of the frame and the liner, a single three-phase three-phase raceway costs $2,100. The polyethylene solids solids filter and biofilter tanks each cost $500. Each of these tanks is loaded with a polyethylene biofilter media called Kaldnes media. The delivered price of Kaldnes media is $28.55/ft3, or about $1,000/m3 of media. Each system requires 1.5 cubic meters of media. The cost of the biofilter media is $1,500 per system.

- 183 -


Table 10-2:

Summary of the initial capital investment requirements for tanks and filtration equipment.

Tanks and Filtration Equipment Value Year 1

Value Year 2

$ 1,500

$1,500

$1,500

$0

ea

$ 1,500

$1,500

$1,500

$0

Reservoir Tank

ea

$ 5,500

$5,500

$5,500

$0

Drain/Chlorination Sump

ea

$ 1,500

$1,500

$1,500

$1,500

racew raceway ay

$ 1,200 1,200

$9,600 $9,600

$9,600 $9,600

$9,600 $9,600

Item

Units

Price

Degassing Column + Media

ea

Pretreatment Biofilter Tank

Growo Growout ut Tank Tank Lumber Lumber & Hardwa Hardware re

Value Year 3

Growout Tank Liners

ea

$

900

$7,200

$7,200

$7,200

Acclimation Tanks (1500 liters)

ea

$ 3,000

$3,000

$ 0

$0

Acclimation Head Tank

ea

$

500

$ 500

$ 0

$0

Solids Filter Tank

ea

$

500

$4,000

$4,000

$4,000

Biofilter Tank

ea

$

500

$4,000

$4,000

$4,000

Biofilter Media

cu.m.

$12,000

$12,000

$12,000

$50,300

$46,800

$38,300

$ 1,000

Two 1,500-liter fiberglass U-bottom acclimation tanks supported in a frame constructed of 2"x 4" lumber will cost $1,500 per tank. A 300-liter polypropylene head tank elevated above the acclimation tanks will cost about $500, including the lumber for the support tower, and a float valve to maintain a constant level of freshwater in the tank. The water pretreatment system consisting of a degassing column, biofilter, and water storage reservoir tank represents a significant expense, totaling $8,500 per system. One system is needed for every six greenhouses. One water pretreatment system is built in each of the first first two years years of the project. It is conceivable that some some sites sites will will have adequate water quality straight from from the well. This might allow the pretreatment degassing column and biofilter to be eliminated. The water storage reservoir would still be a required piece of equipment. The total cost of tanks and sumps for the facility comes to $135,400. An additional $21,600 will be required during Years 6-8 for replacement of the raceway tank liners. Machinery & Equipment

Machinery and equipment capital costs are summarized in Table 10-3. The gas heating systems for the greenhouses represent a significant significant expense. One gas heater is required for each of the twelve greenhouses. The cost for a single heater is $3,275, so the total initial investment in heaters would be $39,300. This cost is spread evenly over the first first three years of the project. The economic life of the heaters is expected to be 7 years. An additional $13,100 will be spent in each of Years 8, 9, and 10 of the project to replace heaters. Other options for heating the greenhouses are also available, including propane powered plate heat exchangers, electric immersion heaters, and solar water heating systems. systems. A separate analysis

- 184 -


Table 10-3: Summary of the capital costs for initial purchase of machinery and equipment. Machinery & Equipment Item

Units

Value Year 1

Price

Value Year 2

Pickup Truck, 1/2 ton

ea

$ 20,000

$ 20,000

$

Gasoline Powered Blower, 11 hp

ea

$ 3,269

$

3,269

$

2 HP Well Pump

ea

$

783

$

783

$

2 hp Sump Pump for Lift Station

ea

$

400

$

400

0.25 HP Air Blower for Degasser

ea

$

200

$

1.25 HP Centrifugal H2O Supply Pump

ea

$

800

1/4 HP Acclimation Blower

ea

$

3.5 HP Blower

ea

1.5 HP Centrifugal Pump

0

$

0

$

3,269

783

$

0

$

400

$

400

200

$

200

$

0

$

1,600

$

1,600

$

0

350

$

350

$

0

$

0

$

972

$

1,944

$

1,944

$

1,944

ea

$

800

$

6,400

$

6,400

$

6,400

Gas Heating System

ea

$ 3,275

$ 13,100

$ 13,100

$ 13,100

Air Conditioner

ea

$

600

$

1,200

$

0

$

0

D.O. Meter

ea

$

650

$

1,300

$

650

$

650

Water Quality Test Kit

ea

$

450

$

450

$

0

$

0

Insulated Harvest Tote

ea

$

500

$

500

$

500

$

500

$ 51,496

3,269

Value Year 3

$ 28,846

$ 26,263

would be required to determine which of these options would best balance between performance and overall cost (capital cost + operating cost). The low head, high volume 3/4-hp centrifugal pumps ($800) cost more than twice as much as high head, low volume 2-hp centrifugal pumps ($375) that deliver roughly the same volume at the required 10 feet of head pressure. However, over the three-year life of the the pump, a low head pump will save over $3,000 in electrical costs. Nevertheless, the capital investment investment for the pumps is high. With two pumps required per greenhouse, a total of 24 pumps are needed. The economic life of the pump is 5 years, years, so 8 new pumps will need to be purchased in Years 6, 7, and 8 at a cost of $6,400/year. One 3.5-hp regenerative blower is required for every 2 greenhouses and one 16-hp gasoline powered backup blower is required for every 4 greenhouses. Each of the 3.5-hp blowers costs $972, so the total investment for blowers is just under $4,000. Three gasoline-powered blowers will be required at a cost of $3,269 each. The 1/4-hp regenerative blower for the acclimation tanks will cost $350. The initial investment for machinery and equipment $135,400 spread over the first three years of the project. Over the remaining 7 years of the 10 year planning horizon, an additional $127,520 will be required for replacement of old equipment.

- 185 -


Office Equipment

In Year 1 a computer, printer, facsimile machine, copying machine, telephone, and office furniture are purchased for the office at a total cost of $4,850 dollars. dollars. The office equipment is replaced after 5 years, while the furniture is replaced replaced after 10 years. The costs for all office equipment are summarized in Table 10-4. Table 10-4: Capital costs for office equipment. Office Equipment Units

Price

Value Year 1

Value Year 2

Value Year 3

Personal Computer

ea

$ 1,200

$1,200

$0

$0

Printer

ea

$

250

$250

$0

$0

Fax Machine

ea

$

300

$300

$0

$0

Copying Machine

ea

$ 1,500

$1,500

$0

$0

office

$ 1,500

$1,500

$0

$0

$100

$0

$0

$4,850

$0

$0

Item

Office Furniture Telephone

ea

$

100

Total Investment Requirements

The total capital investment requirements for the entire 10-year planning horizon are summarized in Table 10-5. Initial purchase of the required capital items during the 3-year construction phase of the project will cost $517,507. An additional $212,470 will be spent in Years 4-10 to replace worn out equipment.

- 186 -

Table 10-5: Capital cost summary for a 12-greenhouse facility for producing marine shrimp in recirculating aquaculture systems. Item

Year 1

Year 2

Year 3

Year 4

Year 5

Year 6

Year 7

Year 8

Year 9

Year10

New Investment Agricultural Land

$12,500

$0

$0

$0

$0

$0

$0

$0

$0

$0

Buildings & Improvements

$92,880

$84,380

$84,380

$0

$0

$0

$0

$0

$0

$0

Tanks and Filtration Equipment

$50,300

$46,800

$38,300

$0

$0

$0

$0

$0

$0

$0

Machinery & Equipment

$51,496

$28,846

$26,263

$0

$0

$0

$0

$0

$0

$0

Office & Office Equipment

$4,850

$0

$0

$0

$0

$0

$0

$0

$0

$0

$212,026

$160,026

$148,943

$0

$0

$0

$0

$0

$0

$0

Buildings & Improvements

$0

$0

$0

$6,000

$6,000

$6,000

$6,000

$12,000

$12,000

$12,000

Tanks & Filtration Equipment

$0

$0

$0

$0

$0

$7,200

$7,200

$7,200

$0

$0

Machinery & Equipment

$0

$0

$0

$450

$4,783

$40,377

$17,744

$28,600

$17,883

$17,683

Office Equipment

$0

$0

$0

$0

$0

$3,350

$0

$0

$0

$0

Total Investment

$0

$0

$0

$6,450

$10,783

$56,927

$30,944

$47,800

$29,883

$29,683

$212,026

$160,026

$148,943

$6,450

$10,783

$56,927

$30,944

$47,800

$29,883 $29,883

$29,683 $29,683

Total Investment Capital Replacement

Total Capital Investment


Process Description and Production Assumptions The economic model assumes shrimp will be raised using a three-phase production strategy. In a three-phase system, the growout is divided into three periods, each period lasting for approximately one third of the total growout time period. In this case the nursery phase will last 58 days, while the intermediate and final growout phases will each last 61 days, giving a total growout time of 180 days. The nursery phase will will lie fallow an average of 3 days between harvest and subsequent restocking. With this approach, market size size shrimp will be harvested from the the final growout section every 61 days. In one year a single three-phase three-phase system will produce 6 crops of shrimp. The three-phase system allows for higher production levels than a single-phase system because in a three-phase system the biomass of each raceway at the time of stocking is much closer to the final harvest biomass. Raceway space is used more efficiently than than in a single phase system in which raceways are maintained at low densities throughout the early part of the growout cycle. Another advantage of the three-phase system is that it provides more frequent harvests of marketable marketable shrimp. By staggering staggering the stocking schedule, the 24 raceways in this production system allow for harvests of market-size shrimp every 2 to 3 days. Table 10-6: Key production assumptions. Production Assumptions Item

Nursery

Intermediate

Final

2

2

2

Rearing Unit Length (ft)

14.0

43.0

83.0

Rearing Unit Width (ft)

14.5

14.5

14.5

80%

85%

90%

Number of Days to Transfer or Harvest

58

61

61

Number of Fallow Days

3 19,584

16,646

14,982

Percent Survival - Overall (%)

80%

68%

61%

Density at Beginning of Phase (shrimp/m2)

1,351

348

150

Density at End of Phase (shrimp/m2)

1,081

296

135

Density at End of Phase (kg/m3)

1.68

2.43

2.46

Size of Shrimp at End of Phase

1.5

8.2

18.1

Total Weight of Shrimp at End of Phase (kg)

29

137

271

1.72

1.77

1.76

Number of Production Units/Greenhouse

Number of PLs Purchased per Crop

28,800

Acclimation Survival

85%

Number of Acclimated PLs Stocked in Nursery

24,480

Percent Survival - Phase (%)

Number of Shrimp Surviving to End of Phase

Cumulative Feed Conversion Ratio (end of phase)

- 188 -


For each crop, 28,800 postlarval shrimp (PL8) are purchased and held for one week in the acclimation/quarantine tanks. Assuming a survival of 85% in the acclimation system, a total of 24,480 freshwater acclimated postlarval shrimp (PL15+) will be stocked into the nursery section for each crop. The stocking density in in the nursery section will be 1,351 shrimp/m2. The shrimp spend 58 days in the nursery section. Growout temperatures will be maintained throughout the year year between 28-32°C. Based on the growth rates observed in the the HBOI demonstration systems, the shrimp will weigh approximately 1.5 grams at the end of the 8week nursery period. Survival to the end of the nursery phase is expected to be about 80%. The intermediate and final final growout phases last 61 days apiece. Survival is expected to be 85% during the intermediate phase of the production cycle, and 90% during the final growout phase, giving an overall survival (PL to final harvest) of 61%. The shrimp are expected to average 8.2 grams at the end of the intermediate phase. The final harvest weight of the shrimp after 180 days of growout is expected to be 18.1 grams, which corresponds to a 36-40 tail count per pound. The final harvest density of shrimp is expected to be 135 shrimp/m2, or 2.45 kg/m2 (4.8 kg/m3). Table 10-6 provides a summary of the important assumptions regarding the growout process.

Production Schedule The cash flow model assumes assumes the first three three years are building years. Four greenhouses are built in each of the first first three years. Greenhouse construction takes place during the first quarter of the year. One greenhouse per month is completed completed and stocked in March, April, May, and June of each of the first three years of the project. Table 10-7 summarizes the production schedule for the first first four years years of the project. The production cycle for any given phase of the production process lasts 61 days, so each phase completes 6 complete production cycles in a one year period. The production schedules for the post-construction years of the project (Years 4 -10) are nearly identical. In these years, 144 complete production cycles are completed per year over the whole facility (12 greenhouses x 2 raceways/greenhouse x 6 cycles/ raceway/year = 144 cycles/year).

Table 10-7:

Production Schedule for the the first four years of the project. project. The production schedule for subsequent years is the same as that for Year 4.

Production Schedule

Year

Year 1

Year 2

Year 3

Year 4-10

Raceways Stocked

38

86

134

144

Raceways Harvested

14

64

112

144

Phase I Production Cycles

34

83

120

144

Phase II Production Cycles

26

75

124

144

Phase III Production Cycles

18

67

104

144

- 189 -


Table 10-8: Summary of production inputs and outputs. Farm Production and Inputs Used Quantity Years 410

Quantity Year 1

Quantity Year 2

Quantity Year 3

Phase I

33.6

83.0

132.5

143.6

Phase II

25.6

75.0

124.5

143.6

Phase III

17.6

67.0

116.5

143.6

38

86

134

144

28,800

28,800

28,800

28,800

1,094,400

2,476,800

3,859,200

4,147,200

14

64

112

144

14,982

14,982

14,982

14,982

Ave. Wt. of Shrimp at Harvest (g)

18.1

18.1

18.1

18.1

Total Wt. of Shrimp Harvested/Raceway/Crop (kg)

271

271

271

271

Total Wt. of Shrimp Harvested During Year (kg)

3,787

17,314

30,299

38,956

Total Wt. of Shrimp Harvested During Year (lbs)

8,342

38,136

66,738

85,806

Juvenile 600-850 Required/Year (kg)

85

211

337

365

Juvenile 850-1200 Required/Year (kg)

164

405

646

700

Juvenile No. 3 Crumble Required/Year (kg)

961

2,376

3,791

4,110

40% Protein 3/32" Grower Required/Year (kg)

835

2,066

3,296

3,573

35% Protein 3/32" Grower Required/Year (kg)

10,543

33,272

57,820

71,298

Hourly Employees

1

2

3

3

Other Inputs Electricity (kw-hrs)

158,155

290,030

413,510

413,510

Propane (gallons)

4,068

16,068

28,068

36,000

Fuel - Diesel (gallons)

120

120

120

120

Fuel - Gasoline (gallons)

315

1,228

2,116

2,638

Office Rental (months)

0

0

0

12

Maintenance & Repairs

179,526

359,052

538,578

538,578

26

75

124

144

Ice & Packing (1 unit/kg harvested)

3,787

17,314

30,299

38,956

Marketing (1 unit/kg shrimp harvested)

3,787

17,314

30,299

38,956

Shipping & Sales (1 unit/kg shrimp harvested)

3,787

17,314

30,299

38,956

Accounting Fees (1 unit/kg shrimp harvested)

3,787

17,314

30,299

38,956

Legal Fees (1 unit/kg shrimp harvested)

3,787

17,314

30,299

38,956

212,026

160,026

148,943

0

Farm Production Production Cycles Completed

Stocking No. of Raceways Stocked No. of PLs Stocked Per Raceway/Crop Total No. of PLs Stocked Per Year Harvest No. of Raceways Harvested During Year Ave. No. of Shrimp Harvested/Raceway/Crop

Feed Postlarval Diet - 400 micron

Labor

Operating Supplies (1 unit/crop)

Insurance (1 Unit/Dollar Capital Investment)

- 190 -


Expected Production At the end of the 180-day growout period the shrimp are expected to average 18.1 grams per shrimp. The growout period was selected to allow the shrimp to reach an average harvest size 18 grams per shrimp. This improves the chance of selling the shrimp for an acceptable price. The shrimp in our study grew at an average rate of 0.7 grams per week when temperatures averaged between 26-28ºC. At this growth rate, the shrimp reach the size of 18 grams in 26 weeks. Assuming an overall survival of 61%, and 24,480 freshwater acclimated postlarvae stocked per crop, a total of 14,982 shrimp will be harvested each crop. The total weight harvested per crop will be approximately 271 kg (597 lbs). With twelve greenhouses and 24 growout tanks in production, a total of 144 crops would be harvested per year, yielding an expected 38,956 kg (85,806 lbs) of shrimp per year. This corresponds to an average weekly harvest total of 1,650 lbs of shrimp shrimp per week. Predicted annual production production is summarized summarized in Table 10-8. If these shrimp bring an average of $5.24/lb, the annual revenue from shrimp shrimp sales (after (after Year 4) would be $449,623. Production Inputs and Operating Costs

Production inputs and operating costs increase as a function of the number of production cycles completed. Production units in in operation for a full year complete six production cycles per year. When the faciltiy is operating at full capacity (Years 4-10), 144 production cycles are completed per year. Operating costs during these years total just over $300,000 per year. The most important production inputs are seed, feed, labor, and energy. Table 109 itemizes the key production inputs and their unit costs. Seed

All postlarvae stocked stocked must be Specific Specific Pathogen Free (SPF). SPF postlarvae are guaranteed to be free from the known viral diseases, including Baculovirus, Infectious Hypodermal Hematopoetic Necrosis Virus (IHHN), Taura Syndrome Virus (TSV), and White Spot Syndrome Virus (WSSV) (see Chapter 9). SPF postlarvae are available from only a few hatcheries and are more more expensive than non-SPF postlarvae. Commercial hatcheries do not sell freshwater freshwater acclimated postlarvae, preferring instead to sell younger younger animals. The postlarvae most likely would be purchased as a PL8. Animals this young young are not yet capable of being acclimated to freshwater. These PLs must be held in seawater until they reach the the age of PL12, when they have developed the physiological capability of adapting to near freshwater conditions. At that time time they can be acclimated to freshwater over a period of three days (Chapter (Chapter 6). The price of commercially available SPF postlarvae ranges from $7.00 - $10.00 per thousand, depending on the hatchery and the age of the animals purchased. Sea salt, feed, and labor to acclimate the PLs adds up to about $2.61/1000 acclimated PLs. Assuming an initial cost of $10.00 per thousand and a survival of 85% through the acclimation period, the net cost of the acclimated postlarvae stocked in the nursery phase would be about $14.85 per thousand. However, postlarvae are highly cannibalistic during this period in their lives, and at high densities losses of up to 3% or more of the population per day are possible. Excessive mortality will significantly drive up the cost

- 191 -


Table 10-9: Key production inputs and unit costs. Operating Input Unit Costs Item

Units

Unit Cost

Shrimp Postlarvae

1000 PLs

$10.00

Cost of Acclimating PLs (Labor, Feed, Energy)

1000 PLs

$2.61

Juvenile Feed - 600-850 microns

kg

$4.06

Juvenile Feed - 850-1200 microns (kg)

kg

$3.04

Juvenile Feed - No. 3 Crumble (kg)

kg

$0.58

40% Protein Grower - 3/32 "

kg

$0.32

35% Protein Grower - 1/8"

kg

$0.29

man-hour

$8.22

Manager's salary (including fringe)

$/year

$47,950

Electricity

kw-hrs

$0.08

Propane

gallon

$0.62

Diesel Fuel

gal

$1.00

Gasoline

gal

$1.10

month

$500

$/$ Capital

$0.05

$/Crop

$25

Ice & Packing ($/kg shrimp harvested)

kg

$0.10

Marketing ($/kg shrimp harvested)

kg

$0.10

Shipping & Sales ($/kg shrimp harvested)

kg

$0.10

Accounting Fees

kg

$0.05

Legal Fees

kg

$0.05

Insurance

kg

$0.01

Labor (Hourly Wage + Fringe)

Office Rental Maintenance & Repairs Operating Supplies ($/crop)

Contingency Rate

% of Operating Costs

10%

of acclimated postlarvae. The Th e use of artificial substrates may help reduce mortality during the acclimation period. Assuming a survival from initial stocking to final harvest of 61%, 24,480 freshwater acclimated postlarvae will be required per crop to yield a harvest density of 135 shrimp/m2. A total of 28,800 postlarvae (PL8) will need to be purchased per crop, assuming 85% survival of the postlarvae through the acclimation process. After Year 4, when all 12 greenhouses are in operation, the annual requirement for postlarvae (PL8) is estimated at just over 4.1 million postlarvae (Table 10-8). Assuming a seed cost of $10/1000 postlarvae, and an annual demand of 4.1 million postlarvae, the annual seed cost would be approximately $41,000, or $52,300 if the feed, salt and labor costs for for acclimating the postlarvae are included. This represents 17.4% of the total operating cost for the facility.

- 192 -


Table 10-10: Feed Table for Intensive Shrimp Production in Raceways Feed Type

Initial Size (g)

Final Size (g)

600-850 850-1200 No. 3 Crumble 3/32 - 40% 3/32 - 35% 3/32 - 35%

0.005 0.08 0.2 0.9 1.5 8.2

0.08 0.20 0.9 1.5 8.2 18.1

Production Phase Nursery Nursery Nursery Nursery Intermediate Final

Feed Rate (%BW/day) 35%-18% 18%-11% 10%-7.5% 7.5%-6.5% 6.5%-2.5% 2.5%-1.5%

Kg Feed/Crop 2.5 5 29 25 227 269

Feed

Table 10-10 summarizes the feed requirements for producing a crop of shrimp. A variety of feeds are required to raise the shrimp from postlarvae to harvest size (Chapter 7). During the nursery phase, three different feeds are required. The shrimp are initially fed a 50% protein postlarval diet (600-850 microns) for a period of approximately 5 days. The feed rate declines from an initial 35% of bodyweight/day to 18% bodyweight/day. The shrimp are then transitioned to a similar diet but with a larger particle size size (850-1200 microns). The shrimp receive this diet for 6-7 days. When the shrimp reach a size of approximately 0.2 g/shrimp they are transitioned to a No. 3 crumble crumble (1200-1800 microns). The crumble feed typically has a protein content of about 40%. The shrimp remain remain on the crumble for about 1 2 /2 weeks until they reach a size of about 0.8 grams/shrimp. grams/shrimp. At this point they are transitioned to a 3/32" 40% protein pelleted feed. The shrimp remain on this diet until the end of Phase I. In Phase II and Phase III the shrimp are fed a 35% protein grower diet at a rate beginning at 6.5% of their bodyweight per day, and declining to 1.5% of their bodyweight per day by the end of the the growout period. The cumulative feed feed conversion ratio for the entire growout process is expected to to be about 1.76. Table 10-10 summarizes the feeding regimes used in the production process. The 600-850 micron ($8.94/kg) and 850-1200 micron ($6.70/kg) juvenile diets are quite expensive, but only small amounts of these diets diets are required. The No. 3 crumble ($1.28/kg) is also used sparingly. The feeds that are used in the greatest quantity are the 40% protein 3/32" pellets ($0.70/kg) and the 35% protein 1/8" pellets ($0.65/kg). All prices given are delivered prices. Annual feed costs are expected to total $61,265 dollars for 12 greenhouses during Years 410. This represents 20.4% of total operating expenditures. Feed costs tend to be volatile, with prices fluctuating according to the prices of raw ingredients. Feed costs could go up if if the price of fishmeal, soybean meal, and other key ingredients go up. The percentage of operating expenses represented by feed will also be sensitive to feed conversion rates. Feed

- 193 -


conversion ratios are assumed to average 1.76. Feed conversion averaged 1.74 in the 1999 HBOI/FDACS intensive shrimp growout demonstration tanks. Labor

It is assumed that that one laborer is required for every four greenhouses. Hourly workers are paid a wage of $6.00/hour plus 37% fringe. The cost to the business is $8.22/hour. One new hourly worker is hired in each of the building years years (Years 1-3). The model assumes that the owner of the facility will also operate and manage the facility. The owner-operator will not draw a salary but will be paid out of the proceeds from shrimp sales after all other expenses are paid. After Year 4, labor costs account for about 17.1% of all operating costs. Energy

Annual electrical consumption for a 12-greenhouse production facility is summarized by type of equipment item in Table 10-11. Total annual energy cost for the 12-greenhouse facility is approximately $55,400, or $4,617 per greenhouse. There are three categories of energy consumption in the production process. Electricity is used to power pumps, blowers, fans and lights. Propane is used to heat the greenhouses. Gasoline is used by the company pickup truck and to power the generator for the backup blower. The facility will use approximately 413,500 kw-hrs of electrical energy for twelve greenhouses, resulting in an annual electric bill of about $33,000 (assuming electricity costs $0.08/kw-hr). The electrical consumption by the 3/4-hp raceway pumps, which run 24 hours/day, 365 days per year accounts for 44% of the total total usage. The blowers, which also run continuously, account for another 38% of the electrical consumption. Electricity accounts for 11% of the total annual operating budget. Propane-powered gas heaters are used to heat the greenhouses during 6 months out of the year, with almost 95% of the consumption-taking place in the months of December, January, February and March. In similar similar 30’ x 152’ greenhouses at HBOI equipped with propane Table 10-11: Expected electrical consumption for a 12-greenhouse shrimp production facility. HP

Watts

Hours/ Day

No. of Units

Days in Operation

Kwhrs/Year

Annual Cost

3

3000

4

2

365

8,760

$701

0.25

250

4

2

365

730

$58

2

2000

4

2

365

5,840

$467

Sump Pump

0.5

500

4

2

365

1,460

$117

Regenerative Blower

3.5

3500

24

6

365

183,960

$14,717

Raceway Pump

0.75

750

24

24

365

157,680

$12,614

Extractor Fan

1.5

1500

4

24

200

28,800

$2,304

3

3000

24

1

365

26,280

$2,102

Equipment Items Well Pump Degasser Blower Water Supply Pump

Air Conditioner

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heaters, about 3,000 gallons of propane are required per greenhouse per year to maintain system water temperatures of above 26°C. Based on this figure, figure, the total annual propane use for a twelve-greenhouse facility facility would be about 36,000 gallons of propane. Assuming that propane costs $0.62/gallon, the annual cost for heating the facility is about $22,300. This corresponds to 7.4% of the total annual operating cost for the facility. Gasoline is primarily required required for a multi-purpose pickup truck. The pickup is used to transport shrimp to markets, as well as for general usage. It is expected that the pickup truck will travel approximately 40,000 miles per year, and will get about 15 miles per gallon. Annually, the pickup truck truck will use more more than 2,600 gallons of gasoline. At $1.10/gallon of gasoline, this corresponds to almost $3,000 dollars per year. A small amount of gasoline is used by the gasoline-powered backup blower. Maintenance

It is assumed that repairs and maintenance of equipment and facilities will be 4% of the replacement value of all items in the capital inventory (excluding land). In a typical year the the cost of repairs and maintenance is expected to be $26,959, or 9% of the annual operating budget.

Marketing Assumptions The model assumes that the shrimp produced will be direct-marketed as a whole, fresh product. The product will be sold directly to area seafood brokers, seafood markets, supermarkets, and/or restaurants. Preliminary analysis indicated that the cost of production of shrimp in tank-based recirculation systems is too high to allow the shrimp to be profitably sold on the wholesale frozen tail market. While little little hard data exists on the potential for direct-marketing fresh, whole shrimp, entrepreneurs investigating this kind of enterprise have Table 10-12: Current shrimp prices (June 12, 1999) for wholesale and direct-marketed fresh shrimp, assuming a 150% mark-up factor for the fresh, directmarketed product. Average Shrimp Wt (Min)

Average Shrimp Wt. (Max)

Category

Wholesale Price/lb (Heads-on)

Direct Price/lb (Heads-on)

10.3

11.9

61-70

$3.30

$4.95

$2.08

$3.12

12.0

14.2

51-60

$3.50

$5.25

$2.21

$3.31

14.3

17.9

41-50

$4.55

$6.83

$2.87

$4.30

18.0

20.5

36-40

$5.55

$8.33

$3.50

$5.24

20.6

23.9

31-35

$6.25

$9.38

$3.94

$5.91

24.0

28.7

26-30

$7.15

$10.73

$4.50

$6.76

28.8

35.9

21-25

$8.15

$12.23

$5.13

$7.70

36.0

46.4

16-20

$9.95

$14.93

$6.27

$9.40

46.5

72.1

U-15

$10.85

$16.28

$6.84

$10.25

Wholesale Direct Price/lb Price/lb (Tails) (Tails)

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reported that they would be able to consistently sell heads-on 18 gram shrimp (36-40 tail count per pound) for $6.00 a pound. The current wholesale market market price for frozen, headsoff, farm-raised Litopenaeus vannamei in the 36-40 count size category is $5.55/lb. Assuming the tail is 63% of the whole shrimp, this corresponds to a price of $3.50/lb for the whole shrimp (see Table 10-12). A price of $6.00/lb represents a 71% markup, relative to the wholesale price. For this analysis it is assumed that the direct market price for whole, fresh, shrimp is 50% above the wholesale who lesale price for frozen shrimp of the same size. Revenues

Once all twelve greenhouses are in production, a total of 144 crops per year will be harvested, yielding 85,800 pounds of whole shrimp. Assuming these shrimp are sold directly as a whole, fresh product, and the average price received is $5.24/lb, annual revenues are expected to be approximately $449,600 per year.

Cash Flow A cash flow analysis was performed to assess the future cash inflows and outflows over the 10-year planning horizon (Table 10-13). All revenues are assumed to come from shrimp sales. Old equipment that is replaced is assumed assumed to have zero salvage value. Total Operating Expenses are calculated by adding the various categories of operating expenses, including seed costs, feed costs, labor costs, fuel and electrical costs, operating supplies, maintenance, marketing, marketing, packing, shipping, accounting and legal fees. A contingency cost is included to cover miscellaneous items not accounted for in the other categories. The contingency cost is 10% of the other budgeted operating costs. Total operating expense s increase in Years 1-4 as new greenhouses are put into production. After Year 3 Total Operating Expenses level out at approximately $300,400 per year, based on the assumptions of the model. The breakeven price required to cover operating costs in the typical year is $3.50/lb (heads-on).

Year 1 is the only year of the project for which Income – Operating Expenses is negative (– $33,208). Year 1 is a building year and shrimp sales do not begin until August in that year. year. Years 2 and 3 are also building years, but revenues from the production from existing greenhouses is more than enough to cover all operating expenses in these years. Income – years, Operating Expenses is $26,343 in Year 2, and $78,927 in Year 3. In subsequent years, Income- Operating Expenses averages $149,246 per year. Total Cash Outflow is calculated by adding together Total Operating Expenses, Total Capital Investment , and Total Taxes (Income + Social Security). Cash Available at the end of each year is calculated by adding the Total Cash Inflow to the Beginning Cash Balance and subtracting from that total the Total Cash Inflow. At the end of each year a minimum of$30,000 must be carried over to the next year as a Beginning Cash Balance. If the calculated amount of cash available is less than $30,000, then the investor(s) will need to pay the difference.

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The Ending Cash Balance is calculated by adding the Investor Paid-In Capital to the Cash Available. For the purposes of this analysis, analysis, it is assumed assumed that bank financing is not available due to the newness of the technology and the inherent high risk associated with recirculating aquaculture systems. Investor capital will have to be paid into the enterprise in each of the first three years, but after Year 3 all cash expenses can be paid out of revenues from shrimp sales. Investor Paid-in Capital totals $275,234 in Year 1, $133,683 in Year 2, and $73,922 in Year 3. In the last seven seven years of the project the average net income after operating expenses and capital replacement costs have been taken out is $118,893 per year. After income taxes have been taken out, the owner-operator will net an average of $91,656 per year. The cash flow analysis shows available cash increasing from year to year by this amount. It is important to note that this amount does not include any cash withdrawals for owner salary and living expenses. The cash available to the operation after family living withdrawals would be significantly lower than the amount indicated in the cash flow analysis. If the owner operator takes a family living withdrawal of $40,000/year, investor paid-in capital would have to be increased by this amount in each of the first three years of the project. In Years 4-10 the available cash for the operation would increase by an average of $51,656/year, rather than $91,656 per year.

Income Statement A pro forma income statement was developed (Table 10-14) to examine the impact of noncash items such as depreciation on net farm income. The straight-line method was used to calculate annual depreciation. The replacement values of all capital assets with the same economic life were summed and the total value was divided by the number of years of useful life for the group. Salvage value was assumed to be zero for all capital items. The annual depreciation value is subtracted from the Net Cash Income (Total Income – Total Cash Expenses). The result is the Net Income Before Taxes. Net Income Before Taxes averages $83,209. This is the basis on which the income tax, social security, and Medicare payments are figured. The Net Income After Taxes shows the profit or loss in a given year. It is a measure of the amount available to the owner-operator for unpaid labor, management, and equity capital used to produce that net farm farm income. The project operates at a loss the first two years, years, but records profits profits thereafter. Once production stabilizes in Year 4 the Net Income After Taxes) averages about $55,972 per year. Note that this value annual profit ( Net Net Revenue = Cash Inflow – Cash Outflow) . is lower than the average annual net revenue ( Net This is due the difference between annual depreciation and annual replacement costs incurred during the time period examined.

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Table 10-14: Pro forma income statement. Item Income: Shrimp Sale of Capital Equipment Total Income Cash Expense: Operating Interest Total Cash Expense Net Cash Income Non Cash Adjustments Depreciation Net Income Before Tax Taxes Income Tax Social Security Medicare Total taxes Net Income Above Taxes

Value Year 1

Value Year 2

Value Year 3

Value Year 4

Value Year 5

Value Year 6

Value Year 7

Value Year 8

Value Year 9

Value Year 10

$43,712 $0 $43,712

$199,833 $0 $199,833

$349,707 $0 $349,707

$449,623 $0 $449,623

$449,623 $0 $449,623

$449,623 $0 $449,623

$449,623 $0 $449,623

$449,623 $0 $449,623

$449,623 $0 $449,623

$449,623 $0 $449,623

$76,920 $0 $76,920 ($33,208)

$173,489 $0 $173,489 $26,343

$270,780 $0 $270,780 $78,927

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$300,377 $0 $300,377 $149,246

$25,402 ($58,610)

$44,362 ($18,019)

$66,037 $12,890

$66,037 $83,209

$66,037 $83,209

$66,037 $83,209

$66,037 $83,209

$66,037 $83,209

$66,037 $83,209

$66,037 $83,209

$0 $0 $0 $0

$0 $0 $0 $0

$1,933 $1,598 $374 $3,906

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

$17,942 $6,882 $2,413 $27,237

($58,610)

($18,019)

$8,984

$55,972

$55,972

$55,972

$55,972

$55,972

$55,972

$55,972

Value Year 2

Value Year 3

Value Year 4

Value Year 5

Value Year 6

Value Year 7

Value Year 8

Value Year 9

Value Year 10

33,109 41,575 41,575

51,676 64,278 65,023

57,324 69,926 75,124

57,324 69,926 75,124

57,324 69,926 75,124

57,324 69,926 75,124

57,324 69,926 75,124

57,324 69,926 75,124

57,324 69,926 75,124

$4.55 $5.71 $5.71

$4.06 $5.05 $5.11

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

$3.50 $4.27 $4.59

Table 10-15: Breakeven analysis. Value Year 1 Breakeven Production (lbs, whole shrimp) To Cover Cash Costs 14,679 To Cover All Costs Before Taxes 19,527 To Cover All Costs Including Taxes 19,527 Breakeven Price ($/lb) To Cover Cash Costs $9.22 To Cover All Costs Before Taxes $12.27 To Cover All Costs Including Taxes $12.27 Item


Breakeven Analysis A breakeven analysis was conducted to determine determine the minimum levels the venture must achieve to cover costs (Table 10-15). There are two types of breakeven analyses. Breakeven production analysis identifies the level of production that achieves zero profit when price and other factors are held constant. Breakeven price analysis identifies the price that must be received to to achieve zero profit when production and other factors are held constant. The breakeven price is a measure of the production cost per pound of shrimp produced. The level of production required to cover all cash costs, assuming shrimp are sold for $5.24/lb whole, and all costs are held constant, is about 57,300 lbs of shrimp, once production levels off in Year 4. About 69,900 lbs must be produced to cover cash costs plus annual depreciation. Just over 75,000 lbs of shrimp must be produced per year to cover all costs, including taxes. The profit that is made is based on the production production in excess of this final figure. In the baseline scenario, the profit margin is based on about 10,700 pounds of production over and above the breakeven production level. The breakeven price of $3.50 is required to cover all cash costs, assuming production of 85,800 pounds of whole shrimp, with costs as indicated in Table 10-13. A price of about $4.28/pound must be received to cover both cash and non-cash costs (depreciation). The breakeven price reveals the high risk of this venture. The breakeven price per pound ($4.28/lb) is for a whole shrimp, which equates to a price of about $6.79/lb for tails. This is 22% above the current current wholesale market price (New York, June, 1999) for 36-40 count frozen tails. Wholesale shrimp prices are volatile and may vary by plus or minus 30-40%. The current price for wholesale shrimp is near a ten-year high. It wouldn't take a very large drop in the price received for the whole, fresh shrimp to make this a money-losing venture. The baseline assumption is that the producer can get a price that is 50% above the market price for frozen tails by selling a whole, fresh shrimp shrimp direct. However, at this time formal formal market studies have not been carried out to establish the relationship between wholesale prices for frozen frozen shrimp and direct direct market prices for fresh shrimp. It is entirely possible that that the products will be seen as substitutes, and the price differential may not be as large as 50%. If there is substitutibility betwen the two products, the price of the fresh shrimp will probably float with the wholesale price of frozen shrimp.

Investment Analysis Another way to examine the profitability of the venture is to look at the Net Present Value (NPV). The NPV of an investment is calculated by summing the present values of the net cash flows that result from an investment, minus the amount of the original investment. The present values of the net cash flows are calculated using a discount rate that corresponds to that which might be earned in the best alternative use of the capital invested in the project. This is the opportunity cost of capital. Six percent, a typical interest rate earned on secure investments such as certificates of deposit, is a figure commonly used to account for the opportunity cost of capital. Because farming farming shrimp shrimp in in high intensity, recirculating

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aquaculture systems is a risky venture, the discount rate used to calculate the NPV must be increased to compensate the investor for the risk factor. Each investor has their their own risk factor depending on their willingness to take on risk. In this analysis the investor's risk factor is set at 20%. The combined discount discount rate necessary to compensate the investor for the opportunity cost of capital and the the risk factor is 26%. If the NPV is greater than zero, then the venture is considered to be an economic success. success. If the NPV equals zero the investor will be indifferent, because the investment will be equivalent to the best alternative use of the money. If the NPV is less than zero, the investor should not invest, because the earnings from the project will not provide adequate compensation for the opportunity cost and risk factor. The internal rate of return (IRR) is another financial measure that is often used to evaluate investments. The internal rate of return is the discount discount rate that makes the net present value of the annual cash flows flows from an investment equal to zero. Taken together, the the NPV and IRR give a good picture of the economic value of an investment. The NPV and IRR were calculated for this project on the net cash flows (Total Operating Expenses - Total Capital Expenditures). Under the baseline set of assumptions, the NPV is – $124,311. The IRR was calculated to be 13%. These values indicate that the earnings from the project of the 10-year planning horizon are not sufficient to compensate the investor for the risk associated with the project. The investor needs to receive an IRR IRR greater than 26% to make it worth the risk of taking the money out of a more secure investment, but in fact only earns 13%.

Sensitivity Analysis Sensitivity analyses were performed to analyze the effects of selected variables on the profitability of the enterprise. These analyses provide information about the values of operating parameters that are required for the enterprise to become profitable. Sensitivity analyses were performed to examine the effects of improving survival and growth. One of the biggest uncertainties facing the producer is the price of shrimp. This is especially true in this situation, where new markets markets must be developed. An analysis was conducted to determine the minimum price the producer can receive and still make an acceptable profit. Survival

The survival rate used in the baseline analysis (61%) was selected based on the average survival rates observed observed in the HBOI/FDACS demonstration tanks. However, higher average survival rates may be possible. In fact, half of the crops harvested in the study had survivals above 75%. Two different production systems (System A and System System B) were tested tested during the demonstration project (see Chapter 4 for a full description of these systems). systems). The survival rates observed in the System A three-phase tanks were consistently low, averaging only 49%, compared to an average survival of 82% in in the System A single-phase single-phase tanks. The majority of the mortality occurred in the nursery section where the tank depth was only 10 inches. The high density in the nursery nursery sections (5,400 shrimp/m3) led to increased rates of

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cannibalism. In the System System B three-phase three-phase study the water depth was nearly double, and water velocities were maintained much higher. These differences differences in system design appeared to reduce the frequency of cannibalism. The survival in this study was 82% after 135 days. The above discussion of the survival rates in the study is included to show that higher survival rates are possible in the system modeled, and that survival rates can be improved with better tank design. Deeper tanks with better water circulation circulation appear to have fewer problems with cannibalism. Although not tested in this study, the use of artificial artificial substrates in the raceways may also increase survival rates. Artificial substrates provide refuges for the shrimp, which may may cut down on cannibalism. In addition, shrimp graze on the periphyton periphyton growing on artificial substrates, substrates, which may significantly improve their growth rates (Jeff Peterson, personal communication). Because there appears to be potential for improved survival rates in these systems, a sensitivity analysis was performed to determine what the economic implications would be of different survival rates in the range between 60% and 75%, holding all other variables constant (Table 10-16). Table 10-16: Sensitivity of net present value and internal rate of return to survival rate, assuming a growout time of 180 days. Financial Measure Net Present Value Internal Rate of Return

60% ($142,281) 11%

Survival Rate 65% 70% ($71,424) $2,833 19% 26%

75% $76,138 33%

Average survivals of 60% and 65% resulted in negative net present values, assuming all other variables are held constant. However, improving the survival to 70% would result in a 26.3% internal rate of return, marginally higher than the 26% rate of return required for investment in the project. If average survival rates can be improved to 75%, the internal rate of return increases to 33%, a very acceptable figure. However, investing in a shrimp culture enterprise based on anticipated survival rates as high as this would be risky. In any aquacultural enterprise, equipment failures, human error, or disease occasionally lead to very low survivals in given crops. These unanticipated events should be taken taken into account in the analysis. Growth Rates

The growth rates observed in the Harbor Branch demonstration system were significantly slower than are commonly recorded for Litopenaeus Litopenaeus vannamei. In pond production systems it typically takes the shrimp 30 days to attain an average weight of 1 gram/shrimp, and thereafter the shrimp increase in size by approximately 1 gram/week. gram/week. At these growth rates 18 gram shrimp may may be harvested after 22 weeks, or 154 days. There are probably several reasons for the relatively slow growth that was observed in the Harbor Branch systems. systems. The

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raceways were not heated, so temperatures were sub-optimal for at least part of each study. Another factor that may have impacted the growth rates was a general lack of algal and detrital food sources for the shrimp in the culture tanks. It is well known that in ponds, L. vannamei grows best in ponds with high levels of natural productivity (Scura, 1995). Phytoplankton and organic detritus are both important components of the shrimp’s diet (Moss, 1992). L. vannamei has a very inefficient digestive system consisting of short, straight gut. Evidence is accumulating that L.vannamei does not utilize prepared diets efficiently, especially if their feces are rapidly filtered from the system. However, if their feces are allowed to remain in the system, heterotrophic bacteria will colonize the fecal material and convert feed feed protein into bacterial protein. Shrimp consume the the decaying fecal material and the associated bacteria. The shrimp derive significant nutritional benefits from the bacterial proteins and partially digested feed proteins during this second pass. The importance of the detrital food chain to shrimp growth was not fully appreciated until this study was nearly over. The culture tanks were shaded to control algae growth, and solid wastes were quickly removed from the system in the interest of maintaining optimal conditions for biofiltration. As a result, the shrimp were almost completely dependent upon the nutrition they could absorb from the prepared feeds in a single pass through the gut. Recent unpublished work at Harbor Branch has demonstrated that the growth rates of shrimp grown in tanks managed for optimization of the detrital detrital food chain have been up to 50% faster than the growth rates observed in the systems modeled in this report. Similarly, Moss (1999) reported growth rates of L.vannamei cultured in a high density tank-based culture system at the Oceanic Institute (OI) in Hawaii that were double the growth rates observed in the HBOI system. The primary difference between the OI system and the HBOI system was that the OI system was a “greenwater” system, while the HBOI system was a “clearwater” system. The presence of algae and organic detritus in the tanks was credited by Moss for the rapid growth rates that were observed in the OI system. system. These results suggest that the mediocre growth rates observed in this study were not strictly a function of the tank environment, or the high densities that were used. Rather, the slow growth may be related to the scarcity of detritus in the the system. Better growth rates might be realized with with alternative management strategies. A sensitivity analysis was carried out to determine what the impact would be of faster growth rates and shorter production cycles on the profitability of the hypothetical enterprise of the model. The net present value and internal rate of return were calculated for growout to an average market size of 18 grams in 150, 159, 168, and 177 days. All other variables were held constant. The results are summarized summarized in Table 10-17. As expected, the profitability of the enterprise is sensitive to shrimp growth rates. The enterprise becomes marginally profitable (NPV = $1,371) if the time required to reach market size is reduced by 21 days (from 180 days to 159 days). If the shrimp shrimp can be grown to market market size in 150 days, the norm for pond culture, then the NPV is strongly positive ($60,314), and the IRR is healthy 32%. These results indicate that even modest modest improvements in growth rates can significantly alter the profit potential for this type of enterprise.

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Table 10-17: Sensitivity analysis of the effects of the time required for shrimp to reach a market size of 18 grams on the net present value and internal rate of return of a hypothetical 12-greenhouse 12-greenhou se shrimp production facility. Item Production Cycle/Year/Tank Production Cycles/Year Baseline Scenario: Survival = 61% Net Present Value (r=26%) Internal Rate of Return

Days Required to Reach 18 grams 159 168 6.76 6.4 162.2 153.7

150 7.16 171.8 $ 60,314 32 %

Alternative Scenario: Survival = 70% Net Present Value (r=26%) $ 216,911 Internal Rate of Return 48 %

177 6.08 146

$ 1,371 26 %

($ 59,413) 20 %

($ 105,761) 15 %

$ 148,134 41 %

$ 78,262 34 %

$ 24,494 28 %

Improved nutrition for the shrimp could conceivably result in both improved growth rates and better survival, especially if well-nourished shrimp engage less frequently in cannibalism. The sensitivity of the NPV and IRR to growth rates was examined examined at a 70% survival rate (Table 10-17). The combination of improved growth and higher higher survival dramatically improves the profit potential of the enterprise. Even with a minimal minimal reduction in the growout time from 180 days to 177 days, the enterprise is marginally profitable if survival averages 70%. Further reductions in the growout growout time time dramatically improve the profit potential of the enterprise. If the shrimp can be grown to an average size of 18 grams in 150 days with a 70% survival rate, the net present value improves to a very attractive $216,911, which corresponds to an IRR of 48%. Seed Costs

Seed costs comprise 17.4% of the total operating cost, following slightly behind feed and energy among the most costly inputs inputs for the enterprise. Seed costs are influenced heavily by two factors: 1) the price charged by hatcheries for the postlarvae, and 2) the survival of the postlarvae through the acclimation/quarantine period. Like most goods, the price of SPF postlarvae will be determined by supply and demand. Currently the supply of SPF postlarvae is extremely limited, with limited numbers being produced by just a few hatcheries. However, the demand for SPF postlarvae is not very great at the moment. At present there is only one commercial SPF hatchery in the state of Florida. The market price (FOB hatchery) is approximately $7.00 per thousand postlarvae. Postlarval shipments can be delivered to most points in Florida for less than $3.00 per thousand postlarvae. If the demand for postlarvae were to increase without a corresponding increase in hatchery production capacity, the price for seed would almost certainly increase significantly. However, if hatchery production increases faster faster than the demand for SPF postlarvae, seed prices could fall to as low as $5.00 per thousand.

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Another important factor affecting the net price paid for seed is the survival of the postlarvae through the acclimation/quarantine period. Cannibalism can be significant in the late postlarval stages. stages. Survival will be a function of density and management. Inadequate frequency of feeding and/or inappropriate feeding rates can result in high rates of cannibalism. Excessive feeding rates and/or inadequate water exchange can result in fouled water and low survivals. A well-managed acclimation acclimation program could average as high as 90% survival, while a less well-managed program could average 70% survival or less through the acclimation period. Unanticipated mortality during the acclimation period is more costly than anticipated mortality mortality if stocking rates rates of production tanks are are affected. If the producer anticipates a survival of 70% through the acclimation period, then additional postlarvae can be purchased and acclimated to ensure that the production tanks are stocked at the desired density. The net effect is only a higher seed cost. However, if the producer bases postlarval purchases on an anticipated 85% acclimation period survival, and only achieves a survival of 70%, the production tanks will be understocked and overall productivity will suffer. A sensitivity analysis was carried out to examine the effect of both postlarval price and acclimation survival rates rates on enterprise profitability. The analysis assumes assumes the acclimation acclimation mortality is compensated for in the number of postlarvae purchased, and production tank stocking density is maintained constant. If we assume that production tank survival averages 61% and the shrimp reach 18 grams after 180 days, no realistic combination of lower seed prices and higher acclimation survival rates resulted in acceptable rates of return for the project. However, if we assume an average survival of 70% in the production tanks, seed costs and acclimation survivals would likely determine the acceptability of the rate of return for the project (Table 10-18). If the price of postlarvae increases to $12 per thousand, the project is unacceptable even if acclimation survival rates are 90%. However, if postlarvae can be purchased for $6.00 per thousand, positive net present values are obtained even if Table 10-18: Sensitivity analysis of the effect of postlarval price and acclimation survival rates on NPV and IRR, assuming production tank survival rates of 70% and a growout period of 180 days. PL Price ($/1000 PLs)

75 %

Acclimation Survival Rates 80 % 85%

90%

$6.00

NPV IRR

$ 16, 968 28 %

$ 34,587 29 %

$ 50,134 31 %

$8.00

NPV IRR

($ 9,836) 25 %

$ 9,459 27 %

$ 26,484 29 %

$ 41,617 30 %

$10.00

NPV IRR

($ 36,640) 22 %

($ 15,670) 24 %

$ 2,833 26 %

$ 19,280 28 %

$12.00

NPV IRR

($ 63,444) 20 %

($ 40, 799) 22 %

($ 20,818) 24 %

($ 3,056) 26 %

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$ 63,953 32 %


acclimation survival drops as low as 75%. At intermediate seed prices, the acclimation survival rates will determine whether or not the net present value of the project is positive or negative. Market Prices

The economic model assumes the the shrimp can be sold head-on for a price price of $5.24/lb, or 50% above the current wholesale price for for a 36-40 count shrimp. A sensitivity analysis was conducted to determine the minimum heads-on price the producer must receive for the shrimp in order for the investment to be an acceptable risk. This was accomplished by determining the product price at which the net present value is equal to zero, using a discount rate of 26% (6% opportunity cost + 20% risk premium). The analysis was carried out for each of four different production tank survival rates and two different growout times (180 days and 150 days). The results are presented in Table 10-19. The baseline scenario for the model assumed that the shrimp can be sold as a whole, headson product for $5.24 per pound. Presently there is insufficient insufficient market information to to know whether or not the product can be sold at that price on a consistent consistent basis. The price used in the baseline scenario is not really an important price to consider. The prices shown in Table 10-19 are much more significant. The breakeven price to cover cash costs is the cost of producing a pound of shrimp shrimp under a given set set of conditions. Production should not even be considered unless this price is virtually guaranteed. The breakeven price for all costs is a measure of the total cost of production per pound of shrimp when depreciation of capital items and income taxes are added to the total operating costs. This is the minimum minimum price that must be received to guarantee that the enterprise will not lose money in the long run. Unless this price can be earned for the shrimp, production will never pay back the capital costs associated with the the project. The minimum economic price is the price at which the net present value is equal to zero under a given set of assumptions regarding production, production costs, and capital costs. This is the the price that must be received to cover the Table 10-19:

Growout Time

180 days

150 days

Sensitivity of breakeven prices and minimimum economic prices to survival and growout time. Survival

Item Breakeven Price (Cash Costs) Breakeven Price (All Costs) Minimum Economic Price (Heads-on) Minimum Economic Price (Heads-off) Percentage of Current Frozen Price Breakeven Price (Cash Costs) Breakeven Price (All Costs) Minimum Economic Price (Heads-on) Minimum Economic Price (Heads-off) Percentage of Current Frozen Price

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60% $3.56 $4.88 $5.98 $9.49 171 % $3.15 $4.22 $5.08 $8.06 146 %

65% $3.35 $4.57 $5.59 $8.87 160 % $2.97 $3.96 $4.76 $7.56 136 %

70% $3.15 $4.28 $5.23 $8.30 150 % $2.79 $3.72 $4.46 $7.08 128 %

75% $2.99 $4.04 $4.93 $7.83 141 % $2.65 $3.51 $4.20 $6.67 120 %


opportunity cost of capital and the risk premium associated with the use of that capital in a non-secure venture. This is the minimum minimum price that must be received for the investor to be indifferent to the investment. Below this price it would be better for investors to leave their money in a secure investment such as a CD or treasury bond. Only if the price is greater than the minimum economic price would it make sense for an investor to consider putting money into the project. For reference, the minimum economic price is computed for for each scenario as a heads-off price (Heads-off price = Heads-on price/lb ÷ 0.63 lb lb tails/lb whole shrimp). The heads-off price is then expressed as a percentage of the current price for frozen 36-40 count shrimp (Fulton Fish Market, June 22, 1999). Note that the minimum minimum economic price (heads-off) is 120% of the current wholesale price for the most favorable scenario (75% survival, 150 day growout time). The percentage of the current frozen price ranges from 120% to 146% for the 150 day growout scenarios, and from 141% to 170% for the 180 day growout scenarios. These figures clearly illustrate the need to market shrimp grown in this kind of production system through direct marketing channels as a premium product. In order for the producer to receive the needed prices, the product must be clearly recognized by the consumer as a unique product, clearly superior to the frozen tails available at much lower prices. Good information is needed on such issues as shelf-life, consumer preferences, and the volume of shrimp that can be sold through direct marketing channels at premium prices.

Conclusion The economic analysis shows that an intensive shrimp production facility will have to achieve better growth rates and survivals than were observed in Harbor Branch’s FDACS shrimp demonstration project in order to be economically feasible. A baseline scenario based on the actual stocking densities, survivals, growth rates and costs obtained during the one year demonstration demonstration project only produced a 13% internal rate of return. However, sensitivity analyses demonstrated that if growth rates can be improved so that the shrimp grow at rates typically observed in ponds, this kind of an enterprise could earn an economic profit. Improving survival rates from from 60% to 70%, holding other variables constant, would also result in economic profitability. If both growth rates and survival can be improved, improved, the economic potential improves dramatically. Economic returns are less sensitive to seed costs, but seed costs could tip the scales one way or the other for scenarios that are marginally profitable. With modifications in the management and/or design of intensive production systems for shrimp, it seems likely that growth rates and survival rates can be improved sufficiently for shrimp production in intensive freshwater recirculating recirculating to become a profitable business. It is strongly recommended, however, that anyone considering this type of enterprise begin on a small scale to demonstrate whether or not the contemplated production system and management regime can, in fact, achieve the required survival, growth rates, and cost structure for the business to succeed.

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The profitability of an intensive shrimp production system such as this requires that the shrimp be sold at prices from 20% to 70% above the current wholesale price for frozen shrimp. The volume of shrimp shrimp that can be sold and the price that can be received through direct marketing channels will depend, in large measure, upon the marketing efforts of the producer. Potential investors should thoroughly research their markets before attempting this type of enterprise.

Literature Cited Moss, S.M. (1999). Biosecure Shrimp Production: Emerging Technologies for a Maturing Industry. Global Aquaculture Advocate 2(4/5): 50-52. Moss, S.M., G.D. Pruder, K.M. K.M. Leber, and J.A. Wyban. 1992. The relative enhancement of Penaeus vannamei growth by selected fractions of shrimp pond water. Aquaculture 101: 229-239. Scura, E.D.. 1995. Dry season production problems on shrimp farms in Central America and the Caribbean Basin. In, C.L. Browdy and J.S. Hopkins, editors. Swimming Through Troubled Waters, Proceedings of the Special Session on Shrimp Farming, Aquaculture ’95. World Aquaculture Society, Baton Rouge, Louisiana. pp. 200-213.

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Appendix A – Ammonia Mass Balance Analysis

Appendix A

AMMONIA MASS BALANCE ANALYSIS

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Ammonia Mass Balance Analysis by Peter Van Wyk Harbor Branch Oceanographic Institution . The required flow rates in a recirculating aquaculture system can be estimating using a process called mass mass balance analysis. analysis. This approach is based on the physical law of conservation of mass, which says that mass cannot be created or destroyed, but only transformed. Losordo (1991) demonstrated how to use this concept to estimate the required flow rates in recirculating aquaculture systems. What follows here is based on Losordo’s mass balance approach for estimating required flow rates. In order to apply the mass balance approach, the following steps must be taken: 1) 2) 3) 4)

The system boundaries must be defined. All flow streams crossing boundaries must be identified as eith input or output. The material to be balanced must be identified. The processes which occur inside the system to transform the material must be identified.

Once these steps have been taken, the mass balance equation can be written: The Rate of Accumulation of Mass Inside the System =

The Rate of Flow of Mass Into the System

The Rate of Flow of Mass + Out of the System

The Net Rate of Transform Transformatio ation n of Mass Within the System

The transformation of mass within the system can result from processes which generate the particular form of the material of interest (ammonia, for example), and from processes that consume that material. Rewriting the mass balance equation to express this idea: (1)

Accumulation =

Input - Output + Generation - Consumption

When applying this analysis to a recirculating system, the system boundaries include the culture tank and the water treatment system, as well as all the plumbing required to make a complete circuit ( Figure 1). Makeup water is a flow crossing this boundary, so any new material entering the system in the makeup water would be considered input. Any material lost from the system in the effluent effluent is considered output. Generation and consumption would result from biological or chemical transformation processes within the system. In a steady state system system there is no net change in the amount of the material in question. question. The accumulation term in Equation (1) is zero. Under these conditions, input plus generation are exactly balanced by output plus consumption: (2)

Input + Generation = Output + Consumption.

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Figure 1: System Diagram for Ammonia Ammonia Mass Balance If we apply the mass balance approach to analyze a particular water quality variable, such as ammonia, we can determine the conditions that will be required to attain a steady state condition with respect to that variable. For example, we will make the assumption that after the system adjusts to a given feed rate and water exchange rate, the ammonia concentration in the system will will settle down to some equilibrium concentration. For design purposes, we want to make sure that when the system is at maximum capacity the equilibrium concentration of ammonia is within acceptable acce ptable limits for the culture species. System Ammonia Mass Balance Ammonia is one of the most critical water quality parameters in nearly all recirculating aquaculture systems. Ammonia is generated within the system as a by-product of protein metabolism. The rate of ammonia generation is a function of the feeding rate. In a clear system (no significant algal biomass), ammonia is consumed by nitrifying bacteria residing largely in the biofilter. The rate of nitrification by these bacteria depends upon the amount of ammonia passing through the biofilter. biofilter. A key design question is “What flow rate will the biofilter require to make sure that the steady state equilibrium concentration of ammonia is within the acceptable limits for the culture species?” species?” To answer this question, we need to be able to express mathematically the input, output, generation, and consumption terms in Equation (2).

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Appendix A – Ammonia Mass Balance Analysis The input of ammonia into the system will be quantity of ammonia entering the system in the makeup water. This is calculated by multiplying the concentration of TAN in the makeup water by the flowrate of makeup water into the system: (3)

Input =

(Q * CTANin)

where, Q CTANin

= =

flow rate of makeup water concentration of TAN in makup water.

The output of ammonia from the system will be the quantity of ammonia exiting the system in the effluent. This is calculated by multiplying the concentration of TAN in the effluent by the effluent flow rate. If the system volume is not changing over time (the system is neither filling up nor being drained), the effluent flow rate will exactly equal the flow rate of makeup water into the system. system. Output can be expressed mathematically as follows: (4)

Output = Q* CTANout

where, Q CTANout

= flow rate of effluent (= flow rate of makeup water) = concentration of TAN in the effluent.

The generation of ammonia within the system is the result of metabolism of the proteins in the feed. The rate of ammonia production is dependent upon the feeding rate, the protein content of the feed, the fraction of protein nitrogen that is excreted as TAN, and the rate of TAN excretion: (5)

P

TAN

=

FA x PC x 0.092 t

where, PTAN FA PC t

= = = =

Rate of Ammonia Production Amount of Feed per Feeding Protein Content of the Feed, expressed as a decimal fraction time in which all of the TAN from a given feeding is excreted.

The number in the formula, 0.092, is the fraction of protein nitrogen that is excreted as TAN. This is calculated by multiplying the fraction of nitrogen in protein (0.16) by the fraction of nitrogen in the feed protein that is assimilated (0.80), the fraction of assimilated nitrogen that is excreted (0.80) and the percentage of excreted nitrogen that is excreted of ammonia (0.092 = 0.16 x 0.8 x 0.8 x 0.9). 0 .9). There are a couple of simplifying assumptions assumptions that are being made here. We are assuming assuming that all of the non-assimilated nitrogen in fecal material is removed rapidly from the tank before the heterotrophic bacteria have time to break down the protein in the feces and excrete more ammonia into the system. system. We also assume that 100% of the TAN is excreted - 212 -

Appendix A – Ammonia Mass Balance Analysis within t hours after a feeding. This assumption assumption requires that the time interval between feedings must be greater than t , the ammonia excretion time. The consumption of ammonia within the system is the rate at which ammonia is converted to nitrite and nitrate within the biofilter. This will be a function function of the the rate at which ammonia enters the biofilter, and the efficiency of the biofilter. The biofilter efficiency is the fraction of TAN removed in one pass through the biofilter. The rate of ammonia removal by the biofilter can be expressed mathematically as: (6)

RTAN = Qf x CTAN x E

where, RTAN Qf CTAN E

= ammonia consumtion rate = flow rate to the biofilter = concentration of ammonia entering the biofilter = ammonia removal efficiency of the biofilter.

Estimating Required Recycle Flow Rates Based on Ammonia Mass Balance If we know the values of the other variables in the mass balance equation, we can calculate the required recycle flow rates by rewriting Equation 2 using the mathematical representations of the input, output, generation and consumption terms, and the solving for the recycle flow rate, Qf . The following equation is Equation 2 expressed in mathematical form:

6)

(Q x CTANou CTANout) t) output

+

(Q x CTAN CTAN x E) f consumption

=

(Q x CTANi CTANin) n) + P TAN input generation

If we know the values of the other variable, we can solve for the recycle flow rate, Q f ., ., by rearranging to express Qf in terms of the other variables: 7)

Qf

=

(Q x CTANin)

+

PTAN - (Q x CTANout)

CTAN x E

In most cases we will have good information about the values of the variables on the right side of Equation 7. Q is the flow rate of makeup water and is typically assumed to produce an exchange rate equivalent of between 5-10% of the system volume per day for most recirculating systems. systems. CTANin is the concentration of ammonia in the makeup water. This value should be zero or close to zero. In some locations the well water comes out of the ground with relatively high levels of ammonia. If this is the case, the water should should be pretreated through a biofilter so that CTANin is as close to zero as possible. possible. PTAN is is dependent on the feed rate (FA), the protein content of the feed (PC), and the ammonia excretion time time (t). For design purposes, FA should be calculated based on the the highest anticipated biomass the system will experience:

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(8)

FA

=

Shrimp Shrimp Biomass Biomass x

Feed Rate (% Bodyweight/Day) Number of Feedings/Day

The protein content of the feed should be known in advance based on published studies and the feed manufacturer’s recommendations. Most diets for shrimp shrimp grown in high density recirculating systems systems contain between 35% and 40% protein. The ammonia excretion time time is approximately 6 hours. The value generally used for CTANout is the maximum value of TAN that the shrimp can tolerate with no appreciable effect on growth or health. Levels of unionized ammonia of greater than 0.03 mg/l begin to affect the physiology physiology of the shrimp. We can use unionized ammonia tables to determine the TAN that would produce the maximum acceptable unionized ammonia ammonia concentration at a specific pH and temperature. temperature. To be conservative, select a pH and temperature combination at the upper end of the expected values for these parameters. For example, at a pH of 8.0 and a temperature of 32°C the fraction of unionized ammonia is 0.075. Under these conditions, the maximum acceptable TAN (CTANout) would be 0.4 mg/liter (0.4 = 0.03/0.075).

The biofilter efficiency, E. is difficult to estimate because biofilter efficiency is a function of many factors, including ammonia concentration, hydraulic loading rate, filter surface area, filter media type, temperature, pH, salinity, alkalinity, DO, TSS, and filter type (submerged, trickling, fluidized bed, etc.). One of the reasons for building a prototype of the production system is to gather information on biofilter performance under different conditions and to determine a reasonable value of E to use in the mass balance analysis. Under normal operating conditions a properly-sized biofilter should remove about 50% of the TAN in the water in a single pass. In fact, the biofilter is not the only place in the system system where nitrification takes place. Up to 30% of the nitrification in a typical recirculation system takes place outside of the biofilter (Losordo, personal communication). Because of this, the method outlined here tends tends to overestimate the required recycle rate by about 30%. However, if the assumption assumption that the fecal wastes are removed immediately is not met, then the amount of ammonia that would need to be removed by the biofilter would be higher. It may well be that these two error factors in the calculation balance out. This is likely to be the case in a system which accumulates solid wastes for 12-24 hours between backwashes. Example:

Assume we have a 50,000 liter recirculating aquaculture system with a maximum biomass of 0.05 lbs/gallon (0.006 kg/liter). These shrimp will will be fed a 35% protein feed at a rate of 2% of their bodyweight per day in four four equal feedings 6 hours apart. Water will be exchanged at a rate of 5% of the system volume per day. The makeup water contains 0.1 mg/l mg/l ammonia nitrogen. The biofilter will have an efficiency of 50% (50% of the TAN will be converted to nitrate in a single pass). pa ss). - 214 -


What should the recycle flow rate be to maintain the total ammonia nitrogen at a value less than or equal to 0.4 mg/l ? Step 1: Calculate the weight of feed per feeding and the rate of production of total ammonianitrogen (PTAN ). Maximum biomass

= 50,000 liter x 0.006 kg/liter = 300 kg of shrimp

FA

= (300 kg shrimp x .02 kg feed/kg shrimp) / (4 feedings/day) = 1.5 kg feed per feeding 6

PTAN

1.5 kg feed/feeding x 0.35 x 0.092 x 10 mg / kg

=

6 hrs =

Step 2:

8,050 mg TAN/hr

Calculate flowrate (Q) of makeup water and wastewater:

Makeup water

= 5% of System Volume/day x System Volume (liters) =

.05/day x 50,000 liters x 1day/24 1d ay/24 hours

=

2,500 liters/day x 1 day/24 hours

=

104 liters/hour

Step 3: Calculate recycle flow rate rate using Equation (7): Eq. (7): Qf = (Q x CTANin + PTAN - Q x CTANout ) / (CTAN x E ) Q = 104 liters/hour (from Step 2) CTANin = 0.1mg TAN/liter (given) PTAN = 8,050 mg TAN/hour ( from Step 1) CTANout = CTAN = 0.4 mg TAN/liter (by assumption) E = 50% (by assumption) Qf

= ( (104 l/hr x 0.1 mg TAN/l) + 8,050 mg TAN/hr - (104 l/hr x 0.4 mg TAN/l) ) / ( 0.4 mg/l * 0.50 ) =

(10.4 mg TAN/hr + 8,050 mg TAN/hr TAN/hr - 41.6mg TAN/hr) / 0. 20 mg TAN/liter

= 40,094 liters/hour

(176.5 gpm)

This corresponds to one turnover every 1.25 hours, or every 75 minutes. - 215 -


Literature Cited: Losordo, T.M.. 1991. An introduction to recirculating production systems design. In, M.B. Timmons and T.M. Losordo, (eds.) Engineering (eds.) Engineering Aspects of Intensive Aquaculture. Proceedings from the Aquaculture Symposium, Cornell University, April 4-6, 1991. Northeast Regional Agricultural Engineering Service, Ithaca , New York. NRAES – 49, pp. 32-47.

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APPENDIX B FRICTION LOSS TABLES

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218

219

220

Farming Marine Shrimp in Recirculating Freshwater Systems

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