FAO Shrimp Culture_ Pond Design, Operation and Management

P r o d u c e d b y : Fisheries and Aquaculture Department

T i t l e : Shrimp culture: pond design, operation and management... More details

SHRIMP CULTURE: POND DESIGN, OPERATION AND MANAGEMENT

TABLE OF CONTENT

N A CA CA T r a i n i n g M a n u a l S e r i e s N o . 2 SHRIMP CULTU RE: POND DESIGN, DESIGN, OPERATION OPERATION AND MA NAGEMENT P. Kungvankij and T.E. Chua Food and Agriculture Agriculture Organization Organization of the United Nations Nations (FAO) and B.J. Pudadera, Jr.

L.B. Tiro, Jr.

G. Corre

I.O. Potestas

E. Borlongan

G. A. Taleon

Alava

J. N. Paw

Aquaculture Department, Southeast Asian Fisheries Development Center N e t w o r k o f A q u a c u l t u r e C e n t r e s i n A s i a (N ( N A CA CA ) R e g i o n a l L e a d C e n t r e i n t h e P h i l i p p i n e s ( RL R L C P) P) June 1986 The designation designation employed and the presentation presentation of material material in this publication do not imply the expression expression of any opinion whatsoever whatsoever on the part of the Food and Agriculture Agriculture Organization Organization of the United Nations/UND Nations/UNDP P nor SEAFDEC SEAFDEC AQD. concerning concerning the legal status of any country, territory, city or area of its authorities, authorities, or concerning concerning the delimination delimination of its frontiers frontiers or boundaries. boundaries.

NOT ICE OF COP COPYRI YRI GHT The copyright in this publication publication is vested in the Food and Agriculture Agriculture Organization Organization of the United Nations. Nations. This publication publication may not be reproduced reproduced in whole or in part, by any method or process, process, without written written permission from the copyright holder. Application for such permission with a statement of the purpose and extent of the repro duction desired, should be made through and addressed to the Coordinator, Coordinator, Network of Aquaculture Centres in Asia (NACA), (NACA), UNDP, P.O. Box 618, Bangkok, Bangkok, Thailand

FOREWORD This publication publication is one of a series published specifically specifically to commemorate commemorate the WORLD FOOD DAY 1986 by the Network of Aquaculture Centres in Asia (NACA), a regional project of the Food and Agriculture Agriculture Organization Organization (FAO) of the United Nations and the United Nations Development Development Programme (UNDP). (UNDP). It is the Asian component of the global network of aquaculture aquaculture centres established and coordinated coordinated through the FAO/UNDP FAO/UNDP inter-regional inter -regional project, Aquaculture Aquaculture Development Development and Coordination Coordination Programme Programme (ADCP). (ADCP). FAO has been observing observing World Food Day on 16 October for the past five consecutive consecutive years, in an effort to increase public awareness of the problems of hunger and malnutrition. malnutrition. The impact of this celebration celebration is globally globally felt, and 16 October has become an important date in the national national calendar of activities of almost all Member Countries Countries of FAO. It provides an excellent excellent opportunity for making better known what FAO is, what it has done since its foundation, and the challenges challenges it faces in helping to resolve resolve the problems of hunger. The theme adopted for this year's celebration is “FISHERMEN and FISHING COMMUNITIES”, including including aquaculture, aquaculture, and NACA is participating participating in the celebration through a series of publications publications and video productions productions on fish farming systems and technologies technologies developed in Asia. The role of aquaculture aquaculture in the improvement of nutrition and socio-econom socio -economic ic conditions of the fish farming communities communities in the rural and coastal coastal regions cannot be over emphasized. emphasized. In fact, rediscovery rediscovery of aquaculture aquaculture in Asia may provide hope for the rural poor, particularly particularly as an option to the displaced displaced fishermen fishermen and fishing fishing communities of the region, for whom the culture of finish, shellfish and other aquatic organisms ranks among those occupations occupations which have the greater potential of contributing contributing to diets and higher income with the least disruption of their traditional lifestyle. lifestyle. However, transfer of technological technological innovations innovations to them for adoption appears to be one of the most important important constraints in changing changing their traditional methods of farming. As such bringing together the art and science science of such innovations innovations in the form of a publication publication or a video for the benefit of the fishermen, fishing community, fish farmers and extension workers, is one of the major NACA activities. activities. It is therefore, befitting to bring out this publication publication as the World Food Day 1986 Commemorative Commemorative Issue. This provides the package of practices practices of the farming system based on synthesis synthesis of the practical practical work done by the authors and blended with the observations observations made by others in this field. On behalf of NACA, I would like to thank the national staff staff and the project staff in bringing out this material.

CHEN Foo Yan NACA Coordinator Coordinator

Hyperlinks Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibilit responsibility y for the opinions, opinions, ideas, data or products products presented at these locations, locations, or guarantee guarantee the validity validity of the information information provided. provided. The sole purpose of links to non-FAO sites is to indicate indicate further information available on related topics. This electronic document has been scanned using optical character character recognition (OCR) software. software. FAO declines all responsibilit responsibility y for any discrepancies discrepancies that may exist between the present document and its original printed version.

TABLE OF CONTENT 1. Introduction 2. Pond Culture 2.1 Traditional or extensive shrimp farming 2.2 Improved traditional or semi-intensive farming 2.3 Intensive farming

FOREWORD This publication publication is one of a series published specifically specifically to commemorate commemorate the WORLD FOOD DAY 1986 by the Network of Aquaculture Centres in Asia (NACA), a regional project of the Food and Agriculture Agriculture Organization Organization (FAO) of the United Nations and the United Nations Development Development Programme (UNDP). (UNDP). It is the Asian component of the global network of aquaculture aquaculture centres established and coordinated coordinated through the FAO/UNDP FAO/UNDP inter-regional inter -regional project, Aquaculture Aquaculture Development Development and Coordination Coordination Programme Programme (ADCP). (ADCP). FAO has been observing observing World Food Day on 16 October for the past five consecutive consecutive years, in an effort to increase public awareness of the problems of hunger and malnutrition. malnutrition. The impact of this celebration celebration is globally globally felt, and 16 October has become an important date in the national national calendar of activities of almost all Member Countries Countries of FAO. It provides an excellent excellent opportunity for making better known what FAO is, what it has done since its foundation, and the challenges challenges it faces in helping to resolve resolve the problems of hunger. The theme adopted for this year's celebration is “FISHERMEN and FISHING COMMUNITIES”, including including aquaculture, aquaculture, and NACA is participating participating in the celebration through a series of publications publications and video productions productions on fish farming systems and technologies technologies developed in Asia. The role of aquaculture aquaculture in the improvement of nutrition and socio-econom socio -economic ic conditions of the fish farming communities communities in the rural and coastal coastal regions cannot be over emphasized. emphasized. In fact, rediscovery rediscovery of aquaculture aquaculture in Asia may provide hope for the rural poor, particularly particularly as an option to the displaced displaced fishermen fishermen and fishing fishing communities of the region, for whom the culture of finish, shellfish and other aquatic organisms ranks among those occupations occupations which have the greater potential of contributing contributing to diets and higher income with the least disruption of their traditional lifestyle. lifestyle. However, transfer of technological technological innovations innovations to them for adoption appears to be one of the most important important constraints in changing changing their traditional methods of farming. As such bringing together the art and science science of such innovations innovations in the form of a publication publication or a video for the benefit of the fishermen, fishing community, fish farmers and extension workers, is one of the major NACA activities. activities. It is therefore, befitting to bring out this publication publication as the World Food Day 1986 Commemorative Commemorative Issue. This provides the package of practices practices of the farming system based on synthesis synthesis of the practical practical work done by the authors and blended with the observations observations made by others in this field. On behalf of NACA, I would like to thank the national staff staff and the project staff in bringing out this material.

CHEN Foo Yan NACA Coordinator Coordinator

Hyperlinks Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibilit responsibility y for the opinions, opinions, ideas, data or products products presented at these locations, locations, or guarantee guarantee the validity validity of the information information provided. provided. The sole purpose of links to non-FAO sites is to indicate indicate further information available on related topics. This electronic document has been scanned using optical character character recognition (OCR) software. software. FAO declines all responsibilit responsibility y for any discrepancies discrepancies that may exist between the present document and its original printed version.

TABLE OF CONTENT 1. Introduction 2. Pond Culture 2.1 Traditional or extensive shrimp farming 2.2 Improved traditional or semi-intensive farming 2.3 Intensive farming

3. Site Selection for Shrimp Culture 3.1 Water quality 3.2 Tidal fluctuations 3.3 Soil 3.4 Topography 3.5 Vegetation 3.6 Source of seed 3.7 Accessibility 3.8 Other factors 4. Species Culture 4.1 Penaeus japonicus and P. orientalis 4.2 P. monodon 4.3 P. indicus and P. merguiensis 4.4 Metapenaeus ensis 5. Pond Design and Construction 5.1 Size and shape of culture ponds 5.2 Dike 5.3 Supply and drainage canal 5.4 Water control gate (sluice type) 6. Pond Preparation 6.1 Soil sampling 6.2 Leaching 6.3 Pond drying 6.4 Tilling 6.5 Control of undesirable species 6.6 Liming 6.7 Fertilization 7. Seed Supply 7.1 Supply of post-larvae from wild stock 7.2 Seed from Hatchery 7.3 Transportation of fry 8. Culture Techniques 8.1 Nursing of fry 8.2 Stocking of fry 8.3 Routine pond management 9. Water Quality Management 9.1 Salinity 9.2 pH 9.3 Dissolved oxygen (DO) 9.4 Nitrogen compound 9.5 Temperature 9.6 Hydrogen sulphide (H 2S) 10. Feeds and Feeding 10.1 Feeding behavior 10.2 Natural food in the pond

10.3 Supplemental feeding 10.4 Feeding method 10.5 Feeding rate and frequency 11. Manipulation of Stocking in Extensive and Semi-intensive Farming 12. Harvesting and Preservation 13. References

LIST OF FIGURES Figure 1. Typical extensive pond in Thailand Figure 2. Typical semi-intensive pond Figure 3. Amakusa-type shrimp farm in Japan Figure 4. Intensive pond Figure 5. Shigueno type intensive culture tank Figure 6. Lay-out of earthen pond with peripheral canal Figure 7. Cross section of dike Figure 8. Sample design of parimeter dike Figure 9. Typical slope of dike Figure 10. A typical wooden gate Figure 11. A reinforced concrete gate Figure 12. Section of gate showing grooves for slabs and screens Figure 13. Scooping of fry in twigs Figure 14. Collection of fry in fry lure Figure 15. Scoop net Figure 16. Push net or scissor net Figure 17. Fry traps Figure 18. Transportation of fry through live tanks Figure 19. Fry transportation of fry in polyethelene bags Figure 20. Nursery pond Figure 21. Nursery cage Figure 22. Feeding tray Figure 23. Selective harvesting net

LIST OF TABLES Table 1. Lime requirement table Table 2. Comparison of organic and inorganic fertilizers

Table 3. Stocking density of shrimp in different culture operations Table 4. Methods of measuring the physico-chemical Table 5. Nutrient composition of natural food organisms



1. Introduct ion Marine shrimp farming is a century-old practice in many Asian countries. Until a decade ago, this commodity was generally considered a secondary crop in traditional fish farming practices. Shrimp fry trapped in salt beds, coastal paddy fields or brackishwater fishponds are allowed to grow to marketable size and harvested as secondary crop. However, in recent years when higher income are derived from the harvest of shrimp than the principal crop, many farmers have converted their rice fields, salt beds and fishponds into shrimp farms. In the traditional farming system, the ponds are stocked with fry either collected from the wild or concentrated through tidal water entering the ponds. Shrimp production is inconsistent and varies from year to year due to the dependence on seasonal supply of fry from the wild. Pond yield is also low (100– 300 kg/ha/ year) because of inefficient control of predators and competitors, full dependence on natural food and inadequate pond depth. Some improvements of the traditional farming methods have been made in the past years. Stocking density of shrimp ponds can be increased through concentration of fry by pumping more tidal water into the pond. Pond depth is increased to minimize fluctuations of environmental parameters. As a result, pond yield has correspondingly increased. However, expansion of the shrimp farming industry is still restricted due to the inconsistency in fry supply. The success in the mass production of hatchery-bred shrimp fry in the 1970's has accelerated shrimp farming development in the region. With improved pond culture techniques, yield from traditional shrimp ponds has been raised to 500–800 kg/ha/year without supplementary feeding. Pond yield can be further increased to 5–10 tons through supplementary feeding and intensive pond management. The long gestation period in the development of shrimp farming practice may be due to inadequate technical and financial inputs to effectively demonstrate its commercial viability. Shrimp farming has now developed into an important export-oriented food industry especially in South Asian countries. The perception of an unlimited market demand, high export price, generation of employment and increase in foreign exchange earnings may have encouraged many countries in the region rich in aquatic resources to place high emphasis on the development of the shrimp culture industry.



2 . Po n d Cu l t u r e S y s t e m Although shrimp farming has been developed for more than a century in Southeast Asia, the main farming operations are still traditional. Such operational practice is characterized by low yield and also relatively low technical and financial inputs. Due to high market demand of products and low acquisition cost of land, these traditional farms are still commercially profitable. Shrimp yield in ponds can be increased by applying modern farming techniques such as intensification of culture operation through regularization of pond size, increase stocking density, employment of aeration, application of formulated feed, etc. This will mean a considerable increase in financial and high technology inputs which most small farmers in the developing countries may not be able to afford.

2 .1 T r a d it i o n a l o r e x t e n s i v e m e t h o d o f c u l t u r e o pe r a t i o n The ponds used in this type of farming system are generally irregular in shapes and sized (3–20 hectares). Usually each pond has a peripheral ditch 10–20 m wide and 30–60 cm deep. In Thailand, the middle portion of the pond is slightly elevated to about 40 cm above the bottom (Fig. 1), while in the Philippines, the pond bottom is entirely flat. Extensive culture operation is considered the simplest culture approach. Seedstock normally come from the wild and supply is season dependent. Shrimp fry found in these farms either gained entrance during water exchange or are intentionally stocked by the farmer with fry collected from the wild. Extensive farming employs very low stocking densities, usually in the range of about 3,000–5,000 fry per hectare. In this grow-out scheme, supplementary feed is not given and water management is by tidal exchange.

Fig. 1. A typical shrimp pond layout in Thailand for extensive farming. In Thailand, Indonesia and Malaysia, shrimp fry are allowed to enter the ponds through the pond gate which are open during rising tide. The gates are then closed as tide recedes. Trapped fry are allowed to grow inside the pond for two months before being harvested. In contrast, shrimp farmers in the Philippines do not rely on natural tidally introduced shrimp seeds but rather they stock their ponds (usually in polyculture with milkfish) with fry collection from the wild. The average stocking density ranges between 2,000 and 5,000 fry per hectare. In both farming approaches, production per unit area is very low.

2 .2 I m p r o v e d t r a d i t i o n a l or s e m i -i n t e n s i v e m e t h o d c u l t u r e operation In this farming method, the improvement over the traditional approach is in the introduction of a systematic pond configuration. The ponds are generally rectangular in shape with size about 1–3 hectares and water depth of 0.80 to 1.2 meters. Each pond has separate inlet and outlet gates to facilitate water exchange, pond preparation and harvesting. A diagonal ditch, 5–10 meters wide and 30– 50 cm deep extending from inlet to outlet is also constructed to facilitate drainage of water and collection of shrimp during harvest (Fig. 2). The ditch also serves as a refuge for the shrimp during sunny day. This method involves higher stocking rates, use of supplementary feed and the implementation of a regular water management scheme. Current practices vary from country to country and within the country. The

typical rate of stocking fry for semi-intensive culture operation varies from 20,000 to 50,000 fry per hectare. Supplementary feed, either formulated or fresh, is given daily in addition to the existing natural food produced through the application of fertilizers. This operation also requires the use of a water pump to facilitate water exchange. While this approach would substantially increase yield per cropping, the use of supplemental feeds entails additional cost which generally accounts for the biggest share in operational expenditure. The culture operation of the Amakusa type shrimp pen in Japan (Fig. 3) can be classified under this method of culture. The pen is an artificial enclosure constructed within shallow bays and intertidal zones for holding and raising shrimps. A rectangular or square vertical wall made of concrete is constructed to a height of 1 meter for holding water during low tide. A wooden frame with nylon netting is set on top of the concrete wall to prevent escape of shrimp and facilitate water exchange during high tide. This culture method takes advantage of the large body of water that is constantly being renewed through tidal fluctuations and by water current. The dimensions of the enclosure range from 2,000 m 2 to 10,000 m 2 with depth of 1.0–1.5 meters. Stocking rate ranges between 20–30 fry per m 2 . Average production is about 300– 400 g/m 2 or about 3–4 tons/ha/year.

Fig. 2. A typical shrimp pond layout in Thailand for Semi-intensive farming.

Fig. 3. Amakusa type shrimp farm in Japan.

2 .3 I n t e n s i v e m e t h o d o f c u l t u r e o p e r at i o n This culture operation is more sophisticated requiring very high financial and technical inputs. The rearing facilities are either earthen ponds or concrete tanks. The distinct features of this culture operation is the complete dependence on hatchery-bred fry, high stocking density, use of formulated feeds, application of aeration to increase dissolved oxygen level in pond water and intensive water management. Sizes of pond or tank vary for 500 m 2 –5,000 m 2 as found in Japan, Taiwan, Philippines and Thailand. Dikes may be of pure earthen material, earth coated with plastic sheets or concrete. Most designs include separate inlet and outlet gates or small water inlets for flow-through purposes. Drain out system is in the form of a centrally located drain pipe, a drain gate (sluice or monk type) or a combination of both (Fig. 4). An excellent intensive method of culture operation for Kuruma shrimp developed by Shigueno has been widely practised in Japan. Culture facilities consist of circular tanks with capacities ranging from 1000 to 2000 tons and average height of 2 meters. A sand substrate covers the tank bottom and water circulation is effected by flow through system (Fig. 5). The shrimps are fed daily with high protein formulated diet. Stocking density ranges from 200–250 per m 2 and average production ranges from 1.5 to 3 tons per crop in 1000 ton tank and about 10–20 tons/ha/year in earthen ponds with concrete dikes.



3 . Si t e Se l e c t i o n f o r Sh r i m p Cu l t u r e The selection of a suitable site always play a major role in shrimp farming. The determination of a site for shrimp farming is made only after through analysis of information on topography, ecosystem, meteorological and socioeconomic conditions in relation to farm design, species compatibility and economic viability. Criteria are herein presented that could serve as guidelines in judging site suitability.

Fig. 4. Pond layout for intensive shrimp farming (earthen pond with Concrete dikes).

Legend: A: Gate value of spray pipe

B: Aeration bubbling tube CROSS SECTION OF CIRCULAR TANK

C: Sand bed D: Cylindrical screen E: Spray pipe F: Gate value of supplying pipe G: Drain pipe

Fig. 5. Shigueno type intensive culture tank.

3 .1 Wa t e r q u a l i t y Water quality includes all the inherent physico-chemical and microbiological characteristics of water. pH is generally considered as one of the most important factors. In any chosen site, the pH of the water preferably range from 7.5 to 8.5. The other equally important chemical characteristic of water is the level of oxygen saturation throughout the water column. Fluctuations in dissolved oxygen level should be predetermined and the oxygen level is preferably not lower than 4 ppm. The water must not be too turbid. Water with very heavy silt load can cause siltation problems in the water supply system, eg., clogging of filter nets or net enclosures and increasing sedimentation at the pond bottom. The water is preferably to be rich in microorganisms. Salinity variation is considered a determinant factor in shrimp production. Optimal level varies from species to species. For instance, the tiger shrimp (Penaeus monodon) grows faster at 15–30 ppt. The white shrimp (P. indicus and P. merguiensis) tolerate higher salinity ranges (25–40 ppt). Ideally, salinity should remain uniform at normal weather and should not drop abruptly during rainy days.

3 .2 T i d a l f l u c t u a t i o n s The tidal characteristics of the proposed site should be known. Knowledge of this parameter is of extreme importance in determining pond bottom elevation of dike, slope ratio and drainage system. Areas best suited for shrimp farming should have moderate tidal fluctuations preferably 2–3 meters. In areas where the tidal range is greater than 4 meters, the site may prove uneconomical to develop or operate as large and high pond dikes will be required. In areas where tidal range is less than one meter, water management will be expensive requiring the use of pumps. A salient point to consider in relation to tidal range is the knowledge of the occurence of highest high and lowest low water levels. This should be known so that the size and height of the perimeter dike can prevent flooding. In addition, direction and strength of water current should be known for provisions on dikes construction to reduce erosion. Lastly, the proposed area must not be adversely affected by any industrial or agricultural pollution.

3.3 Soil The types and texture of the soil of the area should be analyzed before settling on a site for shrimp farming. Soil samples must be taken at random location, preferably up to a depth of 0.5 meter and subjected to physical and chemical tests to determine the acidity, amount of organic load, level of fertility and physical composition. The soil at the proposed site should have enough clay contest. This is to ensure that the ponds constructed will hold water. Good quality dikes are usually built from sandy clay or sandy loam materials which harden and easily compacted. The dikes will not crack in dry weather. Clay-loam or silty-clay loam at pond bottom promotes growth of natural food organisms. Diking materials made of undecomposed plant matter and alluvial sediments should be avoided. Most ponds developed along the coastal areas with dense mangrove vegetation often have acid -sulphate

problem during the first few years of operation. This is due to the accumulation of pyrites (iron sulfide) in coastal soil. Breakdown of pyrites is minimal in submerged soil. During pond construction, the subsoils are dug for dikes and the pond bottom levelled, the pyrites become oxidized producing sulphuric acid which acidifies the soil. The pH of water becomes extremely low and hence affecting water quality and correspondingly reduced natural productivity. Alleviating acid sulphate conditions in ponds requires the use of lime and removal of acid by leaching and flushing.

3 .4 T o p o g r a p h y It is essential to have a detail topography of the selected site for pond design and farm layout. Coastal sites where the slopes run gently towards the sea are easier for pond development requiring less financial inputs since excavation is minimal. Filling and draining of water likewise is easily facilitated by gravity. In areas where the above conditions are not available, the use of mechanical pumps may be resorted. Associated with topography related constraints are the availability of sufficient quantity of soil for dike construction obtained from excavation of ponds or from above ground bunds. It may prove uneconomical if the site to be developed would require diking material to be transported from outside the chosen area.

3 .5 V e g e t a t i o n The type of vegetation in the area can be, to some extend, indicative of physical elevation and soil type. Dominance of the mangrove plants Avicennia spp. is an indication of good and productive soil. Outgrowths of Rhizophora spp. which are usually characterized by dense prop root systems usually signifies soil types that are coarse and acidic. It is of primary importance to consider density of shrubs at the site. These have to be cleared first before any land development can take place. Clearing operation can add up to the capital outlay.

3 .6 S o u r c e o f s e e d Close proximity of the site to the fry ground is advantageous in that the animals being collected for stocking are not subjected to too much transport and handling stress.

3 .7 A c c e s s i b i l i t y Accessibility is an important consideration in site selection. Overhead cost and delay in the transport of materials and products can be minimized.

3 .8 O t h e r f a c t o r s Adequate consideration should be given to a number of farm related matters such as the availability and quality of labor, peace and order situation or the area concerned, availability and source of electricity and water supply, marketing channels and facilities. The availability of technical assistance near the site is another advantage if a site is chosen near an aquaculture research institution.



4 . Sp e c i e s S e l e c t i o n The shrimp species cultured in Asian countries belong to two genera (Penaeus and Metapenaeus) of the family Penaeidae. Among the dozen species cultured, Penaeus monodon, P. japonicus, P. merguiensis, P. indicus, P. orientalis and Metapenaeus ensis are the more important ones.

4 .1 P e n a e u s j a p o n i c u s a n d P . o r i e n t a l i s The aquafarming techniques of P. japonicus have been well established in Japan and Taiwan. The spawners are readily obtained in large numbers from the wild. The shrimp is hardy and can withstand handling. The survival rate of adult shrimp for long distance transportation is high. However, the species cannot tolerate low salinity and high temperature. P. japonicus prefers sandy bottom in grow-out ponds and grow fasts in high protein (about 60%) diet feed. The other temperate species, P. orientalis which is being cultured commercially in China and Korea, has a single pronounced spawning season in spring. Since both are temperate species, the period of hatchery operation is limited to the warmer seasons only.

4 .2 P e n a e u s m o n o d o n Known as tiger or jumbo shrimp, P. monodon is the most common species in Southeast Asian countries. It is one of the fastest growing species among the various shrimps tested for culture. In pond conditions, shrimp fry of about 1 g in weight grow to a size of 75–100 g in five months at a stocking density of 5,000 per hectare. Some were able to grow them to 25 g in 16 weeks in tanks stocked at 15/m 2 ; others grew them to 42 g in 210 days in earthen pond and to 35 g in three months in tanks stocked at 15/m 2 . The tiger shrimp is a euryhaline species and grows well in salinities ranging from 15 to 30 ppt. It is hardy and not readily stressed by handling. Presently, the major supply of fry is still from the wild but the supply is sparse. Although several hatcheries have been established notably in the Philippines. Taiwan and Thailand, fry production is not consistent due to the full dependence on spawners caught from the wild. Until broodstock in captive condition can be made to mature and spawn, hatchery production of this species still has to depend on wild supply of spawners.

4 .3 P e n a e u s i n d i c u s a n d P. m e r g u i e n s i s The biological characteristics of both species are generally the same. Many fish farmers are not able to distinguish the two species from each other. There are behavioral differences which help easy distinction. P. indicus prefers sandy bottom and is difficult to harvest by draining the pond while P. merguiensis is found most frequently in ponds with muddy bottoms moving out of the pond readily when water is drained. Gravid females of these species are easily obtained in large quantities from the wild. They can also mature in captivity. The larvae are more easily raised than those of P. monodon. However, the larvae are less hardy than other species, the juveniles and adults cannot withstand rough handling. Large quantities of fry can be obtained from natural spawning grounds. The growth rate in pond is relatively fast, reaching 12–15 g within the first three months of culture.

4 .4 M e t a p e n a e u s e n s i s The species is very tolerant to low salinity (5–30 ppt) and high temperature (25–45°C). Fry are abundant in natural spawning ground and their survival rate in the ponds is usually high. This shrimp usually does not grow to a large size and has a low market price compared to other species. They are largely

produced from trapping ponds or as secondary species of shrimp farms.



5 . Po n d De s i g n a n d Co n s t r u c t i o n There is no standard design for a shrimp rearing pond. Present day farming practices still heavily rely on the experience of individual farmers, financial capability and the environmental condition prevailing at the site. A shrimp pond from the engineering view point is essential an improved finfish culture pond. The improved structural design is largely due to the behavior of the Penaeid shrimps. P monodon is a benthic animal and it has a habit of gathering along tank walls. Any design to increase the wall surface eg. adding substrates or an elevated earthen platform extending along the edges of a pond, can promote high stocking densities. An ideal shrimp farm is a complex establishment consisting of: (a) various size ponds for nursery and grow-out, (b) water control structures including embankments, supply and drainage canals and sluice gates, and (c) support facilities such as roads, bridges, living quarters, workshops and warehouses, etc. Careful layout of the described facilities and appropriate structural design in relation to the physical features of the area ensure smooth and effective operational management.

5 .1 S i ze a n d s h a p e o f c u l t u r e p o n d s Rectangular or square pond are appropriate for shrimp culture. The longest axis of a pond should be parallel to the prevailing wind direction. This facilitates water movement generated by wind action thereby increasing dissolved oxygen in the water and minimizing water temperature fluctuations in summer or warmer months. The breadth of a pond depends largely on the purpose and the operational system employed. The following are the various sizes recommended: 500 to 1,000 m2

Nursery pond Grow-out pond

- intensive

0.25 to 1.0 ha

- semi-intensive

0.5 to 2.0 ha

- extensive

1.0 to 10 ha

The rearing pond must have a minimum depth of 1.0 meter. Most traditional brackishwater ponds for shrimp farming are relatively shallow. To satisfy depth requirement, a ditch is constructed along the dike or a central canal between two opposite sides of the pond. The average depth is 1.0 – 1.2 meters (Fig. 6) and depth of the platform is 30–60 cm. Such pond design with peripheral ditches and central platform affords several benefits: a. The ditch provide better living conditions during hot weather. b. The shallow, centrally located platform serves as growing area for the natural food organisms. c. The ditch also serves as harvesting canal. Pond bottom should be as even as possible; free from projecting rocks and tree stumps. The bottom must have a gradual slope from the inlet gate towards the drainage gate. The suggested ratio of the slope is 1:500.

5 . 2 Di k e s Dikes do not only serve as boundaries to indicate pond size and shape but also function to hold water within the pond as well as protecting other farm facilities from flood. Diking materials must preferably be tested for load bearing capabilities and compactibility. In some cases where the quality of the soil is inferior for diking, other materials, viz: concrete or clay must be used as core materials to be placed at the pond bottom (Fig. 7). Design and construction of embankment must be based on sound engineering principles and economic feasibility. A typical design of perimeter dikes facing the sea or a river is shown in Fig. 8.

Fig. 6. Layout of earthen pond with peripheral canal. 5.2.1 Height of dike Coastal soil used as diking material usually shrinks initially. As such, the height of perimeter dike should have a free board of 0.6–0.7 meter above the desired water depth. Free board allowance is determined from the occurence and frequency of flood levels over a period from 5–15 years at the farm site. To compute for the height of dike, the following formula could be used:

Where H

=

height of designed dike

Hw

=

highest high water level from past record

G

=

ground level over mean sea level

FB

=

height of free board

%

=

percent shrinkage

To give a concrete example, let us assume that a proposed shrimp farm has a ground elevation of 1.0 meter above mean sea level and normal high tide of 2 meters. Previous records indicate that the highest tide occuring every 10 years is 2.8 meters. The rate of soil shrinkage after the embankment have been consolidated is 20% and the estimated free board allowed is 0.60 meter. Height of dike is then calculated from the formula:

H

=

3 meters

5.2.2 Slope The slope of perimeter dike is maintained at an average ratio of 2:1 to 3:1. Very often, external slopes are made at a ratio of 2.5:1 to 3:1. Dikes with steep slopes are always subjected to erosion and require higher maintenance cost (Fig. 9). Slope of a dike also highly depends on soil quality. For good clay soil, the recommended slopes are: 1:2 when dike height is above 4.26 m and exposed to wave action; 1:1 when dike is less than 4.26 and the tidal range is greater than 2 meters; 2:1 when the tidal range is 1.0 m or less and the dike height is less than 1.0 meter. The crown of the dike between ponds should be 1–5 meters. It would be advantageous if fast growing grass species are planted on the dikes to control soil erosion.

Fig. 7. Cross section of dike A. The dike constructed with entirely impervious material B. The dike with trench or core

Fig. 8. Sample design of perimeter dike

Fig 9. Typical slope of dike.

5 .3 S u p p l y a n d d r a i n a g e c a n a l Not all shrimp farms are located close to the coast or estuaries. For those that are located far away from the water sources, it is necessary to construct supply and drainage canals. Conceptually, a shrimp pond must possess separate canals for drainage and supply and for avoiding probable contamination of the water supply. Both supply and drainage canals would likewise serve as water level control in the pond and as temporary holding areas for shrimps. It is important that the siting

of the canal systems takes advantage of the natural waterways within the proposed site. Dimensions of supply and drainage canals are calculated by using the following equation: Q = AV Where: Q

=

volume of water discharge

A

=

cross- sectional area of the canal

V

=

velocity of water flow

V value can be calculated by the following formula: V = R ⅔ × S ½ × 1/n where: R

=

depth of water flow

S

=

canal bed gradient

n

=

coefficient of roughness (0.02)

Example 1 Assume that R = 1.25 m S

=

1/5000

then V

=

[1.25]⅔ × [1/5000]½ × 1/0.02

V

=

0.82 m/sec

Example 2 Assume that the pond is 50 ha with an average depth of 1.0 meter and that 10 hours is required to drain the water completely; then volume of water discharge/second

= 13.89 m 3 /sec from the equation Q = AV

= 16.94 m 2 The width of the canal can then be calculated from the equation: A = R (b + 2R) Slope of the canal is 1:2, R = 1.25 Substituting 16.9 = 1.25 (b + 2 × 1.25)

= 11.02 m Therefore, for a pond farm covering 50 hectares, width of the canal at the bedline should be 11.0 meters.

5 .4 Wa t e r c o n t r o l g a t e ( s lu i c e t y p e ) When designing a sluice gate, it is essential to consider tidal fluctuations and gravity in order to ensure effective control of the inflow and outflow of water within a given period of time. The water gates are classified according to function as main (primary) gate or secondary gate. Main gates are strategically situated at the perimeter and are usually constructed of reinforced concrete. These are the main structure controlling the quantity of water for distribution to the shrimp farm. Irrespective of the material to be used to construct the water gates (eg., wood, reinforced concrete, ferrocement), the following requirements should be met (Fig. 10, 11): a. a gate should have adequate capacity for the required amount of water to be taken in or drained out; b. a gate should be constructed in a position that water can be totally discharged; c. a gate should have sufficient grooves for placement of filter screens, slabs and harvest nets; d. a gate should be firmly placed at the pond bottom and properly linked with the dikes to prevent seepage and possible collapse. A standard gate design consists of tide stern wing, side walls and bed structure. The side walls are often designed in accordance with the slope of the earthen dike. Grooves for slabs are usually set at the inner side of the gate (Fig. 12). The size of the gate is based on the total water requirement of a pond. Water intake volume is calculated using the equation: Q = CA [2g(H - h)] ½ where: Q = rate of flow (m/sec) C = cross section of the flux (calculated by multiplying the width of gate opening and its depth) A = coefficient of discharge (0.61) g = gravitational constant (9.8 m/sec 2 )

Fig. 10. A typical wooden gate.

Fig. 11. A reinforced concrete gate H

=

tidal level of the river or sea

w

=

water level in the canal or pond

A more detailed discussion on this topic is adequately covered by the works of Katch (1980) and dela Cruz (1983) (See Section 13).



6 . Po n d Pr e p a r a t i o n In any earthen pond culture system, the bottom soil play a major role in pond yield. High organic matter content in neutral soil often promotes higher primary productivity and hence higher fish yield. Natural food organisms are one of the most important food sources in ponds. It is rich in protein, vitamins, minerals and other essential growth elements that simple supplementary feed cannot complete. Fish yield in pond can also be affected by the presence of predators, deteriorating water quality and improper pond management. Hence, pond preparation is a first step towards ensuring a better pond production. Shrimp culture operation in Asia can be grouped into three major categories: a. Those that depend entirely on natural food (extensive culture); b. Those that depend on both natural food and supplementary feeds (improved extensive and semiintensive culture; c. Those that depend entirely on artificial diet (intensive culture). Irrespective of the culture operation used, it is always advisable to prepare the ponds in sustaining high natural productivity throughout the culture period.

6 .1 S o i l s a m p l i n g Prior to pond preparation, soil samples are collected from the pond bottom and the dikes for pH and organic matter contents analysis. Soil pH analysis is generally conducted to determine lime requirement. This procedure is important for newly developed ponds where the occurence of acid sulphate soils is common. When acidic soil condition is detected, corrective measures can be incorporated in the pond preparation activities. Sampling of soil is not necessary for well conditioned ponds. Collection of samples must be done on wet or moist soil using soil augur or an improvised sampler made of bamboo or PVC pipe. About 12 subsamples in an S-shaped pattern should be taken in a one hectare pond. Only the top soil (0–15 cm) is sampled. Stones, rubbish and coarse particles should be removed before taking the soil samples. The subsamples are mixed thoroughly and a representative portion is taken and labelled accordingly. This representative portion is then air-dried by spreading thinly on plastic sheet and protected from direct sunlight, wind and dust. The dried soil is then packed in labelled plastic bag and send for analysis to the nearest soil laboratory. Request for result interpretation may be included when submitting samples for analysis.

F i g. 1 2 . Se c t i o n o f g a t e s h o w i n g g r o o v e s f o r s l a b s a n d s c r e e n In most soil laboratories, it usually takes one to two weeks before the result can be given. Thus for routine soil pH determination, the shrimp farmer can take upon himself to do the analysis using a pH meter. To prepare for the analysis, the air-dried soil sample must be pulverized using a wooden mallet or mortar and pestle. It is then passed through a 2-mm mesh sieve and stored in a properly labelled bag or glass jar. The sample is ready for pH determination (see Section 6.6.3).

6 .2 L e a c h i n g When the pond soil is found to be acidic, it is normally “leached. This is done by flushing and washing the pond bottom with water to leach away undesirable metallic compounds like aluminum, iron and excess sulfur ions.

6 . 3 Po n d d r y i n g The drying of the pond bottom is the most practicl cheap and effective method of eliminating undesirable species in pond prior to the culture period. Drying oxidizes harmful chemical substances especially sulfides and facilitates mineralization of organic matter. The pond is dried until the soil cracks or when it is firm enough to hold one's weight without sinking more than 5 cm on walking over the surface. During the process of drying the ponds, other activities must be undertaken. These include repair of dikes and gates, reconditioning of pond bottom trench, levelling, installation of screens and substrates. Substrate installation such as twigs or coconut fronds at the pond bottom are very important in the first

few weeks of culture because the juveniles have the habit of clinging on vertical surfaces. Aside from that, substrates also serve other purposes: (i) provide additional surface area for some benthic food organisms, (ii) provide shelter against direct sunlight, and (iii) reduce mortality of shrimp juveniles from predators.

6 .4 T i l l i n g Tilling or ploughing of bottom soil improves soil quality by exposing subsoil to the atmosphere thereby speeding up the oxidation process and the release of nutrients that are locked in the soil.

6 .5 Co n t r o l o f u n d e s i r a b l e s p e c i e s Undersirable species which are pests, competitors and predators consist of finfishes, crustaceans, molluscs, reptiles, amphibians, birds and mammals. Pests are species that generally do not have direct harmful effects on the cultured stock. In most cases, however, pests are also competitors. Some pests for example are certain species of crabs that burrow into the dikes. These can destroy the dikes and cause leakages which may allow the entrance of undesirable species or the escape of cultured stock especially in nursery ponds. Others are wood borers and barnacles. Competitors are species that compete for space, food, oxygen, etc. with the cultured stock. Generally, these are of different species. Competition arises out of the similarity in environmental demands which can pose limitations in the culturd species development. Both intraspecific and interspecific competitions prevail in any shrimp pond. It is essential to minimize such competition by adequate management procedures in stocking of shrimp fry and prevention of undesirable species from entering the pond. Predatory species on the other hand, are species that prey on the culturd stock. These species include snakes, birds, finfishes, amphibians, crustaceans and mammals. The presence of predators is a serious problem for shrimp growers especially in nursery ponds. Predators are generally, but not always, larger than the culture animals. In some predatory finfishes for instance, there are a number of distinct structural features such as the head is about 30% of the body length and the horizontal width of the mouth opening is about 40–50% of the head length against 16–24% in non-predatory fishes. The capability of the predators to capture their preys is affected by size, density, general behavior (eg., escape instincts), color and structure of the preys. 6.5.1 Important undesirable species in shrimp pond (a) Finfishes Predatory finfishes are especially destructive to juveniles. The more voracious ones are seabass (Lates calcarifer) and ten pounder (Elops hawaiiensis). Other common predatory species include tilapia, thread fin bream (Polynemus sp.) and Therapon sp. which are very harmful to shrimp larvae. Finfishes that compete for food and space with the cultured stock are mullet (Mugil sp.) mud skipper (Periophthalmus sp.), clupeiods sp. and Leiognathus sp. (b) Crustaceans Crabs are one of the worst predators and competitors in ponds causing heavy damage to the stock. Their dike boring activities are the major causes of water leakage in ponds. (c) Molluscs Some snails compete for natural food in the pond. The occurence of snails in shrimp ponds appears to coincide with soft shelling in shrimps. (d) Amphibians Frogs are considered the most common amphibian predator. The adult frogs are harmful when present in sufficient numbers.

(e) Reptiles Water snakes predate directly on shrimp larvae and adults and are therefore extremely harmful when present in sufficient numbers. (f) Birds There are a number of wading birds which cause serious problems in shrimp farms such as the kingfisher and grey heron. The grey heron can swallow a whole prey of 15–20 cm in size. These birds are especially harmful when the shrimps concentrate in the surface or other shallow areas providing opportunity for these aerial predators. (8) Mammals The lower mammals such as otter often destroy their preys more than predates. The animal usually causes serious damages in a shrimp farm by killing shrimps as they enter the pond. 6.5.2 Methods in controlling undesirable species in shrimp pond There are two usual methods used in controlling undesirable species in shrimp ponds - physical and chemical methods. a. Physical method - The most effective method in this category is drying the ponds. Other methods include installation of appropriate screens in the oulet/inlet gates to prevent entrance of undesirable species, proper maintenance of dikes and water gates to prevent leakage and to eradicate boring organisms like crabs ans snakes and setting up traps and bird-scaring devices like strings of colored cloth streching across the surface of the pond to scare predatory birds. During the culture period, selective harvesting or the use of cast net can be resorted to minimize the impact of undesirable species. b. Chemical method - Eradication of undesirable species is very effective, less cumbersome, efficient and fast when using chemicals. This is because chemicals act as contact or systemic poison. There are several types of chemicals used and collectively are known as pesticides. The use of organic pesticides such as Aquatin, Brestan, Endrin, etc., is not recommended in shrimp farming because these have residual effects which destroy the fertility of the ponds as well as being non-selective or broad-spectrum compounds in terms of biocidal activity. In selecting pesticides, plant-extracted compounds are recommended because these are biodegradable and in most cases contribute to the fertility of the fertility of the pond soil. The commonly used pesticides are: i. Rotenone - This chemical which is extracted from grounded Derris sp. roots has been used as piscicide for centuries in South America. It is a selective poison affecting readily the finfishes but not the shrimps at certain concentrations. Commercial rotenone is in powder form containing 4–5% rotenone. Effective dosage for commercial rotenone is 2 g/m 3 for common predators and 8 g/m 3 for eel. Crude rotenone can be extracted from Derris plant by cutting the root into small pieces, crushed and soaked overnight in water. The crushed roots are squeezed to obtain as much extract as possible. The extract is then added to the pond at the rate of 4 g of dry root/m 3 of water. Fresh derris root is more effective than the dry one. ii. Saponin - It is extracted from tea seed cake which is a residue from oil processing of Camellia sp. seed. It contains 10–15% saponin. Saponin is widely used to eradicate finfishes without toxic effect on crustaceans especially shrimps. The effectiveness of saponin decreases with decreasing salinity. The recommended levels of application are 12 and 20 g/m 3 for salinities above and below 15 ppt, respectively. Saponin is used in shrimp farms in Thailand, Malaysia, Singapore and Taiwan even during the rearing period because of its piscicide activity. iii. Calcium carbide - It is applied into the crab hole and enough water is poured in the hole to activate the calcium carbide which kills the crab.

iv. Tobacco dust - Nicotine is the potent principle in tobacco dust and is non-selective type of poison. Since this is toxic even to shrimp, it is generally applied during pond preparation activities. The pond should be flushed well before stocking. A dosage of 200 kg/ha is used to kill undesirable species especially snails which will take about six months before the population re-establishes. v. Ammonium sulphate - This chemical compound which is also a fertilizer (21-0-0) is effective in eradicating undesirable species when used in combination with lime. The toxicant is ammonia which is released from the reaction of ammonium sulphate with lime. This chemical is applied together with lime during pond preparation at the undrainable portions of the pond at a dosage of 1 part of ammonium sulphate to 5 parts of lime. Lime must preferably be applied first to raise the pH since the rapid release of ammonia from ammonium sulphate is dependent on high pH (above 8.0).

6 .6 L i m i n g Liming is the application of calcium and magnesium compounds to the soil for the purpose of reducing soil acidity. It is usually applied during or after the pond drying stage. 6.6.1 Action of liming The favorable actions of liming are: (a) kills most microorganisms especially parasites due to its caustic reaction, (b) raised pH of acidic water to neutral or slightly alkaline value, (c) increases the alkaline reserve in water and mud which prevents extreme changes in pH, (d) neutralizes the harmful action of certain substances like sulfides and acids, (e) promotes biological productivity since it enhances the breakdown of organic substances by bacteria creating a more favorable oxygen and carbon reserves, (f) precipitates suspended or soluble organic materials, decreases biological oxygen demand (BOD), increases light penetration, enhances nitrification due to the requirement of calcium by nitrifying organisms, and (g) indirectly improves fine-textured bottom soil in the presence of organic matter. Excessive liming, however, can be damaging because it decreases phosphorus availability through precipitation of insoluble calcium or magnesium phosphate. 6.6.2 Liming substances The chemicals used for liming of soils are the oxides, hydroxides and silicates of calcium or magnesium since these are the ones capable of reducing acidity. Typical liming substances are the following: (a) Calcium oxide, CaO This is the only compound to which the term lime may be correctly applied. Calcium oxide is variously known as unslated lime, burnt lime and quicklime. It is manufactured by roasting calcitic limestone in a furnace. Calcium oxide is caustic and hygroscopic and is sold commercially in powder and granular forms. (b) Calcium hydroxide, Ca(OH) 2 Calcium hydroxide is known as flaked lime, hydrated lime or builder's lime. It is prepared by hydrating calcium oxide. It sold commercially in powder or granular forms. (c) Calcium, CaCo 3 and mixed calcium-magnesium carbonate, [CaMg (CO 3)2] The carbonates occur widely in nature. Among the common forms that can be utilized as liming substances are calcitic limestone which is a pure calcium carbonate and dolomitic limestone which is a calcium-magnesium carbonate with varying proportions of calcium and magnesium. Commercial calcium carbonate is known as agricultural lime. The carbonates are the least reactive of the three liming substances. 6.6.3 Determination of lime requirement There are several methods used for the determination of lime requirement in ponds. One of these is the Boyd's method which is relatively easy to perform. The procedure is as follows:

Weight 20 g of the seived soil sample in 100 ml glass beaker and add 20 ml of distilled water. Stir intermittently for one hour. Measure the pH of the above solution with a pH meter previously standardized and record the reading. Add 20 ml of p-nitrophenol buffer to the above solution and stir intermittently for 20 minutes. Prior to reading its pH, set the pH meter to pH 8.0 with 1:1 mixture of the p-nitrophenol buffer and distilled water. Read the pH of the soil sample (buffer/distilled water mixture) while stirring vigorously. Use the values of the soil sample pH in distilled water and soil sample in buffered solution to obtain the liming rate from Table 1. If the pH of the soil in the buffered solution is below 7, repeat the analysis with 10 g of soil sample and double the liming rate from Table 1. Table 1. Lime requirement in kg/ha of calcium carbonate (neutralizing value of 100) to increase total hardness and total alkalinity of pond water above 20 mg/L Mud pH in brffered solution Mud pH in water

7.9

7.8

7.7

7.6

7.5

7.4

7.3

7.2

7.1

7.0

(kg/ha of calcium carbonate required) 5.7

121

242

363

484

605

726

847

968

1 089

1 210

5.6

168

336

504

672

840

1 008

1 176

1 344

1 512

1 680

5.5

269

538

806

1 075

1 344

1 613

1 881

2 150

2 419

2 688

5.4

386

773

1 159

1 546

1 932

2 318

2 705

3 091

3 478

3 864

5.3

454

907

1 361

1 814

2 268

2 722

3 175

3 629

4 082

4 536

5.2

521

1 042

1 562

2 083

2 064

3 125

3 646

4 166

4 687

5 208

5.1

588

1 176

1 764

2 353

2 940

3 528

4 116

4 704

5 292

5 880

5.0

672

1 344

2 016

2 688

3 360

4 032

4 704

5 376

6 048

6 720

4.9

874

1 747

2 621

3 494

4 368

5 242

6 115

6 989

7 974

8 736

4.8

896

1 792

2 688

3 584

4 480

5 376

6 272

7 186

8 064

8 960

4.7

941

1 882

2 822

3 763

4 704

5 645

6 586

7 526

8 467

9 408

Source: Boyd 1979

To prepare a p-nitrophenol buffer of pH 8.0. Dilute 20 g para-nitrophenol, 15 g boric acid, 75 g potassium hydroxide in one liter of distilled water. Make sure that the chemicals used are all reagent grade. Check the pH using a standardized pH meter and adjust to the right pH by adding 7.5% potassium hydroxide (7.5 g/100 ml distilled water) or 1.5% boric acid (1.5 g/100 ml distilled water). Use medicine droppers to dispense the solutions. Refrigerate the buffer while not in use. It will last indefinitely. Care must be exercised in the use of p-nitrophenol as it is toxic and reportedly carcinogenic. Potassium hydroxide is very caustic and should be handled with care. As a rule, never handle the chemicals with bare hands and flush with plenty of water should contact occur. Generally, the liming material used in ponds is calcium oxide. It is therefore necessary to convert the liming rate to calcium oxide value by multiplying the above rate with 0.56. 6.6.4 Methods of liming Liming can be done in three different ways:

by broadcast over dried pond which includes the dike walls. by mixing with water and spraying over the pond, and by liming the water flowing into the pond. In general, any one of these methods may be employed. Certain cases, however, demand the application of a particular method. In using the first two methods, lime should be spread as uniformly as possible over the complete surface of the pond or pond water. Liming the pond water is usually carried out with the use of flat boat. The third method is uncommonly practicec although it saves the labor in spreading.

6 .7 Fe r t i l i za t i o n One usual way of increasing carrying capacity of a shrimp pond is to improve its natural fertility through the addition of organic or inorganic fertilizers. Pond fertilization is an important and necessary step in extensive and semi-intensive methods of farming operations. (a) Organic fertilizers The most common fertilizers are animal manures, rice bran, compost and sewage. Application of organic fertilizers especially in newly developed ponds is advisable because it serves as soil conditioner. The advantages and disadvantages of organic fertilizers are listed in Table 2. The rate of application for shrimp ponds ranges from 500 to 2,000 kg/ha. (b) Inorganic fertilizers Inorganic fertilizers are synthetic fertilizers that generally contain concentrated amount of at least one of the major plant nutrients like nitrogen, phosphorus and potassium. These major nutrients are expressed on a percentage by weight basis. Nitrogen is expressed at %N and phosphorus as % Phosphorus oxide (P2O5). Commercially available inorganic fertilizers are usually sold with such trade names as 16–20-0 (16%N-20%P 2O5 -0%K 2 O), 14-14-14 (14%N-14% P 2O5 -14%K 2O), 45-0-0 (urea). The rate of application ranges from 25 to 100 kg/ha during pond preparation.



7. Seed Supply Shrimp fry are generally collected from the wild. However, substantial number can be supplied through shrimp hatcheries.

7 .1 Su p p l y o f p o s t - la r v a e f r om w i l d s t o c k Natural abundant supply of naturally occuring post-larvae of Penaeid shrimp in many tropical/ subtropical Asian countries has supported a large number of shrimp farms in the region. About 80% of the small shrimp farmers still depend on wild fry for culture. Fry are collected either through trapping ponds or from natural fry grounds. 7.1.1 Trapping pond Natural stocks of shrimp larvae are carried into brackishwater ponds by the rising tide when the pond gates are opened. When the tide starts to recede, the gates are closed and the shrimp seeds are thus trapped. The fry are allowed to grow for about two months before being harvested. Some progressive shrimp farmers use mechanical pumps to concentrate the number of larvae in the pond, hence, increasing the stocking density. A major problem faced by this practice is that many undesirable organisms also enter the pond with the shrimp fry. Table 2. Comparison of Organic and Inorganic Fertilizers for use in Brackishwater Ponds. ITEM

Concentration of N and P

ORGANIC

INORGANIC

Low. Average N ranges from 0.5% to 1.1% while P ranges from 0.1% to 0.4%.

High. For 18–46-0 fertilizer, it contains 18% N and 46% P or 35 times more than the organic fertilizer.

Variable. N and P concentrations depend on diet composition given Composition of nutrients as N and to the producing animal. Nutrients P concentration diminishes through prolong storage or exposure to the elements.

Consistent.

Substrate for micro-benthos attachment

Does provide.

Does not provide.

Processing, storage and transport including application

High cost in terms of money, labor Low cost in terms of money, facilities and general labor, facilities and minimal unpleasantness is greater than general unpleasantness. inorganic fertilizers.

Adverse effect on cultured stock

Mortality of stock commonly due to breakdown by microbial organisms leading to high BOD and low dissolved oxygen in the water.

Rare.

Present. Enhances algal production.

Absent.

Growth factors

Cost per unit of total N and P nutrients

Most expensive. Requires large amount to attain high N and P level.

Lest expensive since N and P are in concentrated amount. Application requires only smaller dose as compared to organic fertilizers.

Feeds for the cultured stock

Can be used directly such as rice bran and chicken manure especialy for species low in the food chain.

Cannot be consumed by aquatic animals.

7.1.2 Collection of wild fry Many methods are employed in collecting shrimp fry. In the Philippines and Indonesia, shrimp fry are usually collected together with milkfish fry. However, due to increasing demand and high cost of fry, a number of efficient gears have been developed. The various fry collecting devices currently being used include: a. Twig - Small bunches of twigs are suspended close to or placed on the bottom of shallow lagoons, esturies and protected coasts. The shrimp fry are collected during low tide by placing a scoop net under each bunch of twighs as it is lifted up (Fig. 13). b. Fry lure - Lure lines are made of saltwater grass. These are usually set along the banks of beaches and rivers (Fig. 14). Each line is 20 meters long and supported on both ends. Shrimp is collected as it is lifted up to the surface. c. Scoop nets - In areas where there are abundance of aquatic weeds, a scoop net can be used to collect shrimp fry which usually cling to weeds (Fig. 15) d. Push or scissor nets - The nets are with or without cod end. These are used along the beach, lagoons, bays, near shore and in estuaries which can be operated by hand or boat (Fig. 16). e. Fry traps - This stationary gear consists of a wing and a collecting chamber. The cod-end of the collecting chamber is kept afloat by bamboo raft and the wing is fixed with bamboo poles against the incoming water (Fig. 17).

7 .2 S e ed f r o m h a t c h e r y Shrimp hatchery has become an important supply source for fry. Some hatcheries can produced shrimp fry all year round as long as spawners are available. An added advantage is that hatchery-bred fry of the same age are almost uniform in size and can be produced in large quantities at any one time. At 15–21 days old, the fry are ready for stocking in ponds. Although wild fry are ready for stocking in ponds. is inconsistent. The hatchery, therefore, is a more reliable seed source.

Fig. 14. Fry lure

Fig. 13. Twig

Fig. 1 5 . Scoop net

Fig. 1 6 . Push net or scissors net

Operation of scissors net.

Fig. 1 7 . Fry trap

7 .3 T r a n s p o rt a t i o n o f f r y There are many ways to transport shrimp fry from hatchery or the wild to nursery or rearing ponds. a. In fry tanks - Fry can be transported in plastic, fiberglass or canvass tanks at a density of 500– 1000/liter with aeration (Fig. 18). Temperature of water can be lowered by means of ice in floating plastic bags. Shrimp fry at densities of 200–5000/ liter can be transported for 10 hours without heavy mortality. b. Plastic bags - Very often, shrimp fry are transported in polyethelene bags with oxygen (Fig. 19). The bag (60×40 cm) is first filled with 6–8 liters of fresh seawater and then packed with 3000–5000 fry. The density may be reduced if the expected transport time is longer. After properly tightening the mouths of the bags, these are placed in styrofoam boxes or plastic buckets. Water temperature is reduced to about 22–25°C by crushed ice mixed with sawdust on the bottom, side and top of the styrofoam box. Under this condition, the fry may be kept alive for more than 12 hours during transportation.



8 . Gr o w -o u t The success of shrimp farming is measured by its rate of return on investment which mainly depends upon the yield, capital investment, market price and the production cost. This in turn is affected by a number of factors the most important of which are farm operation and management.

8 .1 N u r s i n g o f f r y Fry mortality often occurs during the initial period of stocking in ponds. Stress by handling, transportation and acclimation are among the main causes. Hence, young fry of size 0.5–1.0 g are first stocking in nursery ponds for about one month to 45 days before being transferred to grow -out ponds.

Fig. 1 8 . Transportion of fry in tanks.

Fig. 1 9 . Fry transportation in polyethylene bags Nursing of fry can be done either in concrete tank, nursery pond or in net cages installed in deeper ponds or in rivers. 8.1.1 Concrete tank The tanks are first filled with filtered sea water. The water is aerated. Pure culture of diatoms is then added to maintain water quality and for reducing water transparency. Suggested stocking density is about 5000 fry/m 3 of water for P. monodon, 10,000/m 3 for P. indicus and P. merguiensis. It is advisable to use artificial substrates such as polyethelene netting to increase surface area in the nursery tank since postlarvae habitually cling to wall surfaces and tank bottom. The fry are fed with finely chopped mussel or cockle meat. Newly stocked fry are often provided with Artemia nauplii to minimize cannibalism. Young and adult Artemia may also be used to supplement the diet. 50% of the water is changed daily. Flow-through system is used to ensure good water quality for growth and survival. 8.1.2 Nursery pond The size of nursery pond ranges from 500 to 2,000 m 2 with water depth of 40–70 cm. Each nursery pond has at least one gate installed with a fine screen (1 mm mesh size) to prevent undesirable organisms from entering the pond as well as to prevent the escape of stocks (Fig. 20). Stocking density in nursery pond is about 50–150 fry/m 3 depending on the size of the fry.

The nursery pond should be adequately prepared prior to stocking. The pond is completely drained of water and dried until bottom soil cracks. Derris root at 4 g/m 3 will be applied when the pond cannot be completely drained. Lime at 500 to 2,000 kg/ha, chicken manure at 500 to 2,000 kg and inorganic fertilizer (16–20-0) at 25 to 100 kg/ha are then applied.

Fig. 2 0 . Nursery pond About 30% of the water is changed daily. If the pond is not heavily stocked i.e., less than 5/m 2 , water exchange during rising tide may be sufficient. Chopped mussel or cockled meat are fed to the larvae at the rate of 20% total biomass. The nursing period is 30–45 days or when the larvae reached 0.2–1.0 g body weight. 8.1.3 Nursery cages Synthetic net cages (0.5–1.0 mm mesh size) installed within bamboo or wooden frames are kept afloat by bamboo raft or synthetic floats. The cages can be used to nurse shrimp larvae. Nursery cages are mostly employed in calm water such as river, lagoon or fishpond. The cage (3 m 3 ) is usually stocked at 1000– 2000 fry/m 3 of water. The feeding scheme is similar to that being used in earthen pond nursery (Fig. 21).

8 .2 S t o c k i n g o f f r y Optimization of pond yield largely depends on how the ponds are stocked and the operational management thereafter. Stocking of fry is an important operational function. Optimum stocking density depends on the stocking size, natural mortality, pond productivity and culture systems used. 8.2.1 Acclimation Shrimp fry are very sensitive to abrupt change in environmental conditions such as temperature and salinity. Long duration of transportation always increase water temperature of the containers with shrimp fry. Fry should therefore be acclimated to the pond conditions before being released into the rearing ponds. Shrimp fry are acclimated to pond water condition by gradually mixing container water with water from the pond. Alternatively, plastic bags containing the shrimp fry are allowed to float in the pond until water temperature stabilized and then release to the pond slowly. 8.2.2 Stocking time The fry should be stocked preferably in the early morning (0700–1000 hours) or late in the evening (2100–2400 hours) when the pond water temperature is low.

Fig. 2 1 . Nursery cage 8.2.3 Stocking rate The decision on how many shrimp fry a pond should be stocked depends on the carrying capacity of the pond as well as the required harvesting size. The latter is a decision based on economic returns. The basic principle is that pond capacity should be optimized to produce the best economic returns. Optimal stocking density can be determined based on field experiments. Example optimal stocking density for Penaeus monodon culture using extensive method of culture operation. Stocking density (ind.m 2 )

Production (kg/ha)

Harvesting size (g)

Growth rate (g/day)

Yield (kg/ha/day)

1

305

35

0.29

2.9

2

405

30

0.25

5.0

4

560

15

0.116

4.6

It is apparent that stocking density at 2/m 2 gives maximum yield as well as best economic returns considering the preferred harvesting size (30–35 g) for export as well as domestic markets. However, in intensive method of culture operation which depends entirely on artificial feeds and intensive water management, a higher stocking density can be achieved within the limit of pond carrying capacity. The general formula for calculating stocking density is as follows: STOCKING - EXPECTED YIELD (G) (NUMBER)

INDIVIDUAL GROWTH RATE

EXPECTED MORTALITY

Example. If a shrimp farm for P. monodon has a target yield of 1200 kg/ha/crop, expected average body weight is 30 g, and expected survival rate of about 70%, the stocking density is calculated as follows:

The normal stocking density used in difference culture operation systems in shown in Table 3. Table 3. Stocking density of shrimp in different culture Extensive Species P. monodon

Semi-Intensive

Intensive

(× 10 3 individuals/ha) 5–10

20–50

50–300

P. indicus P. merguiensis P. japonicus

10–50 30–100

80–100 100–300

100–500 300–2,500

8 .3 R o u t i n e p o n d m a n a g e m e n t After initial stocking, routine checking of pond conditions should be done every morning to monitor for physico-chemical parameters, physical condition of embankment, water supply and drainage canal, occurence of undesirable species as well as the behavior of cultured stocks. The early morning hours are critical for monitoring oxygen regime of pond water. It is also important to inspect the feeding trays to verify that the feed given the previous day were consumed. If the feeds were not fully consumed, the possible explanation should be found and feeding rate adjusted accordingly. 8.3.1 Water management Frequent change of pond water is needed to maintain water quality. The process also helps to introduce new food organisms into the pond and stimulate molting of shrimp. In stagnant water, decomposition of accumulated organic wastes or depletion of trace metals may affect shrimp growth. The water in the pond can be changed through tidal flows or by means of a mechanical pump. Tidal exchange of pond water is normally practiced in traditional shrimp farm. Water in the pond is drained to one half of the pond level during low tide and is replenished during rising tide. The exchange is only effected within 5– 7 days during spring tide. Pond fertilization has to take place after the last day of the water exchange cycle. Water pumps of various capacities are used to replenish pond water in semi-intensive and intensive culture operations. For semi-intensive culture method, the pump is used only during neap tide while tidal water facilitates exchange during spring tide. About 50% of pond water is changed during each replenishment. For intensive culture methods, frequent changes are essential to remove or reduce water contamination due to decomposition of uneaten food and also to maintain the pond oxygen levels in pond water. hence, water at the pond bottom should be replace during each change of water. Quality of water can be effectively maintained in intensive culture method by changing ⅓ of the pond water daily or adopting a flow-through system. Water analysis kits are field equipment commonly used for monitoring the physico-chemical parameters of pond water. These kits give relatively accurate results, comparatively inexpensive, compact and handy. The kits are easy to use and permit rapid reliable analysis for aquaculture purposes. The most important variables requiring constant monitoring are dissolved oxygen, pH, ammonia and nitrate. Various methods for measurements are presented in Table 4. Temperature and turbidity can be measured with an inexpensive thermometer and a secchi disc, respectively. 8.3.2 Sampling of stocks Regular sampling of shrimp stocks in pond is highly necessary to monitor, their growth performance. This is especially important for adjust the amount of feed used according to shrimp size and standing crop. This is done through periodic sampling of the shrimp to determine their body weight. In the case of Penaeid shrimps, seining is not possible since these species are usually burrowing or

wandering types. It is therefore difficult to obtain a representative sample. However, since these are hardy species, a cast net has proven to be an excellent sampling gear. Usually ten casts is sufficient to get a representative sample of one hectare pond. The dimension of a cast net should be measured to determine the area covered in order to calculate the total stock in the pond. The following formula is used to determine the pond stock:

where X = stock in pond Sampling in early hours of the morning or at night is preferable as the shrimps are more active during these periods and are more evenly distributed that during hot sunny day. For large pond, 15–20 casts may be necessary to obtain a more accurate average.



9 . Wa t e r Q u a li t y M a n a g e m e n t In any shrimp farming, management of water quality is of primary consideration particularly in ponds with higher stocking rates. Degradation of water quality is detrimental to shrimp growth and survival. Good quality water is usually defined as the fitness or suitability of the water for survival and growth of shrimp.

9 .1 Sa l i n i t y Younger shrimps appear to tolerate a wider fluctuation of salinity than the adults. The post -larvae of many Penaeid species can tolerate wide salinity fluctuation which has little effect on their survival or growth. In pond condition, P. monodon can tolerate wide range of salinity from as low as 5 ppt to a high of 40 ppt. Many Metapenaeus also tolerate high salinity. P. merguiensis and P. indicus prefer brackish water while P. semisulcatus and P. japonicus require more saline condition for growth (27–32 ppt). Due to high evaporation rate in some countries, salt concentration in ponds gradually increases during the summer months. Salinity may increase to beyond 40 ppt and thus retard growth. This should be taken into consideration when brackishwater species are used since salinity may increase above their limit of tolerance. In such cases, the species cultured should be changed during the summer months to conform with increasing salinity or the water should be changed frequently either by pumps or through tidal exchange. Table 4. Methods of Measuring the Physico-chemical Parameters of Ponds. Parameters

Method of Measurement

Remarks

Winkler titration method

A traditional procedure which is generally conducted in the laboratory.

Polarographic method

This involves the use of a portable DO meter for field use. It is reliable and accurate. It is important to calibrate using the data obtained form Winkler Method. from time to time.

Electrometric method

This uses portable pH meters which are standardized using standard buffer solutions. It is gives accurate results especially with glass electrodes.

Colorimetric method

This makes use of comparators such as Lovibond. The samples after addition of indicators are compared with colored solutions of known pH.

pH papers

It does not give accurate values but sufficient enough for fast baseline monitoring in the field.

Nesslerization methods

Widely used method for water sampels but tedious.

Phenate method

It is less cumbersome than nessler. Fast and accurate. It can be used using a specific-ion meter or a spectrophotometer.

Cadmium reduction method

Quite cumbersome but relable.

1. Dissolved oxygen

2. pH

3. Total Ammonia Nitrogen

4. Nitrate

9.2 pH The pH of the pond water is indicative of its fertility or potential productivity. Water with pH ranging from 7.5 to 9.0 are generally regarded as suitable for shrimp production. The growth of shrimps is retarded if pH falls below 5.0. Water with low pH can be corrected by adding lime to neutralize the acidity. Water of excessive alkalinity (pH values > 9.5) may also be harmful to shrimp growth and survival. In ponds which are excessively rich in phytoplankton, the pH of pond water usually exceeds 9.5 during late afternoon. However, at daybreak, the pH is usually lower. Excessive plankton growth can be corrected by water exchange.

9 . 3 Di s s o l v e d o x y g e n ( DO ) Maintenance of adequate level of dissolved oxygen in pond water is very important to shrimp growth and survival. Prolong exposure to the stress of low concentration of oxygen lowers their resistance to disease and inhibits their growth. In most cases, oxygen depletion often resulted in mass mortality (anoxia) of shrimp stock. This is particularly common in intensive culture operation. Dissolved oxygen in the pond water comes from two sources. Most of it comes as a by-product of photosynthesis. The other source is from the diffusion of atmospheric air. The amount of dissolved oxygen in the pond water is affected by many factors particularly water temperature, respiration and the level of organic matter. In tropical shrimp pond, the oxygen level in the pond water is normally low because of the higher temperature. However, tropical species are able to adopt to lower oxygen concentration than their temperature counterparts. During daytime, more oxygen is produced through photosynthesis than is removed from the water by the respiration of animals. At night, both plants and animals continue to respire while oxygen is being added to the water only from the atmosphere. In some instances, the respiratory demand under certain circumstances cause total depletion of oxygen especially at daybreak causing anoxia of the cultured animals. Depletion of DO in the pond can be controlled by the following measures: a. Water exchange throug renewal of pond water with fresh water either by tidal flow or pumping. b. Installation of aeration system. In the design of pond layout, it is essential to consider maximal utilization of the natural environment to maintain higher dissolved oxygen content in pond water such as: i. Orientation of the long axis of the pond with the prevailing wind. ii. Construction of larger pond to allow a greater contact of water surface with atmospheric air. iii. Promote wind action on the pond in facilitating water movement and oxygen diffusion. iv. Avoid planting of trees on dikes.

9 .4 N i t r o g e n c o m p o u n d Nitrogen in pond exists in different forms such as nitrate, nitrite, ammonia and various forms of organic nitrogen. Organic nitrogen ranges from relatively simple dissolved compounds such as amino acids to complex particulate organic matter. Nitrogen occurs in the mud in the same form that exist in water. In pond culture activities, ammonia nitrogen (in the form of un-ionized ammonia) is considered important since this compound is toxic to aquatic animals at certain concentrations. Ammonium ions which is another form of ammonia nitrogen is harmless except at extremely high concentrations. Ammonia nitrogen is a product of fish metabolism and decomposition of organic matter by bacteria. The pH and temperature of the water regulate the proportion of total ammonia which occurs in un-ionized form. The highest concentration of total ammonia nitrogen usually occur after the peak of phytoplankton

bloom when most of them died. The pH of the water is low because of high concentration of carbon dioxide. Studies have shown that exposure to ammonia concentration of 0.45 mg NH 3 -N/1liter would reduce shrimp growth by 50%.

9 .5 T e m p e r a t u r e Water temperature plays a very important role in regulating the activities of the cultured animal. The rate of chemical and biological reactions is said to double every 10°C increase in temperature. This means that aquatic organisms will use twice as much dissolved oxygen and chemical reactions will progress twice as fast at 30°C than 20°C. It follows therefore that dissolved oxygen requirement of aquatic species is higher in warmer than in cooler water. Many Penaeid species are tropical or subtropical species. The optimum temperature is about 25–30°C and hence many of the species such as P. indicus, P. monodon and P. merguiensis can be cultured throughout the year while P. japonicus and P. orientalis are limited to the summer growing seasons only.

9 .6 H y d r o g e n s u l f i d e , H 2 S Hydrogen sulfide can severely affect shrimp growth in pond. H 2S is produced by chemical reduction of organic matter that accumulates and forms a thick layer of organic deposits at the bottom. The bottom soil turns black and a rotten smell is discharged if disturbed. High levels of hydrogen sulfide would affect directly demersal or burrowing shrimps such as P. monodon. At levels of 0.1–0.2 ppm in the water, the shrimps appear to loss their equilibrium and die instantly at a concentration of 4 ppm. Using iron oxide (70% ferrous oxide) to treat the bottom soil containing high levels of H 2S would not be economical. The cheaper means is by frequent exchange of water to prevent building up of H 2S in the pond.



10. Feeds and Feeding One of the most important operational functions in shrimp culture is the provision of adequate food supply to ensure that the cultured animals attained the desired harvesting size within the targetted time frame. Feeds is among the largest operational cost of shrimp farming and every efforts should be made to ensure efficient utilization of feeds for growth. It is therefore necessary to have adequate knowledge on the feeding habits and behavior of the cultured organisms, their nutritional requirements and efficiency in dietary protein conversion for growth. Traditional shrimp farms in most Asian countries employ extensive culture operation in which the growth of shrimps fully depends on natural food organisms. In semiintensive culture operation, supplementary feeds are given while natural food organisms remain the major food source. In intensive culture operation, shrimp growth is completely dependent on artificial diets.

1 0 .1 Fe e d i n g b e h a v i o u r In the natural habitat, shrimps feed on other small crustaceans, finfish, molluscs, polychaetes, ophiuroids and other slow-moving benthic organisms. They catch food with their pereiopods, take to their bucal cavity and nibble slowly. They are omnivorous but cannibalize if food is insufficient or of poor quality. They are also scavengers, feeding on any kind of decaying matter available in the habitat.

1 0 .2 N a t u r a l f o o d i n p o n d Natural food organisms are allowed to grow in well prepared pond fertilized with organic or inorganic fertilizers. These food organisms in the form of benthic blue-green algae, diatoms, green algae and various species of microscopic zooplankton and microbenthos serve as the natural food of the cultured shrimp. The nutrient composition of the major natural food organisms growing within ponds is shown in Table 5. The main types of natural food predominate in shrimp ponds are: a. Lablab * - This is a kind of microbenthos composed of blue-green algae, diatoms and other microscopic plants and animals. In the Philippines, shallow brackishwater ponds below 40 cm are heavily fertilized to grow lablab for the culture of milkfish. However, lablab is also providing natural food for shrimps. Growth of lablab requires higher salinity which is not conducive for growth of the tiger shrimp. However, lablab is used as natural food for the post-larvae and juveniles in the first two months after stocking. b. Lumut* - This is composed mostly of filamentous algae such as Chaetomorpha which are also growing in milkfish ponds. The lumut can be grown in low salinity compatible with the growing conditions for shrimps. Other living organisms attached to the lumut are also eaten by the shrimps. Herbivorous fish are often stocked to control the density of lumut in the pond. c. Phytoplankton - Fertilization in pond promotes growth of microscopic plants known as phytoplankton, These primary producers serve as the main food of zooplankton and benthic organisms which in turn become the food of shrimps. The presence of yellowish-green color in pond water signifies good growth of desirable planktonic organisms organisms conducive for shrimp growth. Other sources of food for the shrimps include macrophytes such as Najas graminen and Ruppia maritima which thrive at low salinities. These grow in abundance promoting also the growth of numerous benthic organisms attached to the plants. The shrimps grow well in pond with prolific

growth of these plants since the shrimps feed on the benthic organisms as well as the decaying parts of the plants. * in Filipino

Table 5. Nutrient composition of natural food commonly found with ponds. % Dry Matter Crude protein Crude fte Crude fiber ash

Nitrogen-free extract

Lablab

6.73

0.86

5.27

74.38 12.77

Lumot

15.26

2.17

15.07

31.39 36.09

Najas graminen 18.38

2.43

18.73

23.88 36.58

Ruppia maritima 15.38

3.70

17.26

14.24 49.49

1 0 .3 Su p p l e m e n t a l f e e d i ng As the shrimp grow, consumption increase and the natural food in the pond becomes insufficient. Thus, many shrimp farmers provide supplemental feeds. The types of feed used are: a. Moist/wet feeds - These are freshly prepared feeds using locally available ingredients. The feeds should be given fresh immediately after preparation. However, these could also be frozen and thawed when needed. The commonly used feeds include the following: rice bran with trash fish carabao and cattle hides, house discards/ leftovers (hides are cut into lft 2 pieces, attached to sticks and distributed in the pond) chopped toads and frogs African snails with shells crushed mussel and clam meat snails from the ponds with shells crushed b. Dry pelleted feeds - Pelleted feeds are available commercially to be used as supplementary or full feeds of shrimps. These are also prepared using locally available ingredients. A good pellet feeds not only should meet all the nutritional requirements of shrimp but also stable in water for a certain period of time. The feeds should have also a longer shelf - life. Usually, commercial pellets are brought in bulk and should be properly stored in storage room with low humidity to minimize fungi occurence and insect infestation. It is advisable to ensure rapid turn over of feed supply.

1 0 .4 Fe e d i n g m e t h o d Supplemental feeds may be given by broadcasting, through feeding tray or automatic machine feeder. Broadcasting method is carried out by spreading the feeds evenly into the pond surface. For bigger ponds, the use of flat-bottom boat is needed so that the mid-portion of the pond can be reached. Feeding trays containing the apportioned feeds are placed strategically at different parts of the pond. The trays vary in size from 1–10 m 2 . The common materials used are woven bamboo strips or polyethelene screen (Fig. 22). The trays are usually tied at four corners and suspended into the water column. Normally, one tray per 10 to 100 m 2 pond area is being practiced. The use of feeding tray prevents feed wastage. At the same time, the size and condition of shrimp can be checked and their consumption rate estimated based on the left-over feed in the tray. The disadvantages however, are that when insufficient feeds are given or insufficient trays are used, the bigger and stronger shrimps might prevent the weaker and smaller ones from feeding. If there are many competitors (eg. tilapia) in the pond, they might consume the feeds before the shrimps can get hold of them. Hence, in order to minimize the above mentioned situation, a combination of broadcasting and feeding tray methods are usually employed.

Various automatic feeders designed primarily for fish were tried in shrimp ponds adopting intensive farming operation. Automatic feeders dispense a given amount of feed at certain interval during a 24hour period. A timing device, usually electrically activated, is an essential component of such feeders. These can be set to deliver feed in small quantities several times daily allowing the culturists to feed without being physically present. Extensive comparisons between the efficiency of hand feeding in contrast to automatic feeder have not been made in developing countries. Although it cannot be stated with certainly that one method is more feed-efficient than the other, the savings in labor realized by utilizing automatic feeders is significant, assuming that each feeder does not have to be filled daily. Offsetting this advantage is the high cost of the feeding devices, a number of which may be needed in large ponds.

Fig. 2 2 . A feeding tray

1 0 .5 F e e d in g r a t e a n d f r e q u en c y Optimal feeding rate and frequency are essential in maximizing conversion rate of feed to shrimp. The accuracy of determine the feeding rate is based mainly on the estimate of the density and size of the stock. The more common methods used to determine the feeding rate are: a. Adjustment of feeding rate through visual observation of left-over feed - This is employed by the use of feeding tray. Five to ten percent of the feeding ration are placed at the feeding tray while the rest are broadcasted into the pond surface. Prior to feeding, the tray is lifted to observe whether the previously given feed is totally consumed. If so, the previously given amount of feed is considered insufficient. Hence, an additional 2–5% of the feeding ration is added. However, if the feed is not totally consumed, the previous feeding rate is reduced depending on the left-over feed. This method is very subjective depending on the experience and skill of the operator. b. Periodic determination of the stock density for appropriate feed ration - This is done by the use of cast net. The stock density estimation is described in earlier section. The stocks are sampled at 15–30 days interval. The feed is given at 5–10% of the estimated shrimp biomass per day. c. Feed ration based on assumed density - This method of computing feed ration is based on the estimated survival rate. Most culturists assume 100% survival for the first month of stocking, 90% for the second month and 80% for the third month. Feeds are given at fixed rate of 5–10% of the estimated shrimp biomass per day. Although the food requirement for maintenance and growth

increases with increasing biomass, the relative food requirements per unit weight of animal decreases with increasing shrimp size. Hence, a sliding feed ration of 10% of the estimated shrimp biomass and 4% for the fourth month has been adopted. The common feeding frequency adopted is 2–5 times a day. Most culturists feed their stock every morning and afternoon only. However, experiments have shown that apportioning daily feed ration several times a day improve feed conversion efficiency as it reduces feed wastage, ensures feed quality and more even distribution to the stock. If the stocks are to be fed 5 times a day, two should be given in daytime and 3 at night as the shrimps are more active when dark.



1 1 . M an i p u la t i o n o f St o c k i n g i n Ex t e n s i ve a n d S e m i i n t e n s i v e Fa r m i n g Op e r a t i o n s In extensive culture operation, the shrimps are fully dependent on the availability of natural food in the pond. As the shrimps grow, the amount of natural food organisms become insufficient to meet the growing demand. The growth of shrimps slow down when natural food diminishes. This usually takes place towards the second month of the culture period depending on the stocking density and fertility of the pond. In order to maintain optimum growth rate throughout the culture period, additional feeds should be given in the form of supplemental feeds, fertilization of pond water or transfer of stock to new ponds with natural food. Supplemental feeding is recommended when cheaper feeds (eg., trash fish) are available easily. Pond fertilization on the other hand, is commonly employed when the natural food in the pond is diminishing. However, the latter practice sometimes cannot supply sufficient quantity of natural food in the pond is almost completely consumed prior to fertilization. Transferring of stock to a new pond with luxuriant growth of natural food has been found to be conducive to shrimp growth. Pond production of shrimp is comparable or sometimes even better than those fed with supplementary feeds. Other advantages are: (i) survival rate is significantly improved due to effective eradication of predators and competitors, (ii) maximum growth rate is usually attained because the shrimps are transferred to a more growth promoting habitat free from pollution stress, (iii) reduce the frequency of soft-shelling condition. The disadvantage, however, is that mortality during transfer is unavoidable especially when the shrimp have newly molted. In semi-intensive culture operation (2–4 shrimps/m 2 ), there are no significant difference between feeding the stocks after 2 months of culture and transferring them to another pond using the modular system described above. Due to high cost of supplementary (formulated) feeds, it appears that the modular system is economically more viable than using supplemental feeds.



1 2 . H a r v e s t i n g a n d P r e s e r v at i o n The stocks are usually harvested upon reaching the marketable size (about 30 pcs/kg). Harvesting may be done completely at one time or partially depending on demand. Complete harvesting is usually undertaken by the use of a bag net installed at the drainage gate of the pond. The shrimps that go with the drained water are collected at the bag net and the remaining ones are hand picked when the pond is completely drained. The shrimps should be harvested only when they are not molting because newly molted shrimp have soft shell and fetch lower price. Partial harvesting is normally practiced in culture operation with higher stocking density (i.e. in semiintensive or intensive culture). The stock, upon reaching the marketable size (30 g and above) can be harvested by the use of selective harvesting net (Fig. 23). The selective harvesting net is a modified shrimp trap net installed in the pond with mesh size big enough to retain the bigger shrimps. Several harvesting nets may be installed at various pond locations. This harvesting device is more efficient at night. Selective harvesting improves pond yields because it reduces intra-specific competition thus giving chance to the smaller ones to grow better. The shrimps can be partially harvested after 2–1/2 months of culture or when a lot of stocks reach the marketable size. This operation is usually carried out at bi-monthly interval until most of the stocks are harvested or the remaining ones reached the marketable size. Upon harvesting, the shrimps should be washed and placed immediately in chilled water (10–15°C) for about 15 minutes. They are then packed in styrofoam box with alternate layers of crushed ice at a ratio of 1:1. Smaller styrofoam boxes are preferred to facilitate transportation. If bigger styrofoam boxes are used, it is better to fill up the box with chilled water, shrimps and ice to avoid physical damage on the shrimps at the bottom.

Fig. 2 3 . Selective harvesting net



13 . REFERENCES Boyd, C.E. 1976. Lime requirement and application in fishponds. FAO aquaculture conference. FIR:AO/Conf 176. E13. 3 p. Cook, M.L. 1976. Problems of shrimp culture in the South China Sea region. South China Sea Fishery Development Programme. De la Cruz, C.R. 1983. Fishpond engineering: a technical manual for small and medium scale coastal fish farms in Southeast Asia. SCC Manual No. 5. 180 p. FAO/UNDP SCSP. 1978. Manual on pond culture of penaeid shrimp. Asian National Coordinating Agency of the Philippines. Ministry of Foreign Affairs. Manila, Philippines. Foster, J.R.M. and T.W. Beard. 1974. Experiment to assess the suitability of nine species of prawn to intensive culture. Aquaculture 3:355–368. Hanson, J.A. and H.L. Goodwin. 1977. Shrimp and prawn farming in the Western Hemisphere. Dowdey Hutchingson and Ross, Inc. Hepher, B. and Y. Pruginin. 1981. Commercial fish farming with special reference to fish culture in Israel. Wiley International Publ. N.Y. 261 pp. Kato, J. 1980. Guide to design and construction of coastal aquaculture pond. Japan International Cooperation Agency, Tokyo. 180 pp. Kubo, I. 1949. Studies on the penaeids of Japan and its adjacent waters. J. Tokyo University Fish., 20(10). 870–872. Kungvankij, P. 1973. A survey of the distribution and abundance of economically important shrimp along the Indian Ocean coast of Thailand. Phuket Marine Fisheries Station, Fisheries Cont. No. 3. 1–9. Kungvankij, P. 1976. On the monoculture of jumbo tiger shrimp Penaeus monodon Fabricius. Phuket Marine Fisheries Station Contribution No. 7. 14 pp. Kungvankij, P. 1984. Overview of penaeid shrimp culture in Asia. Paper presented at the 1st International Conference on shrimp/prawn culture. Dec. 1984. Iloilo, Philippines. Kurata, H. 1975. Culture of the Kuruma shrimp. JICA Culture of Marine Organisms. 15–50. Liao, I-/Chiu. 1977. A culture study of grass prawn, Penaeus monodon , in Taiwan - the patterns, problems and prospects. Journal of the Fisheries Society of Taiwan, Vol. 5, No.2. p. 29. Mao, S.L. and V.J. Mancebo. 1982. Pond culture of P. monodon in the Philippines: survival, growth and yield using commercial formulated feeds. Journal of World Mariculture Society Vol. 14. p. 75–85. Motoh, H. 1981. Studies on the fisheries biology of the giant tiger prawn, P. monodon, in the Philippines. SEAFDEC Technical Report No. 7. 127 p. Shigueno, K. 1970. Problems of prawn culture in Japan. OCTA. 33 pp.

FAO Shrimp Culture_ Pond Design, Operation and Management

Recommend Documents