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Best Aquaculture Practices (BAP) for Shrimp Framing Industry in Sri Lanka |
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NAQDA has taken steps to reformulate the Best Aquaculture Practices (BAP) documented for shrimp aquaculture. Stakeholders of the shrimp aquaculture industry emphasized the need for this task in several meetings to government officials. As a result, previous BAPs were reviewed and new documentation was made available with the collaboration of stakeholders of the shrimp aquaculture industry. Some highlights of BAP are presented below. |
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In Sri Lanka , shrimp aquaculture comprises of three culture systems. They are: open system, semi-closed system and closed system. Majority of the shrimp farms have adopted an open system, which implies obtaining water from a common water source (‘Dutch canal' mainly) and releasing effluent water back to it. About 1000 has of farm area are being planned to be brought under the semi-closed system this year. In the semi-closed system, farmers maintain a reservoir tank for water storage. Water is obtained from the treatment tank after treatment with chlorine and e ffluent water is discharged only after disinfections have been effected. In the closed system, farmers obtain water from a common water body to replace evaporation and seepage losses. Farming may be carried out only upon re-circulation of water. There is no water discharge to the lagoon. Open system does not require water storage tanks. Semi-closed/closed systems need water storage tanks. Capacity of water storage tanks of a semi-closed system may be confined to 25% of the total volume of the pond area, where farming is carried out. Depth of the tank is a maximum of 2 meters. Closed system may consist of water storage tanks, which has capacity to store 40-50% of the total water volume of the pond area. Depth of the tanks is the same as in semi-closed system. But storage tank area could be reduced up to 25% with special treatment to the intake water. Sedimentation area is required in any type of culture system. Farmers can use either a common sedimentation area or their own sedimentation area to sediment effluent water. Depth of the sedimentation area should be one meter. Designing of the pond/canal should be made to enhance the free flow of water. For reducing organic load of water, it is recommended to culture bivalves and seaweed in the sedimentation area. Effluent water may be discharged to the environment under gravity. Minimum sedimentation area is 10% of farm operating area. Water should be obtained through 576sq.mesh screen to filter crustacean, fish eggs and wild fish etc. Suitable chemical methods as well as biological methods such as favorable bacteria, bivalve and sea weed cultures are recommended for the area of sedimentation. Selecting post larvae: It is recommended to stock 15-20 days old post larvae. It is essential to test post larvae quality before stocking. If the quality of post larvae is right, post Larvae should be tested for WSD by PCR screening. If the WSD disease is not found, stocking of post Larvae could be carried out. Stocking Density: Recommended stocking density is 4-6 PLs per Sq meter for open system. With aeration, it can increase up to 15 per sq. meter. Special approval has to be taken from NAQDA in order to increase stocking density up to 25 post larvae per sq. meter in the semi-closed/closed system. If required, either pre growing ponds or Hapas could be used as nursery grows out tanks. Post larvae could be grown 11/2 months in these nursery ponds before releasing to the grow-out pond. Pond preparation: Organic matter in the pond bottom should be removed even if they are in dry or wet form. Lime is recommended to be used according to pH of the soil. Fertilizing of the pond is recommended to be done considering fertility of soil of the pond. Feed and Feed management: Farmer should carry out feeding shrimp with good quality feed and monitoring of feeding is to be carried out daily in order to prevent excess feeding. A feeding record should be maintained at the farm to be used for monitoring purposes. Harvesting: When harvesting is carried out, effluent water should be discharged to the sedimentation area to settle organic load. Collecting prawns and transportation should be done hygienically in the best possible way. Resting period: There should be at least 60 days rest period in between two culture cycles. Pond drying, removing organic load in the pond bottom, repairing dikes and canals, liming (if required) and fertilization (if required) etc could be carried out during this period. Culture Period: A Single crop could be obtained per year according to the crop calendar for open and semi-closed systems. It is recommended to culture fish in the next season. Two crops could be carried out per year for closed system according to the crop calendar. Bio Security: Precautions should be taken to prevent the entry of predator birds, dogs, crows, and crabs reptiles to the farm. If a farm is observed to be infected with a disease, Shrimp Farm Extension and Monitoring Unit of NAQDA, NARA , and respective Farmers' Organizations should be informed, as soon as possible. In order to inform nearby farms, a red flag should be erected at the disease-infected farm. Water from infected ponds should not be released to the environment. Farmers should strictly adhere to this. In a disease situation, water should not be obtained from a common water body to culture ponds If the size of shrimps in the infected pond is above 5 gms, a drag net could be used for harvesting. The remaining stock should be destroyed by using appropriate concentrations of suitable chemicals. Dead prawns, shells, parts of the bodies should be buried. Treated water should be discharged to the lagoon after seven days. Hatcheries should consist of tanks for water storage and water disinfections. There should be a retaining tank for hatchery effluent water to be sterilized. Water should be obtained using a recommended filtration system (UV/Ozone). Otherwise sand filters can be used and thereafter water should be treated with chlorine at a concentration of 30ppm. Before receiving brooders to the hatchery, a PCR test has to be done for WSD and MBV to ensure that brooders are free from WSD. Brooders should be kept in the quarantine tank until testing is carried out. If the brooders are infected with WSD, they have to be destroyed and should chlorinate the quarantine tank should be chlorinated. Only after three days, could shrimp brooders be brought back. Live feeds belonging to family Crustaceae should not be used in the hatchery. Records of water quality parameters and Bacterial counts in the hatchery should be maintained in order to manage the water quality. Post larvae are subjected to screening by PCR for every cycle so that a whole batch produced by the hatchery is represented to ensure whether a particular batch is free from WSD and MBV (level of 5 %). If any disease is found, the hatchery should be chlorinated and kept closed for a minimum of at least two weeks After every two or three operational cycles, hatchery should be kept closed at least for two weeks. Washing tanks, repairing of buildings, water supply and the drainage system followed by drying should be carried out during his period. In addition, hatcheries should comply with a common shut down period according to the crop calendar, which is declared by NAQDA All prawn farmers and hatchery owners should follow aquaculture management measures and a plan for disease control in the area, which are recommended /declared by the Director General of NAQDA. All prawn farmers and hatchery owners should maintain a reporting book with regard to activities of farming/breeding in their farms/hatcheries. The said book should be submitted to officers from Shrimp Farm Extension and Monitoring Unit and, Extension Officers at any time if it is required for examination. All prawn farmers and hatchery owners should maintain a log book to be signed by SFEMU Officers who visit the farm /hatchery. All prawn farmers and hatchery owners should obtain instructions regarding usage of chemicals from the Shrimp Farm Extension and Monitoring Unit of NAQDA, NARA and Provincial Fisheries Ministry. The right to change these guidelines to meet the requirements of the national shrimp industry is mandated to Department of Fisheries and Aquatic Resources. |
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