WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2025 77 At 28°C, fertilized eggs hatch approximately 20 days of fertilization. The larvae require brackish water of 12-14 ppt. Over 20 to 35 days, the larvae go through 11 larval stages before becoming post-larvae. Food availability, dissolved oxygen, water temperature, and other environmental factors affect survival. Post-larvae are then suitable for freshwater culture. Prawn farming systems Bihar has a plenty of water resources, including 0.5 million hectares of flood plains, 0.1 million hectares of ponds and tanks, and 0.3 million hectares of reservoirs. Furthermore, the state manages sizable areas under its canal authority, where water is held for nearly six months annually but isn’t yet utilized for aquaculture. Despite having a wealth of water resources, total fish production of Bihar is lower than many other Indian states. Carps and giant freshwater prawns interplanted in a polyculture farming system may result in higher production and greater profitability to the fish farmers. Despite availability of water resources, farmers in Bihar have not yet commercially adopted freshwater prawn culture, due primarily to lack of knowledge about prawn farming and lack of quality seeds. Fish farmers of Bihar can opt for polyculture of Indian major carps with giant freshwater prawns instead of prawn monoculture. Prawn monoculture systems generally lead to differential prawn growth, high maintenance costs, and low survival rates. Fish in polyculture systems, apart from efficient utilization of all strata of fish ponds, also act as a biological control on the growth of filamentous algae, zooplankton, and phytoplankton, which may otherwise lead to instability in the pond ecosystem. Low fish stocking densities in a polyculture system enhance pond water’s ecological integrity without affecting prawn’s growth. Prawns in a polyculture system may survive on consumption of leftover fish feed and faecal matter of fish. The waste utilization by prawns in polyculture minimizes input costs through deduction of costly prawn feed. Based on the management strategies, grow-out cultures can be divided into three categories: extensive, semi-intensive, and intensive. In India, the semi-intensive farming strategy is mostly used, with 7.5 post-larvae/m2 density to achieve 3.0-3.5 tonnes/ ha annually with a 6 month culture period. Optimum fertilization, balanced feeding, and the ideal stocking density in intensive farming are essential to increase productivity. Additionally, regular checks should be made on the water quality parameters, the health of the prawns, and their growth rate. Proper pond preparation technique must be followed for prawn farming in order to increase productivity and improve survival. Liming must be done after the pond is prepared. The amount of lime that should be applied depends on the soil’s pH, but typically 200-1000 kg of lime is applied. Before farming begins, approximately 1000 kilograms of cow dung, 500 kg of poultry manure, and 100 kg of super phosphate can be added for increase the primary productivity of the pond. Enough hiding spots should be available to avoid cannibalism, especially during moulting periods. The giant freshwater prawn eats aquatic insects, worms, algae, tiny mollusc crustaceans, and debris in the wild condition. They take artificial feed as well in culture systems. In semi-intensive farming, prawns are often fed high-quality pelleted feed that contains roughly 25-30% protein and 5-10% fat in the evenings. Over the growing period, the feeding rate should initially be 20% of body weight, decreasing to 5% with increasing body weight. FIGURE 2. Life cycle of freshwater prawn. FIGURE 3. Harvested prawns from a polyculture system. (CONTINUED ON PAGE 78) TABLE 1. Optimum Water Quality Parameters for Prawn Polyculture Systems. Parameter Optimum range Temperature 250 to 320C pH 7-8.5 Dissolved oxygen 5-7 ppm Visibility 40 to 50 cm Water colour Brown to light green Alkalinity 50-100 ppm Ammonia < 0.1 ppm Nitrite <1 ppm Nitrate 20 ppm Hydrogen sulphide 0.0 ppm
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