WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2015 53 (CONTINUED ON PAGE 54) day, hatchlings measured 6.5-7.0 mm in length (Fig. 2) and were released into a nursery tank for further rearing. Nursery Phase Four-day-old hatchlings were reared to the fry stage (20-25 mm) in earthen nursery ponds of 200-1000 m2 (Fig. 3). Nursery pond preparation prior to stocking included the removal of aquatic weeds and predatory fish, followed by liming and fertilization with organic manure and inorganic fertilizer. Aquatic insects were eradicated by the application of a soap-oil emulsion or removed by repeated netting before stocking. The recommended stocking density is 3-10 million/ha, but higher levels of 10-20 million/ha can be also used in well-managed ponds with good water circulation. Hatchlings can be given a supplementary feed made of a 1:1 mixture of rice bran and groundnut or mustard seed press cake. Survival ranges from 30 to 50 percent. Although the beneficial effects of nursery pond preparation are well established, some of these activities are often ignored by farmers, resulting in poor fry survival. Fingerling Production Generally pengba fingerlings are reared along with Indian major carps in ponds. Survival in these fingerling rearing systems ranges from 70 to 80 percent. The production of table fish has not been adequate to meet the market demand. One of the serious problems is the poor availability of a suitable, well-balanced fish feed. High survival (94.5 percent) and growth (785 kg/ha) in three months rearing can be achieved with supplementary feeding. Azolla, an aquatic fern, can be incorporated into pengba feeds that result in good survival and growth rate (Basudha and Vishwanath 2002). Present Culture Trend in the Northeastern Region A few progressive fish farmers in northeastern states have tried to culture pengba. Grow-out of pengba has been confined mainly to earthen ponds. The culture practice is normally adopted in combination with other carps. Although annual production levels of 4-5 t/ha can be achieved with the adoption of scientific carp culture, such practices are limited to a few farms. A large share of the production still comes from extensive farming involving stocking and fertilization as the main inputs, resulting more modest annual production levels of 1-2 t/ha. The general practice of pengba culture includes control of predatory and weed fishes, stocking of fingerlings at a combined density of 7000-8000/ha, pond manuring and fertilization with organic manures like cattle dung or poultry droppings and inorganic fertilizers, the provision of a mixture of rice bran and mustard seed press cake as supplementary feed, fish health monitoring and water management. The grow-out period is normally one year, during which pengba grows to about 400-500 g. In some cases, farmers carry out partial harvests of market-size fish (>300 g) at intervals. Although fingerlings should be used to stock grow-out ponds, their inadequate availability compels some farmers to stock ponds with fry, leading to poor survival and production. Supplementary feed forms the major input, constituting over 50 percent of the recurring expenditure of grow-out. Because commercial feeds are expensive, farmers often use the conventional rice bran and oilseed cake mixture, usually supplied in dough form, which sometimes causes wastage and deterioration of water quality. Careful feed management and culture practices are required to enhance fish production and profit margin. A major problem with pengba is that it is more prone to ulcers and columnaris disease compared to other carp species at higher stocking densities. This often causes growth reduction and mass mortalities. Conservation Strategies The conservation of freshwater fishes has been recognized as an important required action around the world because a number of species are extinct or endangered and the threat is increasingly significant as a result of several anthropogenic perturbations. Major effort has been made to study the biology and ecology of pengba. A mass stocking program was made by various organizations to enhance pengba populations in Loktak Lake and its adjoining water areas. Before construction of the Ithai barrage in 1979 and its subsequent commissioning in 1983, pengba was found in the waters of the Imphal Valley. The fish is still found in Myanmar and Yunnan Province of China. The main threats to pengba in Manipur is from hydroelectric power development TABLE 1. Agents used for induced breeding of pengba Female Male Inducing agent (per kg body weight) (per kg body weight) Pituitary gland extract 10 mg 3 mg Ovaprim 0.5 mL 0.25 mL Ovatide 0.6 mL 0.3 mL Wova-FH 0.6 mL 0.3 mL FIGURE 3. Pengba fingerlings.
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