Effect of Stocking Density on Survival and Growth of Endangered Elong, Bengala Elonga (Hamilton) in Nursery Ponds

Effect of stocking densities on the growth, survival and production of elong, Bengala elonga fry and finger lings were tested in a single-stage nursery rearing system. Physico-chemical parameters and plankton populations were at the optimum level for culture period. The experiment was conducted for a rearing period of 42 days in nine earthen nursery ponds having an area of 0.081 ha each. Four-day-old hatchlings stocked at 0.8, 1.0 and 1.20 millionha-1 were designated as treatment T1, T2 and T3. At stocking, all hatchlings were of same age with a mean length and weight of 0.90±0.02 cm and 0.001±0.00 g respectively. Highest weight gain was observed in treatment T1 and lowest in treatment T3. Final length, final weight and survival of fingerlings also followed the same trends as weight gain. Fingerlings in treatment T1 produced significantly higher specific growth rate than treatment T2 and T3. Feed conversion ratio was significantly higher in treatment T1 followed by treatment T2 and T3 in that order. Significantly higher number of fingerlings was produced in treatment T3 than in treatment T2 and T1, respectively. In despite of this, consistently higher net benefits were found from treatment T1 than from treatment T3 and T2 and also significant (P<0.05). Overall, highest growth, survival and net benefits of fingerlings were obtained at a density of 0.8 million hatchling.ha-1. Therefore, of the three stocking densities, 0.8million hatchling.ha-1 appears to be most suitable stocking density for nursing and rearing of B. elonga fry and fingerlings in single-stage nursery system.