Effect of stocking density on survival and growth of endangered bata, Labeo bata (Hamilton–Buchanan) in nursery ponds

Abstract

Effect of stocking densities on the growth, survival and production of bata, Labeo bata fry and fingerlings were tested in a single-stage nursery rearing system. The experiment was conducted over a 7 weeks period in nine 0.028 ha earthen nursery ponds. Four-day-old hatchlings stocked at 0.60 million ha − 1 was designated as treatment T 1, 0.80 million ha − 1 as treatment T 2 and 1.0 million ha − 1 as treatment T 3. At stocking, all hatchlings were of same age with a mean length and weight of 1.01 ± 0.04 cm and 0.011 ± 0.002 g, respectively. Hatchlings in all the treatments were fed with a mixture of mustard oil cake, rice bran, wheat bran, and fish meal in 40:25:25:10 proportions (32.80% crude protein) from days 1 to 49 days. The water transparency, pH, dissolve oxygen and total alkalinity were found to be in the range of 24.33–47.48 cm, 7.3–8.8, 3.10–5.62 mg L − 1 and 104.13–140.58 mg L − 1 , respectively. The plankton level in all treatments was found to be at optimum level. Highest weight gain (6.76 ± 0.69 g) was observed in treatment T 1 and lowest (3.13 ± 0.34 g) in treatment T 3. Final length, final weight and survival of fingerlings also followed the same trends as weight gain. Fingerlings in treatment T 1 produced significantly higher specific growth rate (3.53 ± 0.23) than treatment T 2 and T 3. Feed conversion ratio was significantly lower in T 1 (0.32 ± 0.01) than T 2 and T 3. Significantly higher number of fingerlings was produced in treatment T 3 than in treatment T 2 and T 1, respectively. Despite of this, consistently higher net benefits were found from treatment T 1 than from treatment T 2 and T 3. Overall, highest growth (6.77 ± 0.66 g), survival (80.15 ± 0.85%) and net benefits of fingerlings were obtained at a density of 0.60 million hatchlings ha − 1 . Therefore, of the three stocking densities, 0.60 million hatchlings ha − 1 appear to be most suitable stocking density for nursing and rearing of bata fry and fingerlings in single-stage nursery system.