Effect of stocking density on growth and yield of Labeo bata fingerlings reared in cages

An experiment was carried out to evaluate the growth performance and yield of Labeo bata reared in cages at different stocking densities in a floodplain wetland of Assam, India. Fifteen cages (effective water volume 40 m3 each) installed in the wetland were stocked with fingerlings of L. bata (mean length 8.20 ± 0.08 cm; mean weight 4.82 ± 0.13 g) at five different stocking densities, i.e., 25 (D25), 50 (D50), 75 (D75), 100 (D100) and 150 fingerlings m−3 (D150) in triplicates. Fish were fed with pelleted feed containing 30 % CP at 3–5 % body weight twice-a-day for six months. Specific growth rate of the reared fish recorded at different stocking densities were 1.08 ± 0.03, 0.89 ± 0.01, 0.90 ± 0.05, 0.77 ± 0.02 and 0.57 ± 0.02 % day-1, respectively, in D25, D50, D75, D100 and D150. The corresponding weight gain percent were 604.77 ± 35.63, 395.37 ± 11.32, 407.88 ± 44.91, 296.61 ± 13.07 and 180.70 ± 11.02. In general, growth performance of the reared fish was inversely proportional to stocking density. However, yield (biomass) increased with increase in stocking density of up to 75 fingerlings m-3 after which no significant increase was observed. Economics of the cage aquaculture system also showed highest net revenue and benefit-cost ratio at 75 fingerlings m-3. Rearing of fish at this stocking density yielded 50 % higher fish production and generated 92.5 % higher net revenue than rearing at the lowest stocking density. The results suggest 75 fingerlings m-3 as the optimum stocking density for rearing L. bata in net cages.