Density-dependent growth performance of Indian major carps in rainwater reservoirs

Abstract

Summary The study was carried out to evaluate growth performance of Indian major carps at different stocking densities in rainwater reservoirs. In this experiment, the absolute growth performance of Catla catla, Labeo rohita and Cirrhinus mrigala at stocking densities of 5000, 8000 and 11 000 fingerlings per hectare was 377.7, 215.4 and 241.9; 370.2, 186.7 and 219.1; and 306.7, 163.4 and 180.6 g, respectively. The recorded biomass yield at 5000, 8000 and 11 000 fingerlings per hectare was 1035, 1572 and 1573 kg ha−1 per 180 days of culture. The effect of stocking density on production performance (performance index, PI) was highly significant (P < 0.05) at the higher stocking density of 11 000 ha−1, while there was no significant variation between PI at stocking densities of 5000 and 8000 ha−1. This indicates optimum production performance at 8000 ha−1, where yield is significantly higher (P < 0.05) than yield at 5000 ha−1 and almost equal to the yield at 11 000 ha−1. An increase in stocking density from 8000 to 11 000 ha−1, however, showed a sharp decline in average mean body weight of each species, even with supplemental feeding. With an increase in stocking density, the biomass yield increased to an optimum (1572 kg ha−1), with no substantial increase thereafter. Reductions in growth, which occurred at high density, did not appear to be due to poor water quality as the water quality did not differ significantly among various treatments. Thus, the reduced survival and growth at high density appears to be a behavioural interaction or physiological response to density itself.