Growth responses of carnivorous fish species under the chronic stress of water-borne copper

This study aimed to investigate the growth performance of three length groups (50, 100 and 150mm) of carnivorous fish species, Channa marulius and Mystus seenghala, under sub-lethal (1/3rd of LC50) exposure of water-borne copper, in terms of increase/decrease in average wet weights (g) and total lengths (mm), condition factor, feed intake (g) and feed conversion efficiency (%). A group of 10 fish of each species and length group, with three replications, was separately exposed to water-borne copper, for 120 days, at constant conditions of water temperature (28°C), pH (8) and total hardness (250 mg L-1). Weekly data on all growth parameters of fish were collected and analyzed statistically. Results showed that treated fish species exhibited significantly lower average wet weight and total length increments than control fish that followed the order: C. marulius>M. seenghala. Among three length groups of both fish species, 150 mm length group exhibited significantly higher growth in terms of average wet weight and total length increments than 100 mm and 50 mm length groups suggesting that younger fish became more susceptible to copper stress hence showed lesser growth than older fish. The “K” values computed were significantly higher for treated than the control fish. Copper treated fish exhibited significantly lower feed intake than control fish. However, among three length groups of fish, order of feed intake was 150 mm>100 mm>50 mm. C. marulius exhibited significantly higher FCE as compared to M. seenghala. Overall, it was concluded that sub-lethal copper exposure caused significant reduction in growth of carnivorous fish.