Acute toxicity of copper sulphate to African catfish, (Clarias gariepinus)

In this study, 96 hrs LC 50 values of copper sulphate (CuSO 4 .5H 2 O), a highly toxicant heavy metal, on African catfish, Clarias gariepinus of average weight 98.43 ± 24.09 g and length 20.5 ± 2.5 cm was determined. The acute toxicity tests were performed according to the static non-renewable bioassay procedure. The experimental design consisted of a control and six concentrations (24, 31, 38, 44, 50 and 55 ppm) of copper sulphate, with two replicates per group and twenty fishes in each replicate. The 96 hour LC 50 value based on probit analysis was found to be 40.86 ppm; the lower and upper lethal confidence limit for copper sulphate indicated a wide range between 37.47 to 44.58 ppm. Susceptibility of catfish, Clarias gariepinus to lethal effect of copper sulphate was found to be duration and concentration dependent as mortality was increased with an increase in its concentration. Results indicated that copper sulphate is toxic to fish, to moderate extent even at lower concentrations. Therefore, the present investigation may provide useful guidance that can be exploited by the aquaculturists to formulate the safety levels of copper sulphate in water bodies. Metal concentrations in aquatic organisms appear to be of several magnitudes higher than concentrations present in the ecosystem (1). This is attributed to bioaccumulation, whereby metal ions are taken up from the environment by the organism and accumulated in various organs and tissues. Metals also become increasingly concentrated at higher trophic levels, possibly due to food-chain magnification. Aquatic toxicity tests are used to detect and evaluate the potential toxicological effects of chemicals on aquatic organisms. Since these effects are not necessarily harmful,