Zinc is a necessary trace element that contributes cumulative polluting effect to aquatic organism. The effect of sublethal concentration of zinc sulphate was investigated on the serum biochemical parameters of Clarias batrachus. This study was carried out to evaluate the sub chronic toxicity of zinc at three levels (10mg/L, 20mg/L and 30mg/L) for 15, 30 and 45 days. The biochemical changes in plasma showed significant increased in glucose, lipids (Triglycerides and cholesterol), serum phosphatases (acid and alkaline phosphatases) and serum transaminases (SGOT & SGPT) where as decreased in bilirubin and protein level. These results indicate that both concentration and period of exposure of zinc sulphate can alter the plasma’s biochemical contents of Clarias batrachus. Thus it can be concluded that fishes can effectively used as monitors of water quality with respect to heavy metal, zinc as well as toxicant. 

Keywords: Zinc; Chronic Toxicity; Biochemical Changes; Clarias Batrachus.