Two hundreds and thirty catfish (Clarias lazera) weighing 200-250 gm each were obtained from abbasa fish farm were used in this investigation. LC₅₀ of Copper Sulphate, lead acetate and Zinc sulphate was determined by exposure of the fish to different concentrations of the tested metals for 96 hours. It was 0.2, 0.1 and 0.1 ppm respectively. Determination of the residues of these heavy metals in the fish muscles and organs was studied after exposure of the fish to 0.02, 0.01 and 0.01 ppm (1/10 LC₅₀) of the tested metals respectively. Blood picture, liver and kidney functions and some biochemical parameters were also studied after exposure of the fish to the tested salts of heavy metals. It was found that liver contains the highest amount of copper (Cu) and lead (Pb) 20.1 & 12.7 ppm respectively while zinc (Zn) was concentrated in the kidney (7.1 ppm). The muscles contained Cu, Pb & Zn (3.6, 0.3 and 0.4 ppm) respectively lower amounts than the permissible limits.
RBCS count decreased by exposure of the fish to Cu, Pb and Zn (1.9, 1.95 and 1.5 million/ µl versus 2.4 for the control) respectively, Hemoglobin concentration and Packed Cell Volume (PCV) were also decreased. On the other hand total leucocytic count increased by the exposure of the fish to Cu and Pb (32.77 and 39.7 versus 27.3 10³/µl), for the control. Exposure to Cu increased serum AST activity from 150 to 170 L whereas serum ALT, AP, total proteins, albumin, total bilirubin, cholesterol did not significantly altered by exposure to tested metals. Exposure to Cu and Pb increased serum glucose level from 90 to 115 and 100 mg/dI respectively, Cu decreased the sodium, chloride, potassium and calcium (123, 112, 2.4 m.mol /L and 6.9 mg/dl versus 140, 123,2.7 m.mol/L and 9.6 mg/dL versus 140, 123, 2.7 m.mol/L and 9.6 mg /dL) of the control respectively. On the contrary it increased blood urea nitrogen from 2.5 to 3.5 mg/dL. Exposure to lead and zinc did not significantly alter these parameters.