Heavy metal copper is common pollutants of freshwater ecosystems where they induce adverse effects on the aquatic biota. Fish, Catla catla is an important carp species in Tamil Nadu region having good nutritional values. Fishes living in close association with may accumulate heavy metals. In the present observation, the toxic effects of the heavy metal copper LC50 1.8 mg/L on the total RBC, WBC and Hb in the fish, Catla catla were estimated. The rate of oxygen consumption were observed decrease in fish Catla catla exposed to low 10% and high 30% sub lethal concentrations of copper sulphate for a period of 24, 48, 72 and 96 hrs. The sublethal concentrations of copper culphate on (Low 10% and high 30% sublethal concentrations) showed a decreasing trend in the RBC and Hb compared to controls and the WBC analysis revealed a significant increased compared to control for a period of 7, 14 and 21 days exposures. The results indicated the toxic nature of the heavy metal copper.
