
Pesticides is a common pollutants of freshwater ecosystems where they induce adverse effects on the aquatic biota. Freshwater carp fish, Oreochromis mossambicus is an important carp species in Tamil Nadu region having good nutritional values. Fishes living in close association with may accumulate pesticides. In the present investigation, the toxic effects of the malathion LC50 0.25 ppm on some biochemical characteristics (total protein in gill, kidney, liver and muscle) of the freshwater carp fish, Oreochromis mossambicus were estimated. There is decreased in all tissues on compared with control. The results indicated the toxic nature of the pesticide malathion.