Biochemical study of freshwater fish catla catla with reference to mercury chloride
Heavy metals are being passed on into aqueous environments through industrial processes, sewage disposal, soil leaching and rainfall. The concentrations of these heavy metals are sublethal or lethal to aquatic organisms when the duration of exposure to these metals are prolonged (Eisler and Gardener, 1973). It is well documented that effect of heavy metals are dependent upon the physical and chemical conditions of the environment especially water salinity, hardness, pH and dissolved oxygen and can act synergistically. Heavy metals from several industrial mining and other sources enormously contribute to the pollution problem in rivers and streams resulting in adverse impacts on biota including fish. Fish population is generally considered very sensitive to all kinds of environmental changes to which it is exposed as they are exclusively aquatic with external mode of fertilization. Certain stages in the life cycle of fresh water fish are more susceptible to environmental and pollution stresses (Von Westernhagan, 1988). Even though many studies are available in toxicity of various fishes (Jagadeesan et al., 1991; Margarat et al., 1991; Jagadeesan et al., 2001; Francis et al., 2002;), there is no report available on Catla catla. Hence the present study has been carried out on Catla catla with reference to mercury chloride.