Coal mine effluent-led bioaccumulation of heavy metals and histopathological changes in some tissues of the catfish Clarias batrachus.

Coal mining generates huge quantity of toxic effluent which consistently pollutes the neighboring wetlands where the local inhabitants regularly cultivate edible fishes. In the present study the concentration of heavy metals Fe, Zn, Cu, Mn, Ni, Cd, Pb and Cr were analyzed in the water and various tissues of edible catfish Clarias batrachus reared in a pond receiving effluents from Rajrappa coal mine, Jharkhand, India. The metal concentrations in the pond water were dramatically higher (Fe 350%, Zn 423%, Cu 12%, Mn 7029%, Ni 713%, Cd 1700%, Pb 4333% and Cr 588%) than the safe limit of Environmental Pollution Agency (2003) as well as the control tap water. Excessive amounts of metals in effluent caused their substantial transfer to the different tissues of the catfish reared in such ponds. Results showed that accumulation of metals in fish tissues were in the following order: liver > kidney > air breathing organ (ABO) > gills > skin > brain > muscles. Among the various tissues the highest accumulation of most of the metals was recorded in the liver (2.05-271.28 mg/kg dry weight) and lowest in the muscles (1.39-30.27 mg/kg dry weight), while the concentration of metals in other tissues ranged in between. The accumulation of heavy metals in tissues appears to cause remarkable histopathological alterations in skin, gills, ABO, liver and kidney that might be leading to deleterious effect on fish physiology and consequently impact the consumers of such fishes.