Comparison of heavy metals burden in two freshwater fishes Wallago attu and Labeo dyocheilus with regard to their feeding habits in natural ecosystem

We examined Zn, Ni, Cr, Cu, Cd and Pb in the skin, gills, intestine, liver and muscle of two fresh water fishes, Wallago attu (Bloch and Schneider, 1801) and Labeo dyocheilus (McClelland, 1839). The aim of the study was to determine the metal accumulation pattern of two species occupying different feeding zones in the same habitat. Metals accumulated in the order Zn>Cr>Cu>Pb>Ni>Cd in the body of Wallago attu. Metal abundance in different organs of this fish was skin>gills>muscle>intestine>liver. Similarly, the order of metal accumulation in the body of Labeo dyocheilus was Zn>Cr>Cu>Pb>Ni>Cd, while metal abundance in different organs of this fish was in the order liver>muscle>skin>intestine>gills. The order of metals bioaccumulation in both the species was different, but in both species Zn was the highest and Cd was the least accumulated metal. Skin, gills, intestine, liver and muscle of Labeo dyocheilus accumulated 43%, 36%, 63%, 105%, 86%, higher metal concentrations as compared to that of Wallago attu. Overall, Labeo dyocheilus accumulated 65.2% extra heavy metals burden as compared to Wallago attu. Our findings suggest that omnivorous fish may bioaccumulate more heavy metals than the carnivorous fish in natural habitats.