Fate of Metals in Fish under Variable Sewage Input in Fish

Abstract- Use of raw sewage in aquaculture spelling prosperity to farmers is actually a veritable threat to the environment. Metal contaminated fish grown in the sewage-fed East Kolkata Wetlands, is potentially hazardous for the consumers. Alarmed by the increase of these persistent elements, an in-depth study was carried out to find out a possible way to reduce metal body burden in fish. The first part of the study deals with the quantitative analyses of metals in several species of fish reared in the sewage fed system. In the second part, sewage input in the ponds was temporarily stopped for six months that helped us to understand the depuration pattern of the accumulated metals from fish tissues. It was observed that, copper accumulates maximally with age in the fish liver especially in the benthic species such as Cirrhinus mrigala and Oreochromis nilitica. However, its depuration rate from the organ is low. After six months, the metal is completely excreted from muscle, skin, gills and kidney. Gills of Catla catla accumulate excess of zinc. Lead and zinc show size dependent increase in muscle, liver, kidney, skin and gills of fish but are steadily depurated in the relatively uncontaminated system. The rate of cadmium uptake and release is extremely low in fish. Index Terms- Depuration, fish, habitat, metals, wastewater