Trace Metal Distribution in Tissues of Cichlids (oreochromis Niloticus and O. Mossambicus) Collected from Wastewater-fed Fishponds in East Calcutta Wetlands, a Ramsar Site

Industrial wastes are considered critical factors for disturbing the natural environment. Composite effluents tainted with different heavy metals are major environmental pollutants of varied wetland ecosystems (Wong 2003). Spread over 12 500 ha, The East Calcutta Wetlands, a Ramsar site in West Bengal, India (lat 22°33 ́ –22°40 ́N, long 88°25 ́–88°35 ́E), receives industrial runoff from at least 6000 largeand small-scale industrial establishments (including tanneries) and Calcutta metropolitan city wastewater throughout the year. The huge amounts of composite, heavy-metal-contaminated effluents (nearly 50 000 m3 · d–1) that flow down through a web of canals into the wetlands are also utilized by local farmers in pisciculture. Nearly 10 915 metric tons of fish were produced annually in 286 large wastewater fed fishponds (Bheris), over 30% of total wetland area (Chattopadhyay et al. 2002). Among several cultivated species of fish, Nile tilapia, Oreochromis niloticus L., and Mozambique tilapia, O. mossambicus (Peters, 1852), are familiar for their high fecundity and fast growth rate. Tilapias are also known to occupy different physical and trophic strata of aquatic bodies and being dependent on varied food sources (Pillay 1993, Chattopadhyay et al. 2002). ThereACTA ICHTHYOLOGICA ET PISCATORIA (2006) 36 (2): 119–125