Bioaccumulation of heavy metals in tissues of marine organisms has been identified as an indirect measure of the abundance and availability of metals in the marine environment. Monitoring fish tissue contamination therefore serves an important function as an early warning indicator of sediment contamination or related water quality problems and enables appropriate action to be taken in order to protect public health and the environment. Trace elements contents of tissues of Clarias gariepinus from River Galma, River Kubanni and Fish farms in Zaria, Nigeria were investigated in the current work using Schimadzu atomic absorption spectrophotometer (model 6800, Japan) after wet digestion. Cadmium, Chromium and Nickel residues in the fish exhibited different patterns of distribution among the selected tissues and localities. It was evident from our study that, liver was the site of maximum accumulation for the elements followed by gills while muscle was the overall site of least metal accumulation. Cadmium and Chromium concentrations in fish tissues followed the order River Galma > River Kubanni > Fish Farms while Nickel followed the trend River Kubanni > River Galma > Fish Farms. The range of concentration was 0.02-16.33 mg/kg for Cadmium, 0.03-8.12 mg/kg for Chromium and 0.09- 13.90 for Nickel. These values were found to be higher than WHO/FAO maximum recommended limits in food fish. Consumption of Clarias gariepinus from the areas under study therefore poses serious toxicological risk. Implications of findings to public health are fully discussed.
 

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