Differences in Toxic Metals Bioaccumulation in Commercial Fish Species from Winam Gulf of Lake Victoria, Kenya
Fish have two main exposure pathways to external metal concentration: through the gills, water and diet. In freshwater, waterborne routes may be significant contributors to metal uptake in the tissues of fish. In this study, four toxic metals (Pb, Cd, Cr and Cu) were analyzed in three commercial fish species (Oreochromis niloticus, Lates niloticus and Rastrineobola argentea) relative to the metal concentration in the water to determine the metal concentration and bioaccu mulation relative to changes in the external metal in Lake Victoria, Kenya under field condition. The fish were sampled at 5 sites on the lake, thus Site 1, Port Victoria; Site 2, Yala River Mouth; Site 3, Kisumu; Site 4, Kendu Bay; Site 5, Macalda.) The metals were analyzed by atomic absorption spectrophotometer (AAS). The results of heavy metal concentration in the fish are equivalent or lower than levels reported in ichthyofauna worldwide. Levels varied among tissues and species, but were seldom influen ced by the gender and fish length (P > 0.05). Regression between metal levels in liver appeared stronger (R2 > 0.6) than that between the metal levels in the whole body and in water (R2 < 0.5) implying higher detoxification by liver and the existence of detoxification processes by the liver. However, level differences between fish from the five sites reflect differences of elemental availability and differences in uptake and/or depuration from both environments.
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