Background. The potential toxicity of metals in water may have detrimental effects on the biochemical processes of aquatic organisms, especially fish, which serve as a source of protein in the protein-deficient Nigerian diet. Objective. The present study aimed to determine the concentration of heavy metals in African catfish (C. gariepinus) and investigate the health risk associated with heavy metals in fish. Methods. Heavy metal concentrations in the water samples were determined using atomic absorption spectrophotometry (AAS) and particle induced x-ray emission spectroscopy (PIXE) for sediment and fish tissues/organ samples. Results. Mean nickel (Ni) concentrations differed significantly (p<0.05) by sample type in both the dry and rainy seasons. Similarly, during the rainy season, mean lead (Pb) concentrations in all of the samples from Osogbo differed significantly (p<0.05) by type, with the highest concentration in fish muscle (10.11±1.21 μg/kg) and the lowest Pb concentration in pond water (1.72±0.05 μg/L). Mean chromium (Cr) concentrations of samples from the Ewuru/Rara stream in Yakoyo also differed significantly (p<0.05) by type, with the highest concentration in fish muscle (113.10.±10.07 μg/kg) and the lowest concentration in pond water (3.31±0.22 μg/L). Discussion. Heavy metal concentrations in pond and stream sediment samples revealed transport and deposition processes where trace metals are deposited and incorporated into sediment after entering the aquatic system. Iron (Fe) had the highest concentration levels ranging from (196.21 μg/g – 698.65 μg/g) in the three locations investigated, while Pb levels were the lowest, ranging from (9.05 μg/g – 75.30 μg/g). Conclusions. In general, the concentrations of Cr, copper (Cu) and manganese (Mn) were below standard guidelines, while the concentrations of nickel (Ni) and lead (Pb) were fairly higher than the tolerable limits for water pollution standards. Competing Interests. The authors declare no competing financial interests
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