Abstract:
Clarias gariepinus were selected from four earthen ponds in Ijoka, Shagari, Agape and Oyemekun Akure in Ondo State. The head and edible tissues (flesh) of the fish, water as well as the bottom sediments and fish feeds were analyzed for Cr, Pb, Ni, Cd using Atomic Absorption Spectrophotometer while Hg was analyzed using UV Visible spectrophotometer. Higher concentration of heavy metals were found in the head than in the tissue. The concentration of Cr, Pb, Ni, Cd and Hg in Clarias gariepinus head ranged from 0.67 to 0.107, 0.000 to 0.002, 0.059 to 0.196, 0.000 to 0.002 and 0.005 to 0.007 mg/kg dry weight while the concentration of Cr, Pb, Ni, and Hg in the tissue ranged from 0.047 to 0.073, 0.000 to 0.001, 0.036 to 0.075 and 0.005 to 0.006 mg/kg dry weight respectively, Cd was not detected in the tissue. All metals analyzed were present in sediment, fish feeds and water samples. Cr and Ni were found to be above the WHO permissible limits in water samples. The estimated daily intake of Clarias gariepinus was below the reference dose established by the US-EPA and the hazard quotient values indicated that there was no risk to humans. Both the Hazard Quotient and Hazard Index for Hg, Cr, Pb, Cd, and Ni in all the Clarias gariepinus samples were below USEPA safe threshold limit. This suggests that the exposure of man to these heavy metals (Hg, Cr, Pb, Cd and Ni) from the consumption of the studied fish species is unlikely to pose any imminent health risk to humans.
