Abstract:
Concentrations of cadmium, chromium, copper, lead, nickel and zinc were determined in the gill, liver, bone, head and muscle of Tilapia zilli, Tilapia dageti, Oreochromis niloticus and Clarias gariepenus and associated water and sediment from the Owena multipurpose dam. Heavy metals levels observed in the various organs of fish were in the order of Liver > Gill > Bone > Head > Muscle. Lead quantity was the most abundant heavy metal found in all the fish species organs with concentrations ranging from 0.30 mg/kg in muscle to 3.32 mg/kg in the liver. Mean concentrations of other metals were Cu (BDL – 0.28 mg/kg), Ni (BDL – 0.28 mg/kg), Zn (0.21 mg/kg – 1.70 mg/kg), Cr (0.05 mg/kg – 0.97 mg/kg) and Cd (0.03 mg/kg – 0.29 mg/kg). Levels of all the metals found in the muscle, head and bone were within the Maximum Acceptable Limit (MAL) for a food source while higher concentrations were recorded in the gills and liver, thus constituting potential health hazard to consumers of these organs of fishes. The mean concentrations (mg/L) of metals in the associated water samples were in the order: Pb (0.265), Zn (0.138), Cr (0.023), Cu (0.022), and Ni (BDL). These concentrations were lower than the World Health Organisation’s acceptable levels in water, except Pb which recorded higher concentration above the WHO limit . In the sediment samples, the mean concentrations (mg/kg) of Cd, Cr, Cu, Ni, Pb and Cr were 0.025, 0.758, 0.599, 0.368, 0.743, and 0.033 respectively. The order of heavy metal concentrations in sediment was Cr > Zn > Cu > Pb > Ni > Cd. These values were all lower than their probable effect concentrations (PEC) in sediment. The results of this study, however, established pollution of the water body which has inturn bioaccumulate in the organs of the fish.
