Trace metals in some benthic fishes of the Ikpoba river dam, Benin City, Nigeria

Abstract

The concentration of iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), cadmuim (Cd), chromium (Cr) and lead (Pb) in two benthic fish species (Mormyrops deliciosus and Mormyrus macrophthalmus netted from two locations (Okhoro and Low lift pump sites) on the Ikpoba River Dam, Benin City, Nigeria were determined using atomic absorption spectrometric technique. Sediment and water samples were also analysed for their trace metal concentrations. The range of trace metal concentrations (μg/g) in the fishes which is the focus of the study were as follows: Fe = 39.60 - 41.07 μg/g, Cu = 5.04 - 8.04 μg/g, Mn = 0.38 - 1.34 μg/g, Zn = 17.01 - 23.16μg/g, Ni = 0.24 - 0.48 μg/g, Cd = 0.79 - 0.98 μg/g, Cr = 0.38-0.91 μg/g, and Pb = 2.67-3.53 μg/g. Results show that relatively, higher metal levels were recorded in M. deliciosus than M. macrophthalmus. No significant differences (P > 0.05) were recorded between the concentrations of Fe, Mn, Zn and Pb in the two fish species. Significant differences (P < 0.05) were however, recorded between the concentrations of Cu, Ni, Cd and Cr in the fishes. The levels of Pb in the fish species exceeded the limit recommended in fish and fishery products by the Food and Agricultural Organization (FAO) of the United Nations. Also, the levels of Fe and Cd in the water exceeded the levels recommended for portable drinking water by the World Health Organization (WHO).

Keywords: Trace metals, benthic fishes, Ikpoba dam, Benin City, Nigeria