CONCENTRATIONS OF METALS IN THE FLESH (MUSCLES) OF FIVE COMMERCIALLY IMPORTANT FISHES OBTAINED FROM THE GREAT KWA RIVER, CALABAR, NIGERIA

This study was carried out to provide information on metals concentrations in the muscles of five commercially important fish species available in the Great Kwa River and to evaluate the possible risks associated with the consumption of fish with high level of metals. The concentrations of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni) and lead (Pb) were determined in the muscles of Chrysichthys nigrodigitatus, Clarias gariepinus, Oreochromis niloticus, Heterotis niloticus and Parachanna obscura. The levels of the metals were obtained spectrophotometrically by using Perkin-Elmer Analyst 300 Atomic Absorption Spectroscopy (AAS). P. obscura concentrated the highest level of Cr and Cu while C. nigrodigitatus had the highest level of Fe and Pb. Cd and Ni concentrations were highest in O. niloticus. The least detectable concentration of 0.011±0.02 was measured for Hg in P. obscura. Results showed that all other metals present in the study apart from Fe in all the fishes and Cr in P. obscura and O. niloticus were lower than the limits permitted by Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO). Concentrations of metals in the fish may be due to industrial and municipal effluent discharges which find their way into the river. Some anthropogenic activities which take place within and along the river banks can also introduce these metals in the river. Thus, anthropogenic or industrial activities that can pollute the water body should be minimized since metals can bio-accumulate in some fishes over a long period of time.