Heavy metals analysis of S. schall and O. niloticus fish species sold at Otuocha Market, Anambra State, Nigeria

Abstract

The potentials of heavy metal pollution in natural environments have necessitated the need to determine the presence of heavy metal pollutants in the surface waters and possible bioaccumulation in the inhabiting fish species and other aquatic organisms. This study thus aimed to determine the heavy metal species that occur outside their recommended ranges in the test fish species and two Cichlid fish species namely, Synodontis schall and Oreochromis niloticus were selected for the analysis. Water samples were taken to assess the concentrations of these heavy metals in the river while tissues and organs of the test fish samples were extracted for further analysis to determine the cumulative tendencies of these metals in the organisms. All the heavy metals (Cd, Zn, Mn, Cu, Pb) were detected in the fish organs except copper (Cu) which was not detected in the fillet/tissue. The metals occurred in the order; Pb > Zn > Cd > Cu > Mn in both fish species. The gill emerged as the organ with the highest concentration of heavy metal with a value of 100.92ppm of lead in Synodontis schall and 111.34 ppm in Oreochromis niloticus. The high concentrations of Zinc and Lead found in the fish organs were compared with the habitat and discovered that the concentrations were high compared to the lower levels found in the river water. Although Zn occurred at very high concentrations, they were still below the threshold recommended by WHO/FAO. However, Cadmium and Lead exceeded their permissible limits, Lead occurred in outrageous amounts while other metals tested (Mn, Zn, Cu) fell within acceptable ranges. Nonetheless, care should be taken and environmental laws and policies guiding the use and discharge of harmful substances put in place to check the influx and accumulation of these toxicants which pose as threat to man. Metal pollution results in abnormal physiological function of the body cells when they exceed these limits and so guidelines on the use of related products and industrial discharge of effluents should be adhered to and penalty measures taken out on defaulters.