ABSTRACT
Heavy metals, such as lead, cadmium, nickel, cobalt and chromium are persistent environmental pollutants. These toxic substances enter water bodies through various anthropogenic activities, including industrial discharges, agricultural runoff, and urbanization potentially leading to the accumulation in aquatic organisms. This study evaluated the organ-specific uptake of heavy metals in benthic and pelagic fishes of Ikpoba river. Two species of fishes were selected based on their ecological importance, abundance, and potential exposure to heavy metal contamination, Tilapia zilli representing pelagic and Clarias gariepinus representing benthic. The liver, gills, muscle and gonads were analyzed for heavy metals (lead, cadmium, Nickel, cobalt and chromium) using standard method. Results showed that the levels of metals in the fishes were higher than that in the surrounding waters and sediment. The distribution of lead, cadmium, nickel, cobalt and chromium across fish organs showed significant variations where the gills had the highest concentration of 0.51mg/kg and the gonads had the lowest concentration of 0.11mg/kg. Heavy metal concentrations in the fish organs (gills – 0.51mg/kg, muscles – 0.25mg/kg, liver – 0.24mg/kg, brains – 0.15mg/kg, and gonads – 0.11mg/kg) was in the order; gills > muscles > liver > brains > gonads in the various fish species. The mean concentrations of nickel recorded in the gills (1.48mg/kg) and muscles (0.07mg/kg) of fish organs in this study exceeded the permissible limits for nickel (0.5 – 0.6mg/kg) set by WHO for fish and fishery products. Furthermore, the mean concentration of lead in the brains (0.15mg/kg) and gills (0.122mg/kg) also exceeded the permissible limits for lead (0.05mg/kg) set by WHO. The presence of high heavy metal concentrations in fish organs poses serious concerns because of its potential health risks to human population relying on these fishes as source of food.
