ABSTRACT
In the last decades, aquatic contamination by heavy metals has become a global crisis. Potential toxic metals (PTMs) in aquatic system are produced from natural and anthropogenic sources and the degree of contamination in fish is dependent on the sampling site, pollution types as well as mode of feeding of the fish The concentration of PTMs such as such as manganese ( Mn), iron (Fe), copper (Cu) , zinc (Zn), cobalt (Co), chromium (Cr), cadmium ( Cd) , lead (Pb) and nickel (Ni) in silver Catfish (Chrysichthys Nigrodigitatus) , Tilapia (Tilapia Zilli), water and sediment collected from Majidun and Igbede rivers were investigated and analyzed using buck scientific model 210 atomic absorption spectrophotometer (AAS) . Iron (Fe) was the most abundant in all the samples analyzed with the highest level of mean concentration recorded in the sediment with a value of 0.56 µg/g as against 0.20 µg/g, 0.19 mg/L 0.18 µg/g recorded for Tilapia, water and Silver Catfish (Chrysichthys Nigrodigitatus ) collected from Majidun river and a similar trend was noted for all the samples from Igbede river with the sediment recording a value of 215.8 µg/g. The high value obtained in the sediment may be associated with the natural abundance of iron in Nigeria soil as well as been a major depository of heavy metal. The accumulation of heavy metals in the samples analyzed for Igbede river were in the order of magnitude Fe >Mn>Zn > Cu compare to Majidun river with an order magnitude of Fe > Zn >Mn >Cu, Fe > Mn > Zn >Cu > Co >Ni, Fe > Mn > Zn > Cu and Fe > Zn > Mn > Cu for water, sediment, Tilapia and Silver Catfish (Chrysichthys nigrodigitatus ) respectively. Pb, Cd, Ni, Co and Cr were not detected in the analyzed samples from both river except for Igbede tilapia that recorded 1.7 µg/g of Ni and sediment of Majidun river that had a low concentration of Ni and Co respectively. The accumulation of iron and zinc by the fishes from both the surrounding water, sediments and their diet were relatively low and are below permissible limits of Food and Agriculture Organization (FAO) and Lagos State Environmental Protection Agency (LASEPA) for daily intake which implies that both Chrysichthys Nigrodigitatus and Tilapia Zilli the analyzed in both Majidun and Igbede River are safe for human consumption.