Bioaccumulation of Lead, Cadmium and Chromium in Two freshwater Fish Species from River Kaduna (Nigeria)

There is increased global concern on the high rate of discharge of heavy metals into freshwater ecosystems from various anthropogenic sources due to their persistence, toxicity, bioaccumulation and biomagnification in the food chain. Fish are bioaccumulators of heavy metals hence; they are considered one of the key indicators of heavy metal pollution of freshwater systems. An investigation on the bioaccumulation of lead, cadmium and chromium in Clarias gariepinus and Oreochromis niloticus from river Kaduna was conducted. Sampling was done at seven different locations along the river. Muscle and liver tissues were collected from each of the fish species and analyzed for heavy metal concentration using atomic absorption spectroscopy. The muscle had higher levels of the heavy metals than the liver tissue. Both fish species are good bioaccumulators of these heavy metals however, O. niloticus is better than C. gariepinus. Furthermore, the muscle accumulated these heavy metals more than the liver. All heavy metals analyzed were above permissible limits hence, C. gariepinus and O. niloticus from river Kaduna are unsafe for human consumption. Therefore, there is an urgent need to regulate discharge of wastes into river Kaduna in order to prevent contamination by these heavy metals.