Bioaccumulation of Mercury, Arsenic and Copper in Two Freshwater Fish Species from River Kaduna (Nigeria)

An investigation on the bioaccumulation of Hg, As and Cu 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. Water samples were also analyzed for these heavy metals using the same technique. Results reveal that the river is contaminated with these heavy metals. The liver had higher levels of Hg, As and Cu than the muscle tissue. Furthermore, C. gariepinus was a better bioaccumulator than O. niloticus. Mercury level was above permissible limits in both fish species while As was above maximum limit only in O. niloticus. Therefore, C. gariepinus and O. niloticus from river Kaduna are unsafe for human consumption. Hence, there is an urgent need to regulate contamination of River Kaduna.