Bioaccumulation of heavy metals in fish (tilapia zilli and clarias gariepinus) organs from river Benue, North - Central Nigeria

Heavy metals concentrations were determined in fish organs of Tilapia zilli and Clarias gariepinus from River Benue along Makurdi metropolis sing atomic absorption spectrophotometer. The results indicated that Tilapia zilli gills contained the highest concentration (52.2%) of all the detected heavy metals, followed by the intestine (26.3%), while the muscle tissues appeared to be the least preferred site for the bioaccumulation of metals as the lowest metal concentration (21.5%) were detected in this tissue. Similarly, the Clarias gariepinus gills contained the highest concentration (40.3%) of all the detected heavy metals, followed by the intestine (31.6%), while the muscle tissue (28.1%) was the lowest. The trend of heavy metals concentration can be represented as: Cr > Zn > Cu > Fe > Mn > Cd > Pb for Tilapia zilli, while that of Clarias gariepinus was Cr > Zn > Fe > Cu > Mn > Cd > Pb. Tilapia zilli showed high bioaccumulation factors of 244, 229 and 178 for Cr, Zn and Cu, respectively. Claria gariepinus showed 232, 226 and 151 for Cr, Zn and Fe, respectively. This suggests that the fish samples could be used to monitor Cr and Zn pollution levels in the River Benue. (author)