Abstract

This study assessed and monitored the concentrations of Cu, Mn, Zn, Cd, Cr, Ni and Pb in the gills, offal, muscle and liver of a commercially important mudfish (Parachanna obscura) from Ogba River, Benin City, Nigeria between January and December, 2005. The same metals were also determined in the water of the river. The results revealed that the concentrations of all the metals in the tissues (offal, gills, muscle and liver) were higher than the concentrations of the metals in water and indicated bioaccumulation. The concentrations of all the metals in water were below WHO and FEPA recommended limits and suggested that the water of Ogba River was suitable for drinking, but the concentrations of Cu, Mn, Cr, Ni and Pb in all fish tissues exceeded these limits and indicated that the fishes of Ogba River, as far as these metals were concerned, were unfit for human consumption. Consequently, close monitoring of metals pollution and the consumption of the fishes of Ogba River is recommended with a view to minimizing the risks to health of the population that depend on the river for their water and fish supply.

Key words: Heavy metals, water, fish, Ogba River, Nigeria.