Mercury Distribution and Concentration in Nile Tilapia (Oreochromis Niloticus) and Catfish (Clarius Gariepinus)

Mining activities from the recent past to the present pose a direct threat to the environment of Dunkwa-on-Offin and its neighbouring towns. The implication is that, the river and its fishes may be contaminated as a result of use of mercury by artisanal miners in their operations locally known as ‘galamsey’. It is perceived that uptake of mercury by planktons and fishes in the River Offin would be lethal to human beings, since the indigenes depend on the river as source of fish (protein). Little knowledge about mercuric toxication by artisanal gold miners and the indigenes makes it difficult to discourage the’ galamsey’ mines from the practice. In this study, analysis of the water, benthic feeders (Catfish) and surface feeders (Nile Tilapia) fish samples caught at decreasing distance from the point of ‘galamsey’ operations on the river was undertaken to determine the levels of mercury in the gills, liver, and muscle of the fishes. The total concentration of mercury in the samples from the River Offin, were determined, computed and compared with W.H.O quality guideline values. Mercury level in both water and the fish from the Offin River exceeded the W.H.O, values. The results indicated that the water and fish are contaminated with mercury and therefore pose health hazards, and should not be used for drinking and food, respectively.