Assessment of Heavy Metals Accumulation in Tissues of Tilapia zilli and Clarias gariepinus Found in Lake Akpoko and River Benue, Nigeria

Water run-offs from up lands polluted by human activities constitute a potential source of heavy metal contamination of the aquatic flora in surrounding water bodies. For instance, lake Akpokpo has abattoir effluents emptying into it all through the year. To investigate this, two commonly consumed fish species, namely Tilapia zilli (Tilapia fish) and Clarias gariepinus (cat fish) were assessed for heavy metals contamination in the gills, intestines and muscles of freshly caught samples following standard procedures . Heavy metals were determined using atomic absorption spectrophotometer. The results showed that the gills of Tilapia zilli from river Benue has the highest concentration of all the metals, while the muscles of cat fish from the lake has the lowest metals concentration. Heavy metals accumulation in the samples ranges in the order TGR>TGL>TIL>CGL>CGR>TIR>CIL>CIR>CMR>TML>CML. In the organs, the range of accumulation is Gills > intestine > muscles. The concentration of heavy metals in the river is in the order Fe> Zn >Cr>Pb>Mn>Cd>Cu. Lead was 12.15 mg/kg in the gills of Tilapia zilli , but 2.08 mg/kg in the muscles of cat fish, both from the lake. The river samples showed lead concentration of 11.585 mg/kg and 2.24 mg/kg, for the Tilapia gills and cat fish muscles respectively. Fishes constitute a staple food for river bank communities. Considering daily permissive intake limits, discussions and recommendations were made. Key words : Heavy metals pollution, Tilapia zilli , Clarias gariepinus, water pollution