Study on the Distribution of Heavy Metals in Different Tissues of Fishes from River Benue in Vinikilang, Adamawa State, Nigeria

Aims: This study is aimed to determine the levels of some heavy metals in different species of fish and to compare the results with other standard values.
Study Design: The gills, liver, stomach, kidney, bones and flesh of four common fish species (Tilapia zilli, Clarias anguillaris, Synodentis budgetti and Oreochronmis niloticus) were collected for analysis of heavy metals.
Place and Duration of Study: This study was carried out in River Benue, Vinikilang, Adamawa State, Nigeria between the periods of January 2011 to January 2012.
Methodology: Sample collection and preparations were carried out using standard procedures. The concentrations of Cu, Zn, Co, Mn, Fe, Cr, Cd, Ni and Pb were carried out using Flame Atomic Absorption Spectrophotometer (AAS, Unicam 969).
Results: Iron was the most abundant metal in the studied tissues of all the fish species. In the fishes analyzed Fe accumulation was the maximum in all the organs but its highest value of 12.65 µg/g was significantly observed in the Gills of Synodentis budgetti (p <0.05), the liver of Tilapia zilli was second while the flesh of Heterotis niloticus shows the least value. From the result of this study, the tissues accumulation was observed in the order of gills>liver>stomach>kidney>bones>flesh. The gills of all the fish tend to accumulate significant high levels of heavy metal than other tissues. Accumulation of metal in different species is the function of their respective membrane permeability and enzyme system, which is highly species specific and because of this fact metals accumulated differently in the tissues of fishes as observed in the study.
Conclusion: Based on the above results, it can therefore be concluded that metals bioaccumulation in the entire fish species study did not exceeds the permissible limits set for heavy metals by FAO, FEPA and WHO. Therefore these fishes are fit for consumption.