The bio accumulation of some heavy metals in some organs of two commerical fish; Clarias gariepinus (burchell) and Chrysicthys nigrodigitatus (lacepede) from River Niger, Onitsha shelf, Anambra state, Nigeria
The rate of heavy metals influx in the aquatic ecosystem has increased recently. This has been attributed to indiscriminate disposal of wasters, effluent from industries, colossal increase in automobiles and agricultural activities. Hence, the bioaccumulation of Zinc (Zn), Iron (Fe), Lead (Pb) and Cadmium (Cd) in samples of gill, Liver and offal of Clarias Gariepinus nigrodigilatus and Chrysichthys from 'Ose' fish landing site of River Niger, at Onitsha was investigated using Atomic Absorption Spectrophotometer (AAS). The result obtained showed that both fish species accumulated heavy metals. The heavy metals (mg/L) bioaccumulated by the whole fish gill, liver and offal of C. gariepinus were respectively: Zn (4.85, 2.66, 2.31, 2.94), Fe (5.85, 1.03, 1.90, 4.74), Pb (0.08, 0.02, 0.02, 0.11) and Cd (0.07, 0.09, 0.16, 0.16). On the other hand, the heavy metals (mg/L) bioaccumulated by the whole fish, gill, liver and offals of C. nigrodigitatus were respectively. Zn (3.57, 1.67, 2.13, 1.55), Fe (7.42, 2.59, 2.74, 4.64), Pb (0.11, 0.02, 0.01, 0.22) and Cd (0.09, 0.02, 0.06, 0.09). Except for Fe and Pb which exceeded the normal Permissible World Health Organization Standard ( 1-3 mg/Land 0.05 mg/L respectively in the whole fish and offals, other metals are within the acceptable range. In comparison, C. nigrodigitatus shown in the study to have more metal bioaccumulation than C. gariepinus. The implication is that the river is polluted and this could affect the biota especially fish and ultimately man along the food chain Recommendations for monitoring and controlling of heavy metal pollution were highlighted.
Keywords-Bioaccumulation, heavy metals, Clarias gariepinus Chrysichthys nigrodigitatus