Comparative Bioaccumulative Potential of Copper Cadmium and Lead by Gymnarchus niloticus and Heterobranchus bidorsalis in Pollution Prone Aquatic Environments of North-Western Nigeria

Fishes in aquatic environment accumulate metals in their tissues many times greater than present in sediment and water. Three organs: gills, muscles, and bones were collected from Gymnarchus niloticus and Heterobranchus bidorsalis for copper (Cu), cadmium (Cd), lead (Pb) and some mineral elements analyses using atomic absorption spectrophotometry in two separate seasons (January-February) and (August-September), and from four rivers (Bunsuru, Gagare, Rima, and Goronyo) receiving chronic inputs of run-offs from illegal mining and dyeing sites. Copper (Cu) level in gills of Gymnarchus niloticus season I sampling of River Bunsuru river was higher (3.30±0.36) µg/g but not significantly (p>0.05) above the WHO upper limit of 3.0 µg/g in sea foods while it was lower all tissues of Heterobranchus bidorsalis in the two seasonal samplings with the exception of bones in season 1 sample. Copper levels in Heterobranchus bidorsalis of Rima River for the two seasons were above the WHO limit, particularly those of season II. Lead (Pb) concentrations in all tissues (gills (4.75±0.87) µg/g, muscles (4.68±0.67) µg/g, and bones (4.34±0.34) µg/g) of Gymnarchus niloticus of Goronyo Dam season II samples were high than the WHO acceptable limit. Same is the case with Heterobranchus bidorsalis of Goronyo Dam season II. No tissues of the two fish species bioaccumulated significant level of cadmium (Cd). In general, there was no seasonal variation or differential accumulative potentials of copper and lead (Pb) in the two fish species. The only factor responsible for high bioaccumulation may be the level of metals in sampling sites. Other essential elements: Ni, Fe, Mg, Cr, Ca, Na and K were within the WHO acceptable limits for sea foods. The chronic discharge of wastes containing the minute quantities of lead and copper may lead to bioaccumulation and biotoxicity to aquatic species and to man who is the end receptor.