Heavy Metal Analysis of Central Cross River, Nigeria using Nile Tilapia (Oreochromis niloticus) and Water as Bio-indicators

The most of the fish consumed in the Cross River State are brought from Cross River, the quality characteristics of such fishes are foremost importance. Therefore, this study was carried out to provide information on heavy metal concentrations in the water and muscles of Nile tilapia (Oreochromis niloticus), a commercial fish species available in the markets of Cross River State and to make people aware of the possible health risk associated with their consumption. Samples were collected from nine sites along the length of the river and were designated as Stations A (Itigidi), B (Ekori), C (Ahaha), D (Ofombogha), E (Obubra), F (Ochong), G (Alesi), H (Okuni) and I (Ikom). The heavy metal profile (Pb, Mn, Zn, Cd, Cr, Ni, Cu, Fe, Al and Co) was assessed using Atomic Absorption Spectrophotometer. Results of metal profile observed were in order of magnitude in Itigidigi > Ekori > Ahaha > Ofombogha > Ochong >Obubra > Alesi > Okuni > Ikom, while the concentration of heavy metals in the sampling stations were in the order of magnitude of fish > water. Most of the metal concentrations were below the maximum allowable levels set by the WHO, FEPA, and USEPA except zinc with mean concentration of 0.27±0.047μg.g-1 in fish and 0.31±0.18μg.g-1 in water which were above recommended limit of 0.0766μg.g-1 of USEPA at Itigidi and Ekori respectively . This implied that the waste assimilation capacity of the river is high, a phenomenon that could be ascribed to continuous water exchange, dilution, and sedimentation. This is an indication that an urban and industrial waste discharged into the Central Cross River has a significant effect on the ecological balance of the river. Thus, fish species harvested from the river may be safe for human consumption.