Fishes are important bioindicators of the integrity of aquatic ecosystems and were used to evaluate the status of heavy metal pollution in an oil impacted aquatic ecosystem (Imo River) located within the Niger Delta region of Nigeria. The concentrations of Cd, Cr, Cu, Fe, Pb, Mg, Mn, Ni and Zn were determined using inductively coupled plasma spectrometer (Optima 3000-Perkin Elmer). The metal concentrations in liver and muscle tissues of Ethmalosa fimbriata (bonga fish), Chrysichthyes nigrodigitatus (catfish), Lutiana ava (pink snapper), Stellifer lancelatus (croaker) and Tilapia guineensis (Tilapia) were consistently higher in the livers than in the muscle tissues of all the five fishes. Magnesium concentration was anomalously higher in the muscle tissue than liver of C. nigrodigitatus, E. fimbriata and L. ava but not in S. lancelatus and T. guineensis. Muscle-liver ratios (MLRs) of the respective heavy metals ranged between 0.089 (CuM:CuL) and 1.299 (MgM:MgL) for C. nigrodigitatus, 0.186 (CrM:CrL) and 1.401 (MgM:MgL) for E. fimbriata, 0.194 (CuM:CuL) and 1.498 (MgM:MgL) for L. ava, 0.131 (CuM:CuL) and 0.646 (NiM:NiL) for S. lancelatus, 0.009 (CuM:CuL) and 0.916 (MgM:MgL) for T. guineensis. Interestingly, copper indicated least MLR in almost all the investigated fishes except in E. fimbriata. Magnesium showed the highest MLR in all fish species except in S. lancelatus. On the other hand, the cadmium/zinc ratios were higher in the muscle tissues than livers of all the fishes analyzed except in E. fimbriata. The threshold contamination value for human dietary risk was however, not exceeded.
N.U. Benson, M.U. Etesin , J.P. Essien , I.U. Umoren and M.A. Umoh , 2006. Tissue Elemental Levels in Fin-Fishes from Imo River System, Nigeria: Assessment of Liver/Muscle Concentrations Ratio. Journal of Fisheries and Aquatic Science, 1: 277-283.