Peter A. Gwaski, Stephen S. Hati, Naomi P. Ndahi and Victor O. Ogugbuaja
This study attempted to develop a decisive tool for pollution bio-monitoring triad (target specie-tissue-analyte) at the Lake Chad region of Nigeria. Six prominent commercial food fish species (Polypterus ansorgii, Clarias anguillaris, Oreochromis niloticus, Synodontis nigrita, Bagrus docmac, Lates niloticus) were collected and tissues (Gills, Kidney, Liver, Lung and Muscle) harvested and prepared for metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) analysis according to standard procedures. Metal determination was conducted by standard methods of flame atomic absorption spectrometry. Clarias anguillaris for Cd, Pb and Zn bio-monitoring was indicated, Oreochromis niloticus for Cu, Mn and Ni monitoring while Synodotis nigrita and Polypterus ansorgii were indicated for Cr and Fe respectively. However, Lates niloticus and Bagrus docmac indicated concern for tissue accumulation of metals, but did not show favourably high collective accumulation of any metal. On the question of target tissue, it was clearly indicated that the muscle tissue is a good candidate for Zn, Pb, Ni and Cu monitoring. The gill tissue revealed monitoring capacity for Mn, Fe and Cr, while liver tissue for Cd. The result of study suggested a high level of reliability on the use of Clarias anguillaris and Oreochromis niloticus as target species and confirmed the use of key tissues such as the muscle, gills and liver as pollution monitors of heavy metals. However, it is strongly suggested that further monitoring studies should be carried out with these species and tissues, at a different period to enable the calibration of the results of this study.
