Comparative assessment of selected heavy metal load in three tilapiine species inhabiting Osinmo Reservoir, Southwestern, Nigeria
Olofinko, Ayomide Omolara
Adewole, Henry Adefisayo
Olaleye, Victor Folorunso
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The levels of selected heavy metal in the water and fillets of Tilapia zillii Gervais, Sarotherodon galilaeus Trewavas and Oreochromis niloticus Lineaus in Osinmo Reservoir were assessed and compared with established regulatory limits of WHO and FEPA with a view to providing information on the water and the fish fillet heavy metal load as well as the fillet bio-accumulative potential as a likely indicator for human fish consumption safety. Water samples and fish specimens were collected monthly from Osinmo Reservoir, Ejigbo, Southwestern, Nigeria for a period of 6 months. The descaled-dried fish fillet and water samples were digested and analysed for lead, chromium, iron, zinc and cadmium using Atomic Absorption Spectrophotometer (A.A.S.). The data obtained were subjected to descriptive and inferential statistics using SPSS 21. The results showed that zinc concentration which was the highest in the water samples and ranged between 144 μg l-1 and 288 μg l-1 was also the highest in the fillets of all the cichlid species. However, the concentrations were within the mandatory regulatory limits. The result of the study also revealed significant differences (P < 0.05) in heavy metal loads of the fish fillets between the cichlid fish species from Osinmo Reservoir. Irrespective of the month of sampling, the heavy metal levels in fish fillets samples were found to increase in the order: O. niloticus > T. zillii > S. galilaeus. However, the levels of lead (11.00–26.00 μg l-1 and 15.00–31.00 μgL-1) and cadmium (6.33–13.00 μg l-1 and 2.33–12.33 μg l-1) which was the least in both water and fish fillet respectively, were above the recommended regulatory acceptable limit of WHO and FEPA. The study concluded that the elevated levels of lead and cadmium in the water and the fish fillet samples assayed indicated that the two elements negatively impacted the fish fillet quality, thereby raising human health consumption safety issues.