Bioaccumulation of Heavy Metals by Clarias gariepinus (African Catfish) in Asa River, Ilorin, Kwara State

Background. Harmful wastes and other dangerous industrial by-products constitute major sources of environmental pollutants in Nigeria. Industrial pollutants discharged into the environment contain organic and inorganic pollutants in dissolved, suspended and insoluble forms. Fishes are known for their innate potential to bioaccumulate heavy metals in their muscles and various organs. Objectives. The present study aimed to assess the bioaccumulation status of heavy metals in selected organs and tissues of African catfish in Asa River, Ilorin, Kwara State, Nigeria. Methods. Three sampling points (A (upstream), B (point of discharge) and C (downstream)) were selected in relation to industrial effluents that enter the river. African catfish were randomly harvested from each site using fishing nets at the three sampling points. The samples were digested and subjected to atomic absorption spectrophotometric analysis. Statistical analysis of data was carried out using the Statistical Package for the Social Sciences (SPSS) version 20 and two-way analysis of variance (ANOVA) to compare data among sites and organs. Results. The present study found that the bioaccumulation level of heavy metals in selected organs and tissues of African catfish in Asa River, Ilorin, Kwara State, Nigeria was very high and the level of accumulation of heavy metals increased downstream. Accumulations were much higher during the dry season (especially in the month of February) and relatively low during the peak of the rainy season. Conclusions. Heavy metals at elevated levels in the aquatic environment can accumulate in fish tissues and organ, and therefore fish from the Asa River are not fit for human consumption. Competing Interests. The authors declare no competing financial interests