Seasonal variation in concentrations of heavy metals in catfish (Clarias buthupogon) from River Oluwa and River Owena, Southwestern, Nigeria

Fish represents one of the main sources of the exposure of people to heavy metal toxicity, and it is the main source of trace elements in the human diet. Most of the human health risk related to fish consumption is associated with metal-contaminated fish. In this study, concentrations of Fe, Cu, Mn, Cr, Zn, Hg, Pb, Cd, Ni, and Ni were determined in catfish (Clarias buthupogon) collected from River Oluwa and River Owena in the dry season and rainy season, to investigate the status of heavy metal contamination. Samples were analyzed using the AAS using GBC Avanta PM ver 2.02. The concentrations of most of the metals were higher in the dry season than in the rainy season. Fe, Cu, Zn, Cd, Ni, and V concentrations were lower than the maximum permissible by ingestion. However, the mean concentration of Mn was 7.10 ppm in the dry season and 3.14 ppm in the rainy season while the mean concentration of Cr in the rainy season was 3.26 ppm, 2.81 ppm in the dry season, and 2.54 ppm in the rainy season which were higher than the allowed levels for human consumption proposed by Food and Agriculture Organization (FAO) (1983). Catfish from River Oluwa and River Owena should be consumed with caution.

 Keywords: Catfish, heavy metal, contamination, season, concentration