Assessment of trace metals in water samples and tissues of African catfish (Clarias gariepinus) from the Akaki River Catchment and the Aba Samuel Reservoir, central Ethiopia

Abstract

Concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in water and muscle of Clarias gariepinus from the Akaki River Catchment and the Aba Samuel Reservoir in Ethiopia during 2016 and 2017. The analyses were performed using ICP-OES. The results revealed that both the catchment area and the reservoir are affected by a high influx of trace metals. From measured values/permissible limits of Cr (0.101/0.05 mg ml⁻¹), Fe (1.47/0.2 mg ml⁻¹), Mn (1.06/0.05 mg ml⁻¹) and Ni (0.06/0.02 mg ml⁻¹) in water samples and Cr (10.66/1 mg kg⁻¹), Fe (66.48/43 mg kg⁻¹), Mn (2.28/1 mg kg⁻¹), Ni (4.93/1 mg kg⁻¹) and Pb (2.79/1 mg kg⁻¹) in the muscle of C. gariepinus, it is clear that values of these trace metals were above the permissible limits. Correlation analyses between trace metal concentrations in the muscle and length and weight of C. gariepinus indicated positive relationships in the dry and negative relationships in the rainy seasons, respectively. There is a necessity to carry out continuous monitoring of trace metal levels in the reservoir to understand human health risks associated with consumption of contaminated fish.

Keywords: Addis Ababa, bio-accumulation, Greater Akaki River, Little Akaki River, muscle, water pollution