Bioaccumulation of Mercury in Fish Species from the Ethiopian Rift Valley Lakes

Lindis Skipperud; Brit Salbu; Ermias Deribe; Alemayehu E. Masresha; Peder August Gade; Siri Berger; Bj?rn Olav Rosseland; Reidar Borgstr?m; Elias Dadebo; Zinabu Gebremariam; Ole Martin Eklo
The concentration and accumulation of total mercury (THg) in relation to size, diet and trophic position of the fish have been investigated in three fish species, i.e., Barbus intermedius, Oreochromis niloticus and Clarias gariepinus, from Lake Koka and Lake Ziway, Ethiopia. Stomach content analysis and stable isotope ratios of nitrogen (δ15N, ‰) and carbon (δ13C, ‰) were used to determine the diet and the trophic position of the fish. The fish species studied represented different trophic positions in the food chain of the lakes. The THg concentrations in each of the three fish species, B. intermedius, C. gariepinus, and O. niloticus, ranged between non-detectable (ND) and 0.9 mg kg–1 (ww) in Lake Koka, and between ND and 0.5 mg kg–1 (ww) in Lake Ziway, respectively. Significantly a higher concentration of THg was found in B. intermedius than in C. gariepinus and O. niloticus, in Lake Koka, whereas in Lake Ziway, B. intermedius had significantly higher THg concentrations than O. niloticus only. Species variation in total THg accumulation is attributed to size, diet and trophic position of the fish.
Fish Species; Rift Valley Lakes; Trophic Position; Hg
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