Samples of fish organs and water were collected from three sampling sites of Lakes Chamo and Abaya. A procedure consuming 12 mL mixture of HNO3-H2O2 for gill, kidney, liver and 1:2.5 mL mixture of HNO3-HCl for water samples for digestion of was developed. Concentrations of three metals in water and their accumulation in Tilapia (Oreochromis niloticus) and Barbus (Labeobarbus intermedius) fish species were determined using Flame Atomic Absorption Spectroscopy. Concentrations of metals in gills, kidney, liver and water varied (mg/kg): Zn 0.061-0.083, 0.047-0.076, 0.070-0.074, 0.011-0.024, respectively; Cu; 0.025-0.031, 0.028-0.043, 0.029-0.044, 0.023-0.092, respectively; Fe 2.934-3.583, 2.735-3.628, 0.809-2.723, 4.756-10.240, respectively. Most of the elements in water samples occurred below detection limit. The highest accumulations of iron (Fe) concentration were observed in liver and gill of Tilapia fish from Chamo Lake. Among the detected metals, zinc (Zn) showed the maximum bioaccumulation factor in both fish species from both lakes, while iron was the least bio accumulated metallic species. Using Pearson correlation, positive correlation was observed for the specific fish organ with water samples. There was no significant difference between the two lakes in accumulating trace metals however lake chamo had higher concentration.

Keywords: Bioaccumulation, Fish, Metals, Labeobarbus intermedius, Oreochromis niloticus