Abstract
Rotenone is a common pesticide used to get rid of objectionable predatory fishes and other undesirable organisms from water bodies including lakes, streams, ponds, lakes and rivers. Two experiments were planned to evaluate its toxicological impacts on Nile tilapia, Oreochromis niloticus fingerlings. LC50 [Lethal concentration] after 96 hours, was valued using different concentrations of rotenone (10, 20, 30, 40, 50 and 60 μg / L). Another experiment was constructed to establish its sublethal toxicity outcomes whereas, fish were subjected to 1/10 and 1/2 of the LC50 value for subsequent 5 weeks. For this objective, Liver functions tests [Aspartate transaminase (AST) and Alanine transaminase (ALT)], Lipid peroxidase (LPO), Catalase (CAT), Superoxide dismutase (SOD), Malondialdehyde (MDA), Glutathione peroxidase (GPx) and Glutathione S-transferase (GST) enzymes activities were considered. Results presented that rotenone-induced substantial mortality in O. niloticus fingerlings with LC50 of 30 μg / L, and fish exhibited neurological signs and respiratory distress before death. In both sublethal doses of rotenone throughout the 5 weeks of the second experiment, the exposure to rotenone caused an elevation in AST and ALT, LPO, and CAT, and GST activities. However, reduction in GPx, SOD, and MDA activities was observed. It can be concluded that rotenone is a tremendously toxic pesticide for O. niloticus, and it is important to create harmless processes for its direct uses and to find out innocent discharge in effluents.

Key words: Rotenone - LC50 - Oreochromis niloticus - Liver aminotransferases - Antioxidant enzyme activities - Lipid peroxidation.