Abstract
Oreochromis niloticus, exposed to lethal and sublethal concentrations of trichlorfon showed restlessness, excess secretion of mucus, convulsions, rapid body movements and difficulty in respiration. The 96-hours LC sub(50) value computed from a probit graph was 21.7 mg/l. The erythrocyte counts, haemoglobin concentration and haematocrit value increased significantly whereas leukocyte counts declined after trichlorfon exposure. Values of mean corpuscular volume (MCV) were also changed. Levels of protein, triglycerides and cholesterol in the serum of exposed fish were decreased while glucose levels increased after pesticide treatment.