Toxicity of Butachlor on Juveniles of Clarias gariepinus (Burchell, 1822).

Clarias gariepinus is an important valued fish widely culture and occur naturally in freshwater. Herbicides produce cumulative deleterious effects thereby reducing the survival and growth of fish. The acute and sub-lethal toxicity of the Butachlor on Catfish were investigated. The fish were exposed to 0 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, 25 mg/L and 30 mg/L acute concentrations of butachlor for 8weeks. Herbicides effects were measured using behavioural, heamatological, histopathological and growth parameters. The study revealed toxicity in a dose-dependent manner. Erratic swimming, gulping of air, restlessness, loss of balance, excessive secretion of mucus and finally death were observed in the exposed fish. Beats of the tail and operculum increased at 12 and 24 hours with increase in concentration, except at the 48th hour. The lethal concentration (LC50) value of butachlor was 14.08 mg/L for 96 hours of exposure. Mean Red Blood Cells (RBC), Haemoglobin content (Hg), Packed Cell Volume (PCV), mean corpuscular volume (MCV) and neutrophils decreased as the concentration of toxicant increased while White blood cell (WBC), mean corpuscular haemoglobin concentration (MCHC) and lymphocyte increased with increase in the toxicant concentration. Histopathological changes of gills include high proliferation of nuclei, total obliteration of the general morphology, loss of epithelial and mucous cells, and presence of hemorrhage. In the liver, there was compressed nuclear architecture, evidence of enucleated cytoplasm reflecting necrosis and distortion of periportal vein. There was significant decrease (p<0.05) in growth rates and nutrient utilization. Its concluded that butachlor was moderately toxic to Clarias gariepinus