The present study was conducted to explore the clinico-hematological and genotoxic effects in fresh water fish (Labeo rohita) exposed to various concentrations of butachlor (chloroacetanilide herbicide). For this purpose 30 fish weighing about 500-600 g were randomly allocated to five equal groups (A-E) and treated with various concentrations (0, 0.25, 0.50, 0.75 and 1.00 mg/L) of butachlor. Blood samples were collected from each fish after 48, 72 and 96 h of post treatment and fresh thin blood smears were made for cellular abnormalities. All the fish kept in group A did not reveal any clinical and behavioral ailments. However, various clinical signs such as rapid breathing, gasping at the water surface, restlessness, opercular movement, loss of equilibrium and erratic swimming were observed at higher concentrations (0.75 and 1.00 mg/L) of herbicide. The results showed that the erythrocyte, hemoglobin, hematocrit and lymphocyte values were significantly (P<0.05) decreased while significantly increased total leukocyte counts were recorded. Significantly increased incidence of different morphological and nuclear abnormalities such as pear shape erythrocyte, microcyte, tear shape erythrocyte, erythrocytes with micronuclei, lobed, blebbed and notched nuclei and cells with nuclear remnants were observed. The results suggested that butachlor poses serious clinico-hematological and mutagenic effects in fish and may be hazardous to the other species when those are exposed to this herbicide.

Key words: Butachlor, Fish, Hematology, Micronucleus assays, Nuclear changes