The aim of present investigation was to screen the acute toxicity of paraquat to the Clarias batrachus for 96 hours at two different selected level of pH (5.6 ±0.3 and 7.6 ±0.3) to determine the LC50 values for different concentrations by Probit analysis statistical method. However, the presumable safe concentration was also noticed and found to be too high as compared to safe dischargeable concentrations. The changes in behavioural pattern viz; imbalance and whirling movement, erratic swimming, vertical hanging for sometimes, reddish colour of the gills, abnormal opercular movement etc. were also noticed in the studied fishes during bioassay test. The LC50 values for two different selected pH were correlated and were found to be significant at 0.05 levels. Oneway ANOVA was also performed between Median lethal concentrations (LC50’s) of Paraquat for 24, 48, 72 and 96 hrs to Clarias batrachus at both the pH of 5.6 ±0.3 (Group-1) and 7.6 ±0.3 (Group-2). Results exhibit that paraquat are highly toxic to freshwater fishes, Clarias batrachus since their LC50 values were noticed in ppm. This study has great importance from agricultural point of view since it helps to manage the aquatic animals, particularly fishes.
