Evaluation of toxicity of an organophosphate pesticide (Nogos) on behavior of the walking catfish (Clarias batrachus ) and it’s translocation in rice-fish ecosystem

Abstract

The Present study investigated the toxic effects of the pesticide Nogos on the walking catfish Clarias batrachus, and its translocation and residual accumulation in a pesticide administrated rice-fish ecosystem under laboratory conditions. The experiment was conducted in aquaria containing soil collected from the paddy. Nogos was applied at five concentrations such as 0.085 ppm. 0.170 ppm, 0.255 ppm, 0.340 ppm, 0.510 ppm and 0.595ppm. A control was maintained without Nogos. An LC₅₀ was obtained at a concentration of 0.31 ppm Nogos. Nogos at a concentration of 0.595 ppm showed LC₁₀₀ to the fish while lower concentrations of 0.085 ppm did not induce any mortality. Some behavioral changes noticed were: rapid opercular movement, jumping, jerking, erratic and circular movement, loss of equilibrium, leaching of mucous through anus, immobility and resting on the corners of the test aquarium, development of red spots on the dorsal surface, white spots on the abdomen. Maximum radioactivity was observed in water on day 2 (1.1 µg/g) of application of the pesticide. Soil sample showed peak radioactivity 0.55 µg/g on day 12 of application and thereafter declined slowly to background level by day 90 of pesticide application. Paddy root and shoot showed highest activity on day 24 (0.24 µg/g) and day 24 (0.20 µg/g), respectively.