Study of toxicity and behaviour of freshwater fish, Channa punctatus (Bloch) after intoxication of carbaryl (1-naphthalenyl methylcarbamate)

Abstract

The effects of carbaryl (1-naphthalenyl methylcarbamate), commonly used in agricultural operations, have been studied with reference to mortality and behavior of the freshwater fish, Channa punctatus. Pesticide was administered to glass aquaria containing the experimental fish by glass rod without disturbing the test animal. Thus the pesticide was imbibed via the gastrointestinal tract and the surface of gill and skin of the experimental fish. Among the five concentrations (4, 6, 8, 10, 12ppm) prepared, the concentration of 12 ppm, carbaryl caused 100% mortality within 48 hr. LC50 of carbaryl is 8.71 ppm to C. punctatus. But such sublethal concentrations increased the frequency of opercular beats and abnormal and erratic swimming movements. The latter response was dose-dependent. These behavioral changes were the immediate response to the toxicant and were indicators of possible stress. The fishes tried to avoid the toxic water with fast swimming and jumping. Their fins became hard and stretched due to stretching of body muscles. They secreted mucus from whole body continuously and soon thick layer of mucus was found deposited in the buccal cavity and gills. Finally fish lost their balance and consciousness, engaged in rolling movement and became exhausted and lethargic. Soon they settled at the bottom of the tank, and after some time their bellies turned upward and the fish died, while the opercula remained wide open exposing the gills. They were lethargic and at the time of death exhibited transient hyperactivity before collapsing.