ACUTE TOXICITY OF LAMBDA, CYHALOTHRIN PYRETHROID (KARATE 2.5 EC) ON THE FRESHWATER CATFISH: Heterobrachus longifilis (CURVIER AND VALENCIENNES)

摘要

Hetrobranchus longifilis fingerlings of mean weight 2.03±0.07 g and length 3.2±0.4cm were exposed to nominal concentration of lambda, cyhalothrin pyrethroid pesticide (Karate 2.5 EC) at 20 ppm, 40 ppm, 60 ppm, 80 ppm and 100 ppm through a gravimetric toxicant auto delivery system during a continuous flow through bioassay for 96 hours. The median lethal concentration 96-hr LC50 value with lower and upper limits of toxicities were 31.62 ppm (14.79 ppm, 82 ppm) respectively. The threshold value was 14.75 ppm. Statistical analysis of the data showed a significant difference between the 96-hr LC_(50) values for the experimental fish at p<0.05. During the exposure period, the fish showed such signs as increased opercula movement, hyperventilation, secretion of mucus, quick jerky movements, darkening of the skin and no response to gentle prodding before death finally occurred. The results suggest that although Karate 2.5 EC is a useful pesticide in agriculture and factory because of its residual effectson non-target organisms, it should be applied carefully using lower possible doses to avoid unforeseen toxicological effects.