Toxicological alteration of Dimethoate (rogor) insecticide against freshwater fish Colisa fasciatus and Mystus mystus

Like other organophosphates, dimethoate is an acetylcholinesterase inhibitor which disables cholinesterase, an enzyme essential for central nervous system function. Dimethoate insecticide can be used for both indoor and outdoor purposes to eliminate a number of insect pests under different condition. Dimethoate, one of the most extensively studied pesticides, may induce many significant changes in fishes. The aim of the present study is to determine the toxicological action of dimethoate on freshwater teleost fishes. The Dimethoate has shown strong piscicidal activity in freshwater fish Colisa fasciatus and Mystus mystus for all the exposure periods (24 or 96h) in time as well as dose dependent manner. The LC50 values decreases from 0.084 ppm (24h) to 0.059 ppm (96h) in winter season (water temp.19⁰) Colisa fasciatus and LC50 0.028 ppm (24h) to 0.010 ppm (96h) in summer season (water temp. 23⁰). The LC50 decreases 0.039 ppm (24h) to 0.022 ppm (96h) in winter season against Mystus mystuus and LC50 0.040 ppm (24h) to 0.015 ppm (96h) in summer season. The pesticide exposure may also fatal to many non- targeted organisms like fish where it hampers its health through impairment of metabolism, occasionally leading to the death of the fish.