Acute toxicity of an organophosphorus insecticide monocrotophos and its effects on behaviour of an air-breathing fish, Anabas testudineus (Bloch)

Acute toxicity of insecticide monocrotophos to the fresh water fish Anabas testudineus was studied using static bioassay method. The 24, 48, 72 and 96 h LC₅₀ were found to be 22.65, 21.2, 19.75 and 19 ppm respectively. The calculated safe concentration of monocrotophos was 0.19 ppm. Decrease in opercular movement, loss of equilibrium, increase in surfacing behaviour, change in body colour, increase in mucus secretion all over the body, irregular swimming activity, increase in nudge, nip and aggressiveness were observed in fish on exposure to monocrotophos.