P.G. Department of Zoology, B.N.M.University, Madhepura, Bihar, India
Received : 29th April, 2020 ; Revised : 30th May, 2020
Abstract– While using several insecticides to control insect pests especially hemipterans in the agricultural field (Paddy), it has been found many pests become resistant to the common pesticides – deltamethrin (a pyrethroid) normally used to treat the crops for making them insect free. However, the pond also provides a good shelter to the bottom dwelling fishes like Singhi, Heteropneustes fossilis (Bloch) which are concomitantly exposed to the pesticides being used for insect control. In the present article the effect of a substitute pyrethroid-fenitrothion in place of deltamethrin on the respiratory rate of H.fossilis has been observed as because many of the farmers are trying this insecticide as safe to control the insect pests. Befittingly, the researchers are supposed to investigate the impact of safer variant on the coexisting fauna at like fishes. The effect of this pyrethroid on the respiratory function of the selected fish has been observed to be less stringent and lethal because its LC 50 & LD50 values are relatively low. In the normal fishes (control) per minute opercular beat as index of respiratory function has been found to be 30 while fenitrothion treated fishes at 10%, 20% & 30% concentration (weight/ volume in distilled water) for 15 days duration exhibited the increased opercular beat to 34, 39 & 52 per minute respectively. Higher concentration of fenitrothion could push the opercular beat to 52 per minute only as compared to 68 in case of Deltamethrin treatment. Gradual increasing trend by 20-30% and sharp peak of opercular beat have also been recorded in 30 and 45 days of exposure leading to high rate of casualty (in 30% concentration and 45 days of exposure).