Effects of Dichlorvos on Freshwater Fish Rohu (Labeo rohita Hamilton,1822)

Abstract

Pesticides are applied to control the pests indoor and outdoor; however, their remarkable amount reaches the aquatic system through various routes like run-off, leaching, spray-drift, and effluent from factories. These pesticides are reported to have a negative metabolic impact on different non-target aquatic organisms like fishes. Thus, the present study was aimed to evaluate the acute toxicity of commonly used organophosphate pesticide dichlorvos to the freshwater fish Rohu (Labeo rohita). The experimental setup was designed to test the acute toxicity, advanced behaviour, and some haematological as well as biochemical analysis for a period of 96h. The LC₅₀ values for dichlorvos after 96hr treatment was found to be 11.36 mg/L. In treated fish, alterations in various behavioural patterns respiratory metabolism, opercular beat rate, and blood parameters were examined for sub-lethal end-points following 1h, 24 hr, 48 hr, 72 hr, and 96 hr exposure. Accelerated opercular beat rate (P < 0.05) was recorded in pesticide-exposed groups in comparison to control. Though the respiratory metabolism was not significantly affected, an increment in oxygen consumption rate was recorded. The pesticide stress caused a significant elevation in haemoglobin (P < 0.01) whereas total protein content was significantly dropped (P < 0.05). Glucose content was found to be increased (P > 0.05) in the pesticide group, compared to the control. Some general behavioural changes such as erratic movement, gulping, schooling, mucus secretion, equilibrium, aggregating behavior, and paleness in the body were observed in pesticide-exposed fish. The acute toxicity data reported in this study can be used to assess the tolerance level of Rohu to insecticide dichlorvos.