Author(s): Lokhande MV

Abstract: Dimethoate, is highly contaminating aquatic ecosystems as a toxic pollutant, it was used for acute toxicity test on freshwater fish Rasbora daniconius. In the present investigation were the toxicity tests were conducted by static renewal bioassay method on the test fish. The LC₅₀ value of dimethoate to Rasbora daniconius was found out to be 9.136 ppm of the LC50 value was selected for sublethal studies. Behavioural patterns and oxygen consumption were observed in sublethal and lethal concentration of 0 hours to 96 hours. Diemthoate is highly toxic to the animal tested. The treated fish also shows fading of their body colour, like erratic movement, jerky movement, fast swimming surfacing activity, followed hyper excitability, loss of balance, finally settles to the bottom of the test chamber. In the present investigation the oxygen consumption of fish clearly shows that the rate of consumption increases in the control group in throughout the study period at different exposure. In the lethal and sublethal concentration the rates of oxygen consumption is increases in the 48 and 72 hours and suddenly falls down in 72 hours and slightly decrease in 96 hours. Fish under sublethal concentration were found to be under stress but not fatal.

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