Studies on acute toxicity of synthetic pyrethroid -cyhalothrin on freshwater fish Labeo rohita

Aim : To study the acute toxicity of λ-cyhalothrin in freshwater fish Labeo rohita by determining the 96 hours lethal concentration 50 (96 hrs LC ) and behavioural patterns of exposed fish. 50 Materials and Methods: A total 270 fingerling size fish were used to determine the 96 hours lethal concentration 50 (96 hrs LC ) of λ-cyhalothrin as per the guideline of Organization for Economic Co-operation and Development (OECD) 203 except 50 the loading density which was higher than the recommended density 1.0 g/l to reduce the chemical loss. The fingerlings were brought from the local fish hatchery, disinfected and acclimatized for 14 days in laboratory conditions. 60 fingerlings, 10 each were divided into six plastic tubs of 35 L capacity with 0 ug/L (control), 10 ug/L ethanol only (vehicle control), 0.1 ug/L, 1ug/L, 5 ug/L and 10 ug/L of λ-cyhalothrin in 20L of dechlorinated tap water. Static renewable bioassay was conducted using five selected doses in between concentrations causing 10 to 100% mortality i.e. 2 ug/L, 2.5 ug/L, 3 ug/L, 3.5 ug/L and 4 ug/L along with control and 4.0 ug/L of acetone only as vehicle control. Water quality parameters like temperature, pH, total hardness and total alkalinity were measured daily. The experiment was repeated three times. Behavioural pattern and mortality was recorded periodically. Results: The fish exposed to chemical showed erratic swimming, loss of balance, surfacing and convulsions in a dose dependent manner. 2.72 ug/L was calculated as 96 hrs LC value for λ-cyhalothrin in Labeo rohita. 50 Conclusions: λ-cyhalothrin was reported as highly toxic chemical for Labeo rohita producing altered behavioural pattern in dose dependent manner.