greater threat to freshwater organisms. Objectives: To measure the tolerance limit of Labeo rohita to expired permethrin, malathion, and dichlorovos mixture at different concentrations. Methods: Freshwater fingerlings of L. rohita were exposed to sub-lethal (0.3mg/l) and lethal (2.3mg/l) concentrations of permethrin, malathion, and dichlorovos mixture, with three replications under constant water temperature (16-30°C), total water hardness (225mgL-1) and pH (6.8-7.7) for 96-hr. Probit analysis was used to calculate the Lethal concentration (LC50) and (LC100) of 96-hour exposure of the pesticide mixture for fish. Correlation analyses were conducted to identify relationships between the variables under study. Physicochemical parameters of water (Electrical conductivity (EC), Dissolved oxygen (DO), Oxidation-reduction potential (ORP), and Salinity) were recorded on a 12-hr basis. Results: For 96 hours, the mean values of LC50 and LC100 of L. rohita were calculated as 1.53 ± 0.028 and 3.05 ± 0.083 mgL-1, respectively. L. rohita exhibited behavioural changes such as erratic swimming, loss of equilibrium, heavy breathing, and abnormal posture due to the toxic effects of the pesticide mixture. Correlation analysis indicates that increasing concentrations of permethrin, malathion, and dichlorvos pesticides significantly degrade water quality, reducing DO while increasing ORP, salinity, and EC. Conclusions: It was concluded that an expired pesticide mixture is more lethal to aquatic life than an unexpired pesticide mixture. So, it is important to take precautionary measures before discarding expired pesticides in aquatic ecosystems.
Aslam et al. (Tue,) studied this question.