Escalating pesticide deposition in the aquatic environment is becoming a potential threat to aquatic organisms. Present study was designed to investigate acute toxicity in O. niloticus. the fish were exposed to five different concentrations of malathion, chlorpyrifos and lambda-cyhalothrin (synthetic pyrethroid) pesticides in the laboratory using separate aquaria for each chemical. Mortality ranged from 100 to 0%. The 24 h LC50 (median lethal concentration) for O. niloticus was 5.70, 0.5 and 0.015 ppm for malathion, chlorpyrifos and Lambda-cyhalothrin, respectively. LC50 values obtained after 24 h of exposure indicated that the fish were sensitive to all the three tested pesticides. The mortality rate was directly proportional to the pesticides concentration. The results showed that the lambda- cyhalothrin was found more toxic followed by chlorpyrifos and malathion. The study results suggested that the runoff of organophosphates and synthetic pyrethorid pesticides from nearby agricultural fields to aquatic environment posed health hazards on fish.

中文翻译：

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有机磷和合成拟除虫菊酯农药在体内暴露的淡水鱼 Oreochromis niloticus 的急性毒性比较 (Linnaeus, 1758)

水生环境中不断增加的农药沉积正在成为对水生生物的潜在威胁。本研究旨在研究尼罗罗非鱼的急性毒性。在实验室中，鱼暴露于五种不同浓度的马拉硫磷、毒死蜱和高效氯氟氰菊酯（合成拟除虫菊酯）杀虫剂中，每种化学品使用单独的水族箱。死亡率从 100% 到 0% 不等。尼罗罗非鱼的 24 小时 LC50（半数致死浓度）分别为马拉硫磷、毒死蜱和三氯氟氰菊酯的 5.70、0.5 和 0.015 ppm。暴露 24 小时后获得的 LC50 值表明鱼对所有三种测试杀虫剂都敏感。死亡率与农药浓度成正比。结果表明，λ-三氯氟氰菊酯毒性更大，其次是毒死蜱和马拉硫磷。研究结果表明，有机磷酸盐和合成拟除虫菊酯农药从附近农田向水生环境的径流对鱼类的健康造成危害。