investigation of acute toxicity diazinon, deltamethrin, butachlor and pretilachlor on zebra cichlid (cryptoheros nigrofasciatus)

background: the presence of pesticide due to the huge demand for agricultural purposes is very prevalent in surface waters of iran. these pesticides could finally accumulate in aquatic ecosystems and have been proved to have toxic effects on aquatic animals. the aim of this study was to assess the acute toxicity of diazinon, deltamethrin, butachlor and pretilachlor on zebra cichlid (cryptoheros nigrofasciatus). methods: fish samples were exposed to different concentrations of diazinon (60%) (0, 2, 4, 8, 16 and 32 ppm), deltamethrin (2.5%) (0, 0.02, 0.04, 0.10, 0.20 and 0.40 ppm), butachlor (60%) (0, 2, 4, 8, 16 and 32 ppm) and pretilachlor (50%) (0, 5, 10, 20, 30 and 40 ppm) for 96 h within the 100 l glass aquaria and cumulative mortality of zebra cichlid fish was calculated in 24-h interval. results: the very low lc50 obtained for diazinon (5.06±0.37 ppm), deltamethrin (0.15±0.39 ppm), butachlor (8.93±0.26 ppm) and pretilachlor (20.72±0.58 ppm) indicated that these are highly toxic chemicals. conclusion: our results demonstrate that deltamethrin and pretilachlor had the lowest and highest rate of mortality on the zebra cichlid respectively.