en Investigation of LC50, NOEC, and LOEC of Oxadiazon, Deltamethrin, and Malathion on Platy Fish (Xiphophorus Maculatus) تخصصي Special پژوهشي Research <b>Background: </b>The presence of pesticides is very prevalent in surface waters of Iran due to their huge consumption for agricultural purpose. These toxic substances may accumulate in the food chain and cause serious ecological and health problems. Chemical pesticides with persistent molecules (long half-life periods) pose a threat to aquatic life forms and the human population consuming the affected fish. <br><b>Methods: </b>Fish samples were exposed to different concentrations of oxadiazon 25% (0, 2, 4, 8, 16 and 32 ppm), deltamethrin 2.5% (0, 0.02, 0.05, 0.10, 0.20, and 0.30 ppm), and malathion 57% (0, 5, 10, 15, 20, and 30 ppm) within a 120 L capacity glass aquaria for 96 h. Their cumulative mortality of platy fish was calculated with a 24-hour interval. <br> <b>Results: </b>LC50-96h was 7.59±0.42, 0.11±0.46, and 12.05±0.75 for oxadiazon, deltamethrin, and malathion, respectively. The very low LC50 obtained for oxadiazon (7.59±0.42 ppm), deltamethrin (0.11±0.46 ppm), and malathion (12.05±0.75 ppm) indicates that oxadiazon, deltamethrin and malathion are highly toxic to platy fish. <br> <b>Conclusion: </b>The results of this study demonstrate that deltamethrin and malathion had the lowest and highest rate of mortality on the platy fish, respectively. Deltamethrin, LC50, Malathion, Oxadiazon, Platy Fish. Deltamethrin, LC50, Malathion, Oxadiazon, Platy Fish. 1271 1276 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-2-183&slc_lang=en&sid=1 Ali Sadeghi علی صادقی sadeghi.a_shilat@yahoo.com 10031947532846004094 10031947532846004094 Yes Department of Fishery, Payame Noor University (PNU), Tehran, Iran Department of Fishery, Payame Noor University (PNU), Tehran, Iran Mohamad Reza Imanpoor محمدرضا ایمان پور 10031947532846004095 10031947532846004095 No Department of Fishery, Gorgan University of Agricultural Science and Natural Resources, Gorgan, Iran. Department of Fishery, Gorgan University of Agricultural Science and Natural Resources, Gorgan, Iran.