Saeid Shahbazi - Fisheries Dept., Faculty of Natural Resources, University of Tehran, Karaj, Iran
Hadi Poorbagher - Fisheries Dept., Faculty of Natural Resources, University of Tehran, Karaj, Iran
Hamed Ghafari Farsani - Fisheries Dept., Faculty of Natural Resources, University of Tehran, Karaj, Iran
Amin Khazaei - Fisheries Dept., Faculty of Natural Resources, University of Tehran, Karaj, Iran
Elahe Chaharde Baladehi - Fisheries Dept., Faculty of Natural Resources, University of Gorgan, Golestan, Iran

Pesticides are used in agriculture to control pest and also protect the human healthand animals. Excessive use of pesticides put human health at risk and threaten nontargetorganisms, polluting water, soil and air are. Malathion is a component oforganophosphate pesticide which is used as a fungicide in agricultural fields. At thepresent study, lethal concentration (LC 50) of malathion was calculated for Rutilusfrisii kutum with a mean weight of 3 ± 1 [mean ± SD] g. The experiment were carriedout in static condition and based on instructions of O.E.C.D in 4 days under controlledwater physicochemical factors with pH = 7–8.5, DH = 215 mg L-1 (CaCO3) andtemperature = 24 ± 1 °C. Primary experiments were performed to find the mortalityrange of the specimens by introducing 10 fish in 25 L glass aquarium with continuousaeration. After finding the mortality range, the final experiments were carried out ina completely random trial with six concentration treatments of malathion (0, 0.5, 1,3, 5 and 10 mg L-1) with three replications. Data were analysed using the probitanalysis. LC1, LC 10, LC30, LC50, LC70, LC90 and LC99 were calculated in 24, 48, 72and 96 hours. Our results indicated that LC50R96-h for Rutilus frisii kutum is 0.86 mgL-1 . These findings suggest that malathion has a high toxicity for Rutilus frisii Kutum.In this study, the hematocrit decreased significantly with increasing concentrationsof the malathion with the concentrations of 0.2, 0.3 and 0.5 mg L-1 being significantlydifferent from the controls. Clinical symptoms including irregular protrusion of theeyes and irregular swimming were observed.

Organophosphore, Malathion, Rutilus frisii kutum, LCP50P 96 h, Pollution