Toxicity and LC 50 96-h of Malathion on the Caspian common carp fingerlings, Cyprinuscarpio, and its effects on some blood indices, including hematocrit, glucose, cholesterol and total protein content, were investigated. The median lethal concentration, the lowest effective concentration and the maximum allowable concentration were found to be 1.3, 0.646 and 0.13 mg.L-1 , respectively. Based on the LC 50 finding, Malathion can be regarded as "moderately toxic" for this fish. Significant

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... ces between the hematocrit, glucose, and cholesterol among treatments were evident, but no significant difference in the total protein of blood plasma was observed. The hematocrit level in the control group was lower than the other groups. The lowest levels of cholesterol and glucose were observed in 0.5 mg/L, and the maximum levels were found in 2.5 and 2 mg/L, respectively. Therefore, malathion which is supposed to be ineffective for non-target species at allowable concentrations, can lead to their blood indicies responses and bio-damages.