Uptake and Retention of Malathion by the Carp

CIDES are being used extensively in all phases of pest control, these compounds frequently reach the aquatic environment. This occurs most directly through spraying operations for mosquitoes, and indirectly as a result of runoff from treated land areas. Also, these compounds have been suggested for possible use in fish management, for fish eradication (Mulla et al., 1967); and mixtures of two of the phosphates--malathion and naled--have been used as a selective piscicide (Hoff and Westman, 1965). The stated "safety" of these phosphate compounds as opposed to those of hydrocarbon origin has been based upon both acute toxicity' studies and the length of persistence of the parent compound in the environment. Acute toxicity levels of the phosphate insecticides to fish have been shown by Tarzwell (1959) to be considerably lower than those of the hydrocarbons. The variable rate of hydrolysis of the phosphate compounds, however, presents several difficulties in the assumption of rapid breakdown. The purpose of this investigation was to study the uptake and retention of one of these pesticides by the carp, C.•prinus carpio. The compound chosen for investigation was malathion, a phosphorothioate developed by the American Cyanamid Company in 1950.