Toxicity of Seven Different Insecticides to Rainbow Trout Salmo Gairdnerii (Richardson)

Today, with the development and use of an increasing number of more potent insecticides there exists a real and potential danger to many forms of wildlife. DDT was the first of these insecticides to be used and it is still very popular and widely applied. Its widespread use on agricultural lands, forests, marshes, and water quickly aroused the interest of persons and agencies who were concerned with the ways in which it might directly or indirectly affect animals other than insects. Most of the studies have been concerned with the toxicity of DDT, but within recent years a number of new insecticides have been developed which are more toxic to animals than DDT. Since little information is available concerning the toxicity of these insecticides to fish it seemed expedient to experimentally test the relative toxicity of several of these newer insecticides in comparison to DDT. This study was made to determine the relative toxicity of dieldrin, toxaphene, heptachlor, aldrin, methoxychlor, chlordane, and DDT to fingerling rainbow trout, Salmo gairdnerii (Richardson). Small fingerling trout were chosen for experimental purposes because they are most easily maintained under laboratory conditions and because smaller fishes are affected to a greater extent by insecticides than are larger fishes (Hoffman and Surber, 1945; Stock, 1950; Surber and Hoffman, 1949). The problem not only involved a study of the relative toxicity of these seven insecticides, but also a study of the tolerance of trout to different formulations and concentrations of each insecticide. Since these insecticides are generally applied in the form of emulsifiable concentrates, wettable powders, and dusts, these were the formulations tested. Although all three types of formulations were not available for each insecticide, at least two formulations were tested for each