Toxicity of mosquito larvicidal pyrethroids to four species of freshwater fishes

Predatory and food fish species commonly used for the control of mosquito larvae and chironomid midges were exposed to new synthetic pyrethroids having mosquito larvicidal potential to determine their toxicity. While different species showed different levels of susceptibility to the pyrethroids, most of the Chemicals had a good margin of safety as measured by the concentrations at which 50 and 90% of a fish sample died. Pyrethroids having high margins of safety can probably be used as larvicides without severe acute effects on fish. Those Chemicals having low margins of safety will probably represent a hazard to exposed fish.