Toxicity of natural pyrethrins and five pyrethroids to fish

The toxicity of natural pyrethrins and five pyrethroids was determined with coho salmon (Oncorhynchus kisutch), steelhead trout (Salmo gairdneri), fathead minnow (Pimephales promelas), channel catfish (Icatlurus punctatus), bluegill (Lepomis macrochirus), and yellow perch (Perca flavescens). The 96-hour LC50's in static tests at 12 degrees C ranged from 24.6 to 114 mug/l of natural pyrethrins and from 0.110 to 1,140 mug/l of pyrethroids. Two pyrethroids, RU-11679 and SBP-1382 (R), were over 10 times more toxic than pyrethrum extract in the flow-through tests. Coldwater species of fish were more sensitive than warmwater species to all the compunds. Temperature (12-22 degrees C) influences the toxicity of natural pyrethrin and the pyrethroids. The natural pyrethrin was more toxic to fish in pH 6.5 than in pH 9.5 water, but the toxicity of pyrethroids was not influenced in the pH range. The two most toxic pyrethroids, RU-11679 and SBP-1382, Were deactivated more rapidly in water solutions than natural pyrethrins, S-bioallethrin, dimethrin, and d-trans allethrin.