Effect of temperature on the chronic toxicity of hydrothol-191 to the fathead minnow (Pimephales promelas)

The weedkiller Hydrothol-191, the alkylamine salt of endothall was effective against algae and aquatic macrophytes at lower concentrations and for longer periods than other commercial formulations of endothall. As part of a study on the chronic toxicity of Hydrothol to non-target organisms, the effect of temperature on its toxicity to fish (Pimephales promelas) was investigated. The chronic toxicity values for survival and growth of minnow larvae at 15C and 25C are tabulated; these values were 2 (at 15C) and 6 (at 25C) times lower than acute toxicity values.