Brown, P. J., and A. V. Zale. 2012. Rotenone persistence model for montane streams. Transactions of the American Fisheries Society 141:560-569.
The efficient and effective use of rotenone is hindered by its unknown persistence in streams. Environmental conditions degrade rotenone, but current label instructions suggest fortifying the chemical along a stream based on linear distance or travel time rather than environmental conditions. Our objective was to develop models that use measurements of environmental conditions to predict rotenone persistence in streams. Detailed measurements of UV radiation, water temperature, dissolved oxygen, total dissolved solids, conductivity, pH, oxidation reduction potential, substrate composition, amount of organic matter, channel slope, and travel time were made along stream segments located between rotenone treatment stations and cages containing bioassay fish in six streams. The amount of fine organic matter, biofilm, sand, gravel, cobble, rubble, small boulders, slope, pH, total dissolved solids, oxidation reduction potential, light reaching the stream, energy dissipated, discharge, and cumulative travel time were each significantly correlated with fish death. Using logistic regression, measurements of environmental conditions were paired with the responses of bioassay fish to develop a model that predicted the persistence of rotenone toxicity in streams. This model was validated using data from two additional stream treatment reaches. Rotenone persistence was conservatively predicted by a model that used travel time, rubble, and oxidation reduction potential. When this model predicts a probability less than 0.95, rotenone applicators can expect incomplete eradication and should plan on fortifying rotenone concentrations. The significance of travel time has been previously identified and is currently used to predict rotenone persistence. However, rubble substrate, which may be associated with degradation by adsorption and volatilization in turbulent environments, was not previously considered.