Rotenone Persistence Model for Montane Streams

Abstract

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 ultraviolet radiation, water temperature, dissolved oxygen, total dissolved solids (TDS), conductivity, pH, oxidation–reduction potential (ORP), 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, TDS, ORP, light reaching the stream, energy dissipated, discharge, and cumulative travel time were each significantly correlated with fish death. By 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 with data from two additional stream treatment reaches. Rotenone persistence was predicted by a model that used travel time, rubble, and ORP. When this model predicts a probability of less than 0.95, those who apply rotenone 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 the degradation of rotenone by adsorption and volatilization in turbulent environments, was not previously considered.

Received March 12, 2011; accepted October 11, 2011

ACKNOWLEDGMENTS

Access to study sites was provided by Hilda Sexauer, Carter Kruse, Scott Barndt, Pat Clancy, Jim Dunnigan, Matt Boyer, and Dave Moser. Field assistance was provided by John Olsen, Jessica Stewart, Troy Buckle, Heather Johnson, Jennifer Ard, Patrick Odenbeck, John Stites, Melinda Brown, and Michael Meeuwig. Carter Kruse, Tom McMahon, Bob Gresswell, Don Skaar, and an anonymous reviewer provided valuable comments on earlier versions of this manuscript. Mention of trade names is for information purposes only and does not imply endorsement by the U.S. Government.