Effectiveness of Two Commercial Rotenone Formulations in the Eradication of Virile Crayfish Orconectes virilis

Abstract

The virile or northern crayfish Orconectes virilis is an invasive species throughout much of the USA, damaging aquatic communities where it is introduced. Therefore, identification of effective methods for its eradication from areas in which it is unwanted is important. We studied the effectiveness of two commercial formulations of rotenone, Chem Fish Regular and CFT Legumine, for virile crayfish control. Although both formulations were effective for fish eradication, earlier observations by fisheries managers suggested that the relative effectiveness of the two formulations differs for crayfish. The only noteworthy difference between the formulations is that the former contains a synergist. In our first experiment, we tested each toxicant at the maximum labeled dosage (5 ppm) and found CFT Legumine to be 100% ineffective (0% mortality), while the Chem Fish Regular treatment resulted in 12.5% mortality. After we deemed Chem Fish Regular to be the only toxicant with any effectiveness against virile crayfish, we tested concentrations from 5 to 50 ppm and found 10 times the maximum labeled dosage (50 ppm rotenone) was needed to kill all virile crayfish. Because crayfish burrow and can leave water, and because 100% eradication is usually desired, rotenone applied at the labeled rates will not be effective for crayfish control. However, treating a body of water with CFT Legumine to eradicate invasive fish while leaving desirable crayfish unharmed is possible.

Received May 16, 2014; accepted February 4, 2015

ACKNOWLEDGMENTS

This project was conducted with aquatic animal care and use in accordance with procedures at the University of Arizona. Funding and support for this study were provided by the Arizona Department of Game and Fish. We especially thank Jeff Sorensen, Arizona Game and Fish Department, for providing inspiration for this study and supplying us with crayfish traps and chemicals to make this study possible. We thank the staff at University of Arizona Environmental Research Laboratory, including Galen Bennett and Jeff Bliznick, for helping with maintenance of the laboratory facilities. We thank Olin Feurbacher for his assistance at the laboratory as well as Anita Kelly, University of Arkansas at Pine Bluff, for her contribution to the discussion. Reference to trade names does not imply endorsement by the U.S. Government.