Physiological Effects of Potassium Chloride, Formalin, and Handling Stress on Bonytail

Abstract

We characterized the sublethal physiological changes in bonytail Gila elegans subjected to consecutive 750-mg/L potassium chloride (KCl) and 25-mg/L formalin treatments for the removal of zebra mussel Dreissena polymorpha and quagga mussel D. bugensis veligers. Plasma cortisol, glucose, and osmolality were measured over 24 h and at 14 d posthandling after exposing bonytail to KCl and one net stressor (capture with a net), KCl plus formalin and two net stressors, and one or two net stressors without chemicals. Elevated plasma cortisol (322–440 ng/mL) and glucose (254–399 mg/dL) concentrations were observed in all treatments compared with the concentrations in control fish (plasma cortisol, 56 ng/mL; glucose, 43 mg/dL). While there were no detectable differences in plasma osmolality among the treatment and control fish, a difference was observed between fish that were handled once versus twice. Chemical effects of stress were not observed in any of the physiological responses when the KCl treatment was compared with the one-net stressor treatment or when the KCl plus formalin treatment was compared with the two-net stressor treatment. Cumulative responses, however, were observed between one net stressor and two net stressors for plasma glucose and osmolality but not for plasma cortisol. Plasma cortisol and glucose levels remained elevated at 24 h posthandling, indicating that bonytail had not completely recovered from the handling stressors and would benefit from a recovery period in protected refugia before being released.

Received August 23, 2010; accepted January 20, 2011

ACKNOWLEDGMENTS

Funding for this research was provided by the U.S. Fish and Wildlife Service, Dexter National Fish Hatchery and Technology Center. Additional support was provided by U.S. Geological Survey, Cooperative Research Units and New Mexico State University, Agricultural Experiment Station. The authors are grateful to Manuel Ulibarri, William Knight, Jason Nachtmann, Bill Williams, Renee Martin, and Michael Shoemaker for their tireless help throughout the project. We also thank Wade Wilson and Connie Keeler-Foster for invaluable comments during the preparation of this manuscript. The work was conducted under the U.S. Fish and Wildlife Service Federal Endangered Species permit number TE676811–2. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Government.