Evaluation of Two Forms of Electroanesthesia and Carbon Dioxide for Short-Term Anesthesia in Walleye

Abstract

Anesthetics immobilize fish, reducing physical damage and stress during aquaculture practices, stock assessment, and experimental procedures. Currently, only tricaine methanesulfonate (MS-222) is approved for use as an anesthetic for food fish in Canada and the United States; however, MS-222 can only be used with certain fish species, and treated fish must be held for a specified period of time before release into the wild. Two forms of electroanesthesia and carbon dioxide (CO₂) were evaluated as anesthetics for adult walleye Sander vitreus to determine their suitability for use before intracoelomic implantation of telemetry transmitters. Walleyes were subjected to one of three treatment groups: constant direct current (CDC), pulsed direct current (PDC), and CO₂. Fish subjected to these treatments were monitored for induction (where appropriate) and recovery time and whether these forms of anesthesia were conducive to implanting telemetry transmitters, that is, whether they fit a surgery threshold range of 250–350 s. Additionally, all fish were monitored for posttrial survival, and radiographs were taken to determine whether any vertebral damage was associated with the electroanesthesia treatments. Although all anesthetic treatments successfully immobilized fish for enough time to implant a transmitter, PDC electroanesthesia is recommended because of its immediate induction time, quick recovery, high immediate and short-term survival, and lack of evidence of vertebral abnormalities.

Received January 11, 2011; accepted May 24, 2011

ACKNOWLEDGMENTS

The authors are grateful to T. Hartman, E. Weimer, M. Turner, J. Tyson, and J. Ross at the Sandusky Fisheries Research Station, Ohio Department of Natural Resources, Division of Wildlife, for their assistance collecting fish and conducting the anesthesia trials. We are also thankful for the assistance of C. Goings, of the Inland Fisheries Research Unit, Ohio Department of Natural Resources, Division of Wildlife, for fabricating the electronarcosis unit as well assisting with preliminary trials and for D. Liebig for viewing the videotape footage and recording the induction and recovery times. T. Brenden at the Quantitative Fisheries Center, Michigan State University, provided statistical consultation. We are also grateful to M. Faisal for coordinating the radiographs through the College of Veterinary Medicine at Michigan State University and to N. Nelson and J. Brown for reading and scoring the radiographs. This research was funded by Federal Aid in Sport Fish Restoration Project F-69-P, the Great Lakes Fishery Commission, and the Great Lakes Research Initiative.