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

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