Feasibility of Electrosedation As an Alternative to Chemical Sedation of Lake Trout, Salvelinus Namaycush

Electricity has been evaluated as an alternative to chemical sedatives (e.g., tricaine methanesulfonate, carbon dioxide, etc.) in fisheries since the 1970s due to concerns over short and long term effects of chemicals.  We evaluated the sedation effects of direct current, pulsed direct current, and dual-frequency pulsed direct current on Lake Trout. Our primary objective was to determine whether some combination of settings (i.e., duty cycle, frequency, voltage, and waveform) using a Portable Electroanesthesia System (Smith-Root, Inc., Vancouver, Washington) will sedate 100% of Lake Trout for longer than 250 s, but not longer than 600 s, when fish are exposed to electricity for less than 60 s.  We evaluated lethal (i.e., mortality) and sub-lethal (i.e., vertebral column injury) effects. A two-stage approach using direct current followed by pulsed direct current effectively sedated Lake Trout for longer than 250 s and did not cause any mortality within 30 days post-exposure. We suggest that the settings used here may be used for conducting surgeries to implant acoustic transmitters in Lake Trout.