Effect of voltage and exposure time on fish response to electrosedation

Abstract

Chemical sedatives requiring withdrawal (period of time where fish are held posttreatment to allow for tissue drug residues to dissipate) may be impractical for field use. As a result, fisheries professionals are beginning to investigate alternative methods that allow fish to be released immediately after treatment. To address the safety and efficacy of electrosedation as an "immediate-release" sedative approach, induction, recovery times, and blood chemistry of juvenile (211 ± 4 g, 26.1 ± 0.1 cm total length [mean ± SE]) hybrid striped bass (female Morone chrysops × male M. saxatilis) were evaluated after sedation by exposure to 100, 150, or 200 V of pulsed direct current (30 Hz and 25% duty cycle) for 4 or 8 s. All fish were sedated to stage IV sedation within 0.3 min, regardless of voltage strength or exposure time. Recovery times varied significantly by the electrosedation treatment used, but all fish recovered within 2 min postinduction. Changes in blood chemistry were consistent with an acute stress response, but these effects were transient and no differences were observed among the electrosedation treatments. Results suggest that pulsed direct current electrosedation is an effective strategy for quickly and easily sedating juvenile hybrid striped bass and potentially other species of conservation or management concern.