Consequences of winter air exposure on walleye (Sander vitreus) physiology and impairment following a simulated ice-angling event

Abstract

Length-based harvest restriction is common in fisheries management and can result in a substantial number of fish being released after capture. Science on live release confirms that the practice allows individuals to return to the population and reproduce; however, little is known about how handling practices influence mortality or the sub-lethal physiological alterations in fish that are released during the winter. In this study, walleye (Sander vitreus; Mitchill 1818) were angled through the ice in Lake Nipissing, Ontario to evaluate the contribution of air exposure to the reflex impairment, post-release mortality, and the stress response of fish in the winter. Following 24 h holding, fish were exposed to a simulated angling event and exposed to air or snow across a range of exposure durations. Fish were non-lethally blood sampled and were assessed for reflex impairment and mortality 24 h after capture. No mortalities were recorded during the study and reflex impairment was not linked to exposure type or duration. Blood [lactate] at 1 h post-capture was comparable across treatment groups but was significantly higher than respective baselines. Plasma [cortisol], blood [glucose], and aspartate aminotransferase activities were comparable to baseline levels. Walleye appeared to be resilient to catch-and-release angling in the winter given that no mortalities occurred and fish suffered minimal reflex impairment and physiological disturbance following capture. Findings from this study suggest that mandatory catch-and-release regulations for sub-adult walleye are a useful tool for the management of winter walleye ice fisheries.