Influence of Temperature and Water Quality on Physiological and Behavioral Responses of Walleye at Catch and Release Angling Tournaments

Abstract

Walleye (Sander vitreus) is one of the most sought after freshwater fish for recreational angling in Canada. Physiological and behavioral measures of stress were used to determine if reduced live-well temperatures and improved water conditions can mitigate stress and facilitate recovery during catch and release angling tournaments. Fish were collected at tournament weigh-in stations to evaluate the effects of live-well water quality parameters and stress mitigation methods on recovery. Fish condition was assessed by measuring plasma cortisol and lactate levels, and observing behavioral cues. This study observed body flex, tail grab, and swim scores and these were determined valuable predictors of stress for Walleye. A commercially available live-well treatment reduced build-up of nitrogenous waste in live wells not replenished with lake water, which is useful while maintaining live-well water quality. High temperature, nitrogenous waste content, and poor weather conditions contributed to higher plasma cortisol and lactate levels, whereas higher temperatures contributed to lower blood glucose levels. Thus it may be best to avoid holding tournaments during the warm summer months or when high winds are forecasted. Additionally, this study shows water quality parameters are an important aspect of the live-well holding periods and tournament organizers should mandate mandatory conditions for live-wells to include continuous aeration and either continuous circulation or the use of live-well treatments depending on season; for instance live-well treatments and temperature control may be preferential over continuous circulation in warm conditions.