Factors Contributing to the Physiological Disturbance in Walleyes during Simulated Live-Release Angling Tournaments

—The goal of the current study was to examine the physiological disturbances in walleyes Sander vitreus that occurred during the different phases of a live-release angling tournament. To achieve this, we took blood and white muscle samples from walleyes during experiments that simulated different aspects of a liverelease tournament (angling, live-well confinement, and weigh-in procedure). In accordance with recent findings for largemouth bass Micropterus salmoides, the physiological disturbance experienced by tournament walleyes results mainly from two distinct bouts of anaerobic metabolism occurring during angling and the weigh-in procedure. These periods are characterized by large increases in white muscle and plasma lactate concentrations, reductions in white muscle ATP, phosphocreatine, and glycogen and a significant cardiac disturbance. The physiological effects of angling are already well understood, but the physiological disturbance that occurs during the weigh-in procedure of tournaments has received little attention. In view of the results from our tournament simulations, a final set of experiments was conducted to examine more closely the bout of anaerobic metabolism experienced by walleyes during the tournament weigh-in. The results of these experiments showed that the magnitude of the physiological disturbance in tournament-caught walleyes is directly related to the duration of air exposure occurring during the weigh-in. Based on these findings, we suggest that to reduce the physiological disturbance experienced by tournamentcaught walleyes, tournament organizers should strive to minimize air exposure during the weigh-in procedure. In recent years, the popularity of competitive angling events has increased dramatically (Schramm et al. 1991; Kerr 1999; Kerr and Kamke 2003). In an effort to conserve the fisheries resource, the vast majority of these events have adopted a live-release policy. In liverelease tournaments, competitors strive to keep captured fish alive until they can be weighed at the end of the tournament day. Following weigh-in, surviving fish are returned as quickly as possible to the water body from which they were angled. During a live-release angling tournament, many factors contribute to physiological disturbances in fish. For example, angling may involve severe exercise, as well as air exposure during hook removal (Payer et al. 1989; Gustaveson et al. 1991; Ferguson and Tufts 1992; Kieffer et al. 1995). To keep fish alive during the angling day, anglers typically retain fish in on-board live wells that are designed to allow fish to recover from angling in fresh lake water. However, fish may be exposed to several stressors while being held in live wells. These include hypoxia (Hartley and Moring 1993), temperature change (Plumb et al. 1988), crowding (Cooke et al. 2002), and accumulation of metabolic wastes (Kwak and Henry 1995). Fish may also experience an additional physiological disturbance during the weigh-in process (Suski et al. 2004). At the * Corresponding author: [email protected] Received June 22, 2005; accepted December 20, 2005 Published online May 9, 2006 557 Transactions of the American Fisheries Society 135:557–569, 2006 Copyright by the American Fisheries Society 2006 DOI: 10.1577/T05-168.1 [Article]