Physiology, Behavior, and Survival of Angled and Air-Exposed Largemouth Bass

—Catch-and-release practices are common in recreational fisheries, yet little is known about the behavior, physiology, and ultimate fate of released fish. We used a combination of radiotelemetry (external attachment) and nonlethal blood sampling (i.e., the blood concentrations of lactate and glucose and plasma concentrations of aspartate aminotransferase (AST), Naþ, Kþ, and Cl ) to assess the relationship between the prerelease physiological status and postrelease behavior and mortality of largemouth bass Micropterus salmoides. The experiments were conducted at two temperatures: approximately 158C and 218C. Immediately after capture by standard angling techniques, largemouth bass were exposed to air for 0 to 15 min to assess the consequences of air exposure at two moderate water temperatures. Fish exposed to air for long periods (approximately 10 min or more) had significantly higher concentrations of blood glucose 30 min after air exposure and took significantly longer to regain equilibrium than fish exposed for shorter periods (approximately 3 min or less). The responses of other physiological indicators were inconsistent. Interestingly, at lower water temperatures, males had greater initial concentrations of glucose and AST than females, revealing the importance of sexual differences in the response to angling stress. The fish exposed to air for longer durations tended to exhibit behavioral impairments and remained close to the release site longer than those exposed for short periods. Despite exposure to air for lengthy periods, no postrelease mortality was observed during the 5-d monitoring period. Although the two water temperatures that we used were moderate for this species, a number of sublethal differences (e.g., physiological disturbances and behavioral impairments) were evident in the longer-air-exposure treatment group, highlighting the need to minimize air exposure during catch-and-release angling to maintain the welfare of angled fish. Catch-and-release angling is an increasingly common leisure activity as well as a form of recreational fisheries management throughout the world (Cooke and Cowx 2004; Arlinghaus et al. 2007a). Anglers may release fish either voluntarily or when mandated by harvest regulations with the assumption that the majority of the individuals will survive with negligible long-term consequences. However, much literature suggests that there can be considerable mortality after catch-and-release angling events even though the fish appear to be in good condition at the time of release (reviewed in Muoneke and Childress 1994; Bartholomew and Bohnsack 2005; Arlinghaus et al. 2007b). Recently, a number of studies have been conducted to assess the sublethal physiological consequences of angling-related stress on individual fish, and they have * Corresponding author: [email protected] Received May 2, 2007; accepted January 16, 2008 Published online August 18, 2008 1059 North American Journal of Fisheries Management 28:1059–1068, 2008 Copyright by the American Fisheries Society 2008 DOI: 10.1577/M07-079.1 [Article]