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), Na +, K + , 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 15°C and 21°C. 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.