Behavioral and physiological responses of the congeneric largemouth ( Micropterus salmoides) and smallmouth bass ( M. dolomieu) to various exercise and air exposure durations

Abstract

Two of the major stressors associated with the catch-and-release of recreationally angled fish are exercise and air exposure. This study investigated the combined effects of exercise and air exposure duration on the congeneric largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu, two of the most popular sportfish in North America. We simulated angling by exercising the fish (i.e., chasing by hand) for either 20 or 180 s and then immediately exposed fish to air for random durations ranging from 0 to 10 min. To assess the combined effects of increased exercise and air exposure durations, and the time needed to recover, we monitored several behavioral responses for both species. For largemouth bass, we also measured hematological variables (i.e., lactate, glucose, and hematocrit). Never did exercise and air exposure have a significant effect on the same response measured in the same species, suggesting that there are two separate responses occurring: likely an exercise response and a stress response associated with hypoxia. Our results also indicate that largemouth bass recover from combined exercise and air exposure faster than smallmouth bass. Smallmouth bass took longer to regain equilibrium, to stop leaning, and to return to very shallow (i.e., normal) ventilation depth, as a result of the treatments of exercise and air exposure, than the largemouth bass. This is likely due in part to behavioral and habitat differences between the two species as well as their different aerobic capacities and sensitivities to hypoxia. Interestingly, no mortality was observed despite air exposure durations of up to 10 min. It is still unclear how air exposure interacts with environmental stressors, such as water temperature. We conclude, based on these findings and as suggested from other studies, that air exposure is a significant stressor, and that species-specific guidelines are needed for catch-and-release practices to be most effective, and to best insure the sustainability of fisheries.