Abstract
Atlantic tarpon (Megalops atlanticus) are prized sportfish found through the Gulf of Mexico/America. Atlantic tarpon populations are also considered vulnerable to extinction, and thus many of the recreational fisheries targeting Atlantic tarpon in North America are limited to catch-and-release (CAR). While CAR procedures are common and effective means of protecting recreational sportfish species, it is important to recognize that species-specific traits can impact their efficacy. Here, we sought to explore the importance of Atlantic tarpon air-breathing behaviour in the context of recovery from exercise, which may impact their vulnerability to CAR angling events. A first series of experiments demonstrated that Atlantic tarpon increased air breathing rate following exposure to hypoxia-reinforcing their status as a facultative air-breather-but not following exhaustive exercise. A second series of experiments assessed whether the recovery of biochemical indicators of exhaustive exercise stress in the white muscle and plasma would be impacted by restricted air access during recovery. For fish with access to air, normal patterns of exhaustive exercise were noted in the plasma and white muscle with the exception that haematological parameters were unaffected by exercise. Access to air resulted in no significant differences in recovery profiles at the 1-h time point. Interestingly, exercise resulted in a significant and sustained reduction in red blood cell pH, which coincided with a significant impairment in oxygen binding affinity at higher oxygen partial pressures, possibly explaining why air-breathing behaviour is not beneficial during exercise recovery. Overall, these data suggest that Atlantic tarpon conform to typical patterns of exercise recovery in fishes and that no special consideration are required with respect to CAR angling.