Anaerobic Exercise and Recovery: Roles and Implications for Mortality in Pacific Salmon

Routinely, fish encounter stressors and conditions that require the use of anaerobic exercise, including escaping predators, capturing prey, and interacting with fisheries. Although anaerobic metabolism rapidly yields energy to support locomotion, it also accelerates the depletion of energy stores, and accumulates potentially damaging metabolites, relative to aerobic metabolism. During recovery from intense exercise, animals are vulnerable and may forgo opportunities (e.g., foraging, mating). Recovery is thus likely under strong selection pressure. Despite the fact that recovery is essential for life, relatively little attention has been given to its importance for fitness and survival. Here, the ecology and physiology of recovery following intense exercise are reviewed using Pacific salmon (Oncorhynchus spp.) as a model, though findings are relevant to a wide range of species given that the need for recovery is ubiquitous. Specifically, when and why salmon use anaerobic exercise across their lifecycle, the physiological consequences of this extreme exercise, and the recovery process are considered. The importance of considering recovery for effective management and conservation of Pacific salmon species is discussed, and examples to highlight meaningful ways in which knowledge of recovery can be applied to problems facing fish are provided, with implications widely applicable to all fishes. Given current and projected climate scenarios, understanding the role of temperature in recovery will become progressively more important, and should be an explicit consideration when assessing vulnerability.