Intraspecific Variation in Metabolic Responses of a Cool Water Fish to Increasing Temperatures

Abstract

Growing impacts of climate change necessitate predicting species' vulnerability to altered ecosystems. Assessing vulnerability requires understanding how species' physiology, life history, and ecology vary among populations and can be altered by behavioral, plastic, and evolutionary adaptations. To examine intraspecific variation in sensitivity to climate change, we measured metabolic responses to acute and chronic temperature exposures in three rearing pond populations of walleye (Sander vitreus), a cool-water-adapted fish species threatened by climate change. We show significant differences among rearing pond populations in response to increasing temperatures which may originate from broodstock, developmental plasticity, and acclimation. Our results indicate northern walleye may be more tolerant of acute and chronic exposure to higher temperatures by being able to maintain a higher aerobic scope than more southern populations. Furthermore, even over small geographic distances, populations can have significantly different physiological responses to environmental stressors. Quantifying variation in population-specific metabolic responses can inform predictions of growth, reproduction, and fitness across a species range and clarify the importance of within-species diversity in determining vulnerability to environmental stressors.