In the future, marine fishes are likely to get squeezed by warming, stratification, deoxygenation at depth, and acidification. Some species may be pre-adapted to habitats that will likely expand in the future, while others may experience a contraction of suitable habitat. We compare the behavior of high trophic level species that have contrasting adaptations to hypoxia, and look at adaptations to their respective habitats. The tunas are 'energy speculators' that require high oxygen environments and have a range of adaptations to high metabolic rate. In contrast, species inhabiting the oxygen minimum layers, such as the bluntnose sixgill shark, have adaptations to energy conservation and low metabolic rate. Future ocean conditions may favor energy conserving adaptations across large regions. Since hypoxia interacts with temperature and pH in its physiological impact, we develop a model to predict performance under a range of present and future scenarios. This model could potentially be used to incorporate the effects of pH into existing ecosystem models that are driven by temperature, oxygen, and productivity.

Kevin Weng is a fish ecologist at the Virginia Institute of Marine Science, College of William & Mary. He studies the migrations of sharks, deepwater fishes, and coral reef fishes. He attended Williams College (BA), the University of Hawaii at Manoa (MSc), and Stanford University (PhD). His lab uses a variety of telemetry techniques to follow animals in the wild to understand the spatial scales at which they live, their habitats, and the nature of their environment.

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