Jason Dunham

US Geological Survey - Forest and Rangeland Ecosystem Science Center

Abstract: Bull trout is among the most stenothermal of all freshwater fishes in North America, and will certainly face increasing threats if water temperatures warm substantially in the face of climate change. Large areas or “patches” of cold water are necessary to support local breeding populations. Connectivity is also important because bull trout move extensively through stream networks. Connectivity within networks depends not only on the ability of fishes to move freely, but also on the relative locations of important habitats, and their seasonal thermal suitability. Considerably less attention has been focused on the latter in terms of the development of migratory life histories in bull trout. For example, where spawning locations are chronically cold, bull trout may be more likely to adopt a migratory lifestyle to exploit thermal environments more suitable for growth of juveniles and adults. In a fish assemblage context, evidence suggests that bull trout may be more vulnerable to impacts from nonnative species such as brook trout when water temperatures are warmer. Recovery activities to increase the chances that bull trout will persist in the face of climate change can benefit from a realization that thermal requirements of this species are diverse and involve different life stages, locations, and species interactions.

Video Length: 17 Minutes, 58 Seconds

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Bull trout habitat requirements and factors most at risk from climate change