Range-wide climate vulnerability assessment for threatened bull trout
Jason Dunham, Supervisory Aquatic Ecologist, U.S. Geological Survey
Image Credit: Joel Sartore/National Geographic Stock with Wade Fredenberg
The threatened bull trout (Salvelinus confluentus
) depends more on cold water than any other species of salmon or trout in the Northwest. Bull trout can also be sensitive to floods that disturb eggs and fry that incubate in stream gravel nests over the winter. Climate warming is likely to spell trouble for bull trout if it leads to warming of stream temperatures and more rain and flooding during the winter. We also know that bull trout are threatened by existing human land and water uses, as well as non-native trout species that can compete with and sometimes interbreed with them. The challenge in this study is to address these different threats across the vast area where bull trout live in the Northwest, including Oregon, Washington, Idaho, Nevada, and Montana. To this end we are mapping the habitats where bull trout live, and measuring the importance different threats across the species’ range in the Northwest. The results of this work will allow us to better understand where different threats are operating to influence bull trout and help to identify appropriate conservation actions to ensure the bull trout can persist in the face of climate change.