Climate Change Threats to Fish Habitat Connectivity

Many fish species, including mountain whitefish and bull trout, need a variety of habitat types throughout their different life stages that include appropriate water temperatures, flows, refugia from predators, and adequate food. Key to a fish finding and using these different habitats is the connectivity between them. Changing conditions in the future, including increased air and water temperatures, are expected to impact many fish populations, as well as the rivers, streams, and habitats where they’re found.



This project, jointly funded by the Great Northern Landscape Conservation Cooperative, focused on the Methow River Basin in the arid east-central part of Washington State. The project team used data on fish growth, distribution, movement, food webs, river flow, and water temperature to develop a bioenergetics model and provide a complete picture of the habitat needs for bull trout. It also demonstrated that habitat connectivity is highly important for bull trout. The study showed that mountain whitefish in the Methow River moved up to 185 km from their natal stream areas, similar to the scale documented for bull trout. These large-scale movements are considered extremely important for diversity and resilience to environmental change. Loss of connectivity will be an increasing concern with rising stream temperatures and altered streamflows, and the project suggests that climate change impacts can be expected to affect major aspects of fish life.