Understanding Climate Impacts on Native and Invasive Fish for Conservation, Management, and Economic Goals in the Northern Rockies

As the origin of three major basins that drain the Columbia, Missouri, and Saskatchewan rivers, Montana is the hydrologic apex for North America. The Northern Rocky Mountain region is home to some of the last remaining interconnected habitats for many native fishes, including the threatened bull trout and native westslope cutthroat trout. The Northern Rockies are also experiencing rapidly changing climate conditions, with temperatures rising at twice the global average. These changes are having a range of impacts on aquatic ecosystems, including warming stream temperatures and changing streamflow regimes. This region is also experiencing a rise in the expansion of alien invasive fish species, which further threaten ecologically and economically valuable cold-water fish like trout and char.

 

The expansion of invasive species directly threatens regional economies, including Montana’s recreational fishing industry, which brings an estimated $1 billion to the state’s economy each year. Despite the implications of these shifts in fish communities, our understanding of how changes in climate might be facilitating the expansion of invasive species is limited, thereby restricting proactive resource management. So far, such expansion has led to observable differences in the productivity and biodiversity of fisheries across the Northern Rocky Mountains. Fisheries managers are increasingly aware of this problem and are faced with the difficult task of weighing trade-offs between preserving cold-water fisheries, and thereby aiding the conservation of native species, or shifting to recreational or warm-water fisheries, which are often comprised of non-native fish that can harm surrounding ecosystems but may also maintain the region’s prized fishing industry.

 

The ultimate goal of this project is to assess the impacts of climate change on native and invasive fishes, fish communities, and user groups to help managers, anglers, and local governments anticipate the ecological and economic consequences of observable climatic changes in the Northern Rocky Mountains. Researchers will use long-term Montana fisheries data in conjunction with occupancy models to describe the geographic and seasonal expansion of invasive fishes throughout the region. This ability to use long-term data is a major strength of the project and was supported by collaborative, decades-old partnerships between the U.S. Geological Survey, Montana Fish, Wildlife and Parks, National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, the University of Montana, and Trout Unlimited. Researchers will engage with these and other stakeholders throughout the study to enhance fisheries conservation and management in the region.