Multiple Climate Change Challenges For Native Cutthroat Trout Discussed in National Geographic Article

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NOROCK scientist Clint Muhlfeld discussed the direct and indirect effects of climate change on native cutthroat trout in western Montana in a National Geographic article. Specifically, Clint spoke about the effects of altered streamflows and hybridizing with a nonnative fish species.

Close-up of non-hybridized westslope cutthroat trout in Montana

Close-up of non-hybridized westslope cutthroat trout Oncorhynchus clarki lewisi) from the Flathead Basin in Montana. This fish represents the genetic and life history diversity of western trout by surviving extreme climatic variation over millions of years. (Credit: Jonny Armstrong. Public domain.)

Aquatic ecologist Clint Muhlfeld is featured in a recently published National Geographic story titled “Climate change comes for a favorite summer pastime: fishing.” The article follows the narrative of a fly-fishing guide based in western Montana as she discusses the challenges of fishing within the context of contemporary climate change. The article brings in the expertise of a handful of scientists, but Clint’s research is discussed at length. Specifically, he talks about his research on native cutthroat trout in the northern Rockies to assess the direct and indirect affects of climate change on native fish. In the article, Clint discusses the direct influences of climate change like warming water temperatures and shifting streamflow regimes, and the hidden, indirect effects of hybridizing with invasive species. In the case of cutthroat trout in the northern Rockies, they are hybridizing with rainbow trout, a highly invasive species.

The findings of Clint and his collaborators have indicated that hybridization between rainbow trout and cutthroat trout expands during periods of high stream temperatures and low streamflow brought on by low precipitation. This is likely due to diminished springflows during drought periods failing to wash away rainbow trout eggs from spawning nests or washing newly emerged juveniles away, allowing rainbow trout populations to increase and reproduce with native cutthroat trout. To make matters worse, rainbow-cutthroat trout hybrids have much lower fitness (decreased reproductive success) compared to pure cutthroat trout. That may translate into cutthroat trout genetics not only being diluted by rainbow trout genetics, but their resulting populations of hybrid fish may not be as adapted to their environment as the genetically pure cutthroat trout.

Clint and his collaborators, including fellow NOROCK scientist Robert Al-Chokhachy, are continuing to investigate the complex ways climate change can affect native trout. His research can assist managers in their understanding of the challenges facing native fish in the context of climate change and provide them the knowledge needed to develop appropriate management strategies for cutthroat trout and possibly other native fish species in west.

This research is part of a national USGS effort to better understand the effects of climate change and drought on freshwater biodiversity and ecosystems, and has been funded by the USGS Ecosystems Mission Area, National Climate Adaption Science Center, and the Northwest Climate Adaption Science Center.

To learn more about this research, check out the Publications and News tabs below.

Creek in western Montana

Clint’s research team on a tributary of North Fork Flathead River studying cutthroat trout. (Credit: Joe Giersch, USGS. Public domain.)

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Date published: April 4, 2017

Hybridization between Native and Invasive Trout is Increasing in the West

Hybridization, or the interbreeding of species, is increasing between native and invasive trout across the northern Rocky Mountains, according to a study released Tuesday by the U.S. Geological Survey and partners.