Like many fish species across the western U.S, Rio Grande cutthroat trout (RGCT) in southern Colorado and central New Mexico are increasingly threatened by climate change impacts (drought, changes in water temperatures and streamflow patterns) and the encroachment of non-native fish species (increased competition for resources). These two factors are the leading cause of habitat loss and population decline for RGCT which makes addressing them a top priority for local resource managers.  

With support from the National and South Central CASCs, USGS scientists Abigail Lynch, Colleen Caldwell, and their collaborators are working with managers and researchers from local universities and state agencies to address the current lack of data on RGCT’s ability to adapt to increasing stream temperatures and drought conditions, and to explore strategies for possibly limiting the invasion of non-native fish species.

Thus far, researchers have found that RGCT have a lower-than-expected tolerance of warmer water temperatures than their non-native counterparts. This disadvantage may mean that RGCT won’t be able to persist in a changing climate. However, the team’s projections of future RGCT populations indicate that non-native fish pose the greatest threat to RGCT if no intervention is taken. By implementing ‘fish barriers’ to aid in the separation of native and non-native fish, they estimate the probability of RGCT survival could increase eight-fold.  

The research team created a new geonarrative summarizing this research and the impacts of climate change and non-native species to inform management strategies for RGCT in New Mexico and Colorado.