Evaluating the Effects of Climate on the Distribution of Yellowstone Cutthroat Trout: A Rangewide Analysis

Understanding the factors associated with the current distribution of Yellowstone cutthroat trout is an imperative step in the design and implementation of future conservation and management strategies, particularly given emerging potential stressors associated with regional climate change. Despite substantial interagency effort to develop rangewide status assessments for Yellowstone cutthroat trout, however, these data have not been used to investigate the physical and biological factors that influence the current distribution of the subspecies. To address this need, we developed a stream temperature model for the range of Yellowstone cutthroat trout, and then use this model within a multilevel modeling framework to better understand how landscape attributes, natural and anthropogenic disturbance, and climate are associated with the distribution of Yellowstone cutthroat trout. The results from our modeling suggest the association between climate and Yellowstone cutthroat trout varied considerably across watersheds; in numerous watersheds our results indicate increased temperatures are likely to favor Yellowstone cutthroat trout with longer growing seasons.  In addition to climate, we found disturbance, land use, and land cover as strong predictors influencing the distribution of Yellowstone cutthroat trout.  Our results also illustrate that historical factors (e.g., land use) and non-native species have likely played a larger role in our understanding of the relationship between  Yellowstone cutthroat trout and climate. We place our results in the context of anticipated climate changes in the Greater Yellowstone Ecosystem, particularly in terms of developing future management strategies.  Further our results highlight the importance of considering additional stressors in the near term, which may be more important than future climate change. Overall, our results provide insight into the factors associated with Yellowstone cutthroat trout distribution, highlight potential gaps in currently available data, and can help direct conservation strategies for this native cutthroat trout in the near future.