Climate, Landscape, Disturbance, and Biotic Factors Associated with the Distribution of Yellowstone Cutthroat Trout: Implications for Conservation Strategies

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 used a 15-km grid sampling approach to establish a spatially-balanced sample of locations of Yellowstone cutthroat trout presence/absence from the current assessment of distribution.  Next, we developed an empirical air temperature-stream temperature model using available data throughout the Greater Yellowstone Ecosystem to predict daily stream temperatures. We then use these data within a hierarchical logistic regression modeling approach to develop a rangewide niche model for Yellowstone cutthroat trout using landscape attributes, natural and anthropogenic disturbance data, stream flow and temperature data, and the distribution of non-native fishes at each site as predictor variables.  Next, we link our model results with projected climate data from regionally-downscaled climate models (15-km² scale) to predict the future distribution of Yellowstone cutthroat trout.  Modeling results indicate the presence/absence of Yellowstone cutthroat trout is strongly associated with temperature, stream flow, anthropogenic disturbance, and non-native distribution patterns. Integrating anticipated changes in climate into our models highlights the need for on-the-ground measures to control non-native species and for developing robust management plans for Yellowstone cutthroat trout throughout the Greater Yellowstone Ecosystem; our results also provide insight into potential gaps in current available data and future monitoring needs.