Characterizing the Thermal Suitability of Instream Habitat for Salmonids: A Cautionary Example from the Rocky Mountains

Abstract

Understanding a species’ thermal niche is becoming increasingly important for management and conservation within the context of global climate change, yet there have been surprisingly few efforts to compare assessments of a species’ thermal niche across methods. To address this uncertainty, we evaluated the differences in model performance and interpretations of a species’ thermal niche when using different measures of stream temperature and surrogates for stream temperature. Specifically, we used a logistic regression modeling framework with three different indicators of stream thermal conditions (elevation, air temperature, and stream temperature) referenced to a common set of Brook Trout Salvelinus fontinalis distribution data from the Boise River basin, Idaho. We hypothesized that stream temperature predictions that were contemporaneous with fish distribution data would have stronger predictive performance than composite measures of stream temperature or any surrogates for stream temperature. Across the different indicators of thermal conditions, the highest measure of accuracy was found for the model based on stream temperature predictions that were contemporaneous with fish distribution data (percent correctly classified = 71%). We found considerable differences in inferences across models, with up to 43% disagreement in the amount of stream habitat that was predicted to be suitable. The differences in performance between models support the growing efforts in many areas to develop accurate stream temperature models for investigations of species’ thermal niches.

Received November 2, 2011; accepted February 15, 2013

ACKNOWLEDGMENTS

Funding for R. Al-Chokhachy was provided in part through the USGS Mendenhall Fellowship Program. S. Wenger was funded by USGS Grant G09AC0050. We thank Kevin Meyer (Idaho Department of Fish and Game), Gwynne Chandler (U.S. Forest Service [USFS]), John Chatel (USFS), and Mike Kellett (USFS) for fish distribution data assistance and A. White (USGS) for GIS assistance. This manuscript was greatly improved by suggestions from three anonymous reviewers. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.