Projecting cold-water fish habitat in lakes of the glacial lakes region under changing land use and climate regimes

Cold-water habitat in lakes is projected to decrease under future climate scenarios, and existing trends suggest such declines are already impacting cold-water fish populations. Herein, we predict the effects of future climate and land use change on cold-water fish habitat in the glacial lakes of the upper midwestern US. Ecoregion-specific, regional regression models were developed to predict annual phosphorus loading rates to lakes based on land use and hydrology and coupled to a previously developed fish habitat model. Outputs from one land use change model and three global climate models were then used to project future cold-water habitat. Significant decreases in cold-water habitat quality were projected in all four ecoregions of the study region, with increases in air temperature generally having greater impacts on habitat than land use changes. Projected localized increases in urbanization and corn acreage were found to degrade cold-water habitat for a subset of lakes in all ecoregions. For cisco (Coregonus artedi), the most thermally tolerant of the four species considered, it was found that most of the highest quality (tier 1) refuge lakes will shift to lower quality (tier 2) lakes with adequate habitat, and about half of the tier 2 lakes will shift to tier 3 (non-refuge) lakes with marginal habitat.