Population-Scale Resilience of Spring Chinook (Oncorhychus tshawytscha) to Wildfire in the Wenatchee River Watershed

Wildfire is an important agent of change contributing to a mosaic of dynamic habitat conditions in riverscapes across the western United States. For native aquatic species such as Pacific salmon, dynamic landscape processes, such as wildfire, have led to phenotypic variability resulting in population-scale resilience. Anthropogenic land management practices of the past century including wildfire suppression, and riparian zone alterations have conspired to change available in-stream habitat. How well native fish respond to natural disturbance, such as fire, in currently altered landscapes is an important question for landscape managers. We explored current and post-fire population-scale viability of spring Chinook salmon (Oncorhynchus tshawytscha) in the Wenatchee River basin, Washington, at reach and subwatershed scales. Our post-fire models include novel modeling techniques that capture changes in sediment, wood, and temperature. We modeled three stages of the spring Chinook life cycle: egg, juvenile, and spawning adult. This allowed us to differentiate the portion of the life cycle that had the greatest potential for fire affects. We found negative effects of fire in all life stages with adults most affected by wildfire. Reach-scale specificity allowed us to identify the areas where wildfire suppression has the greatest potential to effect population-scale resilience of spring Chinook.