Bull Trout (Salvelinus confluentus), a cold-water species native to the Pacific Northwest, face significant threats from habitat degradation, climate change, and the introduction of non-native Brook Trout (Salvelinus fontinalis). Brook Trout compete directly with Bull Trout for resources, exhibit more aggressive feeding behaviors, and hybridize with Bull Trout, reducing genetic fitness and threatening population persistence. Climate change further amplifies these challenges by altering thermal regimes in critical habitats, potentially exacerbating Brook Trout’s competitive advantages.
At Mount Rainier National Park (MRNP), 32 miles of glacial-fed streams support designated critical Bull Trout habitat, providing a climate refuge for cold-water species. However, electrofishing and spawning surveys confirm the presence of Brook Trout within park boundaries, including key Bull Trout habitats. While thermal preferences of Bull Trout and Brook Trout have been studied in non-glacial rivers, little is known about their interactions in glacial headwaters where cold-water habitats are rapidly changing.
This study addresses this knowledge gap by defining the thermal preferences of both species in glacial headwaters of the Puyallup watershed using environmental DNA (eDNA) sampling and a Spatial Stream Network Model (SSNM). Results will inform conservation strategies to mitigate Brook Trout threats and protect vulnerable Bull Trout populations in the face of ongoing climate change.