Using a Spatially Explicit Approach to Examine Bull Trout Spawning Habitat Use

More recently, focus on fish-stream habitat relations has moved from site specific to more spatially expansive riverscape investigations.  In this study, I investigated relationships between stream habitat and bull trout spawning areas at multiple spatial scales using spatially continuous surveys.  The main objective was to test whether habitat used by bull trout for spawning differs from habitat not used. Patterns of aquatic habitat, stream temperature, and bull trout redd distributions were quantified for nearly all available habitat in two spawning streams (8.2 km, 199 redds and 8.8 km, 181 redds).  In addition to examining habitat-redd distribution patterns using typical graphing procedures, all data from these surveys were georeferenced and visualized in a GIS to examine these patterns across the riverscape.  At the channel unit and reach scales, bull trout used stream habitat with more hiding cover and areas of gravel accumulation than areas not used.  Although stream temperatures were well within thermal requirements for bull trout, spawning areas appear to be associated with habitats influenced by cooler water inputs which support observations from other basins.