Evaluating the genetic population structure and movement patterns of bull trout in northeast Oregon

As bull trout are an endangered species, my objectives were to identify: (1) cues for migration, (2) whether co-occurring life-history forms interbreed, and (3) potential spatial genetic structuring in the South Fork Walla Walla River (SFWW). I PIT-tagged > 1600 bull trout and used passive detections (at in-stream antennae) to determine movement timing and life-history form. I demonstrated that juvenile and subadult bull trout migrated on a spatial and temporal continuum, predominantly at night. Furthermore, seasonal migration was associated with changes in minimum temperature. This study indicates that bull trout movement patterns are much more variable and continuous than previously assumed.I assessed genetic differentiation (using 11 microsatellite loci) and found that resident and migratory bull trout interbreed, and that there is no spatial genetic structuring in the SFWW. While different life-history forms have the potential to interbreed, behavioral variability may have fitness consequences and conservation value as well.