Thesis (M.S., Natural Resources) -- University of Idaho, 2015 | While a number of anthropogenic threats have been attributed to the population declines of Pacific lamprey (Entosphenus tridentatus), the poor passage of this species at hydropower dams on the Columbia River (~50% success rate) has been identified as a leading causative agent. This thesis sought to examine the potential mechanisms at hydropower dams responsible for limiting passage by exploring Pacific lamprey behavior at three different scales. The first scale was dam-wide, which sought to understand differences in behavior between Pacific lamprey and Chinook salmon (Oncorhynchus tshawytscha), a species which has high passage success at these dams (>95%). The second scale was a fishway-scale, where an acoustic camera was placed within fishways to identify the swimming behavior and potential mechanisms inducing passage failures. The final scale was a site-specific study, which attempted to identify the hydraulic and structural elements at a known passage bottleneck responsible for liming Pacific lamprey passage.