Abstract: Behavioral studies have been conducted over the last several years to assess downstream passage of juvenile salmonids, upstream passage of shad and reservoir movement of white sturgeon at hydroelectric facilities in the United States. Acoustic transmitters were surgically implanted into run-of-river fish and detection arrays were configured to track acoustically tagged fish. GIS analysis of fish approach and passage has provided valuable information to hydropower engineers who were seeking alternatives to operational configurations that would increase passage rates. For juvenile salmonid studies, GIS spatial analyses have included the evaluation of passage route efficiency, relative percent passage densities, normalized bin densities, approach elevations and top-spill nonselection. Passage route efficiency was measured by the proportion of smolts that selected a particular route of passage (powerhouse, top-spill or spillway). Relative percent passage densities and normalized bin densities highlighted zones of use in the forebay. Both passage route efficiency and relative percent passage were correlated to operational configurations. Approach elevations were analyzed for smolt positions within 300 feet of the dam. Top-spill nonselection presented three-dimensional positions of smolts that had approached within 300 feet of the top-spill bypass structure but did not pass. All GIS analyses were examined for trends between years and species and have led to operational configuration modifications to provide increased successful smolt passage. The GIS analyses used during these behavioral studies will be presented.