Floating guidance structures are intended to promote safe in-stream passage for juvenile salmon migrating downstream through reservoirs. However, the ability of an engineered structure to guide fish to safe passage has been primarily tested either after large-scale implementation in existing reservoirs or in laboratory studies and computer simulations without live subjects. Research is needed that integrates environmental fluid mechanics with fish behavior to study how hydraulic conditions around a floating guidance structure trigger swimming behaviors. In this study, an outdoor experimental channel was used for two objectives: 1) to identify the hydraulic signature of a floating guidance structure at increasing angles to the flow (20, 30, and 40 degrees), and 2) to measure fish swim responses in relation to channel hydraulics. The flow field surrounding a floating guidance structure at three angles of deployment was characterized using an array of acoustic Doppler velocimeters. Swimming behaviors of juvenile Chinook salmon in the experimental channel were recorded using underwater videogrammetry and transformed to three-dimensional swim paths. A statistical method for behavioral point change detection identified the most likely locations of behavior changes in fish as they first encountered the guidance structure. Finally, the locations of behavior changes were compared to the hydraulic signature of each guidance structure. Results corroborated previous evidence that guidance structures at low angles produce the most uniform hydraulics at the low magnitudes along their length. Fish were found to consistently exhibit behavior changes (i.e. halting, passing) upstream of the guidance structure, but observational biases restricted definitive conclusions of which hydraulic variables incited behavioral changes of juvenile salmon. Results highlighted the importance of understanding fish behavior near guidance structures for effective passage of juvenile salmon.