LAUSR

While navigating through the same migratory corridor, different species may experience differing reproductive success due the interaction of species-specific movement behavior with habitat configuration. We contrasted the migratory behavior of White Sturgeon Acipenser transmontanus and fall-run Chinook Salmon Oncorhynchus tshawytscha , two native fishes in Central Valley of California. These species co-occur in the region’s Yolo Bypass floodplain seasonally, but they represent disparate reproductive strategies: White Sturgeon are iteroparous, spawning multiple times throughout their lifespan, while Chinook Salmon are semelparous, spawning only once in their lifespan. Except for brief windows when the Yolo Bypass connected to the Sacramento River during flood conditions, migrating White Sturgeon and Chinook Salmon that entered the Bypass from 2012 to 2018 had to turn around and exit it in order to complete a successful spawning migration up the Sacramento River. This “exit behavior” was critical to migratory success when the Bypass was not flooded. Between March 2012 and May 2018, the median probability of acoustically-tagged fall-run Chinook Salmon exiting the Yolo Bypass at its southern extent was estimated to be 0.74 (0.58–0.87 95% credible interval), while an individual White Sturgeon had a median exit probability of 0.99 (0.96–1.00 95% credible interval). Our results suggest that White Sturgeon successfully exit the Yolo Bypass more consistently than fall-run Chinook Salmon, indicating that fall-run Chinook Salmon are at higher risk of stranding in the Yolo Bypass. The difference in probability of exit between these two species has implications for how to manage for migratory success in altered habitats. Floodplain · Fish passage · Bayesian · Telemetry · Behavioral ecology · Movement · Stranding.