The lower portion of the Sacramento River, California, has been highly engineered to protect low‐lying surrounding communities from annual flood events. While engineered floodplains have provided adequate protection for the surrounding communities, there remain unintended consequences to migratory fish that become stranded during high flow events. In April 2011, we rescued 24 threatened Green Sturgeon Acipenser medirostris that were stranded in two flood diversions along the Sacramento River. We tagged these 24 Green Sturgeon with acoustic tags and analyzed their survival and migration success to their spawning grounds. Additionally, we provided a population viability analysis to show the potential impacts of stranding and the benefits of conducting rescues at the population level. We found that 17 of these 24 individuals continued their upstream migration to the spawning grounds. Modeling suggests that recurrent stranding of a similar magnitude without rescue could affect the long‐term viability of Green Sturgeon in the Sacramento River. Population viability analyses of rescue predicted a 7% decrease below the population baseline model over 50 years as opposed to 33% without rescue. Despite the mitigated impact to the population with rescue, fish passage improvements should be considered as a long‐term goal for preventing population risks at flood control diversions.Received May 4, 2012; accepted December 6, 2012

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