Sockeye salmon repatriation leads to population re-establishment and rapid introgression with native kokanee

Re-establishing salmonid populations to areas historically occupied has substantial potential for conservation gains, however, such interventions also risk negatively impacting native resident stocks. Here, we assessed the success of the hatchery-assisted reintroduction of anadromous sockeye salmon (Oncorhynchus nerka) into Skaha Lake, British Columbia, Canada, and evaluated the genetic consequences for native kokanee, a freshwater-obligate ecotype, using single nucleotide polymorphism genotypic data collected from reference samples of spawning Okanagan River sockeye and Skaha Lake kokanee pre-sockeye reintroduction, along with annual trawl survey and angler-caught samples obtained over an eight-year period. Significant differentiation was detected between sockeye and kokanee reference samples, with >99% stock assignment. Low proportions of sockeye and hybrids were detected within 2008 and 2010 age-0 trawl samples, however, by 2012, 28% were sockeye, rising to 41% in 2014. The number...