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

Abstract

Re‐establishing salmonid populations to areas historically occupied has the 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 the reference samples of spawning Okanagan River sockeye and Skaha Lake kokanee presockeye 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 of hybrids detected rose proportionally with the increase in sockeye and exhibited an intermediate phenotype. Our results indicate that the reintroduction of anadromous sockeye to Skaha Lake is succeeding, with large numbers returning to spawn. However, hybridization with native kokanee is of concern due to the potential for demographic or genetic swamping, with ongoing genetic monitoring necessary to assess the long‐term effects of introgression and to support interactive fisheries management.

An ancient selective sweep linked to reproductive life history evolution in sockeye salmon

“…29 15Shuswap LakeEagle RiverBritish Columbia, CanadaFraserKokaneeStream90.28Taylor et al . 29 16Skaha LakeOkanagan RiverBritish Columbia, CanadaColumbiaSockeyeStream330.02Veale & Russello 71 17Penticton ChannelBritish Columbia, CanadaColumbiaKokaneeStream190.08Veale & Russello 71 18Okanagan LakeOkanagan LakeBritish Columbia, CanadaColumbiaKokaneeShore1440.99Lemay & Russello 59 Mission CreekBritish Columbia, CanadaColumbiaKokaneeStream1360.10Lemay & Russello 59 19Wood LakeWood LakeBritish Columbia, CanadaColumbiaKokaneeShore480.92Frazer & Russello 42 Middle Vernon CreekBritish Columbia, CanadaColumbiaKokaneeStream480.28Frazer & Russello 42 20Kalmalka LakeKalmalka LakeBritish Columbia, CanadaColumbiaKokaneeShore320.95Veale & Russello 71 Coldstream CreekBritish Columbia, CanadaColumbiaKokaneeStream320.23Veale & Russello 71 21Christina LakeChristina LakeBritish Columbia, CanadaColumbiaKokaneeShore481.00Frazer 70 Sanders CreekBritish Columbia, CanadaColumbiaKokaneeStream480.07Frazer 70 22…”

Risk assessment for the reintroduction of anadromous salmonids upstream of Chief Joseph and Grand Coulee Dams, Northeastern Washington

“…Seaward migration of kokanee also has been observed in Skaha Lake, British Columbia (Richard Bussanich, Okanagan Nation Alliance, oral commun., January 5, 2017), where Sockeye Salmon were reintroduced. Interestingly, reintroduction of Sockeye Salmon into Skaha Lake has led to hybridization with kokanee (Veale and Russello, 2016). Veale and Russello (2016) reported that hybrids represented 15 percent of age-0 fish, were intermediate in size, and had reduced fitness for traits associated with anadromous and freshwater life histories.…”

“…Interestingly, reintroduction of Sockeye Salmon into Skaha Lake has led to hybridization with kokanee (Veale and Russello, 2016). Veale and Russello (2016) reported that hybrids represented 15 percent of age-0 fish, were intermediate in size, and had reduced fitness for traits associated with anadromous and freshwater life histories. Hybridization generally occurs through male kokanee associating with spawning Sockeye Salmon (Foote and Larkin, 1988).…”

Genetic Stock Identification Reveals That Angler Harvest Is Representative of Cryptic Stock Proportions in a High‐Profile Kokanee Fishery

“…In the case of kokanee, the application of population genomic techniques has allowed for the identification of outlier loci that are associated with reproductive ecotypes in a number of lakes throughout British Columbia and elsewhere across their distribution (Russello et al. ; Frazer and Russello ; Lemay and Russello ; Veale and Russello , , b). Importantly, the incorporation of outlier loci within genotyping panels has greatly improved the accuracy and precision of individual assignment and mixed‐composition analyses for management of kokanee (Lemay and Russello , ; Russello et al.…”

“…Importantly, the incorporation of outlier loci within genotyping panels has greatly improved the accuracy and precision of individual assignment and mixed‐composition analyses for management of kokanee (Lemay and Russello , ; Russello et al. ; Frazer and Russello ; Veale and Russello ), and other freshwater and marine species (Freamo et al. ; Corander et al.…”