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Sockeye Salmon Reintroduction to the Canadian Columbia River – Lessons from Small-Scale PIT Tag Releases

Patrick Zubick

Okanagan Nation Alliance, 961 Waterloo Crescent, Castlegar, BC V1N4M3

The Canadian reaches of the Columbia River were once home to three known sc’win (sockeye salmon, Onchorhynchus nerka) rearing lakes, with the potential for up to five others, which may have had limited accessibility. These runs were extirpated with the construction of the Grand Coulee Dam in 1939 but once comprised a major proportion of the sockeye salmon production in the Columbia River. In 2020, Okanagan Nation Alliance (ONA) Fisheries Department, as guided by Syilx Nation Leadership, began including limited scientific experimentation with Ceremonial sockeye fry releases. We performed two releases of passive integrate transponder (PIT) tagged sockeye salmon fry to provide an indication of how sockeye salmon will behave upon reintroduction. We released 5789 PIT-tagged fry to the Columbia River at Castlegar in 2020 and 1998 PIT-tagged fry in 2021; we also released 1910 PIT-tagged fry to rear in the Arrow Lakes in 2021. The PIT array network distributed throughout the US portion of the Columbia River was queried to provide preliminary estimates of fry to smolt survival and migratory behaviour. For the 2020 release cohort, sixty-two fish were detected downstream of the release point the same year as release, eighteen the year after and two in 2022. Similarly, for the 2021 release cohort six fish were detected downstream in the same year as the release (all Lake Roosevelt rearing fish), twenty-seven the year after and six in 2023. The average outmigration date for each release cohort was calculated, and it was found that fish which displayed normal migratory behaviour by out-migrating after 1 – 2 years of rearing, left their rearing lakes on an average date of May 15th. These results contrast with an average date of outmigration on August 4th, for fish that displayed non-normal migratory behaviour and outmigrated as fry. Cormack Jolly Seber (CJS) analyses were performed on each release cohort to determine survival along different segments of their migration. Survival for the 2020 release to Rocky Reach Dam was 3.3 % and then 45.7 % to Lower Columbia grouped dams (McNary, John Day, and Bonneville), for the 2021 cohort, survival was 2.3 % for the grouped release cohorts to Rocky Reach and 37 % to Bonneville Dam. Returning adult sockeye from the 2020 release class were tracked, with one returning as a 0-year ocean fish, one as a 1-year, and two as 2-ocean-year fish. These results have provided valuable, initial insight to inform reintroduction study design as part of the growing transboundary, Columbia River salmon reintroduction initiatives.