The first sockeye of 2020, a naturally produced female, returned to Redfish Lake Creek trap near Stanley on July 31 and a second arrived on Aug. 2, which are among the 412 sockeye that have crossed Lower Granite Dam through Aug. 2 and signals a substantially larger return to Idaho than last year.
This year's sockeye return appears to be slightly later than usual, and fisheries managers expect more fish will cross Lower Granite, which is the last dam the fish cross before reaching Idaho. Based on historical conversion rates between Lower Granite and the Sawtooth Basin, if no more fish crossed the dam, about 124 to 165 sockeye would return to the basin this year and likely surpass the last two year's returns.
Only 17 sockeye completed the migration to the Sawtooth Basin in 2019, which was the lowest in more than a decade, and 113 made it in 2018.
This year's return over the dam is already the highest since 2016, when 816 fish were counted at the dam.
While dam counts are higher this year, the fish still have a long way to go before reaching the Sawtooth Basin, where they will be trapped and transported to the Eagle Hatchery. Based on genetic analysis, some of those fish will be incorporated into the captive broodstock at the hatchery and the remaining fish will be released to Redfish Lake in mid-September to spawn naturally.
Fisheries managers were expecting an uptick in returns this year thanks to relatively cool water temperatures that benefit migrating fish and improvements to the way young sockeye were released into the Stanley Basin to migrate to the ocean.
In 2017, young sockeye released from Fish and Game's Springfield Hatchery had very low survival as they headed to the ocean. Biologists determined it was caused by their inability to acclimate to the soft water (water with low amounts of dissolved minerals) in Redfish Lake Creek after being raised in comparatively hard water (water with higher amounts of dissolved minerals) at the Springfield Hatchery.
Since then, biologists have acclimated the young sockeye at the Sawtooth Fish Hatchery near Stanley, which has water that provides a happy medium between the two. The young fish released after being acclimated made it to Lower Granite Dam with record survival rates in 2018 and 2019, which made biologists hopeful they would see a larger adult return starting this year.
Sockeye salmon typically spend two years in the ocean before making the return journey, meaning this is the first year Springfield Hatchery fish released using the new method are returning as adults. The hatchery released its first smolts in 2015, which significantly increased the number of young sockeye raised and released in Idaho, but the fish still face daunting challenges.
Sockeye returning to the Sawtooth Basin from the Pacific must complete a 900-mile migration though the Columbia, Snake and Salmon rivers that includes crossing eight dams and climbing 6,500-feet elevation.
When Idaho sockeye were listed in 1991 under the federal Endangered Species Act, only four adult sockeye returned to the Sawtooth Basin. The total number of sockeye that returned from 1991-99 was 23 fish, including two years when no sockeye returned.
Over the 10 years spanning 2010 to 2019, the annual sockeye return to the Sawtooth Basin averaged 558 fish, with annual returns ranging from 17 in 2019 to 1,579 in 2014.