This year’s return of Snake River sockeye salmon, Idaho’s most imperiled fish, is lagging far behind the 10-year average and isn’t expected to improve.
Through Monday, just eight sockeye had been counted at Lower Granite Dam on the Snake River in Washington compared to a 10-year average of 317. The fish are listed as endangered and have been struggling for decades.
Sockeye that make a 900-mile journey with an elevation gain of 6,000 feet to return to Redfish, Alturis and Pettit lakes in the Stanley Basin nearly blinked out in the 1990s when returns were often in the single digits. Some years, no adults returned. The fish were protected under the Endangered Species Act in 1991.
The run was somewhat stabilized when state and federal officials opted to take the extraordinary measure of bringing remaining fish into a captive breeding program. Returning adults were bred in hatcheries, and many of their offspring spent their entire life cycles in captivity while others were released to migrate as juveniles to the Pacific Ocean.
The move staved off immediate extinction risks but has yet to put the fish, which turn red during spawning and gave Redfish Lake its name, on the path to recovery. Annual adult returns, measured at Lower Granite Dam, have been highly variable since then, based largely on factors such as ocean conditions and the strength of spring runoffs. In 2014, 2,786 adult sockeye were counted at Lower Granite, a low number based on historic returns but a vast improvement from the 1990s. Last year, 276 sockeye were counted at the dam, and 113 eventually returned to the Stanley Basin where the 10-year average for returns is 620.
State and federal fisheries officials hoped the construction of the Springfield Hatchery in southeastern Idaho in 2013 would change the trajectory of the run. The hatchery has slowly ramped up its production and is on pace to hit its goal of releasing 1 million smolts annually. But thus far, the increased releases have not boosted adult returns.
The hatchery’s early years have been plagued by an unforeseen water chemistry problem. When the fish were released in Redfish Lake Creek, starting in 2015, many of them died before reaching Lower Granite Dam, the first they must negotiate on their way to the ocean. The low survival persisted into 2016 and 2017.
After months of study, fisheries managers determined the pH difference between the extremely hard and mineral-rich water at the hatchery and the super-soft water in Redfish Lake Creek was stressing the juvenile fish and causing many of them to perish before reaching dams on the Snake and Columbia rivers that also kill many fish.
To compensate, biologists started acclimating the fish in medium-hard water at Sawtooth Hatchery prior to release. The practice allowed the young fish to better adjust to the difference in water chemistry. The tactic appears to have led to an increase of survival for the juvenile fish. However, the change in operations won’t pay dividends in adult returns until next summer when the first group of fish released under the acclimation regime are expected to return as adults after spending a full two years in the ocean.
Sockeye returning as adults this year were released in 2017 when only about 16 percent of juvenile sockeye survived the trip from the Stanley Basin to Lower Granite Dam. The survival rate jumped to about 70 percent following the implementation of the acclimation process last year.
Biologists initially expected about 129 adult sockeye to return this year but now are unsure how many will return, because this year looks to be a down year for sockeye returns across the Columbia Basin. Regional fisheries managers recently downgraded their Columbia River sockeye return forecast by 39 percent. Most sockeye that enter the Columbia return to the upper reaches of that river, with far fewer heading up the Snake River and eventually the Salmon River to reach their spawning grounds.
“It is still early for most of these fish to have made it to Idaho. Approximately 50 percent of the run usually crosses Lower Granite Dam in the two weeks following July 4; thus, we will know more about the size of the Snake River sockeye run in the next couple of weeks,” Powell said.
He said it’s likely some of the fish this year will be returning after only spending one year in they ocean.
Barker may be contacted at email@example.com or at (208) 848-2273. Follow him on Twitter @ezebarker.