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Restoring the Lower Snake River

salmonSeptember 29, 2017

Some 157 of the 401 Snake River sockeye that passed Bonneville Dam this year made it into the Sawtooth Basin in Idaho. That’s the second lowest run into Idaho’s Sawtooth wilderness in the last 10 years.

The worst year was during the low and hot water conditions of 2015 when just 91 of the sockeye returned. Nearly half of those fish had to be trapped at Lower Granite Dam, far short of their destination in the Sawtooth Valley, and hauled to Eagle Hatchery. The other half completed the 900 mile journey to the Sawtooths. Snake River sockeye were listed as endangered under the federal Endangered Species Act in 1991.

The comparison, however, between this year and 2015 ends there.

About 4,000 Snake River sockeye passed Bonneville in 2015, part of a run of more than 500,000 sockeye that flooded into the Columbia River basin (most were headed into the upper Columbia River and the Okanagan Valley). But an estimated 90 percent of the Snake River fish perished in the more than 70 degree waters of the Columbia River before even arriving in the Snake.

This year, the total estimated run of sockeye was much smaller: the preseason forecast was 198,500 fish, with 1,400 of those headed to the Snake River. However, poor passage numbers at Bonneville Dam resulted in a mid-season downgrade in the forecast by the U.S. v Oregon Technical Advisory Committee to 88,200 fish as measured at the river’s mouth, with just 401 heading to the Snake River.

Overall, 227 sockeye salmon passed Lower Granite Dam, the most upstream of the four lower Snake River dams, and 157 were trapped in the Sawtooth Basin this summer, according to Idaho Department of Fish and Game information.

"We are very pleased with this return given the estimate of only about 400 Idaho sockeye made it to Bonneville Dam this summer based on PIT tag estimates," said Eric Johnson, research fisheries biologist for ODFG.

Biologists were concerned about so few fish crossing Bonneville in early summer and whether they would complete the 900-mile migration from the Pacific that includes crossing through eight dams and climbing 6,500-feet elevation to the Sawtooth Basin, IDFG said.

But Johnson said migration conditions were good for Idaho sockeye because rivers did not warm until most of the sockeye had already reached the Salmon River. Cool water from a higher-than-average snow pack helped their final leg from Lower Granite Dam about 30 miles downstream of Lewiston to the Sawtooth Basin.

"This year, we observed higher-than-average conversion rates between Lower Granite Dam and the Sawtooth Basin," Johnson said. Conversion rate is the ratio of fish that arrive at an upstream point, in this case the Sawtooth Basin, from a downstream point (Lower Granite Dam).

The run is well-below last year's return of 595 fish, IDFG continued, and the second-lowest in a decade. The 10-year average is 690 sockeye trapped annually in the Sawtooth Basin, which ranged from a high of 1,579 to a low of 91.

While recent sockeye runs to the Snake River are tiny compared with other salmon runs, they’re a vast improvement over the 1990s. When Idaho sockeye were listed only four adults returned to the Sawtooth Basin. The combined annual returns from 1991-99 was 23 fish, which included two years when no Snake River sockeye returned.

Idaho has a three-prong strategy to recover sockeye:

Adults returning from the ocean are collected annually in the Sawtooth Basin at Redfish Lake Creek and the nearby Sawtooth Fish Hatchery.

Some of those returning adults are spawned in the hatchery, and others released to spawn naturally in Redfish Lake. Fish and Game also raises in captivity a small population of adult sockeye that are spawned to augment those returning from ocean.

Those three sources provided about 740,000 young sockeye that were released, or naturally migrated from Redfish Lake, during spring, IDFG said.

All anadromous returning sockeye are incorporated into a brood year spawning matrix (this year is BY2017), with the exception of natural sockeye assigning back to Pettit or Alturas Lakes, said Marc Garst, fish production program manager at IDFG.

“We have released captive broodstock from Eagle Hatchery and NOAA into Redfish and Pettit Lakes to spawn naturally,” he said.

Some 99 adults were released September 12 in Pettit Lake from NOAA’s captive broodstock hatchery in Manchester, Washington. Broodstock at that facility serves “as a safety net for the Eagle Program in case of a catastrophic event,” Garst said.

IDFG’s Eagle Hatchery released 305 captive broodstock into Redfish Lake September 11 and 12.

NOAA released captive broodstock into Redfish Lake from Manchester September 12 (404 fish) and again September 20 (428 fish).

Overall, 1,137 sockeye have been released into Redfish Lake and 99 into Pettit Lake. The 157 fish that completed their journey will all be used as spawners in the hatchery, Garst said.

The justification for incorporating all anadromous returns into the BY17 broodstock matrix, according to Garst, is:

“Under the IDFG Springfield Master Plan (1454 Permit) at least 10 percent of the broodstock should be natural origin returns, but if those numbers are not possible then we can back-fill with hatchery origin anadromous returns to meet the goal of 10 percent. Our goal is to incorporate 50 percent of the anadromous return and transition from 100 percent captive spawners to 100 percent anadromous spawners over time. To maximize the effective population size and retention of genetic diversity in hatchery we aim to represent each family in the brood and equalize family size at the adult stage using genetic pedigree information. We will also try to represent anadromous run-timing during the selection of spawners.”

Johnson said it's still possible, but unlikely, more fish will return this fall.

"We will operate the trap until around the first of October in hopes of getting another fish or two, but I would not be surprised if this is our final count for the year," he said.

The best year for returns of sockeye to the Sawtooth Basin was in 2014 when 1,579 fish made the full journey. The year 2010 was second with 1,355; 2011 was 1,117; 2009 was 832, 2008 was 646; 595 in 2016; 272 in 2013; 257 in 2012; 157 in 2017; and 2015, the worst year, was 91.

 

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