Chum Salmon Pass Bonneville Dam In Record Numbers, Operations Under Way To Ensure Redds Remain Watered Downstream

A record number of threatened chum salmon passed Bonneville Dam late in 2024, with over 1,100 of the salmon passing the dam on their way upstream, the largest passage by chum at the dam since 1954. These are in addition to the chum that spawn annually downstream near the dam’s tailrace and are the subjects of an effort to restore the Columbia River run that at one time was near 1 million fish.

Over the past three years the chum population upstream of Bonneville has nearly doubled each year, according to a Bonneville Power Administration news release, which also said that BPA operations and habitat investments are supporting the return of this threatened species. However, little is known about where the fish that traverse the dam actually spawn.

While chum are the most abundant species of salmon throughout North America’s West Coast and Asia’s upper east Pacific coast, it is a different story in the Columbia River basin where chum salmon are listed as threatened under the federal Endangered Species Act and since the early 2000s their spawning and incubation efforts have been protected downstream of Bonneville Dam by fisheries managers and dam operators.

The Columbia River evolutionarily significant unit includes naturally-spawned chum salmon originating from the Columbia River and its tributaries in Washington and Oregon. The ESU also includes chum salmon from Grays River, Washougal River and Big Creek hatcheries.

Habitat loss, harvest and other factors caused their numbers to plummet during the last century to a low of just a few thousand fish returning to the river each year. An important ecological species and food for many species both aquatic and terrestrial, Columbia River chum were listed as threatened under the ESA March 25, 1999 and June 28, 2005, with a status update April 14, 2014.

In October 2022, NOAA Fisheries completed its 5-year status review of four species of salmon and steelhead, including lower Columbia River chum, concluding that all the species reviewed are in as much trouble today as they were at the last status review in 2016 and should retain their current listing status (https://media.fisheries.noaa.gov/2022-10/Sign4_5-Yr_Review_LCR_FINAL_19Sep2022_SMR.pdf). In the review, NOAA said “the collective risk” has not changed significantly and the “overall level of concern remains the same.”

Chum are the last salmon of the year to return to the Columbia to spawn, and their young are the first to leave for the ocean in the spring. Chum salmon generally spawn from November 1 to mid-December each year downstream of Bonneville Dam in areas where warm ground water pushes up through gravel. The warm water quickly incubates their eggs until emergence, which occurs by early April.

A 2000 NOAA Fisheries Biological Opinion said that chum that spawn downstream of Bonneville Dam were sensitive to dam operations, so those operations have changed to ensure that the downstream habitat remains watered throughout spawning and incubation to protect the redds (nests). Spawning began Nov. 1, 2024 and the incubation phase began Dec. 19 and will last through early April.

Tony Norris, BPA’s representative on the interagency Technical Management Team that makes recommendations on dam and reservoir operations to protect migrating anadromous fish, sturgeon and bull trout in the Columbia River, said BPA coordinates with other federal agencies, such as the U.S. Army Corps of Engineers and the Bureau of Reclamation, to manage downstream flows from the dam. TMT is made up of representatives from Columbia River tribes, the four Northwest states, and other federal agencies, including the U.S. Fish and Wildlife Service and NOAA Fisheries.

During the chum spawning phase, the flows below the dam are operated to maintain a specific water surface elevation range during the day that ensures the redds remain watered. That range is 11.3 to 13 feet in elevation above sea level. During the incubation phase the Corps holds the river below the dam at a minimum elevation of 11.3 feet.

For these operations to occur, water is released 350 miles upstream from Grand Coulee Dam, operated by the Bureau of Reclamation. Norris said management of the system is a balance of long-term water management and hourly operations to accomplish such a precise operation at Bonneville Dam when the water is released so far upstream.

BPA’s Geomatics and Geographic Information Services teams map historical chum spawning locations and provide critical information to help river operators protect the redds, BPA says. These maps focus on historical spawning sites near Ives Island that are directly influenced by operations at the dam.

Coordinating with the Pacific States Marine Fisheries Commission’s chum monitoring team, Geomatics’ land surveyors measure the location, elevation and adjacent water elevation of the chum redds. This information is essential to accurately identify the water surface elevation required to protect chum when they emerge from their eggs. The Geographic Information Services team then adds that data to a three-dimensional model of the chum spawning areas.

“The GIS visualizations and data have facilitated important changes to how chum operations are managed during periods of low flows in the Columbia River,” Norris said.

Periodic spawning grounds surveys, when weather permits, are conducted at the Ives Islands spawning grounds, as well as other nearby areas where chum spawn. Although the number of chum salmon that spawned this year won’t be available until June, according to Charles Morrill of the Washington Department of Fish and Wildlife, speaking at this week’s TMT meeting, the numbers of redds have been recorded at https://www.fpc.org/spawning/spawning_surveys/ODFW_reports/2024spawningsurveys.htm. The highest number of redds counted during any one survey was 714 on Nov. 24, 2024.

According to BPA, it has helped fund and maintain off-channel habitat for chum spawning below the dam, including at Hamilton Creek. Feeding into the spawning habitats around Ives Island, Hamilton Creek flows through the town of North Bonneville. A channel of Hamilton Creek was disconnected during the construction of Bonneville Dam’s second powerhouse, but the channel still experiences upwelling groundwater after sufficient rainfall has occurred. Chum were found to successfully spawn in this old channel.

In 2011, BPA funded a project to improve the channel and increase available habitat for spawning chum, including the creation of a second fork in the channel. The channel, called Hamilton Springs, provides chum with perfect spawning conditions. A natural filling spring, Norris said the channel is unaffected by operations at Bonneville Dam. In Hamilton Springs, chum emerge at a rate 10 times higher than fish spawned in the mainstem spawning areas.

“BPA has awarded contracts to the State of Washington and others to improve chum salmon habitat. It is encouraging to see the work contribute to the increase in returning adults,” said Executive Vice President for BPA environment Fish and Wildlife Scott Armentrout. “We will continue to build on this success and future work will add more opportunity for this species. I am grateful for the hard work BPA staff and contractors have done to make this possible.”

For background, see:

— CBB, November 1, 2024, NOV.-APRIL OPERATIONS AT BONNEVILLE DAM FOR ESA-LISTED CHUM SALMON TO BEGIN; LA NINA COMING, BRINGING WET WEATHER, POSSIBLE ‘DROUGHT REMOVAL’ HTTPS://COLUMBIABASINBULLETIN.ORG/NOV-APRIL-OPERATIONS-AT-BONNEVILLE-DAM-FOR-ESA-LISTED-CHUM-SALMON-TO-BEGIN-LA-NINA-COMING-BRINGING-WET-WEATHER-POSSIBLE-DROUGHT-REMOVAL/

— CBB, November 3, 2023, LOW WATER IN UPPER COLUMBIA HAS RIVER MANAGERS TWEAKING OPERATIONS TO AID ESA CHUM SALMON IN LOWER RIVER, HTTPS://COLUMBIABASINBULLETIN.ORG/LOW-WATER-IN-UPPER-COLUMBIA-HAS-RIVER-MANAGERS-TWEAKING-OPERATIONS-TO-AID-ESA-CHUM-SALMON-IN-LOWER-RIVER/

— CBB, March 2, 2023, LOW WATER, LOW FLOWS FORCE COLUMBIA RIVER HYDRO MANAGERS TO DROP BONNEVILLE DAM TAILWATER LEVELS AIMED AT PROTECTING ESA-LISTED CHUM SALMON, HTTPS://CBBULLETIN.COM/LOW-WATER-LOW-FLOWS-FORCE-COLUMBIA-RIVER-HYDRO-MANAGERS-TO-DROP-BONNEVILLE-DAM-TAILWATER-LEVELS-AIMED-AT-PROTECTING-ESA-LISTED-CHUM-SALMON/

— CBB, June 10, 2021, “A Million Chum Salmon Once Returned To Columbia River, Now Down To 20,000; WDFW Recovery Plan Aims To ‘Jump Start’ Population Rebuilding,” https://cbbulletin.com/a-million-chum-salmon-once-returned-to-columbia-river-now-down-to-20000-wdfw-recovery-plan-aims-to-jump-start-population-rebuilding/

— CBB, May 27, 2021, “Scientists Review Hatchery Programs For Recovering ESA-Listed Columbia River Chum Salmon; Supplementation, Reintroduction Priorities,” https://cbbulletin.com/scientists-review-hatchery-programs-for-recovering-esa-listed-columbia-river-chum-salmon-supplementation-reintroduction-priorities/

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