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NW Fishletter #388, Dec. 3, 2018

[13] Chum Are Spawning, Despite Low Precipitation

A dry November didn't stop the chum from spawning in the lower Columbia River, where federal agencies are operating dams to provide additional flow for the late-spawning fish.

U.S. Army Corps of Engineers' Doug Baus, who chairs the Columbia River Technical Management Team (TMT), said biologists recently counted 355 chum spawning in the usual places below Bonneville Dam, and more potentially out there.

"This is about when we would see that next wave of chum arrive and spawn," he told fellow TMT members on Nov. 28.

Paul Wagner, the group's NOAA Fisheries representative, said fish counters at the dam also noticed an uptick of chum making it through the fish ladders, with latest numbers showing 163 chum passing the dam so far this year.

"So the early arriving chum, wherever they went, have been replaced or supplemented with this current population that is a reasonable number so far," he said. "Now, if the rain would just cooperate."

The U.S. Army Corps of Engineers has been increasing flows over Bonneville Dam to ensure eggs in chum salmon redds below the dam remain submerged as river levels fluctuate this fall and winter.

Beginning Nov. 2, the agency began its annual chum operations, holding the river level to between 11.5 feet and 13 feet above sea level to aid spawning at the mouth of Hamilton Creek in the Columbia River Gorge. Officials say that water is released from reservoirs as far away as Hungry Horse and Libby dams in Montana to help keep water flowing to the redds and compensate for the typically lower flows in late fall and early winter.

Columbia River chum were listed as threatened under the Endangered Species Act in 1999. Historically, more than 1 million returned to the lower Columbia River, but their numbers are now greatly diminished.

NOAA Fisheries' most recent status review for Columbia River chum in 2016 says the population remains at moderate to high risk. It notes that ocean conditions have a strong influence on the survival of emigrating juveniles, and that poor ocean conditions and land development in the lower river area could put further pressure on these populations.

A joint news release from the Bonneville Power Administration (BPA), the Corps and the U.S. Bureau of Reclamation says chum salmon are the last to return to the Columbia River to spawn, and lay their eggs below the dam in areas where warm water pushes up through the gravel beds and quickly incubates their eggs.

BPA funds two hatchery programs and has built spawning habitat, efforts that appear to be succeeding, the news release said. More than 20,000 chum returned to the Columbia River in 2015, the highest number since 2002, it said.

November's precipitation has been below normal throughout much of the Columbia Basin, and well below normal in some of the more southern locations. As of Nov. 28, lower tributaries of the middle Columbia River received about1.5 inches, or 49 percent of normal precipitation for the month so far. The river above The Dalles had gotten 2.4 inches, or 76 percent of normal; and above Grand Coulee Dam had received 3.9 inches, or 89 percent of normal.

On the Snake River, locations above Hells Canyon Dam with 1.3 inches were sitting at 69 percent of normal; while the middle Snake River tributaries received 1.2 inches, which is 58 percent of normal. Upper Snake tributaries, however, were doing well with 2.6 inches, which is 103 percent of normal.

Baus reported that forecasts show below average chances for precipitation in the Columbia Basin through early December, with above average chances after that. "So, hopefully we can see some of that precipitation help with the chum operation," he said. -K.C. Mehaffey

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NW Fishletter is produced by NewsData LLC.
Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: K.C. Mehaffey
Phone: (206) 285-4848 Fax: (206) 281-8035

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