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Monday, March 4, 2024
March 4, 2024

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Chum salmon return to Columbia in big numbers

Pacific blob, El Niño could be trouble for future populations

The Columbian

This winter’s Columbia River chum salmon return could be the largest in more than a decade.

Fisheries biologists monitoring the return say the 2015 run could be as high as 20,000 salmon — the largest since 2002. In 1999, the federal government listed the Columbia River chum salmon as threatened under the Endangered Species Act.

According to the Washington Department of Fish and Wildlife, the vast majority of returning chums are wild in origin. The majority of this winter’s returning adults left the Columbia as fry in 2012. The numbers are encouraging, but they are still a far cry from the historic returns. Before the populations began to crash in the early 1950s, runs estimated at more than 1.3 million chum came back to the Columbia.

Called “dog salmon” because of their large teeth, chums are the last spawning salmon of the year to return to the Columbia, and their offspring are the first to leave. They have the largest natural range of any Pacific salmon, but they’re listed as threatened in the lower Columbia River and the Hood Canal.

Todd Hillson, a WDFW fisheries biologist charged with salmon recovery in the lower Columbia, said a limiting factor for their populations is habitat. Historically, they were distributed from the mouth of the Columbia up to the Walla Walla River. Now, their habitat typically limited to the lower third of the mainstream of the Columbia and its tributaries. One of their mainstream spawning areas is located near the Interstate 205 Bridge.

“The loss of that habitat was probably the nail in the coffin for chum. They like the lower channels and upwelling areas and it’s along those areas where everybody builds cities and farms,” he said.

On the lower Columbia, the Bonneville Power Administration has funded two hatchery programs and new spawning habitat for chum.  In 2011, BPA added capacity to two spawning channels on tributaries just below the Bonneville Dam.

When it comes to managing chum, and migratory fish in general, humans can control and improve variables like hatchery programs, river habitats and harvests, but the one variable they can’t control is likely also the biggest — the ocean.

Salmon that spawn in the Northwest and the food they eat to bulk up thrive in the cold waters of Pacific, but the blob of warm water that settled along the West Coast last year made circumstances unusual. The water that came up pushed out the fattier cold water plankton younger salmon depend on and brought with it a leaner, more tropical species.

“Warm waters doesn’t provide the groceries for juvenile fish,” said state fish biologist Mike Scharpf.

Scharpf said biologists saw a slight decline in returning coho populations this year. Those fish were maturing as the blob was forming. Now they’re waiting to see if the same will be true in other salmon varieties.

This winter’s returning chum are too old to be impacted by the sea change, Scharpf said, but those coming next winter and the  year after might have been affected.

“If you look at long-term trends, warm water and El Niño leads to decreased populations in the past,” he said.