Before the 1940s, as many as half a million to one million Columbia River chum salmon returned to the river to spawn as far up the river as Celilo Falls.
With the loss of habitat and overfishing, the total population in the Columbia dropped to 1,000 to 10,000 fish and 14 of the 17 evolutionary significant units (ESUs) are now considered at a high risk of extinction or extirpated, according to Todd Hillson, Lower Columbia River chum salmon program leader at the Washington Department of Fish and Wildlife. He spoke Tuesday, July 11, at a meeting of the Northwest Power and Conservation Council’s Fish and Wildlife Committee in Vancouver, Washington.
The other three ESUs — Grays River, Washougal and lower Gorge populations — are considered to be at low to moderate risk of extinction. (ESUs consist of members of the same species — in this case chum salmon — that have adapted to prosper in specific places.)
The decline of chum salmon began in the 1940s and is due to loss, degradation and access to spawning habitat, changes in the estuary ecology and habitat, altered mainstem and tributary hydrology — much of that due to the addition of Bonneville Dam that flooded the salmon’s spawning areas — and overharvest.
“Where we built our towns on the lower end of the river, that was their habitat,” Hillson said of the chum.
Lower Columbia River chum salmon were listed for protection under the Endangered Species Act in 1999. In 2004 the Lower Columbia Fish Recovery Board developed a plan for their recovery as well as for other ESA-listed salmon as part of the Northwest Power and Planning Council’s Subbasin Plan (the NPPC is now the Northwest Power and Conservation Council). The LCFRB updated the recovery plan in 2010, and NOAA finalized the federal recovery plan in 2013.
As much as half of the up to 1 million fish that once spawned in the river were harvested, but harvest has now been completely stopped for both hatchery and wild chum, although there is some incidental take of chum, but the limit on the incidental take harvest is set at less than 5 percent of the projected run size each year.
Most of the chum spawning and incubation habitat was in off-channel or braided parts of the river, Hillson said. That habitat, which results in a higher survival for the fish, is needed especially when ocean conditions are poor. But off-channel habitat was typically found in the lower river and has since been limited by agriculture, dikes, levees and the growth of human populations.
Incubation before heading to the ocean is extremely important for chum fry. They are small (30 to 40 millimeters, which is 1.18 to 1.57 inches), compared to Chinook fry that are about 160 mm (6.3 inches), and once they hatch and emerge, Hillson said, they move out of the off-channel areas and head straight to the ocean.
“At that size, they are food for everything,” he said. Once in the ocean, survival is typically less than one-half of a percent. “With this low marine survival, freshwater survival rates must be high.”
Conservation hatcheries have helped reduce the extinction risk. About 175,000 fry have been released into the Grays River basin in southeastern Pacific County and western Wahkiakum County. And about 45,000 fry have been released into Duncan Creek downstream of Bonneville Dam.
In addition, Duncan Creek spawning channels were constructed in 2001 and upgraded in 2008 and 2011, as well as spawning channels in Hamilton Creek in the 1980s, also near Bonneville Dam. That habitat was upgraded in 2011.
As a result, egg to fry survival in the off-channel sites is improving: Duncan Creek averages about 54 percent and Hamilton Creek about 48 percent. The Grays River channel, which is not an off-channel site, has a survival rate of about 17 percent.
So, overall, how is recovery of Columbia River chum coming?
Grays River has the strongest population, Hillson said, and has a population that has returned in numbers far above the river basin’s delisting goal for 15 years in a row. The delisting goal is 1,600 spawners, but the actual return last year (2016) was 12,325 fish, the strongest return of all 15 years. “That’s a big rebound,” Hillson said.
The good news is that together, the Grays, Washougal and Gorge population returns in 2016 totaled 18,823 fish. The bad news is that the persistence probability for recovery continues to be very low for most ESUs.
For the upper Gorge population, the spawning goal for delisting of the ESU is 900 fish. The 2016 spawning count from fish that migrated from the river in 2012 was 115 fish, which has been about the average number of spawners since 2002.
The lower Gorge population with a delisting goal of 2,000 spawners is “not doing badly and are on a positive,” Hillson said. “Eight out of 15 years has been above the delisting goal.” Some 3,378 chum spawned in 2016 near Bonneville Dam.
Most of the lower Gorge population spawns in lower reaches of that area near Washougal, downstream to the I-205 Bridge that spans the Columbia River in east Portland. With a delisting goal of 1,300 fish for this section of river, last year’s return of adults to spawn tallied 3,120 fish.
“The quality and quantity of spawning and incubation habitat continues to be a strong limiting factor for recovery in these other areas, such as at Skomakawa, the East Fork of the Lewis River, and the Cowlitz River in Washington, and the Sandy River in Oregon, among many others.
Continued recovery will come with creating better habitat along with supplementation hatcheries and reintroduction where needed, Hillson said.