Warm water slows steelhead return to Snake River, tributaries
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Published 5:30 am Saturday, October 4, 2025
State district fish biologist predicts larger 2-salt steelhead to make up less than 1/3 of return
Autumn-like temperatures have been slow to arrive in Northeastern Oregon, and the sluggishness also has afflicted steelhead.
But a state fish biologist remains optimistic that this year’s return of the ocean-going trout will give anglers ample opportunities through the fall and winter and into next spring.
Kyle Bratcher is the district fish biologist at the Oregon Department of Fish and Wildlife’s Enterprise office. In August, after checking reports of steelhead numbers starting their migration up the Columbia River, Bratcher began to believe this could be one of the better years for steelhead angling in the past decade on the Grande Ronde, Imnaha and Wallowa rivers.
Bratcher’s optimism was based on steelhead numbers at Bonneville Dam near Cascade Locks, the first of the dams the fish have to pass before reaching the Snake River and tributaries such as the Grande Ronde.
But as summer waned, the steelhead weren’t arriving in comparable numbers at McNary Dam near Umatilla.
The culprit, Bratcher thinks, is warm water.
Steelhead and other anadromous fish don’t swim as swiftly through the slack water of reservoirs when the water temperatures are relatively high. In the last week of September, the water just below McNary Dam was around 70 degrees — about 5 degrees warmer than usual for that period, Bratcher said.
The average temperature at the Eastern Oregon Regional Airport in Pendleton during September was 68.5 degrees, which is 5 degrees above the long-term average.
(Average temperature is derived from the average of each day’s high and low temperatures.)
At the Hermiston Airport, the average temperature in September was 69.8 degrees — 5.2 degrees above average.
As of Thursday, Oct. 2, the water below McNary Dam had cooled to 67 degrees.
“This is far warmer than any recent year and is presumably holding those fish up a bit,” Bratcher wrote in an email Oct. 2. “We did see a significant bump in passage at McNary Dam yesterday and I think with cooling water we’ll still see those fish move into the Snake River soon.”
Although Bratcher doesn’t expect quite as bountiful a run of hatchery steelhead as he did in August, he still anticipates a “worst-case scenario” of a run similar to last year’s.
“I still suspect we’ll see at least a moderate increase over last year’s numbers,” he wrote in the email.
The steelhead season started Sept. 1 and runs through April 30, 2026.
Anglers can keep up to three hatchery-raised steelhead per day, with no season limit. Wild steelhead must be released. Hatchery fish have a clipped adipose fin — the small, fatty fin on their back near the tail.
Steelhead size
Based on records this year at Bonneville Dam, Bratcher said in August he expects most steelhead will be 1-salt fish — those that spent one year in the Pacific.
That’s not unusual, he said, but it means anglers are more likely to hook fish in the 23- to 25-inch range rather than the larger 2-salt steelhead, which he expects will make up less than one-third of the return.
The ratio of 1-salt to 2-salt steelhead varies each year, and it’s all but impossible to predict, Bratcher said.
Why some fish spend two years in the ocean instead of one — and why some rainbow trout never swim in saltwater at all, staying in the Columbia River — is a mystery, he said.
Multiple factors, including food availability, certainly affect the ratio.
Ultimately, though, the differences help to create “resiliency” in the steelhead population, Bratcher said.
If few 1-salt fish survive one year, the 2-salt fish and the rainbow that never enter the ocean can help offset the losses.
While 2-salt females tend to produce more eggs, they also are more vulnerable to predators and other risks because they spent twice as long in the Pacific, Bratcher said.
In contrast, 1-salt fish reduce their exposure to those threats, but they aren’t as efficient at reproducing.
It’s a complex relationship, he said, an adaptation that he appreciates as a biologist.
Wild steelhead
Bratcher said these steelhead, which are off limits to sport anglers, have also far outpaced pre-run projections.
The original forecast for the Columbia River was 17,000, but as of Aug. 21 the count at Bonneville Dam was 48,000 wild steelhead.
Predicting wild steelhead is even more challenging than for hatchery fish, he said, because far fewer wild steelhead have tracking tags.
Bratcher is estimating about 8,000 wild steelhead will return to the Grande Ronde River this year, and about 2,000 to the Imnaha.
“I expect a good return of wild fish compared to recent years,” he wrote in a recent email update. “I do want folks to keep in mind this is still a long ways from what historic abundance would have been, and recovery efforts are still needed.”
