Northeast Oregon steelhead run has made it over Bonneville Dam

October 5, 2020
Northeast Oregon steelhead run has made it over Bonneville Dam

With most of the Grande Ronde and Imnaha steelhead now past the Bonneville Dam, an estimated 2,550 will make it past the eighth and final dam and on to home waters to spawn.

On an average year, the number of fish Enterprise Assistant Fish Biologist Kyle Bratcher said he figures will make it over the Lower Granite Dam is 75% of the 3,400 steelhead that crossed Bonneville. Some of those will head up the Clearwater River at Clarkston, Wash., 40 miles from Lower Granite, while the Grande Ronde fish have another 33 miles to go before taking a right turn at Rogersburg, Wash., to head to their home waters.

“From here on, our monitoring will be mostly watching those fish move through the system on their way to the home rivers,” Bratcher said.

A little bit of good news for both researchers and anglers, Bratcher said, is that rough estimates of wild steelhead suggests they are showing up in about the same abundance as hatchery fish — about a 50/50 split.

Bratcher said to get a good estimate of steelhead returning from the ocean, hatchery fish are tagged with passive integrated responder tags, or PIT tags, before they are released into the river.

“We know the ratio of fish that have PIT tags because we know the total number of fish, he said. “Therefore, we can estimate the number of hatchery fish by expanding the number of detections based on the tagging rate.”

He said if 100 fish are released and 10 are tagged, then he knows that each tag detection represents 10 fish.

For wild fish, Bratcher said there isn’t a starting population estimate.

“We do have some programs that tag wild fish and some loose relationships that can suggest what those numbers might be but they aren’t very good,” he said.

However, he said he can also use dam counts and average historic ratios. At Lower Granite Dam, on average, about 25% of the wild fish that pass are bound for the Grande Ronde and about 8% are bound for the Imnaha.

“These still are not as accurate as the estimates for hatchery fish, but it gives us some idea and guidance,” he said. “Simply put, there are too many variables that we cannot account for when estimating wild fish.”

Despite the slight uptick in numbers this year, Bratcher said anglers are finding the early arrivals in the Grande Ronde to be a bit tough to come by.

“Despite some improvement over last year’s run, I’d like to reiterate that I wouldn’t call this a good run by any stretch,” he said.

The size of the fish reported to the district office are meeting other predictions, as well. Bratcher said 20% of the returning steelhead were in the ocean one year, while 80% spent two years in the Pacific Ocean.

So far, Bratcher said, he hasn’t had any reports from anglers on the Imnaha.

“I’m expecting a similar split between wild and hatchery fish there, and even fewer one-salts coming in around 10 to 15% of the total run,” he said.

Fall chinook and coho also are in the Grande Ronde system this year and Bratcher said with the diversity of potential catches this year, he is encouraging anglers to brush up on their species identification at the Oregon Department of Fish and Wildlife salmonid page.

“Personally, I’d save these on my cellphone so I have it on the river,” he said.

Besides being able to identify the different species in the rivers this fall, Bratcher said anglers should keep up on regulation changes.

As for future ocean conditions, the outlook is promising. Bratcher said the Pacific is experiencing La Nina conditions.

“La Ninas are typically a good thing for the survival of our anadromous fish if the conditions are strong enough,” he said.

The current models suggest a “moderate” La Nina that Bratcher said had a pretty good chance to last through the winter, though it’s still early and things could change.

“If we do have solid La Nina conditions and you find yourself enduring a wetter/snowier than normal winter, remember, it’s good for the fish and skiers, so keep your fingers crossed,” he said.

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