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Spring Chinook Salmon Run Shows Most
Impressive Run Since 2016 at Idaho Dam

by Eric Barker
Twin Times-News, May 12, 2022

Only 406 adult chinook had been counted at Lower Granite Dam as of Wednesday.

Graphic: Wild Chinook runs to the Lower Snake River as counted at the highest dam in place at the time. (1961-2020) Spring chinook are continuing to make an impressive showing at Bonneville Dam.

In the past 10 days, more than 62,500 adult springers have been counted in the dam's fish ladder. That includes nearly 13,500 on Tuesday alone and more than 7,000 on Wednesday. The season total, from March 15 through Wednesday, is an impressive 72,134.

That is the best to-date count since 2016, when more than 76,000 passed the dam during the same time frame. For context, it lags behind the 153,803 counted in 2015 and pales in comparison to the 326,271 counted in 2001. But it's a respectable showing and certainly better than the miserable count of just over 9,000 in 2017. The 10-year average, which has been declining over the past five years, is about 50,000.

Joe DuPont, regional fisheries manager at the Idaho Department of Fish and Game, said it now looks as though the run will exceed the agency's preseason forecast. The department is now forecasting the run could be strong enough to allow a harvest share of about 5,200 adult chinook on the Clearwater River and 4,119 on the lower and Little Salmon rivers.

It's nice to see, especially after five years of disappointing returns, but DuPont isn't surprised. That's because the run has been trending very slowly upward since it bottomed out in 2017.

"If you look at trends over time, when the run is declining from one year to the next, we tend to overestimate, and when the run is increasing from one year to the next, we tend to underestimate."

Chinook runs can spike and plunge as fast as a 30-pound springer can spool line. But DuPont is pleased the peak of this run seems to have some staying power.

"The fact that we have been seeing counts above 3,000 fish for over a week and many days over 6,000, that is a good sign that it's not just going to drop off to really low numbers."

Anglers can expect good fishing once the fish arrive in Idaho, but it has taken longer than normal for them to get here. That appears to be changing. A bottleneck developed below Lower Monumental Dam where the Army Corps of Engineers stopped spilling water at four of the dam's eight spillgates so it could repair worn parts. The work changed the hydraulics beneath the dam, essentially creating an eddy in front of the fish ladder and making it difficult for returning adult salmon to find the entrance.

Two of the spillways have been returned to service, and it looks as though it might have fixed the problem. The number of chinook passing Lower Monumental jumped from about 100 on Monday to nearly 900 on Tuesday and more than 1,000 on Wednesday. Repairs on the other two spillways may take another week or more to complete.

DuPont said if hydraulics continue to cause delays at the dam, Fish and Game and the Nez Perce Tribe are prepared to ask the corps to stop spilling water so adult fish can more easily find the attractant flow from the fish ladder. Doing so may come with a cost to juvenile fish migrating downstream, but DuPont said it would likely be a short term operation.

If the problem is fixed, DuPont said it's likely the delayed adult fish will storm upriver. Anglers prepared to catch that slug of salmon could be in for good fishing.

"My advice to you is to keep an eye on the dam counts so you can plan when to be on the river. If there are not additional fish passage issues, the fish should be able to get from Lower Monumental Dam to the lower Clearwater River in 3-5 days," he wrote in his weekly run update available here.

Only 406 adult chinook had been counted at Lower Granite Dam as of Wednesday.

Eric Barker
Spring Chinook Salmon Run Shows Most Impressive Run Since 2016 at Idaho Dam
Twin Times-News, May 12, 2022

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