Record Number of Fall Chinook Pass Through Bonneville Dam

2013 marks a record year for the Chinook (King) salmon runs on the Columbia River. Over 1 million salmon have passed through the Bonneville Dam located near the mouth of the Columbia River. Historically, the Fall Chinook run is the biggest single run of the year far exceeding the Spring and Summer season runs. In addition this Fall, 68,000 fish passed through the dam in a single day. According to Ben Hausmann, senior fish biologist for the Army Corp of Engineers at the Bonneville Dam, that is the highest daily run count since they began counting fish.

Bonneville Dam on the Columbia River

The Bonneville Dam was built in 1938, and from its inception, fish passage was one of its original concerns. As you see in the video, the fish ladders provide a safe navigational passage through the dam for the adult salmon. There are two main ladders, one on the Washington side with the newer Powerhouse 2, and the other on the Oregon side, with Powerhouse 1. Whichever entrance the fish encounter, there is a spillway that was added to provide better passage for the juvenile fish.

Originally, the spillway was was added to provide flood control. As fish passage became more of a concern over time, especially for the juveniles, the dam now spills only to improve fish passage. By August 31, most of the spill that occurs during the Spring season officially ends, regardless of excess water levels. According to Hausmann, by then, the vast majority of the juveniles have already navigated through the dam.

So why the banner year for Chinook?

Hausmann points to a number of factors, including the year the salmon went out as juveniles, and the water flow levels that enabled them to go quickly through the spillways. “You know this was a perfect storm of good conditions. You couple that with good ocean conditions, and the improvements we’ve made at the dams and operationally what we’re able to do, that’s kind of the suite of things that makes for a success story”, says Ben Hausmann.

Fall Chinook Salmon Passing by Counting Window

In a separate room, two fish counters, record and identify each fish as it crosses the vertical line.

Comments

  1. Chris Foster says

    Perhaps Mr. Hausman should have been more clear when he states “overall dam survival for juveniles is 97%”. Someone please correct me if I’m mistaken, but I believe that figure is for Bonneville alone. With eleven dams on the main stem and hundreds more on tributaries, the actual “overall” loss is quite high. So for downstream fish, Bonneville takes 3% from an already much diminished number due to loss at upstream dams…correct?

    • says

      Hi Chris:

      If it’s not clear in the video that Mr. Hausmann is specifically referring to the Bonneville Dam when he mentions the 97% survival rates for the juveniles, that would be our (CUPS) fault. Yes, you are correct, while 3% loss does not seem high by itself, it is a cumulative loss that occurs throughout the dams. I think the actual number of dams on the main stem and tributaries is closer to 50 though, not in the hundreds. I was impressed during our visit, the dam continues to try to improve those survival numbers. Not that long ago, the survival rates at Bonneville were 94%, and Hausmann emphasized the significance of those improvements based on the cumulative losses that occur as the fish progress through the other dams.

      • Chris Foster says

        Thanks Fred-

        Glad to hear they are getting better at managing the downstream migration at Bonneville. I’m not sure just how they count them, but Columbia Riverkeeper says “14 main stem dams and a total of 450 within the basin” (probably including Canada). History professor Bill Lang of P.S.U. says “The Columbia River Basin is the most hydroelectrically developed river system in the world. More than 400 dams — 11 run-of-the-river dams on the mainstem — and hundreds of major and modest structures on tributaries block river flows..”. I think its important to keep the immensity of the dam management task and its impacts in perspective.

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