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Ecology and salmon related articles

Bonneville Dam Fish Ladders:
Once a Spawn a Time

by Chris Woolston
VIA Magazine, October 20, 2011

Steelhead trout and salmon need the ladder at Bonneville. (reverendlukewarm/Flickr) It's no coincidence that Oregon's Bonneville Fish Hatchery is next door to the roaring Bonneville Dam. The dam doesn't just provide power to all of those hatchery buildings -- it gives the hatchery a reason to exist.

As the hatchery manager explained to me, the millions of salmon and steelhead reared at the hatchery help "mitigate" the impact of the dam. In other words, the dam kills big fish, and the hatchery tries to compensate by putting young fingerlings (fish at least one inch long) back in the Columbia and tributaries further upstream.

Like many other dams on salmon rivers, Bonneville is equipped with fish ladders, a series of stair-step pools that give adult fish a fighting chance to get past the dam and reach their spawning grounds. Despite this lift, it's estimated that almost 20 percent of salmon and steelhead in this stretch of the Columbia die before they reach their destination -- and that doesn't count the ones caught by fisherman.
(bluefish: this mortality estimate seems high see survival.htm)

Some fish miss the ladders and get whacked by turbines (bluefish: presumably the author is referring to 'fallback' which is when an adult climbs a ladder but mistakenly is pulled into the turbine intake of the same dam), some get fatally stressed out as they try to climb the ladders, and many thousands get eaten by sea lions who have discovered easy pickings in the fish jams immediately below the dam, AKA "The Bonneville Buffet." The dam is 145 river miles away from the ocean, but for hungry sea lions, Bonneville is definitely worth the trip.

The ladders on both the Washington and Oregon sides of the dam give visitors an excellent chance to see wild salmon and steelhead in action. You can stand on an outside platform to watch the fish fight the current, or you can go inside to watch the fish pass by large viewing windows. It's like a cool aquarium exhibit with a constantly rotating cast.

To give yourself the best chance to see some wild fish, visit the dam between April and November; with luck, the ladders will be crowded. In 2009, more than 480,000 adult chinook salmon and 600,000 steelhead trout passed through the dam.

Watching fish through the window, you can't help but root for them to make it as far as they need to go. If they've already come this far, they just might have a chance.

Related Pages:
Oregon's Bonneville Hatchery by Chris Woolston, VIA Magazine, 11-12/11

Chris Woolston
Bonneville Dam Fish Ladders: Once a Spawn a Time
VIA Magazine, October 20, 2011

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