In the 1960s, two large dams went up on the Cowlitz and shut salmon out of the entire upper half of the basin. By the logic of every other case on this site, the runs should have cratered.
Instead, the Cowlitz is one of the most productive salmon and steelhead fisheries in Washington. Not because the fish adapted, and not because anyone waited — but because the dam owner was made to run one of the largest active-production operations in the state, and it works.
Mayfield Dam (1963) and Mossyrock Dam (1968), built by Tacoma Power, walled anadromous fish out of the upper Cowlitz, the Cispus, and the Tilton — a huge share of the watershed's spawning habitat, gone behind two tall dams that fish can't climb. In most of our case studies, that's the beginning of a collapse. Here it was the beginning of a mitigation program built to a genuinely industrial scale.
Tacoma Power funds and WDFW operates a hatchery system (rebuilt and consolidated in 2010) that releases on the order of 7.5 million spring Chinook, fall Chinook, and coho every year.
Juvenile and adult fish are collected and trucked around the dams — up to the Tilton, Cowlitz, and Cispus — reopening the upper basin to salmon for the first time since the 1960s.
The whole effort is a condition of the dams' federal license — the operator paying to actively produce and move fish, rather than letting the runs simply blink out behind the concrete.
Strip away the details and the Cowlitz makes a blunt point: where dams block a huge share of a basin, active production can keep a major run — and a major fishery — alive anyway. The passive alternative was never "the fish recover on their own"; there is no upstream habitat to recover into. The alternative was near-zero. Instead, a heavily-fished, year-round fishery persists, and salmon are being put back into the upper basin by truck. That is human intervention doing exactly what the hands-off approach cannot: replacing production that a barrier destroyed.
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The Cowlitz leans heavily on hatchery production, and that's a real limitation, not a bragging point. A run kept alive mostly by 7.5 million released smolts is not the same as a self-sustaining wild run, and the honest goal is to grow the natural, upper-basin component over time so it isn't purely a put-and-take system. Done poorly, large hatchery programs carry genuine genetic and ecological risks, and the Cowlitz has to keep managing those.
But the baseline comparison is stark. Behind two impassable dams, the choice wasn't wild-versus-hatchery — it was active production versus almost nothing. Keeping a major run and fishery alive, and rebuilding the upper basin by hand, beats watching it disappear.
The figures on this page are drawn from public, authoritative records:
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