Friday August 28, 2026
CalTrout —
Less than two years ago, four dams on the Klamath River were removed. This week, the first peer-reviewed science is out — published in Scientific Reports, part of the renowned Nature portfolio of journals — confirming that Chinook salmon reoccupied 88% of their historical range within just two migratory seasons. Chinook salmon didn’t just trickle back into reconnected habitat in the upper Klamath Basin. They surged.
The study, led by CalTrout’s Shasta Cascade Regional Director Damon Goodman alongside partners from the Karuk Tribe, Klamath Tribes, Yurok Tribe, Oregon Department of Fish and Wildlife, California Department of Fish and Wildlife, NOAA, USGS, CalPoly Humboldt, and independent researchers, is the first published quantitative assessment of how salmon have responded to the removal of J.C. Boyle, Copco 1, Copco 2, and Iron Gate dams — the largest dam removal project ever completed.
Using high-resolution imaging sonar stationed near the former Iron Gate Dam site, the team counted salmon swimming upstream into water they hadn’t been able to reach in over a century. In fall 2024, the first salmon migration season after the dams came out, an estimated 7,742 Chinook salmon passed the site — about 18% of all the Chinook that returned to the entire Klamath Basin that year. The following year, fall 2025, that number nearly doubled to 13,310, or roughly 19% of the basin-wide return.