Since 2024, CalTrout and our partners have been building a clearer picture of how the Klamath River is responding to the removal of four dams — J.C. Boyle, Copco 1, Copco 2, and Iron Gate — the largest dam removal project in the world, through the Klamath River Monitoring Program. Bringing together tribes, government agencies, universities, and non-profits, the project team is tracking how salmon and steelhead are finding and using more than 400 miles of habitat that had been largely inaccessible for over a century.

How many fish are moving into the newly accessible river? When are they arriving? Where do they go once they get there? To answer these questions, the team combines several tools that work together to follow the fish across the watershed. High-resolution imaging sonar, enhanced by AI technology developed through the Fisheye Project with Caltech, MIT, and UMass Amherst, offers a continuous, highly accurate view of fish passing through turbid water. Netting captures information on species, age, length, and genetics, and allows researchers to tag fish for tracking. Radio telemetry follows tagged fish as they migrate upstream, and spawner surveys pinpoint where fish are building nests, revealing which reaches of river they've chosen to call home. A parallel effort focused on steelhead adds another layer to the picture: trained anglers collect scale samples, tissue samples, and field observations, extending the reach of formal monitoring and helping researchers understand how quickly steelhead recolonize newly opened habitat, what role resident rainbow trout play in rebuilding the population, and how the species' genetic diversity is shifting with restored connectivity.

Together, these methods let the team follow salmon and steelhead every step of the way, and the results so far have exceeded expectations. Within just two migratory seasons, Chinook salmon reoccupied 88% of their documented historical range, reclaiming 214 miles of river and tributaries. Returns nearly doubled year over year, from about 7,742 fish passing the former Iron Gate site in fall 2024 to roughly 13,310 in fall 2025. Fish were documented as far upstream as Beatty Gap on the Sprague River, over 360 river miles from the ocean, the farthest upstream record ever recorded on the Klamath.

This monitoring work is building the evidence base needed to understand how fish are responding to one of the largest river restoration efforts ever undertaken, and to guide where future restoration work can have the greatest impact. Findings continue to be published as the story unfolds: a 2025 report detailed results from the first year of sonar monitoring, a steelhead-focused report published in mid-2026 laid out a biology-driven framework for tracking long-term recovery, and an August 2026 study led by CalTrout's Damon Goodman, in Scientific Reports, part of the Nature portfolio of journals, documented the rapid Chinook salmon recolonization described above.