After four dams were removed on the Klamath River – the largest dam removal operation in history – those pushing for the rehabilitation of this important salmon river have largely been holding their breath. The hope was that chinook salmon would reclaim their historical native range throughout the Klamath River Basin, restoring a run of fish that somehow hasn’t completely disappeared, back to its former glory.
According to a new study published in Nature, the king salmon haven’t just started coming back to the Klamath – they’re thriving.
The study’s abstract states that between 2024 and 2025, the chinook that returned to the Klamath have been documented in 88% of their historical native range. This includes not only the main stem of the upper reaches of the Klamath, which have been blocked by dams, but also the countless tributaries and feeder streams where much of the spawning actually happens.
Quickly returning
“Recolonization required fish to swim through dam removal sites, complex hydraulic corridors and engineered fishways, demonstrating the propensity for rapid recolonization at basin scale despite these challenges,” the study says. “These findings provide the first quantitative assessment of salmon response to the world’s largest dam removal and demonstrate how reconnection can catalyze large-scale recolonization in historically fragmented river networks.”
In plain English, that means the chinook have come back to their historical native range at a pace far quicker than what was anticipated. It also shows that, if given the opportunity, endangered anadromous fish like salmon and steelhead can quickly regain their footing in the natural world. It’s hoped that the Klamath River’s success story could lead to other large-scale salmon and steelhead restoration efforts throughout the Pacific Northwest.
Nearly gone
The chinook salmon in the Klamath very nearly didn’t survive the dams. The study goes into great detail on the impact of dams, as well as the impact of habitat restoration.
For more than a century, dams, over-harvest, and overuse of water had diminished the population of chinook salmon by over 90%. On top of that, the spring-run chinook salmon disappeared completely off the landscape. These fish also faced serious threats from disease, linked directly to changing hydrology based on dam release, low flows, and warming water temperatures. In fact, over 33,000 king salmon died in 2002 before being able to spawn due to that combination of factors.
Success
Dam removal was completed in 2024, and only two years later, we’re already seeing fish back in 88% of their historical native range. If these trends continue, chinook salmon in the Klamath should be well on their way to persisting on the landscape for many more years.