For decades, the Klamath River in southern Oregon and northern California bore the burden of four large dams built in the twentieth century. These structures blocked the path of the Chinook salmon — the king of salmon — whose populations in the basin had declined by roughly ninety percent. It seemed that the historical spawning grounds would remain inaccessible forever. However, in 2024 the dams were dismantled, and already that same year 7742 individuals made their way upriver, and in 2025 — more than thirteen thousand.
A study published in the journal Scientific Reports showed that the fish quickly colonized 345 kilometers of the previously blocked channel — that amounts to about eighty-eight percent of the known historical habitats. The scientists used a special hydroacoustic camera capable of "seeing" through murky water even in complete darkness. This method made it possible to accurately count migrating individuals and to distinguish Chinook salmon from other species.
The speed of the return surprised even the authors of the study. According to lead researcher Damon Goodman, the fish overcame rapids, artificial fish passage structures and a former lake to reach places that had been inaccessible for more than a century. This suggests that the species has retained an innate ability to find and use new stretches of the river as soon as the barriers disappear.
At the same time, full recovery of the population will require more than one generation of successful spawning. It is necessary to improve water quality, ensure free passage through the entire basin and preserve suitable conditions for the young. The dismantling of the dams was an important step, but it does not remove all the threats that the Chinook salmon faces in a changing climate and under growing anthropogenic pressure.
Such examples show how closely human engineering decisions and the natural migration routes of fish are intertwined. When barriers are removed, the ecosystem is capable of responding with surprising speed, restoring a balance that seemed lost forever.
Observations on the Klamath confirm: restoring river corridors gives a real chance to species whose populations were on the brink. The main thing is to continue monitoring and to maintain the conditions under which the fish can not only return but also establish themselves in new territories.
