Removal of four dams from a north American river has led to such large runs of salmon that they have exceeded researcher expectations.
The findings published in the journal Scientific Reports say that thousands of chinook salmon have been recorded in the Klamath river after the last of four dams was removed in 2024.
The Klamath river flows about 260 miles through Oregon and California, and was spanned by four major hydroelectric dams for many decades.
The last dam was removed after many years of lobbying, but early reports gave no indication as to whether the fish would return.
Over 7,700 adult chinook salmon swam through after the last dam removal, and the number increased by about 72 per cent in the headwaters of the river the following year.
Coho salmon, steelhead trout and Pacific lamprey, all species important for indigenous subsistence fishing, also migrated upstream.
“I don’t think any of us, in our wildest dreams, expected this many fish this quickly to repatriate that area,” Keith Parker, a senior fisheries biologist and member of the Yurok Tribe, which led the decades-long campaign to have the dams removed, told The New York Times.
“Recovery takes time,” Damon Goodman, a fish biologist with the conservation organization California Trout who led the report said.
“We’re not there yet. But the signs are good,”he said.
To estimate how many fish were chinook, the researchers used sonar to count fish passing the former Iron Gate Dam site, supplemented by video monitoring and surveys of live salmon and carcasses.
