The Klamath River runs through Oregon and California in the US. Dams blocked Chinook salmon for about a century. Their numbers fell by about 90%. Workers removed four dams in 2024.
Soon afterwards, 7,742 salmon swam past the old dam sites. In 2025, more than 13,000 did this. The fish returned to 345 kilometres of river. They reached 88% of their known old homes. Scientists expected their return, but its speed surprised them.
Scientists counted fish with an underwater camera. It uses sound, so it works in muddy water. But the fish still face problems. To reach their old numbers, they need to have young successfully over many years. They also need better water, better places to live and easier routes through the river.
