Historic California dam removal, meant to help salmon, sees massive die-off

San Francisco Chronicle . March 3, 2024

Hundreds of thousands of young salmon are believed to have died this week at the site of a historic dam removal project on the Klamath River, after an effort to restore salmon runs on the newly unconstrained river went awry, the Chronicle has learned.

The dead chinook salmon were among the first hatchery fish released on the Klamath since four hydroelectric dams were breached near the California-Oregon border, to allow the river to flow freely again and ultimately help fish flourish. One of the dams has been fully removed, and the three others are scheduled to come out later this year.

The salmon die-off, discovered downstream of the 173-foot Iron Gate Dam, is thought to be the result of trauma the small fish experienced when they went through a tunnel at the dam’s base, which had been opened to allow the river to pass and dam demolition to proceed. Water pressure in the outlet tunnel was presumably too great, causing the fish to die of what appears to be gas bubble disease, California officials told the Chronicle.

“No one, especially those in my program who work night and day to keep fish alive, wants to see something like this happen,” said Jason Roberts, an environmental program manager for the California Department of Fish and Wildlife. “We’re going to learn from it. We need to do better.”

Link (paywall): https://www.sfchronicle.com/california/article/klamath-dams-salmon-die-off-18700078.php

According to the link, about 830,000 hatchery-raised chinook were released. Each was roughly 1 to 2 inches long, the majority of which died or probably soon will.

Excellent intention, nightmare result.