Over 800,000 salmon suddenly die in California river. ‘Gas bubble disease’ is to blame

Hundreds of thousands of newly hatched salmon released into the Klamath River died passing through a dam due to be demolished, California wildlife officials reported.

The 830,000 fish likely perished from “gas bubble disease,” caused by severe changes in water pressure, the California Department of Fish and Wildlife said in a March 2 news release.

The salmon died while passing through a tunnel associated with the Iron Gate Dam, officials said. The dam and tunnel are scheduled to be removed later this year.

The fish were part of a Feb. 26 release of Chinook salmon fry into Fall Creek, which flows into the Klamath River, from a new $35 million fish hatchery, officials said.

The project is part of an effort to restore Chinook and coho salmon runs on the Klamath River following the removal of several dams, the agency said.

Scientists found no evidence the salmon died because of oxygen levels or higher levels of particles in the river, and the dead fish showed signs of gas bubble disease, officials said.

“The problems associated with the Iron Gate Dam tunnel are temporary and yet another sad reminder of how the Klamath River dams have harmed salmon runs for generations,” the agency said in the release.

Future releases will take place below the dam until it is removed, officials said. In all, the state plans to release 3.25 million salmon into the Klamath River in 2024.

Additional salmon are being raised at the hatchery to replace those killed in the February release.

The Klamath River is about 300 miles north of Sacramento, near the Oregon border.

This story was originally published March 4, 2024 at 7:19 AM with the headline "Over 800,000 salmon suddenly die in California river. ‘Gas bubble disease’ is to blame."