The Klamath River salmon die-off was tragic. Was it predictable?


recent large die-off of young salmon released into the Klamath River shocked and dismayed state biologists, reinforcing that human efforts to restore nature and undo damage can be unpredictable and difficult  to control. 

The tiny Chinook salmon turned up dead downriver just two days after they were released from the California Department of Fish and Wildlife’s brand new Fall Creek Fish Hatchery, built to supply the Klamath River as it undergoes the largest dam removal in history.  

The $35 million state hatchery, on a tributary just upstream of Iron Gate dam in Siskiyou County, was constructed to help the river’s threatened coho and dwindling fall-run chinook salmon, a mainstay of commercial and recreational fishing and tribal food supplies.

The hatchery’s first release ended with an unknown number of the 830,000 young Chinook salmon found dead, their eyes bulging, in a federal sampling trap about 9 miles below the dam.

State officials called it “a large mortality,” but said there’s no official count yet and released no additional details about the size of the die-off.

California’s fish and wildlife officials said they suspect “gas bubble disease,” a condition similar to decompression sickness in scuba divers, is to blame — likely caused when the salmon traveled through a 9-foot-wide tunnel out of Iron Gate dam to reconnect with the Klamath downriver. 

Gas bubble disease in fish is caused by “environmental or physical trauma often associated with severe pressure change,” officials said.

Jason Roberts, inland fisheries program manager with the state agency, said it’s an outcome that state, federal, and tribal scientists involved in the decision didn’t anticipate.

“The basin co-managers made the best decision they could with the information that they had, and unfortunately, it did not go well,” Roberts said. “I don’t think anyone thought water going through this tunnel would cause gas bubble disease, or we obviously wouldn’t have done it.”

“You see gas bubble disease at hatcheries when there’s flood flows and there’s tons of water,” he added. “I think everyone assumed, given Iron Gate reservoir was basically drained, that there wouldn’t be a problem.”

It was a tragic, heartbreaking event for the fish biologists and a setback for a costly and high-profile project: The state had hatched and raised the salmon, then released them into a place where they died almost immediately. 

“I feel really bad for the fish. And I feel really bad for my staff that spend all their time taking care of these fish, and for all the partners and stakeholders that are counting on us,” Roberts said.