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Almost a million young salmon released in Klamath River die from gas bubble disease

Chinook salmon swimming tribe's ancestral McCloud River for first time in decades
Chinook salmon swimming tribe's ancestral McCloud River for first time in decades 04:37

YREKA -- The California Department of Fish and Wildlife (CDFW) said Saturday that 830,000 Chinook salmon fry, released from its Fall Creek Fish Hatchery in Siskiyou County, are presumed to have died due to gas bubble disease in the Klamath River.

On Monday, CDFW released the fish into Fall Creek, a tributary of the Klamath River above Iron Gate Dam.

The fish were hatched at CDFW's new, $35 million, state-of-the-art hatchery, which CDFW said represents California's long-term commitment to supporting and restoring both Chinook and coho salmon runs on an undammed Klamath River.

Chinook Salmon
Spring Chinook salmon in an undated photo. Michael Humling via Bay City News

The salmon experienced a large mortality based on monitoring data downstream. CDFW said in a statement there are indications the fish were killed by gas bubble disease that likely occurred as they migrated though the Iron Gate Dam tunnel, old infrastructure that is targeted for removal along with the Iron Gate Dam itself later this year.

Gas bubble disease results from environmental or physical trauma often associated with severe pressure change.

The CDFW said there's no indication the deaths are associated with other Klamath River water quality conditions, such as turbidity and dissolved oxygen, which were reading at suitable levels on Feb. 26 and the days prior to release.

The visual appearance of the dead fry detected by monitoring equipment points to gas bubble disease, the agency said. Monitoring equipment documented other healthy yearling coho and Chinook salmon that came from downstream of the dam.

CDFW 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."

Fall Run Chinook Salmon Fry
Juvenile Chinook salmon swim in a raceway at Iron Fish Gate Hatchery, Siskiyou County before their relocation to the Fall Creek facility on July 7, 2021.  CDFW Photo by Travis VanZant

CDFW said it will plan all future salmon releases below Iron Gate Dam until it's removed.

"Poor habitat conditions caused by the dams and other circumstances such as this are reasons why CDFW conducts releases of hatchery fish at various life stages," CDFW said.

CDFW's Fall Creek Fish Hatchery continues to hold approximately 3.27 million healthy, fall-run Chinook salmon. Additional releases are planned later in the month.

The annual fall-run Chinook salmon production goal for the hatchery is to raise and release 3.25 million fish. The additional Chinook salmon remaining in the hatchery exceeds the annual production goal and will help offset losses experienced with the initial release of fry.

The state has been ramping up its efforts to facilitate the recovery of the salmon population in California.

Earlier this year, California Gov. Gavin Newsom pledged to fast-track more than half a dozen projects by the end of his term to remove or bypass dams that have blocked salmon from returning to the state's chilly mountain streams and acting as the keystone of a complex ecosystem that sustains both economies and spiritual beliefs for tribes.  

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