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

via cbsnews.com

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.

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.”