The California Department of Fish and Wildlife (CDFW) announced that about 830,000 fall-run chinook salmon fry released from its Fall Creek Fish Hatchery in Siskiyou County are presumed to have succumbed to gas bubble disease in the Klamath River.
On Feb. 26, CDFW released the fry into Fall Creek, a tributary of the Klamath River above Iron Gate Dam. The fish were hatched at CDFW’s new, $35 million Fall Creek Fish Hatchery, which represents California’s long-term commitment to supporting and restoring chinook and coho salmon runs on an undammed Klamath River.
The salmon fry experienced large mortality, based on monitoring data downstream. Indications are the cause of mortality is gas bubble disease that likely occurred as the fry migrated though the Iron Gate Dam tunnel, old infrastructure that is targeted for removal along with Iron Gate Dam later this year. Gas bubble disease results from environmental or physical trauma often associated with severe pressure change. There is no indication the mortality is associated with other Klamath River water quality conditions such as turbidity and dissolved oxygen, which were reading at suitable levels before release, CDFW said. Monitoring equipment documented other healthy yearling coho and chinook salmon that came from downstream of the dam.
In January, Hydro Review reported that the Klamath River Renewal Corporation (KRRC) initiated the drawdown process by opening the low-level outlet tunnel in Iron Gate Dam. Draining the reservoirs is the first step toward removal of the three remaining hydroelectric projects. Drawdown of the JC Boyle and Copco reservoirs was scheduled to begin later in January, and all reservoirs were expected to be drained by the end of February, KRRC said.
The three dams, along with Copco No. 2 dam that was removed in 2023, comprise the Lower Klamath Hydropower Project, which occupies about 400 acres of federal land on the California-Oregon border administered by the U.S. Department of Interior, Bureau of Land Management.
The strategy for removing Iron Gate was different in that “there was no blast at this dam, instead we had the opportunity to use existing infrastructure, which allows us to precisely control the volume of water going down river, limiting downstream impacts,” said Mark Bransom, chief executive officer of KRRC.
KRRC’s Aquatic Resources Working Group carefully selected the initial drawdown period. January and February are the ideal months, as there are the fewest threatened and endangered species in the mainstem and winter flows will assist with sediment evacuation, they said.
The problems associated with the Iron Gate Dam tunnel are temporary, CDFW said. CDFW will plan all future salmon releases below Iron Gate Dam until this infrastructure is 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, according to a release. CDFW’s Fall Creek Fish Hatchery continues to hold about 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 – 1.25 million released as fry, 1.75 million as smolts, and 250,000 as yearlings.
