Wednesday June 3, 2026
Active NorCal —
The first detailed health data on juvenile salmon in the post-dam Klamath River is in, and the numbers are concerning.
A June 1 memo from the U.S. Fish and Wildlife Service’s California-Nevada Fish Health Center reports that 46% of young Chinook salmon tested in the upper Klamath River are infected with Ceratonova shasta, a waterborne parasite that can be fatal to juvenile fish. Of those infected, 18% carry parasite loads at levels associated with mortality. That is a significant jump from 2025, when 22% of fish tested positive and none carried lethal-level infections.
The testing covered 696 fish collected between March 17 and May 12 from three reaches of the upper river, from the Oregon state line down to the Scott River. The first detection occurred on April 2. By late April, infection rates in some reaches had climbed to 93% and 100% of fish sampled.
A new rotary screw trap was installed at the site of the former Iron Gate Dam, marking the first time biologists have been able to monitor fish health at a location that was underwater behind a dam for over a century.