What in Klamath River waters is making juvenile salmon sick?

New salmon populations living in the Klamath River face sickness and low water levels due to diminished snowpack less than two years after the Klamath Dam removal, the Karuk Tribe said in a June report on the river's health.

Scientists monitoring the Klamath's waters found rising levels of a fish parasite called Ceratonova shasta, according to the report. Most juvenile salmon, which are especially susceptible to disease caused by the parasite, migrated out to sea in early spring 2026 - before the disease spread to high levels, said Toz Soto, the tribe's senior biologist.

Soto said it's possible most of the sick and dying fish came from the same hatchery.

While the dam's removal "remains a historic and necessary step toward salmon recovery," surveys of the river show it's "still in the early stages of healing," the tribe said in the report.

There are signs the river is recovering since construction crews removed the last of four dams in October 2024. According to the report, issued by Craig Tucker, the tribe's natural resources policy consultant, adult salmon have since been returning to the river, and juvenile salmon are migrating out from parts of the Klamath that hadn't had a salmon living in them for a century.

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Juvenile salmon sickness related to warm spring and low mountain snowpack

It was a tough winter and spring for the salmon so far, the tribe said in the report.

The California Department of Water Resources reported in April that Northern California's mountain snow levels were almost nil. Spring temperatures were warmer than usual and much of the snow melted early due to warm spring rain.

Warm temperatures and little snowpack melting into the Klamath creates conditions that cause stress to salmon, especially juveniles. It can leave them more vulnerable to diseases, the tribe's report said, because melt water helps clean parasites out of the river.

That doesn't mean removing the dam wasn't successful, tribal scientists said.

"…No one should confuse dam removal with an instant cure. The river was damaged for more than a century. It will take time, strong winter flows, habitat restoration, and continued care to bring it back to health," said Karuk Vice Chairman Kenneth Brink in the report.

Soto said the parasite shows up periodically in the Klamath River, especially when water flow is low.

"One good year or one bad year will not define the future of this river," Soto said. "What we need now are several winters with strong flushing flows, continued habitat restoration, and careful monitoring so the river can rebuild the natural functions that salmon depend on."

Jessica Skropanic is a features reporter for the Record Searchlight/USA Today Network. She covers science, arts, social issues and news stories. Follow her on Twitter @RS_JSkropanic and on Facebook. Join Jessica on Record Searchlight Facebook groups Get Out! Nor Cal, Today in Shasta County and Shaping Redding's Future. To support and sustain this work, please subscribe today. Thank you.

This article originally appeared on Redding Record Searchlight: What in Klamath River waters is making juvenile salmon sick?

Reporting by Jessica Skropanic, Redding Record Searchlight / Redding Record Searchlight

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This story was originally published June 23, 2026 at 2:08 AM.