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Deadly Parasite Invades Upper Klamath, Threatens Salmon
13 Jun
Summary
- A lethal waterborne parasite, Ceratonova shasta, is rapidly spreading in the Upper Klamath River.
- Nearly half of tested juvenile Chinook salmon showed infection, with one-fifth carrying lethal levels.
- Dam removals were expected to improve conditions, but warm temperatures are fueling parasite growth.
Scientists are closely monitoring a dangerous waterborne parasite, Ceratonova shasta, as it rapidly expands its presence in the Upper Klamath River. This parasite, previously a major concern in the Lower Klamath Basin, has now been detected in alarming numbers in juvenile Chinook salmon in Oregon for the first time since the removal of four hydroelectric dams earlier in 2024. Despite expectations that dam removal would improve river conditions and curb disease, persistent drought and unusually warm water temperatures have created a perfect storm for the parasite.
Recent testing between mid-March and mid-May indicated that 46% of nearly 700 juvenile Chinook salmon in the Upper Klamath River were infected. Worryingly, about one-fifth of these carried lethal levels of the parasite. This rapid spread into new areas is particularly concerning for endangered salmon runs, which scientists previously believed would be better protected after dam removals allowed fish greater access upstream. Researchers are now studying the dead fish to better understand the parasite's impact and its relationship with rising river temperatures.
