For the past few months some of the trout hatcheries in California have been experiencing a bacteria outbreak that is negatively affecting their fish populations. The bacteria (Lactococcus garvieae) has been detected in freshwater and saltwater aquaculture facilities around the world, but this is the first time it has been observed in California. According to the California Department of Fish and Wildlife (CDFW), fish infected with Lactococcus garvieae “can show symptoms including bulging eyes, lethargic or erratic swimming and increased mortality, or be asymptomatic and show no signs of infection depending on a several factors including water temperature and stress.” 

Rainbow trout with bacteria infection
Courtesy of HIPRA

Hatcheries including the Mojave River Hatchery, the Black Rock Hatchery, and the Fish Springs Hatchery have spent the past few months working with fish pathology experts and experimenting with different treatments in order to get their trout back to good health. After months of trial and error, the CDFW has made the difficult decision to euthanize all the trout at the affected facilities in order to stop the spread of the outbreak.

Dead trout
Courtesy of California Department of Fish & Wildlife

Jay Rowan, environmental program manager for CDFW hatcheries, stated, “Euthanizing our hatchery stocks was not a decision we came to lightly, but it had to be done.This bacterium is resistant to all the treatment options we have available for fish. The fish losses were getting worse despite our treatments. The best option we have available that will get us back to planting fish from these hatcheries in the shortest timeline is to clear the raceways, thoroughly disinfect the facilities, and start over.”

Courtesy of California Department of Fish & Wildlife Badge
Courtesy of California Department of Fish & Wildlife

While depopulating these hatcheries is the best decision, this action comes with major issues. It is not certain when these hatcheries will be able to stock natural streams once again. It may be well into next year before these facilities can get back on track. Until then, CDFW is in the process of modifying their stocking plan to reallocate fish from central and northern California hatcheries to a small number of easily accessible waters in parts of the eastern Sierra and Southern California.

Young kid holding a large rainbow trout
Courtesy of California Department of Fish & Wildlife

For additional information, please see CDFW’s frequently asked questions about the L. garvieae outbreak. Also, members of the public can email questions to

Article written by Flylords Content Team Member Andrew Braker.


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