Bacterial outbreak forces state to euthanize hatchery fish

Trout at three hatcheries in Southern California and Eastern Sierras were given a death sentence to prevent a spread of infection.

SACRAMENTO—A small corner of the fish world was on the verge of experiencing a localized pandemic of its own – as if the worldwide spread of Coronavirus amongst humans (and the associated political discourse) hasn’t dominated headlines in this publication (and others).

The California Department of Fish and Wildlife (CDFW) announced they euthanized trout at three fish hatcheries in Southern California and the Eastern Sierras. State officials decided to euthanize the trout after a bacterial outbreak affected 3.2 million fish, it was announced on July 20.

Mojave River Hatchery, Black Rock Hatchery and Fish Springs Hatchery were the three hatcheries where fish were euthanized. The hatcheries provide fish to CDFW’s South Coast and Inland Desert regions.

CDFW staff said its action would “have a profound effect on CDFW’s ability to stock fish for anglers in [Southern California and Inland Desert] regions in the near future.”

“Euthanizing our hatchery stocks was not a decision we came to lightly, but it had to be done,” Jay Rowan, an environmental program manager for CDFW hatcheries, said in a released statement. “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.”

The three hatcheries were placed under quarantine for more than one month, allowing pathologists and hatchery staff to conduct tests and research potential treatment options.

“The outbreak of Lactococcus garvieae, which is similar to streptococcus, has been reported in cattle and poultry farms as well as fresh and saltwater fish and shellfish hatcheries around the world, but had never before been detected in fish in California,” CDFW staff said. “Research of treatment options employed at trout farms in Europe and other parts of the world show there is almost no chance for successfully eliminating the bacteria from a facility without depopulation and disinfection.”

Common symptoms affiliated with L. garvieae include bulging eyes, lethargic/erratic swimming and increased mortality. Fish can also be asymptomatic and show no signed of infection, depending upon water temperature and stress, according to CDFW staff.

“Fish-to-human transmission of this bacteria is rare and unlikely but there are several documented instances associated with immunocompromised people consuming infected raw fish and unpasteurized milk products,” CDFW staff stated.

Eastern Sierra’s Hot Creek Hatchery has tested negative for L. garvieae and is still providing plants for eight waterways in Inyo and Mono counties, according to CDFW staff.

“CDFW is in the process of developing a modified stocking plan to reallocate fish from central and northern California hatcheries to a small number of high angler use, easily accessible waters in geographically distinct parts of the eastern Sierra and Southern California,” CDFW staff stated.

Anyone who has questions about L. garvieae can reach out to CDFW staff via email at hatcherybackteriainfo@wildlife.ca.gov.

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