CALIFORNIA— Multiple fish hatcheries across the eastern Sierra and Southern California are battling a bacterial outbreak threatening the hatcheries wild fish populations, according to a statement by the California Department of Fish and Wildlife made on June 30.

The bacteria, Lactococcus garvieae, has sickened fish at the Mojave River Hatchery and been detected at the Black Rock and Fish Spring hatcheries. The bacteria increases the mortality of fish. Symptoms include bulging eyes and lethargic or erratic swimming. The CDFW has also said fish exhibit no symptoms due to several factors such as stress or water temperature.

The Mojave River Hatchery contains approximately 860,000 rainbow trout, of which 10 of 16 groups of the trout are infected. Although chances of fish to human transmission of this virus are very low, the CDFW has halted fish stocking (the process of releasing raised fish into the wild) temporarily. Once fish have recovered from the infection and pathologists determine there is no threat to the environment or other wild fish populations, fish stocking will resume.

Eight waterways in San Bernardino, two in San Diego, and one in Los Angeles and Riverside will not be receiving scheduled fish plants between now and October. Environmental program manager Jay Rowan for the CDFW’s hatcheries said,

“This is a challenge for our hatcheries because the bacteria is previously unknown in California, and we don’t have tried-and-true strategies on hand to combat it.”

Rowan also broke down the CDFW’s bacterial outbreak response plan into three components: treating the affected fish, finding the outbreak’s origin, and planning to contain and prevent the future spread of bacteria.

“Unfortunately, we may be in for a long battle here, which means there will not be a lot of fish plants in the near future in the eastern Sierra and Southern California. I wish we could give anglers a target date for when we think we can start planting again, but it’s all up to how fast and how well the fish respond to the treatments,” Rowan added.

Currently, the CDFW’s treatment measures include low water temperatures, reducing stress-induced activities such as overcrowding, and introducing antibiotic medication and a special diet. The cost of antibiotic feed for the Mojave River Hatchery has so far exceeded $75,000 and the CDFW expects to spend several hundred thousand dollars throughout the entire treatment process.

If treatment is unsuccessful, the CDFW has presented two options that center on testing wild fish populations for the bacteria. If L. garvieae is widespread in wild fish populations, fish can still eventually be released. If the bacteria is not present in fish populations and treatment is not successful, the infected fish in hatcheries will have to be euthanized. It has previously taken hatcheries up to three years to return to previous production levels after depopulation.

The CDFW is currently investigating the outbreak’s cause and monitoring other fish hatcheries for an L. garvieae outbreak.