A never-before-seen bacteria has killed over 60,000 fish in California

VICTORVILLE — As coronavirus infections and deaths continue to rise throughout the United States, state officials are fighting a battle against a separate outbreak that has killed up to 60,000 fish at the Mojave River Hatchery.

The culprit, a bacteria known as Lactococcus garvieae, has never before been seen in the state until it was detected at the Victorville facility in April, said Jay Rowan, an environmental program manager of the California Department of Fish and Wildlife.

Since then, the bacteria has been detected at two other state fish hatcheries, both in the Owens Valley. About 3 million rainbow trout, cutthroat trout, brown trout and other species remain in quarantine as scientists try to understand a novel pathogen that, so far, has resisted treatments to cure it.

“The thing that makes it so bad is that it’s new to California,” Rowan said. “We don’t know that it exists out in the wild.”

When asked about the comparison with COVID-19, Rowan said “the parallels are a little weird.”

One parallel is that fish can be infected with L. garvieae but show no symptoms.

Signs of the disease include bulging eyes, lethargic or erratic swimming, darkening of the skin and a swollen abdomen. While rare, fish-to-human infections have also been known to occur.

According to the CDFW, scientists have found infected fish are more likely to be symptomatic and die at water temperatures of 59 degrees Fahrenheit or above, among other factors.

Rowan said this likely explained why the mortality rate at the Mojave River Hatchery was significantly higher than the two facilities farther north — Black Rock Hatchery and Fish Springs Hatchery — where almost no fish have died due to the bacteria.

All three facilities are fed by groundwater, which is typically warmer in the High Desert. Plus, Rowan said, more fish are dying at the lower ends of raceways — artificial channels where the trout are raised — where the sun shines more intensely.

On June 30, the CDFW said about 50,000 of the 860,000 rainbow trout housed at Mojave River had died. That death toll has increased by another 10,000 as of Tuesday, according to Rowan.

And despite officials’ treating the fish, the trout continue to succumb.

Hatchery staff at the Mojave River Hatchery, which is located on Victor Valley College’s lower campus, have fed the fish antibiotic feed at a cost of more than $75,000, but the CDFW said the bacteria was still present.

“Honestly, we’re learning new things about this every single day,” Rowan said.

In the United States, he said L. garvieae has only been found in aquaculture facilities in three other states making it more of a challenge to combat it because there aren’t “tried-and-true strategies.”

On top of that, fish pathologists still don’t know where the bacteria came from in the first place.

Rowan said he didn’t want to speculate on what the next course of action would be if the treatments don’t work. Department officials have suggested euthanizing healthy fish if it is determined the bacteria doesn’t exist naturally in the wild.

Stocking of natural waterways in at least five Southern California counties is unlikely to happen from the quarantined facilities this year, CDFW officials said, so as not to spread the disease to other animals.

If euthanization of all the fish at Mojave River Hatchery occurs, they say catchable fish wouldn’t be ready until December or January of 2021. CDFW said based on previous experience in having to depopulate hatcheries, it could take up to three years before Victorville’s is back up to “pre-depopulation production levels.