Three years ago, Mono County saw a disease breakout in fish hatcheries, and for that entire year the Eastern Sierra saw hardly any stocked fish – and the fish they did see were from other hatcheries around the state that were brought in. 

The California Department of Fish and Wildlife (CDFW) had to euthanize 3.2 million fish that year in order to stop the spread of the disease. 

The following year, CDFW was only able to stock smaller fish in the area.

Unfortunately, this year, fish in two local hatcheries just tested positive for Lactococcus petauri, a naturally occurring bacterium similar to Streptococcus (strep throat), that sickens fish. 

The affected facilities -Black Rock Hatchery and Fish Springs Hatchery- usually provide fish for stocking waterways in CDFW’s Inland Deserts Region.

Approximately 120,000 trout at Black Rock Hatchery, which would normally be stocked throughout the fishing season, have tested positive for the disease. At Fish Springs Hatchery, approximately 550,000 trout tested positive. 

The news comes on the eve of this Saturday’s trout fishing opener

The hatcheries were able to develop a vaccine for these fish about a year and a half ago, and have administered it to them. The current outbreak is among fish that have already received one round of vaccination.

The hatcheries’ plan for this upcoming fish season: if the fish are not presenting any symptoms, they will stock those fish in “all hydrologically-connected waters to their hatcheries that are cold.” This includes anything south of Deadman Summit in Mono and Inyo Counties; anything north of that boundary will not receive any fish this year from the two hatcheries. 

Hot Creek Hatchery will conduct its normal plants to waters including: Owens River Sections 1, 2 and 3, Crowley Lake, Pleasant Valley Reservoir, Lower Bishop Creek, Lone Pine Creek, and Diaz Lake. 

Diseased fish will be euthanized and not planted.

“Those communities [north of Dead Man’s Summit] are therefore back in the same situation that they were in three years ago, which was hoping to get fish that will be diverted from other hatcheries into Mono County. So that’s what we’re relying on now,” said Economic Development Manager Jeff Simpson, who’s had several meetings within the past week with CDFW. According to Simpson, he has been pushing CDFW heavily to spend their own money on buying fish from private providers. 

Simpson made these comments at Tuesday’s Mono County Economic Development Commission meeting. 

There are apparently a few other hatcheries approved for stocking Mono County: “We’re just going to have to see what kind of fish we will be able to get from our other communities. If we have three years of no fish, then we need some hard cash to be spent to find some from private industry,” concluded Simpson.

Within the past two weeks, using $100,000 given from Mono County, all of the currently accessible, prominent bodies of water north of Deadman’s Summit have been stocked, except for higher elevation areas such as Virginia Lakes.

The timing of the outbreak is unfortunate, as the Eastern Sierra fishing opener approaches this weekend. CDFW fishery managers hope to carry out the traditional season opener as planned.

“All is not lost,” stated CDFW Director Charlton H. Bonham in a press release. “Fortunately, we learned much from the 2020 outbreak, and we have more knowledge and better tools to fight the bacterium this time around. We also believe we can continue stocking, with some adjustments and careful monitoring.”

Before the outbreak three years ago, the bacterium had never been detected in fish in California before.

About this bacterium: 

Lactococcus spp. occurs naturally in the environment and is usually spread by movement of fish or eggs. CDFW’s fish pathologists believe that it may have been carried into the hatcheries by birds that picked it up from an environmental source; since the current strain is identical to one found in fish farms in central Mexico, scientists believe that birds using the pacific flyway are the likely spreader of the bacterium. 

Fish infected with the bacterium show symptoms including: bulging eyes, lethargic or erratic swimming, and increased mortality. They can also be asymptomatic and show no signs of infection, depending on several factors, including water temperature (which is why CDFW will only stock the hatcheries’ fish in cold water areas). 

Fish-to-human transmission of this bacterium is “rare and unlikely”. The CDFW reminds anglers to follow USDA recommendations on cooking fish to an internal temperature of 145 degrees Fahrenheit.

Both Black Rock and Fish Springs hatcheries have juvenile fish that will be ready for planting at all their normal planting locations starting in 2023.