Invasive golden mussels confirmed in Port of West Sacramento for first time

The invasive golden mussel has now been confirmed in the Port of West Sacramento, marking the species' northernmost detection in California since it was first discovered in Stockton in 2024, wildlife officials announced Saturday.

The California Department of Fish and Wildlife said the mussels found in West Sacramento represent an established local population rather than a one-time introduction from a contaminated boat.

Officials have notified the cities of West Sacramento and Sacramento, along with Sacramento and Yolo counties, about the discovery.

The detection comes as communities across the Sacramento-San Joaquin Delta continue to grapple with the invasive species, which can rapidly reproduce and attach themselves to hard surfaces, clogging water intake pipes and damaging infrastructure while disrupting native ecosystems.

UC Davis Professor Edwin Grosholz said the spread isn't surprising.

"If they're out in the river systems, if they're up and down the state, there's just nothing you can really do," Grosholz said.

He said the state should treat the spread like an "aquatic wildfire" and respond with the same level of urgency.

"If the state thought of this as an aquatic wildfire and I'm trying to put this out in the media, the state needs to take it seriously," he said.

Golden mussels were first detected in California in October 2024 at the Port of Stockton, marking the species' first known appearance in North America.

Grosholz said that the longer the mussels spread, the more expensive it will become to remove them from water infrastructure and pipes.

Those impacts are already being felt in Stockton, where the city is spending more than $200,000 to remove the mussels from screens in the city's water intake pipes — 30-40% of them were clogged.

"We're already having problems and this is something that's going to be around for a long time," San Joaquin County Supervisor Mario Gardea said.

San Joaquin County declared a state of emergency back in April, creating a committee dedicated to finding solutions to slow the spread. 

"Different types of paints, ultrasound, ultraviolet lights to try and keep them from attaching to some of the material," Gardea said.

But Grosholz said at this point, the best chance is to keep the mussels out of waterways that aren't connected to the delta.

"The only way to contain it is to keep it out of disconnected areas," he said. "In other words, places like Clear Lake, places like Lake Tahoe that are important to recreation and other uses."

The discovery in West Sacramento follows growing concerns in Stockton, where city leaders also declared a local emergency over the impact of golden mussels on the city's drinking water system.

State wildlife officials continue to urge boaters and anyone using California waterways to thoroughly clean, drain and dry their watercraft and equipment before moving between bodies of water in an effort to slow the spread of the invasive species.