Golden mussels spread to East Bay’s Lake Del Valle for the first time

Golden mussels have spread to a popular reservoir in the East Bay, prompting officials to enforce a 30-day quarantine on all boaters who launch at Lake Del Valle in Livermore, where the invasive species recently emerged.

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The East Bay Regional Park District has been enforcing a banding program for boaters since the summer of 2025, attaching tamper-proof plastic ties to the eye bolts of watercrafts to track where they’ve been before they can enter another waterway. The goal is to prevent the spread of the tiny mussels, which were detected for the first time in North America at the Port of Stockton in the Sacramento-San Joaquin Delta in October 2024. At the time, officials with the California Department of Fish and Wildlife said they were likely introduced by a ship traveling from an international port. The news encouraged outdoor destinations like Lake Tahoe to double down on their existing watercraft inspection programs, requiring motorized vessels to also undergo a decontamination process.

Golden mussels, a distant cousin of quagga and zebra mussels, are native to rivers and creeks in coastal Asia. They “can thrive in water with much lower calcium levels” than other species, “putting local water sources and aquatic ecosystems at greater risk of invasion,” according to the news release. 

It’s not the first time the mussels have been detected in the East Bay. The California Department of Fish and Wildlife announced they were found on a settlement plate in Contra Loma Reservoir in Antioch in October 2025, where the same quarantine rules are in effect.  

Boats that only launch at Lake Del Valle and return with a secure band will not be subject to the quarantine, officials said in a news release. Boats without a band will be subject to inspection for the presence of the invasive species, which costs $10 for motorized vessels and $5 for car-top watercraft and inflatables. 

Inspections are also required at Lake Chabot Regional Park, Quarry Lakes Regional Recreation Area and Shadow Cliffs Regional Recreation Area, and apply to all boats, kayaks, canoes, sailboats, inflatable craft and floating boards, according to the news release. Lake Tahoe implemented its own watercraft inspection program in 2008.

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“Mussels can quickly contaminate the waterways and can rapidly spread,” officials said, noting they “can attach to nearly any underwater surface, including boats, ropes, buoys and aquatic plants that become entangled on anchors and trailers.” 

Boaters are advised to “clean, drain and dry” their vessels and belongings, including life vests and paddles, and remove all debris, animals and plants by disposing of them in the trash. The East Bay Regional Park District also instructed people to allow their equipment to dry completely before entering the water again.