Invasive golden mussels prompt Sacramento County emergency declaration
The Sacramento County Board of Supervisors declared a local emergency Tuesday because of the growing threat posed by invasive golden mussels.
The golden mussel, a freshwater mollusk native to Asia, was first detected in the Sacramento-San Joaquin Delta by the California Department of Water Resources on Oct. 17, 2024. The discovery marked the first known sighting of the species in North America and raised concerns among wildlife and water agencies because of its ability to reproduce rapidly and form dense colonies that can clog pipes, pumps and water conveyance systems.
Since then, the species has spread hundreds of miles through California’s interconnected waterways,prompting boat inspection and decontamination requirements at lakes and reservoirs across the state. Lake Tahoe officials also have intercepted boats carrying golden mussels in recent weeks, underscoring concerns that the invasive species could spread to one of California’s most iconic waterways.
“The potential consequences of a growing golden mussel infestation in the Sacramento-San Joaquin Delta and Sacramento River pose a serious and immediate threat to Sacramento County’s public infrastructure, health, and economic stability,” the county Board of Supervisors’ agenda item for Tuesday’s meeting stated.
The species was detected in Sacramento County on Dec. 9, 2024, at the south end of Andrus Island. On July 1, 2025, the golden mussel was discovered in the Sacramento River downstream of the Freeport Regional Water Authority, a key municipal drinking water supply. According to the agenda item, its presence disrupted system operations and increased maintenance and chemical treatment costs.
In response to the species’ continued spread, the board declared the golden mussel infestation a local emergency Tuesday, joining San Joaquin and Kern counties, which also have declared local emergencies because of the invasive species.
“Sacramento County relies on an extensive network of waterways and water infrastructure to support residents, businesses and agriculture,” a spokesperson for the California Department of Fish and Wildlife wrote in a statement. The agency said the bivalve is difficult to contain, making its continued spread a growing threat.
Officials said golden mussels spread primarily by attaching to boats, trailers and equipment moved between waterways. Once established, the mollusks are extremely difficult to eradicate and can damage drinking water systems, irrigation infrastructure and hydroelectric facilities while disrupting native aquatic ecosystems.
County officials said they would work with water agencies, environmental partners and state officials to monitor and contain the spread of the golden mussel. Under the local emergency declaration, the director of emergency services must report back to supervisors at least every 60 days on the status of the emergency.
