County Supervisors took action Tuesday following recent spread of aquatic species through Delta waterways, raising concerns for drinking water systems, infrastructure and local ecosystems
Sacramento County has declared a local emergency in response to the growing threat posed by the invasive golden mussel, a rapidly spreading freshwater species that officials warn could have significant impacts on regional water infrastructure, public resources, agriculture and the environment.
The Sacramento County Board of Supervisors unanimously approved the emergency proclamation Tuesday, joining other California jurisdictions that have taken similar action as the species continues to spread through interconnected waterways across the state.
County officials said the declaration will strengthen coordination with regional, state and federal agencies while allowing Sacramento County to more effectively respond to the threat and protect critical water resources.
“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,” county officials stated in materials presented to the Board of Supervisors.
The golden mussel, also known as Limnoperna fortunei, is a freshwater mollusk native to Asia that was first detected in North America on Oct. 17, 2024, when the California Department of Water Resources discovered the species in the Sacramento-San Joaquin Delta. The discovery marked the first known detection of the species anywhere on the continent and immediately raised concerns among water managers, environmental agencies and infrastructure operators.
Since that initial discovery, the mussel has spread hundreds of miles through California waterways, prompting increased monitoring efforts and the implementation of boat inspection and decontamination requirements at lakes and reservoirs throughout the state.
Sacramento County officials said the species was first identified within county boundaries on Dec. 9, 2024, at the southern end of Andrus Island in the Delta. Less than a year later, on July 1, 2025, golden mussels were detected in the Sacramento River downstream of the Freeport Regional Water Authority, one of the region’s key municipal drinking water suppliers.
According to county documents, the infestation has already affected operations at the facility, resulting in increased maintenance requirements and higher costs associated with chemical treatment and infrastructure protection.
Unlike many aquatic invasive species, golden mussels reproduce rapidly and attach themselves to hard surfaces in dense colonies. The species can spread through natural waterways as well as by hitching rides on boats, trailers and recreational equipment that move between lakes and rivers.
Once established, officials say the mussels are extremely difficult to eliminate.
Large colonies can clog pipes, pumps, water intake systems and conveyance infrastructure. The mussels also pose risks to irrigation systems, hydroelectric facilities and municipal drinking water operations. Environmental concerns include competition with native aquatic species and disruption of natural ecosystem balance.
The declaration comes as neighboring counties report similar concerns. San Joaquin County previously declared a local emergency related to the species, while Kern County recently took similar action after golden mussels were discovered in waterways within its jurisdiction.
The spread has also heightened concerns at popular recreational destinations across California. In recent weeks, officials at Lake Tahoe reported intercepting boats carrying golden mussels before they could be launched, underscoring fears that the invasive species could establish itself in one of the state’s most treasured freshwater ecosystems.
For Sacramento County, the stakes are particularly high, according to officials. The county relies heavily on an extensive network of rivers, Delta channels, drinking water facilities, flood control infrastructure and agricultural irrigation systems. Any widespread infestation could increase operational costs for public agencies while creating challenges for businesses, farmers and residents who depend on those systems.
County officials said the emergency declaration will help facilitate ongoing monitoring efforts and strengthen partnerships with water agencies, environmental organizations and state agencies working to slow the species’ spread.
The California Department of Fish and Wildlife has described the golden mussel as a particularly difficult invasive species to contain because of its reproductive capacity and ability to attach to a wide variety of surfaces.
Officials continue to emphasize prevention as the most effective tool available.
Boaters, paddlers and other recreational water users are being urged to thoroughly clean, drain and dry boats, kayaks, canoes, paddleboards, tubes and other watercraft before transporting them between waterways.
The county is directing residents to the national Stop Aquatic Hitchhikers program for guidance on proper cleaning and decontamination practices designed to prevent the spread of invasive aquatic species.
Residents who believe they have found golden mussels are encouraged to report sightings to the California Department of Fish and Wildlife by emailingInvasives@wildlife.ca.gov.
Under the emergency proclamation approved Tuesday, Sacramento County’s Director of Emergency Services will be required to provide status updates to the Board of Supervisors at least every 60 days regarding ongoing response efforts and conditions related to the infestation.
The declaration remains in effect as county officials continue evaluating the impacts of the species and coordinating with agencies throughout California working to protect waterways and water infrastructure from further spread.
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