Invasive Golden Mussel Detected at Silverwood Lake and Pyramid Lake

New Boating Protocols Implemented and Effective Immediately at Silverwood Lake

SACRAMENTO, Calif.-The Department of Water Resources (DWR), California Department of Fish and Wildlife (CDFW), and California State Parks have confirmed presence of the invasive golden mussel at Pyramid Lake in Los Angeles County and Silverwood Lake in San Bernardino County. These lakes are the southernmost State Water Project (SWP) reservoirs where golden mussels have been detected. The invasive species was recently discovered during a routine water test by DWR; in response, State Parks has updated Silverwood Lake's boat inspection protocols, effective immediately. Pyramid Lake, which is managed by DWR, implemented exit inspections following the discovery of quagga mussels in 2016.

The golden mussel, native to China and Southeast Asia, was initially detected in the Sacramento-San Joaquin Delta and O'Neill Forebay in October 2024 and has subsequently spread south. This small freshwater bivalve is known for its rapid reproduction and ability to clog water infrastructures, disrupt ecosystems, and outcompete native species. These invasive mussels can also cause significant damage to boats by attaching to hulls and clogging engines, leading to increased costs for boaters and other motorized vessel owners. Currently, there are no effective methods to treat or eliminate the golden mussel from infested waterways, making prevention of further spread to non-infested waterways a top priority.

Through a series of coordinated actions with state and local partners, DWR has expanded its activities to protect SWP facilities against this destructive species while maintaining operational capacity to deliver water to 27 million Californians and 750,000 acres of farmland. Actions to mitigate the spread of golden mussels include ongoing research to better understand and suppress the species, as well as designing and implementing new measures to protect pumping plants, hydroelectric plants, and water supply deliveries.

New Boating Protocols at Silverwood Lake

Due to the confirmed presence of golden mussels in Silverwood Lake, the following changes to boating protocols are now in effect:

• Vessel inspections upon arrival are discontinued:As the lake is now infested with golden mussels, mandatory inspections for invasive mussels upon entry are no longer required.
• Drain plug removal/outbound inspection:Drain plugs should be pulled on all vessels prior to exiting Silverwood Lake to prevent the transport of lake water, which may contain microscopic golden mussel larvae or veligers.
• Clean and dry advisory:Boaters are strongly advised to ensure their vessels are thoroughly cleaned, drained, and driedafter recreating on Silverwood Lake. For vessels that cannot be completely drained of water, such as boats with ballast tanks, boaters are advised to check with the specific body of water they plan to recreate for decontamination guidelines before launching in other lakes or bodies of water not yet infested with invasive mussels. These measures aim to reduce the risk of spreading golden mussels to other California waterways not impacted by invasive mussels. A list of reservoirs contact and watercraft inspection information can be found here.

Potential Impact on Lake Perris

While nearby Lake Perris State Recreation Area (SRA) has not yet tested positive for golden mussels, the daily transfer of millions of gallons of water from Silverwood Lake to Lake Perris, combined with the invasive mussel's rapid reproduction, makes the spread to Lake Perris highly likely. Monitoring efforts are ongoing, and the public will be notified of any updates. Lake Perris is continuing inspections for now and will discontinue incoming inspections if Lake Perris tests positive for golden mussels and will adopt this exit inspection protocol.

For more information on invasive species prevention or to report suspected sightings of golden mussels, visit the CDFW's golden mussel webpage, call (866) 440-9530 or email [email protected].

For information about SWP golden mussel mitigation, visit DWR's website.

Contacts:

[email protected]
California State Parks

[email protected]
California Department of Water Resources