How to Stop the Spread of Golden Mussels

Boaters and recreationists can help combat the spread of a new invasive recently discovered in California waterways – the golden mussel. Despite its flashy name, this species poses a significant threat to infrastructure and the ecological health of all state waterways.

With the 2024 discovery of the invasive golden mussel in a State Water Project (SWP) reservoir, the non-native freshwater/brackish bivalve poses a threat to California’s water delivery systems and environment as they can survive in a wide range of environmental conditions. When golden mussel populations are established, they are difficult to control since they can become very abundant and are easily spread to new waterbodies. It is important to be vigilant of these destructive invaders.

If left unchecked, they can:

• Alter aquatic ecosystems by filter-feeding on planktonic algae and changing the habitat structure
• Impact water delivery systems by clogging small-diameter pipelines, screens, and filters
• Impact recreation by fouling boat hulls and motors and clogging intakes and cooling lines

The golden mussel (Limnoperna fortunei) was first discovered in North America in October 2024 when DWR staff conducted routine water quality monitoring in the Port of Stockton in California. Soon after, golden mussels were also discovered in Merced County at O’Neill Forebay, part of the SWP. Golden mussels range from ¾ inches to 2 inches in size and have a light to dark yellowish-brown to brown-colored shell.

To prevent the spread of invasive mussels, DWR routinely monitors for these species and acts to prevent their spread to non-infested waters. DWR, in partnership with the California Department of Fish and Wildlife (CDFW) and California State Parks’ Division of Boating and Waterways informs boaters to always remember to clean, drain, and dry their boats before entering and leaving lakes, rivers, and other waterways. 

When recreating on California’s waterways, always remember to:

• Clean off aquatic plants and animal material from your boat, trailer, and equipment before leaving the ramp or parking lot
• Drain ballast, bilge, live-wells, and other water-containing devices, and never drain back into the waterway
• Dry equipment before launching into another body of water. As waiting periods vary, check with the waterbody owner on their watercraft inspection criteria.

As part of National Invasive Species Awareness Week, DWR produced a new golden mussel video that covers the impacts of the golden mussel and outlines steps you can take to prevent its spread. By working together and staying vigilant, we can protect California’s water supply and environment.

For more information on watercraft inspections and additional resources, go to DWR’s website at water.ca.gov/mussels. If you find these invaders, notify CDFW’s Invasive Species Program by email at Invasives@wildlife.ca.gov or call (866) 440-9530.