Golden mussel (Limnoperna fortunei) is a small invasive freshwater bivalve, recently discovered in the U.S. for the first time. They can range from pale gold to deep yellow or brown color and are similar in size and shape (<1.5 inches) to more established invasive species, zebra and quagga mussels. Golden mussels are hardy, thriving in both fresh and brackish water, and tolerant of diverse water conditions, including much lower dissolved calcium than their well-known invasive counterparts (CDFW 2024). This is likely an indicator of high establishment and/or distribution potential in California’s freshwater systems.
Originating in rivers and creeks in southeast Asia, the golden mussel was first discovered in California at Rough and Ready Island, near the Port of Stockton, in October 2024. It was likely introduced from ship ballast water when traveling to California from international ports, because the golden mussel has a large non-native biogeographic range, from South America to east Asia. As of November 2024, colonies as large as 500 individuals have been observed in waters in and near the San Joaquin River (CDFW 2024). They have not yet been identified in the Feather River but may have potential to occur due to the freshwater habitat and connected waterways of the Delta and Central Valley.
Golden mussels pose a threat to human activities and aquatic species. Their dense colonies of up to 200,000 organisms per square meter attach to hard surfaces and clog water intakes, power plants, and other infrastructure, and can impede distribution of fresh water. Golden mussels affect aquatic recreation by colonizing docks and beaches and crusting upon vessels, engines, steering components, and equipment. Regarding water quality, golden mussels are highly efficient filter feeders, overconsuming phytoplankton and other microscopic organisms that entire ecosystems rely on, potentially eliminating lower trophic levels. This disturbance is highly likely to negatively affect aquatic organisms locally and downstream, including native species (CDFW 2024).
Controlling the spread of golden mussels is essential to reducing their impact on aquatic species. Control of zebra and quagga mussels through cleaning, draining, and drying of vessels and aquatic equipment when removed from water bodies has been effective in reducing their spread, and will likely reduce spread of golden mussels. The California Department of Water Resources is currently inspecting watercraft at O’Neill Forebay near San Luis Obispo to reduce spread. Reporting invasive species and suspected invasive species to the CDFW Invasive Species Program by phone, email, or online can also improve response to and removal of invasive species (CDFW 2024).
If you observe a mussel that you suspect to be a golden mussel, please report it to CDFW’s Invasive Species Program. Be sure to include the specific location of the observation, at least one clear close-up photograph of the organism, and your contact information. Observations may be reported using one of the following options:
Online: wildlife.ca.gov/Conservation/Invasives/Report
Email: invasives@wildlife.ca.gov
Telephone: (866) 440-9530
If you are concerned that invasive mussels may be present in your local water bodies or have a project that may be affected by invasive mussels, ECORP may be able to assist you by designing and implementing a study to determine if invasive mussels are present in the water bodies of concern. ECORP works closely with a local molecular ecology laboratory to design and conduct studies for detection of invasive and hard-to-find species using environmental DNA (eDNA). eDNA is a cost-effective, unintrusive, and rapid method for early detection of invasive species. This method relies on analyses of surface water samples using quantitative polymerase chain reaction (qPCR) to detect trace amounts of DNA derived from organisms that often cannot be readily observed with traditional survey methods due to their small size, low abundance, and/or cryptic nature.
To find out more about these services, please feel free to contact Todd Chapman in the Irvine office at (714) 648-0630, or David Thomas in the Rocklin office at (916) 782-9100.
Source cited (CDFW 2024): California’s Invaders: Golden Mussel
