Golden Mussel Detection in the California Delta

Initial Discovery of Golden Mussels

On October 17, 2024, the California Department of Water Resources (DWR) reported finding mussels attached to a float in the Port of Stockton.

These mussels were not observed during prior inspections of the float. Samples of the unknown species were promptly sent to the UC Davis Genomic Variation Laboratory and the California Department of Food and Agriculture (CDFA) laboratory for identification.

Genetic Analysis Confirms Golden Mussels

By October 23 and 24, genetic analyses from UC Davis and CDFA confirmed the presence of golden mussels (Limnoperna fortunei). This invasive species, previously unknown in North America, represents a serious ecological and infrastructural threat.

Additional Findings in O’Neill Forebay

On October 25, 2024, mussels were reported on artificial monitoring substrates in O’Neill Forebay, a site used for tracking quagga and zebra mussels. Specimens from this location are now en route to UC Davis and CDFA for further genetic analysis.

Why Golden Mussels Are a Concern

Golden mussels share similarities in appearance and biology with quagga and zebra mussels, but they pose unique risks. They can thrive in waters with lower calcium levels, enabling them to establish in a wider range of environments. Their dense colonization of hard surfaces can:

• Block municipal and industrial water intakes
• Require costly, ongoing biofouling removal
• Disrupt native species assemblages
• Degrade water quality

How Golden Mussels Were Likely Introduced

Golden mussels are native to rivers and creeks in China and Southeast Asia. Outside their native range, they are established in regions including Hong Kong, Japan, Taiwan, Brazil, Uruguay, Paraguay, and Argentina. In California, they were likely introduced by an international ship.

What’s Next?

The California Department of Fish and Wildlife (CDFW) will continue to share updates on detection and response efforts in the coming weeks and months. Immediate steps are being taken to inform water managers across California about this discovery.

How You Can Help

If you manage or operate water systems, it is critical to stay informed and monitor for signs of golden mussels. CDFW encourages proactive communication and preventive measures to reduce the risk of spread.

For more details, visit the CDFW News Archive.

Source: https://bassanglermag.com/golden-mussel-detection-in-the-california-delta/

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