Golden Mussel Warning For Mother Lode Waterways

Sonora, CA – Stanislaus National Forest is warning boaters to “exercise extreme caution/diligence” after the Golden Mussel was discovered on watercraft in California last year.

This alert comes as other agencies have also cautioned about the spread of the highly invasive mussel. We reported in February that recreational boating was closed on Lake Tulloch due to the invasive mussel threat. Before that, on December 7th, the Bureau of Reclamation temporarily suspended all boat launches at New Melones Lake after golden mussels were discovered in the Sacramento-San Joaquin Delta last year.

Golden mussels (Limnoperna fortunei) range from ¾ inches to 2 inches in size and have a light to dark yellowish-brown or brown-colored shell. According to forest officials, the non-native freshwater/brackish bivalve, which can thrive in a variety of environmental circumstances, is a threat to the state’s water delivery infrastructure and ecosystem. They were first discovered in North America in October 2024 when the California Department of Water Resources staff conducted routine water quality monitoring in the Port of Stockton; the golden mussels quickly spread and were discovered during a state water project at the Merced County at O’Neill Forebay Reservoir.

The forest is urging visitors to area waterways to take extra precautions to ensure their watercraft is free of the highly invasive species. Forest officials provided these tips to remember when recreating:

• 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.

Golden mussels may grow plentifully and are quickly dispersed to other water bodies, making them challenging to manage once populations have been established. Forest officials say that being on the lookout for these damaging intruders is crucial. They disclose that 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

Learn more about the Golden Mussel by clicking here.