Friday, February 3rd, 2023
Friday, February 3rd, 2023

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Boaters Asked to Help Fight the Spread of Invasive Quagga and Zebra Mussels This Labor Day Weekend

California agencies battling the spread of invasive quagga and zebra mussels are asking boaters to be especially vigilant over the three-day Labor Day weekend.

Boaters are asked to clean, drain and dry motorized and non-motorized watercraft and any equipment that comes into contact with lakes, rivers or other waterways both before and after boating.

Anyone who launches a vessel into any body of water in the state is subject to watercraft inspections.

Quagga and zebra mussels are non-native freshwater mussels that multiply quickly and can encrust watercraft and infrastructure. They can also compete for food with more desirable species

The mussels spread easily from infested bodies of water by attaching to nearly anything that has been in an infested waterbody, or by being transferred in water held in boat engines, bilges, live-wells or buckets.

To ensure that watercraft is clean, drained and dry, many local agencies are conducting boat inspections. DFG has posted the list of these inspections on its website ( along with information about invasive mussels and what people can do to help prevent their spread in California.

Boaters should call ahead to check for restrictions prior to visiting their destination.

To prevent the spread of invasive mussels and pass inspections, boaters should inspect all exposed surfaces, remove all plants and organisms, drain all water, including that contained in lower outboard units, live-wells and bait buckets, and allow the watercraft to thoroughly dry before launching.

Watercraft should be kept dry for at least five days in warm weather and up to 30 days in cool weather between launches in different bodies of fresh water. These measures are vital to safeguard California waterways.

DFG has also developed a short video demonstrating the ease of implementing the clean, drain and dry prevention method, available at  In addition, a detailed guide to cleaning vessels to prevent the spread of mussels is available on the Department of Boating and Waterways website at

Travelers are also advised to be prepared for inspections at California Department of Food and Agriculture Border Protection Stations. Inspections may include not only a check of boats and personal watercraft, but also of trailers and onboard items. Contaminated vessels and equipment are subject to quarantine or impoundment.

Quagga mussels were first detected in the Colorado River system in January 2007 and were later found in San Diego and Riverside counties. They are now known to be in 24 water bodies in Southern California. Zebra mussels were discovered in San Justo Reservoir in San BenitoCounty in January 2008.

Both species can attach to and damage virtually any submerged surface. They can:

  • Ruin a boat engine by blocking the cooling system and causing it to overheat;
  • Jam steering equipment, putting occupants and others at risk;
  • Require frequent scrapping and repainting of boat hulls;
  • Colonize underwater substrates such as boat ramps, docks, lines and other underwater surfaces, necessitating constant cleaning;
  • Require costly maintenance, repair or replacement.

A multi-agency effort that includes DFG, the Department of Boating and Waterways, Department of Water Resources and Department of Parks and Recreation has been leading an outreach campaign to alert the public to the quagga and zebra mussel threats. A toll-free hotline at 1-866-440-9530 is available for those seeking information on quagga or zebra mussels.

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