Agencies Ask Boaters to “Clean, Drain and Dry” for Labor Day Weekend – Help to Prevent Spread of Invasive Mussels

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Invasive MusselsCalifornia state departments are asking boaters to clean, drain and dry their boats to stop the spread of harmful invasive mussels. Properly cleaning and drying boats will also help them avoid quarantines or being turned away from a water destination.

“Quagga and Zebra mussels pose a serious threat to our waters and fisheries,” said Department of Fish and Game (DFG) Director Donald Koch. “The spread of these mussels threatens water delivery systems, hydroelectric facilities, agriculture, recreational boating and fishing, and the environment in general. Boaters should be prepared for inspections throughout the state that will help ensure California’s water bodies remain mussel-free.”

In addition to being sure to clean, drain and dry watercraft, the Department of Boating and Waterways (DBW) urges boaters to plan for possible launch restrictions and inspections by calling water bodies before leaving home. Programs and requirements vary and can change rapidly.

Zebra Mussel - Dreissena polymorpha / Shell: D-shaped and triangular; thin and fragile to thick and sturdy; smooth or shallowly ridged; solid light to dark brown or striped • Attaches to hard surfacesQuagga Mussel - Dreissena bugensis / Shell: D-shaped and triangular; thin, fragile; smooth or shallowly ridged; solid light to dark brown or dark concentric rings; paler near hinge  • Attaches to hard and soft surfaces“Anyone planning to go boating should contact their destination about local restrictions or requirements,” said DBW Director Raynor T. Tsuneyoshi. “At some locations, potentially contaminated vessels – those not properly cleaned, drained and dried – could be turned away.”

Quagga and Zebra mussels can cause severe problems for boaters and water enthusiasts. They can:

  • ruin the engine by blocking the cooling system – causing overheating
  • increase drag on the bottom of the boat, reducing speed and wasting fuel
  • jam steering equipment on boats
  • require scraping and repainting of boat bottoms
  • colonize all underwater substrates such as boat ramps, docks, lines and other underwater surfaces requiring constant cleaning

To help prevent the spread of these mussels, boaters should inspect all exposed surfaces, wash boat hulls thoroughly, remove all plants from boat and trailer, drain all water, including lower outboard units, clean and dry livewells and bait buckets and dispose baitfish in the trash. Watercraft should be dried for at least five days between launches in different fresh bodies of water. These steps are designed to thwart spread of the invasive mussels, safeguard boats and preserve high quality fisheries.

“We are strongly encouraging boaters to arrive at State Park reservoirs with clean and dry vessels to ensure they are granted access,” said Roy Stearns, spokesman for California State Parks (Parks). “Boaters should be prepared to have their boats inspected and we hope that people understand and cooperate to stop the spread of this destructive invasive species.”

California law makes it illegal to possess or transport Quagga or Zebra mussels and gives DFG authority to stop, detain, search and quarantine boats suspected or determined to be contaminated with mussels. Additional agencies have been granted this authority including the Department of Food and Agriculture (CDFA) and Parks.

Help to prevent spread of invasive mussels“Vehicles with watercraft are being stopped at many of the California border stations for inspection,” said Food and Agriculture Secretary A.G. Kawamura. “From January 2007 to July 2008, we have inspected more than 140,000 vessels crossing into California. While more than 13,000 needed cleaning, we have confirmed adult mussels on nearly 170. Each of those finds meant we saved a California lake or reservoir from exposure to the mussels.”

Zebra mussels inhabit water depths from four to 180 feet, while Quagga can reach depths more than 400 feet. Both mollusks can attach to and damage boat trailers, cooling systems, boat hulls and steering equipment. Mussels attached to watercraft or trailers can be transported and spread to other water bodies. Water in boat engines, bilges, live wells and buckets can carry mussel larvae (called veligers) to other water bodies as well.

Quagga mussels were first detected in the Colorado River system in January 2007 and were later found in San Diego and Riverside counties by state and local water agencies. Zebra mussels were discovered in San Justo Reservoir in San Benito County in January 2008.

A multi-agency taskforce that includes DFG, the Department of Water Resources, DBW, CDFA, Parks and multiple federal partners is currently working to determine the extent of the Quagga and Zebra mussel threat and to educate watercraft users. As part of the public education effort, the state continues to facilitate Quagga/Zebra inspection and decontamination trainings with more than 400 individuals in San Diego, Redding, Fresno, Stockton, Monterey, Los Alamitos, Ontario, Lake County, Sacramento and Yountville.

A public toll-free number hotline has been established for boaters and anyone involved with activities on lakes and rivers seeking information on the invasive and destructive Quagga mussels at 1-866-440-9530.

For more information on the Quagga/Zebra mussel response, please visit the DFG Web site at

Learn what boaters can do to stem the spread of the invasive Quagga mussel (PDF).