Invasive Mussels

ACWD would like to Invasive Musselsremind boaters to do their part to help thwart invasive quagga and zebra mussels. Boats are the primary transporters of these species and boaters should take special care to properly clean, drain, and dry their vessels.


Non-native quagga and zebra mussels threaten California in a variety of ways: 

  • They wreak havoc on the environment by disrupting the natural food chain and releasing toxins that affect other aquatic species.
  • They can colonize on hulls, engines, and steering components of boats and can damage boat motors and restrict cooling.
  • They frequently settle in massive colonies that can block water intake structures and threaten municipal water supplies, agricultural irrigation, and power plant operations.
  • They reproduce quickly and in large number and are extremely difficult to eradicate.

Efforts are currently underway to implement a region-wide strategy to prevent the spread of these mussels to local water bodies. As a part of this effort, ACWD has become an active member of the Bay Area Regional Consortium for Mussel Prevention. Boat inspections at many of the lakes and reservoirs you may visit, including Quarry Lakes, are an important part of this strategy. Preventing the spread of mussels is essential to protecting ACWD’s water delivery infrastructure and avoiding the significant costs ACWD customers would have to bear in the event of a mussel infestation.

What You Can Do

Quagga and zebra mussels move from one place to another primarily through human-related activities. They attach to hard surfaces, including boats and fishing gear, and can survive out of water for up to a week. The microscopic larvae can be transported in bait buckets, bilges, ballast water, or other equipment that holds water. To prevent the spread of mussels, follow these steps:

  • When removing your boat from the water: - Inspect all exposed surfaces – small mussels feel like sandpaper to the touch.
    - Wash the hull of each watercraft thoroughly.
    - Remove all plant and animal material.
    - Drain all water and dry all areas.
    - Drain and dry the lower outboard unit.
    - Clean and dry all live-wells.
    - Empty and dry any buckets.
    - Dispose of all bait in the trash.
    - Wait five days in hot weather, and up to 30 days in cool and moist weather, before launching into different fresh waters.
    - Keep watercraft dry between launches into different fresh waters.
  • Do not put your boat into waters that are inhabited or at high risk of inhabitation. These areas include: Lake Mead, Lake Havasu, Lake Mojave, Lake Skinner, Copper Basin Reservoir, San Justo Reservoir, and generally waters of San Benito County and California counties south of the Tehachapi Mountains, and any waters outside of California.
  • Maintain a clean and dry boat inside and out! This includes all bilges, tanks, water pipes, trailers and accessories.
  • Allow extra time when you visit local lakes and reservoirs to allow for staff to inspect all boats for invasive species and standing water. Remember that boats failing inspection may be turned away.

For More Information

To learn more about quagga mussels, zebra mussels, and other invasive aquatic species and how to prevent their spread, visit the California Department of Fish and Game website or call 866-440-9530.

For more information on boat inspection requirements at Quarry Lakes, contact East Bay Regional Park District.