Quagga / Zebra Mussel - FACT SHEET

State and federal agencies have initiated a unified response to the quagga / zebra mussel invasion in California. The involved agencies include CDFW, Water Resources, Food and Agriculture, Boating and Waterways, Parks and Recreation, Cal Fire, CalTrans, State Water Resources Control Board, State Lands Commission, Natural Resources Agency; U.S. Fish and Wildlife Service, U.S. Forest Service, U.S. Army Corps of Engineers, U.S. Geological Survey, National Park Service, and Bureau of Reclamation; Metropolitan Water District of Southern California; and multiple local authorities.

History of quagga / zebra mussels in North America

  • In the 1988, zebra mussels were discovered in the Great Lakes and a year later, quagga mussels were discovered in the same area.
  • January 6, 2007 quagga mussels were found in Lake Mead, NV and subsequent surveys found mussels in Lakes Mojave and Lake Havasu in the Colorado River, and within the Colorado River Aqueduct.
  • January 10, 2008, zebra mussels were discovered in San Justo Reservoir, San Benito County.
  • To date, quagga mussels have been found in waterbodies in San Diego, San Bernardino, Orange, Riverside, Imperial, Ventura, and Los Angeles counties.

Zebra Mussels

  • Colonize primarily on hard surfaces in freshwater, from the surface to more than 180 feet in depth.

Quagga Mussels

  • Habitat variable; can colonize both hard and soft surfaces in freshwater, from the surface to more than 400 feet in depth.

Both Mussels

  • Native to Ukraine and Russia.
  • It is believed that quagga/zebra mussels were introduced to the United States from ballast water of trans-oceanic ships.
  • Freshwater mollusks with D-shaped, triangular shells. The shells are smooth or shallowly ridged and can be variable in color, from solid light to dark brown, or have alternating dark and light stripes.
  • At various stages of life mussels range in size from microscopic to the size of a fingernail.
  • Adult mussels can spawn multiple times a year and have the potential to produce millions of offspring per spawning season.
  • Are filter feeders that consume large quantities of plankton that form the base of the food web.
  • Adults attach to aquatic plants, boats, motors, trailers, and recreation equipment; microscopic larvae can be present in water.
  • Adults can survive out of water for a week or longer depending on temperature and humidity.

Border Protection Stations
Jan. 29, 2007 - Dec. 31, 2020

  • Watercraft Inspected: 1,882,955
  • Watercraft with water needing drainage: 121,078
  • Watercraft with confirmed adult mussels: 1,807

Call the Invasive Species Information Line for more information: (866) 440-9530