Thumbnail-Sized Mollusk Cuts Swath of Destruction

"At Sea" from our February 7, 2007, CW Reckonings

February 7, 2007


The destructive quagga mussel is on the loose and may be spreading to a lake near you. First discovered in Lake Erie in 1989, the mussels eventually extended into the other Great Lakes, the St. Laurence Seaway, and Lake Simcoe in Ontario.

In January, researchers discovered quagga mussels in Lake Havasu, Lake Mead, and Lake Mohave, inland lakes on the Colorado River near the California/Arizona border. Isolated cases have been reported elsewhere in California, in very small bodies of water in Riverside and San Bernardino.

The quagga mussel is native to the Caspian Sea and likely found its way to North America in the ballast holds of oceangoing ships, as did the similarly invasive zebra mussel. The thumbnail-sized quagga mussel is fan-shaped, with pointed edges at either side; it’s light tan to white in color, with dark, narrow stripes.


Unlike zebra mussels, quagga mussels can live in almost any type of water-warm or cold, shallow or deep, fresh or brackish-but they prefer silty or sandy freshwater lake bottoms. The mussels feed year-round, even in winter.

Because of their hardiness, these little critters wreak serious havoc. They eat up the food source for fish and can change the food web in lakes. They take in enormous amounts of pollutants, which can harm the wildlife that eat them. And when humans ingest animals that have consumed quagga mussels, such as yellow perch-which apparently find quagga mussels a delicacy-contaminants like Clostridium botulinum enter the food chain.

Quagga mussels can attach themselves to any hard surface, causing serious damage to pipes and pumps at power and water-treatment plants, docks, breakwalls, buoys, trailers, and of course, boats. All freshwater boaters should take the following steps to stop the spread of the quagga mussel:

  • Thoroughly wash the hull once the boat is out of the water, removing all plants, animals, and mud.
  • Drain any water through the vessel’s hull plug and ensure the area is dry.
  • Make sure the outboard engine is clean and dry.
  • Empty and dry any buckets.
  • Dispose of all bait in a trash receptacle.
  • Spray boat and equipment with high pressure and/or hot tap water, especially if moored for more than a day, or dry boat and equipment and keep out of the water for five days. For more information, contact the California Department of Fish and Game at (866) 440-9530 or

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