History of the Quagga and Zebra Mussels

Zebra and quagga mussels are native to Eastern Europe with zebra mussels coming from the Black and Caspian seas and quagga mussels coming from the Dneiper River in the Ukraine.

Zebra mussels were first discovered in the Great Lakes in 1988, and a year later, quagga mussels were discovered in the same area. It is believed they arrived in America via ballast water discharge from boats traveling from Europe.

Europeans have been dealing with the mussels for 200 years by designing industrial facilities with the creatures in mind. The mollusks also have natural predators and controls in those ecologies. But in North America, the mussels can reproduce rapidly when introduced into a new environment because of the lack of control.

The mussels were found in Lake Mead on Jan. 6, 2007, and later throughout Lake Mead's lower basin. Almost two weeks later, they were found in lakes Mojave and Havasu in the Colorado River. They have also been identified in San Diego County in San Vicente Reservoir, Lake Murray Reservoir, Lower Otay Reservoir, Lake Dixon, and Miramar Reservoir and in Riverside County in Lake Skinner and Lake Mathews.

Most recently, zebra mussels were found in January in San Justo Reservoir, San Benito County - a mere 250 miles away from Lake Tahoe.

- Sources: U.S. Fish and Wildlife Service and California Department of Fish and Game.

What are quagga and zebra mussels?

Both quagga and zebra mussels are part of the Dreissena family and are close cousins. Differences include physical appearance and ecological tolerance.

They can range in size from microscopic as larvae to about two inches long as adults.

They can live up to five years and can spawn constantly if conditions are amenable, producing millions of offspring.

In their larval stage the mussels are free floating and carried with currents. As adults they use byssal threads to attached to hard surfaces, and can detach to move to new habitats.

Zebra mussels can survive in waters as warm as 86 F but survive best in 64 F water. Scientists are researching if quagga mussels can survive in similar temperatures, but prefer 61 F.

Both zebra mussels and quagga mussels can survive cold waters near freezing, but cannot tolerate freezing - zebras need waters above 54 F in order to reproduce and quaggas need temperatures about 48 F.

To survive the mussels also need low salinity, high calcium content, high PH. Both breeds can survive in low oxygen concentrations.

They prefer to exist in environments with waters moving at low speeds and hard to attach to. Quagga mussels can tolerate living in soft sediments, but zebra mussels seldom do.

Zebra mussels are typically found from just below the surface to about 40 feet. Quagga mussels are typically found at any depth as long as oxygen is available.

Both species prefer to avoid light and are usually found in shaded areas or below the depth that light penetrates water.

- Sources: U.S. Fish and Wildlife Service