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The
zebra mussel and it's close cousin the quagga mussel have
not yet been introduced into the Pacific Northwest, but they
are a highly invasive species that is edging its way across the country. The quagga mussel has recently been found in Lake Mead, Lake Mojave, Lake Havasu, and the lower Colorado River.
The zebra mussel is native to western Russia and was introduced into
Europe a couple hundred years ago through canals connecting
various waterways across the continent. They came to North
America in the mid-1980's when a ship probably brought them
over in its ballast and dumped them out in Lake St. Clair
(between Lake Huron and Lake Erie). Within a year of being
discovered, they blanketed Lake Erie, and within 5 years
they were incredibly abundant in all the Great Lakes and the Mississippi
and Ohio Rivers.
Zebra
mussels reach densities in the tens of thousands per square
meter and have caused dramatic environmental and economic
damage. They have almost single handedly eliminated already
troubled native mussel populations in some areas. They
use the native mussels as substrate, attaching to them with tough
byssal threads and reducing the native mussel's ability to move and feed.
Each adult zebra mussel can filter a liter of water every
day and remove all of the microscopic plants and animals from the water, thus reducing the food available to planktivorous
fish and other animals. On the economic front, they clog drains,
intakes, and boat motors and replace sandy beaches with sharp
mussel shells.
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Size: large
Identifying feature(s): sturdy triangular shell with a flat side, brown and white markings
Habitat: lakes, large rivers
Tolerance: tolerant
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Mollusca
