Animal Molluscs
Family: Dreissenidae
Classification: Prohibited
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Mussels removed from a boat
at the Spokane Port of Entry by WSP Inspectors |
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Zebra mussels (Dreissena
polymorpha) and Quagga mussels (Dreissena bugensis) are native to
the Caspian Sea, and were introduced into the Great Lakes in the mid 1980’s
in ships ballast water. Zebra mussels have since spread to more twenty states,
and two Canadian Provinces. Because the mussels can live out of water for up
to a month if they are not subjected to heat or extreme drying conditions they
may be easily transported on recreational boats. They can be on aquatic plants
attached to boats or trailers, or as microscopic larvae in bilges, live wells,
motor cooling systems and other water systems, or attached to the hulls, especially
around trim tabs, transducers, keels or propellers. Usually the zebra mussel
is about the size of an adult fingernail, but can be as large as two inches,
or as small as a sesame seed. Where introduced they threaten native fish and
wildlife by consuming available food and smothering native species. They clog
power plant and other water intakes, costing taxpayers millions.
Quagga mussels
can tolerate a much wider range of temperatures and water depths than zebra
mussels. They can also tolerate brackish water, and are able to thrive in areas
that zebra mussels cannot. The Quagga mussel is usually light tan to almost
white, with narrow strips. It is fan-shaped, and where the zebra mussel shell
is flat where the two shells attach, the quagga mussel is rounded. Unlike the
zebra mussel, which has a dormant season, quagga mussels feed year around. For
many years the quagga mussel was not found in any inland lakes, possibly because
they tend to inhabit deeper waters than the zebra mussel. However, the quagga
mussel has found it’s way to Lake Mead, near Boulder City, Nevada, and
in Lake Havasu and Lake Mohave on the California/Arizona border. These are very
popular recreational sites – and WDFW boat inspectors have found boats
from Lake Mead and Lake Havasu at fishing tournaments in Washington State. Fortunately,
launch managers and National Park authorities at these areas are making certain
that boats leaving there have been inspected and cleaned.
WDFW has initiated
volunteer monitoring programs in several lakes and along the Columbia and Snake
rivers, and requires that out of state participants in fishing contests undergo
boat inspections. Washington State Patrol Commercial Vehicle Inspectors check
some of the boats that are commercially hauled into the state at the ports of
entry, but not all haulers are required to stop. WDFW is increasing boater education
efforts, and inspections of privately hauled recreational boats being transported
from out of state. It is
important that recreational boaters and anglers clean their boat and equipment
before moving from one waterbody to another.
For more information
on zebra mussels and quagga mussels visit:
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