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Dreissena polymorpha

THE CRIMES: Creates problems in the food web by decreasing food supplies for native fish. Can kill native mussels, including rare or endangered mussels.
Filters water so well that algae can get out of control Creates expensive cleanup and repair by clogging water intakes and boat motors.

DESCRIPTION: Fingernail-sized, freshwater mollusks with a striped pattern on both shells (a bivalve). Can grow up to 2.54 cm (1 inch) in length. They use sticky, byssal threads to attach to hard and soft surfaces.

The Interrogation
Where are you from?
I came from the Caspian and Aral seas in Eastern Europe and Western Asia.
How did you get here?
I came over as tiny larvae in the ballast water of ships that traveled from freshwater ports thousands of miles away. Once these ships reached the Great Lakes, the ballast water was dumped out and we were deposited as hitchhikers to this new freshwater system. Now that we’ve spread throughout the Great Lakes, we’re also good at getting into your rivers and inland lakes. We cleverly attach in clusters to your boats or might be tiny larvae hiding in bait buckets. Then when you move to another waterway without cleaning us off we get to colonize a new body of water. We also can stick onto aquatic plants. When these plants get accidentally entangled on boat motors or trailers we ride along until we’re put into a waterbody that is new to us.
What’s your problem?

We have a real knack for attachment and because we can cluster together in large numbers we’re famous for clogging intake pipes, boat motors, pumps, etc. These can be very expensive to clean and repair, especially if we get into your water treatment and power plant facilities. Sometimes we kill your native mussels by suffocating them. This is especially bad when the natives are rare and endangered.

Since we filter water by feeding on microscopic plants and animals such as phytoplankton, the water’s gotten much clearer. This might sound good, but more sunlight can get through and then loads of new vegetation can grow like blue-green algae. Also since we are decreasing the food supply for lots of native fish, the food web can be in trouble.

If you see our shells washed up on your beach, you’ll notice that we are quite sharp and can easily cut your skin. This creates problems with your opportunities to enjoy swimming at your favorite beach.

How can we control you?
If we’re not in bodies of water around you, keep an eye out for us and notify your local natural resource agency to report any colonies that you see. Scuba divers need to clean and dry their equipment too, if they want to keep us out of small inland bodies of water like filled-in quarries. If you have a boat, it’s real important to inspect the whole boat and its trailer and remove any plants and animals. You should drain on land all the water from the motor, livewell, bilge and transom well. Be sure to also empty water from your bait buckets only on land. Then dispose of unwanted bait in the trash. After you leave a boat launch don’t forget to wash all the equipment with 104 degree water or dry your equipment for at least five days before going to a new waterbody. That’ll really help keep us from spreading.
Reward: The honor of protecting our water resources— A healthier environment and more opportunities to enjoy our natural areas.