Zebra mussels (Dreissena polymorpha) are recent invaders in waterways across the United States.
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Zebra mussels (Dreissena polymorpha) are recent invaders in waterways across the United States. They were accidentally carried from Russia to North America in ballast water in commercial ships. Since their discovery in Lake St. Claire in 1988, they have spread to all of the Great Lakes and are now in over 25 states. The estimated cost of controlling zebra mussels in the Great Lakes ranges from $100 million to $400 million annually.

In 2009, ecologists identified zebra mussels in DuPage County in Deep Quarry Lake at West Branch Forest Preserve in Bartlett. Boaters and anglers most likely released them into the lake accidentally. As a result, the lake has been closed to boating indefinitely to prevent any further spread.

Adult zebra mussels have 1- to 1.5-inch-long striped shells. They can live up to 5 years, depending on conditions, but reach sexual maturity during their first year. They reproduce when the water gets above 54° F. One female can produce up to 1,000,000 eggs in one breeding season. The fertilized eggs quickly develop into microscopic free-swimming larvae called “veligers,” which cannot be seen by the naked eye. (This makes veligers proficient hitchhikers.)

As zebra mussels grow, they need to attach to hard surfaces, or they will die. They attach using “byssal threads.” The threads are located on the hinged edge of the mussel’s shell. They are a liquid protein that is secreted by a gland and injected along a groove in the mussel’s single foot. When the protein touches a hard surface, it hardens and becomes an anchor for the mussel. The foot releases the thread and retreats back into the shell. A zebra mussel will repeat this process over and over to reinforce its grip. Even as veligers, zebra mussels can hitch a ride on recreational gear — boats, oars, bait buckets, etc. — rocks, wood, native mussels and plants, even each other, easily infecting new lakes or rivers.

Zebra mussels are highly efficient filter feeders. Just one adult can filter the microscopic plants and animals from 1 quart of water in one day; one colony can clear an entire lake. This leaves little food for small native animals, such as zooplankton and small fish, whose populations tend to decrease. Populations of larger fish, which feed on the smaller fish, also decline.

Zebra mussels clear the water to such an extent that light-sensitive fish, such as walleye, may move to deeper waters. Aquatic plant beds may grow denser and at greater depths, which may create habitat for small fish but may also prevent larger predators from finding food. The dense beds can also cause problems for boaters and anglers and alter aquatic environments.

After zebra mussels die, their decaying bodies create foul odors, and their sharp shells pile up on shorelines.

Known Zebra Mussel Locations in DuPage County
• Deep Quarry Lake at West Branch Forest Preserve in Bartlett
• Bass Lake at West Branch Forest Preserve in Bartlett
• Mallard Lake at Mallard Lake Forest Preserve in Hanover Park
• Eagle Lake at Hidden Lake Forest Preserve in Lisle 

Protect Your Waters

  • Drain and remove all water, mud, plants and animals from all equipment before leaving the shore.
  • Don’t dump bait! Dispose of bait and bait water in the trash or on the ground far from shore.
  • Wash and dry anything that comes in contact with the water — boats, trailers, tackle, clothes, pets. Use hot water over 104° or a power washer. If possible, let it dry for five days before entering new waters.
  • Never put plants or animals in a body of water unless they came out of that body of water.
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