Zebra mussels: the tiny threat that doesn't quit

Half an inch long, striped like a zebra, and capable of turning a dock into a gravel bed within a few seasons. Zebra mussels are one of the most consequential invasive species in North American freshwater — and, fortunately, one of the few where a single member habit does most of the work.

What they are

Zebra mussels (Dreissena polymorpha) are native to the lakes of Eastern Europe. They arrived in the Great Lakes region in the 1980s, likely in the ballast water of transoceanic freighters, and have since spread through connected waterways — and, more recently, through recreational boating. They're tiny (adults under about 2 cm), filter-feeders, and they reproduce fast: a single female can produce millions of larvae a year.

Why they're a problem

The mussels themselves are not toxic. The problem is what they do at scale:

• They colonize hard surfaces. Docks, boat hulls, water-intake screens, pump intakes, and even swimming platforms get encrusted. A heavily fouled intake can lose flow; a heavily fouled dock can become unusable.
• They outcompete native mussels. Native mussels are keystone species — they filter water and support a food web. Zebra mussels grow faster, reproduce more, and take the same hard surfaces.
• They change the water. By filtering so much of the water column, they can increase clarity and shift where algae and sediment end up — which sounds nice until you realize the whole food web has to adapt.
• They're extremely hard to remove once established. There is no practical "clean them out" at lake scale. Prevention is the only realistic play.

How they spread

Zebra mussels spread in two main ways:

1. Water movement — ballast water, connected waterways, and (importantly) live wells and bilge water in boats.
2. Hitchhiking on gear — the veligers (free-swimming larvae) and even adult mussels attach to hulls, trailers, nets, waders, and anything wet that gets moved from one lake to another.

The second vector is the one members control.

What members can do: Clean, Drain, Dry

The standard, DNR-recommended protocol — and the one we ask every member to follow:

1. Clean. Inspect your boat and gear before you launch and after you leave. Remove mud, plants, and anything attached. A quick hose-down at home is a good habit.
2. Drain. Drain all standing water from the boat, live wells, bilge, and any equipment (fins, life jackets, fish finders) before you transport to another lake. Zebra mussel veligers survive in water; they don't survive drying out.
3. Dry. Let gear air-dry fully before storing or transporting.

It takes five minutes. It is the single most effective thing a boater can do to stop the spread.

What the Association does

Beyond the member protocol, the Association's role is awareness, early detection, and coordination:

• Education. This page, the annual meeting, and the newsletter all carry the Clean/Drain/Dry message.
• Reporting. If you find a cluster of small striped mussels on a dock, intake, or rock — especially in a spot where you'd expect none — report it. Early detection is the only way containment is even possible.
• Supporting DNR-led actions. For confirmed detections, the DNR leads the response; the Association's role is to mobilize members and support local DNR-led actions.

Bottom line

Zebra mussels are not a "maybe someday" problem — they're a moving front, and recreational boating is their highway. The good news: the front is slow, and every member who Clean/Drain/Drys is a speed bump. If you find something that looks like a cluster of tiny striped mussels, don't scrape it off and go fishing — report it.