Aquatic Invasive Species

The Lake County Health Department monitors for aquatic invasive species in our local lakes. If uncontrolled, invasive species can harm our environment, health, and economy. Anyone who uses our lakes should do their part to stop the spread of invasive species.

Zebra Mussels

Zebra mussels (Dreissena polymorpha) get their name from the alternating black and white striped pattern on their shells. They have spread extensively in the Great Lakes region in the past decade. They attach themselves to any solid underwater object such as boat hulls, piers, intake pipes, plants, other bivalves (mussels) and even other zebra mussels.

These are the only officially documented occurrences of zebra mussels in inland lakes in Lake County.  However, the mussels have undoubtedly infested other County lakes but have probably gone unnoticed thus far.

Lakes with Discovered Zebra Mussels

Zebra Mussel
Year Lakes

Independence Grove Lake


Sterling Lake at Van Patten Woods, Fox Chain-O-Lakes, Gages Lake,
Lake Zurich, West Loon Lake, Lake Minear and Tower Lake


Bangs Lake, Cedar Lake, Third Lake


Druce Lake, East Loon Lake


Slocum Lake


Diamond Lake


Acorn Pond


Long Lake, Round Lake


Island Lake, St. Mary's Lake

Tips to Prevent Spreading

The following are some tips from the Great Lakes Sea Grant Network that can help prevent the spread of zebra mussels:

  • Always inspect your boat and boat trailer carefully before transporting. Studies have shown that transport via aquatic plant fragments is one of the major contributors to the spread of zebra mussels.
  • Drain all bilge waters, live wells, bait buckets, and engine compartments before entering another lake. Make sure water is not trapped in your trailer. Never transport water from one lake to another.
  • Flush clean water (tap) through the cooling system of your motor to rinse out any larvae.
  • Full-grown zebra mussels can be easily seen but cling stubbornly to surfaces. Boats that have been in the water for long periods of time should be carefully inspected. Carefully scrape the hull (or trailer), or use a high-pressure spray (250 psi) to dislodge them. Or leave your boat out of the water for at least 5 days, preferably up to 2 weeks. The mussels will die and drop off.
  • In their earlier stages, attached zebra mussels may not be easily seen. Pass your hand across the boat’s bottom - if it feels grainy, it’s probably covered with mussels. Don’t take a chance; clean them off by scraping or blasting.
  • Dispose of the mussels in a trash barrel or other garbage container. Don’t leave them on the shore where they could be swept back into the lake or foul the area.

The zebra mussel’s reproductive cycle allows for rapid expansion of the population. A mature female can produce up to 40,000 eggs in a cycle and up to one million in a season. Zebra mussels can live as long as five years and have an average life span of about 3.5 years. The adults are typically about the size of a thumbnail but can grow as large as 2 inches in diameter. Colonies can reach densities of 30,000 - 70,000 mussels per square meter.

Growth Cycle & Toll

Edging Out Native Species

Due to their quick life cycle and explosive growth rate, zebra mussels can quickly edge out native mussel species. Negative impacts on native bivalve populations include interference with feeding, habitat, growth, movement, and reproduction.

The impact that mussels have on fish populations is not fully understood. However, zebra mussels feed on phytoplankton (algae), which is also a major food source for planktivorous fish, such as bluegill. These fish, in turn, are a food source for piscivorous fish (fish-eating fish), such as large-mouth bass and northern pike.

Economic Concerns

In addition to the ecological impacts, there are also many economic concerns. Zebra mussels have caused major problems for industrial complexes located on the Great Lakes and associated bodies of water. Mussels can clog water intakes of power plants, public water supplies, and other industrial facilities. This can reduce water flow (by as much as two-thirds) to heat exchangers, condensers, fire fighting equipment, and air conditioning systems.

A Michigan-based paper company recently reported that it had spent 1.4 million dollars in removing only 400 cubic yards of zebra mussels. There is currently no widespread/whole lake control practice that would be effective without harming other wildlife, and there does not currently appear to be an effective predator of the mussel.