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Frequently asked questions

Aquatic and Wetland

What are aquatic invasive species?

Aquatic Invasive species are plants, animals and pathogens that are "out of place." A species is regarded as invasive if it has been introduced by human action to a location, area, or region where it did not previously occur naturally (i.e., is not native), becomes capable of establishing a breeding population in the new location without further intervention by humans and spreads widely throughout the new location.

Why are aquatic invasive species a problem?

Aquatic invasive species often leave their predators and competitors behind in their native ecosystems. Without these natural checks and balances they are able to reproduce rapidly and out-compete native species. Once established they can alter ecological relationships among native species and can affect ecosystem function, economic value of ecosystems and human health.

How do they become a problem?

Humans have created conditions where plants and animals can aggressively invade and dominate water bodies in three ways:

  • Introducing exotic species (from other regions or countries) who lack natural competitors and predators to keep them in check.
  • Disrupting the delicate balance of native ecosystems by changing environmental conditions (e.g., stream sedimentation, ditching, building roads) or by restricting or eliminating natural processes (e.g., fire). In such instances, even some native plants and animals can become invasive.
  • Spreading invasive species through various methods. Some examples:
    • Moving watercrafts from waterbody to waterbody without removing invasive plants and animals or draining water
    • Moving live fish from a waterbody
    • Releasing live non-native animals and plants into the wild
    • Carrying seeds of invasive plants on footwear or pet’s fur

I found a new aquatic invasive species not known to occur in my lake, wetland or stream

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How does the DNR control aquatic invasives?

Clean Boats, Clean Waters Watercraft Inspection
Through the Clean Boats, Clean Waters program, inspectors are trained to organize and conduct a boater education program in their community. Adults and youth teams share information with boaters and anglers about what invasive species look like and what precautions they should take to avoid spreading them. Inspectors demonstrate how to take proper steps to clean boats, trailers and equipment, as well as perform boat and trailer checks for invasive species. They also distribute informational brochures and are encouraged to help monitor for aquatic invasive species.

Supported by the Wisconsin Lakes Partnership, this program offers training on how to organize a watercraft inspection effort, how to inspect boats and equipment and how to interact with the public. Trainings are open to adults and youth.

Contact Erin McFarlane, Statewide Clean Boats, Clean Waters Educator for Extension Lakes for more information: 715-346-4978 or

This effort involves monitoring for aquatic invasive species, including zebra mussels, Eurasian water milfoil, spiny waterfleas and rusty crayfish. For zebra mussels, it involves collecting samples for veliger (larval zebra mussel) analyses and deployment of substrate samplers. There are also specific sampling procedures for spiny waterfleas and rusty crayfish.

Information and education
In close cooperation with UW Extension and Wisconsin Sea Grant, education efforts focus on working with resource professionals and citizens statewide to teach boaters, anglers and other water users the steps to take to prevent transporting aquatic invasives to new waters. Efforts also involve addressing other potential mechanisms of introduction, including aquarium pet release and water gardening. Many educational tools are used to reach the public - brochures and publications, watch cards and wild cards, public service announcements and displays at parks, sport shows, convention and symposiums.

Purple loosestrife biological control
A citizen-based project that emphasizes using two safe, purple loosestrife foliage-feeding beetle species, in combination with traditional methods, for controlling this invasive plant. Citizens of all ages make up the backbone of this cooperative program by rearing and releasing these insects in their local wetlands - and learning about these precious places in the process. Learn how to participate!

Contact the Statewide Purple Loosestrife Biocontrol Coordinator for more information: 608-266-0061 or

What can we do about them?

Controlling invasive species is difficult and costly, and eradicating them is often impossible. Whenever possible, preventing invasive species from arriving in the first place is the best option. DNR staff monitor the presence and spread of invasive species, work with partners to educate the public and research control methods. But citizens also play a key role in the campaign against invasive species. Here’s what you can do to help us fight these invaders.

How can I become a watercraft inspector?

Lake property owners, lake enthusiasts and concerned citizens can help prevent zebra mussels and other invasive species from infesting their favorite lakes by attending a training in the spring or summer to learn how to become a watercraft inspector. Participants in the trainings will learn about invasive species and how to help boaters check their boats for the most common places that invasive species stow away on boats, boat trailers, bait buckets and other water recreation equipment. There are several resources available to inspectors, including a kit full of educational and other materials that can help them start inspection programs in their communities.

The most common way that zebra mussels, Eurasian watermilfoil and other aquatic invasive species get introduced to new lakes and become established is being transported aboard boats, boat trailers, bait buckets, or in bilge water. Wisconsin's Clean Boats, Clean Waters (CBCW) watercraft inspection program is a key part of the state's prevention strategy for the one-on-one educational opportunities they offer. To see how many boats have been inspected, the number of people our watercraft inspectors have contacts and how many hours were spent conducting inspections at boat landings around the state, visit the Watercraft Inspector Summary webpage. Wisconsin’s dedicated watercraft inspectors are putting forth tremendous effort each year.

To learn more about the CBCW program, visit the Clean Boats, Clean Waters website [exit DNR] or contact your local Aquatic Invasive Species Coordinator.

Are there zebra mussels in the St Croix River?

In 1998, the National Aquatic Nuscience Species (ANS) Task Force [exit DNR] approved an interstate ANS plan on the St. Croix National Scenic Riverway. The plan was prepared jointly by Minnesota, Wisconsin and the tribes. It has provided federal funding to each state for $20,000 and to the tribes for $2,500. The federal dollars have been used to protect the St. Croix River against the introduction of zebra mussels.

Specific actions have been aimed at enforcing state ANS laws on the St. Croix, monitoring for zebra mussels via dive searches and veliger plankton tows and information/education efforts such as posting signs and providing information to boaters at the water access sites.

A state law that was enacted in 1996 prohibits the placement of any boat, trailer or equipment in the Lower St. Croix if there is reason to believe that zebra mussels are attached. The regulations address the risk to several endangered natural mussel species in the St. Croix River if zebra mussels colonize upstream of the Mississippi River.

Are biological controls dangerous to the environment?

Although it's true that early experiments with biological controls often ended worse than they began, modern day testing of the control organism ensures that the cure won't be worse than the disease.

Last revised: Monday March 16 2020