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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?

Watercraft Inspection
This effort involves dissemination of information to anglers and recreational boaters to make them aware of what invasive species look like and what precautions they should take to avoid spreading them. It also involves visual inspection of boats to make sure they are "clean" and demonstration to the public of how to take the proper steps to clean their boats, trailers, and boating equipment. Watercraft inspectors also install signs at boat landings informing boaters of infestation status, state law, and steps to prevent spreading invasives.

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.

Contact Brock Woods, UWEX/DNR Purple Loosestrife Bio-control Coordinator for more information: (608)266-2554 or

Clean Boats, Clean Waters Volunteer program
Sponsored by the DNR, UW Extension, and the Wisconsin Association of Lakes, this program offers training on how to organize a watercraft inspection program, how to inspect boats and equipment, and how to interact with the public. Volunteers are also encouraged to help monitor for aquatic invasives. Workshops are open to adults and youth; adult groups are encouraged to work with local youth partners. Contact Erin McFarlane, Volunteer Coordinator for the Invasive Species Program (715) 346-4978 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 volunteer 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 one of workshops statewide in the spring and summer to learn how to become a volunteer watercraft inspector.

Participants in the workshops 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. They'll also receive a kit full of educational and other materials that can help them start volunteer inspection programs in their communities.

The most common way that zebra mussels, Eurasian water-milfoil and other invasive aquatic species get introduced to new lakes and become established is being transported aboard boats, boat trailers, bait bucketsor in bilge water. Those two invasive species aren't the only threats, but are among the most common.

Wisconsin's watercraft inspection program, which includes a small corps of paid seasonal watercraft inspectors and volunteers, are a key part of the state's prevention strategy for the one-on-one educational opportunities they offer.

Last year, the Clean Boats, Clean Waters program trained more than 350 volunteers in 38 counties. As of February 2005, volunteers had spent 1,103 hours at boat launches, contacted more than 5,000 boaters, and helped them inspect more than 2,400 boats.

To register for a workshop or learn more about them, email Laura Felda-Marquardt, or contact her by telephone at DNR Rhinelander Service Center, 715-365-2659, or visit the UW Extension web site [exit DNR] for a current list of workshops.

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: Friday May 10 2019