top of page



The best way to keep aquatic invasive species (AIS) from being introduced to Green Lake is to inspect every boat that enters Green Lake for any plants or debris, and to wash each boat when possible. (Learn more about AIS below.)


That's why we've installed an automated boat wash station at Dodge Memorial County Park. This boat wash station is a pilot project, with the goal of learning from this site and expanding the number of boat wash stations around Green Lake in the coming years, which will help build an additional line of defense for our lake.

To encourage use of the boat wash station, boaters who wash their boat before entering Big Green Lake at Dodge Memorial County Park and complete this survey are eligible to win a $500 cash prize. Each boat wash station use provides another chance to win. (See terms & conditions here.)


Thank you to our partners who help make this possible!

GLA_Logo_Vertical_withTag_Care4ourLake (1).jpg
Protecting Green Lake from Invasive Species

Protecting Green Lake from Invasive Species

Play Video

Aquatic invasive species (AIS) are plants, animals, or pathogens that are introduced by human action to an area where they do not naturally occur. Once they establish breeding populations, they spread rapidly in their new environments. AIS lack natural predators and competitors, which contribute to their population explosions. 

Green Lake already has six damaging culprits that the GLA is aware of—zebra mussels, Eurasian watermilfoil, curly-leaf pondweed, rusty crayfish, carp, and purple loosestrife—each introducing their own set of challenges to our lake. Learn more about each below.


With thousands of boats visiting Green Lake every summer, there is an urgent need to be proactive against aquatic invasive species. 

zebra1 .jpg


Zebra Mussels (Dreissena polymorpha) – small, fingernail sized organisms that can attach to any hard surface in water. Adults are approximately 1/4 inch to 1 1/2 inches long, and feature D-shaped shells with alternating yellow and brownish stripes.


Native to Eastern Europe, zebra mussels were first introduced into the Great Lakes through ballast water that was drained from international cargo ships. As effective filter feeders, they can remove large levels of plankton and other small organisms, creating increased water clarity levels. However, increased water clarity is not always an indicator of a healthy ecosystem, and the increased clarity can cause increased aquatic plant growth, creating an imbalanced ecosystem.

Eurasian water milfoil.jpg


Eurasian Watermilfoil (Myriophyllum spicatum) – once commonly sold as an aquarium plant, this invasive species was first introduced as early as the 1940’s. Similar in appearance to northern watermilfoil, a native species, Eurasian watermilfoil can be best identified by counting the number of leaflets. Eurasian watermilfoil will have 12 or more leaflets, compared to the 6 or less on native species.


Once established, Eurasian watermilfoil can quickly become the dominant plant in a local ecosystem, blocking sunlight from native species and spreading easily from one area to another. Often introduced by boaters who go from one boat landing to another without properly cleaning and removing plant debris from boats and trailers.

Curly leaf pondweed.jpg


Curly-Leaf Pondweed (Potomogeton crispus) – often the first pondweed to appear in spring, Curly-Leaf Pondweed thrives in cold waters, such as those found throughout Wisconsin and other Midwestern states. Due to its preference for cold water, Curly-Leaf Pondweed begins growing while ice may still cover most lakes, gaining a head start over other native plants. This unique life-cycle allows it to outcompete native plants for resources, but it also means that it dies off earlier than most other species.


This creates a unique problem because the decomposition of Curly-Leaf Pondweed in late summer can decrease dissolved oxygen levels, destroying native fish populations. In addition it can create a sludgy mess that is a headache for boaters and lakefront home owners.



Rusty Crayfish (Orconectes rusticus) – once commonly used by anglers as an excellent fishing lure, the Rusty Crayfish has now been effectively introduced throughout the Midwest. Dominant and aggressive, these crustaceans will outcompete other species for resources, devastating the natural food chain and degrading overall biodiversity.

While it is now prohibited to use Rusty Crayfish for fishing, capturing them is encouraged, so long as they are not introduced into another body of water. They are edible and make a scrumptious meal when prepared in a variety of ways. Plus, you have the added benefit of removing them from areas that they would otherwise negatively impact!

purpleloosestrife 2.jpg


Purple Loosestrife (Lythrum salicaria) – a wetland plant from Europe and Asia, purple loosestrife was first introduced as an ornamental landscape plant. Having no native predators or diseases to control its population, and with each plant producing over 1 million seeds per year, Purple Loosestrife spread broadly across the United States.

Having established itself as a dominant species in many wetlands, Purple Loosestrife damaged habitats that were vital to other plants and animals. Thankfully, it was discovered that beetles that were native to the same region that Purple Loosestrife originated, could be bred and released, destroying many of the plants while leaving native species alone. The Purple Loosestrife eating organisms, Galarucella beetles, are often bred and released as part of a control program in Green Lake County.



Carp (Cyprinus carpio) – carp destroy important vegetation, stir up the lake bottom, fuel algae growth,and muck up the water. Every spring, the GLA joins forces with our partners to remove invasive carp that harm the health of the lake. Fewer carp means a lake that is better protected against nutrient and phosphorus pollution.

How did they get here? In the 1800's the U.S. Government introduced carp to many lakes seeing them as a cheap and easy food source. However, the carp population soon grew out of control since one female carp can lay one million eggs per year!



Spiny waterfleas are tiny creatures that can grow to about half an inch long and look almost see-through. They have a long spine that looks like a tail, with additional spines along the edges. 

Spiny waterfleas eat tiny animals called zooplankton, impacting the whole food chain. This can lead to big problems, like blue-green algae blooms, which can harm both animals and humans. 

Spiny waterfleas are often noticed by fishermen on fishing lines because they can create a clear, gelatin-like mass. Spiny waterfleas can be transported in minnow buckets, live wells, or bilge water, or on nets and anchor lines. Their eggs can be transported in the mud on anchors or other boating gear.  


Even though they're small, spiny waterfleas can cause a lot of damage. For example, once introduced to Madison’s Lake Mendota, spiny waterfleas caused $80 million to $160 million in water quality damage.   



Starry stonewort is a non-native species of large algae that can grow to more than six feet tall.  

When it grows, starry stonewort makes thick mats of plants that can crowd out other plants in the water. This can make it hard for people to swim, fish, or do enjoy other activities in the lake. 

The best way to prevent the spread of starry stonewort is to wash your boat and equipment before leaving and entering any lake. 



Quagga mussels are a type of small invasive creature that are very similar to zebra mussels. Both types of mussels can cause big problems in our lakes and rivers. 

Quagga mussels are "filter feeders," which means they eat tiny things in the water, like algae. But when there are too many quagga mussels, they can eat so much algae that there's not enough left for other animals to eat. This can disrupt Green Lake’s whole food chain. 

Just like zebra mussels, quagga mussels can attach to boats, pipes, and other things in the water. This can make it hard for people to go boating or fishing. 

If we all work together to keep our boats and equipment clean, we can help stop these mussels from causing more problems in our lakes and rivers. 



Faucet snails are small creatures that live in the water. They're about half an inch big and have a light brown to black shell. The opening of the shell is on the right side and it's less than half the height of the shell. 

Faucet snails can be a problem because they can carry parasites that can make waterfowl, like ducks, really sick. These parasites can even kill the birds.  

To stop faucet snails from spreading to new lakes and rivers, we need to be really careful with our boats and other equipment. Faucet snails can be transported in things like boats, trailers, anchors, and duck decoys. They can even survive for up to a month in dry mud! Cleaning equipment really well before moving it from one place to another can help keep the snails from spreading and causing more problems. 



The round goby is a small, tough fish that usually grows to be about three to six inches long, but can be as big as ten inches. When they're young, they're solid gray, and when they're adults, they're light gray with dark blotches. 

Round goby can hurt native fish populations by taking away their food and places to lay their eggs. Round goby can even eat the eggs of other fish! 


It’s important to clean, drain, and dry your boat and all of your equipment before moving to a new lake or river to help stop the round goby from spreading. 

bottom of page