Potential Aquatic Invasive Species Threats

There are a number of aquatic invasive species that pose direct threats to the inland lakes in Calumet County as well as Lake Winnebago, but do not seem to have arrived yet. A few of the potential future invasive species are listed below. For information on possible invasive aquatic plants, there is a very good publication produced by the Midwest Invasive Plant Network.

Banded Mystery Snails Waterflea
Quagga MusselsRound Goby

Banded Mystery Snails

The banded mystery snail is not found in Calumet County, but they are confirmed in Manitowoc County. The banded snails are in a few lakes in Manitowoc County, and as near to Calumet as Bullhead Lake. They do not seem to be in Long Lake yet. If you trailer your boat between Bullhead Lake and Becker Lake, clean all your equipment very carefully and do not move any plant material or water between the two lakes. In fact, since other lakes in Manitowoc County have these snails, if you recreate on any of their lakes, be very careful not to bring these invasive species back to Calumet. Not only is cleaning your equipment the right thing to do, it's the law and fines will be issued.

Banded Mystery Snails


Banded mystery snails are non-native snails that are found in an increasing number of Wisconsin lakes. There is not a lot yet known about these species, but they seem to have a negative effect on native snail populations. Piles of dead snail shells litter beaches making them unpleasant, much like zebra mussels.

Fish Hook and Spiny Waterfleas

Fish hook and spiny waterfleas have been a problem in Lake Michigan for quite a while. A few years ago, they were found in two water bodies in Vilas County. In 2009 large populations were found in Lake Mendota and Lake Monona in Dane County. We do not want to spread these invasive species to Lake Winnebago or our other inland lakes.



Both waterfleas are only about ¼ to ½ inches in length and individual waterfleas may go unnoticed. However, both species tend to gather in masses on fishing lines and downrigger cables, making them quite messy, so anglers are often the first to discover a new infestation.

Spiny and fishhook waterfleas eat zooplankton, putting them in direct competition with juvenile fish for food. Young fish have trouble eating these waterfleas due to their long, spiny tails.

Fishing, boating, and other water recreational equipment can transport spiny waterfleas and their eggs to new water bodies. Their resting eggs can survive long after the adults are dead. Great care must be taken not to transport water between water bodies and to remove all waterfleas and eggs from all equipment.

Quagga Mussels

Quagga mussels are a tremendous problem in Lake Michigan. They are closely related to the zebra mussel, but since quaggas like silty or sandy lake bottoms and can live in waters ranging from warm and shallow to deep and cold, they can thrive in areas that zebra mussels cannot.

Quagga Mussels


The quagga mussel looks a lot like a zebra mussel, but its shell has a rounded angle instead of the flat ventral side of the zebra mussel. A quagga mussel feeds all year, even in winter when its cousin the zebra mussel is dormant. Some researchers believe that Lake Erie's dead zone is likely the partial work of the quagga mussel's non-stop feeding, its ability to live in deep water, and the excretion of phosphorous with its waste. It is certainly contributing to the cladaphora problem along the shores of Lake Michigan.

Because quagga mussels prefer silty and sandy bottomed lakes, they may be able to successfully invade inland lakes with those characteristics, including some lakes not suitable for zebra mussel establishment.

Round Goby

The round goby is currently angering anglers in Lake Michigan and the Bay of Green Bay. Anyone who has tried to ice fish in areas where there are round gobies knows what nasty, bait stealing fish they are.

The round goby is a bottom dwelling fish with a large head and can grow to be 10 inches. Round gobies are thriving in the Lake Michigan because they are aggressive, voracious feeders and can forage in total darkness. The round goby takes over prime spawning sites traditionally used by native species, competing with native fish for habitat and changing the balance of the ecosystem.

If you catch a round goby, DO NOT THROW IT BACK ALIVE.

Round Goby



The ruffe is another aquatic invasive species in Lake Michigan that we must keep out of our inland lakes. The ruffe is a member of the perch family and could be confused with young native fish such as yellow perch and walleye. Ruffe are 4 to 6 inches in length and tend to be quite spiny, which helps distinguish them from other species. Ruffe compete with native fish for food and habitat, and populations have the potential to increase rapidly.

If you catch a ruffe, DO NOT THROW IT BACK ALIVE.