New Zealand mud snails discovered in Black Earth Creek

First occurrence in inland Midwest

MADISON – The invasive New Zealand mud snail that has been a problem in western U.S. streams has been detected in Black Earth Creek, a renowned trout stream in Dane County.

The discovery, the first in an inland Midwestern stream, is spurring the state to begin rapid response procedures to try to contain the snail, and to call on waterfowl hunters, trappers anglers and hikers to take precautions to avoid accidentally spreading the species.

“This is a significant and disappointing find in Wisconsin,” says Bob Wakeman, who coordinates the Department of Natural Resources aquatic invasive species efforts. “The New Zealand mud snail can be extremely prolific, has altered the food chain and may be having an impact on fish populations in Western streams.”

“We don’t know what the impact will be in Wisconsin, but we do know that there is no good way to eradicate the snails so we are focusing on containing them as quickly as we can and ask for citizens’ help in doing that as well.”

Wakeman says DNR has notified partners of the discovery, and will work with citizens, the River Alliance of Wisconsin, Trout Unlimited, University of Wisconsin-Extension, Wisconsin Sea Grant and Dane County to contain the species through increasing awareness of prevention steps among those who might inadvertently help spread the snail: hunters, anglers, trappers and hikers.

Signage, and wash stations along the area where the invasive species has been detected are among the educational efforts likely to be used, Wakeman says.

The department’s discovery of the snail during routine monitoring for aquatic invasive species was confirmed earlier this month by Dr. Kathryn Perez from University of Wisconsin-La Crosse, who identified all individuals in the samples as belonging to the “Clone 1” population, previously found only in the western states as far east as Colorado. A “Clone 2” population also exist in the Great Lakes, which arrived by ballast water.

The New Zealand mud snail, the size of a grain of sand, has a black and brown shell and is capable of reaching high densities – up to 500,000 per square meter. The snails outcompete native insects that are food for fish and other aquatic life but are not good food sources themselves.

The snails are listed as a prohibited species in Wisconsin, meaning it’s illegal to buy, sell, possess or transfer them without a permit.

Although trout season on the creek has closed for winter, hunters, hikers and trappers visiting the Driftless area should take care to review gear disinfection protocols – particularly for waders, where the tiny snails can cling to rubber or mud.

“This is why it’s so important to clean your equipment before leaving a lake or stream — and ask your friends and guests to do the same,” Wakeman says. “We need everyone’s vigilance to help contain this invasive species.”

Take these prevention steps after leaving the water to keep Wisconsin streams healthy:

  • Inspect and remove all mud and debris that might harbor snails from your boots, waders, boats and other gear with a stiff brush. If possible, rinse with tap water before leaving the river. If you are going home, let your gear freeze for 6-8 hours or dry it in a warm place (85 degree Fahrenheit) for 24 hours to kill mud snails.

  • Drain water from boat, motor, bilge, decoys and other water containing devices before leaving water access (before launching, after loading and before transporting on a public highway).

FOR MORE INFORMATION CONTACT: Bob Wakeman,  262-719-0740 ; David Rowe  608-275-3282