Exotic, invasive snail found in two new streams

Anglers cautioned to take steps to prevent further spread

MADISON — New Zealand mudsnails, an invasive snail previously only found in two Dane County locations, have recently been verified in two new streams – Mt. Vernon Creek in Dane County and Rowan Creek in Columbia County.

New Zealand mudsnails have been found in two new streams. - Photo credit: DNR
New Zealand mudsnails have been found in two new streams.Photo credit: DNR

Mt. Vernon Creek, located in southwest Dane County, is a tributary to the Western Branch of the Sugar River and is a Class 1 trout stream. Rowan Creek in Columbia County near Poynette is a Class 1 and Class 2 trout stream. Stream biologists and volunteers discovered the snails during routine stream sampling.

The New Zealand mudsnail is an NR40 prohibited invasive species, meaning that it is absent from Wisconsin or found in only a few locations. The small snail can establish large populations that can outcompete native stream insects that serve as food for fish and change the nutrient flows in streams. However, it is uncertain what impacts this invasive species will have on streams in Wisconsin.

All of the locations where New Zealand mudsnails have been found in the state are popular for fishing and may also be used by paddlers, trappers and hikers.

All water users play an important role in preventing the spread of the New Zealand mudsnail and all other aquatic invasive species. Anyone can prevent the spread of invasive species by following the Stop Aquatic Hitchhikers guidance of:

  • INSPECT your equipment, including waders, nets, and fishing gear, boats and trailers
  • REMOVE any attached aquatic plants or animals
  • DRAIN all water from boats and equipment; and
  • NEVER MOVE live fish away from a waterbody.

People who wade streams for any reason can also use a brush to scrub their boots and waders and then rinse thoroughly with tap water away from the stream. Freezing gear for at least eight hours will further reduce the risk of transporting New Zealand mudsnails to other streams. By performing these prevention actions water users can further protect our waters and stop the spread of invasive species.