Invasive New Zealand mudsnails detected in east branch Au Sable River

June 9, 2016

For More Information:
Sarah LeSage, 517-243-4735,
Nick Popoff, 517-284-5830,

The DEQ and DNR recently received reports from Grand Valley State University confirming populations of invasive New Zealand mudsnails in the east branch of the Au Sable River near Grayling, Mich.

New Zealand mudsnails are considered an invasive species and are listed as a Prohibited Species in Michigan. These snails are only about 1/8 of an inch long and can be difficult to see. However, they often cluster in high densities and compete with native snails and other macroinvertebrates for food and space. Originally from New Zealand, the snails are now widespread in many western states and present in Wisconsin. They are easily transported and resilient, and can survive in damp environments for up to 26 days. Where established, these snails can dominate the bottoms of rivers and streams and exhibit invasive qualities, outcompeting and displacing macroinvertebrates that are vital as food sources for many fish species. In addition, these invasive snails have no nutritional value for fish.

Beginning this month, the DEQ and DNR will collaborate with partners to conduct surveys to determine the extent of New Zealand mudsnails in the Au Sable River and other rivers across the state.

New Zealand mudsnails were previously detected in August 2015 in the Pere Marquette river near Baldwin, Mich. Introductions of New Zealand mudsnails have been linked to recreational uses like fishing, since New Zealand mudsnails can easily hitchhike rides on recreational gear, especially waders.

Anglers and boaters on the Au Sable River and throughout the state are reminded to take steps to clean, drain and dry their equipment to help prevent the spread New Zealand mudsnails and other types of aquatic invasive species. Boaters are required by law to remove aquatic plants before launching, as well as to drain live wells, bilges and all water from boats before leaving the access site. Additionally, boaters and anglers are strongly encouraged to clean boats and equipment, including waders, with hot water or a diluted bleach solution, and allow them to dry for at least five days before reusing.

The DEQ and DNR are working together and with local partners to enhance awareness of New Zealand mudsnails and other aquatic invasive species. Anglers may encounter wader wash stations and signage at various locations encouraging them to take steps to limit the spread of aquatic invasive species.

For more information and to report new sightings of New Zealand mudsnails to the DEQ or DNR, visit or the Midwest Invasive Species Information Network at

The DEQ is dedicated to respect for Michigan’s citizens, stewardship of the environment, and support for a sustainable economy.