Invasive New Zealand mudsnails turn up in Kent County’s Bear Creek, the first find in southern Michigan: what anglers and paddlers should do

GRAND RAPIDS — A tiny invasive snail that can blanket a streambed has been found in Kent County, the first time it has turned up in the southern half of the Lower Peninsula, state officials said.

New Zealand mudsnails were found in Bear Creek, a small coldwater tributary of the Thornapple River, the Michigan Invasive Species Program said Monday, Nov. 2. The site is about 75 miles south of the closest known infestation, in the Pere Marquette River. CBS Detroit described the creek’s location as southeast of Grand Rapids.

Volunteers with the Coldwater River Watershed Council collected the snails during routine monitoring of aquatic insects and other small bottom-dwelling creatures, which serve as a check on stream health. The group sent photos to the Michigan Department of Environment, Great Lakes, and Energy, and experts from Oakland University and Trout Unlimited verified the find.

Why one snail is a problem

The snail is brown to black and about one-eighth of an inch long. It is prohibited in Michigan. All of them are female, and they develop complete embryos without fertilization, so a single snail can start a whole population, the state said. One snail can produce more than 200 young a year, and researchers in some Western states have counted densities of 300,000 per square meter.

That crowds out the mayflies, caddisflies and other insects that trout and other sport fish eat. Fish will eat the mudsnails, but the thick shell, which closes with a tight “hatch,” makes them hard to digest and low in nutrition, and some pass through alive. The state said that can reduce the growth, condition and eventually the number of fish such as trout.

It is the second time in a few weeks that state biologists have asked West Michigan anglers for help; in October the DNR asked Muskegon River anglers to release tagged lake whitefish.

Because the snails reproduce by cloning, Oakland University will run genetic tests on the samples to try to find where they came from.

Where else they live

Mudsnails were first found in Michigan in 2015. They now live in the Au Sable, Boardman, Grass, Pere Marquette, Pine and Upper Manistee rivers in northern Michigan, according to the state.

State biologists plan more sampling at the Bear Creek site and in other Thornapple River tributaries in Barry, Kent and Ionia counties. Signs will go up at recreational access points on affected creeks and rivers. The program will work with the Coldwater River and Thornapple River watershed councils and local invasive species groups to spread the word.

What you can do

There is no effective treatment to control or eradicate the snail, so prevention falls on the people using the water. After any trip to a lake, river or stream, clean, drain and dry your boat, trailer and gear before going somewhere new, the state said.

The snails are small enough to hide in mud and plant bits, so check poles, nets, waders, boots, buckets, kayaks, canoes and life jackets. “Anything that has been in the water or at the water’s edge should be inspected before it is packed or loaded,” the release said. Information on the snail and how to report a suspected sighting is at Michigan.gov/Invasives.

Sources:
Michigan Invasive Species Program, “Invasive New Zealand mudsnails detected in southern Michigan” (Nov. 2, 2026; Bear Creek find, verification, biology, rivers, sampling plans, prevention), https://www.michigan.gov/invasives/news/2026/11/02/invasive-new-zealand-mudsnails-detected-in-southern-michigan
Michigan DNR news release via GovDelivery (Nov. 2, 2026; same release with reproduction and fish-impact details), https://content.govdelivery.com/accounts/MIDNR/bulletins/4315154
CBS Detroit, “Michigan DNR asks boaters to be on the lookout for invasive snail species” (Nov. 2, 2026; location southeast of Grand Rapids), https://www.cbsnews.com/detroit/news/michigan-dnr-asks-boaters-to-be-on-the-lookout-for-invasive-snail-species/
Photo: Judi Lapsley Miller, “Two Potamopyrgus antipodarum on a māhoe leaf 1.jpg,” Wikimedia Commons (CC BY 4.0), https://commons.wikimedia.org/wiki/File:Two_Potamopyrgus_antipodarum_on_a_m%C4%81hoe_leaf_1.jpg

Grand Rapids

Tags: New Zealand mudsnail · Invasive species · Bear Creek · Thornapple River · Michigan DNR · Fishing