Invasive New Zealand mudsnails have been detected in a Michigan creek, the sixth known infestation in Michigan in recent years.
The Michigan DNR said the mudsnails were found at the mouth of Shanty Creek, a tributary of the Grass River in Antrim County during routine monitoring in May and confirmed through DNA analysis in August.
New Zealand mudsnails were first discovered in the United States in Idaho’s Snake River in 1987. Since then, the snails have spread throughout the western states and into areas of the Great Lakes by attaching themselves to boats, waders and equipment.
The Grass River is now the sixth river system in Michigan known to be infested by the mudsnails. Their discovery in the Pere Marquette River in August 2015 signaled the first detection in a Michigan inland waterway. In 2016, populations were confirmed in the Boardman and Au Sable rivers. By 2017, the invasive snails were found in the Upper Manistee and Pine rivers.
Michigan’s salmon season, which peaks in September and October, draws thousands of anglers to Michigan’s premier rivers.
This brown to black, one-eighth-inch long mudsnail, a native of New Zealand, is considered invasive and is prohibited in Michigan due to the environmental harm it can cause to rivers, streams and lakes. Because the snail reproduces by cloning (females develop complete embryos without fertilization), a single snail can start an entire population.
One snail can produce over 200 young in a year. Since few natural predators or parasites of this species exist in North America, their numbers grow rapidly each year. In some locations in western states, researchers have documented snails reaching densities of 300,000 per square meter. With that many mudsnails, food for other stream invertebrate populations can become scarce.
“This is a time when people are likely to visit multiple rivers and streams over a few days,” said Lucas Nathan, Michigan Department of Natural Resources aquatic invasive species coordinator. “If they are not cleaning equipment thoroughly each time, there is a potential to introduce New Zealand mudsnails into new waters.”
DNR offices across the state, along with other volunteer organizations, are constantly monitoring for the mudsnails and other invasive species.
“The Michigan Invasive Species Grant Program has been instrumental in fostering the development of CISMAs across the state, creating a network of local invasive species resources,” Nathan said. “At the same time, the grant program supports research efforts like Oakland University’s New Zealand mudsnail project, which has raised awareness among anglers, trained citizen scientists and developed an important partnership with Trout Unlimited, which helped to initiate the New Zealand Mudsnail Collaborative.”
The Michigan DNR is asking anyone who visits the state’s lakes, rivers or streams, to be sure to clean, drain and dry your boat, trailer and equipment.
The New Zealand mudsnail’s small size requires careful examination and cleaning of places where plants, mud or debris can be found on poles, nets, waders, boots, buckets, kayaks, canoes and flotation devices. Anything that has been in the water or at the water’s edge should be inspected before it is packed or loaded.
The NZMS Collaborative offers these simple steps for cleaning boots and waders:
- Stomp and inspect as soon as you leave the water to remove attached debris.
- Brush waders, soles and laces to loosen remaining debris and mud.
- Spray boots and waders thoroughly with a disinfecting agent.
- Rinse after 20 minutes.
- Dry waders thoroughly before next use.