Researchers track invasive mudsnail in Michigan rivers

MICHIGAN — A tiny invader is threatening prized trout streams in Michigan’s northern Lower Peninsula.

At 1/8-inch long, the New Zealand mudsnail is barely distinguishable from a grain of sand, but over time its invasive habits can affect the quality and quantity of trout and other fish in the Au Sable, Pere Marquette and Boardman rivers where it has been found.

New Zealand mudsnails were first discovered in the United States in Idaho’s Snake River in 1987. Since then, infestations have spread throughout the western states and into areas of the Great Lakes. The discovery of New Zealand mudsnails in the Pere Marquette River in August 2015 signaled the first detection in a Michigan inland waterway. Within the next year, populations were confirmed in the Boardman and Au Sable rivers. The U.S. Geological Survey has developed an animated map illustrating the New Zealand mudsnail’s movement through the states.

What harm can a snail do?

This brown to black 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), just one snail can start a population.

One snail can produce over 200 young in a year. Since no natural predators or parasites exist in North America, exponential population growth occurs unchecked, year after 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.

What is Michigan doing to combat the problem?

Once New Zealand mudsnails were positively identified in the Pere Marquette River, the DNR and the Department of Environmental Quality began surveying heavily utilized rivers across the state. Since the discoveries in the Boardman and Au Sable rivers, no new mudsnail locations have been identified. Surveying efforts will continue through the 2017 field season.

Mudsnail distribution

In a project supported by the Great Lakes Restoration Initiative, the DNR and Michigan State University are working together to understand how widely distributed New Zealand mudsnails are in the Pere Marquette River and how these invaders may be affecting native invertebrates.

“We are also taking the opportunity to talk to anglers about their behaviors, whether they travel to multiple fishing spots in a single day, and whether they are washing their gear between visits,” said Dr. Dan Hayes, a professor and associate chair of MSU’s Department of Fisheries and Wildlife. “Their responses help us understand potential vectors for New Zealand mudsnail transportation.”

A chemical treatment targeting sea lamprey in the Pere Marquette River is scheduled for summer 2017. MSU researchers will use this opportunity to determine what, if any, effect the lampricide treatment has on mudsnails.

What can you do?

Invasive species management begins with prevention. Though the snails have been found in three river systems, it is not too late to prevent their spread to other rivers and lakes. Since it takes only one New Zealand mudsnail to start a population, prevention requires everyone’s involvement.

The most important means of prevention is practicing good recreational hygiene. After a visit to one of Michigan’s lakes, rivers or streams, be sure to clean, drain and dry your boat, trailer and gear before heading to a new destination.

The New Zealand mudsnail’s small size requires careful examination and cleaning of places where plants, sand 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.

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