Tiny snail spreads to southern Michigan, threatening local food webs

The New Zealand mudsnail has reached a new part of the state.

Volunteers from the Coldwater River Watershed Council found the small creatures in Bear Creek during a recent monitoring event. This stream is a tributary of the Thornapple River in Kent County. The discovery marks the first time the invasive species has been confirmed in the southern Lower Peninsula.

Officials are now conducting population genetics tests to determine how the snails arrived at this specific location. The species first appeared in the Great Lakes in 1991, likely via ballast water. It has since spread through various rivers and the Great Lakes themselves.

The snails pose a severe threat to local ecosystems. They reproduce asexually, meaning a single female can establish a new population without a mate. In Michigan, all recorded individuals are female. According to the Michigan Invasive Species Program, one snail can produce 200 clones per year. In some western states, densities have reached 300,000 snails per square meter.

Jen Koop, an invasive species biologist at Northern Illinois University, noted that the snails are difficult to detect until they are established. She stated that there is currently no way to eradicate them once they enter an aquatic system. The snails compete with native species for food and can clog pipes and drainage systems due to their high densities.

Donna Kashian, Director of Environmental Science at Wayne State University, explained that the snails may benefit from other invasive species. Zebra and quagga mussels filter nutrients from the water column and deposit nutrient-rich waste on the bottom. This creates ideal habitat for the mudsnails. Kashian said this adds another stressor to Great Lakes fisheries, which already face reduced nutrients and zooplank levels.

The Michigan Invasive Species Program advises people to clean, drain, and dry all equipment between water bodies. This includes waders, boots, and any gear that touches water or mud. The New Zealand Mud Snail Collaborative suggests using separate gear for known infested areas. Freezing, hot water, or long air exposure can kill the snails and prevent them from hitching a ride to new locations.