Tiny Intruder Alert: Maryland Confirms First Invasive Mollusk

U.S. Geological Survey

For the first time, the Maryland Department of Natural Resources has confirmed that there is a non-native, freshwater mollusk living in state waters.

The New Zealand mudsnail has taken up residence in the Gunpowder River. The Gunpowder Riverkeeper, Theaux Le Gardeur, reported finding small snails in the river in Northern Baltimore County, south of the Prettyboy Reservoir near Bush Cabin Run. Biologists went to the site to investigate, and were able to collect hundreds of snails in a matter of minutes.

Species expert Edward Levri confirmed they were Potamopyrgus antipodarum, or New Zealand mudsnails. The mudsnail is tiny, 4 to 6 millimeters long, and can be gray, dark brown or light brown. It feeds on algae, bark and leaves. It was first discovered in North America in 1987, when it was found in Idaho. Since then, it’s been spreading to several states. Because mollusks are asexual, the mudsnail can literally clone itself more than 100 times a year.

It’s not yet clear what the potential ecological impact is here, but state biologists worry that the invasive snail could crowd out native snails and insects that other native species, like fish, depend upon.

 A sample of mudsnails taken by Maryland DNR: tiny compared to a leaf
A sample of mudsnails taken by Maryland DNR: tiny compared to a leaf

DNR says the snail can easily be spread to other Maryland waters on anglers’ wading boots, fishing gear, or other equipment. The department is asking all boaters and fishermen to check their equipment and clean their boats, motors and trailers to prevent the mudsnail from spreading into other bodies of water.

Here are the precautions DNR recommends:

“Remove all dirt, mud and sand, and all visible animals, fish and plants from any equipment and gear before traveling and/or using them in another body of water. Eliminate water from all equipment and gear at the site before transport. Draining water at home could introduce an invasive hitchhiker to a local stream through the storm drain.”

-Meg Walburn Viviano