The Invasive New Zealand Mud Snail Spotted in the Delaware River Watershed

The Invasive New Zealand Mud Snail Spotted in the Delaware River Watershed

By Nancy Lawler, Water Quality Coordinator for the Musconetcong Watershed Association

 MWA intern Levi Morris reviewing a macroinvertebrate sample with a volunteer.

MWA intern Levi Morris reviewing a macroinvertebrate sample with a volunteer.

Call it “Snailzilla” or “the Snailpocalypse,” but the New Zealand mud snail is an invasive species that is no laughing matter. Just this month, the mud snail’s presence was recorded in the Musconetcong River in New Jersey and the Little Lehigh River in Pennsylvania - the first two sightings in the Delaware River Watershed. The mud snail has the potential to rapidly reproduce through cloning and displace native macroinvertebrates. Macroinvertebrates include insects, snails, worms, algae, bacteria, and fungi that play key roles in the ecosystems they inhabit. Displacing native macroinvertebrates can have upstream affects in the food chain, by pushing out native aquatic insect larva and snail populations that feed fish and insect-eating terrestrial species like bats, dragonflies, and birds. 

The Musconetcong Watershed Association (MWA) reached out to state and federal agencies to spread the word, and shared information with project partners on how the mud snail might be controlled. While there is no consensus on how to adequately clean gear without introducing chemicals harmful to the waterway, experts do agree that cleaning should occur before leaving the river bank. Fishermen, boaters, and scientists that work in the river should clean their clothing and gear of debris and mud to slow or prevent the mud snail moving between streams. MWA is already looking for funding to help the public learn how to identify this invasive critter, and perhaps keep it out of other local streams.

The snails cling to anything and are remarkably tough; they can survive out of water for as many as fifty days by closing their operculum, the tiny trap door that seals their shell. When eaten, the mud snail can apparently pass through the guts of predatory fish and birds whole and unharmed. But it is likely that the snail also spread from waterway to waterway by hitchhiking on the soles of waders and fishing gear.

As MWA’s Water Quality Coordinator, I send routine spring macroinvertebrate samples for taxonomic identification and analysis to Cole Ecological, Inc. Five sampling locations had the New Zealand mud snail. Because New Zealand mud snails were found at sites upstream and downstream of the 37.5-foot-high Warren Glen Dam, it’s not clear how it came into the Musconetcong River.

MWA has a strong educational mission, including running a citizen science program for more than ten years. Getting information out about a threatening invasive species like the New Zealand mud snail is part of that effort. The New Jersey Department of Environmental Protection recently issued guidance, as has the Pennsylvania Fish and Boat Commission. It’s early days still, and the research has yet to catch up on the best practices for containing this potentially harmful snail.

More About the New Zealand Mud Snail

The New Zealand mud snail is bad news for any stream. They originally came into the United States in contaminated trout stocking shipments in 1987. In North America, colonies of this tiny invasive species can carpet the bottom of waterways, though adults are less than ¼ inch long. In Yellowstone National Park’s Madison River watershed, snails were observed at densities of as much as 800,000 snails per square meter. Until recently, mud snails were unknown in the eastern part of the United States. Now the tiny invasive has been documented in Gunpowder Creek in Maryland, Spring Creek in Pennsylvania, the Musconetcong River, and the Little Lehigh River. 

 Nancy Lawler, Water Quality Coordinator for the Musconetcong Watershed Association, taking a benthic invertebrate sample in the Musconetcong River.

Nancy Lawler, Water Quality Coordinator for the Musconetcong Watershed Association, taking a benthic invertebrate sample in the Musconetcong River.

About the Musconetcong Watershed Association

The Musconetcong Watershed Association in Asbury, New Jersey, works with citizens, municipalities, as well as state and federal agencies to protect and improve water quality in the Musconetcong River. The Musconetcong River flows 42 miles from its headwaters in Lake Hopatcong, through small scenic historic towns, downstream to where it finally joins the Delaware River, in the town of Riegelsville. The river was designated as part of the federal Wild and Scenic River system in 2006, and is noted for its critically threatened Brook Floater mussel habitat.

Resources on the New Zealand Mud Snail: