Due to its small size (several can fit on a dime), the New Zealand mudsnail can easily hitchhike on a variety of recreational and commercial
equipment that comes in contact with the water and riparian zone.
Invasive snails find Wisconsin ready to defend
Timely lessons as June is Invasive Species Awareness Month.
Sampling the bottom of a cold water stream is a lot like upending a Lilliputian city into your net. There are caddisflies in their rocky armor, split–tailed stoneflies and worm–like midge larvae — all tumbling downstream into a waiting net along with algae, vegetation and gravel. Thatís why it was so easy for hundreds of tiny, dark snails to hide in the net of Water Quality Biologist Mike Sorge, kicked up like so many pieces of sand from the bottom of Black Earth Creek in Dane County, a renowned trout–fishing stream.
Without any fanfare, they made their way to a lab at UW–Stevens Point, just one of more than 400 samples from around the state that the Department of Natural Resources takes every year to keep track of stream health and catch problems early. Except when researchers began to pull apart Sorgeís sample under the microscope last October, they noticed the pieces of "sand" were actually New Zealand mudsnails, one of the most troublesome invasive species for trout streams.
When Sorge heard the news, he knew Wisconsin was in for a tough challenge. The snails can travel unnoticed on wading boots, gear or construction equipment and people leaving waterways donít think to look for them. They graze on algae and zooplankton, compete with native grazers and could negatively impact the stream.
Sorge says, "Theyíre hard to see, they like to cling and they can be mistaken for coarse grains of sand or tiny rocks."
Sticking to boots may be how the snails reached Black Earth Creek in the first place. Since mudsnails only reproduce asexually outside of their native range — cloning themselves — geneticists can track where they came from. "Clone 2" snails live in the waters of Lakes Michigan and Superior and probably arrived through ballast water, but have not been expanding their range. "Clone 1" snails may have arrived with stocked game fish in Idaho and then spread on recreation equipment. Clone 1 populations only lived west of ColoradoÖ until now.
Call to action
With such an adept hitchhiker in Black Earth Creek, the first step was to get the word out as fast as possible. Two aquatic invasive species (AIS) experts — DNRís Statewide AIS Monitoring Coordinator Maureen Ferry and Regional Watershed Coordinator Susan Graham — reached out to Wisconsinís existing AIS partnership to quickly pull together a rapid response team with experts from UW–Extension, the River Alliance of Wisconsin and the department. Within days of confirming the find, the team was spreading the word with the news media and stakeholder groups across the Midwest.
Any time a species arrives to a new habitat, itís hard to predict how it will fare. In the worst case scenarios, mudsnails in some western U.S. waterbodies have been found growing at densities of up to 500,000 per square meter, changing native food webs and impacting trout health. However, in other locations they have had minimal impact, or the snail populations have crashed after an initial boom. Itís too early to know which route the mudsnails will take in Wisconsin or if they will spread to other habitats in the Mississippi River watershed.
As ground zero for the snailís arrival in the inland Midwest, Graham says, "We had a lot of questions, but also guidance from our rapid response plan that helped lead us to the right people to answer them."
One of the first questions was whether the snail might already be at other locations.
"We think theyíve been in Black Earth Creek maybe two years," says Graham, "So thereís a chance theyíve already spread around."
Before the team could head out to investigate, though, they had to develop a protocol to clean gear so that researchers wouldnít spread mudsnails by accident. Graham says this step was challenging because New Zealand mudsnails have another trick up their shells that helps them get around. A structure called an operculum functions like a trap door to lock them in their shells at signs of trouble, making them resistant to common chemicals like bleach. They can also resist drying, staying alive for up to 26 days in a damp, cool environment, or even survive passage through a fish gut — making fish a potential source of spread.
The result, says Ferry, is that, "We have some new prevention steps that work for these snails that we havenít needed in the past." The team will work on sharing these new methods with groups at risk of spreading the snails such as researchers, anglers and stream restoration crews.
Graham and Ferry say the response from these stakeholders, especially groups like the River Alliance of Wisconsin and Trout Unlimited, has been phenomenal. Members of Trout Unlimited have volunteered for monitoring and outreach work, which Steve Wald, the president of the Southern Wisconsin chapter, says is just the right thing to do.
"We believe in a strong connection between enjoying and protecting the resource," says Wald. "We recognize that anglers can be a major vector for invasive species, so weíre tuned in and ready to participate in any way we can."
The support was evident at a public meeting held in Cross Plains last December, near the source of the discovery. Local sportsmen and women, business owners and concerned citizens packed in to learn more about the snails on their doorstep and share their ideas with the response team.
With help from meeting attendees on locating heavily–trafficked water access points, the response team completed a plan to survey more than 100 sites statewide to learn if New Zealand mudsnails are anywhere else in Wisconsin.
With crucial help from volunteers, the team has been screening kick–net samples taken in the middle of winter.
Ferry said, "We had biologists going out in freezing temperatures to get stream samples, but they were happy to be there. Thatís remarkable."
With voluntary support from labs at UW–Madison, UW–Stevens Point, the U.S. Geological Survey in La Crosse and the U.S. Fish and Wildlife Service, the rapid response team is also experimenting with a new method that Wisconsin has used before to search for Asian carp — environmental DNA.
DNR Fisheries Biologist David Rowe explains how the process will work for mudsnails.
"Using Black Earth Creek as a test site, weíre going to analyze the water samples for [mudsnail] DNA," says Rowe. "The neat part about eDNA is that water makes it go everywhere, so even at very low density it gives us an idea if mudsnails are there before we ever look with a kick–net. If it works well at Black Earth Creek, it will help us with early detection around the state."
The results could provide key clues for managing mudsnails in the future. "Oftentimes an invasive species will be present but stays in the background," says Rowe. "If we can detect populations with low densities, we can test the systems where they donít take off."
A future with invasives
Any time a new invasive species makes the jump across state borders, itís easy to be discouraged. Whatís remarkable about the New Zealand mudsnail discovery, though, is how quickly Wisconsin has been able to respond thanks to existing partnerships.
Historically, ballast water in the Great Lakes has been the main source of Wisconsinís inland invasive species and the associated costs they bring to water quality, recreation, tourism and industry. However, regulations since 2006 for oceangoing ships have effectively halted new introductions to the Great Lakes. Out of 184 species introduced to Lake Michigan in the past century, only 30 have made it to inland Wisconsin waters. The large majority of Wisconsinís inland waterways remain free of harmful species like Eurasian watermilfoil and zebra mussels even decades after these species were introduced to the state.
This is a testament to the success of prevention programs like Clean Boats, Clean Waters, which today reaches more than 200,000 boaters each year. In 2013, 96 percent of these boaters said they were aware of state AIS laws. Department staff works with a vast partnership that includes scores of lake and watershed associations, nonprofit partners, university specialists, federal and state agencies and nearly 50 county AIS coordinators.
To Ferry, this says that the fight against invasive species is a stand worth taking. "What boaters are doing every day to clean their gear is working well for our lakes and rivers, protecting our natural heritage, as well as saving communities time and money down the line. When an invasive species does occasionally slip through the cracks, like now, weíre able to respond."
Wisconsinís latest invader is certainly concerning, but Laura MacFarland of the River Alliance, who has been working with Wisconsin anglers since 2007 and is playing a leading role in the mudsnail response, has suggestions on how to make sure mudsnails donít spread any faster than a one–eighth–inch snail can crawl.
"You can learn to identify them, learn the prevention steps and help educate others about the threat and prevention steps," says MacFarland. "Everyone who uses the water can make a difference."
Deborah Seiler is an aquatic invasive species communications specialist for UW–Extension and the Department of Natural Resources.