A New Invader, New Zealand Mudsnails, Found in Black Earth

A New Invader, New Zealand Mudsnails, Found in Black Earth Creek

Black Earth, WI:   New Zealand mudsnails, tiny invasive snails measuring a mere four to six millimeters, have been found in Black Earth Creek in western Dane County this week by the Wisconsin Department of Natural Resources.  

This snail has the potential to harm the celebrated trout fishery of Black Earth Creek and other streams in southwestern Wisconsin.  Wading anglers and other river users are being asked to help curb its spread by cleaning their gear before moving between streams.

New Zealand mudsnails are notorious for hitching a ride on the waders and boots of anglers throughout the western U.S. from one popular trout stream to another.  Given the rising popularity of the southwestern Wisconsin as a destination trout fishery, the discovery, while devastating, isn’t entirely unexpected.

 “Due to the national renown of the Driftless Area, we have anticipated the arrival of New Zealand mudsnails for several years,” said Laura MacFarland, River Alliance of Wisconsin’s Invasive Species Director.  “In preparation, we have been working hard to raise awareness about this species and the role of river users, including wading anglers in the prevention of their spread.  This discussion just became a whole lot more real.” 

Are our trout in jeopardy?

New Zealand mudsnails could have a negative impact on our valued trout fisheries throughout the Driftless Area, but ultimately, no one is sure what to expect.  There are plenty of incidences where invasive species, including New Zealand mudsnails, have been found but never cause wide spread havoc. 

However, based upon what we have seen out west, it is anticipated that this new invasion may likely result in a decrease in the number and size of trout in invaded streams.  This is the first known occurrence of New Zealand mudsnails in the Midwest where our streams differ significantly.  Here in agricultural dominated watersheds of southern Wisconsin where the food web is based on algae, our fish’s diets depend highly on the very bugs that these mudsnails are going to replace.  Mudsnails, themselves, provide very little to no nutrition for fish.  

“Our trout already face a number of challenges from agricultural runoff to climate change to gill lice.   Sometimes a new threat, like an invader that disrupts a food supply, can interact with these existing threats compounding their impacts.  Therefore, it is important that we do what we can to minimize the spread of the New Zealand mudsnail within the Driftless Area to protect our native fish and widlife,” says MacFarland. 

Anglers, duck hunters, contractors, and farmers can help prevent the spread of New Zealand Mudsnails and Other Invasives

While it’s not known exactly how these invasive snails found their way from the western United States to Wisconsin, it is certain that anglers, duck hunters, utility and stream restoration contractors, and farmers all may inadvertently spread them to nearby waters. 

The River Alliance has been working for years in close partnership with Trout Unlimited and other local river groups to promote measures to curb the spread of invaders, such as wild parsnip, Japanese hops and zebra mussels. 

According to Henry Koltz, chariman of Wisconsin Trout Unlimited Council, “Wisconsin TU is disturbed by the arrival of New Zealand mudsnails here in our state.  Preventing the introduction and spread of invasive aquatic species is incredibly important to Wisconsin Trout Unlimited’s mission.  To that end, and despite this clear setback, we will continue to partner with the River Alliance and other groups to educate the public about invasive species, and to provide clear instructions how to clean equipment in order to reduce or eliminate the spread of invasives.”  

All of the steps below will minimize the risk that you are moving live snail.  Freezing or completely drying your equipment is most effective.  Notice bleach is NOT recommended.  

  • Inspect your gear, clean off mud and plant material and drain all water. 
  • Scrub your equipment with a stiff, synthetic  bristled brush
  • Rinse equipment with tap water  after scrubbing clean
  • Freeze clean, dry equipment for 6 to 8 hours.  Really wet equipment will require longer. 
  • Completely dry equipment.  Scrub all debris and mud off gear before drying for a minimum of five days.   This will not be effective for felt soled boots or other porous materials that remain damp.  New Zealand mudsnails can survive in slightly moist environments for weeks.

The River Alliance has created a short, four minute video demonstrating how to clean your waders before you leave a stream:  http://youtu.be/LPlRYsqNxJo

For more information contact the River Alliance of Wisconsin at lmacrfarland@wisconsinrivers.org.

Photo Credit: USGS


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