Representing the second detection of the invasive snail in a major northern Michigan river system within the past year, New Zealand mudsnail (scientific name: Potamopyrgus antipodarum), a rapidly reproducing aquatic invasive species first discovered in the waters of the Pere Marquette River near Lake Michigan last summer, has now been found in the east branch of the Au Sable River near Grayling. Achieving extraordinary rates of reproduction and populations densities of up to 500,000 per square yard, invasive New Zealand mudsnails pose a serious threat to the viability and sustainability of native macroinvertebrate communities that provide the ecological foundation of Michigan’s $2 billion sport fishing industry.
New Zealand mudsnails were most likely initially introduced to the Great Lakes via ocean going freighters that entered the region through the St. Lawrence Seaway from Europe, where large populations of the highly invasive snail have existed for decades. Discovered in Lake Ontario in 1991, the waters of Lake Erie in 2005 as well as within Lake Michigan, near Waukegan, Illinois in 2006, New Zealand mudsnails were first discovered in North America in 1987, as populations of the invasive snail were detected in the Snake River of Idaho, and have subsequently spread to many rivers, streams, and inland lakes throughout western regions of the United States during the past thirty years.
The tiny shells of New Zealand mudsnails are usually gray or light to dark brown in color, and exhibit a distinctive right-handed coiling pattern comprised of 5-6 whorls. Capable of growing to nearly one half inch in diameter within the freshwater streams and inland lakes of New Zealand, the invasive snails found in Michigan’s waters usually grow to no more than one eighth of an inch in diameter. The species’ tiny size makes it relatively easy for anglers and boaters to unknowingly transport the invasive snail from one waterbody to another. Capable of tolerating northern temperate water temperatures ranging from just above freezing to 83° F, relatively high levels of salinity, and light depriving turbid conditions, the tiny snails are found in a diverse array of water bodies. Possessing a significant competitive advantage over native macroinvertebrate species due primarily to their ability to rapidly achieve large numbers, New Zealand mudsnails represent a significant threat to the native fauna communities that are an important component of healthy, productive aquatic ecosystems.
Easily transported from one stream or lake to another via the waders or boats and trailers of fisherman or recreation boaters, the accidental introduction of a single invasive mudsnail carries the potential to begin a new infestation within a river, stream or inland lake. Once New Zealand mudsnails have been successfully introduced and have established sustainable populations within a particular waterbody, there is no viable way of effectively eradicating the species without inflicting co-lateral damage to host aquatic ecosystems. Folks engaged in fishing, canoeing, or kayaking should always strictly adhere to the Clean Boats, Clean Waters mantra of “Clean – Drain – Dry – Dispose”. For more information about how you can help prevent further introductions of aquatic invasive species, please visit the Michigan Clean Boats, Clean Waters program website viewable at www.micbcw.org .