The New Zealand mudsnail, Potamopyrgus antipodarum was first discovered in the mid-Snake River, Idaho in the 1980's. It is now rapidly spreading throughout the western USA and has become established in rivers in 10 western states and three national parks. It is a parthenogenic livebearer with high reproductive potential.
The New Zealand mudsnail often reaches densities greater than 100,000/m² in suitable habitat and has been reported to approach densities as high as 750,000/m² in sections of rivers in Yellowstone National Park. Frequently, these mudsnails will comprise over 95% of the invertebrate biomass in a river. To date, limited research has documented decreases in native macroinvertebrate populations in several rivers where the mudsnail has invaded. Potamopyrgus antipodarum has also been shown to drastically alter primary production in some streams. Its invasion has generated much concern about the potential effects it may have on native species, fisheries, and aquatic ecosystems in the western USA. Its spread into new systems is considered to be primarily human caused.
