Human activities can introduce plants, animals and diseases into places where they outcompete native species and disrupt ecosystems.
The Arizona Game and Fish Department says one such invasive species has now reached Tonto Creek: the New Zealand mudsnail.
Since their detection two decades ago near Lees Ferry, the snails have moved down the Colorado River and into the lower Verde and Salt Rivers.
The new sighting lies two-and-a-half miles downstream of Tonto Creek Hatchery, which remains closed to the public while the department evaluates and tightens biosecurity there. The hatchery raises six varieties of trout and provides habitat to an array of wildlife.
The department says the tiny snails, which reach about one-eighth to one-quarter inch in the Southwest, pose a threat because they compete with native invertebrates for food, posing potential harm to Arizona’s native and sportfish populations, as well as native mollusks.
Moreover, because the mudsnails reproduce asexually and give birth to live young, only one is needed to start a new population.
Other confirmed New Zealand mudsnail populations in the state include Canyon Creek, Oak Creek, Verde River below Bartlett Dam, lower Salt River, Lake Mead, Lake Mohave and the Colorado River from Davis Dam to Interstate 40.
As with any water body listed as containing invasive species under Director’s Orders, the law requires visitors to these waters or Tonto Creek clean, drain, dry and decontaminate equipment before using another Arizona water.
The department lists effective methods on its website azgfd.com/fishing-2/aquatic-invasive-species/.
