New Zealand mud snail
Potamopyrgus antipodarum (J.E. Gray, 1853)

New Zealand mud snail has a light tan to brownish, tiny, elongate, right-coiling shell of less than 0.25 in. (0.64 cm) length in Great Lakes populations (although it has been observed to nearly 0.5 in. [1.3 cm] in its home range).
Habitat and Habits
New Zealand mud snail is native to the fresh waters of New Zealand and nearby small islands. It occupies any shallow water (estimated less than 150 ft. [45.7 m]).
Ecological Threat
New Zealand mud snail can form dense populations and may crowd out native grazers and snails and prevent colonization by other macroinvertebrates, like native insects, including sensitive species that are indicators of ecosystem health. It is very tolerant of poor water quality, a wide range of temperatures, transport on mats of algae, and can even pass through the guts of fish alive. Densities greater than 300,000 individuals per square meter have been observed in Montana, making New Zealand mud snail a likely candidate as a biofouling nuisance at water intakes. It can also carry parasites that infect native snails and fish. Be careful to decontaminate fishing and sporting equipment so as not to spread existing populations or start new ones.

Identification, Biology, Control and Management Resources