New Zealand mudsnail

Potamopyrgus antipodarum · Aquatic life

Whole animal · Photo: Alexander Mrkvicka / CC BY-SA

InvasiveMollusk (mussel, clam, snail)

Also called Potamopyrgus, Mudsnail, NZMS

State listing

Idaho: Prohibited invasive species
Wyoming: Game and Fish aquatic invasive species

How to identify New Zealand mudsnail

Tiny snail, usually 1/8 to 1/4 inch
Long, narrow, cone shaped shell with 5 to 6 whorls
Light to dark brown or black, sometimes with a keel
Right handed opening with a thin trapdoor (operculum)
Can carpet rocks and plants in huge numbers

Similar species

Native pebblesnails and other tiny snails are usually shorter and rounder; a hand lens and an expert check are often needed. Physid snails coil to the left and have no trapdoor.

Profile

Season	Present all year; reproduces year round when water is not too cold.
Starts	Reproduces in water above about 50 F
Depth	Bottom, rocks and plants from shallow edges to deep water
How it spreads or reproduces	Females clone themselves without males, so one snail can start a population; carried on waders, boots, boats, fish and gear and can survive passing through fish
Habitat	Rivers, streams, spring creeks, lakes, reservoirs and canals; tolerates a wide range of conditions including silt and mild salinity.

Why it matters in a lake

Invasive snails that crowd out native insects and snails that trout feed on. Cleaning, drying or freezing waders and gear between waters is the main defense; report new finds to the state.