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Invasive New Zealand Mud Snail Found in Lake Michigan

Published August 14, 2008
URBANA - Earlier this summer, researchers at the Lake Michigan Biological Station (LMBS), a field station of the Illinois Natural History Survey (INHS), discovered a population of New Zealand mud snails while processing a sample from Lake Michigan--one of the first reported sighting of this species in the lake.

Native to New Zealand, these mud snails are an invasive species in North America, Europe, and Australia. They were first spotted in the United States in 1987, and were found established in Lake Ontario in 1991--the first occurrence of the species in the Great Lakes.

Aquatic ecologists from LMBS identified the species while processing samples that had been taken from the waters one mile south of Waukegan Harbor in September of 2007. Another discovery of New Zealand mud snails in Lake Michigan was announced in June. The sample had been collected in deeper water--20 m in depth--off the coast of Waukegan in 2006.

According to Kevin Cummings, INHS malacologist, this discovery is significant because of the species ability to reproduce asexually, which allows them to spread at a rapid rate. "It's hard enough to contain a species once it makes its way into non-native waters," said Cummings. "When each mud snail has the ability to produce large quantities of embryos without a partner, you've really got a problem."

Due to previous stresses from other invasive species, the introduction of New Zealand mud snails into Lake Michigan could prove more damaging than it has in other waters.

"If the New Zealand mud snail becomes widely distributed at high densities, it could further disrupt the system by outcompeting native mollusks and other invertebrates for habitat and food," said Sara Creque, a LMBS aquatic ecologist. "Many of the native invertebrates are already declining throughout the lake. If the New Zealand mud snail out competes these species, it could have detrimental effects on upper levels of the food chain."

New Zealand mud snails have no natural predators in the United States. And, although trout have been readily eating them in Western rivers, the mud snails can be too numerous for predation alone to eliminate them. "There isn't really anything you can do to control them once they're here," said Cummings. "We just need to step up our efforts to make sure species like these don't get into our waters in the first place."

"The concern now is that these mud snails will spread to inland waters," said Kristin TePas, Illinois-Indiana Sea Grant aquatic invasive species outreach specialist. "Anglers and boaters play a crucial role in preventing this from happening."

Due to the mud snails' small size--up to 5 mm in length--anglers and boaters will not have much luck spotting them, she added. Instead, they need to be vigilant about performing important practices such as draining water from the boat, removing plants and mud from equipment, and rinsing gear.

"In fact these steps should be a part of their routine all the time to prevent not only the spread of New Zealand mudsnails but other invasive species as well," said TePas.


The Illinois-Indiana Sea Grant College Program is one of 30 National Sea Grant College Programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs. Funding is provided by the U.S. Department of Commerce, the National Oceanic Atmospheric Administration, the University of Illinois and Purdue University.