New Zealand Mudsnails
The New Zealand mudsnail, Potamopyrgus antipodarum, is an aquatic invasive species that was first found in the United States in Idaho in the 1987, and has since spread to every Western state except New Mexico. They appeared in California in the late 1990’s in the Owens River, and were found in southern California in Malibu Creek in 2005 and in Piru Creek in the Santa Clara River watershed in 2006. Since their discovery in Malibu Creek, they have spread to several streams in the Santa Monica Mountains.
New Zealand mudsnails are tiny, with adults only reaching 3-5 mm and juveniles even smaller, about the size of a grain of sand. They are usually light to dark brown, and may appear black when wet. They have conical shells that have five, or sometimes six whorls.
New Zealand mudsnails reproduce clonally and bear live young. Broods of up to 120 can be produced three times per year in warm climates, and a single female and her offspring are capable of yielding 40 million individuals in a year.
We believe they compete with native invertebrates for food and habitat though research is currently underway. What is known is that they reach huge densities. Over 750,000 individuals per square meter have been recorded in the Yellowstone River. As they provide little in the way of food value, they may have detrimental effects on fish and wildlife. They have wide ranging temperature and salinity tolerances, and can survive for several days out of water under moist conditions.
Taken together, their small size, dark coloration, and ability to stick to things makes them excellent at invading new systems. They can hitch a ride on fishing gear, sampling equipment, shoes (hiding in the treads and under the laces), and clothes, as well as on the fur of dogs and horses. We know of no way to get rid of them once they invade a river system, other than drastic dewatering or poisoning. Researchers are investigating options for biological control.
Download our new New Zealand Mudsnail Fact Sheets!
UC Cooperative Extension and UC Santa Barbara are collaborating on research on the ecological impacts of New Zealand Mudsnails. For more information on this research and on UCSB research on control methods, visit UC Santa Barbara NZMS Research Projects
General overview of the biology of New Zealand Mudsnails, developed by Montana State University
Country-wide overview developed by the US Geological Survey
General overview by the 100th Meridian Project, a collaboration of several government agencies working on stopping the nationwide spread of invasive species
General information about New Zealand Mudsnails and other invasive species in California, including reporting information from the California Department of Fish and Game
Information about New Zealand Mudsnails in the Santa Monica Mountains: http://mudsnails.com/
Local information may also be available by contacting your local parks agency or water supplier.
Preventing the spread of New Zealand Mudsnails
Inspections and Decontamination
Information on how to inspect and decontaminate gear, clothing, and vessels to prevent spreading aquatic nuisance species available at: How to Prevent the Spread of New Zealand Mudsnails through Field Gear from Oregon Sea Grant
California Department of Fish and Game New Zealand Mudsnail poster and watchcard
o Scroll down for available public education materials
Protect Your Waters, Stop Aquatic Hitchhikers Campaign
Education about the problems caused by releasing unwanted pets and plants. Developed by Habitattitude: http://www.habitattitude.net/
Exotic Aquatics on the Move – Resource for K-12 education about aquatic invasive species. Developed by the National Sea Grant Network and Geographic Education Alliance