- Author: Chris M. Webb
Dr. Sabrina Drill, of the University of California Cooperative Extension (UCCE), is a Natural Resources Advisor covering both Los Angeles and Ventura Counties. One of the issues she is currently studying is the New Zealand mudsnail (NZMS), Potamopyrgus antipodarum.
NZMS is an aquatic invasive species that was first found in the United States in Idaho in 1987. It has since spread to every Western state except New Mexico. They were found in California’s Owens River in the late 1990’s. In 2006 it was found in the Santa Clara Watershed, which straddles the two counties Dr. Drill covers in her UCCE work.
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. A single female and her offspring are capable of yielding 40 million individuals in a year! As is typical with invasive species, they compete with native invertebrates for food and habitat, and as they provide little in the way of food value, may have detrimental effects on fish and wildlife. They have a wide ranging temperature and salinity tolerance, 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.
The best way to manage New Zealand mudsnails and other invasive species is to try and prevent them from spreading.
Please help contain the spread of NZMS by doing the following:
- Stay out of infected streams and do NOT go from one stream to another in wet gear.
- If you need to go into an infected stream, consider having dedicated clothes and gear that you don’t wear anywhere else.
- Scrub all gear with a stiff brush before you leave an infected site; mudsnails are experts at hiding, so you can’t trust a visual inspection.
- Let all gear dry completely between visits, or freeze for a minimum of six hours between uses.
As Dr. Drill continues to monitor the distribution and impacts of NZMS in the Santa Clara River she will be adding her findings to the NZMS website. You can find the site at http://groups.ucanr.org/NZMS/. She will also be doing outreach for fisherfolk in the fall. Check back for dates and locations!