Original release Tuesday, August 13, 2002 11:00 AM

Contact: Kiza Gates, Conservation Coordinator or Bob Wiltshire
FFF-Fly Fishing Discovery Center
Livingston, Montana
406-222-9369

The Federation of Fly Fishers (FFF) is warning all anglers and water users about the risks of transporting New Zealand Mud Snails "We are calling on all anglers to immediately take action to insure that they do not spread New Zealand Mud Snails" says Verne Lehmberg, FFF Conservation Vice President. "New Zealand Mud Snails are rapidly being spread to waters across the west and each of us must insure that we are not part of the problem."

Since their discovery in Idaho's Snake River New Zealand Mud Snails have spread to surrounding areas where they have flourished. These small brown snails measure no more than 1/8 inch. An individual snail is no problem but New Zealand Mud Snails easily reach densities that cause significant problems. Snail numbers as high as 750,000 per square yard have been recorded in some areas. At these levels the snails consume most available food leaving little for native snails and aquatic insects to feed on. This leads to a reduction or elimination of these creatures, which can result in a significant impact on fish populations.

Anglers easily overlook the small snails which can be found clinging to waders, boats, tackle and other fishing accessories. The snails have the ability to close off their shell opening allowing them to live for significant lengths of time without being in water. Anglers unknowingly transfer the snails to new waters when they are lodged in their equipment. It is likely that transport by anglers is the most significant cause of mud snail spread.

"In recent weeks the snails have been discovered in the Colorado River at Lee's Ferry, and in Montana's Beaverhead and Upper Missouri Rivers" reports Lehmberg. "All of these are popular angling destinations and there is compelling evidence that these introductions are angler caused. The FFF knows that anglers are interested in protecting our waters, not hurting them, and the only reason snails are spread is because people don't know about them."

The FFF is asking every angler and water user to take a few simple precautions to help control the spread of NZMS.

1. Thoroughly clean and rinse your equipment before you leave a fishing site.

2. Completely dry all equipment before using again.

3. Hot temperatures kill NZMS - 113 degrees for 60 seconds will kill 100%.

4. Never release fish or any other living creature into any water it did not originate in.

The Federation of Fly Fishers, a non-profit membership organization, conducts a variety of programs designed to help counter the threat of invasive species. For more information contact the FFF at 406-585-7592 or www.fedflyfishers.org.

New Zealand Mud Snail - Fact Sheet

Scientific Name: Potamopyrgus antipodarum

Originally found only in New Zealand the New Zealand Mud Snail (NZMS) was first transported to England in 1859. By 1899 it had reached mainland Europe and the 1920's found it throughout all of England. In 1987 NZMS were discovered in Idaho's Snake River. In 1997 surveys showed the snail had spread to all of the major waters in Yellowstone National Park. In recent years it has been found throughout the Columbia River drainage, in many Montana waters and in several California streams.

NZMS have the capability for clonal asexual reproduction. In this type of reproduction a single snail can reproduce with no mate. Thus, a single snail is all that is required to establish a new population.

NZMS reproduce very rapidly. A single snail produces up to 38 live snails twice a year. Each of these reaches reproductive age very quickly and it is possible that a single individual could be responsible for a population of 3,700,000 in two years.

NZMS impact the environment through sheer numbers. Densities of more than 800,000 per square meter have been recorded in several areas. These huge numbers of snail eat much of the available food in the stream. A recent study from Montana State University showed that NZMS can consume up to 50% of the production in a stream.

The impact of NZMS feeding on available food is seen in several ways. The most immediate impact is on populations of native snails that can quickly be pushed out. In fact, in Pole Cat Creek in Grand Teton National Park a unique native snail found only in the creek is facing extinction because of competition from NZMS.

Many organisms besides snails are impacted by NZMS. Many aquatic insects can be impacted as well. Invertebrate studies show marked declines in midge and mayfly populations.

Loss of native snails and other aquatic invertebrates becomes a loss of food to various fish. NZMS provide little if any nutrition to fish that eats them. In fact, a significant percentage of the snails that are eaten pass through the fish alive.

NZMS have no natural enemies in North America. In New Zealand a tiny parasite controls snail numbers, giving hope that future biological control might be possible.

NZMS invasions can only be controlled by preventing the spread of the snail. Once they are established there is no known way to eradicate them. All of the methods of transport have not been identified but it is almost certain that water recreationists are the primary vectors of spread.

New discoveries of NZMS are occurring rapidly as biologists and others become trained in looking for them. They are probably found in far more waters than currently identified.

More information on NZMS can be obtained from the Federation of Fly Fishers at 406-222-9369.

These Photographs were taken by Vern Lehmberg, Conservation Chairman

They show the size of these snails.

All pictures Copyright: Federation of Fly Fishers