|
Arizona Game and Fish
Dept.
2221 W. Greenway Road
Phoenix, AZ 85023
(602)
942-3000
PRESS RELEASE
Media Contacts: April 9,
2002
AZ Game and Fish, Larry Riley, (602) 789-3258
National Park
Service, Mark Andersen (928) 608-6208
New Zealand Mudsnail, an
Invasive Species, Detected at Lees Ferry
New Zealand Mudsnails, an
aquatic nuisance and invasive species, have been detected at Lee's Ferry
in Glen Canyon National Recreation Area. These snails are not native to
North America and may have harmful effects on the river ecosystem. They
are not welcome visitors!
Mudsnails were unintentionally introduced
into North America and over the past two years have emerged as a serious
concern in the Western United States. New Zealand Mudsnails are very
small, about one-eighth of an inch in diameter and can be very hard to
detect when they first arrive. They can reach very high densities, as many
as a half a million per square meter. They provide very little or no food
value to fishes and other aquatic life and can compete with other animals
for nutrients, food, and space.
Lees Ferry is a very popular trout
fishery located on the Colorado River in the Glen Canyon National
Recreation Area in Northern Arizona. Lees Ferry is located just below the
Glen Canyon Dam that forms Lake Powell, and above Grand Canyon National
Park.
Snail populations have been
on the rise over the past several years. Observations of scientists,
anglers, and fishing guides have suggested that the snail populations have
been increasing. Concern has been expressed that snail community at Lees
Ferry might include New Zealand Mudsnails. Samples colleted earlier this
year were submitted to experts in Montana for identification. This
evaluation confirmed that Mudsnails are present.
New Zealand Mudsnails
arrived in the Western United States during the 1980s, where they were
detected in the Snake River in Idaho and the Madison River in Montana.
They have subsequently spread to Yellowstone National Park and in 2001
were detected in the Owens River in California. There are potentially
other infested sites that have not yet been identified.
Mudsnails are very small but
are also very tough. They tolerate temperatures ranging from near freezing
to about 78 degrees Fahrenheit. While they are aquatic, they are well
adapted to surviving some period out of water. The shell comes equipped
with an operculum or "hatch" that can seal the snail inside and protect it
from drying and from predators. In a moist environment, the Mudsnail can
survive out of water for at least several days. There is evidence that
they can pass through the digestive tracts of fish and potentially other
possible predators. This makes them very effective "hitch-hikers".
It
is not known exactly how or exactly when Mudsnails first arrived at Lees
Ferry. Work with scientists with the Grand Canyon Monitoring and Research
Center (Biological Research Division - US Geological Survey) is underway
to see if it is possible to identify about when they first arrived. They
likely arrived as a hitch-hiker. The most likely pathways for travel to
Lee's Ferry were on boats or gear used by anglers that had visited
infested sites, on equipment used by scientists at infested sites, or
potentially even with migratory birds that had visited infested sites.
Because the snails are so small, they can hitch-hike along the seams of
waders or in the soles of wading boots.
The New Zealand Mudsnail
doesn't require a partner to reproduce. The snails can reproduce
asexually, through a process referred to as parthenogenesis. A single
living snail can apparently start a new population.
There is no method
for removing these snails from the Colorado River at this point. The best
approach is to do all we can to minimize the possibility that they are
transported to other locations. Signs and information are being placed at
the Lees Ferry Boat Ramp to inform the angling and boating public, and
asking them to make sure they don't unwittingly transport mudsnails to
other locations. Anglers and boaters can accomplish this by doing the
following.
1) Inspect and clean fishing gear (waders, boots, nets,
etc.) and boats and trailers before leaving a fishing or boating site.
Remove any vegetation, mud, or foreign material that may be attached.
Drain water from your boat's bilge before you pull away from the
site.
2) Remove the stomach and digestive tract from any harvested fish
at the site you catch them, mudsnails can be transported in the guts of
fish. Dispose of that material in receptacles on site if at all possible.
Dispose of any fish remains at a sanitary landfill - don't flush them down
your drains at home.
3) Dry your gear thoroughly between uses at
different sites. Our hot Arizona sunshine is an asset. Cleaning and
thoroughly drying equipment in the hot sun for several hours can kill
mudsnails. Washing down equipment with a strong soap solution, rinsing
with tap water that drains onto the ground, and drying in the sun should
do the trick.
This is a serious threat to Arizona's wildlife resources,
and it will take the combined efforts of all of Arizona's citizens to keep
it from spreading.
-30-
Media Note: Additional information on
New Zealand Mudsnails can be obtained from the USGS at: http://www.fcsc.usgs.gov/ and at http://www.anstaskforce.gov/ . A
printable fact sheet can be downloaded from the Web at: http://www.fcsc.usgs.gov/Nonindigenous_Species/New_Zealand_Mudsnail/mudsnail2.pdf
back to the
News
|