DOW INVESTIGATING THE PRESENCE OF NEW ZEALAND
MUD SNAILS IN SOUTH PLATTE RIVER
April 28, 2005
The Colorado Division of Wildlife (DOW) is working to
confirm if snails found in the South Platte River are the invasive
species from New Zealand.
Earlier this week, two anglers brought samples of what they believed
to be New Zealand mud snails to the DOW.
The samples were collected from the section of river below Elevenmile
Reservoir Dam and in Elevenmile Canyon. DOW fish pathologist Pete
Walker identified them as New Zealand mud snails. The DOW is working
to collect more samples from the river to confirm their presence and
measure how far downstream they are established.
The DOW has already implemented a public education program for anglers
and other people who use Colorados rivers in an effort to slow
the spread of this invasive species. New Zealand mud snails were found
in a section of Boulder Creek in late 2004, the first known discovery
Colorado. Efforts are underway to finalize a statewide management
plan for New Zealand mud snails. DOW biologists will also be working
to sample other popular fishing rivers throughout the state to determine
where else the snails may be. The DOW is sampling as many streams
possible before the spring run off begins and will continue sampling
throughout the summer and fall.
During a recent New Zealand mud snail workshop held by the DOW
on April 20 in Denver, top researchers noted that no significant impacts
to fisheries have been documented in any North American river system,
even those where the snail has been established for more than a decade,
said Robin Knox, aquatic invasive species coordinator for the DOW.
The mud snail is native to New Zealand and first spread to Europe
in the late 1880s and then to the United States in 1987 where it was
first discovered in the Snake River in Idaho. The snail, prior to
being found in Colorado, had spread to California, Oregon, Washington,
Idaho, Montana, Wyoming, Nevada, Utah and Arizona. The snails have
been shown to take advantage of new habitats colonizing rapidly. As
with most invasive species their numbers tend to peak quickly, but
then they drop back and stabilize once they reach equilibrium and
find a natural balance.
I am not surprised that these very hardy snails have been found
in another river in Colorado, said state aquatics manager Eric
Hughes. I suspect we will make more discoveries of New Zealand
mud snails, especially in popular fly fishing sections of rivers throughout
Mud snails can survive for as much as eight days in dried mud and
can be inadvertently moved from place to place on fishing waders,
boats, heavy equipment, etc., and it is speculated they may be transferred
The DOW will continue to take reasonable steps to slow the spread
of this small snail primarily by educating people who might otherwise
transport it to new waters, Hughes said. In fact, earlier
this year the DOW distributed alert posters to sporting goods stores
and license vendors around the state, put up displays at fly fishing
and outdoor sports shows, and are working closely with the US Fish
and Wildlife Service and organizations like Trout Unlimited to get
the word out to all people who use the rivers of the state.
Many discoveries of snails in North America have been associated
with popular fly fishing streams so all anglers are being encouraged
to take strong measures to clean their equipment, especially boots
and waders. Submerging in a 50-50 solution of FORMULA 409® cleaner
minutes will help prevent further spread of this pest, said
Knox. The DOW will be evaluating its public education program,
and will try to boost public awareness not only for New Zealand mud
snails, but also for other invasive species.
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