Editorial: Mudsnail scourge major concern
By Ed Engle
The Daily Camera (CO)
Published February 24th, 2005
By now, most Boulder County fishermen know that late
last year, Bruce Norikane, a local resident and fly fisher,
discovered New Zealand mudsnails in Boulder Creek near
Pete Walker, a senior fish pathologist with the Colorado
Division of Wildlife, said that at the time Norikane didn't
know exactly what he'd found, but he knew it was something
There are a lot of biologists around the state who are
in awe of what Norikane did and how he pursued an answer
to the mudsnails' identity, Walker said.
The discovery of the mudsnail was not good news. The
short course on the New Zealand mudsnail goes something
They are anywhere from about the size of a grain of sand
to one-eighth inch long. A mudsnail is an especially resilient
critter that can survive in water temperatures from 32
to 77 degrees.
Even more important is the fact that they can live out
of the water for many days, and they are especially hard
to get rid of because they can close their little shells
up tight to prevent poisons from entering.
The reason fishery biologists and fishermen fear the
mudsnail in the Rockies is that it has no natural enemies
in North America. That means it can multiple at an obscene
rate. The mudsnails can virtually take over an aquatic
ecosystem from the bottom up, which doesn't leave much
room for things like the invertebrates that trout eat.
It's true that trout can indeed eat the mudsnail, but
it passes through their system unharmed, offering no nutritive
value. Oh, and by the way, the mudsnails reproduce asexually,
which theoretically means an entire population could be
created from a single snail.
The possible end result of all of these nasty facts is
that the mudsnail could deplete your favorite trout stream
Norikane's discovery is the first evidence of the mudsnail
in Colorado. In other western waters where the snail has
established itself the population densities can be astounding.
There are places in Yellowstone National Park with more
than 500,000 mudsnails per square yard. That can't be
With all of this in mind, the Colorado Wildlife Commission
closed a 21/2-mile stretch of Boulder Creek to fishing,
dogs, hunting — or anything that might allow the mudsnails
to be carried to another stream.
The first thing that comes to mind, of course, is how
could all of this be happening again? Wasn't whirling
disease enough? Isn't the spread of chronic wasting disease
in Colorado's deer and elk herds enough?
It's even more painful when you examine how this has
happened. The first record of New Zealand mudsnails being
found in the United States was near Mount Shasta in California.
No one knows for sure how they got there. They could have
been carried on an angler's waders, or come from a local
trout hatchery. When they showed up in the Great Lakes,
it was believed that they were carried in the ballast
of European ships, where the snail had already established
But when they showed up in the Madison and Firehole rivers
in Yellowstone, the Henry's Fork of the Snake River, the
Green River tailrace below Flaming Gorge Reservoir in
Utah, and Boulder Creek, it is almost a certainty that
they were carried there on the wading gear of fly fishermen.
If you look at where the organism is found, it seems
to have a real tendency to show up in places where high-end
fly fishers fish, said Pete Walker.
There it is. Those of us who travel around the country
and the world may have had a hand in this latest case
of pestilence over the land.
So what can you do about it? I've heard from some sources
that if you thoroughly dry out your wading equipment,
that will kill the mudsnail. Other sources say take it
a step farther and spray them with soapy water and leave
them in the hot sun for several hours. Still others say
soak the waders and wading shoes in hot water (120 degrees)
for several minutes. The optimists say just thoroughly
clean the mud off your wading shoes and rinse them in
Walker says the one surefire way he's found to kill the
mudsnail is to wrap your wading shoes and waders in a
plastic bag and put them in the freezer overnight. The
one way he says may not kill the snails is to soak them
in the kind of bleach baths that kill the whirling disease
Ultimately, there is one other consideration. It may
be time to hang up the felt sole wading shoes. The felts
are a perfect medium for the mudsnails and the whirling
disease pathogen to be transported no matter how careful
You can make a case that it was harder for the mudsnail
to be transported when fishermen used the old time rubber
soled boot foot waders, Walker said.
Walker added that he and a number of others at the Division
of Wildlife have switched to rubber soled wading boots.
It's something to think about.