clams claim a new toehold
Troublesome zebra mussels are found in a Crow Wing County
By John Myers
Duluth News Tribune
The first infestation of exotic zebra mussels in a northern
Minnesota inland waterway has been confirmed at Lake Ossawinnamakee
in Crow Wing County.
The outbreak was confirmed last week and reported Tuesday
by the Minnesota Department of Natural Resources.
Exotic species experts fear the small clams could begin
to spread throughout the resort, cabin and fishing waters
that are the hallmark of the North Country and the Land
of 10,000 Lakes.
Wherever zebra mussels have been found, they have become
a costly problem, financially and environmentally. But
the impact of zebra mussels on small, inland lake ecosystems
isn't fully understood. And their impact on tourism and
fishing hasn't been studied here.
Lake Ossawinnamakee is south of the famous Whitefish
chain of lakes on the Pine River system, upstream from
the Mississippi River.
The infestation, discovered by a boat lift installer,
was so thick that DNR scientists are sure the mussels
are reproducing in the lake.
"It's bad news. They've jumped a couple hundred
miles north into an area where Minnesotans do a lot of
recreating," said Gary Montz, DNR aquatic invertebrate
biologist. "It's not good news for an area with so
many lakes so close together."
During a followup inspection, DNR staff also found mussels
in cracks of rocks, along contours of a minnow bucket
and other tight areas of boat lifts and docks -- from
the shoreline to 18 feet deep.
It's not clear how long the mussels have been in the
644-acre lake or how they got there.
Officials will try to isolate the mussels to keep them
from spreading. But that could be difficult, if not impossible.
The larval stage of the zebra mussel can flow freely
with currents for several weeks. And adults can attach
themselves to boats and hitchhike for miles upstream,
even surviving out of water for a time.
"That lake becomes a continuous source now for everything
downstream. And boats can move them around," said
Jeff Gunderson of the Duluth-based Minnesota Sea Grant
program, which has tracked zebra mussels for 15 years.
"It's going to take even more effort now to continue
to get boaters and anglers to keep from spreading them
Public education and law enforcement will play a key
role in trying to curb their spread.
Boaters are required to inspect their boats upon leaving
a lake and remove any exotic species or weeds. Boaters
are asked to dry or disinfect their boats between lakes
and to not transport any water, even minnow buckets, from
lake to lake.
Boaters across Minnesota also are required to drain water
from live wells, bilges and bait buckets before leaving
infested waters. The harvest of bait from infested waters
On parts of the Great Lakes, the mussels have covered
virtually every smooth surface since they began to take
hold in 1988. They have caused the extinction of native
mussels, covered fish spawning beds and cost industry
and government millions of dollars annually to remove
from water intakes, docks and sea walls. Their long-term
impact on native fish populations remains to be seen.
More than 180 inland lakes in Michigan are infested with
zebra mussels, likely due to recreational boaters moving
from the infested Great Lakes to others in the state.
A few lakes have been infested for a decade.
"The water usually becomes clearer, which means
they are intensively filtering nutrients out of the water.
Increased water clarity means more rooted plants, more
weeds," said Carol Swinehart of Michigan Sea Grant.
Professor Orlando Sarnelle of Michigan State University
has studied the impact on lakes infested with zebra mussels.
While they reduce the overall algae, he said they cause
more blue-green algae -- up to five times more than normal
-- which can be toxic to animals and people.
"The problem is especially bad in clear lakes,"
he said. "And it's a biodiversity issue with them
driving native mussels to extinction."
Sarnelle also noted that zebra mussels in Lake Michigan
appear to be eliminating a small shrimp-like organism
that is the backbone of the big lake's fishery.
Another researcher is looking at the impact of zebra
mussels on the growth rate of panfish.
Lake Ossawinnamakee is only the second inland lake in
Minnesota found to be infested with zebra mussels. The
first was Zumbro Lake near Rochester, which became infested
about three years ago. Both the Mississippi River north
to the Twin Cities and the St. Louis River estuary in
Duluth-Superior also are infested.
On Zumbro Lake and along the Mississippi River, swimmers,
water skiers and hikers have complained of cut feet from
zebra mussel shells. Hunters have reported their dogs
have cut feet on the sharp little shells.
In the Duluth-Superior harbor, walleye anglers commonly
snag sticks, native clams and other objects covered in
zebra mussels. But, as in Lake Erie, massive numbers of
zebra mussels haven't seemed to adversely affect walleye
fishing -- at least not yet.
"You can't say with certainty how they'll affect
any one body of water. They surprise you," Montz
Any cabin owner or business that draws water from a zebra
mussel-infested lake can expect to have problems keeping
their intake pipes unclogged, experts say.