may fend off invading carp
Tom Meersman and Mark Brunswick
Minneapolis Star Tribune
Minnesota natural resource officials said Tuesday that
they are studying the possibility of building an underwater
electric barrier across the Mississippi River to prevent
the northward spread of Asian carp into the state's waterways.
The barrier, consisting of electrified cables or bars
on the river bottom, would shock fish as they swim toward
it. It might be installed somewhere between the Iowa border
and the Twin Cities if a study concludes that it would
Two exotic species of carp, silver and bighead, have
been expanding upriver since the 1980s, after they were
imported by Arkansas fish farmers and apparently escaped.
The carp, which can weigh more than 60 pounds, are dangerous
When motorboats pass through waters infested with silver
carp, the fish routinely jump several feet out of the
water and sometimes land in boats. The jumping fish have
injured boaters and damaged their equipment.
Silver carp are moving up the Mississippi.Marlin LevisonStar
Tribune"You get blood everywhere, slime everywhere
and green poop, and that's if the fish doesn't fly to
pieces," said Duane Chapman, fisheries biologist
for the U.S. Geological Survey, who has been studying
the carp for the past few years near Columbia, Mo.
Jay Rendall, exotic species coordinator for the Minnesota
Department of Natural Resources (DNR), said bighead carp
have been reported near the Minnesota border south of
La Crosse, Wis., while the silver carp appear to be farther
south in Iowa.
The carp, which are different from the common carp native
to the river, feed on the same plankton consumed by native
mussels, larval fish and even some full-grown fish, such
as the paddlefish, he said. "Because of what they
eat and how abundant they can get, they [Asian carp] are
a significant threat to the whole food web of the river,"
He said the DNR has hired Smith-Root Inc., a fisheries
technology company in Vancouver, Wash., to look at stretches
of the Mississippi -- mostly narrow sites including locks
and dams -- where an electric barrier might be installed.
The study will cost up to $5,000, he said.
Smith-Root built an experimental electric barrier in
a canal that connects Lake Michigan to the Illinois River
last year to prevent Asian carp from swimming up the canal
and entering the Great Lakes. That $1.25 million barrier,
located about 30 miles southwest of Chicago, consists
of several spaced bundles of electric cables across the
bottom of the 165-foot-wide canal. The system emits enough
electricity to deter fish from swimming upstream.
The Asian carp are about 22 miles south of the electric
barrier. It is being tested on several dozen common carp.
Illinois officials, working with Smith-Root, the Army
Corps of Engineers and others, are planning a $7.5 million
permanent barrier nearby.
Ron Martin, aquatic invasive species coordinator for
the Wisconsin Department of Natural Resources, said he
is interested in a proposed barrier on the Mississippi.
Authorities from several state and federal agencies and
universities are scheduled to discuss the preliminary
study results in late October. After that, the Minnesota
DNR will decide whether the project is worth studying
If Wisconsin were asked to help pay for the barrier,
that state's legislators would need assurances that the
technology could stop the fish, Martin said. An electrified
barrier also would affect native fish, which need to move
up and down the river to spawn, he said.
Martin said he supports the study. "Any time you
get 3-or 4-foot carp that are virtually eating machines,
they're going to have an effect on the system," he
said. "Instead of food that would be producing walleye,
northern, bass or a number of other desirable species,
all of a sudden that biomass is going into producing carp."
Vern Wagner, conservation director for the Minnesota
B.A.S.S. Federation, said his group also hopes that the
invasive carp can be blocked. "It is a subject of
concern," he said. "They leap out of the water
and attack people in their boats. None of us wants to
have that happen to us."
However, Wagner said it might be difficult to construct
barriers or gates on the Mississippi.
Pam Thiel, project leader for the U.S. Fish and Wildlife
Service in La Crosse, said locks and dams have slowed,
but not stopped, the movement of silver and bighead carp.
She said the experimental barrier near Chicago is on a
canal that is only about the width of two barges. A similar
structure on the Mississippi probably would need to be
much larger and far more expensive, she added.
"We need to look at the feasibility of this first
and then make a more educated decision," she said.
"But these carp have infected our riverways, and
so it's going to be difficult to find a magic potion or
some physical solution to eliminate them or even slow
Scott Elkins, state director of the Sierra Club, said
constructing barriers "is kind of like putting your
thumb in a dike once the dam is crumbling." Money
would be better spent to educate people about exotic species
and to prevent others from being introduced, he said.