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Great Lakes
Article:
New lake threat:
Asian carp
05/06/2002
BY
GARY WISBY ENVIRONMENT REPORTER
One
barrier is in place and others are in the works against
a finny invader that weighs up to 60 pounds, eats so much
it threatens to starve out other fish and breeds so fast
that Australians nicknamed it "river rabbit."
Wildlife
officials fear the Asian carp will penetrate Lake Michigan
soon, if it hasn't already.
Today,
they will officially open an electrified barrier in the
Chicago Sanitary and Ship Canal at Romeoville. About four
years in the making, the $1.6 million device originally
was intended mainly to repel another invasive fish, the
round goby, in case it migrated downriver to the Illinois
and Mississippi rivers beyond.
Origin:
China; escapees from Arkansas fish farms
Weight: 40 to 60 pounds
Length:
39 to 40 inches
Bighead carp's official name: Hypophthalmichthys
nobilis
Silver carp's official name: Hypophthalmichthys
molitrix
Appearance: Small scales, like a trout's; eyes
low on head
Teeth: None in jaws; comblike structures filter
food
Why they're bad: They compete for food with native
fish.
How to stop them: Barriers using electricity, bubbles
or sound
But with the recent population boom among the alien
carp, the barrier has a new purpose: halting, or at least
slowing down, the fish's upriver advance into the Great
Lakes.
The voracious invaders, bighead and silver carp, threaten
the plankton food supply of fellow filter feeders: paddlefish,
gizzard shad and bigmouth buffalo. The carp also compete
with larval and juvenile fish and mussels.
"They are displacing a lot of native fish in the
Illinois and Mississippi rivers," said John Rogner,
director of the Chicago field office of the U.S. Fish
& Wildlife Service. "The concern is that they
have the potential to do the same in the Great Lakes."
Asian carp have been reported in the Joliet area, 25
miles downstream of the Romeoville barrier and 55 miles
from Lake Michigan.
Some may already be in the lake.
"If not, they move a long way in a year,"
said Fish & Wildlife supervisor Pam Thiel. "It's
just a matter of time."
Arkansas fish farmers imported both varieties of carp
in the early 1970s to improve water quality in their pens.
Some escaped, probably in floods, and they started showing
up in the Mississippi River in the early 1980s.
Mark Pegg, who runs an Illinois River station at Havana,
south of Peoria, for the Illinois Natural History Survey,
saw none of them as recently as three years ago. But by
2000, counts showed the Asian carp was already at No.
8.
Another study, counting larval fish moving from the
Chautauqua Wildlife Refuge into the Illinois River, found
the alien was second only to the gizzard shad.
Besides the Romeoville barrier, which, it is hoped,
will shock the carp into making a U-turn, Fish & Wildlife
is considering a couple of other methods.
The fish don't like bubbles, which are bad for visibility,
so a bubble curtain may be installed near the barrier.
The curtain may include sounds of a frequency that would
annoy the carp. Cueing on the bubbles, Thiel suggested
Lawrence Welk.
"In smaller streams, they've tried strobe lights,"
Pegg said. "But the Illinois River is probably too
wide for that to work."
Fish & Wildlife will be trapping round gobies in
June for its annual estimate of their numbers. This time,
it also will be counting carp.
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