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Asian carp threaten to invade Lake Michigan, harm native fish

Asian carp, a humongous plankton-gobbling fish that has been dubbed the underwater lawn mower, is getting so close to Lake Michigan that scientists worry it could wipe out sport fish in the Great Lakes.

Nervous authorities are hoping an electric barrier on a canal near Chicago will prevent the fish from dipping a fin in the Great Lakes.

The Asian carp, which made its way into the Mississippi River from Arkansas fish farms in the 1970s, steadily has swum upstream for years at a pace of 40 to 50 miles a year. It's now near the Quad Cities on the Mississippi and may be only 25 miles from Lake Michigan on the Illinois River.

It can grow so big - more than 100 pounds and four feet long - that it quickly out-muscles any predators. It can jump as high as 15 feet and has broken the nose of at least one commercial angler. It snacks on plankton - the base of the aquatic food chain - at a pace of two to three times its weight each day. That doesn't leave much for other creatures to eat.

While scientists have no idea if Asian carp could survive in the Great Lakes, they don't want to find out.

"The worst case is that they would find it very suitable and very much to their liking, and they would grow to huge population numbers and compete with sport fish like yellow perch, walleye and smallmouth bass," said John Rogner, field supervisor of the U.S. Fish and Wildlife Service office in Chicago.

Quick action urged

On Thursday, a Canadian-American organization that regulates border waters urged officials in both countries to take action to prevent Asian carp from swimming into the Great Lakes. The International Joint Commission called on authorities to make permanent the electric barrier, which was installed in April to prevent another non-native species from traveling from Lake Michigan into the Illinois River.

The temporary barrier near Romeoville, Ill., on the Chicago Sanitary and Ship Canal, which is scheduled to be removed after 18 months, sends electric signals into the water and produces a tingling sensation that fish find uncomfortable.

To humans, it's similar to the feeling you get when bumping your funny bone, explained Pam Thiel, project leader at the U.S. Fish and Wildlife Service's fishery resource office in La Crosse. The hope is that Asian carp that make it as far as the barrier will turn around.

The commission also recommended installing a second barrier of electricity, bubbles or sound waves on the Illinois River to act as a second fire break to keep out Asian carp. The second barrier could be located near the present one.

"We have a historic opportunity here," said Jim Houston, environmental adviser for the commission.

It's possible people who catch bait in the Mississippi or Illinois rivers could mistakenly introduce Asian carp when they're small by using the bait while fishing in the Great Lakes, Thiel said.

If Asian carp sneak into the Great Lakes, it could be just as devastating as the zebra mussel, another non-native species, Houston said in a phone interview from Ottawa, Canada.

Millions of dollars have been spent to clean up after billions of quarter-sized zebra mussels that attach themselves to ships, docks and other mussels. Houston said any money spent on preventing Asian carp from invading Lake Michigan will end up being much less than the costs of carp decimating native fish populations.

Imported from China

With a face only an Asian carp mother could love, the fish was brought from China to Arkansas fish farms in the early 1970s to improve water quality and control algae blooms. The fish escaped when aquaculture ponds adjacent to the Mississippi River flooded about a decade ago.

Of the four species of Asian carp, two - bighead and silver - are the ones that are the problem in America. They dine on the plankton food supply of paddlefish, gizzard shad, big-mouth buffalo and other filter feeders. They also compete with larval and juvenile fish, and mussels.

Even though they're members of the minnow family, bighead and silver carp grow fast, and as they get bigger, need more to eat.

"Because they are very large, they have to consume large amounts (of plankton), so they're basically swimming around all day with their mouths open," Thiel said.

Between 1988 and 1992, the combined commercial harvest of bighead and silver carp by Illinois anglers in the Illinois and Mississippi rivers was less than 1,300 pounds, Thiel said. By 1994, the yearly catch was more than 51/2 tons, and since 1997 the annual catch has exceeded 55 tons.

Thiel ate Asian carp while visiting China. She said it tastes good, but she had difficulty comparing it to fish commonly consumed in America.

One thing different about the Asian carp here is its leaping ability. Asian carp in Asia aren't known for jumping high in the air like a tarpon.

They seem to be affected by the sound or vibration of motorboats, Rogner said.

Scientists have documented instances, and have the video to prove it, of Asian carp leaping into boats. Thiel heard of a commercial fisherman who got smacked in the face by a carp. A researcher has been hit four times by the carp he was researching, and the last time his injuries landed him on workman's disability.

Some commercial fishermen use cookie sheets as shields from the big flying fish, she said.

Thiel, who does research on the Mississippi River in La Crosse, figures she'll have to come up with a sturdier shield.

"I think if they get as far as La Crosse, I'll use a garbage can lid because it has handles," she said.

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