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Giant Asian carp lurk at doorway to Great Lakes
July 15, 2002
By Sabrina Eaton
Say hello to the giant Asian carp, the latest foreign invader to menace the Great Lakes.
They're big, sometimes exceeding 100 pounds. They've crowded other fish out of the Mississippi River and its tributaries. Scientists fear they will infiltrate Lake Michigan within a year and spread throughout the Great Lakes unless an experimental barrier outside Chicago stops them.
'They are a huge threat to the Great Lakes and could disrupt the food chain in ways that would be very difficult to predict,' said Gary Isbell, who heads the Ohio Department of Natural Resources' fisheries management program.
But local scientists are less certain.
'As with zebra mussels and every other foreign species, it's very difficult to predict what impact it will have and very difficult to control once it's introduced,' said Rich O'Neal a fisheries biologist with the Michigan Department of Natural Resources.
'It can't be good to have them in Lake Michigan, but we don't know yet if they would be a curiosity or a disaster,' said Chuck Pistis, an agent for Michigan Sea Grant.
Although Asian carp have been caught twice in Lake Erie, biologists believe those specimens do not signify an infestation because they probably were set free by people who bought them at Asian food markets. A 47-pound sample caught last year in the Ohio River also was an isolated find, said Isbell, who believes it swam all the way from the Mississippi River.
'They're strong swimmers,' he said.
Asian carp are several fish species native to China and Siberia that were imported by fish farms in the southern United States. They escaped into the Mississippi River during floods in the 1980s, and rapidly spread north into tributaries such as the Illinois River. A U.S. Fish and Wildlife survey conducted last month found them just 55 miles south of Lake Michigan.
'They tend to eat almost everything in their path,' said Dick Munson, executive director of the Northeast Midwest Institute think tank in Washington, D.C. Already, he said, 97 percent of fish in some sections of the Mississippi River are now Asian carp.
Lake Erie Commission Executive Director Jeff Busch said the fish aren't tasty and don't make good sport fish. If many got into Lake Michigan, he said, they'd certainly spread to Lake Erie.
'It's all one big, connected waterway,' said Busch. 'It might happen quickly, or it could take a long time.'
Environmentalists fear the monster fish will crowd out local species by eating huge amounts of the tiny plankton they rely on for food. They say one type of the fish eats mollusks and could devastate endangered native shellfish already being pushed aside by zebra mussels.
But there's a way they threaten humans directly: acrobatics.
The giant fish leap out of the water for no apparent reason and land on people and watercraft, said Pam Thiel of the U.S. Fish and Wildlife Service office in La Crosse, Wis.
Thiel said one recently struck an unsuspecting commercial fisherman on Illinois' Kaskaskia River and broke his nose. A research biologist in Illinois was hit four times by jumping carp, once so hard that he filed a worker's compensation claim. In the St. Louis area, the fish often land on the canopy of an Army Corps of Engineers boat.
'When you're dealing with something that size, it's shocking,' said Marc Gaden of the Great Lakes Fishery Commission in Ann Arbor.
Biologists hope an electronic barrier recently built across a canal that separates the Mississippi River water system from Lake Michigan will contain the invaders. It cost more than $1 million, and Great Lakes activists are requesting federal money to install improvements such as a backup power system.
Illinois Department of Natural Resources biologist Rich Hess said the barrier consists of cables on the bottom of the Chicago Sanitary and Ship Canal that sends electric current through the water to discourage fish from crossing.
While the system worked well in laboratories, Hess said, it has never been field tested. Researchers plan to place transmitters on other species of test fish to determine whether the barrier blocks them, he said.
Hess said it is uncertain whether the barricade would stop larvae that might flow through the canal.
, and whether the current it supplies would be enough to turn the fish away without stunning them. A stunned fish might float through the canal and recover on the other side of the barricade.
The fish also might be spread by anglers who unwittingly pick up small fry to use as bait and later dump them in different waterways, biologists say.
'We may have to go through some novel experimental regimes,' said Hess. 'It's a real challenge.'
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