Research Murky On Danger of Asian Carp Invasion

Carp
Associated Press + More

By JOHN FLESHER, Associated Press

HAVANA, Ill. (AP) — As scientists aboard a research boat activate an electric current, the calm Illinois River transforms into a roiling, silvery mass. Asian carp by the dozen hurtle from the water as if shot from a gun, soaring in graceful arcs before plunging beneath the surface with splashes resembling tiny geysers.

Water quality specialist Thad Cook grunts as a whopper belts him in the gut. His colleagues duck and dodge to avoid the missile-like fish that plop onto the deck, writhing madly until someone can grasp the slimy, slithering critters and heave them over the side.

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It's like a scene from a Hitchcock movie — and indeed the flying carp have played villainous roles in many a YouTube video. Biologists, however, fear a different kind of horror story may be taking shape underwater: a war for survival between the aggressive Asian carp newcomers and native species important to people who catch fish for a living or fun.

"We suspect at some point there will be a real crash in the populations of some of these native fishes," said John Chick, an aquatic ecologist with the National Great Rivers Research and Education Center on the Mississippi River near St. Louis.

While years of study have turned up ominous signs that the carp are capable of crowding out other species and changing ecosystems, the worst-case scenario scientists expect to unfold hasn't yet been realized. Some scientists say that dire predictions about the damage carp can do may be premature. That makes the research Chick and his colleagues are conducting critical: It likely will influence how the debate over managing waterways made vulnerable by carp plays out in Congress and the courts.

U.S. research so far has focused on rivers, where Asian carp are most plentiful. A common method for determining which fish are in a given location is to shoot an electric charge into the water that temporarily stuns them so crews can scoop them up in nets. Silver carp, an Asian type known for springing from the water when startled, manage to jump first.

Imported decades ago to cleanse algae-choked aquaculture ponds and sewage treatment lagoons, they escaped during floods and have marched up the Mississippi watershed in more than two dozen states, ranging as far as Kansas and the Dakotas. They're taking dead aim at the Great Lakes, with the leading edge on the Illinois River some 55 miles south of Lake Michigan, although their DNA has been found in Chicago a mere 6 miles from the lake.

"All you've got to do is look at tributaries of the Mississippi or Ohio rivers and you'll find them," said biologist Ron Brooks of the Kentucky Department of Fish and Wildlife Resources.

Those environments are hotbeds for research, and could foretell what will happen if carp invade other waterways. What's missing, though, is smoking-gun evidence that Asian carp will devastate other fish. Even in places such as the Illinois and Mississippi, where carp are rampant, changes have been incremental.

For example, while indigenous bigmouth buffalo and gizzard shad both have gotten skinnier since the carp arrived, the buffalo's population has declined only moderately while the shad have fluctuated. Commercially harvested buffalo are found on grocery shelves from Alabama to Minnesota. The shad are crucial prey for bass and other sport fish.

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"When you get a species invasion ... typically you see some native species decline or go extinct locally," said biologist Jim Garvey of Southern Illinois University at Carbondale. "We haven't seen that yet. We're kind of wondering what the heck's going on."

Chick and others have found that silver and bighead carp, the most menacing of several Asian varieties in the U.S., eat the same food as the bigmouth buffalo and gizzard shad. A separate study detected weight declines among buffalo and shad in the Illinois River, believed to have the largest concentrations of Asian carp.