ESPN

ST. LOUIS, Mo. — As bighead, silver and grass carp move ever closer to the Great Lakes, a fourth species of carp appears to have joined the foreign invasion that began in the lower Mississippi River.

A black carp was netted this summer, about 90 miles upriver from here.

"We're at the forefront of another invasion, it would appear," said Rob Maher, commercial fisheries biologist for the Illinois Department of Natural Resources.

Maher added that he's troubled by the fact that the fish seems to have moved through two locks and dams before it was finally caught. "The implications are that those structures are probably not going to prevent those guys from moving north," he said.

Before that 11-pound carp was taken in a hoop net, a black carp was caught in an Illinois backwater near the confluence of the Ohio and Mississippi rivers, and an angler caught one that weighed nearly 30 pounds in Louisiana's Red River. That angler said he'd been catching them occasionally in the area for years.

As with the other exotic carp that are crowding out native species on the nation's rivers and threatening to invade the Great Lakes, black carp were brought into this country by fish farmers. They wanted them to eat snails, which harbor parasites that threaten their commercial catfish operations.

Black carp used by the fish farms are supposed to be sterile, unlike early introductions of other carp species. In all cases, however, fish farmers promised that the exotics wouldn't escape. And, if they did, they wouldn't reproduce. Those same arguments are being used today for black carp.

"When I hear of three or four black carp being caught, it doesn't indicate a problem to me," said Ted McNulty, vice president for aquaculture at the Arkansas Development and Finance Authority.

Not surprisingly, states such as Arkansas and Mississippi, both with strong aquaculture lobbies, are primary contributors to the invasive problems now plaguing so many other states.

While silver and bighead carp compete with native fish species for food and habitat, the black carp threatens endangered snail and mussel populations. Even just a few escaped black carp that are sterile can pose problems. Each one can live 15 years or more and eat huge quantities of shellfish.

"The mussels have a hard enough time making it on their own right now," said Ron Benjamin of the Wisconsin Department of Natural Resources. "They don't need an extra predator out there working them."

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