PITTSBURGH

Massive carp that have been known to jump some 10 feet out of the water and wallop boaters in the Mississippi River have been spotted in Lake Erie, raising fears that the nonnative species may spread throughout the Great Lakes. The bighead carp are just another example of invasive species threatening ecosystems.

In Maryland, it was snakeheads — predatory fanged fish from Asia that are able to move on land. Flathead catfish, native to western Pennsylvania waters, have been caught in the Susquehanna and Schuylkill rivers. And several pacu, a mostly vegetarian cousin of the piranha, were caught in the Ohio River near Pittsburgh last fall.

While some nonnative fish are probably dumped from home aquariums and unable to survive for long — which state fish biologists think was the pacus' fate — fisheries experts say invasive fish have the potential to cause havoc with aquatic ecosystems.

"They can compete — and sometimes out-compete — with the native wildlife for food in that area, which can throw the ecosystem off," said Mitch Snow, a U.S. Fish and Wildlife Service spokesman.

That happened with zebra mussels.

Brought to the United States in the ballast water of oceangoing ships in the 1980s, zebra mussels spread rapidly through the Great Lakes and other inland waterways and have caused millions in damage to power plants and boats.

Only a couple of bighead carp have been caught in Lake Erie, though some biologists believe they spotted one July 17.

Robert Wellington, an aquatic biologist with Erie County health department, was with some colleagues and a group of students in Presque Isle Bay when a massive fish surfaced.

"I would estimate that it could have been between 30 and 50 pounds," said Wellington, a lifelong angler. Others in the boat said it was about 5 feet long. "It was a tremendous fish," he said.

Though they tried to catch it, they couldn't.

"Until you get it in your hands, it's pretty much a fish tale," Wellington said.

Chuck Murray, a biologist with the Pennsylvania Fish & Boat Commission, said the fish sounded like a bighead carp, though he isn't that familiar with it.

The fact that so few have been caught or spotted indicates they have not been able to breed, he said.

Marc Gaden, a spokesman for the Great Lakes Fisheries Commission, said most biologists believe the bighead carp sightings in Lake Erie have been isolated incidents.

But fisheries experts fear they will adapt eventually to the Great Lakes. Bigheads have been spotted as close as 25 miles from Lake Michigan in a canal connecting the lake to the Illinois River, a tributary of the Mississippi.

The Army Corps of Engineers has erected an electrical barrier that hopefully will stop the fish, Gaden said.

"This has all the makings of another zebra mussel," he said. "Once the species makes the Great Lakes their home … you can't get rid of them."

Bigheads were imported from Asia in the 1970s and 1980s to control plankton in fish farms in the south, said Jerry Rasmussen, a biologist with the U.S. Fish and Wildlife Service and a coordinator with the Mississippi Interstate Cooperative Resource Association.

"I've seen them jump into boats and I've seen them jump 6 to 10 feet into the air," he said. "They're pretty astounding."

Though he hopes the barrier works, he said there's a good chance they'll get in.

Snakeheads are believed to have been eradicated from the Maryland pond in which they were found. They are in Florida waters and are sold live in some pet shops.

While it's always been illegal to release live snakeheads into the state's waterways, the commission is making it illegal to sell or possess the fish, said Dan Tredinnick of the Pennsylvania fish commission. Snow said the federal government has proposed a similar measure.

The threat — or benefit — of nonnative fish isn't new.

Sport fish such as rainbow and brown trout and smallmouth bass were introduced into Pennsylvania waters more than a century ago.

"A century ago, the idea was, 'Let's see what we can grow here,' but the view of how fisheries should be managed has changed," Tredinnick said.

MINNESOTA OUTLOOK:

It is "not very likely" that bighead carp have reached Lake Superior, said Jay Rendall, exotic species program coordinator for the Minnesota Department of Natural Resources.

"We've been expecting to see the bighead and silver carp in the Mississippi River in the southernmost part of Minnesota," Rendall said. "Boaters and anglers should expect to see them there this year or next."

Anyone who believes he or she has caught a bighead carp in Minnesota should take the fish to the local DNR Fisheries office for identification or call the Exotic Species Program at (651) 296-2835, Rendall said.