(AP) -- After nearly four decades as a fishing guide on the Great Lakes, Pat Chrysler has seen enough damage from invasive species to fear what giant, ravenous Asian carp could do to the nation's largest bodies of freshwater.
"It's like introducing piranhas to the Great Lakes," Chrysler said from South Bass Island in Lake Erie, which teems with walleye, perch and other fish that draw anglers from near and far.
Federal and state officials are mounting a desperate, last-ditch effort to prevent the marauding carp from breaching an electrical barrier and slipping into the Great Lakes from the Mississippi River. Michigan is drawing up a lawsuit demanding the closing of shipping locks between the lakes and the Mississippi. And last week, Illinois officials poisoned a six-mile stretch of a canal to wipe out any of the carp.
The prospect of a carp invasion alarms environmentalists and people whose livelihoods depend on a strong fishing and tourism economy, from charter boat skippers to those who sell bait and tackle, rent personal watercraft and operate lakefront restaurants and motels. The Great Lakes fishing industry alone is valued at $7 billion a year.
"I'm afraid they can wipe us out in a hurry," said Jim Conder, a charter boat operator on Michigan's St. Joseph River, which flows into Lake Michigan. "We need to spend all we can to keep them out."
Over the years, parasitic sea lampreys, zebra mussels and other invasive species have killed trout and birds, left prized salmon and whitefish skinnier, and done other damage to the lakes.
Now, many fear that the despised Asian carp, which can reach 4 feet long and weigh up to 100 pounds, will wreak havoc, too - not by attacking native fish, but starving them out by gobbling up plankton.
The carp were imported from Asia to cleanse fish ponds and sewage lagoons in the Deep South but escaped into the Mississippi and have been working their way north since the 1970s.
Much is unknown about what will happen - and how quickly - if they conquer the Great Lakes. But the carp's ability to take over is evident in places like the Illinois River, where it has caused native fish such as gizzard shad and bigmouth buffalo to go hungry.
They are also apparently spooked by the sound of motors and have a nasty habit of leaping from the water like missiles and colliding with boaters with bone-breaking force.
Steve Munton of Fulton County, Ill., said Asian carp tore his nets, and one jumper knocked his pet Labrador out cold. "They're nuts," he said.
Tavern manager Betty DeFord of Bath, Ill., recalled a battle with soaring carp during an excursion on a 16-foot craft about five years ago. "They just about swamped us. They were like flying torpedoes," she said. "We were hitting them with a broom, boat oars, anything."
Afterward, DeFord's family established the Redneck Fishing Tournament "to get those carp out so we can take back the river." But their population explosion continues.
Fishing for Asian carp isn't an attractive option for many anglers. Salmon are fighters and fun to pursue, while the carp have small mouths and aren't inclined to bite at baited hooks. Also, most Americans would much rather eat salmon, walleye or whitefish. While Asian carp's defenders say their meat is tasty, they are quite bony.
Mike Schafer, owner of a processing plant in Thomson, Ill., sells about 100,000 pounds a week for human consumption overseas or conversion into fertilizer. "We're the only country in the world that looks at a carp as a trash fish," he said.
For now, the carp are being kept at bay by an electric barrier in the Chicago Sanitary and Ship Canal, part of the waterway linking the Mississippi with the Great Lakes. The barrier emits electric pulses to scare off approaching carp and gives a non-lethal jolt if they don't take the hint.
Critics, including environmentalists and Michigan officials, questioned the electricity's effectiveness after Asian carp DNA was found past the barrier this fall. Some want to sever the century-old, manmade route between the Mississippi and the lakes - a proposal strongly opposed by tug and barge companies that haul millions of tons of iron ore, coal, grain, scrap metal and other cargo on the waterway.
Even if a few Asian carp reach the lakes, "it's not the end of the game yet," said Phil Moy, a researcher with the University of Wisconsin. In fact, a few have turned up in Lakes Erie and Michigan over the past couple of decades but apparently didn't reproduce.
To gain a foothold, they would have to multiply in large numbers. And U.S. Geological Survey biologist Duane Chapman said it could take years - even decades - for carp to bring ruin to valuable species such as salmon and whitefish.
"Will they grow and reproduce enough to be a huge player in the ecology? Can't say for sure," he said. "If they are successful, I can't think of a positive outcome."
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Next-door leopards: First GPS-collar study reveals how leopards live with people