Lake Invaders

Flying, fearsome Asian carp have already taken over much of the Mississippi. Can electrical barriers keep them out of the Great Lakes--or do we need to block the waterways to keep the fish from spreading?

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Ben Lowy for TIME

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If the Asian carp do take over, it would most likely be through the Chicago Sanitary and Ship Canal, the only connection between the Mississippi River system and the Great Lakes. The canal is the Thermopylae in the war against the carp, and the Army Corps of Engineers has done its best to close off the pass, installing underwater electrical barriers about 30 miles (48 km) downstream from Chicago. The barriers send a small jolt of juice across the water, enough to repel any approaching carp while allowing free passage to ships and sewage. (The canal carries Chicago's treated waste.) The corps is also looking into backup measures, like an additional barrier that uses acoustics and bubbles to dissuade incoming carp, as well as longer-term strategies, so officials believe they can defend the Great Lakes. "I feel confident that working together with other agencies, we can do this," says Colonel Vincent Quarles, the commander of the Chicago district of the corps.

But some environmentalists and politicians worry that the corps's barrier system is far from impregnable. Researchers from the University of Notre Dame have found carp DNA in Lake Michigan, and earlier this summer a fisherman caught a 3-ft.-long (1 m) bighead carp in Lake Calumet, which is upstream of the electrical barriers. That doesn't mean the barriers aren't working — some scientists think the fish that was caught might have been introduced directly into Lake Calumet by a person, and the same possibility could account for the presence of any other carp in Lake Michigan. Then again, the barriers were shut down for a short time in 2008, which might have allowed carp to pass through. Plus, flooding can link the canal and the nearby Des Plaines River, giving Asian carp a chance to bypass the barriers altogether.

Critics of the all-out anticarp offensive argue that the fact that so few live carp have been found past the barriers indicates that they're working. But carp are hard to catch, especially if their numbers are still small. "If there were a thousand fish in Lake Michigan, we might have no idea for sure for a long time," says Duane Chapman, a biologist with the U.S. Geological Survey. "We can't rule out that possibility."

For those who really fear the fish, the mere possibility of their presence is enough to call for more drastic measures, including closing the locks on the Chicago canal to seal off a water route from the Mississippi to the Great Lakes. Business interests in Illinois have fought hard against that course, arguing that the economic damage inflicted by closing the shipping lanes would far exceed the damage carp could cause if they slip past the barriers. The shipping advocates are also pushing an environmental angle. "A single barge on the canal carries 80 truckloads of material that would instead have to be on our roads," says Jim Farrell, executive director of infrastructure at the Illinois Chamber of Commerce. "It's irresponsible."

The lawsuit filed by Michigan's Cox and other state attorneys general isn't likely to succeed — the Supreme Court denied similar attempts earlier this year. But even with the Obama Administration spending nearly $80 million on Asian-carp control, more may need to be done. The fish is hardly the only invasive species threatening the Great Lakes. There are more than 180 alien species in the system, including zebra mussels, round gobies and sea lampreys, that can go back and forth between the Mississippi and the lakes. Beyond beefing up surveillance of international shipping — many invaders hitch a ride inside the ballast water of container ships — blocking off the waterway is the only sure way to prevent the carp and other species from making a home in the Great Lakes. Or, to borrow the words of Nicholas Schroeck, executive director of the Great Lakes Environmental Law Center, "How much longer will we battle this stupid thing when we could get a much better solution by instituting a physical barrier?"

As I'm zipping around the river during the fishing tournament, I have to admit that for a brief, sunny moment, having a lot of Asian carp around seems less an ecological disaster than a totally excellent sporting adventure. But then Nayden hits a school of carp, and suddenly the sky is filled with fish, like shrapnel from a grenade burst. They're coming at us from all directions. I flinch as one hits me square in the stomach, leaving behind blood, scales, slime and one ruined shirt. O.K., carp — now it's war.

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