Killing Chicago River may stop infestation

CHICAGO -- It's impossible to kill all the exotic species sloshing between the Great Lakes and the Mississippi River basin, so some scientists suggest killing the river that links the two watersheds.\nIt's a radical long shot of an idea that bucks the federal Clean Water Act. But the fact that some wildlife advocates would even think of returning the Chicago River to its former, sludgy self underscores the ecological and economic disaster wrought when Asian carp, zebra mussels and other undesirables emigrate.\n"Take the oxygen out of the water," suggests Jerry Rasmussen, a river biologist for the U.S. Fish and Wildlife Service. "We've done marvelous things with the Clean Water Act, and nobody wants to undo that."\nBut shutting down the river's aeration system would effectively halt migration until scientists come up with a better answer, he said.\nZebra mussels, now drifting from Lake Michigan to the Mississippi 300 miles away, already have cost an estimated $5 billion in clogged water intakes and damage to fisheries, according to the U.S. Environmental Protection Agency. Now officials fear a repeat in the other direction, as giant carp work their way from the Mississippi toward the lakes.\nThe Chicago River flows backward, away from Lake Michigan, because 19th century Chicagoans engineered it to carry pollution away from their beaches and into a canal. The canal flows to the Illinois River, a tributary of the Mississippi, creating a link unintended by nature.\nBefore aerators, in the 1970s, Chicago's waste choked the river and canal so that no fish could swim through and live. The Metropolitan Water Reclamation District has since brought the manmade waterway into federal compliance.\nThe new urgency comes with the Asian bighead carp, a potential 100-pound home wrecker. Imported to clean Mississippi Valley fish farm ponds, the plankton-straining fish escaped in floods and now are within 25 miles of Lake Michigan. Rasmussen and others fear bigheads could destroy the lakes' food chain.\nAs large river operations coordinator at the wildlife agency's Rock Island, Ill., field office, Rasmussen made the river-killing suggestion as one of several options in an analysis he wrote for cooperating agencies.\nOther state and federal biologists agree it could be effective, but politically difficult.\nStates routinely use fish kills to remove nonnative or "trash" fish. In September, Maryland sprayed poison on a 4-acre pond to kill it and the more than 1,000 rapacious Asian snakehead fish in it.\nMark Pegg and his crew at the Illinois Natural History Survey are working on something prettier. The carp reached their lab on the Illinois River at Havana in the mid-1990s, 150 miles upstream from the Mississippi. Bigheads now dominate the river there.\n"We'll catch easily 100 before we even get the net set," Pegg said. Many are about 8 pounds: 2-year-olds that could grow tenfold.\nFor science, at least, the abundance is good. Last month the researchers needed a steady supply to test gadgets aimed at blocking their migration.\nThey had already tested two sets of four electrodes across an eight-foot-wide raceway trough at a nearby state fish hatchery. In unblocked troughs, fish patrolled from one end to the next. But at the 56- and 118-volt electrodes, 98 percent turned tail.\nEffective, but not failsafe.\nOn a cold November day, aquatic ecologist Ron Taylor drew on coveralls, a vest and knit cap to sit in a lawn chair above the raceway for six hours. The gimmick this time: a wall of compressed-air bubbles bombarded with a mechanical whooping sound from underwater speakers.\nEach time a carp approached and turned away, he marked a success on his clipboard. Then two made a run and jumped over.\n"They might have been agitated by the sound," he said.\nThe bubble-and-noise barricade so far has a success rate of about two-thirds.\nNext up is a test of the bubbles, bleeps and electrodes all together.\nPegg also plans tests of heated water and a nitrogen plume that would suffocate the channel as Chicago's waste once did.\nOne experimental electronic barrier was planted across the canal at Romeoville southwest of Chicago last spring. In November the federal government, International Joint Commission and Great Lakes Fishery Commission paid $300,000 for the Army Corps of Engineers to install a backup generator. The Corps is considering a larger, second electronic barrier.\nSome supplemental suggestions are as low-tech as the channel catfish. Phil Moy, invasive species specialist with the Wisconsin Sea Grant Program, suggests loosing an army of predators between two bubble or electronic barriers, to eat wayward juveniles.\n"It's kind of neat to think that maybe you could even have some kind of trophy fishery in there," Moy said.\nMoy used to work for the Corps of Engineers and championed the electronic barrier at Chicago. He's intrigued by the idea of killing the river for a stretch. But both he and Rasmussen acknowledge that's a tough sell because it sets an ugly example.\nIndeed, the city of Chicago wants to help, but not in that way. \nCity Environment Commissioner Marcia Jimenez said she worries about damage to other plants and animals, and wouldn't endorse shutting off aerators "without a great deal of research."\nMayor Richard Daley is lobbying Congress and agencies for more barrier funding, Jimenez said.\nBut even building a new Hoover Dam wouldn't guarantee protection.\n"Asian carp may get into the Great Lakes even with the barriers in place," said Sarah Whitney, program manager with the Great Lakes Commission in Ann Arbor, Mich. "Someone may like to eat them and decide it's a good idea to release them."\nStill, she said the Great Lakes Commission backs the research and potential new barriers. No sense giving up.\n"Otherwise I'd just go home and cry," she said.