CHICAGO -- A makeshift electrical barrier in the Illinois River is the only thing that keeps Asian carp from moving upstream into the Great Lakes. But the barrier failed to prevent round gobies from spreading downstream from the lakes.
Biologists and bureaucrats warn that unless the federal government refits the initial electrical weir and builds a second one a short distance downstream, the odds are that within a few years the Great Lakes could become overrun by giant Asian carp.
The barrier is on the Chicago Sanitary and Ship Canal, about 40 miles downstream from America's third-largest city.
Researchers are trying to determine how susceptible Asian carp are to rotenone, a poison used commonly by wildlife agencies to kill unwanted fish. But rotenone kills indiscriminately, knocking off species valued by anglers. It also kills insect life and other invertebrates.
Dennis Schornack, the American chairman of the International Joint Commission, said that if Asian carp were found above the barrier, "We'd nuke the river with rotenone and kill everything in about a five-mile stretch downstream. It would be a terrible public relations problem. But we'd have no choice. We don't want to see the Great Lakes as a giant carp pond."
The commission oversees Great Lakes issues.
Schornack said biologists from the Illinois Department of Natural Resources and the U.S. Fish and Wildlife Service will watch for signs of carp in a large pool on the canal just downstream from the barrier.
If an Asian carp is seen there, commercial fishermen will be hired to bring in nets, and "if we caught more than one or two of them, we'd treat the whole pool with rotenone," he said.
Schornack, a one-time policy adviser to former Michigan Gov. John Engler, said the existing barrier was meant to be temporary. It was built to keep round gobies, which came to the Great Lakes in the ballast of ocean-going ships, from moving downstream to the Illinois River.
That didn't work. Gobies have been found below the barrier. No one knows if the barrier will work in reverse to keep the carp from going upstream.
If Asian carp enter the Great Lakes, scientists say, they could filter so much plankton out of the water that it could cause the collapse of entire ecosystems by disturbing the food chain.
"We've already seen how the waters in the Great Lakes have cleared because of the introduction of zebra mussels," Schornack said. "One of these things filters as much water a day as thousands, maybe millions of mussels."[/b]
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