Conservation groups called for immediate measures to close all Illinois gateways and locks with access to Lake Michigan in a last-ditch effort to keep the destructive Asian carp from invading the Great Lakes after it was learned Friday, November 20, that carp have likely advanced past the electric barrier designed to keep them out and are present just six miles south of Lake Michigan. Carp DNA, but not actual fish, has been detected in water samples taken past the electric barrier, the Army Corps of Engineers acknowledged Friday. This puts the species about 20 miles closer to Lake Michigan than previously thought.

Even as researchers learned the carp had likely breached the barrier, an emergency plan is being made to treat six miles of the Chicago Sanitary and Ship Canal with a fish-killing poison to avert a Great Lakes invasion by the oversized Asian carp. The plan is to be put in place December 2.

The U.S. Army Corps of Engineers will shut down the southernmost of two electric barriers in the canal for routine maintenance on that date. Erected to keep Asian carp out of Lake Michigan and the other Great Lakes, the barrier was turned to high voltage earlier this fall to ward off carp that have been drawing ever nearer.

Working in concert with the corps, the Illinois Department of Natural Resources plans December 3 to treat six miles of the canal between the barrier and the Lockport Lock and Dam with rotenone, a pesticide that is deadly to fish but does not present a risk to people and wildlife.

The pesticide is needed to prevent any fish from reaching the weaker northern barrier – the final stop before the Asian carp gain passage to the world’s largest surface freshwater system. Water quality experts with the Illinois Environmental Protection Agency will be monitoring downstream of the application zone to ensure the waters of the state are protected, and the chemicals do not move beyond the designated application area.

The chemical plan underscores the need for a permanent solution to keep the invasive species out of the lakes, the Alliance for the Great Lakes reported.

“Today the carp are backing the Great Lakes into a corner and we need to hit back with everything we’ve got,” said Joel Brammeier, Alliance for the Great Lakes acting president. “When the deed is done, we’ve got to focus like a laser on separation of the lakes from the Mississippi River so we don’t have to use this drastic technique in the future.”

Once the southern barrier is powered down, Mr. Brammeier said it would be an open invitation for the carp to swim upstream to the second barrier. Its voltage cannot be turned high enough to keep out all the fish. With the southern barrier in need of routine maintenance, and the carp circling nearby, the corps and the state have few options but to use rotenone to stop the fish’s movement upstream, according to the Chicago-based Alliance.

“This is a price we have to pay to protect the Great Lakes,” said Mr. Brammeier, who also said the situation should never have been allowed to reach this point. “And the only way to stop the bills coming due is to eliminate the problem – permanently.”

Work crews will remove the fish from the canal and dispose of them in a landfill following the procedure. The water in the canal will be treated with potassium permanganate, an antidote that neutralizes the effects of the rotenone.

The Alliance last year issued a report calling for physically separating the Mississippi and Great Lakes basins. The two watersheds are joined by the Sanitary and Ship Canal, an artificial connection engineered more than a century ago to carry Chicago’s wastewater away from Lake Michigan.

In October, conservation groups demanded that the corps build an emergency physical barrier between the Sanitary and Ship Canal and the adjacent Des Plaines River, which is infested with Asian carp. The emergency barrier is needed to prevent the carp from being swept into the canal past the electrical barrier in the event of flooding.

Known to batter boaters and even knock them into the water at the sound of a passing motor, Asian carp are non-native fish that are already seriously damaging the environment and economy of the Mississippi River and threaten to do the same in the Great Lakes, the Alliance reports. Voracious feeders, they were first brought to the area decades ago by a fish farmer and have infested waters of the Mississippi River basin.

The carp, specifically the bighead and silver carp, can grow to more than four feet long, weigh up to 100 pounds, and quickly dominate a body of water by gobbling up the same food that sustains native fish populations.

If the carp make their way into the Great Lakes, they could devastate the region's $4.5 billion fishing industry and change forever how recreational boaters, anglers, and tourists relate to the lakes, the Alliance reports.