The Army Corps of Engineers acknowledged Friday that tests taken earlier this fall revealed 32 positive DNA samples for Asian carp above the electric fish barrier on the Chicago Sanitary and Ship Canal, some within about eight miles of the shoreline of Lake Michigan.

The Journal Sentinel first reported the apparent barrier breach Thursday, though the Army Corps refused to acknowledge it until Friday morning.

There now appears to be nothing left standing between the supersized, ecosystem-ravaging fish and the world's largest freshwater system other than the constantly swinging gates of two busy navigation locks, and it may be only a matter of time until the fish are jumping and flopping in Lake Michigan waters from Chicago to Door County - and beyond.

"It's a disaster," said Dan Thomas, president of the Great Lakes Sport Fishing Council. "Heads should roll for this."

The Great Lakes commercial and sport fishing industries are valued at over $7 billion annually, and Asian carp pose a threat to those businesses because they can grow bigger than 50 pounds, sometimes much bigger, and they can consume 20% of their weight in plankton per day. That's food upon which every other fish species directly or indirectly depends.

Two distinct Asian carp species have been detected above the barrier, bighead carp and their slightly smaller cousin, silver carp.

Silver carp are considered a particular menace because of their penchant for leaping out of the water when agitated by the whir of a boat motor. The Great Lakes region is home to more than 4 million registered recreational boats, about a third of the U.S. total. Boat owners here may someday have to learn to live on a different and dangerous set of lakes; hockey helmets are considered standard safety gear for some boaters on infested waters of the Mississippi River basin.

Fish evidence, but no fish

No actual fish have been found above the electric barrier, which itself is about 20 miles south of Lake Michigan. But biologists say the water samples provide some compelling - and distressing - evidence that the fish imported decades ago by an Arkansas fish farmer and subsequently let loose during federally funded sewage treatment experiments finally busted past the electric barrier. It is a barrier that has never been turned up to its full capacity due to concerns it would disrupt barge operators and recreational boaters on the Chicago canal.

"We're assuming (the fish) are there because we have to," said John Rogner, assistant director of the Illinois Department of Natural Resources. "It's the best data we have."

The biologists responsible for detecting the fish with cutting-edge "environmental" DNA testing agreed. "There is no reason to think that there aren't carp present when the DNA is detected," said University of Notre Dame's David Lodge.

The tests were taken on Sept. 23 and Oct. 1, and the results were not available to the Army Corps until Tuesday.

Lodge said no DNA tests have been conducted on Lake Michigan itself, but he said there is still reason to be optimistic they would be negative.

"As a biologist and somebody who has spent decades now studying many different kinds of invasive species, we should not assume all is lost because there may be some silver and bighead (carp) above the barrier," Lodge said. "There are lots of cases, well documented from many parts of the world, where a small number of organisms may invade new areas, but they may die out before they establish a sustainable reproducing population. So it's very important to keep the numbers of individual organisms as low as possible."

The Army Corps agrees, and said Friday it will steam ahead with plans to poison the Chicago canal just below the barrier to kill all the fish in a several-mile downriver stretch in early December so the barrier can be shut down for a day or two for regular maintenance.

Army Corps officials said Friday they would continue DNA testing above the barrier and will consider poisoning options in the areas where DNA is detected.

Government officials also said they would consider changing the way they operate two busy navigational locks near the shoreline of Lake Michigan.

"All options are on the table," said Rogner.

Officials said research is already under way to try to manage carp populations in the Great Lakes, similar to the Great Lakes lamprey sterilization program that keeps numbers of that invasive parasite in check.

"We anticipate that someday this kind of operation may have to occur with carp," said Charles Wooley, deputy regional director for U.S. Fish and Wildlife Service.

Too weak to work?

Army Corps officials declined to speculate how the fish might have made it past the barrier.

One possible reason is that it wasn't operating at a level strong enough to repel all sizes of Asian carp until August, when the newly developed DNA tests first detected the fish within several miles of the barrier. Previous fish-shocking surveys had showed the carp stalled for several years about 20 miles below the barrier.

The Journal Sentinel reported a year ago that Army Corps officials planned to operate the barrier at one-quarter of its designed strength, due to the potential for electrical arcing and the resulting safety concerns for barge operators and boaters on the canal. They made that decision despite research that showed one-quarter strength, or one volt per inch, is not strong enough to repel all sizes of Asian carp.

The barrier was turned on in April at one volt per inch, and the Army Corps said it would consider bumping up the voltage if the fish were detected closer to the barrier.

The Journal Sentinel reported on Aug. 7 that DNA tests revealed the fish were indeed on the move. The Army Corps turned up the power on the barrier to two volts later that month after conducting several days of safety tests.

Agency officials said at the time that laboratory tests showed two volts, with the proper pulse frequency, is strong enough to repel all sizes of fish.

Conservationists Thursday said the only thing left to do now is to close the navigation locks to determine with certainty if the fish have indeed breached the barrier. And if they have, it's time to try to kill those fish.

"The important thing now is to make sure no fish get into Lake Michigan, and since we've got those structures in place that will help us do that, that is where we've got to focus," said Joel Brammeier of the Alliance for the Great Lakes.