The U.S. Army Corps of Engineers fired up a new electric fish barrier Thursday on a Chicago-area waterway linking the Great Lakes and Mississippi River watersheds, the latest bid to protect the lakes from an Asian carp onslaught that could harm native species.
The $19 million device is slightly upstream from two others on the Chicago Sanitary and Ship Canal, which could serve as a pathway to Lake Michigan for bighead and silver carp that have migrated northward on the Mississippi and its tributaries since the early 1970s. The underwater electrodes emit rapid pulses, creating a force field meant to repel fish or shock those that don’t turn back.
“We now have great flexibility and redundancy” in the barrier network, said Col. Vincent Quarles, commander of the corps’ Chicago district. “We want to deter the Asian carp threat. The barrier is a very good tool.”
The three barriers are within a 1,500-foot section of the canal about 25 miles south of Chicago. The first, then a demonstration project, went online in 2002. The second was activated in 2009.
Federal and state officials contend the barriers have performed well, preventing Asian carp from becoming established in Lake Michigan and spreading to the other lakes. Biologists say the voracious carp, which can reach 4 feet in length and weigh up to 100 pounds, could disrupt the food web by out-competing less aggressive fish for plankton, eventually threatening the lakes’ $7 billion fishing industry.
Skeptics question the barrier’s effectiveness. Scientists with the University of Notre Dame and The Nature Conservancy have reported detecting bighead and silver carp DNA in numerous locations above the barrier, though just one live Asian carp has been found there.
“There are still serious gaps in our knowledge about how well it’s working,” said Thom Cmar, an attorney with the Natural Resources Defense Council. “No one ever imagined these electric barriers would be a permanent solution. They’ve always been just a stopgap idea.”
Environmental groups have called for physically severing the century-old, man-made link between the Great Lakes and Mississippi drainage basins, a step also sought by Michigan and four other Great Lakes states in a pending federal lawsuit against the Army Corps of Engineers.
The corps has pledged to consider that option in a comprehensive study of ways to prevent species migrations between the two watersheds, but critics are unhappy that it isn’t scheduled for completion until 2015.
In a report last week, the corps acknowledged the 2 volts per inch of electricity coursing through the barriers might not be enough to turn back fish just a few inches long, although it appears sufficient for larger fish. Officials said they would continue studying whether the voltage could be increased without endangering barges moving flammable items across the canal. Results are expected this fall, Quarles said.
With the new barrier up and running, Quarles said the second would be taken down for maintenance within the next two months. Field studies will determine how many of the devices will be operated at any given time, he said.