Asian Carp: An Electric Hope for the Great Lakes

Imported from China in the '70s, silver and bighead carp have now spread throughout the Mississippi River basin. An electric barrier has so far prevented them from entering the Great Lakes.

An Electric Hope for the Great Lakes by David Schaper
NPR.org, July 11, 2006 ·

The last, best hope for keeping voracious Asian carp out of the Great Lakes appears to be an electric barrier on the Chicago Sanitary and Ship Canal, which connects the Illinois River with the Chicago River and Lake Michigan.

Though fast-moving and fast-multiplying (some call carp the "rabbits of the water"), the fish apparently still haven’t advanced past the Brandon Road lock and dam near Joliet, some 50 miles from the mouth of the Chicago River and the entrance into Lake Michigan.

There is real concern that the invasive species could seriously alter the food web and the entire ecosystem of the Great Lakes if they ever get through.

"Asian carp [pose] one of the most serious threats to our way of life in the Great Lakes region in the next 100 years," says Cameron Davis, executive director of the Alliance for the Great Lakes, a non-profit advocacy and educational organization.

Biologists and ecologists say Asian carp consume massive amounts of phytoplankton and zooplankton -- as much as 40-percent of their body weight or more each day. That's the same food source relied upon by many native fish species and other aquatic life.

Competing with carp would put native species at a huge disadvantage. Asian carp can grow to 80 pounds, and they reproduce rapidly: Females can carry up to 2 million eggs.
"If carp get into Lake Michigan, it has the potential to completely undo the food web, much like a computer virus can wipe out a network," says Davis. “We’re like a computer system without an anti-virus."

At stake is a $4.5 billion-a-year fishing industry.

A temporary and experimental electric barrier was put in place four years ago on the canal near Romeoville, about 30 miles southwest of Chicago, in hopes of turning back the Asian carp. It consists of 13 cables across the bottom of the canal that send electric impulses at split-second intervals to startle and turn back fish.

In trial runs with common carp, the experimental barrier has appeared to work well. But it is beginning to corrode, and one of the 13 electrodes has failed. A new, bigger and more powerful electric barrier is being constructed; last month, Congress appropriated $10 million for its completion and operation.

The new, permanent barrier consists of 46 electrodes. It would create a much stronger electrified field, three times larger than the experimental one.

Still, the barrier won't be foolproof. Some observers fear the powerful wake left by big barges could pull fish through the barrier, or that Asian carp larvae could ride along like stowaways in ballast tanks and be discharged into the Great Lakes.

For more information:
National Public Radio
Upper Midwest Environmental Science Center
US Environmental Protection Agency

Illustration by Doug Beach for NPR