"Fish that have the potential to devastate the Great Lakes ecosystem may be just a few miles from Lake Michigan.
Two carp species from Asia — the silver and the bighead — are invasive fish with huge appetites. If they enter the Great Lakes, they could overwhelm the native fish.
To halt their migration, the U.S. Army Corps of Engineers built an underwater electric fence on a canal 20 miles south of Lake Michigan. Despite the barrier, tests now indicate that Asian carp have gotten close to the lake."