Scientists have been testing the water in the channels and rivers above an electric barrier desiged to keep Asian carp out of the Great Lakes.
They've found DNA evidence of the carp in Lake Calumet in the past. Now they've found more.
From the Associated Press:
Scientists have turned up more genetic evidence of Asian carp above an electric barrier designed to keep them from invading the Great Lakes.
The U.S. Army Corps of Engineers this week reported that nine water samples taken in May and June from Chicago-area waterways contained DNA from silver carp, one of two Asian species threatening to enter the lakes after migrating northward in the Mississippi River and its tributaries.
Hundreds of other samples had no carp DNA. But environmentalists say the latest findings show the electric barrier isn't enough to protect the Great Lakes. They want to sever the link between the lakes and the Mississippi basin near Chicago.
The federal government's Asian carp program coordinator said Thursday there's no evidence the fish are getting through the barrier.
DNA evidence can be a sign that Asian carp are in the water, but not necessarily so. It could just be that Asian carp scales or mucus are in suspension in the water column in that area.
Though one researcher with the U.S. Geological Survey says you're much more likely to find the DNA evidence before you find any fish:
"These fish are remarkably cryptic. They are very sensitive to nets and boats. They are not caught by accident by guys with rods and reels."
By the time Asian carp make themselves known, they tend to be breeding and well-established, he said.
"It's typical for a species to putter along at a barely noticeable level for several generations... but when you get the density high enough, you are definitely going to start noticing them."