Sampling for Asian carp to begin in Chicago area

While DNA samples suggest that destructive silver or bighead Asian carp have breached the barriers, no physical fish -- dead or alive -- has ever been found on the other side of them, said Chris McCloud, spokesman for the natural resources department.

Weather permitting, biologists will begin sampling in rivers and canals on Wednesday.

"We have got to find where these fish are at so we can hopefully validate the (DNA) evidence," McCloud said.

Crews will focus on areas where warm water from industrial operations enters the waterways. Fish tend to congregate near the warmer water in the winter as temperatures drop. Workers and fishermen will use commercial fishing nets and electrofishing to search over the next two to three weeks, officials said.

In December, wildlife officials discovered a single Asian carp in a canal leading to Lake Michigan, the nearest the species has come to the Great Lakes. Environmentalists fear that if the carp reach the lakes they could starve out native fish species and devastate a $7 billion-a-year fishing industry. Carp can grow to 4 feet in length and 100 pounds.