Sampling for invasive carp on the Chicago River critical in quest to keep fish from Great Lakes

It’s 6:30 in the morning, and the boat is already quietly cruising up the river. We’re in the middle of a canyon, its dark walls beginning to glisten in the cool light of dawn.
The canyon boasts sheer walls hundreds of feet high, but they aren’t made of rocks and soil. Instead, this canyon is made of steel, glass, and concrete, crossed by spans of bridges carrying cars and pedestrians on their morning commute.