In December 2009, Illinois officials made a remarkable decision to protect the Great Lakes from an invasive fish threat: They treated roughly six miles of the Chicago Sanitary and Ship Canal with more than 1,800 gallons of rotenone, a chemical used to kill fish.
The operation was designed to stop Asian carp from using the canal as a gateway from the Mississippi River basin into the Great Lakes. What happened next was both dramatic and surprising. Hundreds of thousands of pounds of fish were recovered from the canal, yet crews found just one bighead carp.
