From a farmers perspective the answer is easy. It's a business decision. The Chicago River is man made. It delivers water FROM Lake Michigan to the Mississippi. ANSWER! Poison it daily.heavy dose & daily. Like a deer drive. Squeeze & please. More chemicals. Kill all fish. Keep killing and move south slowly (fish move & follow current). 2 steps forward & one back till ya get to New Orleans. We can replace with hatchery fish what we want. My thoughts!