Knowing Illinois government , they probably wrote that not even knowing pike , much less big , old pike are in the river...trusting our state government when it comes to our natural resources is a big gamble and one I personally don't take.
Eat whatever you like (but it would be much better for EVERYONE if there were a slot limit in my stretch , taking handles and leaving larger to live on...) but understand that the DesPlaines is a regularly flooded river, regularly....there is runoff from sewage, lawns and whatever people want to dump on their lawns , commercial properties , animal habitat, etc ., etc ., pouring in right now. There was flooding recently before these last rains. These last rains raising the levels 5' and there may be again before the 4 month rainy season is over here. It's an urban drain.
If there were coho and eyes in abundance and easily taken in there you could not pay me to eat them.