I figured, that is what I found after googling "Conneautte Harbor"
Unfortunately I can't be much help with answering your questions. Call the DNR, they will tell you what you want to know about the regulations and rules for hunting there.
As for whether or not there are any ducks to had in Conneautte Harbor, only one way to find out
What was big was not the trout, but the chance. - Aldo Leopold