Non-lethal would be stringing fishing line from stakes in areas that it likes to frequent.
While they don't eat as many fish as cormorants (water turkeys) they really can do some damage to spawning fish in shallow water, and any larger fish that swim by.
I don't know if Wi. requires you to have a permit to permanently remove them like Indiana does.
I heard that they are allergic to lead when delivered at high velocities.