I believe that prior to 2000 the Green River (King County) was restricted to bank fishing only. No fishing from a boat. Not sure if this was to help the run or for some other reason. Heres a thought and I am sure I am more guilty than the average fisherman. When I bank fish I have a tendancy to want to work a lot of water, especially during low water conditions. This can mean I will walk for miles and in the process cross the river multiple times no doubt damaging redds. I feel bad knowing this has probobly happened more than once. However a boat banging down a tail-out is doing the same thing.
Who's to say that it's a bad idea. Maybe restrict boating to normal and higher flows. Mandatory educational classes about ways to leave no impact. Before we start shooting down ideas lets get a bunch out in the open. There are a lot of smart people on this board and I am sure collectively we are a lot smarter then we sound.