Being able to use a resource but in a limited fashion seems to be the overall theme here. Flyfishing obviously has its disadvantages from an efficiency standpoint by not being able to reach water or cover depths that conventional tackle can.(insert spey argument here)
Limiting boats and the ablity to fish out of them is another limiting factor, along with a tag system. I guess what I don't understand is; to limit the user of a resource you have to know what their impact is.

Knowing what % encounter rate a wild steelhead faced would go along ways to managing the use of the resource. I've fished long enough to know there are three types of steelhead; 1) Kamakazee - Hit almost anything
2) selective to size, color, scent, action, etc... 3) won't bite anything

So, out of a run of 4,500 steelhead...How many will encounter an angler and when they do you take into account hooking mortality, etc...