I agree WW. In my view, in a situation like this, the water should be opened to trout/char. But, I would add some definitions to "fishing for" to cover situations like this in order to prevent a trout "fisherman" from playing with salmon. Here's some ideas:

Open to trout, closed to salmon/steelhead. Maximum hook size of 10, maximum weight added of half ounce.

Open to salmon, closed to trout. Minimum hook size of 6.

The same is needed for spiny ray fisheries in situations like Lake WA where you want to protect adult and smolt salmon. Might only be shore based or boat must be within 10' of shore.

I know WDG/W defined whitefish gear to allow fishing for whitefish when the rest of the river needed protection so the concept was not foreign, in the past. Also, this won't be perfect in that some legitimate angling methods might be prevented but it should allow for reasonable fisheries.