Who eats something that is found dead or nearly dead? That is some weird ish man.
There are other uses like sturgeon bait, or the body for garden fertilizer/dog food, and the roe for bait (yes, people justify harvesting a zombie chum for this reason all the time).
Under the wording of the regs quoted by WAfishboy I would think you cannot just wade into the slack water and grab your daily limit of dying or dead fish. At minimum you have to use some sort of hook and line (even a handline) and make some pretense of hooking it somewhere around the mouth**.
Another thing is that presumably you cant harvest a dead fish if it's currently closed for retention. ie. you could not grab a moldy sockeye floating by as sturgeon bait if that water was closed for sockeye at the time even though that carcass clearly has absolutely no value otherwise.
** A funny story on this topic. Last year on the Vedder a guy retains a chum. A while later he catches another beauty doe chum and bonks that one too (over the limit). Fishermen around start giving him a hard time, and one was apparently an off duty cop and goes up to Mr Poacher, asks for his license and gives him the business for a few minutes and makes him dump the extra chum into the river. Mr Poacher packs up and leaves but the extra chum eventually floats it way back to the rivers edge. One guy who watched the whole thing goes up to the chum, hooks it in the mouth and drags it the last two feet onto the bank and retains it.
We all kind of laughed at the absurdity of the whole incident and discussed it, and yes, if he had just gone up and grabbed it would have been against the regs, but making at least some effort of hooking it in the mouth first made it perfectly legit, if not a bit weird.