Access is not being able to just get to the stream, it is getting to all of it. Just because bridges cross every mile or so doesn't mean you can get to the creek. Mounds of carcasses are not exactly a good way to get nutrients in.

Wild fish are just as prone to move bugs around. One of the reasons why there is a an effort to keep any and all anadromous fish out of hatchery water supplies is to keep bugs out.

We should be increasing wild escapement by leaps and bounds. That would be the simplest solution to getting nutrients into the system.

And wild fish are in now way free. One must protect the habitat which means reduce/eliminate water withdrawals, stream side logging, stream side ag, and so on. Plus, a hatchery is simply more efficient at converting water to fish. The complex of hatcheries in Hood Canal produces way more chum salmon for about 100 or 200 cfs. It produced more chum than any of the major river systems. While part of that was poor escapement goals there is the efficiency piece.