Fishing closures help every steelhead that goes uncaught. Aha, but there's the catch 8^). Closed rivers are fairly barren of angling traffic, as you might suppose. Unfortunately, such traffic is not completely absent. My observations on the Skagit, Sauk, and Stilly during the 80s gave me the feeling that the CNR fishery resulted in less active poaching. However, from the fish's point of view, you'd have to contrast that against the incidental mortality rate of the CNR fishery to evaluate the net benefit or liability. If the overall mortality was about the same either way, I'd have to side with the social justice of allocating the steelhead mortality to a lawful CNR fishery (from which society benefits significantly) rather than the narrow interest serving a few unlawful poachers.
Unfortunately, fish management issues like this aren't cleanly black and white. No fish every benefited by being caught by an angler. Of course, that fish benefits significantly less if it's killed and removed from the population. The high moral ground of CNR fishing is a peculiar one - ranging from inconveniencing, traumatizing, or incidentally killing the fish, in the compromise interest of conserving fish populations while simultaneously extracting a social and economic benefit from the fishery resource.
It ain't pretty, but it's real.
Sincerely,
Salmo g.