The only time I keep a bronze fish or dark fish if you will is when they are a hatchery fish. For the educated fisherman you can tell by strain, color of fish and time of year which will make out to eat and which will make out to smoke.
I too think it is unethical to keep a pre-spawning wild fish. It would make a lot more sense to let the fish spawn, then die and become nutrients for those that are hatching.
It's sad when you see the guys keep those dark, I mean dark fish that are starting to develop the white crust on them. I had one guy keep one next to me and I told him there was no use for the fish and it would help the ecosystem to return the fish to spawn and he looked at me and said "It'll make a good smoker" what a jacka$$..
My .02 worth
Keith