They're OK but not as flavorful as fresh fish. You do have the advantage of it being a summer-run in that it is still a few months from spawning thus, despite it's dark color, retaining some body fats that will add to the flavor. If it's a buck...all the better! Their meat stays much firmer than a ripe female.

To each his own but it is sometimes considered good taste to release dark, REALLY ripe fish as their table quality is poor at best and will not taste good baked, barbequed or smoked. If anyone tells you differently....they're lieing.