G-man,
A steelhead hooked in the gills has a high chance of dying, but don't assume they all do. Some fish that are hooked in the gills and bleeding like a stuck pig when released do survive. As part of a study years ago, a steelhead hooked on a barbed treble on the Snake River was bleeding when boated, tagged, and released. That fish showed up at the hatchery many weeks later, ready to spawn. As others have indicated, bonking a fish results in zero % survival. The release of fish in poor condition results in a higher % survival, but much less than 100%. Since a released fish has some chance of survival, even if as little as 1%, there is no wastage of gamefish violation.
Silver Hilton,
As for netting and beaching, neither does the fish any favors. I'm referring specifically to the most common nets I see in boats on the rivers. These are made of knotted polypropolene webbing. They cut through the slime layer and then scrap a lot of scales off. The scale loss leaves the fish's skin open to infection, which will increase the mortality rate by some amount. I don't know how much. The knottless nylon or polyester webbing nets are very much gentler on fish, and I do wish they were more readily available to anglers, as they do facilitate a more rapid handling and release of fish.
Sincerely,
Salmo g.