Well, heres the way i see it. Trout are indeed a delicate species for the most part. In waters out west, there are thousands of miles of river, and about 20% of that is C&R Fly/Lure only ( some places single barbless only). Now, taking that into account along with an average of 3000-6000 fish per mile, you can see where proper handling and release plays a huge role in the overall productivity of a population.
I'm not gonna choose sides here, a fish is a fish in my oppinion, and a fisherman is a fisherman despite their choice of tools.
Back to proper handling/release. I know it sounds like preaching to some, and to others it is old-hat, but a reminder nonetheless.
!!! Fish are used to neutral bouyancy, and their bodies are not made to fully support their own weight out of water !!!!!
Number one - DO NOT hold a fish in the gills for any reason, ever, unlesss you plan to keep it!!
Number two - Keep the fish in the water at all times if possible. Ask yourself this - how long can you hold your breath after running for your life for a couple minutes ?? Same thing goes for the fish out of water. The buildup of lactic acid in the gills takes a few moments to clear its bloodstream, so placing the fish in the net in the water, or holding it in the water to recover till it swims off on its own is the way to go. And you'll be sure of doing far less damage.
Bass - Holding the fish by the lip vertically is ok for a quick grip-n-grin shot, but folding the fish over by the lip, thereby putting all the fishes weight in the lower jaw and soft tissue does a good deal of damage later after its release. The gill rakers and gills get compressed as well. You do run the risk of dislocating the jaw, tearing tendons, etc. The fish may swim away fine in our own eyes, but if that fish cannot properly use its mouth to feed - it won't last very long.
Treble Hooks - These pretty much guarantee inflicting as much damage to a fish as possible. I've noticed a trend toward using single hooks, which will still hook the fish and cause far less damage. I cannot remember the vendors or brands, but a look thru the shops will reveal a lot of options to swap out hooks on your hardbaits.
Trebles while bait fishing almost always results in gut hooking. Unless you plan on keeping every fish you catch, switch to single hooks or circle hooks.
Barbless Hooks - If you're just out for plain old fun, or don't plan to keep any fish, go barbless. Afterall, its the fight we love, and the chance to keep the fishery healthy.
Wet Hands - ALWAYS handle fish with wet hands. Dry hands, Dry Rags, Dry Gloves, all will take the slime coating off a fish. The slime is a barrier to ward off infections, without it the fish is prone to diseases.
Rubber Nets - Far better than nylon, and best of all, your hooks won't snag in them! Go with the smallest thickest mesh you can find. Smaller holes spread the fishes weight out more, and thicker material has less chance of snagging on scales, gill plates, etc.
Larger Fish ( Pike, Musky, Steelhead, Lake Run Browns, Salmon ) Same rules go as to handling and release. However one note of caution. I've seen many people "tail" fish in order to land them. By this i'm talking about grabbing the fish by the tail and carrying it that way, hanging the fish nose-down. The larger, heavier brown trout have whats called a knuckle at he tail along the spinal cord. Makes a great handle on a dead fish, but will "pop" on the larger ones,and can lead to a severed spinal cord, paralyzing the tail.
So, in the end, for any fish you plan to release, just cradle the fish with your palm under the belly and one hand under or gently holding the tail.
Again, i'm not preaching here, just adding my 2 cents. Some of us get lax time to time and don't think or remember these tips. Any fish you release has a chance to grow to its full potential, giving all of us the chance at better fishing in the coming years, and ensures our children a great place to fish.