Here's an article from the Colorado Trout Biologist about proper handling techniques. You can find the same principles promoted by most State Game & Fish Trout biologists and more highly regulated trout waters all over the US and the world for that matter. It's not Holier Than Thou attitude. It's about being good sportsmen and respecting the resources we all share and enjoy.
Trout should be handled and released in a way that affords them the best chance for survival No matter the species (brown, brook, rainbow, golden or cutthroat), the trout is one of the most fragile of all the freshwater fishes. A trout's needs and requirements for continued survival are some of the most demanding of any freshwater game fish and both it and its underwater habitat should be treated with respect. Like any other fish, trout possess a “slime” coating that protects them from acquiring disease and infection. Once the slime coating has been compromised, the trout is susceptible to invasion from a host of life-threatening illnesses and potentially deadly injuries. Here is a list of the top four immediate needs for optimum care of any trout:•Get the trout to hand as soon as possible. Overplaying a trout causes a potentially catastrophic build-up of lactic acid in the muscle tissues. Lactic acid accumulation prevents the fish from swimming normally, which makes it a target for predators. •Help protect the trout’s slime coating by not handling the fish at all, if possible. If handling is necessary for whatever reason, it should only be done after completely wetting your hands. Handling should be kept to an absolute minimum. Please, don’t grasp the trout with a towel. And never drag a fish up on the shore. This is particularly important in alkaline lakes where a heavy coating of slime is necessary to protect the fish.•Keeping a trout out of the water is like keeping a human under water; breathing is impossible. The less time a trout stays out of the water, the better its chances for post-release survival. Lactic acid increases as a fish is deprived of oxygen when it is taken out of the water. Extreme levels of lactic acid will cause paralysis. So limit the time that a fish is out of water to a maximum of 20 seconds or so.•Once the hook is removed from the trout’s lip, gently cradle the trout underwater facing upstream. Allow the trout a few moments to collect its’ thoughts, lose some lactic acid, and regain equilibrium. Once the trout has recovered, it will swim away from you faster than a car thief running from the cops.While those are the four most basic items to understand, there are other considerations and “helps” for a successful release.•If catch and release is the goal, pinching down the barbs on your hooks makes removal much easier. My personal experience is that if I keep a bend in the rod and tension on the fish, barbless hooks lose no more fish than barbed.•The slime coating is further protected by using the newer style, rubber nets now on the market. The older nylon nets are very hard on the fish. Next time you need to pick out a net, look for one that is made for C&R.•The use of forceps or hemostats is helpful in securing the hook and removing it without damaging the fish’s mouth.•If a fish is hooked deeply, the best idea is to simply snip the leader close to the mouth, rather than attempting to use a disgorger or pulling the hook free.•“Lipping” trout is very harmful, as the bones of their lips and mouth are fragile. They cannot be handled like a bass or with a Boga type tool. Holding a large trout vertically from the lower lip can damage the narrow isthmus area at the bottom of the gills. If you want to lift a fish for a picture, grasp the fish in front of the tail and under the belly to support the weight as evenly as possible.•The best way to weigh a fish is to lift it in a net. Weight the net with the fish and then subtract the weight of the net alone.•Avoid getting your fingers anywhere inside the gill plate. The least disturbance of the gills can kill a trout in a few hours, even though it looked fine swimming away from you.•Trout caught while fishing deep in lakes suffer from barotrauma (the bends) when brought to the surface. These fish must be released as soon as possible in order to improve survival. If the fish appears bloated and can’t swim back down by itself, it is best to use a descender weight with a clip or barbless hook to return the fish to depth quickly. Recent studies have found that deflating trout with a needle is a bad idea. Whether you release all the fish you land or selectively release fish to enhance your time on the water, these tips will allow for the best chance of survival for your trout. They are beautiful creatures and provide food and pleasure for us. Whenever we release them we should always do all we can to improve their survival.