Fishing ( Catch and Release)

Effective catch and release fishing techniques avoid excessive fish fighting and handling times, avoid damage to fish skin, scale and slime layers by nets, dry hands and dry surfaces (that leave fish vulnerable to fungal skin infections), and avoid damage to throat ligaments and gills by poor handling techniques.
The use of barbless hooks is an important aspect of catch and release; barbless hooks reduce injury and handling time, increasing survival. Frequently, fish caught on barbless hooks can be released without being removed from the water, and the hook(s) effortlessly slipped out with a single flick of the pliers or leader. Barbless hooks can be purchased from several major manufacturers or can be created from a standard hook by crushing the barb(s) flat with needle-nosed pliers. Some anglers avoid barbless hooks because of the erroneous belief that too many fish will escape. Concentrating on keeping the line tight at all times while fighting fish, equipping lures that do not have them with split rings, and using recurved point or "Triple Grip" style hooks on lures, will keep catch rates with barbless hooks as high as those achieved with barbed hooks.
One study looking at brook trout found that barbless hooks did not result in statistically significantly lower mortality rates than barbed hooks when fish were hooked in the mouth, but did elevate mortalities if fish were hooked deeper. The study also suggested bait fishing does not have a significantly higher mortality when utilized in an active style, rather than a passive manner that allows the fish to swallow the bait.
To make a hook barbless, the barb is simply crushed flat with a pair of needle-nosed pliers, a trivial task. Medium grit sandpaper can be further used to ensure complete removal of the barb, but this is not necessary and is rarely done.
The effects of catch and release vary from species to species. A study of fish caught in shallow water on the Great Barrier Reef showed high survival rates (97%+) for released fish if handled correctly and particularly if caught on artificial baits such as lures. Fish caught on lures are usually hooked cleanly in the mouth, minimizing injury and aiding release. Other studies have shown somewhat lower survival rates for fish gut-hooked on bait if the line is cut and the fish is released without trying to remove the hook.

While a number of scientific studies have now found survival rates of shallow water fish caught-and-released on fly and lure have extremely high survival rates (95–97%) and modestly high survival rates on bait (70–90%, depending on species, bait, hook size, etc.) emerging research suggests catch and release does not work very well with fish caught when deep sea fishing. New research indicates that bait mortality is more closely related to technique than to the fact that one is fishing bait, and that bait mortality is much lower than once thought.
Most deep sea fish species suffer from the sudden pressure change when wound to the surface from great depths; these species cannot adjust their body's physiology quickly enough to follow the pressure change. The result is called "barotrauma". Fish with barotrauma will have their enormously swollen swim-bladder protruding from their mouth, bulging eyeballs, and often sustain other, more subtle but still very serious injuries. Upon release, fish with barotrauma will be unable to swim or dive due to the swollen swim-bladder. The common practice has been to deflate the swim bladder by pricking it with a thin sharp object before attempting to release the fish.
Emerging research indicates both barotrauma and the practice of deflating the swimbladder are both highly damaging to fish, and that survival rates of caught-and-released deep-sea fish is extremely low. However, barotrauma requires that fish be caught at least 30 – 50 feet below the surface. Many surface caught fish, such as billfish, and all fish caught from shore, do not meet this criterion and thus do not suffer barotrauma.