In recent years, there has been an increasing trend in the release of angled game fish by the recreational fishing sector. Many sport body impose the catch and release policy to protect the depleting stock of game fish. Angler throughout the world are finding the idea of catch and release fascinating enough to follow the trend and it has become common thing to see an angler shooting the fish (off course by a camera) rather than killing the fish after a great fight.
While some of this is due to the imposition of management measures such as minimum sizes and bag limits designed to reduce mortality on immature fish, there have also been an marked changing attitudes among sport anglers and sport body. Tagging program have contributed greatly to the education of fishermen relative to fish conservation and the importance of biological study. The angler that tags and releases fish now feels a sense of contributing to causes that will enhance the fishery. Discussions about numbers of fish tagged have slowly replaced those about numbers of fish killed among the sport fishing community.
In general, fish react to the acute stress of capture, severe exercise, and handling with more exaggerated disruptions to their physiology than those seen in higher vertebrates. Nearly all species of fish have a substantial proportion of their myotomal muscle mass (80%-95%) as anaerobic white swimming muscle which reflects an ability for high work output in short bursts. Angling practices cause increased anaerobic activity, muscular fatigue, and time out of water, resulting in marked respiratory and metabolic changes. Since fish blood comprises only 3%-6% of the body weight and white muscle over 30%, changes in muscle biochemistry will be reflected strongly by the composition of the blood Therefore, the changes in various hematological parameters relative to the degree of physical exhaustion can directly affect the general health of released fish.
But can the fish survive after it is released. Little is known of the mortality associated with the release of game fish. Evidence from different studies conducted using tag and recapture method are misleading and inconclusive as the low recapture rates of tagged fishes can be attributed to tag shedding, emigration, stock size, natural mortality, and reporting failure. still the mortality associated with angling stress cannot be discounted. Studies conducted on offshore fishes released after a fight by following the fishes using ultrasonic devices for eight hour minimum shows that all fishes survive completely the psychological effects due to stress related of fight.
As of my personal experience, only one fish was found dead after the release. It was handled very badly as it fell down while taking a photograph. That is why It becomes imperative to follow the laid down procedures while handling the fish and releasing it. If you want to release a fish follow the laid down procedures and release it immediately after revival. The maximum mortality happens only due to ignorant handling like tying the fish through the gills, keeping the fish out of water for long time while taking photographs and removing the slime accumulation over the fish body again by ignorant handling. Though not an expert on this subject, it is my belief that if properly handled, almost all fishes will survive after release.