Fishing is a popular pastime. Many people enjoy fishing so much they catch more fish than they can keep, so they practice something called “Catch and Release”. In theory this is suppose to be cruelty free, the fish swim away and live happy lives. In reality, while the fish may swim away, many do not survive long, and catch and release fishing is not as cruelty free as people think.
When fish are hooked they panic, they fight to get away. This uses a lot of energy. The energy they exert when trying to get away causes lactic acid to build up in the fish and reduces its oxygen levels. It should go without saying that an exhausted fish is not going to just swim away and continue as though nothing happened, it has lost its school (not all fish swim in schools but some do), it is frightened, and it is tired.
Fish do feel pain when hooked, and some hooks are swallowed by the fish, not just hooked onto the side of the mouth. Removing these swallowed hooks is very difficult and nearly always damages the fish, in some cases its insides are tore by the fisherman reaching into it for the hook, and by the hook being dragged back up its throat.
At one time fishermen use to try to justify the pain by saying that fish didn't feel pain, but studies have shown this is not the truth, fish do feel pain. A study in Edinburgh's Roslin Institute, and published by the Royal Society, showed that rainbow trout do feel pain much like any of the higher mammals.
Additionally the stress of being out of the water can cause the fish's gills to collapse. It does take a while for the fish to “suffocate” from being out of the water, but there is still damage done in the mean time.
Even the handling of the fish puts it at risk. Fish are covered with a “slime coat” when handled this slime coat is damaged and when the fish is put back into the water it is more at risk for bacterial, or fungal, infections.
Fish caught and released often stop eating, perhaps due to pain, or trauma.
Two studies were done on fish caught and released at fishing tournaments. One study was done in Oklahoma, by the Oklahoma Department of Wildlife Conservation. They found that 43% of caught and released fish died within 6 days. Another study, by Texas Tech University, found 62% of caught and released fish died within 6 days. In both studies a control group of fish was also observed and none died in either case.
All in all it would be a foolish idea to assume that fish caught and released swim off as though nothing happened.