There are several reasons to practice catch and release.  Releasing a fish allows it to be caught again and be enjoyed by other anglers.  Also, fishing regulations often require fish of a certain size to be released.  Stress on fish increases when being caught, landed, and released and must be minimized in order to survive this process.

Stress is negative, whether you’re a person or a fish, and the higher the stress level, the longer it takes to recover.  When fish are caught, a number of factors contribute to how much stress they experience. Effects of stressors on fish add up quickly.  The more stress they experience, the lower the chance they will survive if released. 

Ways to Reduce Stress and Increase Fish Survival
Answers to Commonly Asked Questions
Rating Common Fishing Techniques for Impact on a Fish's Chance of Survival if Released

Answers to Commonly Asked Questions

Does letting gas out of the gas bladder with a needle, or “fizzing” a fish, improve a fish’s chances of surviving?

A fish that cannot remain upright in the water because it is severely stressed and/or has an over-inflated gas bladder stands a poor chance of surviving, if released.  “Fizzing” is a process where gas is released from the gas bladder of a fish by inserting a needle in its side and puncturing the gas bladder.  While this may help a fish regain it’s ability to return to the bottom of the lake, many fish that are “fizzed” die within a few days of release, from the stress of being caught and handled. There is also the likelihood that when you insert the needle into the side of a fish you will damage internal organs such as the kidney or intestines and should not be performed by untrained anglers.  Just because a fish swims towards the bottom doesn’t mean it will survive.

Should I reel in fish hooked in deep water quickly or slowly?

Quickly!  Contrary to popular belief, slowly reeling in a fish from deep water DOES NOT give a fish enough time to compensate for the change in pressure.  Between 20 and 30 minutes may be needed for a fish to compensate for pressure differences between a depth of 30 feet and the surface.  Prolonging the time it takes to land and release a fish, increases its stress level.  The tissues around the gas bladder are often capable of preventing the gas bladder from increasing in size for up to 5 minutes after the pressure outside of the fish decreases. Once a fish is in the boat, release it as quickly as possible to maximize its chance of surviving. 

What if a fish is bleeding when I bring it into the boat?  Will it survive if I release it?
The best you can do is to try to assess the extent of the damage to the fish.  If a gill was simply nicked by the hook, a fish might stand an excellent chance of surviving if released.  However, if the hook has been swallowed deeply or a gill arch has been ripped, you should keep the fish, if it is legal to do so.  Consider the effects of other sources of stress on a fish’s chance of surviving if released.

What if a fish swallowed the hook?  What should I do with the hook?
Many of the hooks used today are made of metals that do not rust.  If at all possible, with the use of a needle nose pliers or hemostat, remove the hook gently and quickly without damaging any tissues.  If the hook is not able to be seen or removed, cutting the line may be the only option and the hook may pass through the fish’s digestive tract.