Another device that works well is called a hook-out and I believe it was originally developed for trout.
From everything I have witnessed if the fish is bleeding at all, I won't release it, but if you can unhook a deeply hooked fish without any hemorrhage the chances of survival are decent.
In Wisconsin our early trout season (starts the first of March every year) is mandatory artificial and barbless hooks. Implementing this rule into your pond greatly reduces hook related mortality.
