There is also a natural mortality of fish. A released fish will generally survive if properly handled. On the other hand, improper handling results in high mortality. When we fly fish most of the fish are hooked in the mouth or lips.
Hooking is likely to prove fatal when the gills or vital organs are hooked.
Studies have also proven the old adage that a bleeding fish, regardless of where it is hooked, is a dead fish. We finally have enough studies which show that catch and release is a cost effective management tool, but it should be directed toward specific objectives. Since it becomes complicated to know the value of catch and release in a given stream, I have found a simple solution. You may also want to read Jesse Bohl's cautionary tale about a beginning flyfisher's experience with barbed hooks.