When water temperature exceeds 70 degrees, mortality of released fish, especially larger fish, goes up substantially. Fish brought up from more than 30 feet of water have greatly reduced chances of survival, although some hardier species of snapper and grouper survive when brought up from depths of 150 feet. A long fight on the line can upset a fish s chemical balance. Fish to be released should be brought to the boat quickly and while still fresh. Loss of Slime.
Fish have a slime coating which seals out infection.
Rough handling can damage this protective layer. Time out of the water. As long as a fish is out of the water, it cannot breathe or restore its chemical balance. Anglers should minimize the damage caused by hooks and by handling. Use strong enough tackle.