Most of the articles I read said the side method had a better survival rate than mouth fizzing.
http://www.tpwmagazine.com/archive/2...1_bassfizzing/
Side fizzing doesn’t appear to hurt the bass, and it isn’t difficult to do. If a tournament-caught fish shows signs of barotrauma, “we recommend that the angler go ahead and side-fizz the fish, within the first hour if possible,” Myers says.
Fish that were mouth-fizzed fared worse than those that weren’t treated at all. Some bled excessively, and a significant number died. Researchers can’t say for sure why this happened, but Myers can make an educated guess. “When you use mouth fizzing, you’re piercing the business end of the air bladder. That’s where all the nerves and blood vessels are,” he says. “We don’t recommend that treatment.”