I have Fizzed several hundred fish over the past 10 years. About 5 years ago, I tested the fizzing in the side of a fish. I have never tried the fizzing in the mouth, looks like it would be better. I was wondering if the fish died weeks after doing the air bladder relief, so I caught some from 20 -30 foot in the winter on a spoon. I fizzed the fish and took them home and marked them and released them into a pond. I caught all 4 fish the following summer, 2 small mouth and 2 large mouth. Over the years, what I have learned is that small mouth can be caught from 35+ foot and do all right with fizzing. But large mouth, about 28 foot is the deepest I can keep the alive. I read a study that when a Large mouth come from deep water +25 that the air bladder can expand so much that it ruptures the organs coming up. I have had this happen on South Holston when drop shotting in 40 foot. Caught a 2 LB large mouth and it was dead when it got to the surface. I did bring it up fast, and it eyes looked like it was going to pop. So, if you do catch a fish deep, bring them up as slow as possible.
When does a fish need to be fizzed?
The best way to tell is 5 minutes after putting in live well, Is it on its side? Or worse up side down, for sure if it is up side down, it gills work with gravity and olny take 5-10 minutes to die. if they are on there side, I fizz them. Sometimes you have to fizz more than once. If you let too much air out the will lie on thier side on the bottom of the live well, never had one die from this.
When you insert the needle, you usally can hear the air blow out with a hiss. Check on your fish often.
Fish caught from 5 foot and stressed in the live well can also need to be fizzed as well sa deep fish.
They are easy to fizz, when one is in trouble rub its side and you will fill a hard spot above the side fin. As a general rule Large mouth, with the dorsal fin pointing toward the tail, count back 3 scales and up one. Small mouth back one and up 3. The needle needs to be long enough to go half way through the fish.
Just do a Google search Bladder Relief for Bass or fizzing.
I have fizzed Large mouth, small mouths and Spotted bass over the last 10 years and had 2 die, both large mouth.
A alterative is to clip some 1 oz weight to both front fins. Some of the additives, are helpful also.
Good luck and Good fishing and keep them Bass alive!