The role of the swim bladder in the fish is:

The gas filled in the swim bladder is mainly oxygen, ammonia and carbon dioxide, and the content of oxygen is the most. Therefore, in an oxygen-deficient environment, the swim bladder can be used as an auxiliary respiratory organ to provide oxygen to the fish.

The main use of the swim bladder is not for breathing. Fish rely on the swim bladder to regulate their specific gravity, and through the swim bladder, they can slowly rise or fall without movement, and most bony fish have a swim bladder to regulate their buoyancy.