The swim bladder is a type of fish organ, commonly known as a fish bladder.

The swim bladder is a specific gravity regulator that adapts the fish body to life in the water. It is located in the front of the body cavity, under the vertebrae, filled with air, and the esophagus is connected with a short section of the airway. In a few fish, the airway is degraded and the swim bladder is separated from the esophagus.

Role:

The swim bladder, which accounts for about 5% of the fish's body, is the regulator of the depth of the fish's position in the water when it swims, and it can regulate the specific gravity of the fish's body by inflating and deflating the air.

The most important function of the swim bladder is to regulate the specific gravity of the fish body by inflating and deflating, so as to regulate the balance of water pressure inside and outside the body of the bony fish and control the body sinking and floating. Some fish can also use their swim bladders to hear and breathe.

The gases that fill the swim bladder are mainly oxygen, ammonia and carbon dioxide, with oxygen being the most abundant. Therefore, in an oxygen-deficient environment, the swim bladder can be used as an auxiliary respiratory organ to provide oxygen to the fish.

Most of the bony fish that live in the upper and middle layers of seawater have swim bladders. Their shapes are ovoid, conical, heart-shaped, horseshoe-shaped and so on.