The swim bladder, commonly known as the fish bubble contains air, which allows the fish to regulate the density of the body, rise or sink in the water.

Most of the bony fish that live in the upper and middle layers of the sea have swim bladders. The swim bladder occupies about 5 percent of the body's volume. Its shape is ovoid, conical, heart-shaped, horseshoe-shaped and so on. The swim bladder is filled with gases 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 for the fish.

The most important function of the swim bladder is to regulate the specific gravity of the fish's body by inflating and deflating, thus regulating the balance of water pressure inside and outside the body of the scleractinian and controlling the body sinking and floating. In this way, when they swim, they need very little strength to maintain a stable state in the water without sinking or floating. The pressure of seawater increases with the depth of the water, and increased pressure is an obstacle for fish that want to take a trip to the bottom. So when a fish wants to descend to a deeper layer of water, it will expel some of the gas from the swim bladder, so that the fish body increases as the specific gravity, and it will be much easier to dive. On the contrary, if it wants to rise to a higher layer of water, it has to fill up part of the gas, so that the swim bladder expands. At this point, the density of the fish body is less than that of the surrounding water, and the fish floats to the surface. The swim bladder makes it possible for bony fish to roam the ocean as they wish.

2. Why Fish Bladder is Nutritious:

The dried product of fresh and high quality swim bladder (commonly called fish bladder) is a traditional seafood, which is rich in viscous substance, so it is also known as fish glue and flower glue.

Because fish bladder is a viscous substance rich in protein, vitamins, minerals and other nutrients, fish bladder has the effect of tonifying the kidney, strengthening the waist and knees, nourishing the yin and essence as well as moisturizing and nourishing the skin. It is suitable for people who are weak, have a loss of real yin, are mentally overworked, or overworked in the house, as a tonic.