The presence of an air bladder (also called a swim bladder) in Pisces is very important because it helps fish maintain buoyancy. This gas-filled organ allows fish to control their depth in the water column without constantly swimming, which conserves energy. By adjusting the gas volume inside the air bladder, fish can rise or sink, enabling them to stay at a desired depth for feeding, avoiding predators, or resting. Additionally, the air bladder contributes to lateral stability, may assist in sound production and reception, and in some species, it can even supplement respiration. Without an air bladder, many fish would need to swim continuously to avoid sinking, which is energetically costly. Cartilaginous fish like sharks and rays do not have an air bladder and rely on other means such as dynamic lift or oil-filled livers for buoyancy. Overall, the air bladder is a crucial adaptation supporting swimming efficiency, survival, and ecological versatility in most bony fish.