Fish Gas Bladder

Gas bladder (also called a swim bladder or fish maw) is a hydrostatic body of finfish that allows the fish to float freely at different depths. The fish can control the bladder and change its volume. If the fish reduces the bladder, it diminishes also the total volume of the body, the lifting force is reduced and the fish goes down. If the fish wants to move up to the surface, it increases the volume of the bladder and thus the buoyancy force acting on it.