Answer:
Explanation:
Most fish rise and sink using this method, but not all do. Some species don't need a swim bladder because they spend all their life skimming along the ocean floor. Other fish, such as rays and sharks, ascend and descend by propelling themselves forward.
Lol I never thought swim bladder actually exists.
Well fishes that have bones contain swim bladder , while cartilegenious fish do not contain swim bladder. It is basically an organ fillled with gas allowing fish to control their buoyancy, and thus to stay at their current water depth without having to waste energy in swimming. So only bony fish have swim bladder while cartilegenious fish do not.
