Swimming techniques in osteichthyes and in chondrichthyes

Question

How swimming strategies are different in the osteichthyes and in chondrichthyes? Why sharks are required to agitate their body to swim whearas bony fishes do not?

Answer 1

Bony fishes have some specialized organ known as a gas bladder, or swim bladder, their interior is filled with the gas liberated from the gas glands. Swim bladder works as the hydrostatic organ as it varies relative density of body regulating the buoyancy and also depth of the animal in water while chondrichthyes don’t have swim bladders and therefore they should continuously agitate their body in order to keep swimming and manage their depth in the water. As an additional swimming aid, in chondrichthyes liver is big and oily; this trait helps in reducing the density of the body relative to water.