Any member of the vertebrate class Osteichthyes, including the great majority of living fishes and all the world's sport and commercial fishes.
Also called Pisces, the class excludes jawless fishes ( hagfishes and lampreys ) and cartilaginous fishes ( sharks , skates , and rays ). There are more than 20,000 species worldwide, all with a skeleton at least partly composed of true bone. Other features include, in most species, a swim bladder (an air-filled sac to give buoyancy), gill covers over the gill chamber, bony platelike scales, a skull with sutures, and external fertilization of eggs. Bony fishes occur in all freshwater and ocean environments.