How Many Bones Do Fish Have?
Fish come in a variety of species, sizes and anatomical structures, which means there is no average or typical amount of bones for fish. While some fish have a bony skeletal structure, others have a skeleton consisting of cartilage instead of bone.
"Cartilage-fish" are classified as chondrichthyes and include rays and sharks. These fish are descended from bony fish, but have evolved a cartilage-centric skeleton.
The lamprey and hagfish have no bony skeleton or jaw and feed through sucker-like mouths. The hagfish is highly flexible and is virtually able to tie its body in a knot; it does this to remove the slime its body produces to ward off predators.