To understand why proper fish handling is important, a basic understanding of fish biology is helpful. Although saltwater finfish come in many shapes, sizes, and colors, they do have several things in common. Recreational anglers most frequently encounter two classes of fish.
Bony fish have a backbone and a skeleton made of bones.
Most of the familiar commercial species, such as cod, flounder, and bluefish, are bony fish. Cartilaginous fish, or Elasmobranch fish, have a skeleton made of cartilage instead of bones. This class includes sharks, dogfish, rays, and skates. The part of the fish usually used for food is the muscle. Other parts, such as roe, liver, and the fins of sharks, are sometimes eaten, but most fish is consumed as fillets or steaks.