Dogfish, the name given to several kinds of small sharks because they hunt in groups, like packs of dogs. Dogfish are found in waters near the shore. The spiny dogfish, or grayfish, is caught for its vitamin-rich liver oils; it has a sharp spine in front of each back, or dorsal, fin. Two species of smooth, or spineless, dogfish live in North American coastal waters. The Atlantic smooth dogfish is five feet (1.5 m) long; the Pacific smooth dogfish, about half that length. Most dogfish are pests to commercial fishermen because their raiding packs scatter smaller fish sought by fishermen and often foul nets.

The spiny dogfish, Squalus acanthias, is of the family Squalidae. The Atlantic smooth dogfish is Mustelus canis; the Pacific smooth dogfish, M. californicus, both of the family Galidae.