A dogfish is a type of small shark that lives in oceans around the world. Despite its name, it has nothing to do with dogs: sailors gave it this name centuries ago, possibly because some species hunt in packs like wild dogs, or because they're so common that they seemed as ordinary as dogs.

The spiny dogfish, one of the most common species, grows only about three feet long and has a sharp spine in front of each dorsal fin for protection. Unlike the fearsome sharks you see in movies, dogfish are relatively harmless to humans and mostly eat small fish, squid, and crustaceans near the ocean floor.

Scientists often use dogfish in marine biology classes because they're abundant and their anatomy is similar to other sharks, making them useful for studying how sharks' bodies work. When you see a preserved shark in a science classroom, it's usually a dogfish.

Dogfish populations have declined in some areas because they're caught accidentally by fishing boats or intentionally for their meat, which is used in fish and chips in some countries. Some fishing communities also consider them a nuisance because they sometimes eat fish caught in nets before fishermen can haul them in.