dogfish, name for a number of small sharks of several different families. Best known are the spiny dogfishes (family Squalidae) and the smooth dogfishes (family Triakidae). Spiny dogfishes have two spines, one in front of each dorsal fin, and lack an anal fin. The common spiny, or piked, dogfish ( Squalus acanthus ) is found in most oceans of the world and is particularly abundant in shallow, temperate waters. Its gray skin is speckled with white. Females of this species may reach a length of 4 ft (120 cm) and weigh 15 to 20 lb (6.3–9 kg); males are smaller. The spines in this species contain venom that can cause a very painful wound. Spiny dogfishes migrate seasonally, preferring water within a certain temperature range. They feed on a variety of fishes and invertebrates and cause great damage to populations of commercially valuable fish. In Europe they are fished for food. Other members of the spiny dogfish family are found in deep water. The smooth dogfish ( Mustelis canis ) is found on the Atlantic coast of America from Brazil to Cape Cod. It is gray in color and grows to a length of about 5 ft (150 cm). Of no commercial value, it migrates seasonally and feeds on small fishes and invertebrates. Like the spiny dogfish, the smooth dogfish is much used for dissection by students of vertebrate anatomy. The smooth dogfish family also includes two small sharks abundant on the Pacific coast of the United States, the brown smoothhound ( Rhinotriacis henlei  ) and the leopard shark ( Triakis semifasciata ); the latter is strikingly marked with black on a tan background. The name dogfish also refers to certain unrelated bony fishes (see bowfin). The dogfish sharks are classified in the phylum Chordata, subphylum Vertebrata, class Chondrichthyes, order Selachii.