Spiny Dogfish (Squalus acanthias)

Spiny Dogfish (Squalus acanthias)

The spiny dogfish is the most prominent member of the Squalidae family of dogfish sharks. Some live in relatively shallow water close to shore; others inhabit great depths. They vary widely in length, and one of their chief anatomical characteristics is the lack of an anal fin.


The body of the spiny dogfish is elongate and slender. The head is pointed. The color is slate gray to brownish on top, sometimes with white spots, and fading to white below. It has spines at the beginning of both dorsal fins; these spines are mildly poisonous and provide a defense for the spiny dogfish.


Spiny dogfish are common at 2 to 3 feet in length; the maximum size is about 63 inches and 20 pounds. In California waters, a large fat female will be roughly 4 feet long and will weigh 15 pounds. In the north-western Atlantic, maximum ages reported for males and females are 35 and 40 years, respectively.

Life history

Spiny dogfish tend to school by size and, for large mature individuals, by sex. Females are larger than males and produce from 3 to 14 young at a time in alternate years. The species bears live young and has a gestation period of about 18 to 22 months. Spiny dogfish are long lived and nonmigratory; heavy commercial fishing pressure in a given area will rapidly lower populations of this slow-growing, low-reproductive species.

Food and feeding habits

The spiny dogfish is voracious and feeds on practically all smaller fish, including herring, sardines, anchovies, smelt, and even small spiny dogfish and crabs. They have been known to attack schools of herring and mackerel, as well as concentrations of haddock, cod, sand lance, and other species.

Other Names

dogfish, dog shark, grayfish, Pacific grayfish, Pacific dogfish, spinarola, California dogfish, blue dog, common spiny fish, spiny dogfish, picked fish, spiky dog, spotted spiny, spurdog, white-spotted dogfish, Victorian spotted dogfish; French: aiguillat; Italian: spinarolo; Japanese: aburatsunozame; Portuguese: galhudo; Russian: katran; Spanish: galludo.

Spiny Dogfish (Squalus acanthias)
Spiny Dogfish (Squalus acanthias)


Spiny dogfish occur in temperate and subtropical waters. In the western Atlantic, they range from Greenland to Argentina; in the eastern Pacific, they range from the Bering Sea to Chile.


This species is common in nearshore waters along some coasts and may be found in enclosed bays and estuaries; it generally inhabits deep waters and typically favors the bottom. In temperate waters during the spring and the fall, spiny dogfish can range into coastal waters, heading more northerly in the summer. In the winter, they are distributed primarily in deeper waters along the edge of the continental shelf.