Spiny Dogfish
Squalus acanthias

   The spiny dogfish is a small schooling shark that forms groups of hundreds or thousands of individuals of the same sex and size. This shark is gray or brownish on top and pale gray or white on its ventral side with irregular white spots on the top or sides of the body. The average length is between 75 and 105 cm (30 to 40 inches), however individuals have been known to grow to 130 cm (50 inches) weighing 9 kg (20lbs). The second dorsal fin is smaller than the first and both fins have spines at their origin. The caudal fin is asymmetrical with the upper lobe being larger. The smooth edged short and oblique teeth are similar in both the upper and lower jaw. The spiny dogfish has an estimated life span of 25 to 30 years.
    Tagging studies have determined that the spiny dogfish migrates great distances. Individuals tagged off of Newfoundland have been recovered in Iceland years later. There have also been records of transatlantic crossings. However the bulk of the population migrates seasonally along the northeastern coast of North America.

Diet

    The spiny dogfish is an opportunistic feeder eating whatever prey is abundant. In general their diet is comprised of small fishes such as capelin, cod, haddock, hake, herring, menhaden and ratfish. They also eat invertebrates such as krill, crabs, polychaete worms, jellyfish, ctenophores, amphipods, squid and octopus.

Reproduction

    Development in this shark is ovoviviparous. The gestation length is the longest known for sharks at an estimated 22 months. Young are born in the warmer waters off of North Carolina or New England during the winter months. The number of young born in a litter is dependant on the size of the female, larger females bearing more pups. However most litters are between 2 and 16 individuals that are approximately 20 to 30 cm (8 to 12 inches) in length. Sexual maturity in males is reached at a size of 80 to 100 cm (31 to 39 inches) at which time they are usually 11 years of age. Females reach sexual maturity at a later age, between 18 and 21 years at which time they are between 100 and 124 cm (39 to 49 inches) long.

Habitat

    The spiny dogfish is found in cold and warm temperate oceans at temperatures between 6 and 15 degrees Celsius. However on the Scotian Shelf this shark has been caught in water temperature between 3 and 11 degrees Celsius. The spiny dogfish is tolerant of a wide range of salinities and can be found in estuaries. It can be located in the water column from the surface to depths of 730 meters (2,400 feet).

Range

    This shark is present in all of the worlds temperate oceans It ranges throughout the coastal waters of the Atlantic and Pacific oceans. The spiny dogfish is a seasonal migrant into Canadian waters. In June these sharks appear off Nova Scotia, in the Bay of Fundy and off southwestern Newfoundland. By July they move into the Gulf of St. Lawrence and into waters off of southern Labrador and around the rest of Newfoundland. By late fall most of the spiny dogfish migrate out of Canadian waters and move south to waters off of North Carolina or New England.

Distinguishing Characteristics

• No anal fin
• Spines in front of each dorsal fin
• Irregular white spots present on sides and back of the body
• Strongly oblique teeth in both jaws, with single cusp
• No subterminal notch on caudal fin
• Pectoral fins with curved rear margins
• Narrow anterior nasal flap

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