Spiny dogfish (Squalus acanthias)

Physical characteristics

Adults typically measure about 70–100 cm (28–39 in) and can weigh up to around 9.8 kg. Key features include a slender, elongated body, two dorsal fins each preceded by a stout spine, no anal fin, and a coloration that ranges from brownish-gray to mottled with lighter spots. The skin is rough to the touch. These traits help distinguish it from other small sharks.

Distribution and habitat

Spiny dogfish occur in both the North Atlantic and the North Pacific oceans. They occupy a wide depth range, from near the surface to depths reported over a thousand metres, and are commonly found in coastal shelf waters as well as offshore. They prefer temperate and cooler waters and often form large schools.

Diet and ecology

This species feeds primarily on a variety of smaller pelagic and demersal fish, including species such as herring and mackerel, as well as squid and crustaceans. Spiny dogfish are active predators and scavengers; their schooling behavior can concentrate feeding on abundant prey. They are preyed upon by larger sharks, marine mammals and historically by humans.

Life history and reproduction

Spiny dogfish have a slow life history compared with many bony fishes: they grow gradually, mature relatively late, and produce a modest number of well-developed young. Females are ovoviviparous, giving birth to live pups after a lengthy gestation period. These reproductive traits make populations slow to recover from heavy exploitation.

Human interactions and conservation

The species has been intensively fished for meat, liver oil and as a component of commercial groundfish catches; in some regions it was used historically as an inexpensive food source. Because of its slow reproduction and value to fisheries, spiny dogfish have experienced regional declines and are the subject of management and conservation measures in many jurisdictions. Sustainable harvest limits, monitoring and protective regulations aim to balance use with recovery where stocks have been depleted.

Notable facts

• Each dorsal spine can deliver a painful wound if the fish is handled carelessly.
• The species often forms mixed-sex schools and can migrate seasonally in response to temperature and prey availability.