Pacific Spiny Dogfish Shark

• Maximum lengthAbout 1.3 m (4.3 ft), females; most adults 75–105 cm
• WeightUp to about 10 kg (22 lb); most adults 2–5 kg
• Lifespan80–100 years (spine-band ages of 80+ validated)
• Depth rangeSurface to about 1,240 m (4,050 ft); mostly 50–350 m
• DietHerring, sand lance, hake, pollock, krill, shrimp, squid, jellyfish
• IUCN statusLeast Concern (assessed 2016)

How to recognise a Pacific spiny dogfish

A spiny dogfish is a slim, grey shark about the length of your leg, and the first thing to check is the back: there is a stout, sharp spine standing in front of each of the two dorsal fins, the rear one longer than the front, and no anal fin at all. Those two features rule out almost every other inshore shark of the North Pacific; the tope, which shares the range, has an anal fin and no spines.

The snout is narrow and pointed, the eyes large and green-tinged, and the body slate grey to brownish above, shading to white below. Along the upper flanks runs a scattering of small white spots, bright in juveniles and often faded or gone in old adults. The teeth are the family trademark: small, with a single cusp bent sharply sideways so that the upper and lower rows interlock into a continuous cutting edge, about 28 in the upper jaw and 22 to 24 in the lower, which lets a dogfish saw pieces out of a fish too big to swallow.

Until 2010 this shark was lumped with the Atlantic spiny dogfish, Squalus acanthias, as a single worldwide species. A study led by David Ebert compared vertebral counts, fin proportions and mitochondrial DNA and resurrected the name Girard had given the Pacific fish in 1855, Squalus suckleyi, after the naturalist George Suckley who collected it in Puget Sound. In the field the ocean you are in settles the identity.

How big does the Pacific spiny dogfish get?

Females are the big ones. The largest reliably measured Pacific spiny dogfish are a little over 1.3 m (4.3 ft), and NOAA gives a maximum weight of about 10 kg (22 lb); FishBase quotes 1.4 m, which is at the edge of what the records support. Males are smaller, rarely passing 1 m. Most adults you will see in a trawl or on a line are 75 cm to 1.05 m and weigh 2 to 5 kg.

Pups are born at 22 to 30 cm (8.5 to 12 in), already carrying miniature spines, and growth after that is among the slowest measured in any fish: about 1.5 to 2 cm a year for an adult female. Males mature at 70 to 80 cm and females at 80 to 100 cm, a difference of a few centimetres that represents fifteen years of extra growing. The size bar below sets the 1.3 m maximum against a 1.8 m diver.

Where Pacific spiny dogfish live

The species belongs to the cool rim of the North Pacific. On the American side it ranges from the Bering Sea and the Aleutian Islands through the Gulf of Alaska and down the coast of British Columbia, Washington, Oregon and California to central Baja California; on the Asian side it occurs off Japan, Korea, the Sea of Okhotsk, Sakhalin and Kamchatka in Russia. The densest populations are in the sheltered inland seas of the north-east: Puget Sound, the Strait of Georgia and Hecate Strait.

It prefers water of roughly 7 to 15 °C, which is why it is scarce in the warm south of its range in summer and absent from the tropics. Vertically it is recorded from the surface to about 1,240 m (4,050 ft), but the bulk of the population lives over the continental shelf in 50 to 350 m, with juveniles higher in the water column and adults nearer the bottom. It tolerates brackish water but does not stay in estuaries.

Tagging in British Columbia since the 1940s has shown two kinds of movement. Most fish stay within a few hundred kilometres of where they were tagged, shifting inshore in summer and deeper in winter. A minority travel: dogfish tagged off Vancouver Island have been recaptured off Japan up to seven years later, a crossing of more than 7,000 km, and others have turned up off Mexico.

What Pacific spiny dogfish eat and how they hunt

Spiny dogfish eat whatever is abundant, which is the secret of their numbers. Stomach surveys from Alaska to California list Pacific herring, sand lance, capelin, smelt, hake and walleye pollock as the main fish prey, with juvenile salmon, cod, flatfish and rockfish taken when available. Invertebrates make up a large share by weight: euphausiid krill, shrimps, squid and octopus, crabs, and, unusually for a shark, jellyfish and comb jellies, which show up in a surprising number of stomachs. Small dogfish live mostly on krill; the switch to fish comes with size.

The hunting method is collective. Dogfish move in schools that can number in the thousands, usually sorted by size and sex, and a school working a herring shoal drives the fish into a ball and takes them from every side. A single dogfish cannot swallow a large herring, so it clamps on with the interlocking teeth, twists its body and cuts out a mouthful; a dozen dogfish do this at once and the herring is gone in seconds. Applied to a hooked salmon or a full gillnet, the same behaviour is why Pacific-coast fishers have cursed the species for a century.

Feeding peaks in spring and summer, when herring and sand lance are inshore, and slackens in winter as the schools move deeper.

Behaviour, spines and adaptations

The spines are the species' defining adaptation. Each is a hard, grooved spike of dentine, and the skin lining the groove secretes a mild venom. A dogfish that is grabbed arches its back and swings its tail around so that the second dorsal spine jabs whatever is holding it, and the spines also deter seals, larger sharks and lingcod, the animals that eat it.

Dogfish are among the most social of sharks. They spend their lives in schools, and the schools are structured: immature fish of both sexes together, adult males separately, adult females separately again, with the largest pregnant females often inshore in the shallowest water. The segregation is consistent and lasts for decades of an individual's life.

The senses are those of a shark that finds prey by scent and pressure rather than sight in dim water: a long snout packed with olfactory tissue, a lateral line sensitive enough to track a herring school in the dark, and ampullae of Lorenzini on the head. A low metabolism, an oil-rich liver and a slow cruising speed let a 3 kg shark travel thousands of kilometres and live for the better part of a century.

Reproduction and lifespan

Nothing about this shark happens quickly, and reproduction least of all. The Pacific spiny dogfish is ovoviviparous: fertilised eggs are enclosed in a thin membrane, or candle, inside the uterus, hatch there, and the embryos live on their yolk sacs until birth. Gestation lasts 18 to 24 months, one of the longest pregnancies of any vertebrate, and it runs longer in colder water. Litters range from 2 to 22 pups and average 6 to 9, larger females carrying more, and pups are born in winter at 22 to 30 cm. Because the female then rests for a year or more before ovulating again, she produces a litter only every two to three years.

Maturity is late even by shark standards. Males mature at 70 to 80 cm and a median age of about 19; females at 80 to 100 cm and a median age of about 35. Those ages come from counting bands on the second dorsal spine, whose enamel-like outer layer lays down a ring each year, and the method has been validated with tagged, chemically marked fish recaptured in British Columbia up to two decades later.

The same bands put the oldest Pacific spiny dogfish at more than 80 years, and estimates of 100 are defensible for the largest females, which places the species among the longest-lived sharks after the Greenland shark (see how long sharks live). A female removed at 40 has perhaps three litters behind her and thirty years of breeding ahead.

Is the Pacific spiny dogfish dangerous?

Not in the water. The SharkSider database contains no incident attributed to the Pacific spiny dogfish, and none is expected from a metre-long shark with a mouth built for herring that flees from divers. The few "dogfish" entries in the record all come from the Atlantic and Brazil and involve other species. Swimmers in Puget Sound share the water with millions of these sharks every summer, and the bite records for Canada and Alaska contain nothing to do with the species.

On a boat the calculation changes slightly. A hooked or netted dogfish thrashes and arches, and the venomous second dorsal spine can be driven into a hand, forearm or thigh. The venom is mild, but the puncture is deep, throbs for hours and can become infected. The safe grip is behind the head with the spines facing away, and the standard advice is to soak a spine wound in water as hot as can be tolerated, which breaks down the venom proteins, then clean it thoroughly. That is the full extent of the danger this shark poses to people (more on shark encounters).

The SharkSider database has no incident attributed to this species. The database draws on the International Shark Attack File, the Global Shark Attack File and verified local reports, and is updated weekly.

Conservation status and fisheries

The IUCN Red List assesses the Pacific spiny dogfish as Least Concern in an assessment dated 2016, reflecting a very large population, a huge range and stock assessments that show no decline in the core areas. NOAA Fisheries reports the Pacific coast stock as neither overfished nor subject to overfishing, and the Alaska stocks as not subject to overfishing, and in Canada the Committee on the Status of Endangered Wildlife rated the species of Special Concern in 2010 rather than Threatened.

That comfortable position was not always so. In the 1940s British Columbia and Washington ran one of the largest shark fisheries in history for dogfish livers, whose oil was the main commercial source of vitamin A, landing tens of thousands of tonnes a year until synthetic vitamins ended it in 1950. A second fishery followed from the 1970s for fillets sold in Britain as rock salmon and in Germany as Schillerlocken, and the British Columbia fishery became, in 2011, the first shark fishery in the world to win Marine Stewardship Council certification, later allowed to lapse as markets shrank. Today the species is mostly a bycatch of trawl, longline and salmon fisheries, and US commercial landings on the Pacific coast have shrunk to a few hundred tonnes a year.

The caution is biological. Any animal that matures at 35 and breeds every second or third year can be depleted fast and recovers over generations, as the Atlantic spiny dogfish showed when it was fished down in the 1990s. The species is not listed on CITES or CMS. It belongs on neither the endangered list nor the list of species anyone can fish carelessly, and mercury, which accumulates over a long life, makes large dogfish unsuitable for regular eating.

Similar species and close relatives

The obvious twin is the Atlantic spiny dogfish, Squalus acanthias, which looks identical, lives the same slow life and occupies the cool shelves of the North Atlantic, the Mediterranean, the Black Sea and the southern hemisphere; until 2010 the two shared a name. Within the North Pacific the genus is represented by a few smaller spurdogs off Japan, and in the wider family Squalidae by the barbelled mandarin dogfish of Japan and Australia and, in the Atlantic, the Cuban dogfish, a compact relative of the Caribbean slope.

The other dogfish of the North Pacific are more distant relatives in the same order, Squaliformes, and are all deep-water animals: the enormous Pacific sleeper shark, which shares the Gulf of Alaska and the Bering Sea but grows to 4 m and has no spines, the birdbeak dogfish of the continental slope with its long snout and big spines, and the black dogfish and other lanternshark-like species of the deep. Along the inshore coast the shark most often mistaken for a dogfish is the tope, or soupfin shark, which is larger, has an anal fin and no dorsal spines and is caught on the same lines. The dogfish lineage goes back well over 100 million years (see the evolution of sharks) and its body plan has barely changed.

• Cuban Dogfish Sharkspecies profile
• Mandarin Dogfish Sharkspecies profile
• Pacific Sleeper Sharkspecies profile
• Birdbeak Dogfish Sharkspecies profile
• Black Dogfishspecies profile
• Tope Sharkspecies profile

Written and reviewed by

SharkSider Editorial Team

A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.

Published August 31, 2022 · Last updated September 22, 2026 · No incident attributed to this species in the SharkSider attack database, which is updated weekly.