North Pacific Spiny Dogfish: Squalus suckleyi

Family: Squalidae

Common name(s)

Spiny Dogfish, , Piked Dogfish, Spurdog.

Identification

A slender squaloid shark with a long snout, fairly large eyes, and a narrow anterior nasal flap. Snout length greater than mouth width. Two dorsal fins with short anterior spines. Second dorsal fin smaller than first dorsal. First dorsal fin origin posterior to free rear tip of pectoral fin. Second dorsal origin posterior to pelvic fin free rear tip. Pectoral fins have mildly concave posterior margins and rounded free rear tips. Anal fin absent. Pectoral fins broad with rounded free rear tips.
Dorsal coloration grey or greyish-brown, usually with a few small, white spots along lateral line and upper back. Ventrum pale. Tip of first dorsal and upper caudal lobe often dusky or black. Posterior margins of pectoral fins and caudal fin often pale.

Size

Maximum length 130cm. Size at birth 22-33cm.

Habitat

A boreal to warm-temperate water species. Found in muddy or sandy bays, in channels of rocky reefs, and offshore along the continental and insular slopes. From the surface to 1,236m.

Distribution

The North Pacific spiny dogfish is found on both sides of the North Pacific Ocean. In North America it occurs from Baja, northwards to Alaska. In Asia it occurs from Eastern Russia, southward to Taiwan, including the Japanese archipelago.

Conservation Status

LEAST CONCERN

The North Pacific Spiny Dogfish (Squalus suckleyi) has been found to migrate extensively, even across the Pacific Ocean Basin, but there are relatively isolated stocks in Puget Sound (Washington, U.S.) and Strait of Georgia (British Columbia, Canada). Small target fisheries for this species are present in three different countries, as well as non-target catch and discards that are poorly known, underestimated, or completely unaccounted for. This species has life history characteristics that make it highly sensitive to over-exploitation including late maturity (~36 years for females), slow intrinsic growth rate (0.031–0.044 yr^-1), low reproductive capacity, and high longevity (80 or more years). The gestation period of 18–24 months is the longest known for vertebrates. This species segregates by both size and sex, making some members of its population (mature females) more accessible to fishing by trawl and bottom longline, which are the main fisheries that exist in its range. Some fisheries management exists in a limited portion of the range for the North Pacific Spiny Dogfish, but since this species is highly migratory, all countries and states must coordinate management of shared stocks for it to be effective. Multiple stocks have been identified but due to the absence of genetic differences among the stocks, they were assessed as one population.

In summary, the Northeast Pacific offshore stock is not overfished, and is possibly increasing based on the recent stock assessments. The Puget Sound inshore stock has historically been intensely fished but currently has relatively minor fisheries exploitation. The Strait of Georgia inshore stock has been categorized as being in a ‘cautious’ state, but currently, only around half of the recommended Total Allowable Catch (TAC) is used. North Pacific Spiny Dogfish in Alaska are stable or increasing. The status of the North Pacific Spiny Dogfish in the Northwest Pacific (Japan, Korea, Russia) is not as well known, but does not seem to be decreasing. In Japan, this species was historically fished and has remained at low levels, but the current fishing effort is low.

Considering that data indicate North Pacific Spiny Dogfish in different areas of the North Pacific Ocean basin have no genetic differences, that the fishing pressure in most of its range is minimal or negligible, and that the most recent available stock trends suggest that abundance is stable or increasing in the majority of its range, the North Pacific Spiny Dogfish is categorized as Least Concern. However, we caution that the status of this species should be monitored closely because: (i) population trends of some stocks (Northwest Pacific) are uncertain, (ii) it has a very long generation length (51 years), and (iii) there is international demand for fins.

Citations and References
Bigman, J.S., Ebert, D.A. & Goldman, K.J. 2016. Squalus suckleyi. The IUCN Red List of Threatened Species 2016: e.T195488A2382480. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T195488A2382480.en. Downloaded on 12 January 2021.

Reproduction

An aplacental viviparous species. Litter size 2-12. Gestation ranges between 18-24 months.

Diet

North Pacific spiny dogfish are opportunistic feeders that consume a wide variety of bony fishes and invertebrates, and occasionally other elasmobranchs.
This species is known to form very large, dense feeding aggregations. Anecdotal reports from divers in the 1980s, tell of dogfish schools that would block out the sun and bring visibility down to zero, as the mass of animals moved through the area.

Behavior

North Pacific spiny dogfish undergo extremely long migrations. One tagged individual traveled 6500km across the Pacific.

Reaction to divers

Somewhat shy and difficult to approach, but may make close passes if curious. North Pacific spiny dogfish are extremely bold in baited situations, even wrestling for fish directed from divers’ hands.

Diving logistics

During the summer and fall, it is not unusual to see North Pacific spiny dogfish on the rocky reefs around Vancouver Island. Historically, the best place to see them was at Quadra Island where a fish processing plant would pump waste into the bay. This practice has been banned so dogfish numbers have diminished but a remnant population can still be found in that area.