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Spiny Dogfish
Photo: Tone Vollen
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Spiny Dogfish

Spiny Dogfish has a worldwide distribution and is known to be one of the most abundant sharks. This species is subdivided into several populations, and the Northeast Atlantic stock extends from the Bay of Biscay to the Barents Sea. Tagging studies during the late 1950s showed seasonal movements of this stock from summers off the coast of Scotland to winters in Norwegian waters. 

Similar tagging studies in the 70s showed a distribution extending from the southern North Sea during summer to waters off Scotland during winter. In recent years, their distribution appears again as more northerly, but new tagging studies are needed to confirm this.  It is probable that changes in occurrence of this species in Norwegian waters reflect combined effects of changes in both migration patterns and population size.

Dogfish form large schools, and once individuals are encountered large quantities may be captured. Males and females often form their own schools, as do large and small fish. Females give birth to a small number (7-11) of live offspring after a two-year gestation period.  Capturing large schools with many pregnant females has a significant effect on future recruitment levels. Therefore, the spiny dogfish, like many other species of shark, are considered particularly vulnerable to overexploitation. Nevertheless, spiny dogfish in other areas appear to be able to rebuild after substantial over-fishing.

Facts about Spiny Dogfish

Latin name: Squalus acanthias
Family: Squalidae
Maximum size: 123 cm
Life span: 25 years
Distribution: Global distribution in temperate regions of both northern and southern hemispheres
Primary spawning area: Undetermined
Spawning season: Free-living offspring are born year round, but production is believed to be lower during winter.
Diet: Largely zooplankton, including gelatinous plankton during juvenile pelagic stages.  Adults feed on juvenile fish including cod, herring, squid, shellfish, and others.
Characteristics: Has a moderately poisonous spike at the tip of both dorsal fins. These can be used to estimate the fish's age by counting the number of enamel rings which have been laid each year.

Status and Fisheries Advice

The northeast Atlantic stock of spiny dogfish has provided the basis for a valuable fishery for more than a hundred years. Throughout the 40-year period from 1950-1990, it is reported to have supported annual landings of 30,000-60,000 tons.  

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