Squalus acanthias (Linnaeus 1758), Spiny dogfish (Squalidae)

Author: Ronald Fricke, Germany

1. Description of the habitat/autecology of the species

The Spiny dogfish Squalus acanthias is a benthopelagic species that may enter brackish waters and may even straggle through freshwater habitats but would not survive there for more than a few hours. Squalus acanthias may be the (formerly) most abundant living shark. The species lives inshore and offshore, from shallow waters down to 1460 m depth, preferring temperatures of 7-15°C, in continental and insular shelf and upper slope habitats; it is usually found near the bottom, but may also ascend to midwater or may be found close to the surface. The species often occurs in enclosed bays or estuaries. This is a schooling species, with schools segregated by size and sex, but mixed schools occasionally occurring. It feeds mainly on bony fishes, but also molluscs, crustacea and other invertebrates. The species is growng slowly, and it takes more than 12 years to reach maturity at a total length of 60-70 cm (males) or 75-90 cm (females). Squalus acanthias is ovoviviparous, with a gestation period of 2 years and 1-13 young in a litter in Atlantic waters (Stenberg 2005). This species has two sharp dorsal spines that are believed to inflict toxins (Froese & Pauly, 2005). Maximum total length 160 cm (male) or 120 cm (female), maximum weight 9.1 kg, maximum individual age 75 years.

2. Distribution (past and present)

Distributed from the Kattegat to Kiel Bay, rarely to Bay of Mecklenburg. Outside HELCOM area, worldwide in tropical and temperate coastal and insular oceans except for the Indian Ocean and Red Sea.

3. Importance (sub-regional, Baltic-wide, global)

It’s historic importance in the fishery has made it a threathened species today. A small directed fishery is still carried out on Swedish west coast with landings of ca 200 tonnes a year. HELCOM (2007) defines the species as neither of local nor global importance.

4. Status of threat/decline

This species is threatened and its populations have been significantly declining throughout its distribution range in HELCOM area and in other European waters. In a HELCOM assessment, this species is classified as critically endangered (CR) according to IUCN criteria in the HELCOM area and as a HELCOM high priority species (HELCOM, 2007). It is suggested as critically endangered (CR) by George (2003; personal communication 2004) and listed as endangered (EN) in Sweden, and as threatened migrant (TM) in Germany.

5. Threat/decline factors

This species is threatened by fisheries (caught as by-catch in demersal fisheries, and also as a target species). It is rare, and highly sensitive to human activities, but not a keystone species.

6. Options for improvement

Squalus acanthias populations would benefit from a restrictive fisheries management, ICES recommends 0- catch.  and from a network of marine protected areas where fisheries is completely banned; such areas would serve for recovery of the populations. As a main threat for the species occurs outside HELCOM area in the neighbouring OSPAR area, and some populations in western HELCOM area depend on North Sea stocks, similar measures are recommended for the European Atlantic to restore population.

7. References

Froese R. & Pauly D. (eds) 2005. FishBase. Available in: www.fishbase.org, version (11/2005).

George M.R. 2003.  Die Ost- und Nordsee als Lebensraum für Haie, Rochen und Chimären. Meer und Museum, 17: 15-24. 

HELCOM 2007. HELCOM Red list of threatened and declining species of lampreys and fish of the Baltic Sea. Baltic Sea Environmental Proceedings, No. 109, 40 pp.  Available in: http://www.helcom.fi/stc/files/Publications/Proceedings/bsep109.pdf

ICES. 2006. Report of the Working Group on Elasmobranch Fishes (WGEF), 14–21 June

2006, ICES Headquarters. ICES CM 2006/ACFM:31. 291 pp.

Stenberg, C. 2005. Life History of the Piked Dogfish (Squalus acanthias L.) in Swedish Waters. J. Northw. Atl. Fish. Sci., 35: 155-164.