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Somniosus microcephalus 

Scope: Europe
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Squaliformes Somniosidae

Scientific Name: Somniosus microcephalus (Bloch & Schneider, 1801)
Regional Assessments:
Common Name(s):
English Greenland Shark, Gurry Shark, Large Sleeper Shark, Sleeper, Sleeper Shark
French Laimargue Du Groenland
Spanish Tiburón Boreal, Tollo De Groenlandia
Synonym(s):
Squalus microcephalus Bloch & Schneider, 1801
Taxonomic Source(s): Eschmeyer, W.N. (ed.). 2015. Catalog of Fishes. Updated 6 April 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 6 April 2015).
Taxonomic Notes: Yano et al. (2004) confirm that sleeper sharks found in the South Atlantic Ocean and Southern Ocean are a separate species, Somniosus antarcticus Whitley, 1939.

Assessment Information [top]

Red List Category & Criteria: Near Threatened (Regional assessment) ver 3.1
Year Published: 2015
Date Assessed: 2014-10-14
Assessor(s): Burgess, G.H., Sherrill-Mix, S.A. & Kyne, P.M.
Reviewer(s): Hussey, N.E. & Allen, D.J.
Contributor(s): Dolgov, A., Walls, R.H.L. & Fordham, S.
Facilitator/Compiler(s): Dulvy, N.K., Lawson, J. & Walls, R.H.L.
Justification:
European regional assessment: Near Threatened (NT)

Somniosus microcephalus (Greenland Shark) is a large dogfish of the Arctic and North Atlantic oceans, inhabiting inshore zones to continental shelves and slopes usually at depths of zero to 1,200 m (one individual recorded at 2,200 m). Maximum size is uncertain but reaches at least 640 cm total length (TL), possibly 756 cm TL, with most adults between 288 and 504 cm TL. This appears to be an extremely long-lived and slow-growing elasmobranch with limited reproductive capacity.

Historically it was targeted for its liver oil in Norway, Iceland, Russia and Greenland with catches reaching 32,000 sharks per year in the 1910s in Greenland alone. These fisheries may have had a significant effect on the species, but the rate of historical decline (if any) is unknown. It is presently taken as bycatch in trawl, gillnet and trap fisheries, as well as in Arctic artisanal fisheries. Its population dynamics and biology are not well understood but its large size and slow growth rate suggest it is sensitive to exploitation.

No life history information on age at maturity or longevity are available. Time series data suggest a decline in landings from 1990-2012 (ICES 2013). Based on congener sleeper sharks (Centroselachus crepidater) generation length can be estimated to be at least 37.4 years, but is likely significantly longer given the larger size of S. microcephalus. A decline of 74% is estimated from 1990-2012 from ICES 2013 data. If declines continued at this rate, the species would likely be extinct by the year 2077 (within less than three generations). However, this information is based on landings data, which are not always an accurate measure of abundance, and it is unclear how effective management changes have been for reducing bycatch.

This shark is listed as Near Threatened in European waters on the basis of possible population declines that are likely to approach the threshold for listing under criterion A and limiting life history characteristics. There is a need to examine historical data and monitor current bycatch levels in the region.

Geographic Range [top]

Range Description:This species is restricted to northern Atlantic and Arctic regions. In the northeast Atlantic Ocean it is found in the waters surrounding the islands of Greenland, Iceland, and Spitzbergen. It is also found along the Arctic coasts of Russia (Bear Island, White Sea) and Norway, and further southwards to the North Sea and Ireland. It is not found in the Mediterranean Sea or the Eastern Central Atlantic. Reports of Greenland Shark (Somniosus microcephalus) from the Southern Hemisphere are most likely misidentifications of Southern Sleeper shark (S. antarcticus).
Countries occurrence:
Native:
Belgium; Denmark; Faroe Islands; France (France (mainland)); Germany; Guernsey; Iceland; Ireland; Isle of Man; Jersey; Netherlands; Norway; Russian Federation (European Russia, North European Russia, Northwest European Russia); Svalbard and Jan Mayen; United Kingdom (Great Britain, Northern Ireland)
FAO Marine Fishing Areas:
Native:
Arctic Sea; Atlantic – northeast
Additional data:
Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Lower depth limit (metres):2200
Range Map:60213-1

Population [top]

Population:No information is currently available on population size or structure. In the Northeast Atlantic, an inferred decrease in the subpopulation was reported in the Barents Sea over the last century (Rusyaev and Orlov 2013). Estimated landings from Icelandic fisheries in International Council for the Exploration of the Sea (ICES) Sub-areas Va (Iceland) and XIV (East Greenland) peaked at 91 tonnes in 1998 and have since declined, with as little as three tonnes reported in 2007 (ICES 2013).
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This shark is littoral and epibenthic, with habitat preferences ranging from river mouths and bays to continental shelf and slope waters. It is usually found at depths of zero to 1,200 m, but a maximum dive of 1,816 m was recorded by satellite telemetry for one individual (Campana et al. 2013) and another individual was observed at a depth of 2,200 m off North Carolina by a Remotely Operated Vehicle (Herdendorf and Berra 1995, Ebert and Compagno 2013). This species has been recorded in water temperatures of 0.6 to 17.2°C (Campana et al. 2013, Ebert and Compagno 2013). Although typically considered a deepwater species, local Inuit commonly report sightings of Greenland sharks in very shallow coastal waters, scavenging on harvested marine mammals.

Overall knowledge of movement and migration patterns remains limited. Satellite tracking of this species in the Northwest Atlantic showed medium-sized sharks moving northward and larger sized sharks moving southwards (Campana et al. 2013). However, in the Northeast Atlantic, individuals tagged off Svalbard showed no specific directional movements (Fisk et al. 2012). Short term tracking studies of Greenland Sharks under ice off Baffin Island during late Spring suggest that individuals remain at deeper depths during the morning and gradually move into shallower depths in the afternoon and at night (Skomal and Benz 2004), and vertical dive data suggest an oscillating diving behaviour interspersed with deep dives (Campana et al. 2013).

This species is live bearing with yolk sac, with one observed female carrying 10 young (Ebert and Compagno 2013). Size at birth is approximately 37−38 cm total length (TL) (Bjerkan and Koefoed 1957, Ebert and Compagno 2013). Size at maturity is > 400 and > 300 cm TL for females and males, respectively (Yano et al. 2007). This species reaches a maximum size of at least 640−756 cm TL, however most adults are between 288 and 504 cm TL (MacNeil et al. 2012, Ebert and Compagno 2013). The species is very slow growing with medium-sized sharks appearing to grow at a rate of one centimetre per year (Hansen 1963, Castro 1984, Castro et al. 1999). Juveniles are not commonly observed, but have been caught in deep waters in both coastal fjords and as bycatch in offshore waters. This suggests that juveniles reside in coastal and offshore nursery areas, or that these smaller individuals undertake large-scale movements between these areas (Hussey et al. 2014).
Systems:Marine
Generation Length (years):37.4
Movement patterns:Unknown

Use and Trade [top]

Use and Trade: An estimated 1,200 individuals or 140-150 tonnes are taken as bycatch annually in commercial Barents Sea bottom trawl fisheries (Rusyaev and Orlov 2013). In addition to commercial bycatch, it is also caught by artisanal fisheries in the Arctic (Young et al. 2010, Idrobo and Berkes 2012).

Threats [top]

Major Threat(s): In the northeast Atlantic Ocean, shark liver fisheries in the waters surrounding Norway, Russia, Iceland, and Greenland historically targeted this species, and may have had a significant effect on subpopulations. The Greenland fishery commenced in the early 19th century and in 1857 the estimated annual catch was 2,000-3,000 sharks. However in the 1910s this annual catch increased to 32,000 sharks (Jensen 1914). A target commercial trawl fishery for this species in the Barents Sea extracted 200-300 tonnes annually from 1930 to 1941 (Rusyaev and Orlov 2013). All commercial fishing of this species ceased when Greenland fisheries for liver oil stopped in 1960 (Castro et al. 1999). During the 1970s this shark was perceived as a problem for other fisheries in western Norway and the government subsidized a fishery in order to reduce the population (Castro et al. 1999).

Currently this shark is taken as bycatch in trawl, gillnet and fish trap fisheries. An estimated 1,200 individuals or 140-150 tonnes are taken as bycatch annually in commercial Barents Sea bottom trawl fisheries (Rusyaev and Orlov 2013). In addition to commercial bycatch, it is also caught by artisanal fisheries in the Arctic and is viewed as a nuisance species due to its entanglement in longlines and consequent damage to fishing gear (Young et al. 2010, Idrobo and Berkes 2012).

Conservation Actions [top]

Conservation Actions: Based on advice from ICES to end fishing for deepwater sharks, the European Union Fisheries Council established a total allowable catch (TAC) for this species in 2007 (CEC 2012). This TAC was gradually reduced and in 2010 it was set at zero. In 2011, the allowable bycatch was reduced from 10% to 3% of the 2009 TAC and in 2012 it was further reduced to zero (ICES 2013).

Citation: Burgess, G.H., Sherrill-Mix, S.A. & Kyne, P.M. 2015. Somniosus microcephalus. The IUCN Red List of Threatened Species 2015: e.T60213A48917268. . Downloaded on 19 November 2017.
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