161691-3

Raja brachyura 

Scope: Mediterranean
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Rajidae

Scientific Name: Raja brachyura LaFont, 1871
Regional Assessments:
Common Name(s):
English Blonde Skate, Blonde Ray
Synonym(s):
Raia brachyura LaFont, 1871
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: This species has been confused with Raja montagui and Raja polystigma in the Mediterranean Sea (Bertozzi et al. 2003).

Assessment Information [top]

Red List Category & Criteria: Near Threatened (Regional assessment) ver 3.1
Year Published: 2016
Date Assessed: 2016-03-25
Assessor(s): McCully, S., Serena, F., Morey, G & Ellis, J.R.
Reviewer(s): Walls, R.H.L. & Allen, D.J.
Contributor(s): Dulvy, N.K., Notarbartolo di Sciara, G., Bertozzi, M., Ungaro, N., Tinti, F. & Mancusi, C.
Facilitator/Compiler(s): Walls, R.H.L.
Justification:
Mediterranean regional assessment: Near Threatened (NT)

The Blonde Skate (Raja brachyura) is a relatively large-bodied skate, endemic to the Northeast Atlantic and western Mediterranean Sea. It occurs on soft substrates to depths of about 300 m in the Mediterranean Sea. It is apparently rare in the region, captured in only 21 of 6,336 tows in Mediterranean-wide trawl surveys conducted between 1994 and 1999 (at depths of 10–800 m). It is not certain whether the Blonde Skate has always been rare in the region; no data are currently available on historical abundance or trends for this region and there is no evidence to suggest it was ever common. Due to a lack of data, the similarity between fishing pressure in both regions and the lacking management in the Mediterranean Sea compared with the Northeast Atlantic can be used to infer that the population is likely doing the same, if not worse, in Mediterranean waters. Therefore, in the absence of data it is inferred from the Northeast Atlantic region that the Blonde Skate has declined similarly by almost 30% in Mediterranean waters as a result of overexploitation. The species is therefore assessed as Near Threatened, close to meeting the criteria for Vulnerable A2bd.

Geographic Range [top]

Range Description:Within the Mediterranean Sea, the Blonde Skate occurs off Spain, France, western Italy, Tunisia, Algeria, and Morocco (Bauchot 1987, Bertrand et al. 2000, Baino et al. 2001, Bertozzi et al. 2003). There is also one questionable record from the northern Aegean Sea (Serena 2005).
Countries occurrence:
Native:
Algeria; France (Corsica, France (mainland)); Gibraltar; Italy (Italy (mainland), Sardegna, Sicilia); Malta; Monaco; Morocco; Spain (Baleares, Spain (mainland), Spanish North African Territories); Tunisia
FAO Marine Fishing Areas:
Native:
Mediterranean and Black Sea
Additional data:
Lower depth limit (metres):300
Upper depth limit (metres):10
Range Map:161691-3

Population [top]

Population:This species was recorded in a total of 21 of 6,336 tows performed at depths of 10−800 m in the International Bottom Trawl Survey in the Mediterranean (MEDITS) between 1994 and 1999 (Baino et al. 2001). This survey covers the northern Mediterranean coast almost continuously from west Morocco and Spain to the Aegean Sea and Cyprus in the east. The species appears to be relatively rare in Italian waters, with a low frequency of occurrence in Italian scientific trawl surveys "Gruppo Nazionale Risorse Demersali" (GRUND), MEDITS, and other surveys in this area (Follesa et al. 2003, Ragonese et al. 2003, Spedicato et al.2003, Serena et al. 2005). The Blonde Skate does not appear to have been captured in either historical or recent comparative trawl surveys of the Adriatic Sea or the Gulf of Lions (Aldebert 1997, Jukic-Peladic et al. 2001). The Blonde Skate also appears to be uncommon off Tunisia (Bradaï 2000).

The Blonde Skate is relatively rare in the Mediterranean Sea, but it is unclear if this was always the case. Recent regional population trends cannot be estimated for this species given the lack of appropriate data from the region, although a long term decline is suspected (MiPAAF 2014). Instead, it can be inferred from the Atlantic region, where fishing pressure is similar but more regulated, that the species is declining similarly in the Mediterranean Sea due to comparable fishing pressure and habitat use. In the Northeast Atlantic the Blonde Skate is suspected to have declined by almost 30% over the past three generations (30 years), hence the same can be inferred for the Mediterranean regional assessment.
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:In the Mediterranean Sea this species is mainly found at depths of 10−150 m, to around 300 m (Baino et al. 2001), usually over sandy sediments.

Like other skates, this is an egg-laying species. It reproduces between February and August, and has a gestation period of almost seven months. Females produce ~30 egg cases per year (Stehmann and Bürkel 1984). In the English Channel waters off Jersey, sexual maturity is reached at a length of 82 and 93 cm total length (TL) in males and females, respectively (Ellis et al.  2011). Similarly, length at first maturity for females in Portuguese waters was reported as 92 cm TL (Figueiredo et al. 2007). Trawl survey catches from UK waters reported lengths at first maturity of 55 and 60 cm TL and length at 50% maturity of 78.2 and 85.6 cm TL for males and females, respectively (McCully et al. 2012). The largest immature specimens caught during this study were a 91 cm TL male and a 93 cm TL female. This species reaches a maximum size of approximately 120 cm TL (Stehmann and Bürkel 1984) and commonly reaches 40−80 cm TL. These data are likely to be very similar and therefore appropriate for inference to the Mediterranean region.

Age data are limited (Gallagher et al. 2005), with age at maturity and maximum age suspected to be approximately 5 and 15 years, respectively. This would indicate a 10 year generation length.
Systems:Marine
Generation Length (years):10
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: There is no information on the use or trade of this species in the Mediterranean region.

Threats [top]

Major Threat(s): The Blonde Skate is taken as bycatch of Mediterranean semi-industrial (Spain) and artisanal (Morocco and Greece) fisheries using bottom trawls, gill nets, and long lines (Bauchot 1987). Demersal trawl effort increased both numerically and in technological terms in the shelf and slope area of the Mediterranean Sea for a period of >50 years. For example, the Gulf of Lions area was historically exploited by small-scale trawl fisheries, comprising 27 small low powered boats (total nominal horsepower of 2,700 hp). Effort increased to a total nominal horsepower of 19,940 hp from 1974–87. The continental shelf and upper slope of the Mediterranean Sea are highly exploited, with intensive commercial trawling occurring at depths of 50−800 m (Colloca et al. 2003, Massutí and Moranta 2003).

Conservation Actions [top]

Conservation Actions: There are no species-specific management or conservation measures currently in place. In future, this species may benefit from generic management measures for demersal fisheries such as mesh size regulations or effort reduction. Research is required on population size and trends, range, biology, ecology, habitat status, and threats.

Citation: McCully, S., Serena, F., Morey, G & Ellis, J.R. 2016. Raja brachyura. The IUCN Red List of Threatened Species 2016: e.T161691A16527725. . Downloaded on 17 August 2018.
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