Description: A relatively common skate. Body subrhombic, with a short, buntly angled snout, with a pronounced tip. Solid tail about as long as the body, with two small dorsal fins at the rear. Upper surface always covered by rough dermal denticles, even in young specimens; large adults, especially females, may have additional large thorns. The underside is wholly prickly in large females, whereas in males and young only on the snout and along the disc margins. Colour and pattern extremely variable, often with spots, blotches, or marbled, but may equally be plain coloured. The tail is usually transversally striped with light and dark crossbars.
Global Distribution: Eastern Atlantic: from Iceland, Norway, North Sea and the western Baltic to Morocco and Namibia, including the Mediterranean and the Black Sea. Possibly also South Africa and part of the Indian Ocean. View Map
BIOLOGICAL FEATURES
Size: Size at hatching 10-13 cm (total length). Maximum length: male 105 cm (TL); female 139.0 cm (TL); common length 85.0 cm (TL); maximum published weight: 18.0 kg.
Age: 15 years
Weight length rel.: Azores (Rosa et al. 2006): a=0.0058, b=3.022, r2=0.930 (n=404).
Portugal, south coast (Borges et al. 2003): a=0.00135, b=3.357, r2=0.99 (n=13).
Portugal, west coast (Mendes et al. 2004): a=0.0025, b=3.231, r2=0.963 (n=63).
Spain, south-west coast (Torres et al. 2012): a=0.0021, b=3.273, r2=0.99 (n=86).
British Isles (McCully et al. 2012): Males: a=0.0046, b=3.082, r2=0.99. Females: a=0.0037, b=3.148, r2=0.99. FishBase: Bayesian estimated length-weight: a=0.00251 (0.00206 - 0.00306), b=3.24 (3.19 - 3.29).
Growth type: Positive allometric (Mendes et al. 2004; Torres et al. 2012).
von Bertallanfy growth parameters:
Reproduction: Oviparous. Large females can produce up to 150 egg cases per year, which they lay in the winter and spring. The embryos take 5 months to develop.
Maturity: 76.7 cm, range 48 - 87.5 cm. British Isles (McCully et al. 2012): 66.6 cm (males), 76.6 cm (females).
Behavioural ecology: Nocturnal species. Remains on or buried in the sand during the day, being more active around dusc and during the night. Young may tend to follow large objects, such as their mother. Detects weak electric fields generated by other organisms (prey detection and predator avoidance) and may also generate its own weak electric fields.
Population structure & migrations: Exhibits sex and size segregation and shows a clear annual migration cycle. Adults exhibit seasonal migrations in order to mate and deposit egg cases in shallow nursery areas. Young are non-migratory.
ECOLOGICAL FEATURES
Depth range: FishBase: 10 - 577 m. Most common between 100 - 300 m.
Habitat: Demersal. Inhabits shelf and upper slope waters. Tolerates low salinities. Found on mud, sand and gravel bottoms, rarely on rougher bottoms. Young inhabit inshore nursery grounds.
Feeding habits: Juveniles feed mostly on small crustaceans, whereas adults feed on a variety of fish and crustaceans.
Trophic level: FishBase: 3.8
FISHERIES
Commercial interest: Minor commercial species. Commercially it is not distinguished from other skates of the family Rajidae.
Conservation status: Global: Near threatened.
Northeast Atlantic: Near threatened.
Europe: Near threatened.
Nutritional information & food safety:
Proximate composition per 100 g:
energy value: 90.1 kcal (4.5% DRV)
protein: 20.02 g (40.0% DRV)
fat: 0.51 g (0.7% DRV)
of which saturates: 0.246 g (1.2% DRV)
omega-3 (EPA+DHA): 0.070 g (recommended: 0.250 - 2.0 g daily)
REFERENCES
Borges T.C., Olim S., Erzini K. (2003). Weight–length relationships for fish species discarded in commercial fisheries of the Algarve (southern Portugal). Journal of Applied Ichthyology, 19(6): 394-396.
Direcção Regional de Pescas, Madeira.
Ebert D.A., Stehmann M.F.W. (2013). Sharks, batoids, and chimaeras of the North Atlantic. FAO Species Catalogue for Fishery Purposes, No. 7. FAO, Rome, 523 pp.
FAO-WHO (2010). Fat and fatty acids in human nurition. Report of an expert consultation, 10-14 November 2008, Geneva. FAO Food and Nutrition Paper 91. Rome, Italy, 180 pp.
Gibson C., Valenti S.V., Fordham S.V., Fowler S.L. (2008). The Conservation of Northeast Atlantic Chondrichthyans: Repost of the IUCN Shark Specialist Group Northeast Atlantic Red List Workshop. IUCN Species Survival Commission Shark Specialist Groups, NatureBureau, Newbury, UK, 76 pp.
González J., Hernández C., Marrero P., Rapp E. (2000). Peces de Canarias: GuÃa Submarina (5th edition). Francisco Lemus Editor, Santa Cruz de Tenerife, Canarias, Spain, 235 pp.
IUCN (2014). The IUCN Red List of Threatened Species. Version 2014.1. www.iucnredlist.org
McCully S.R., Scott F., Ellis J.R. (2012). Lengths at maturity and conversion factors for skates (Rajidae) around the British Isles, with an analysis of data in the literature. ICES Journal of Marine Science, 69(10): 1812-1822.
Mendes B., Fonseca P., Campos A. (2004). Weight–length relationships for 46 fish species of the Portuguese west coast. Journal of Applied Ichthyology, 20(5): 355-361.
Nieto A., Ralph G.M., Comeros-Raynal M.T., Kemp J., GarcÃa Criado M., Allen D.J., Dulvy N.K., Walls R.H.L., Russell B., Pollard D., GarcÃa S., Craig M., Collette B.B., Pollom R., Biscoito M., Labbish Chao N., Abella A., Afonso P., Ãlvarez H., Carpenter K.E., Clò S., Cook R., Costa M.J., Delgado J., Dureuil M., Ellis J.R., Farrell E.D., Fernandes P., Florin A-B., Fordham S., Fowle, S., Gil de Sola L., Gil Herrera J., Goodpaster A., Harvey M., Heessen H., Herler J., Jung A., Karmovskaya E., Keskin C., Knudsen S.W., Kobyliansky S., KovaÄić M., Lawson J.M., Lorance P., McCully Phillips S., Munroe T., Nedreaas K., Nielsen J., Papaconstantinou C., Polidoro B., Pollock C.M., Rijnsdorp A.D., Sayer C., Scott J., Serena F., Smith-Vaniz W.F., Soldo A., Stump E., Williams J.T. (2015). Europen Red List of Marine Fishes. IUCN and European Union, Publications Office of the European Union, Luxembourg, 90 pp.
Rosa A., Menezes G., Melo O., Pinho M.R. (2006). Weight–length relationships of 33 demersal fish species from Azores archipelago. Fisheries Research, 80(2): 329-332.
Torres M.A., Ramos F., Sobrino I. (2012). Length–weight relationships of 76 fish species from the Gulf of Cadiz (SW Spain). Fisheries Research, 127: 171-175.
Turan H., Sönmez G., Kaya Y. (2007). Fatty acid profile and proximate composition of the thornback ray (Raja clavata, L. 1758) from the Sinop coast on the Black Sea. Journal of Fisheries Sciences, 1(2): 97-103.
