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 Thorny skate (Raja radiata )…  Can be identified by the row of thorns.  2 or 3 large thorns on each shoulder.  The bases of the thorns on the pectorals.

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Presentation on theme: " Thorny skate (Raja radiata )…  Can be identified by the row of thorns.  2 or 3 large thorns on each shoulder.  The bases of the thorns on the pectorals."— Presentation transcript:

1  Thorny skate (Raja radiata )…  Can be identified by the row of thorns.  2 or 3 large thorns on each shoulder.  The bases of the thorns on the pectorals are star-shaped, a very distinctive character.  Adult males have 2 rows of hooked, erectile thorns near the outer corners of the pectorals.  The snout is blunt.  There are 36 to 46 series of teeth in each jaw.

2  Brown on the dorsal side,either uniform or slightly clouded.  Sometimes there is a white spot beside each eye, and another on each side on the rear part of the disc.  The ventral side is white, may have slight brown blotches.  The thorny skate is about 4 inches (100 mm.) long from snout to first dorsal fin at hatching, may grow up to 100cm in length(40 inches).

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4  Is widely distributed throughout the North Atlantic region from Hudson Bay to South Carolina  Also occurs in areas such as: USA, Greenland, Iceland, Spitzbergen in the north, and from Norway to the southern North sea.

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6 1) Sampling:  Thorny skates is captured using an otter trawl.  Skates are kept alive on board the vessel  Total length was measured as a straight line distance from the tip of the rostrum to the end of the tail, and disc width as a straight line distance between the tips of the widest portion of pectoral fins.  Total wet weight (kg) was also recorded.

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8  Vertebral samples is taken from above the abdominal cavity, labelled and stored frozen.  After having been thawed, three centra from each specimen is removed from the vertebral column, stripped of excess tissue and air dried.  Large centra is cut sagittally using a mini-saw attachment.  Processed vertebrae is mounted horizontally on glass microscope slides and ground on both sides with successively finer-grit wet-dry sandpaper to produce a thin hourglass section.  Vertebral sections is digitally photographed.  The age can now be determined.

9 1. Bigelow and Schroeder. Thorny Skate[ internet].Thorny Skate(Raja radiata) Donovan 1807[28 July 2009] Available from: 2. Bergstad O.A, Skjaeraasen J.E. Distribution and feeding ecology of Raja radiata in the northeastern North sea and Skaerrak(Norwegian Deep)[internet] June 5[cited 2009 July 28]; 57(1) : (12 pages). Available from: http: 3. Chevolot M, Olsen J.L, Rijnsdorp A.D, Stam W.T, Wolfs P.H.J. Population Structure and historical demography of the Thorny Skate( Amblyraja radiata, Rajidae) in the North Atlantic. Marine biology[internet] 2006 Dec 19[cited 2009 August 1] ; 151(10) : (12 pages). Available from: 1286/151/10.http://www.biomedcentral.com/ /151/10 4. Danley P.D, Elzey S, Howell W.H, Jurek J, Kneebone J, Tsang P.C.W. Age and growth estimate of the thorny states (Amblyraja radiata) in the Western Gulf of Maine. Fish Bulletin [internet] 2003 August 21 [cited 2009 August 4] 103(1): (9 pages) Available from:


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