1 (edited by stevemcbill 11-03-2015 16:35:03)

Topic: Two Species of Skate

Chris,

See the website and comment by Andy Horton below:

Two species of Skate: http://www.sciencedaily.com/releases/20 … 191048.htm
From the mid-19th century the Common Skate was described as two distinct species, the Flapper Skate, D. intermedia, and the Blue Skate, D. flossada.

Andy Horton:-  Since this factsheet was produced, genetic research has revealed that the Common Skate, Dipturus batis, is in fact two distinct species. These have been named D.intermedia and D.flossada.  Common names already in use for these species are the Flapper Skate and Blue Skate respectively, although it remains to be seen if these become widely accepted. The two species appear to have different distributions and biological characteristics.  Of the two, D.intermedia is slower growing and reaches a larger size. The first data published suggests a size at 50% maturity of 197.5cm (♀) and 185.5cm (♂) for D.intermedia, compared to 122.9cm (♀) and 115cm (♂) for D.flossada.  The largest positively identified specimen of D. flossada was 143.2cm in length. It seems the maximum total length of 285cm previously attributed to D. batis must be D. intermedia.  While the ranges of the species overlap it appears that D.intermedia is limited to west Scotland and west Ireland, with D.flossada limited to the southern Irish and Celtic Seas and the Rockall Trough.  This appears to be closely related to temperature. The most reliable means of distinguishing these species seems to be the colour of the iris. In D. intermedia it is dark green/olive, in D.flossada it is pale yellow.  Other morphometric features to check are the malar thorns, lateral tail thorns, interdorsal space and tooth bases.  Colouration can differ on the ventral surface and on the centre of the wings.  For a full discussion of these differences see Iglésias et al., 2009, available online. http://www.sharktrust.org/.../common_sk … tsheet.pdf

Steve

Steve J. McWilliam
www.rECOrd-LRC.co.uk
www.stevemcwilliam.co.uk/guitar/

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Re: Two Species of Skate

And more:

Andy Horton:-  Current status of the species:  Further deterioration in the status of Common Skate (Dipturus batis) has been reported since it was included on the OSPAR List, particularly in Regions II and III.   The species is now assessed as “Critically Endangered” globally on the IUCN Red List of Threatened Species (Dulvy et al. 2006). Furthermore, recent genetic research (Iglésias et al. in press 2009) indicates that the species reported as Dipturus batis is actually comprised of two large threatened species of Dipturus (provisionally D. cf. flossada and D. cf. intermedia), and that recorded landings of D.batis also include Norwegian Skate D.nidarosiensis, particularly from deepwater fisheries.  The implications of these observations are that members of the ‘D. batis’ species complex are even more depleted than formerly understood. http://qsr2010.ospar.org/.../Species/P0 … _skate.pdf

Steve

Steve J. McWilliam
www.rECOrd-LRC.co.uk
www.stevemcwilliam.co.uk/guitar/

3

Re: Two Species of Skate

Thanks Steve - will research and get back to you here

Chris Raper, Manager of the UK Species Inventory, Angela Marmont Centre for UK Biodiversity,
Natural History Museum, Cromwell Road, London, SW7 5BD.  (tel: 020 7942 5894)
also Tachinid Recording Scheme (http://tachinidae.org.uk/)

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Re: Two Species of Skate

Hi Steve

WoRMS hasn't accepted the split yet but I have gone with our local authority, the Shark Trust, who consider them distinct species. Also there is a significant conservation concern to think about which suggests that we should map them differently - as the Common Skate they were endangered but now as 2 species each is even more at risk.

Dipturus intermedia (Parnell, 1837)
tvk NHMSYS0021053471
Flapper Skate
tvk NHMSYS0021123382

Dipturus flossada (Risso, 1826)
tvk NHMSYS0021053470
Blue Skate
tvk NHMSYS0021123376

I have left the 'aggregate' species batis as it is, for records which do not make the distinction. Perhaps when the split is more formally accepted batis will officially become an aggregate in terms of UK records.

Thanks :)

Chris Raper, Manager of the UK Species Inventory, Angela Marmont Centre for UK Biodiversity,
Natural History Museum, Cromwell Road, London, SW7 5BD.  (tel: 020 7942 5894)
also Tachinid Recording Scheme (http://tachinidae.org.uk/)

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Re: Two Species of Skate

Thanks Chris !! :-)

Steve J. McWilliam
www.rECOrd-LRC.co.uk
www.stevemcwilliam.co.uk/guitar/