Sharks play an essential rol in the health of our oceans

Skate

Dipturus batis

 

 

The skate is is a member of the family of rays (Rajidae) ad the order of the rays and skates (Rajaformes). It is the largest endemic ray species, most frequently found on a depth of 100 to 200 meters. Juveniles prefer shallower waters. Blue skates feed on wurms, smelt, flatfish and crabs. The blue skate used to be common along the Dutch and Belgian shores, but the number of sightings has decreased dramatically.

 

Picture by A.W. Gmelig Meyling, Stichting ANEMOON

 

The blue skate  lays eggs, and is therefore oviparous.  The green eggs are deposited in pairs, in spring and summer. They change to brown during their development. The eggcases are large and can measure 13 x 24 cm.

 

  • Maximum length: 285 cm
  • Maximum weight: 975 kg
  • Maximum lifespan: 50 years
  • Habitat: maximum 1000 meter depth
  • Catches: there is a total allowable catch for rays and skates in the North Sea, but not specifically for the blue skate. Regulations are considered urgently needed, but more catch data are needed. Blue skates have to be released when caught in the North Sea. The blue skate has disappeared from the southern North Sea.
  • Status: ‘Critically Endangered’ on the  international IUCN Red List (http://www.iucnredlist.org/).

Picture: Pieter van der Sluis

 

Genetic research (Taxonomic confusion and market mislabelling of threatened skates: important consequences for their conservation status, Iglésias, Toulhoat, Sellos, published november 2009), has revealed that the Common Skate, Dipturus batis, is in fact two  distinct species, named Dipturus intermedia and Dipturus  flossada. The two species appear to have different, partly overlapping distributions that seem to be related to water temperature and different biological characteristics. Of the two, D. intermedia is slower growing and larger.  The first data published suggests a size at 50% maturity of 197.5cm for females and 185,5cm for Dipturus intermedia, compared to 122.9cm and 115cm for males Dipturus 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.

This taxonomic confusion puts into question all previously accumulated data based on D. batis. Its endangered status highlights the need for an extensive reassessment of population collapses with accurately identified species.

Distribution

 

 

 

Contact info

You can contact us at +31 (0) 6 12195593 Or per email at: georgina@dutchsharksociety.org

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