Skates migrate to popular advice map

Alongside a host of other fish and crustacean stocks, various species of skate are the latest additions to ICES interactive popular advice map.
Published: 31 October 2014

​Parallel to its official advice, ICES delivers popular advice – that is, more accessible, easy-to-read versions of the advice targeting a wider audience. Initially available as single stock sheets, in July this year popular advice for all ICES stocks (194 at the time) was collated into an online map.

Now, several stocks of skates have become the latest to move over to the map, an interactive application that presents users with a panoramic of all the different stocks across a map of the ecoregions.

“This is the first year that we are publishing popular advice on skates,” explains ICES Advisory Programme Professional Officer Anne Cooper. “Not only is the popular advice a great medium for making science accessible, but the newly available map interface enables even more access to information on where ICES provides advice on elasmobranches, what these animals look like and where they’re harvested.”

Let's talk about rays - or skates?

Skates, along with rays and sharks, make up a taxonomic subclass of fish known as elasmobranchs, classified as such due to their skeletons being composed of cartilage rather than bone – a feature they still share with their ancestors from 400 million years ago. Other characteristics that distinguish them from their bony cousins include the presence of multiple gill slits rather than just one and the absence of swim bladders.

One such species is the thornback ray. A prickly-backed, diamond shaped marine predator belonging to the Rajidae family, the thornback glides across the seafloor hunting for crabs, shrimp, and shellfish using a sixth sense which perceives the smallest of shifts in electricity, a skill matched by its ability to camouflage itself by burying into the soft sand and mud.

What’s also remarkable is that the thornback ray represents a popular misnomer: the species is actually technically a skate. Whilst rays give birth to live young and have longer, rope-like tails (some complete with stinging barbs), skates such as the thornback lay eggs and have shorter tails. 

Distributed across a stretch of the coastal eastern Atlantic from the Faroe Islands and Iceland down to South Africa, the thornback, like other species of skate, sets off for the inshore shallows in spring to spawn. Ecologically, this means the thornback has been described as being philopatric – that is, the tendency shown by migratory species to head to a specific site to give birth.

Ray-sing the subject

Laying its eggs (small pouches known as mermaids’ purses) on the sandy, gravelly or muddy sea bottoms on which it spends its life is a life-trait common to all skates like the thornback. It’s one of many biological traits that are the domain of ICES Working Group on Elasmobranch Fisheries (WGEF) – experts who deal with not only the thornback, but a variety of stocks of other skates and sharks.

WGEF, in addition to exploring the science at its June meeting in Lisbon, also plays a key role in the development of ICES advice on elasmobranch stocks, with this year’s advice having just been issued – covering populations of skates in the area denoted by ICES as the Celtic Seas and Bay of Biscay and Iberian coast ecoregions.

Map migrants

And it’s the Bay of Biscay and Celtic Seas ecoregions where, as of 16 October, the skates that constituted the recent advice became the latest migrants to the popular advice map. Alongside the thornback ray are various Celtic Seas and Bay of Biscay stocks of the blonde ray, cuckoo ray, sandy ray, shagreen ray, small-eyed ray, spotted ray, and undulate ray. All of them, just as the thornback, skates and not rays – despite the names.

Outside the world of elasmobranchs, other new arrivals on popular advice map include northern shrimp in the Barents, North and Norwegian seas and the small forage fish capelin in the northeast Arctic. These will be joined by Norway lobster in the Celtic Sea in early November.

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Each orange dot on the map signifies one of ICES stocks, and the thornback ray is now one of them.

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Skates migrate to popular advice map

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