Common skate species complex

Flapper Skate (Dipturus intermedius) and
Common Blue Skate (Dipturus batis)

Historically, the common skate was one of the most abundant and widespread skates in the Northeast Atlantic. Since 2010, biologists have reclassified the fish historically identified as common skate into two separate but similar and related species: the common blue skate (Dipturus batis) and the flapper skate (Dipturus intermedius). Both species are listed as Critically Endangered by the IUCN Red List.

Flapper skate are considerably larger than blue skate as fully grown adults, and common blue skate tend to have a more offshore distribution. Historical catch statistics generally have not differentiated between the two species, which fisheries scientists often currently group as a common skate species complex to make up for otherwise limited data.

The flapper skate is the largest skate in the world, reaching lengths up to at least 254 cm total length. It can be found at depths from 10 metres to 1,600 metres. The common blue skate is a medium-sized skate reaching to at least 143 cm total length. It can be found in depths from 10 metres to 600 metres.

For both species, their large body size renders them vulnerable to mortality as fisheries by-catch even from birth.

The Marine Sportfish Tagging Programme tagged 1,159 common skates between 1972 and 2014 off the coast of Ireland, with 88% of taggings in the vicinity of just five sites: Clew Bay, Baltimore, Courtmacsherry, Ballycastle Bay and Tralee Bay. The programme has shown that 89% of recaptures of tagged fish occur close to their original tagging locations.