There are seven species of skate taken as groundfish in trawl fisheries off the northeastern seaboard of the United states-barndoor skate (Dipturus laevis), clearnose skate (Raja eglanteria),little skate (Leucoraja erinacea), rosette skate (Leucoraja garmanii), smooth skate (Malacoraja senta), thorny skate (Amblyraja radiata), and winter skate (Leucoraja ocellata).
Skates are elasmobranches, closely related to sharks.
The elasmobranchs, a group of fishes with cartilaginous skeletons and plate-like scales, are vulnerable to overfishing because of their long lives, late reproductive ages and relatively low fecundity. Skates lay eggs, producing small clutches of leathery egg cases sometimes called mermaid’s purses.
This method of reproduction is different from their cousins, the Stingrays, which produce live young.
Like stingrays, skates are bottom-dwellers and they are often found resting on the seafloor or hiding partly submerged in soft sediment.
They prey upon bottom fishes, worms, crustaceans, and mollusks, using flat, molar-like teeth to crush hard-shelled prey.
Essential habitats for these seven species of skates include bottom habitats with substrates of sand, mud, gravel, and/or broken shell, and pebbles.
Historically, this species has not been commercially important, only used only as bait and often discarded as trash fish. Skates have become an increasingly important fishery as the populations of other bottom-dwelling fish (particularly cod and haddock) have become depleted. As a result, several of the skate species in the Northeast are over fished or have suffered deep declines. There has also been some marketing of skate meat as scallops using round cuts from the skate wings.
Skates are mainly caught using otter trawl gear, which causes considerable habitat damage to seafloor habitats. Otter trawling is also indiscriminate; this method catches both unintended and intended species.
These unintended species are unmarketable, illegal or undersized individuals that are subsequently discarded dead or dying as bycatch.
By establishing an international fishing limit for a species of skate, the multi-national North Atlantic Fisheries Organization has become the first international fishery management body to implement measures for a species of elasmobranch – the class shared by sharks, skates and rays. Beginning in 2005, NAFO established a total allowable catch of 13,500 tonnes for thorny skates (Amblyraja radiata) in Canadian and international waters around Newfoundland’s Grand Bank.
Until then, no international restrictions on shark, skate or ray fisheries had been adopted, despite growing awareness of their plight worldwide. According to the NAFO Scientific Council, thorny skate populations declined significantly between 1985 and 1994, and they continue to hover near historic low levels. The relatively few remaining skates are concentrated on the southwestern part of the Grand Bank – a distribution similar to that observed for northern cod just prior to their collapse.
Scientists at a recent IUCN-World Conservation Union assessment workshop proposed that the thorny skate be added to the IUCN Red List of Threatened Species.
The U.S. National Marine Fisheries Service has highlighted thorny skate as a Species of Concern and prohibits possession of this species under the Northeast Skate Fishery Management Plan.
Taken together, their vulnerability to overfishing result in an overall seafood recommendation of ‘Avoid’ for all Northeast skate species. A sustainable alternative is farmed scallops, such as the Bay Scallop (Argopecten irradians).
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