Barndoor skate (Dipturus laevis)

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Barndoor skate
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Barndoor skate fact file

Barndoor skate description

KingdomAnimalia
PhylumChordata
ClassChondrichthyes
OrderRajiformes
FamilyRajidae
GenusDipturus (1)

The largest skate in the Northwest Atlantic (1) (2) (3) (4), the barndoor skate has a pointed snout and a flattened body, which is fused to the expanded pectoral fins to form a broad disc, with sharply angled corners, concave front edges, and rounded back edges (2) (3) (4). The tail is moderately short, bears three rows of spines, and has two small dorsal fins set close together near its tip. The upper surface of the barndoor skate is brown to reddish-brown in colour and marked with many small, scattered, dark spots, while the underside is white, with irregular grey blotching (2) (3) (4). Interestingly, mature male and female barndoor skates possess quite different teeth, with those of the female being close-set, with rounded cusps, while those of the male are widely spaced, arranged in rows, and have sharply pointed cusps (3).

Also known as
barn-door skate, barndoor winter skate, barn-door winter skate.
Synonyms
Raja laevis.
Size
Length: up to 153 cm (1) (2)
Weight
up to 20 kg (1) (2)
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Barndoor skate biology

This large skate is slow-growing and long-lived (3) (4), taking at least 6 or 7 years to reach maturity (5), and potentially living for up to 18 years (1) (2). In captivity, the barndoor skate has been recorded breeding year-round, with egg-laying highest in the autumn and lowest in the spring. One female was recorded to lay between 69 and 115 eggs per year (6). The eggs are laid in smooth, rectangular, yellowish or greenish capsules, around 16 centimetres in length and with short, stiff horns at each corner (3) (4) (6). The egg capsules are deposited in sandy or muddy flats (3) (4), and may hatch after around 11 to 16 months (6). The young barndoor skates average about 19 centimetres in length (3) (6), with males reaching maturity at an estimated 107 to 112 centimetres, and females at around 116 centimetres (1) (2) (5).

The diet of the barndoor skate consists mainly of bottom-dwelling species, including fish, squid, crustaceans, bivalves, worms and gastropods (1) (2) (3) (4), with larger individuals capable of taking larger and more active prey (3). This skate’s size means that, as an adult, large sharks are probably its only potential predators (3) (4).

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Barndoor skate range

The barndoor skate occurs in the northwest Atlantic Ocean, along the Atlantic coast of the USA and Canada, where it has been recorded from the northeast coast of Florida to the banks of Newfoundland, the southern Gulf of St. Lawrence, and the outer coast of Nova Scotia (1) (2) (3) (4). Seasonal migrations may occur, the skates moving offshore during the warmer summer and autumn months, and returning to inshore waters in winter and spring (3) (4).

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Barndoor skate habitat

This species is usually found in relatively cool waters, over a range of ocean bottom types, including sand, soft mud and rock (1) (2) (3). Although recorded from the shoreline to depths of 715 metres or more, possibly even to 1,400 metres (1) (2), it is most commonly found at depths of less than 140 to 150 metres (3) (4).

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Barndoor skate status

Classified as Endangered (EN) on the IUCN Red List (1).

IUCN Red List species status – Endangered

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Barndoor skate threats

Although not specifically targeted by fisheries, the barndoor skate has often been taken as bycatch in commercial trawl nets, and as part of a complex of several skate species fished in USA waters. There is also a directed fishery for dogfish and skates on the Georges Bank, which is thought to have led to a decline in this species. The flesh of this and other skates is used as lobster bait, fish meal and pet food, and the meat from its ‘wings’ (the pectoral fins) is sold as seafood (1) (2) (3) (4).

In recent years, it was believed that the barndoor skate had come to the brink of extinction, with catch rates in USA waters having declined by an alarming 96 to 99 percent between the 1960s and 1990s (1) (2) (3) (7). However, its status has since been brought into question, with new studies of the species’ life history suggesting that it may be more resilient to overfishing than previously thought (5). Although its slow growth, late maturity, large size and low number of offspring still make the barndoor skate vulnerable to overexploitation (1) (2) (4) (5) (7), a reduction in fishing effort is thought to have allowed the species to start recovering. However, any increase in fishing effort or the opening of ‘no-take’ areas may cause it to decline once more (1) (2).

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Barndoor skate conservation

Since it was reported to be near to extinction in 1998 (7), the status of the barndoor skate has been the subject of much debate, and a number of petitions have been made to list the species under the US Endangered Species Act (1) (2). The National Oceanic and Atmospheric Administration (NOAA) listed the barndoor skate as a ‘Species of Concern’ (4), but it was removed from the list in early 2010 after it was decided that there was no evidence the species was in imminent danger of extinction (8). There has been a ban on possession of the species in US waters (3) (4), and, most significantly, no-take zones in areas such as Georges Bank appear to have led to decreased mortality (9) and an increase in the number of juveniles (1) (2) (3), suggesting that areas protected from trawling would be effective in allowing the barndoor skate population to recover (1) (2) (7). This large skate may also benefit from further research to better understand its conservation status and the threats it faces.

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Find out more

To find out more about the barndoor skate see:

For more information on the conservation of sharks, rays and skates, see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Bivalves
In this group of aquatic molluscs the soft parts are encased in a shell consisting of two parts known as valves.
Bycatch
In the fishing industry, the part of the catch made up of non-target species.
Crustaceans
Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
Dorsal fin
The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
Gastropods
A group of molluscs that have a well-defined head, an unsegmented body and a broad, flat foot. They can possess a single, usually coiled shell or no shell at all. Includes slugs, snails and limpets.
Pectoral fins
In fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
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References

  1. IUCN Red List (May, 2010)
    http://www.iucnredlist.org/
  2. Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (2005) Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. IUCN/SSC Shark Specialist Group, IUCN, Gland. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/2005-029.pdf
  3. Barndoor Skate Biological Profile, Ichthyology Department, Florida Museum of Natural History (May, 2010)
    http://www.flmnh.ufl.edu/fish/Gallery/Descript/BarndoorSkate/BarndoorSkate.html
  4. NOAA National Marine Fisheries Service - Species of Concern: Barndoor skate Dipturus laevis (May, 2010)
    http://www.nmfs.noaa.gov/pr/pdfs/species/barndoorskate_detailed.pdf
  5. Gedamke, T., DuPaul, W.D. and Musick, J.A. (2005) Observations on the life history of the barndoor skate, Dipturus laevis, on Georges Bank (Western North Atlantic).  Journal of Northwest Atlantic Fishery Science, 35: 67-78.
  6. Parent, S., Pépin, S., Genet, J.P., Misserey, L. and Rojas, S. (2008) Captive breeding of the barndoor skate (Dipturus laevis) at the Montreal Biodome, with comparison notes on two other captive-bred skate species. Zoo Biology, 27: 145-153.
  7. Casey, J.M. and Myers, R.A. (1998) Near extinction of a large, widely distributed fish. Science, 281: 690-692.
  8. NOAA National Marine Fisheries Service: Barndoor skate (Dipturus laevis) (May, 2010)
    http://www.nmfs.noaa.gov/pr/species/fish/barndoorskate.htm
  9. Gedamke, T., Hoenig, J.M., DuPaul, W.D. and Musick, J.A. (2008) Total mortality rates of the barndoor skate, Dipturus laevis, from the Gulf of Maine and Georges Bank, United States, 1963-2005. Fisheries Research, 89: 17-25.
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Barndoor skate  
Barndoor skate

© Andy Murch / Elasmodiver.com

Elasmodiver.com
andymurch1@gmail.com
http://www.elasmodiver.com

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