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Dipturus laevis

(Barn-Door Winter Skate)

Overview

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Family : Skates ; Occur from water's edge to 430 m depth; absent from shoal waters in south during warm months[1]. Found in salinities that range from 35 along the continental edge to 31.5 inshore along the open coast and as low as 21-24[2]. Live on all kinds of bottom . Feed on bivalve mollusks, squids , rock crabs, lobsters, shrimps, worms and fishes . Oviparous . Distinct pairing with embrace. Young may tend to follow large objects, such as their mother[3]. Eggs are oblong capsules with stiff pointed horns at the corners deposited in sandy or muddy flats[3]. Egg capsules are 7.1-13.2 cm long and 4.6-7.4 cm wide[4]. Little use is made of the small quantities that are caught. In some cases, they are made into fish meal .

Endangered
Threat status

Common Names

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Click on the language to view common names.

Common Names in Danish:

Ladeportsrokke

Common Names in Dutch:

Deurrog

Common Names in English:

Barn-Door Skate, Barn-Door Winter Skate, Barnards Lanternfishes, Barndoor Skate

Common Names in French:

Grande Raie

Common Names in Mandarin Chinese:

滑鰩

Description

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Family Rajidae

Benthic rays occurring in all oceans, from Arctic to Antarctic waters and from shallow coastal shelfs to abyssal regions; rare in tropical shallow waters or near coral reefs; some species enter brackish waters. Disc quadrangular to rhomboidal . Mouth transversed to arched, with numerous teeth. Five pairs of ventral gill slits . Tail very slender, with lateral folds, usually 2 reduced dorsal fins and a reduced caudal fin. Electric organs weak, developed from caudal muscles. Skin prickly in most species, the prickles often in a row along midline of dorsal. Oviparous ; eggs in a horny capsule with four long tips . A reversal to egg-laying from live-bearing was observed in this group based on fossil records [5]. Skates feed on other benthic organisms. Skate wings are considered good eating. The following subgenus have been elevated to the genus level: Amblyraja, Dipturus, Fenestraja, Leucoraja, Okamejei, Rajella, Rostroraja[6].The family Rajidae belongs to the Class Elasmobranchii (sharks and rays) and the Order Rajiformes. It contains 14 genera and 200 species. It may be found in Marine and Brackish environments and is primarily Marine. Members of this family are not used in the aquarium trade. Reproductively, most members of this family are nonguarders. The main mode of swimming of adult fish in this family is rajiform. Compared with other fish, the activity level of this family tends to be normal. Members of this family have been dated back to the Cretaceous period. Etymology of this family name : Latin, raja = ray

Physical Description

Species Dipturus laevis

Distinctive Features: The broad disk of the barndoor skate has sharply angled corners and a pointed snout. The front edges of the skate's disk are concave and its dorsal fins are close together. The posterior disk corners are rounded and the tail is moderately short. The barndoor skate can be distinguished from other skates by a straight line that begins at the snout and ends at the anterior margin of the outer corner of the disk, but does not intersect the disk.

Dentition: The teeth of female and immature male barndoor skates are close-set and have rounded cusps. Teeth of mature males are widely spaced and arranged in rows , with sharp-pointed cusps . The upper jaw of this skate consists of 30- to 40-tooth rows and the rows of the lower jaw each contain between 28 and 38 teeth.

Denticles : Denticles are absent from small specimens of the barndoor skate. Larger specimens have relatively small thorns on anterior and posterior orbital rims and along the midline and in a line along the lateral aspect of the tail and between the dorsal fins. Mature females also possess dermal denticles on the head and shoulders , and along the dorsal midbelt of the disk and tail. The thorns are absent from the dorsal midline of the disk and from the shoulder region of the skate to the base of the tail.

Color:

The upper surface of the barndoor skate is brown to reddish brown. This surface is marked with darker spots and blotches, along with lighter streaks and reticulations . In particular, the center of each pectoral fin is marked with an oval spot or blotch . The barndoor skate has a light, white to gray, lower surface. This surface is marked with gray blotches on the snout that are more numerous in larger individuals. Both surfaces contain darkly pigmented ampullar pores near the eyes, snout and on much of the anterior disk.

Size/Age/Growth

The barndoor skate is one of the largest skates in the north Atlantic Ocean. It is long-lived and slow growing. Reportedly, one captured specimen measured nearly 59 inches (150 cm) TL and weighed almost 40 pounds (18.0 kg ). There have been unconfirmed reports of specimens that have reached 71 inches (180 cm) TL. Studies show that a barndoor skate weighing 4-7 pounds (2-3 kg) averages a length of 28-30 inches (71-76 cm).

Habitat

The barndoor skate can be found on various types of ocean bottom including soft muddy, sandy, and rocky bottoms. It can be found from shoreline to, though it is most abundant at depths less than 492 feet (150 m ), depths of up to 2,460 feet (750 m). The broad temperature range in which the barndoor skate lives and breeds , from just above freezing to 68°F (20°C), can account for the depth distribution of the species. Though the barndoor skate has been found in brackish water where the salinity is 21 to 24 parts per thousand (ppt), it prefers salinity between 31 and 35 ppt.

Typically found in water with a depth of 0 to -2,697 meters (0 to -8,848 feet).[7]

Biome: Saltwater . Demersal .

Ecology: The barndoor skate attains a maximum length of 153 cm and a maximum weight of 20 kg ; the largest skate species in the Northwest Atlantic and eleventh largest in the world (Bigelow and Schroeder 1953). Age at maturity was assumed to be similar to that of the common skate D. batis (the sister species from the Northeast Atlantic): an estimated 11 years (Casey and Myers 1998), but this is likely to be an overestimate. Age at maturity has been estimated as eight years by extrapolating from skate allometric relationships (Frisk et al. 2001). The average age of mature individuals in the population (generation length ) therefore can be estimated to be 10 to 14 years. It is likely that the lower value for age at maturity is closer to reality. Longevity has been estimated as between 13 and 18 years, assuming that the age of maturity is 60% of the lifespan, then age at maturity can be assumed to be 8 to 11 years (Frisk et al. 2001). Length frequency data indicate few adult individuals remaining in the population, with these generally less than 130 cm long. However, these data were using a sample gear (scallop dredge ) that may underestimate the abundance of larger size classes.

Length at maturity has been estimated to be 115 cm for females and 112 cm for males (T. Gedamke, pers. comm. ), but these may have changed due to variations in population density , food availability and exploitation rates. Egg production is estimated as 47 per year, based on the inverse relationship between fecundity and weight of hatchlings and common skate life history parameters (Casey and Myers 1998). Body size is a good general predictor of demography and vulnerability to exploitation in skates ; the large size of the barndoor skate suggests that it is one of the most vulnerable of all the skates (Dulvy et al. 2000, Dulvy and Reynolds 2002, Frisk et al. 2002, Frisk et al. 2001, Musick et al. 1999, Walker and Hislop 1998).

The diet includes bivalves , squid, rock crabs, lobsters, shrimps, worms and fishes (Packer et al. 2003, Robbins and Ray 1986).[8]


List of Habitats :9.1Marine Neritic - Pelagic 10.1Marine Oceanic - Epipelagic (0-200m)

Biology

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Diet

The prey of the barndoor skate consists mainly of fishes and invertebrates associated with the bottom . Such food items include polychaetes , gastropods , bivalve mollusks, squids , crustaceans and fishes. Small individuals subsist on benthic invertebrates such as polychaetes, copepods , amphipods , isopods , crangon shrimp, and euphausiids . Larger specimens are capable of capturing larger and more active prey, including razor clams, large gastropods, squids, cancer crabs, spider crabs, lobsters and fishes. Garman noticed that many times, the thorns on the snout of barndoor skates are worn smooth , as though the snout is used to dig in the mud or sand to obtain bivalve mollusks.

Reproduction

The barndoor skate is oviparous , meaning it lays eggs from which the young hatch . The skate becomes sexually mature at 11 years of age and reproduction takes place over the entire range of the species. During mating it is known that a distinct pairing with embrace occurs; though this activity has not been studied extensively in this species. The barndoor skate deposits single fertilized eggs in the yellowish and greenish egg capsules in sandy or muddy flats. Incubation takes approximately 6 to 12 months. The smooth egg capsules of the skate are rectangular, with a short horn at each corner and fine filaments along the anterior and posterior margins . Though small specimens are rarely captured, hatchlings have been measured at (180-190 mm) TL . It has also been noted that young barndoor skates tend to follow large objects such as their mother.

Behavior

Predators:

Due to the large size of the barndoor skate, large sharks are its only likely predator of adult barndoor skates .

Parasites:

The numerous parasites of this skate include turbellarians, trematodes , cestodes, nematodes and copepods

Taxonomy

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Ambiguous Synonyms

  1. Raia granulata Gill, 1879

Unambiguous Synonyms

  1. Raja laevis Mitchill, 1818

Notes

Name Status: Accepted Name . Ambiguous Synonym: Raia granulata. Latest taxonomic scrutiny: September 30, 1999.

The barndoor skate was described in 1818 by Mitchill with the original combination of Raja laevis. The scientific name was later changed to the currently valid name Dipturus laevis . The genus name, Dipturus, is derived from the Greek words, di, meaning two, and pteryx, meaning fin . Raja, the original genus of Dipturus laevis , which was coined by Linnaeus in 1758, is still recognized as a valid subgenus .

Common Names : The common name in the English language include barndoor skate, barn-door skate, and barn-door winter skate. Other language common names include deurrog (Dutch), grande raie (French), and ladeportsrokke (Danish).

Similar Species

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Members of the genus Dipturus

ZipcodeZoo has pages for 46 species and subspecies in this genus:

D. australis · D. batis (Common European Skate) · D. bullisi (Tortugas Skate) · D. campbelli (Blackspot Skate) · D. cerva · D. chilensis (Yellownose Skate) · D. crosnieri (Madagascar Skate) · D. diehli (Thorny Tail Skate) · D. doutrei (Javelin Grunter) · D. ecuadoriensis (Ecuador Skate) · D. flavirostris · D. garricki (San Blas Skate) · D. gigas (Giant Skate) · D. gudgeri (Greenback Skate) · D. innominata · D. innominatus (New Zealand Smooth Skate) · D. johannisdavisi (Travancore Skate) · D. kwangtungensis (Ocellate Spotskate) · D. laevis (Barn-Door Winter Skate) · D. lanceorostratus (Rattail Skate) · D. lemprieri · D. leptocauda (Thintail Skate) · D. leptocaudus (Thintail Skate) · D. linteus (Sharp-Nosed Skate) · D. macrocauda (Bigtail Skate) · D. mennii · D. nasuta · D. nasutus (New Zealand Rough Skate) · D. nidarosiensis (Norwegian Skate) · D. olseni (Spreadfin Skate) · D. oregoni (Hooktail Skate) · D. oxyrinchus (Long-Nosed Burton Skate) · D. polyommata (Argus Grouper) · D. pullopunctata (Slime Skate) · D. pullopunctatus (Slime Skate) · D. sp. nov. L · D. springeri (Roughbelly Skate) · D. stenorhynchus (Prow-Nose Skate) · D. teevani (Prickly Brown Ray) · D. tengu (Acutenose Skate) · D. trachyderma (Roughskin Skate) · D. trachydermus (Roughskin Skate) · D. whitleyi · D. kwangtungensis · D. kwangtungensis · D. nidarosiensis

More Info

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Further Reading

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal March 01, 2008:

Identifiers

Footnotes

  1. Robins, C.R. and G.C. Ray (1986). A field guide to Atlantic coast fishes of North America. Houghton Mifflin Company, Boston, U.S.A. 354 p. [back]
  2. Bigelow, H.B. and W.C. Schroeder (1953). Sawfishes, guitarfishes, skates and rays. p. 1-514. In J. Tee-Van et al. (eds.) Fishes of the western North Atlantic. Part two. New Haven, Sears Found. Mar. Res., Yale Univ. [back]
  3. Breder, C.M. and D.E. Rosen (1966). Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. [back]
  4. Bor, P. (2002). Egg-capsules of sharks and skates. www.rajidae.tmfweb.nl/rogtabel.html [back]
  5. Dulvy, N.K. and J.D. Reynolds (1997). Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays. Proc. R. Soc. Lond. B 264:1309-1315. [back]
  6. McEachran, J.D. and K.A. Dunn (1998). Phylogenetic analysis of skates, a morphologically conservative clade of elasmobranchs (Chondrichthyes: Rajidae). Copeia 1998(2):271-290. [back]
  7. Mean = -488.180 meters (-1,601.640 feet), Standard Deviation = 840.130 based on 491 observations. Ocean depth information for each observation from British Oceanographic Data Centre. [back]
  8. Dulvy, N.K. 2003. In IUCN 2008. 2008 IUCN Red List of Threatened Species. IUCNRedList.org. Downloaded July 19, 2008. [back]
Last Revised: August 12, 2009