Barndoor skate

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Barndoor skate
Barndoor skate, Dipturus laevis

Least Concern (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Rajiformes
Family: Rajidae
Genus: Dipturus
Species:
D. laevis
Binomial name
Dipturus laevis
(
Mitchill
, 1818)

The barndoor skate (Dipturus laevis) is a

North Atlantic Ocean, reaching lengths up to 1.5 m (5 ft). It is carnivorous, feeding on invertebrates and other fish
found near the sea floor.

After peaking in the 1950s, the population of the barndoor skate dramatically declined in the 1960s and early 1970s as a result of overfishing. In 2003, it was listed as endangered by the

World Conservation Union. However, barndoor skate populations have increased substantially since 1990 and even surpassed 1960s population size by 2012. In 2019, the barndoor skate was downlisted to least concern by the IUCN based on its largely increased population, new protections within its range, and also minor expansions to its range.[1] In most cases, the barndoor skate is not intentionally harvested by the commercial fishing industry—it is usually considered bycatch in the trawling
nets used to target other species of fish.

Description

Skeleton

The barndoor skate is a flat-bodied fish with a large, disk-like body with sharply angled corners and a pointed snout. Its

pectoral fins have evolved into broad, flat, wing-like appendages used to propel the fish through the water. These fins have a concave front edge with rounded posterior corners. Like sharks, it has a boneless skeleton made of cartilage, a tough, elastic substance composed of collagenous and/or elastic fibers, cells, and a firm, gel-like substance called the matrix. It has slot-like body openings called gill slits on the underside of the body beneath the pectoral fins that lead from the gills. The dorsal fins are close together and far removed from the tail.[3] It has two eyes on its dorsal surface, located about 5.5 centimeters (2.2 in) apart.[2]

The fish's upper surface is brown to reddish brown with many scattered darker spots, lighter streaks, and reticulations. The center of each

pectoral fin is marked with an oval spot or blotch. The lower surface is light, white to grey, blotched irregularly with gray spots.[3][4] The barndoor skate is unique from other species of skate in its having a straight line that begins at the snout and ends at the anterior margin of the outer corner of the disk, but stopping short of the disk.[3]

The barndoor skate is one of the largest skates found in the

North Atlantic Ocean.[2] It can reach lengths of up to 1.5 m (5 ft) and can weigh up to 18 kg (40 lb).[5] There have been unconfirmed reports of individuals reaching lengths of 1.8 meters (6 ft).[3] A 71–76 cm (28–30 in) barndoor skate typically weighs 2–3 kg (4–7 lb).[3]

The tail is moderately short and does not have large, thorn-like structures called

dermal denticles that are normally found on skates. This lack of denticles distinguishes it from all but two species of skates found in the western Atlantic.[2] Larger individuals do have three rows of smaller denticles on the tail, and mature females also possess denticles on the head and shoulders, and along the dorsal midbelt of the disk and tail. Denticles are completely absent on small individuals.[3]

Habitat

The barndoor skate occurs in a range extending from the banks of

shoreline to depths to 750 m (2,460 ft), although it is most commonly found at depths less than 150 m (500 ft). It inhabits waters in a broad range of temperatures, from just above freezing to 20 °C (68 °F).[6] It appears to move closer to shore in the autumn and further out to sea in the warmer months. It tolerates brackish water where the salinity is as low as 21 to 24 parts per thousand, but it prefers salinity between 31 and 35 parts per thousand.[5] It is believed to not exhibit any north-south migratory
patterns.

Diet

The fish is

euphausiids.[8] Individuals have been found with the denticles on the snout worn smooth, indicating that the snout is used to dig in the mud or sand to obtain bivalve mollusks.[3]

Importance to humans

The barndoor skate is one of five skates in the

commercial trawlers operating in the northwestern Atlantic that target other commercially valuable species of fish using bottom trawling.[5] When harvested, the flesh of the barndoor skate is used as bait, fish meal, and pet food, and the meat from its wings is sold for human consumption.[3] Since 1981, landings of skates have increased substantially, partly in response to increased demand for lobster bait, and more significantly, to the increased export market for skate wings.[9] The commercial retention and sale of barndoor skates was prohibited in the United States from 2003 until 2018.[1]

Conservation

Barndoor skate caught during an NOAA research cruise

Abundances of barndoor skate dropped precipitously in the 1960s and early 1970s, coinciding with the period of intense fishing by foreign factory trawlers. The abundance remained very low through around 1990, but increased nearly exponentially from 1990 to 2005, and have been approaching the levels observed in the 1960s.

World Conservation Union had listed the barndoor skate as "vulnerable" under the 1994 Categories and Criteria, but in 2003, it reassessed the species as endangered on the IUCN Red List.[1] In 2019, the species was downgraded to least concern because of its greatly increased population size.[1]

Each year, the National Oceanic and Atmospheric Administration (NOAA) estimates current population levels for a variety of aquatic species of special interest, and releases an annual report showing the progress being made to reduce harvesting of overfished species. When a species has been determined to be either overfished or subject to overfishing, the regional fishery management councils are required to develop a plan to correct the problem. In 2006, NOAA published a press release stating that as a result of conservation efforts, between 2004 and 2005, monitored stocks of the barndoor skate had grown to a level that the NOAA no longer considers "overfished".[13]

Taxonomy and naming

The fish was originally described as Raja laevis by

scientific name was later changed to the currently valid name Dipturus laevis. It has also been misidentified as Raia granulata by Theodore Gill, an American ichthyologist, in 1879.[14] The genus name, Dipturus, is derived from the Greek words di, meaning two, and pteryx, meaning wing. Raja, the original genus which was coined by Carl Linnaeus in 1758, is still recognized as a valid subgenus.[3]

See also

References

  1. ^ . Retrieved 18 November 2021.
  2. ^ a b c d Basta, J. (2002). "Dipturus laevis". Animal Diversity Web. Retrieved 28 December 2009.
  3. ^ a b c d e f g h i Wettstein, M.J. "Biological Profiles: Barndoor Skate". Florida Museum of Natural History, Ichthyology Department. Retrieved 28 December 2009.
  4. ^ Bigelow, H.B.; W.C. Schroeder (1953). "Sawfishes, guitarfishes, skates and rays.". In J. Tee-Van; et al. (eds.). Fishes of the western North Atlantic. Part two. New Haven: Sears Found. Mar. Res., Yale Univ.
  5. ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2006). "Dipturus laevis" in FishBase. June 2006 version.
  6. ^ a b Bigelow, H.B.; W.C. Schroeder (1954). "Deep water elasmobranchs and chimeroids from the northwestern Atlantic slope". Bull. Mus. Comp. Zool. 112: 38–87.
  7. ^ McEachran, J.D.; J.A. Musick (1975). "Distribution and relative abundance of seven species of skates (Pisces: Rajidae) which occur between Nova Scotia and Cape Hatteras". Fishery Bulletin. 73: 110–136.
  8. ^ a b Packer D.; Zetlin, C. & Vitaliano J. (2003). "Essential Fish Habitat Source Document: Barndoor Skate, Dipturus laevis, Life History and Habitat Characteristics" (PDF). National Marine Fisheries Service, NOAA Technical Memorandum NMFS-NE-173. Retrieved 28 December 2009. {{cite journal}}: Cite journal requires |journal= (help)
  9. ^ Northeast Fisheries Science Center (2000). "Report of the 30th Northeast Regional Stock Assessment Workshop (30th SAW): Stock Assessment Review Committee (SARC) consensus summary of assessments". Northeast Fish. Sci. Cent. Ref. Doc. 00-03. {{cite journal}}: Cite journal requires |journal= (help)
  10. ^ NEFSC (2009). "Data poor working group, skate assessment figures". NEFSC. Archived from the original on 14 December 2012. Retrieved 12 April 2011.
  11. PMID 9685260
    .
  12. ^ NOAA. "endangered species ruling" (PDF). NOAA. Retrieved 12 April 2012.
  13. ^ "NOAA Releases Report on Status of U.S. Marine Fisheries for 2005" (Press release). National Oceanic and Atmospheric Administration. June 20, 2006. Archived from the original on 14 June 2010. Retrieved 28 December 2009.
  14. ^ Goode, G. B.; Bean, T. H. (1879). "List of the Fishes of Essex County, Massachusetts, including those of Massachusetts Bay". Bull. Essex Inst.: 28.

"Dipturus laevis". Integrated Taxonomic Information System. Retrieved 14 November 2006.

External links