Blue skate

Last updated

Blue skate
FMIB 50423 White Ray (Raia betis).jpeg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Rajiformes
Family: Rajidae
Genus: Dipturus
Species:
D. batis
Binomial name
Dipturus batis
Synonyms [2]
  • Raja batisLinnaeus, 1758
  • Raja macrorynchus Rafinesque, 1810
  • Propterygia hyposticta Otto, 1821
  • Raja flossada Risso, 1827
  • Raia gaimardi Gaimard, 1851
  • Batis vulgaris Couch, 1862

The blue skate (Dipturus batis), also known as the grey skate or blue-grey skate, is a species of cartilaginous fish, a ray, belonging to the family Rajidae, the skates. It was formerly considered to be conspecific with the flapper skate (D. batis), the combined taxon being known as the common skate. [3] [4] Historically, it was one of the most abundant skates in the northeast Atlantic Ocean and the Mediterranean Sea. Despite its name, today it appears to be absent from much of this range. [5] Where previously abundant, fisheries directly targeted this skate and elsewhere it is caught incidentally as bycatch. The former species was uplisted to critically endangered on the IUCN Red List in 2006 [1] and it is protected within the EU. [6]

Contents

Research published in 2009 and 2010 showed that the common skate should be split into two, the smaller southern D. cf. flossada (blue skate), and the larger northern D. cf. intermedius (flapper skate). [4] [7] [8] [9] Under this taxonomic arrangement, the name D. batis is recommended to be discarded. [9] [10] Currently, the scientific name D. batis (with flossada as a synonym) is retained for the blue skate and D. intermedius for the flapper skate. [11]

Taxonomy

The blue skate was first formally described as Raja batis in the 10th edition of Systema Naturae by Carl Linnaeus published in 1758 with its type locality given as "European Seas, locations being given as England and Lesbos. [12] In 1810 Constantine Samuel Rafinesque proposed a new subgenus of Raja which he called Dipturus with R. batis as its only species, the blue skate is the type species of Dipturus by monotypy. [13] The genus Dpturus belongs to the family Rajidae which is classified within the order Rajiformes. [14]

Distinct genetic and morphological differences exist within the common skate as traditionally defined, leading to the recommendation of splitting it into two species: The smaller (up to about 1.45 m or 4.8 ft in length) southern D. cf. flossada (blue skate), and the larger and slower-growing northern D. cf. intermedius (flapper skate). [4] [7] [8] [9] [15] Under this taxonomic arrangement, the name D. batis is discarded. [9] [10] Alternatively, the scientific name D. batis (with flossada as a synonym) is retained for the blue skate and D. intermedius for the flapper skate. [11] A formal request of preserving the name D. batis (with flossada as a synonym) for the blue skate has been submitted to the International Commission on Zoological Nomenclature, but as of 2017 a decision is still pending. [16]

Based on molecular phylogenetics, D. cf. intermedius is very close to D. oxyrinchus , while the relationship to D. cf. flossada is more distant. [4] [9] [17]

D. cf. intermedius has dark olive-green eyes and the blotch on each wing consists of a group of pale spots. [9] [15] [18] D. cf. flossada has pale yellow eyes, and the blotch on each wing is relatively large, roughly round, dark and with a pale ring around it. [9] [15] [18] Additional differences between the two are found in the thorns on their tails and other morphometric features. [9] [18] Both are found around the British Isles, and their ranges broadly overlap in the seas around this archipelago, but D. cf. intermedius is the most frequent species in the northern half (off Scotland and Northern Ireland), and D. cf. flossada is the most frequent in the southwest (Celtic Sea) and at Rockall. [4] [19] The primary—possibly only—species in Ireland is D. cf. flossada based mainly on the ICES International Bottom Trawl Survey and zoological specimens, [19] the species off Norway is D. cf. intermedius (no confirmed records of D. cf. flossada, but it might occur), [17] [20] and based on limited data the main in the North Sea, Skagerrak and Kattegat is D. cf. intermedius (although at least one record of D. cf. flossada in this region, off west Sweden, has been reported). [19] [21] Uncertainty exists about the exact species involved in the southern half of the range, but a preliminary morphological study indicates that the one in the Azores is D. cf. intermedius. [22]

Description

The blue skate can reach up to 1.43 m (4 ft 8 in) in length. [1] [23] Overall shape features a pointed snout and rhombic shape, with a row of spines or thorns along the tail. [24] The top surface is generally coloured olive-grey to brown, often with a pattern of spots, and the underside is lighter blue-grey. [2] It can be confused with several other skates in its range, such as D. nidarosiensis , D. oxyrinchus , and Rostroraja alba . [15]

Range, habitat, and ecology

The blue skate is native to the northeast Atlantic. [1] It is a bottom dwelling species mainly found at depths of 100–200m, [2] but it can occur as shallow as 30m [4] and as deep as 1000m. [2] Now, their population and range are severely depleted and fragmented, with disappearances being reported on several places. [1] [25] This species is found in northeastern Atlantic from Norway and Iceland to Senegal. [2] Its presence in the Mediterranean Sea is questionable since earlier records could concern D. intermedius recently considered as a distinct species. [26]

Growth and reproduction

The blue skate can reach an estimated age of 50–100 years [15] and maturity is reached when about 11 years old. [1] The size where they reach maturity depend on sex and population. In D. cf. flossada (blue skate) males reach maturity when about 1.15 m (3 ft 9 in) long and females when about 1.23 m (4 ft 0 in) long. [18] In D. cf. intermedia (flapper skate), males reach maturity when about 1.86 m (6 ft 1 in) long and females when about 1.98 m (6 ft 6 in) long. [18] The sex ratio is 1:1, but this can vary depending on geography and season. When hatching, juveniles measure up to 22.3 cm (8+3⁄4 in) long. [1] Once they have reached sexual maturity, they reproduce only every other year. They mate in the spring, and during the summer, females lay about 40 egg cases in sandy or muddy flats. The eggs develop for 2–5 months before hatching. [15]

Egg case

Egg cases measure up to 25 cm (10 in) long, excluding the horns, and 15 cm (6 in) wide. They are covered in close-felted fibers and often wash up on the shore. [15]

Egg case hunts have been done throughout the general distribution of the common skate. In the British Isles, egg cases were found only in northern Scotland and the north of Ireland. In the 19th and 20th centuries, egg cases were seen along the entire British coastline in high numbers, but now they are found only in a few areas. [27]

Diet

Like other skates, the blue skate is a bottom feeder. Its diet consists of crustaceans, clams, oysters, snails, bristle worms, cephalopods, and small to medium-sized fish (such as sand eel, flatfish, monkfish, catsharks, spurdog, and other skates). [15] [28] [29] The size of the individual can affect its diet. Larger ones eat larger things like fish. [2] The bigger the skate is, the more food will be needed to sustain its large body size. The activity level determines how much it eats; the more active it is, the more it eats. [30] The blue skate does not feed only on creatures at the bottom of the ocean, as some do ascend to feed on mackerel, herring, and other pelagic fish, [31] which are caught by rapidly moving up from the seabed to grab the prey. [15]

Threatened status

The blue skate is listed as a critically endangered species by the IUCN and it is threatened both in the Atlantic Ocean and Mediterranean Sea. [1] The blue skate's population has drastically decreased because of overfishing and it likely will disappear entirely unless more is done to preserve it. [25] It has both been targeted directly and caught incidentally as bycatch. [1] Due to the profitability of trawl fishing, bycatch likely will remain a serious problem for the blue skate. [1] The species is extirpated in the Baltic Sea. [32] Remaining strongholds where it remains locally common are off western Scotland and in the Celtic Sea. [4] [16] A stronghold along the coast of Norway has been suggested, [4] but recent studies indicate the species is rare there and many previous records are the result of misidentifications of other skates. [17] [20]

Because the blue skate is long-lived and slow to mature, it may be slow to repopulate, [33] but experience with the related barndoor skate (D. laevis) of the northwest Atlantic indicates that a population recovery may be possible in a relatively short time. [34] The blue skate is strictly protected within the EU, making it illegal for commercial fishers to actively fish for it or keep it if accidentally landed. [6] Like other elasmobranchs, it is believed to have a good chance of surviving if released after being caught. [15]

Related Research Articles

<span class="mw-page-title-main">Skate (fish)</span> Family of fishes

Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. More than 150 species have been described, in 17 genera. Softnose skates and pygmy skates were previously treated as subfamilies of Rajidae, but are now considered as distinct families. Alternatively, the name "skate" is used to refer to the entire order of Rajiformes.

<span class="mw-page-title-main">Rajiformes</span> Order of fishes in the superorder Batoidea

Rajiformes is one of the four orders in the clade Batomorphi, often referred to as the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the head and the gill slits are on the underside of the body. Most species give birth to live young, although some lay eggs enclosed in a horny capsule.

<span class="mw-page-title-main">New Zealand smooth skate</span> Species of cartilaginous fish

The New Zealand smooth skate is a skate of the genus Dipturus, found around New Zealand at depths between 15 and 1,300 m.

<i>Dipturus</i> Genus of cartilaginous fishes

Dipturus is a large genus of skates native to the Pacific, Atlantic, and Indian Oceans. They were formerly included in Raja. Some species initially moved to Dipturus were later placed in Dentiraja, Spiniraja, and Zearaja.

<i>Raja</i> (fish) Genus of cartilaginous fishes

Raja, also known as Raia, is a genus of skates in the family Rajidae containing 16 species. Formerly a wastebasket genus, many species historically categorized here have been moved to other genera in the family, such as Amblyraja, Beringraja, Dipturus, Leucoraja and Rostroraja. Raja are flat-bodied, cartilaginous fish with a rhombic shapes due to their large pectoral fins extending from or near from the snouts to the bases of their tails. Their sharp snouts are produced by a cranial projection of rostral cartilage. The mouth and gills are located on the underside of the body. They may be either solid-coloured or patterned, and most skates have spiny or thornlike structures on the upper surface, while some species contain weak electrical organs within their tails. Mating typically occurs in the spring and the female lays numerous eggs per clutch which are encapsulated in leathery cases, commonly known as "mermaid’s purses". Species vary in size, ranging from about 40 to 140 cm (1.3–4.6 ft) in length. These bottom-dwellers are active during both day and night, and typically feed on molluscs, crustaceans and fish. Raja skates are found in the East Atlantic, also in the Mediterranean, and western Indian Ocean, ranging from relatively shallow water to a depth of 800 m (2,600 ft). Skates and related species have fossil records dating from the Upper Cretaceous period, thus this well-adapted species is quite ancient.

<span class="mw-page-title-main">Barndoor skate</span> Species of cartilaginous fish

The barndoor skate is a species of marine cartilaginous fish in the skate family Rajidae of the order Rajiformes. It is native to the northwestern Atlantic Ocean, and is found from the Grand Banks of Newfoundland and the southern side of the Gulf of St. Lawrence south to North Carolina. The fish is one of the largest skates found in the 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.

<span class="mw-page-title-main">Argus skate</span> Species of fish

The argus skate is a species of fish in the family Rajidae. This small, up to 38 cm (1.25 ft) long, skate is endemic to depths of 135–320 m (443–1,050 ft) in the oceans off northeast Australia. It was formerly included in Dipturus or Raja.

<span class="mw-page-title-main">Thornback ray</span> Species of cartilaginous fish

The thornback ray, or thornback skate, is a species of ray fish in the family Rajidae.

<span class="mw-page-title-main">Smalleyed ray</span> Species of cartilaginous fish

The smalleyed ray or smalleyed skate is a species of ray in the family Rajidae, the typical rays and skates, from the eastern Atlantic Ocean where it is found in tidal, coastal waters with sandy substrates.

<span class="mw-page-title-main">Batomorphi</span> Superorder of cartilaginous fishes

Batomorphi is a clade of cartilaginous fishes, commonly known as rays, this taxon is also known as the superorder Batoidea, but the 5th edition of Fishes of the World classifies it as the division Batomorphi. They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.

<span class="mw-page-title-main">Mottled skate</span> Species of cartilaginous fish

The mottled skate is a species of skate in the family Rajidae. An inhabitant of shallow coastal waters, it is found in the northwestern Pacific Ocean off Korea, Japan, and China. This species grows to 1.12 m (3.7 ft) long and has a diamond-shaped pectoral fin disc with a long snout. It is characterized by a covering of prickles above and below its snout, but not elsewhere on its body, and a dark ring in the middle of each "wing".

<span class="mw-page-title-main">Clearnose skate</span> Species of cartilaginous fish

The clearnose skate is a species of cartilaginous fish in the family Rajidae. R. eglanteria is also known by other common names such as the brier skate and summer skate. Clearnose skates are easily identified by the translucent patches on either side of their snouts and their mottled dorsal surface. They are found along the Atlantic and Gulf coasts of the United States in shallow waters of the continental shelf.

<span class="mw-page-title-main">Graytail skate</span> Species of cartilaginous fish

The graytail skate, or gray tail skate, is a large species of skate in the family Arhynchobatidae, native to the south-western Atlantic Ocean and south-eastern Pacific Ocean. It is listed as endangered by the IUCN. It was caught as part of a commercial fishery around the Falkland Islands and is a bycatch in several other fisheries.

<i>Dipturus nidarosiensis</i> Species of cartilaginous fish

The Norwegian skate, or black skate, is a species of skate found at depths of 200 m (660 ft) to over 1,600 m (5,200 ft) in the East Atlantic region. Initially its range was believed to be restricted to the Norwegian Sea and North Sea to the Bay of Biscay. It is occasionally encountered off the western coast of Ireland, and historically has been found near Rockall and in the Norwegian Deep, though recent surveys have not identified the species there. The species has frequently been confused with other skates, and since the late 1980s it has been confirmed to occur more widely, ranging from Iceland to Morocco, as well as off South Africa and in the Mediterranean Sea.

Dipturus teevani, commonly known as the prickly brown ray or Caribbean skate, is a species of cartilaginous fish in the family Rajidae. The prickly brown ray is medium in size compared to other skates, and is known from a patchy, deep-water distribution in the western Atlantic Ocean.

<i>Caliraja rhina</i> Species of cartilaginous fish

Caliraja rhina, commonly known as the longnose skate, is a species of skate in the family Rajidae from the northeast Pacific. It is found from the eastern Bering Sea and Alaska to Baja California and the Gulf of California. The longnose skate is found at depths of 9–1,069 m (30–3,507 ft) and often deeper than the big skate. The longnose skate was briefly associated with the genus Beringraja, having been previously included in Raja until genetic evidence supported reclassification. It was then reclassified into the new Caliraja genus after an analysis of egg case morphology and the number of embryos per egg case. This issue has not be completely resolved and the scientific names "Raja rhina" and "Beringraja rhina" are still in widespread use.

<span class="mw-page-title-main">Flapper skate</span> Species of cartilaginous fish

The flapper skate is a species of cartilaginous fish, a ray, belonging to the family Rajidae, the skates. It was formerly considered to be conspecific with the blue skate, the combined taxon being known as the common skate. The flapper skate is found in the Eastern Atlantic Ocean, although its range has contracted to a considerable extent due to overfishing, and it is classified by the International Union for Conservation of Nature as Critically Endangered. It is the largest species of skate in the World.

<i>Dipturus oxyrinchus</i> Species of fish

Dipturus oxyrinchus, commonly known as the longnose skate, is a species of skate in the family Rajidae. It is up to 1.5 m (4.9 ft) m in length. The species is found in eastern Atlantic Ocean and in the Mediterranean Sea.

<span class="mw-page-title-main">Sydney skate</span> Species of cartilaginous fish

The Sydney skate is a species of skate of the family Rajidae native to waters off the east coast of Australia.

<span class="mw-page-title-main">Blonde ray</span> Species of cartilaginous fish

The blonde ray or blonde skate is a species of ray fish in the family Rajidae.

References

  1. 1 2 3 4 5 6 7 8 9 10 Ellis, J.R.; McCully-Philips, S.R.; Sims, D.; Derrick, D.; Cheok, J.; Dulvy, N.K. (2024) [amended version of 2021 assessment]. "Dipturus batis". IUCN Red List of Threatened Species . 2024: e.T203364219A256580832. doi: 10.2305/IUCN.UK.2024-1.RLTS.T203364219A256580832.en .
  2. 1 2 3 4 5 6 Froese, Rainer; Pauly, Daniel (eds.). "Dipturus batis". FishBase . June 2024 version.
  3. ↑ Florida Museum of Natural History. "Ray and Skate: Basic Questions" . Retrieved 29 October 2007.
  4. 1 2 3 4 5 6 7 8 Griffiths AM; Sims DW; Cotterell SJ; et al. (2010). "Molecular markers reveal spatially-segregated cryptic species in a critically endangered fish, the common skate Dipturus batis". Proceedings of the Royal Society of London B. 277: 1497–1503. doi:10.1098/rspb.2009.2111. PMC   2871835 .
  5. ↑ Brander, K. (1981). "Disappearance of common skate Raja batis from Irish Sea". Nature. 290 (5801): 48–49. Bibcode:1981Natur.290...48B. doi:10.1038/290048a0. S2CID   4349670.
  6. 1 2 ICES (11 October 2016)5.3.12 Common skate (Dipturus batis-complex (blue skate (Dipturus batis) and flapper skate (Dipturus cf. intermedia)) in subareas 6–7 (excluding Division 7.d) (Celtic Seas and western English Channel) Archived 18 January 2017 at the Wayback Machine . ICES Advice 2016, Book 5.
  7. 1 2 Is 80-Year-Old Mistake Leading to First Species to Be Fished to Extinction?, ScienceDaily 17 November 2009
  8. 1 2 "Skate may be fished to extinction". BBC News.
  9. 1 2 3 4 5 6 7 8 Iglesias SP, Toulhoat L, Sellos DY. 2009. Taxonomic confusion and market mislabelling of threatened skates: important consequences for their conservation status. Aquatic Conservation: Marine and Freshwater Ecosystems 20: 319–333.
  10. 1 2 White W.T. and P.R. Last. 2012. A review of the taxonomy of chondrichthyan fishes: a modern perspective. Journal of Fish Biology 80: 901–917.
  11. 1 2 Last, P.R.; Weigman, S.; Yang, L. (2016). "Changes to the nomenclature of the skates (Chondrichthyes: Rajiformes)". In Last, P.R.; Yearsley, G.R. (eds.). Rays of the World: Supplementary Information. CSIRO Special Publication. pp. 11–34. ISBN   9781486308019.
  12. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species in the genus Dipturus". Catalog of Fishes . California Academy of Sciences . Retrieved 2 November 2024.
  13. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Genera in the family Rajidae". Catalog of Fishes . California Academy of Sciences . Retrieved 2 November 2024.
  14. ↑ "Eschmeyer's Catalog of Fishes Classification". California Academy of Sciences . Retrieved 2 November 2024.
  15. 1 2 3 4 5 6 7 8 9 10 "Common skate : Dipturus batis" (PDF). Sharktrust.org. Archived from the original (PDF) on 8 April 2016. Retrieved 16 January 2017.
  16. 1 2 ICES (2017). WGEF Report . Retrieved 31 December 2017.
  17. 1 2 3 Lynghammar, A.; J.S. Christiansen; A.M. Griffiths; S.-E. Fevolden; H. Hop; T. Bakken (2014). "DNA barcoding of the northern Northeast Atlantic skates (Chondrichthyes, Rajiformes), with remarks on the widely distributed starry ray". Zoologica Scripta. 43 (5): 485–495. doi:10.1111/zsc.12064. hdl: 11250/2468480 . S2CID   84319635.
  18. 1 2 3 4 5 ICES (October 2012). European Commission special request on spatial distribution, stock status, and advice on Dipturus species . Retrieved 31 December 2017.
  19. 1 2 3 ICES (October 2012). Rays and Skates in the Celtic Sea . Retrieved 31 December 2017.
  20. 1 2 "Dipturus batis (Linnaeus, 1758)" (in Norwegian). Norsk Rødliste [Norwegian Red List]. Retrieved 31 December 2017.
  21. ↑ ICES (9 October 2015). Common skate (Dipturus batis-complex) in Subarea IV and Division IIIa (North Sea, Skagerrak, and Kattegat) . Retrieved 31 December 2017.
  22. ↑ Das, D.; P. Afonso (6 November 2017). "Review of the Diversity, Ecology, and Conservation of Elasmobranchs in the Azores Region, Mid-North Atlantic". Front. Mar. Sci. 4: 354: 1–19. doi: 10.3389/fmars.2017.00354 .
  23. ↑ Muus, B.; J.G. Nielsen; P. Dahlstrom; B. Nystrom (1999). Sea Fish. Scandinavian Fishing Year Book. pp. 68–69. ISBN   8790787005.
  24. ↑ ARKive. "Common skate – Dipturus batis". Archived from the original on 5 April 2007. Retrieved 29 October 2007.
  25. 1 2 "Background Document for Common skate : Dipturus batis" (PDF). Qsr2010.ospar.org. Retrieved 16 January 2017.
  26. ↑ Guide of Mediterranean Skates and Rays (Dipturus batis). Oct. 2022. Mendez L., Bacquet A. and F. Briand.http://www.ciesm.org/Guide/skatesandrays/questionable-species/
  27. ↑ "The Shark Trust – Common/Flapper Skate". Sharktrust.org. Archived from the original on 29 October 2013. Retrieved 16 January 2017.
  28. ↑ "The Benthic Zone: The Sea Floor". Brighthub.com. 23 December 2009. Retrieved 23 October 2013.
  29. ↑ "BIOTIC Species Information for Dipturus batis". Marlin.ac.uk. Retrieved 23 October 2013.
  30. ↑ Wearmouth, Victoria J.; Sims, David W. (2009). "Movement and behaviour patterns of the critically endangered common skate Dipturus batis revealed by electronic tagging". Journal of Experimental Marine Biology and Ecology. 380 (1–2): 77–87. doi:10.1016/j.jembe.2009.07.035.
  31. ↑ "Common Skate". Uk-fish.info. Retrieved 16 January 2017.
  32. ↑ HELCOM (2013). "HELCOM Red List of Baltic Sea species in danger of becoming extinct" (PDF). Baltic Sea Environmental Proceedings (140): 72. Archived from the original (PDF) on 7 October 2014. Retrieved 30 July 2014.
  33. ↑ "Descriptions and articles about the Blue Skate (Dipturus batis) – Encyclopedia of Life". Encyclopedia of Life.
  34. ↑ Neat; Pinto; Burrett; Cowie; Travis; Thorburn; Gibb; Wright (2014). "Site fidelity, survival and conservation options for the threatened flapper skate (Dipturus cf. intermedia)". Aquatic Conservation. 25 (1): 6–20. doi:10.1002/aqc.2472.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.