Graytail skate

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Graytail skate
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Rajiformes
Family: Arhynchobatidae
Genus: Bathyraja
Species:
B. griseocauda
Binomial name
Bathyraja griseocauda
(Norman, 1937)
Greytail-skate-rangemap.png
Synonyms
  • Raja griseocaudaNorman, 1937

The graytail skate (Bathyraja griseocauda), 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. [1] It was caught as part of a commercial fishery around the Falkland Islands [2] and is a bycatch in several other fisheries.

Contents

Range and distribution

In the Atlantic Ocean, the graytail skate is found off the coast of Argentina and in the waters surrounding the Falkland Islands. The northern extent of its range in the Atlantic is 37 degrees South. [1] Its range extends very slightly past Cape Horn into the Pacific Ocean, off the coast of Chile, [3] but does not extend beyond a northern extent of 41 degrees South. [1]

Although graytail skates have been found in waters as shallow as 51 metres (167 ft), [4] they are most often found deeper than 250 metres (820 ft). They are found all over the continental shelf surrounding the Falkland Islands, but are found in highest concentration in the western, deeper shelf margin. [5]

Individuals also segregate spatially by age class. Nursery grounds near the Falkland Islands are generally located at depths of 300-350m. Juveniles are found in deeper water, 400 to 600 metres (1,300 to 2,000 ft), but migrate either to the upper slope (200 to 400 metres (660 to 1,310 ft)) or into deeper water (below 600 metres (2,000 ft)) after growing to 40 to 45 centimetres (16 to 18 in) in length. [5]

The current population size of the graytail skate is not known. [1] However the catch per unit effort has declined from 1993-2001, [2] as well as a decrease in size. [1] These indicators led to the partial closure of the fishery around the Falklands, although no assessments have been completed to gauge current status. The frequency of bycatch and slow growth rate have led fisheries scientists to believe the fisheries restriction has not reversed the decline. [1]

Biology and description

Recent reports indicate the graytail skate grows to a length of approximately 130 centimetres (51 in), with a maximum reported length of 157 centimetres (62 in). The disc width is generally less than the total length, growing to a maximum width of approximately 90 centimetres (35 in). [5] An earlier study found mature individuals to be considerably smaller. [6] The dorsal surface is black-brown and is covered by denticles but lacks spines. The ventral surface is yellowish with dark spots near the tail. The tail has 19-27 large spines. [6]

The graytail skate is a slow-growing species, [1] growing 4 to 6 centimetres (1.6 to 2.4 in) per year. [5] This is slower than most species in the genus Bathyraja. [1] The maximum observed age is 28 years. Sexual maturity is reached at approximately 18 years for females and 14 years for males. [5] The sex ratio is slightly skewed toward female. [5]

Like most skates, the graytail skate is oviparious, laying paired eggs with horn-like projections. [4] It spawns year-round, although lays fewer eggs in the winter. [5]

Younger individuals eat primarily amphipods and other crustaceans and polychaete worms. These disappear from the diet as the individual ages. Older individuals eat rajids, ray-finned fish, and cephalopods. [7]

Taxonomy

Initially classified in the genus Raja , the graytail skate was reclassified as Bathyraja in 1971, a genus which did not exist in 1947. [6] This classification was supported by a morphological phylogenetic analysis [8] and genetically. It is closely related to the butterfly skate, Bathyraja papilionifera, based on similarity of mtDNA fragments from Cytochrome c oxidase subunit I. [9]

Fisheries

The graytail skate was the largest component of the rajid catch in the Falkland Island from 1993 to 2001. It comprised 24.2% of the harvest, followed by the white-dotted skate, B. albomaculata, and the broadnose skate, B. brachyurops. [2] It is also a bycatch in trawler fisheries targeting teleosts, and long line fisheries targeting patagonian toothfish. [1] Fisheries may be based in the Falkland Islands, Argentina, or Chile.

Management

The Falkland Islands instituted a management plan in 1994. The plan identifies two mix-species fisheries, one north and one south of the Falklands. Fishing for rajids in the north requires a license, while it has been prohibited in the south since 1996. As of 2005, Argentina had not instituted an elasmobranch management plan. [10]

Related Research Articles

<i>Bathyraja</i> Genus of fishes

Bathyraja is a large genus of skates in the family Arhynchobatidae.

<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">Spotback skate</span> Species of fish

The spotback skate is a species of fish in the family Arhynchobatidae. It is found off the Atlantic coasts of Argentina, Brazil, and Uruguay where its natural habitat is over the continental shelf in the open sea. It is a large fish, growing to over a metre in length. It feeds mainly on other fish according to availability, with shrimps, octopuses and other invertebrates also being eaten. Reproduction takes place throughout most of the year, with the eggs being laid in capsules that adhere to the seabed. The spotback skate is the subject of a fishery and is thought to be overfished, resulting in Greenpeace adding the fish to its red list of fish to be avoided, and the International Union for Conservation of Nature listing it as an "endangered species".

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

The big skate is the largest species of skate in the waters off North America. They are found along the Pacific Coast from Alaska to Baja California, typically from the intertidal zone to a depth of 120 m (390 ft), and feed on benthic invertebrates and small fishes. They are unusual among skates in that their egg cases may contain up to seven eggs each. This species is one of the most commercially important skates off California and is sold for food.

<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.

Thymops birsteini, the Patagonian lobsterette, is a species of lobster found around the coasts of South America, particularly the South Atlantic. It belongs to the monotypic genus Thymops.

<i>Bathyraja mariposa</i> Species of cartilaginous fish

Bathyraja mariposa, sometimes referred to as the butterfly skate, is a species of skate found in the Aleutian islands. It is overall a medium-brown color, lacks thorns on the disc and has indistinct thorns on the tail. It was discovered in 2002 during a National Marine Fisheries Service survey, and first described in 2004. The holotype specimen is held at the University of Washington. Its species name "mariposa" derives from the Spanish word for butterfly, although several other species are sometimes referred to as the "butterfly skate."

Broadnose skate is a species of skate in the family Arhynchobatidae. This fish occurs on 28 to 604 meters, mostly at depths shallower than 250 meters, from Valdivia and Estrecho de Magallanes to Argentina and the Falkland Islands. It has the maximum total length of about 125 centimetres (49 in) which it reaches in about 20 years. Both sexes reach maturity at age 8–10 years.

<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">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">Grey skate</span> Species of cartilaginous fish

The grey skate is a species of fish in the family Rajidae. It was described in 2008 by Australian ichthyologist Peter R. Last.

<i>Patagonotothen ramsayi</i> Species of ray-finned fish

Patagonotothen ramsayi, the longtail southern cod, rock cod, marujo or Notothenia, is a benthopelagic species of marine ray-finned fish of the family Nototheniidae, the notothens or the cod icefishes, native to the Patagonian Shelf in the southwest Atlantic, where it is the most abundant notothen species found, dominating among medium-sized demersal fishes in the area, and is a commercially important species.

<i>Rajella fyllae</i> Species of ray fish

Rajella fyllae is a species of skate in the family Rajidae.

Bathyraja andriashevi, the little-eyed skate, is a species of skate in the family Arhynchobatidae found in the western Pacific Ocean.

Bathyraja bergi, the bottom skate, is a species of skate in the family Arhynchobatidae found in the north-western Pacific Ocean.

Bathyraja taranetzi, the mud skate, is a species of skate in the family Arhynchobatidae found in the north-western Pacific Ocean.

Bathyraja tzinovskii, the creamback skate, is a species of skate in the family Arhynchobatidae found in the western Pacific Ocean.

Bathyraja matsubarai, the dusky-purple skate, is a species of skate in the family Arhynchobatidae found in the north-western Pacific Ocean.

Bathyraja cousseauae, also known as Cousseau's skate or the joined-fins skate is a species of skate within the genus Bathyraja. The species is found in the Southwest Atlantic Ocean.

Okamejei panayensis is a demersal fish belonging to the skate family, occurring in nearshore temperate environments and deep-water tropical and boreal regions.

References

  1. 1 2 3 4 5 6 7 8 9 10 Pollom, R.; Dulvy, N.K.; Acuña, E.; Bustamante, C.; Chiaramonte, G.E.; Cuevas, J.M.; Herman, K.; Paesch, L.; Pompert, J.; Velez-Zuazo, X. (2020). "Bathyraja griseocauda". IUCN Red List of Threatened Species . 2020: e.T63113A124459226. doi: 10.2305/IUCN.UK.2020-3.RLTS.T63113A124459226.en . Retrieved 18 July 2024.
  2. 1 2 3 Wakeford, R.C. (2004). "Management of the Falkland Islands Multispecies Ray Fishery: Is Species-specific Management Required?" (PDF). Journal of Northwest Atlantic Fishery Science. 35. D. J. Agnew, D. A. J. Middleton, J. H. W. Pompert and V. V. Laptikhovsky: 309–324. doi: 10.2960/J.v35.m497 . Archived from the original (PDF) on 16 March 2014. Retrieved 13 March 2012.
  3. ↑ Saez, S.; Lamilla, J. (2004). "Sexual homodonty in Bathyraja griseocauda (Norman 1937) from the Southern Eastern Pacific (Chile) (Chondrichthyes, Rajidae: Arhynchobatinae)". Journal of Applied Ichthyology. 20 (3): 189–193. doi: 10.1111/j.1439-0426.2004.00516.x .
  4. 1 2 Froese, Rainer; Pauly, Daniel (eds.) (2012). "Bathyraja griseocauda" in FishBase . March 2012 version.
  5. 1 2 3 4 5 6 7 Arkhipkin, A.I. (2008). "Biology of the skates Bathyraja brachyurops and B. griseocauda in waters around the Falkland Islands, Southwest Atlantic". ICES Journal of Marine Science. 20 (4). N. Baumgartner, P. Brickle, V.V. Laptikhovsky, J.H.W. Pompert, and Z.N. Shcherbich: 189–193. doi:10.1093/icesjms/fsn015.
  6. 1 2 3 Llano, G.A.; Wallen, I.E. (1971). Biology of the Antarctic Seas IV. Antarctic Fisheries Series, vol 17. American Geophysical Union: Washington D.C.
  7. ↑ Brickle, P.; V. Laptikhovsky; J. Pompert; A. Bishop (2003). "Ontogenetic changes in the feeding habits and dietary overlap between three abundant rajid species on the Falkland Islands' shelf". Journal of the Marine Biological Association of the United Kingdom. 83 (5): 1119–1125. doi:10.1017/s0025315403008373h. S2CID   84601955.
  8. ↑ McEachrun, J.D.; Dunn, K.A. (1998). "Phylogenetic Analysis of Skates, a Morphologically Conservative Clade of Elasmobranchs (Chondrichthyes: Rajidae)". Copeia. 1998 (2): 271–290. doi:10.2307/1447424. JSTOR   1447424.
  9. ↑ Mabragana, E. (2011). "DNA Barcoding Identifies Argentine Fishes from Marine and Brackish Waters". PLOS ONE. 6 (12). J. Martın Dıaz de Astarloa, R. Hanner, J. Zhang, and M. Gonzalez Castro: e28655. Bibcode:2011PLoSO...628655M. doi: 10.1371/journal.pone.0028655 . PMC   3235135 . PMID   22174860.
  10. ↑ Fowler, S.L. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. R.D. Cavanagh, M. Camhi, G.H. Burgess, G.M. Cailliet, S.V. Fordham, C.A. Simpfendorfer, and J.A. Musick. IUCN – The World Conservation Union.
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