Common eagle ray

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Common eagle ray
Temporal range: 2.588–Present  Ma
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Myliobatis aquila.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family: Myliobatidae
Genus: Myliobatis
Species:
M. aquila
Binomial name
Myliobatis aquila
Synonyms [2]
  • Leiobatus aquila(Linnaeus, 1758)
  • Myliobatis cervusSmith, 1935
  • Myliobatis equila(Linnaeus, 1758)
  • Myliobatis noctulaBonaparte, 1833
  • Myliobatus aquila(Linnaeus, 1758)
  • Raia rhombusLarrañaga, 1923
  • Raja aquilaLinnaeus, 1758

The common eagle ray or bullray (Myliobatis aquila) is a species of fish in the family Myliobatidae. It inhabits the eastern Atlantic Ocean (North Sea to South Africa), the Mediterranean Sea and the south-western Indian Ocean. [1]

Contents

Description

The common eagle ray reaches up to 183 cm (6.0 ft) in total length [3] and has a disc width up to 80 cm (2.6 ft). [4] Most specimens are, however, smaller. [5] Females grow to be larger than males. [6] The dorsal surface is brown or black while the ventral surface is white. It has a rhomboidal disc with a pair of large, triangular pectoral fins projecting on either side, and a single dorsal fin. [3] The blunt snout is rounded and the tail is long and slender, with a large spine at its base but no tail fin. [3] [5] On average, males have 72 spine serrations and females have 66 spine serrations. The spine makes about 70% of the male's length and 65% of the female's length. [7] The mid dorsal groove, which contains the glandular tissue necessary for venom injection, extends along 10–40% the tail. [7] [8] It has one or two excretory channels for the venom. [9]

Distribution and habitat

This species occurs in the eastern Atlantic Ocean, including the North Sea, from the British Isles to South Africa, extending to the Indian Ocean. It is also found in the Mediterranean Sea. [10] It occurs both close to the shore and further out, at depths down to about 800 m (2,600 ft), but much of its time is spent in shallower water at less than 50 m (160 ft). [1] It typically prefers more open sandy areas. [5] It has also been found in a semi-enclosed lagoon on Gran Canaria Island, particularly in winter (March to April) and summer (August to October), where it was founded to prefer rocky and mixed bottoms. [11]

Ecology

Feeding and diet

Benthic invertebrates form an important part of the common eagle ray's diet. [6] The species largely feeds on crustaceans and bivalve molluscs that it excavates from the seabed. Other items in its diet include polychaete worms, gastropod molluscs, sea pens and small fish. [10] Larger individuals consume more fish than smaller individuals. [6] Instead of having pointed teeth, it has flattened hexagonal bars and plates arranged in a mosaic pattern on its jaws; with these, it crushes the shells of its prey. [12]

Mollusks and teleost fish were found to be the most important food items for individuals living in the Sea of Marmara, although polychaetas and crustaceans were also frequently found amongst the stomach contents. [13] Calliostoma lusitanicum and Stramonita haemastoma are the most common prey species off the coast off the Azores. [14]

Reproduction and development

This species is known to gather in groups of dozens of individuals during the reproductive period. [15] Reproduction is oviviviparous. A clutch of three to seven young develop inside the mother, receiving nourishment at first from their egg yolks, but later from fluids secreted by their mother into her uterus. [3] The gestation period is 6–8 months long, after which the female gives birth to between three and seven live pups. [16] [17] The smallest juveniles were caught around France between May and September off the coast of France. [18] They still had a unhealed scar on the lower surface, suggesting they were neonates. A study conducted in South Africa in 1983 found juveniles in November. [19] Juveniles were also found at Gran Canaria Island in October. [11]

Female development

Juvenile females have whitish membranous ovaries and thread-like oviducts. The oviducal glands are inconspicuous. Sub-adults have white translucent follicles and a well differentiated genital duct. The oviducal glands are slightly rounded. Adult females captured in January and March off the coast of France were found to have developing oocytes in both ovaries. The uteri were thick and muscular. They contained uterine fluid, which is probably sectreted from the villi that cover the internal wall. Females caught in August and September in the same region had between eight and ten yolky oocytes of a similar size and mass. Both uteri were enlarged and contained uterine fluid. The villi were well-developed and formed the trophonemata, which plays an important role in stingray gestation. Fertilised eggs surrounded by a diaphanous and a yellowish capsule that tapered to a small filament at either end were found in a female captured in October. The ovary contained atretic oocytes. [18]

Male development

Juvenile males have thread-like testes and genital ducts. The orbits have a smooth surface. Sub-adult males have no externally visible spermatocysts on the testes or sperm in the seminal vesicles. The superior surface of the orbit has a conspicuous protrusion. Adult males have elongated calcified claspers that are larger than the pelvic fins. The testes are well developed with visible external spermatocysts, a twisted genital duct and sperm in the seminal vesicles. They have well-developed conical supra-orbital vesicles. [18]

Hermaphrotism

At least one hermaphroditic specimen has been recorded. This specimen was classified as an abnormal hermaphrodite - one which is unable to perform as a functioning male or female as the reproductive organs were underdeveloped. [20]

Parasites

Several parasites live in and on this species. These include Entobdella diadema on the skin and Monocotyle myliobatis in the gills. [21] [22]

Relationship with humans

While it does contain venom, this species is not considered to pose a risk to humans as stings typically don't have any strong effects. [3] [23]

Fishing

This species is sometimes caught as bycatch, including in the pelagic trawl fishery. Due to declining numbers, the levels of bycatch are not nearly as high as they were historically. [24] A study in the Adriatic Sea showed that, on average, the fisheries in the region catch one common eagle ray every 20 hauls. About 79% of these are released alive after capture. The frequency is impacted by the depth of trawling, the season and the area being trawled. Most individuals were caught between April and September in the more northern areas at depths of 20–40 m (66–131 ft). [25]

Tourism

This species has gained economic importance through underwater photographers and other SCUBA divers. [14]

Bioaccumulation

A study in the Mediterranean Sea examined the mercury and methylmercury (the most common organic mercury compound) concentrations in three cartilaginous fish species. The common eagle ray was found to have lower mercury concentrations (0.67-1.01 mg/kg) than Chimaera monstrosa or Torpedo nobiliana . This is likely due to its diet as both the other two species feed on higher trophic levels (compared to the invertebrates that make up this eagle ray's diet). It also had the lowest methylmercury concentration (an average of 72%). [26] This species does, however, appear to have higher levels of arsenic in its tissues than pelagic ray species. [27]

Status

The International Union for Conservation of Nature to rate it as "critically endangered". [1]

The taxonomic position of this fish is unclear as populations in the Mediterranean Sea may be a different species from those in the southeastern Atlantic. In the Gulf of Lion in the northwestern Mediterranean Sea, populations declined in the 1970s, and there and elsewhere in the Mediterranean, the fish is under threat from intensive fishing. [1] The population has also been declining in the Atlantic Ocean off the coast of Europe, where it was once one of the most common skate and ray bycatch species (which collectively made up a total of about a quarter of the total catch by mass in 1881). The species is now rare in the region. [24]

Along the coast of West Africa it is also the subject of artisanal fishing activities but these are less intensive and populations may be steady. [1]

Related Research Articles

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Myliobatis is a genus of eagle rays in the family Myliobatidae.

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

The New Zealand eagle ray or Australian eagle ray is an eagle ray of the family Myliobatidae, found in bays, estuaries, and near rocky reefs around New Zealand and southern Australia on the inner continental shelf. It is a common species and the International Union for Conservation of Nature has assessed its conservation status as being of "least concern".

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

Aetomylaeus bovinus, also known as the bull ray, duckbill ray, or duckbill eagle ray, is a species of large stingray of the family Myliobatidae found around the coasts of Europe and Africa.

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

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<span class="mw-page-title-main">Angular roughshark</span> Species of shark

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<span class="mw-page-title-main">Velvet belly lanternshark</span> Species of shark

The velvet belly lanternshark is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 20–2,490 m (66–8,169 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. The ventral photophores are thought to function in counter-illumination, which camouflages the shark against predators and prey. The bioluminescent flank markings may play a role in intraspecific communication.

<span class="mw-page-title-main">Blackmouth catshark</span> Species of shark

The blackmouth catshark is a species of deepwater catshark, belonging yo the family Pentanchidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of 150–1,400 m (490–4,590 ft), on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of 50–79 cm (20–31 in), with sharks in the Atlantic growing larger than those in the Mediterranean.

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

The blue skate, 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, the combined taxon being known as the common skate. 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. 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 and it is protected within the EU.

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

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The purple eagle ray is a species of fish in the family Myliobatidae. It was formerly considered endemic to Australia but is now known to be more widespread. Its natural habitat is the open seas where it has a patchy distribution, and the International Union for Conservation of Nature has assessed its conservation status as being "near-threatened".

The longnose eagle ray or snouted eagle ray is a species of fish in the family Myliobatidae. It is found in the East Pacific Ocean from Baja California and the Gulf of California to Sechura, Peru, ranging from shallow water to a depth of 64 m (210 ft). This species was first described in 1964 by the American ichthyologist Shelton Pleasants Applegate, who was an expert on fossil and living sharks, and by American marine biologist John Edgar Fitch.

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

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References

  1. 1 2 3 4 5 6 Jabado, R.W.; Chartrain, E.; Cliff, G.; Da Silva, C.; Derrick, D.; Dia, M.; Diop, M.; Doherty, P.; Leurs, G.H.L.; Metcalfe, K.; Pacoureau, N.; Porriños, G.; Seidu, I.; Soares, A.-L.; Tamo, A.; VanderWright, W.J.; Williams, A.B.; Winker, H. (2021). "Myliobatis aquila". IUCN Red List of Threatened Species . 2021: e.T161569A124508353. doi: 10.2305/IUCN.UK.2021-1.RLTS.T161569A124508353.en . Retrieved 20 November 2021.
  2. ↑ "Myliobatis aquila". WoRMS. World Register of Marine Species . Retrieved 1 April 2023.
  3. 1 2 3 4 5 "Myliobatis aquila: Common eagle ray". FishBase. Retrieved 5 June 2016.
  4. ↑ Muus, B., J. G. Nielsen, P. Dahlstrom and B. Nystrom (1999). Sea Fish. p. 76. ISBN   8790787005
  5. 1 2 3 Zsilavecz, Guido (2005). Coastal fishes of the Cape Peninsula and False Bay: a divers' identification guide. Cape Town: Southern Underwater Research Group. ISBN   0-620-34230-7. OCLC   70133147.
  6. 1 2 3 Christian, C. (1976-05-01). "Etude du regime alimentaire de l'Aigle de mer, Myliobatis aquila (L., 1758) des cotes tunisiennes". ICES Journal of Marine Science. 37 (1): 29–35. doi:10.1093/icesjms/37.1.29. ISSN   1054-3139.
  7. 1 2 Schwartz, Frank J (2005). "Tail spine characteristics of stingrays (order Myliobatiformes) found in the northeast Atlantic, Mediterranean, and Black Seas". Electronic Journal of Ichthyology. 1: 1–9.
  8. ↑ Maretic, Z. (1982-01-01). "Some clinical and epidemiological problems of venom poisoning today". Toxicon. 20 (1): 345–348. Bibcode:1982Txcn...20..345M. doi:10.1016/0041-0101(82)90241-0. ISSN   0041-0101. PMID   6123162.
  9. ↑ Kumar, R & Vennila, R & Palani, Damotharan & Shankar, Kanchana & Muthuvel, Arumugam & Thangavel, Balasubramanian. (2010). Abundance of stingrays in parangipettai coast and the importance of exploring properties of their venom. Inter. Jour. of Recent Scientific Research.
  10. 1 2 Guide of Mediterranean Skates and Rays (Myliobatis aquila). October 2022. Mendez L., Bacquet A. and F. Briand. http://www.ciesm.org/Guide/skatesandrays/Myliobatis-aquila
  11. 1 2 Tuya, Fernando; Asensio, Maite; Navarro, Alberto (2020-05-01). ""Urbanite" rays and sharks: Presence, habitat use and population structure in an urban semi-enclosed lagoon". Regional Studies in Marine Science. 37: 101342. Bibcode:2020RSMS...3701342T. doi:10.1016/j.rsma.2020.101342. hdl: 10553/73658 . ISSN   2352-4855. S2CID   225914133.
  12. ↑ Burton, Maurice; Burton, Robert (1969). International Wildlife Encyclopedia. Marshall Cavendish. pp. 729–731. ISBN   978-0-7614-7266-7.
  13. ↑ Gül, Güzin; Demirel, Nazli (2020). "Trophic interactions of uncommon batoid species in the Sea of Marmara". J. Black Sea/Mediterranean Environment. 26 (3): 294–309.
  14. 1 2 Ponte, Dário Dinis Sousa; Barcelos, Luís Miguel Duarte; Santos, Cristina Sousa; Medeiros, João; Barreiros, João P. (2016). "Diet of Dasyatis pastinaca and Myliobatis aquila (Myliobatiformes) from the Azores, NE Atlantic". Cybium. 40 (3): 209–214. ISSN   0399-0974.
  15. ↑ Grancagnolo, Desiree; Arculeo, Marco (2021). "Summer aggregation of common eagle ray, Myliobatis aquila (Chondrichthyes: Myliobatidae), in the Marine Protected Area of the Egadi Islands (southwestern Tyrrhenian Sea)". Biogeographia – the Journal of Integrative Biogeography. 36. doi: 10.21426/B636051230 . hdl: 10447/547067 . ISSN   1594-7629. S2CID   234245830.
  16. ↑ Whitehead, P.J.P., Bauchot, M.-L., Hureau, J. and Tortonese E. 1984. Fishes of the Northeastern Atlantic and the Mediterranean, Vol. I. UNESCO, Paris.
  17. ↑ Last, P., White, W., de Carvalho, M., Séret, B., Stehmann, M. and Naylor, G. 2016. Rays of the World. CSIRO Publishing, Clayton.
  18. 1 2 3 Capapé, Christian & Guélorget, Olivier & Vergne, Yvan & Jean-pierre, Quignard. (2007). Reproductive biology of the common eagle ray, Myliobatis aquila (Chondrichthyes: Myliobatidae) from the coast cf Languedoc (Southern France, northern Mediterranean). Vie et Milieu. 53. 25–30.
  19. ↑ Buxton, C.D.; Smale, M.J.; Wallace, J.H.; Cockcroft, V.G. (1984-01-01). "Inshore small-mesh trawling survey of the Cape south coast. Part 4. Contributions to the biology of some teleostei and Chondrichthyes". South African Journal of Zoology. 19 (3): 180–188. doi: 10.1080/02541858.1984.11447880 . ISSN   0254-1858.
  20. ↑ RAFRAFI-NOUIRA, Sihem; EL KAMEL-MOUTALIBI, Olfa; OUNIFI-BEN AMOR, Khadija; BEN AMOR, Mohamed Mourad; CAPAPÉ, Christian (2017). "A CASE OF HERMAPHRODITISM IN THE COMMON EAGLE RAY MYLIOBATIS AQUILA (CHONDRICHTHYES: MYLIOBATIDAE), REPORTED FROM THE TUNISIAN COAST (CENTRAL MEDITERRANEAN)". Annales: Anali za istrske in mediteranske študije = annali di Studi istriani e mediterranei = annals for Istrian and Mediterranean studies. Series historia naturalis (27–1). doi:10.19233/ASHN.2017.06.
  21. ↑ Llewellyn, J.; Euzet, L. (May 1964). "Spermatophores in the Monogenean Entobdella diadema Monticelli from the skin of sting-rays, with a note on the taxonomy of the parasite". Parasitology. 54 (2): 337–344. doi:10.1017/S0031182000067962. ISSN   1469-8161. S2CID   84808479.
  22. ↑ Tazerouti, Fadila; Neifar, Lassad; Euzet, Louis (2011-01-01). "Redescription of Monocotyle myliobatis (Monogenea, Monocotylidae) from the type host Myliobatis aquila (Elasmobranchii, Myliobatidae) off the Algerian coast". Acta Parasitologica. 56 (3). doi: 10.2478/s11686-011-0056-4 . ISSN   1896-1851. S2CID   25272145.
  23. ↑ Maretić, Z. (1982). "Elektrokardiografske promjene nakon ujeda i uboda otrovnih životinja". Arhiv Za Higijenu Rada I Toksikologiju. 33 (4): 325–333. ISSN   0004-1254.
  24. 1 2 Quero, Jean-Claude (1998-01-01). "Changes in the Euro-Atlantic fish species composition resulting from fishing and ocean warming". Italian Journal of Zoology. 65 (sup1): 493–499. doi: 10.1080/11250009809386873 . ISSN   1125-0003.
  25. ↑ Bonanomi, Sara; Pulcinella, Jacopo; Fortuna, Caterina Maria; Moro, Fabrizio; Sala, Antonello (2018-01-29). "Elasmobranch bycatch in the Italian Adriatic pelagic trawl fishery". PLOS ONE. 13 (1): e0191647. Bibcode:2018PLoSO..1391647B. doi: 10.1371/journal.pone.0191647 . ISSN   1932-6203. PMC   5788366 . PMID   29377920.
  26. ↑ Storelli, M.M; Giacominelli-Stuffler, R; Marcotrigiano, G.O (December 2002). "Total and methylmercury residues in cartilaginous fish from Mediterranean Sea". Marine Pollution Bulletin. 44 (12): 1354–1358. Bibcode:2002MarPB..44.1354S. doi:10.1016/S0025-326X(02)00223-0. PMID   12523539.
  27. ↑ Šlejkovec, Zdenka; Stajnko, Anja; Falnoga, Ingrid; Lipej, Lovrenc; Mazej, Darja; Horvat, Milena; Faganeli, Jadran (2014). "Bioaccumulation of Arsenic Species in Rays from the Northern Adriatic Sea". International Journal of Molecular Sciences. 15 (12): 22073–22091. doi: 10.3390/ijms151222073 . ISSN   1422-0067. PMC   4284695 . PMID   25470025.
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