Common eagle ray Temporal range: | |
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Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Superorder: | Batoidea |
Order: | Myliobatiformes |
Family: | Myliobatidae |
Genus: | Myliobatis |
Species: | M. aquila |
Binomial name | |
Myliobatis aquila | |
Synonyms [2] | |
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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]
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]
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]
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]
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]
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]
Juvenile males have thread-like testes and genital ducts. The orbits have a smooth surface. Sub-adult males have no eternally 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]
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]
Several parasites live in and on this species. These include Entobdella diadema on the skin and Monocotyle myliobatis in the gills. [21] [22]
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]
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]
This species has gained economic importance through underwater photographers and other SCUBA divers. [14]
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]
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]
Stingrays are a group of sea rays, a type of cartilaginous fish. They are classified in the suborder Myliobatoidei of the order Myliobatiformes and consist of eight families: Hexatrygonidae, Plesiobatidae, Urolophidae (stingarees), Urotrygonidae, Dasyatidae, Potamotrygonidae, Gymnuridae and Myliobatidae . There are about 220 known stingray species organized into 29 genera.
Bycatch, in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juveniles of the target species. The term "bycatch" is also sometimes used for untargeted catch in other forms of animal harvesting or collecting. Non-marine species that are caught but regarded as generally "undesirable" are referred to as rough fish or coarse fish.
The kitefin shark or seal shark is a species of squaliform shark in the family Dalatiidae, and the type species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of 200–600 m (660–1,970 ft). With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to cruise slowly through the water while expending little energy. The kitefin shark, the largest luminous vertebrate on record, has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (3.3–4.6 ft), though examples as long as 5.9 ft (180 cm) have been encountered.
Myliobatis is a genus of eagle rays in the family Myliobatidae.
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".
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.
The devil fish or giant devil ray is a species of ray in the family Mobulidae. It is currently listed as endangered, mostly due to bycatch mortality in unrelated fisheries.
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.
The blackmouth catshark is a species of catshark, and part of the family Scyliorhinidae, 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.
The common skate, also known as the blue skate, is the largest skate in the world, attaining a length of up to 2.85 m. 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 species was uplisted to critically endangered on the IUCN Red List in 2006 and it is protected within the EU.
The pelagic stingray is a species of stingray in the family Dasyatidae, and the sole member of its genus. It is characterized by the wedge-like shape of its pectoral fin disc, which is much wider than long, as well as by the pointed teeth in both sexes, whip-like tail with extremely long tail spine, and uniform violet to blue-green coloration. It generally reaches 59 cm (23 in) in width. The pelagic stingray has a worldwide distribution in waters warmer than 19 °C (66 °F), and migrates seasonally to spend the summer closer to the continental shelf and at higher latitudes. The only stingray that almost exclusively inhabits the open ocean, this species is typically found in surface waters down to a depth of 100 m (330 ft). As a consequence of its midwater habits, its swimming style has evolved to feature more of a flapping motion of the pectoral fins, as opposed to the disc margin undulations used by other, bottom-dwelling stingrays.
Mullus barbatus is a species of goatfish found in the Mediterranean Sea, Sea of Marmara, the Black Sea and the eastern North Atlantic Ocean, where its range extends from Scandinavia to Senegal. They are fished, mostly by trawling, with the flesh being well regarded. The International Union for Conservation of Nature has assessed their conservation status as being of "least concern".
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.
The common stingray is a species of stingray in the family Dasyatidae, found in the northeastern Atlantic Ocean and the Mediterranean and Black Seas. It typically inhabits sandy or muddy habitats in coastal waters shallower than 60 m (200 ft), often burying itself in sediment. Usually measuring 45 cm (18 in) across, the common stingray has a diamond-shaped pectoral fin disc slightly wider than long, and a whip-like tail with upper and lower fin folds. It can be identified by its plain coloration and mostly smooth skin, except for a row of tubercles along the midline of the back in the largest individuals.
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