Banded eagle ray

Last updated

Banded eagle ray
Dorsal view of banded eagle ray. Taken by Hamid Badar Osmany. Retrieved from Fish Base.png
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family: Myliobatidae
Genus: Aetomylaeus
Species:
A. nichofii
Binomial name
Aetomylaeus nichofii

The banded eagle ray (Aetomylaeus nichofii) is a species of fish in the family Myliobatidae. The species was first described by Bloch and Schneider in 1801. [1] As an elasmobranch, the banded eagle ray has a skeleton composed of cartilage. Like other eagle rays it has a depressiform, dorsoventrally flattened, shape to succeed in its benthic lifestyle. It preys mainly on benthic crustaceans, snails, and worms. [2] Its natural habitats are open seas, shallow seas, and coral reefs. As of 2016, this species is classified as vulnerable by the IUCN. The main threats to the banded eagle ray are overfishing and habitat destruction.

Contents

Description

Aetomylaeus nichofii is a relatively small eagle ray with a maximum disc width of 72 cm, [3] but most organisms are between 35 and 55 cm. [4] Like other members of Myliobatidae, this eagle ray is diamond-shaped with broad pectoral fins and a long tail. Gas exchange is facilitated by their dorsal spiracles, located behind their eyes, and their five ventral gill slits. [2] The species has a greyish brown dorsal coloration with 7 to 8 faint blue transverse bands. As the individual matures, the bands become less distinct and can be difficult to detect in adults. [5] Their ventral side is pale and whitish with dusky pectoral fins. [5]

Their tail length is between 1.5 and 2 times the organism's disc width. [3] The tail is characterized by faint blue banding with a greyish dorsal coloring and black ventral coloring. [2] They have a small dorsal fin close to the pelvic fin insertion, near the base of the tail. [6] This species has no caudal fin spine nor do they have any stinging apparutus, so they are not considered a stingray. [3]

Frontal view of A. nichofii. Frontal view of banded eagle ray.png
Frontal view of A. nichofii.

They have tapered pectoral fins that are broad relative to the organism's size. [2] Their pelvic fins are rounded and small relative to the pectoral fins. Their mouth contains 7 rows of molariform teeth in both the upper and lower jaw. Three smaller teeth rows run down each side of their jaw. [7] The head is small and narrow with a fleshy and rounded rostral lobe. [6] It protrudes forward and rises above the disc of the organism. [6] Like other members of the genus Aetomylaeus, their pectoral fins are separated from the rostral lobe. [6] The species has a long internasal flap with a fine fringe. [2] Adult males have a small knob on the upper anterior margin.t [6]

Intraspecific variation is common which can lead to difficulties in interspecific distinction. Aetomylaeus nichofii is often confused with A. caeruleofasciatus and A. wafckii. In general, A. nichofii has a shorter head and tail than A. caeruleofasciatus. [5] In addition, molecular data strongly supports the distinction of A. caeruleofasciatus as a separate species from A. nichofii. [5] A. wafickii has more transverse lines than A. nichofii (8-10 vs. 7-8 respectively), a lighter dorsal surface, and a shorter tail length, relative to organism size. [7] Unlike in A. nichofii, the bands on A. wafickii do not become less distinct with age.

Distribution

Geographic distribution of A. nichofii. Note: This map is outdated and still shows the incorrect distribution of this species in Northern Australia. Banded eagle ray distribution.jpg
Geographic distribution of A. nichofii. Note: This map is outdated and still shows the incorrect distribution of this species in Northern Australia.

The banded eagle ray has a large distribution across the Indo-West Pacific. [1] Historically it was estimated to occur from India to Papua New Guinea, north to Japan, and south to Northern Australia. [3] The distinction of A. caeruleofasciatus, which appears in Northern Australia and Papua New Guinea, shrank the historic distribution of A. nichofii. [1] The present distribution is now considered to be India to Indonesia and north to Japan (see Figure 3). There is also a fragmented population in the Persian Gulf. There has been sightings in Bangladesh, [8] Bahrain, [4] Brunei, Cambodia, China, India, Indonesia, Japan, North Korea, South Korea, Malaysia, Myanmar, Pakistan, the Philippines, Singapore, Sri Lanka, Taiwan, Thailand, Vietnam, possibly Maldives, and possibly Mozambique.

The banded eagle ray is a benthic fish that inhabits intertidal, nearshore waters, and coral reefs of tropical and temperate seas. [3] This species is often found in tropical or temperate seas. [2] It is amphidromous, found in both marine and brackish waters. [9] It is often found in areas with sandy substrates, at depths of up to 115m. [3] Wild specimens caught by the Queensland Museum Research team were found at depths ranging from 8-43m. [3] A study done from 2006 to 2012 in Bangladesh found the species to be abundant year round, but sightings were on the decline. [8]

Ecology

Eagle rays are aquilopelagic rays [10] that use their wing-like pectoral fins for powerful propulsion. Rays move using the vertical muscles in their exaggerated pectoral fins, often flapping these fins up and down in unison. [2] This allows for a flight-like movement along with large leaps out of the water characteristic of other eagle rays. [10] While they do forage and inhabit the bottom, they swim above the seafloor instead of burrowing like other rays. They feed by disturbing the substrate, using their narrow head, to target small inactive prey. They eat crustaceans (such as shrimp [11] ), snails, worms, and other invertebrates. [9] Due to their wide variety of prey, the banded eagle ray is considered a generalist species. Their molariform teeth are specialized for grinding up hard-shelled invertebrates. These teeth are replaced continuously throughout the organism's lifetime, allowing them to grow in size and crush larger prey as the fish grows. [2] As benthic feeders, banded eagle rays release nutrients from the sediment via the process of bioturbation. [12] Like other predatory organisms, this species contributes to the biological carbon pump through the production of feces and food falls (see whale fall). [12]

Like most other elasmobranchs, A. nichofii possess a lateral line and electroreception to aid them in sensing their surroundings. [2] The lateral line is composed of pores that lead to an internal channel lined with specialized neurosensory cells. It detects change in fluid flow, providing the organism with information on predator/prey detection, current, and turbulence. Electroreception is the process in which the organism receives directional information through the detection of electric fields in the water. The mechanism of how the field is detected is not certain and an active area of research.

The age of the organism can be estimated in the lab via growth rings found on their vertebrae. [2]

Reproduction

Ventral view of male A. nichofii. Ventral of male banded eagle ray.jpg
Ventral view of male A. nichofii.
Ventral view of female A. nichofii. Ventral view banded eagle ray.png
Ventral view of female A. nichofii.

While the reproduction of A. nichofii in specific is understudied, the reproduction of Chondrichthyes is well understood and can be applied to the base information on this species. Banded eagle rays exhibit internal fertilization and are ovoviviparous, meaning their eggs develop and hatch within the body, so they birth live pups. [9] They produce about 4 pups during each gestation period. [3] Pups have a disc width of about 17 cm at birth. Males mature into adults at a disc width between 39 and 42 cm, the maturation size of females is unknown. [3] Males possess reproductive organs known as claspers, which are a pair of grooved extensions at the base of the pelvic fin. One clasper is located on each side of the tail. Females have paired oviducts that lead to paired oviducal glands. [13]

Mating occurs when a male inserts one clasper into the female and transfers semen into her oviduct. In the oviducal gland, the egg is encased in a coat of jelly followed by a tertiary egg envelope. The egg envelope is transferred to the uteri where the egg continues its development. The uterus is crucial in regulating the environment of the egg to maintain appropriate growth conditions. Myliobatidae nurture their eggs via lipid histotrophy, a matrotrophic mode of reproduction. The uterus produces a lipid rich histotrophic “milk” which provides the fetus with the necessary nutrition to develop. The “milk” is secreted from the trophonemata which is in the uterine lining. [13]

Conservation and Threats

According to the IUCN, the banded eagle ray is considered vulnerable, and the species is on the decline. [1] Before its decline, the species was already naturally uncommon in certain areas of its distribution (Sea of Oman, Arabian Sea, and the Red Sea). [7] The IUCN estimated the population has decreased by more than 30% over the last three generations, based on declines in fish catch. [1] They are threatened by habitat loss due to fishery practices such as trawling, which destroy their benthic habitat. [1] In addition to habit loss, trawling threatens this species by increasing the likelihood of bycatch. They are often unintentionally damaged in the trawling process or become caught in the equipment and nets used when fishing for other organisms. Overexploitation of this species by unregulated fisheries is another major threat to A. nichofii. [1] The fish is harvested primarily for its meat and secondarily for its cartilage. [3] Until recently, the banded eagle ray was one of the main commercial species in South-East Asia. [3] The fish was also popular in Thai markets but has become less common since its decline.

Rays are inherently vulnerable to population decline due to their low reproductive output. When coupled with habitat loss, the likelihood of producing a successful generation is very low and a significant conservation concern. [7] A fishery study in Bahrain found a significant sex ratio biased towards males (89:37). [4] This unproportionate ratio lowers the chance of successful reproduction, since females are the limiting sex in population growth. A separate study in Bangladesh classified the banded eagle ray as a “vulnerable ray species” due to fishing pressure enforced by the exploitation of local shark fisheres. [8]

There is currently no conservation efforts geared directly towards the banded eagle ray. [1] One of the biggest conservation inhibitors is the unknown distribution and poor monitoring of eagle rays as a general group. [14] Without knowing where and when these animals occur, scientists cannot create concrete plans to protect them. To increase the surveillance of eagle rays, scientists are experimenting with machine learning. Aerial surveys are used to detect eagle rays which are easy to spot due to their unique shape and relatively large size. The process of gathering footage is relatively easy and efficient, but the manual processing where all the observations and counting occurs is time-consuming and prone to human error. [14] A group in New Caledonia tested out the ability of a deep learning detection model to detect and map eagle rays in a coral reef. After training the model, it successfully detected 92% of eagle rays from the provided images. Similar deep learning detection models have been tested on sea turtles, dugongs, pinniped, and whales, [14] yielding promising outcomes for the future of marine organism monitoring.

Related Research Articles

<span class="mw-page-title-main">Shovelnose guitarfish</span>

The shovelnose guitarfish, Rhinobatos productus, is a ray in the family Rhinobatidae. The genus is derived from the Greek word rhinos, meaning nose, and the Latin word batis, which means ray. R. productus was first described by William Orville Ayre in 1854. As its common name suggests, this species possesses a pointed shovel-shaped snout and a body similar to that of a guitar with a larger head and long, slender body. The shovelnose is considered to be a primitively developed ray, with many features of both sharks and rays. The shovelnose guitarfish was first considered to be a shark because of its dorsal fins' shape. Fossils of R. productus ancestors have been recovered, dating back over 100 million years.

<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 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">Japanese bullhead shark</span> Species of shark

The Japanese bullhead shark is a species of bullhead shark in the family Heterodontidae found in the northwestern Pacific Ocean off the coasts of Japan, Korea, and China. This benthic shark occurs at depths of 6–37 m (20–121 ft) over rocky bottoms or kelp beds. Measuring up to 1.2 m (3.9 ft) long, it can be identified by its short, blunt head, two high dorsal fins with anterior spines, and pattern of irregularly shaped, vertical brown bands and stripes. The Japanese bullhead shark is a docile, slow-swimming species that feeds mainly on shelled invertebrates and small bony fishes. Reproduction is oviparous, with females laying spiral-flanged eggs in communal "nests". This species is of little interest to fisheries.

<span class="mw-page-title-main">Blotchy swellshark</span> Species of shark

The blotchy swellshark or Japanese swellshark is a common species of catshark, belonging to the family Scyliorhinidae. The Blotchy swellshark is found at depths of 90–200 m (300–660 ft) in the northwestern Pacific Ocean, from Japan to Taiwan. It is benthic in nature and favors rocky reefs. Reaching 1.4 m (4.6 ft) in length, this thick-bodied shark has a broad head, large mouth, and two unequally-sized dorsal fins positioned far back past the pelvic fins. It can be identified by its dorsal coloration, consisting of seven brown "saddles" and extensive darker mottling on a light tan background. This species has often been confounded with the draughtsboard shark and the Sarawak pygmy swellshark in scientific literature.

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

The mouse catshark is a species of shark belonging to the family Pentanchidae, the deepwater catsharks. It is common in the northeastern Atlantic Ocean from Iceland to Western Sahara. There is much taxonomic confusion regarding this species in Icelandic waters, where it may be confounded with another species of Galeus or Apristurus. Probably not exceeding 49 cm (19 in) long, the mouse catshark has a uniformly brown body and is characterized by large, rounded pelvic fins and crests of enlarged dermal denticles along both the dorsal and ventral caudal fin margins. In addition, in adult males the inner margins of the pelvic fins are merged into an "apron".

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

The spotted eagle ray is a cartilaginous fish of the eagle ray family, Aetobatidae. As traditionally recognized, it is found globally in tropical regions, including the Atlantic, Pacific and Indian Oceans. Recent authorities have restricted it to the Atlantic with other populations recognized as the ocellated eagle ray and Pacific white-spotted eagle ray. Spotted eagle rays are most commonly seen alone, but occasionally swim in groups. They are ovoviviparous, the female retaining the eggs then releasing the young as miniature versions of the parent.

<i>Rhina ancylostoma</i> Species of cartilaginous fish

Rhina ancylostoma, also known as the bowmouth guitarfish, shark ray or mud skate, is a species of ray and a member of the family Rhinidae. Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates. This rare species occurs widely in the tropical coastal waters of the western Indo-Pacific, at depths of up to 90 m (300 ft). Highly distinctive in appearance, Rhina ancylostoma has a wide and thick body with a rounded snout and large shark-like dorsal and tail fins. Its mouth forms a W-shaped undulating line, and there are multiple thorny ridges over its head and back. It has a dorsal color pattern of many white spots over a bluish gray to brown background, with a pair of prominent black markings over the pectoral fins. This large species can reach a length of 2.7 m (8.9 ft) and weight of 135 kg (298 lb).

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

The longheaded eagle ray is a species of eagle ray in the family Myliobatidae. The longheaded eagle ray, like other members of the genus Aetobatus, is characteristically different from other genera of eagle rays, distinguished by their notched nasal curtain; complete, singular set of upper and lower teeth; and v-shaped teeth in the lower jaw. It is found in the tropical and warm temperate Indo-West Pacific. It formerly included populations in the northwest Pacific, but these were recognized as a separate species, Aetobatus narutobiei, in 2013. Longheaded eagle rays are benthopelagic fishes that feed on crustaceans, cephalopods, echinoderms, and small bony fishes. It is a poorly known species, but generally uncommon and considered endangered by the IUCN.

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

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

<span class="mw-page-title-main">Silver chimaera</span> Species of fish

The silver chimaera, or ginzame, is a species of holocephalan in the family Chimaeridae. They are found in the deep sea along the coast of East Asia, from Japan to Indonesia. They are chondrichthyans, closely related to sharks and rays, which means that they have a fully cartilaginous skeleton with no true bones.

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

The smooth butterfly ray is a species of cartilaginous fish in the family Gymnuridae. It is a member of the order Myliobatiformes, which contains 10 total families. Its natural habitats are shallow seas, subtidal aquatic beds, estuarine waters, and coastal saline lagoons. Its common name is derived from its compressed body, pectoral fins that are wider than their length, and overall diamond shape.

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

Hypnos monopterygius, also known as the coffin ray or Australian numbfish, is a species of electric ray endemic to Australia, where it is common in inshore waters shallower than 80 m (260 ft). It is the sole member of its genus Hypnos, and family Hypnidae. This small species typically reaches 40 cm (16 in) in length. Greatly enlarged pectoral fins and an extremely short tail, coupled with diminutive dorsal and caudal fins all concentrated towards the rear, give the coffin ray a distinctive pear-like shape. It is a varying shade of brown in colour above, and has tiny eyes and a large, highly distensible mouth.

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

The sharpnose guitarfish also known as the granulated guitarfish is a species of ray in the Glaucostegidae family. They belong to the subclass Elsamobranchii which are cartilaginous fish that include sharks, rays, and skates as shown in their morphology. They have a flattened ray-like body and shark-like elongated snout. This species was first described by Georges Cuvier in 1829, and despite their appearance, they don’t pose any threat to humans.. As of April 2022, the IUNC has classified the sharpnose guitarfish as critically endangered.

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

The crossback stingaree or banded stingaree is a species of stingray in the family Urolophidae. It is endemic to southeastern Australia, mainly off Victoria and Tasmania but also marginally to New South Wales and South Australia. This bottom-dwelling fish generally inhabits sand and reef habitats deeper than 100 m (330 ft) off Victoria, and muddy habitats in shallow bays and estuaries off Tasmania. Befitting its name, the crossback stingaree has a distinctive dark pattern on its back, consisting of a midline stripe that is crossed by three transverse bars. It has an oval pectoral fin disc with a blunt snout and a skirt-shaped curtain of skin between the nostrils. Its tail is short with no skin fold along the sides, and a deep, leaf-shaped caudal fin. The youngest rays may have a small dorsal fin in front of the stinging tail spine. This species reaches 50 cm (20 in) in length.

<i>Zebrias</i> Genus of fishes

Zebrias is a genus of ray-finned fish in the family Soleidae.

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

The common eagle ray or bullray is a species of fish in the family Myliobatidae. It inhabits the eastern Atlantic Ocean, the Mediterranean Sea and the south-western Indian Ocean.

<i>Raja radula</i> Ray in the genus Raja

The rough ray is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809.

References

  1. 1 2 3 4 5 6 7 8 9 Kyne, P.M., Compagno, L.J.V. & Bennett, M.B. (2016). Aetomylaeus nichofii. IUCN Red List of Threatened Species. https://doi.org/10.2305/IUCN.UK.2016-1.RLTS.T84784918A68607458.en
  2. 1 2 3 4 5 6 7 8 9 10 Last, P. R., & Stevens, J. D. (2009). Sharks and Rays of Australia. Harvard University Press.
  3. 1 2 3 4 5 6 7 8 9 10 11 Curtis, L. K. (2012). Species Profiles. Queensland's Threatened Animals. CSIRO PUBLISHING. pp. 198-199
  4. 1 2 3 Moore, A., & Peirce, R. (2013). Composition of elasmobranch landings in Bahrain. African Journal of Marine Science, 35(4), 593–596. https://doi.org/10.2989/1814232X.2013.866160
  5. 1 2 3 4 White, W.T., Last, P.R. & Baje, L. (2016). Aetomylaeus caeruleofasciatus, a new species of eagle ray (Myliobatiformes: Myliobatidae) from northern Australia and New Guinea. Ichthyological Research 63, 94–109. https://doi.org/10.1007/s10228-015-0480-9
  6. 1 2 3 4 5 Last, P., Naylor, G., Séret, B., White, W., De Carvalho, M., & Stehmann, M. (2016). Rays of the world. CSIRO PUBLISHING.
  7. 1 2 3 4 Jabado, R.W., Ebert, D.A. & Al Dhaheri, S.S. (2022). Resolution of the Aetomylaeus nichofii species complex, with the description of a new eagle ray species from the northwest Indian Ocean and a key to the genus Aetomylaeus (Myliobatiformes: Myliobatidae). Marine Biodiversity, 52(2), 15 https://doi.org/10.1007/s12526-021-01234-4
  8. 1 2 3 Jit, R. B., Singha, N. K., Ali S. H., & Rhaman, M. G. (2013). Availability of vulnerable elasmobranchs in the marine water of Bangladesh. Bangladesh Journal of Zoology, 40(2), 221-229.https://doi.org/10.3329/bjz.v40i2.14316
  9. 1 2 3 Jena S., Kalaiselvam M., Jayalakshmi S., & Jena G. (2023). Biodiversity of the Ray Fish along the Southeast Coast of India with Their Conservation Status: A Comprehensive Overview. Eur. Chem. Bull, 12(4). 1580-1591
  10. 1 2 Compagno, L. J. V. (1990). Alternative life-history styles of cartilaginous fishes in time and space. Environmental Biology of Fishes, 28. Kluwer Academic Publishers. 33-75. https://doi.org/10.1007/978-94009-2065-1_3
  11. ↑ Carassou, L., Al-Kindi, A. S., & Dobrestsov, S. (2017). Preliminary assessment of the trophic structure of demersal fish community in the Sea of Oman. Regional Studies in Marine Science, 16. 145–151. https://doi.org/10.1016/j.rsma.2017.08.008
  12. 1 2 Flowers, K. I., Heithaus, M. R., & Papastamatiou, Y. P. (2021). Buried in the sand: Uncovering the ecological roles and importance of rays. Fish and Fisheries, 22(1). 105–127. https://doi.org/10.1111/faf.12508
  13. 1 2 Musick, J. A. (2010). 1. Chondrichthyan Reproduction. In K. S. Cole (Ed.), Reproduction and Sexuality in Marine Fishes: Patterns and Processes. University of California Press. pp 3-20. https://doi.org/10.1525/9780520947979-004
  14. 1 2 3 Desgarnier, L., Mouillot, D., Vigliola, L., Chaumont, M., & Mannocci, L. (2022). Putting eagle rays on the map by coupling aerial video-surveys and deep learning. Biological Conservation, 267 https://doi.org/10.1016/j.biocon.2022.109494
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.