Giant guitarfish | |
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Species: | R. djiddensis
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Binomial name | |
Rhynchobatus djiddensis Forsskål, 1775
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The giant guitarfish (Rhynchobatus djiddensis), also known as the whitespotted wedgefish, is a large species of guitarfish in the family Rhinidae. It is restricted to the Red Sea, Persian Gulf, and western Indian Ocean,[3] but was formerly considered more widespread due to confusion with its relatives.[1]
Taxonomy and range
The giant guitarfish was previously believed to range throughout a large part of the Indo-Pacific, but recent evidence has shown that it, as traditionally defined, actually was a species complex consisting of four different species.[4] In addition to the giant guitarfish, this complex includes the white-spotted guitarfish, the broadnose wedgefish and possibly the smoothnose wedgefish. With these as separate species, the giant guitarfish has a relatively restricted range; it is found only in the Red Sea and Persian Gulf, and the western Indian Ocean as far south as South Africa.[3][5] Ranging across the western Indian Ocean, it is common to misidentify the separate species of guitarfish within a similar range.[6]
Description
A large fish reaching up to 3.1 m (10 ft) long and weighing as much as 227 kg (500 lb),[5] it is brownish or greyish above with a variable pattern of white spots. Juveniles have a black spot above each pectoral fin, but in adults it is a dusky ring or absent. There is a dark, bar-like pattern between the eyes (on top of the head), which separates it from the other Rhynchobatus species in its range.[3]
Behavior
Breeding
The giant guitarfish is considered ovoviviparous, where the embryos initially feed on the yolk and then receive more nourishment from uterine fluid enriched with mucus which is obtained by means of indirect absorption.[6] Because of their lower fecundity, the giant guitarfish are known to only produce, on average, four pups per litter during the summer.[6]
Diet
The giant guitarfish feeds on bivalves, crabs, lobsters, squid and small fish.[5][7] Despite not having any cutting teeth, this species is a known predator of stingrays. One specimen from the Philippines had more than 20 stingray barbs stuck in its jaw, apparently unaffected by the stingray's venom.[8]
Habitat
It is a shy fish, found at depths of 2–50 m (6.6–164.0 ft), inhabiting areas with a sandy sea floor. These are generally around coastal reefs or reef flats, but they will sometimes venture into the brackish waters of estuaries.[5][7]
Interaction with man
The giant guitarfish is harmless to humans. It is listed as critically endangered on the IUCN Red List as its population is believed to have declined significantly due to unregulated high levels of exploitation for its flesh and fins,[4] the latter for shark fin soup. Its low fecundity and presumed slow growth rate make it highly vulnerable to unsustainable exploitation.[4]
References
- ^ a b Kyne, P.M.; Gledhill, K.; Jabado, R.W. (2019). "Rhynchobatus djiddensis". IUCN Red List of Threatened Species. 2019: e.T39394A121035795. doi:10.2305/IUCN.UK.2019-2.RLTS.T39394A121035795.en. Retrieved 18 November 2021.
- ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
- ^ a b c Last; White; de Carvalho; Séret; Stehmann; Naylor, eds. (2016). Rays of the World. CSIRO. pp. 68–75. ISBN 9780643109148.
- ^ a b c Kyne, P.M., Gledhill, K. & Jabado, R.W. 2019. Rhynchobatus djiddensis. The IUCN Red List of Threatened Species 2019: e.T39394A121035795. https://doi.org/10.2305/IUCN.UK.2019-2.RLTS.T39394A121035795.en. Downloaded on 26 July 2019.
- ^ a b c d Froese, Rainer; Pauly, Daniel (eds.) (2007). "Rhynchobatus djiddensis" in FishBase. 7 2007 version.
- ^ a b c "Rhynchobatus djiddensis, Giant guitarfish : fisheries, gamefish, aquarium". www.fishbase.se. Retrieved 2022-10-19.
- ^ a b Lieske, E. and Myers, R.F. (2004) Coral reef guide; Red Sea London, HarperCollins ISBN 0-00-715986-2
- ^ Pavid, Katie. "The cannibal rays that eat fellow fish". Natural Science Museum.