Giant guitarfish: Difference between revisions
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== Population == |
== Population == |
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Giant guitarfishes have been exploited as incidental catch, and as a result, it has led to severe declines, reduced population size, and disappearances. Though the giant is labeled as critically endangered on the IUCN Red List, there is no specific data for the species that could be used to calculate the number of individuals in the decreasing population. Species-specific reporting and identification issues are the two major components as to why no accurate data is kept.<ref name=":1" /> |
Giant guitarfishes have been exploited as incidental catch, and as a result, it has led to severe declines, reduced population size, and disappearances. Though the giant is labeled as critically endangered on the IUCN Red List, there is no specific data for the species that could be used to calculate the number of individuals in the decreasing population. Species-specific reporting and identification issues are the two major components as to why no accurate data is kept.<ref name=":1" /> Although there's an insufficient data record kept on the exact giant guitarfish population; the harvest rates infer that the species is substantially decreasing while the fishing rates remain stable or even increase. As the human population along the coastlines increase, fishing technology is improvised, and the expansion of the fish markets ultimately lead to an increase in fishing effort on a global scale. The highest increases in the fishing industry have occurred around the regions of Asia.<ref>{{Cite web |title=Giant guitarfish |url=https://www.speciesonthebrink.org/species/giant-guitarfish/ |access-date=2022-11-10 |website=Asian Species Action Partnership |language=en-US}}</ref> |
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==Interaction with man== |
==Interaction with man== |
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Revision as of 05:59, 10 November 2022
| 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] In addition to this, the guitarfish can also be characterized by the large black eyespots on the pectoral bases and a distinct pointed snout.[6]
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]
Population
Giant guitarfishes have been exploited as incidental catch, and as a result, it has led to severe declines, reduced population size, and disappearances. Though the giant is labeled as critically endangered on the IUCN Red List, there is no specific data for the species that could be used to calculate the number of individuals in the decreasing population. Species-specific reporting and identification issues are the two major components as to why no accurate data is kept.[9] Although there's an insufficient data record kept on the exact giant guitarfish population; the harvest rates infer that the species is substantially decreasing while the fishing rates remain stable or even increase. As the human population along the coastlines increase, fishing technology is improvised, and the expansion of the fish markets ultimately lead to an increase in fishing effort on a global scale. The highest increases in the fishing industry have occurred around the regions of Asia.[10]
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. Although finning has been prohibited in the eastern Pacific, fins are still traded when the guitarfish is landed.[9] Its low fecundity and presumed slow growth rate make it highly vulnerable to unsustainable exploitation.[4]
Conservation
As of today, there are limited conservation efforts or management regulations established for the giant guitarfish. The practice of finning is now prohibited in all administrations in Australia. Along with this, general fisheries management and protected areas will most likely benefit the giant guitarfish in Australia.[9]
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.). "Rhynchobatus djiddensis". FishBase. July 2007 version.
- ^ a b c d "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.
- ^ a b c "Giant guitarfish". Asian Species Action Partnership. Retrieved 2022-11-03.
- ^ "Giant guitarfish". Asian Species Action Partnership. Retrieved 2022-11-10.