Giant mottled eel

Giant mottled eel
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Genus: Anguilla
Species: A. marmorata
Binomial name
Anguilla marmorata
Quoy and Gaimard, 1824
Synonyms
  • Anguilla fidjiensis Günther, 1870
  • Anguilla hildebrandti Peters, 1881
  • Anguilla labrosa Richardson, 1848
  • Anguilla mauritiana Bennett, 1831
  • Anguilla ohannae Günther, 1867
  • Muraena manillensis Bleeker, 1864

The giant mottled eel (Anguilla marmorata), also known as the marbled eel, is a species of tropical anguillid eel that is found in the Indo-Pacific and adjacent freshwater habitats.[2]

Description

Specimen

Similar to other anguillids, the giant mottled eel is cylindrical with small, well-developed pectoral fins and a protruding lower jaw.[3] The eel has thick, fleshy lips.[3] The eel has dorsal and anal fins that are continuous around the tail, with the origin of the dorsal-fin origin between the pectoral fins and anus.[3] It has small, oval-shaped scales that are embedded in the skin.[3]

Unlike some other anguillid species, this species has a mottled color.[2][3] The adult eels are yellow with a greenish-brown to black marbling on their back and a white belly.[2][3] The young elvers have less visible marbling and are grayish to yellow.[2][3] The dorsal fin of the marbled eel is closer to the gill opening than to the anus, more anterior than other species of Anguilla.[3] Like all anguillid eels, it does not have pelvic fins.[4] The head is rounded and the snout is depressed.[4] Its teeth are small and in bands.[4] It has a total of 100 to 110 vertebrae.[2]

It can grow up to 2 meters (6.6 ft) for females and 1.5 meters (4.9 ft) for males and can weigh up to 20.5 kilograms (45 lb),[2] making it the largest species of anguillid eels. The marbled eel can live up to about 40 years.[3]

Distribution and habitat

This anguillid species can be found from East Africa to French Polynesia and as far north as southern Japan.[2][3][5] In Africa, it may be found within Mozambique and the lower Zambezi River.[2] The giant mottled eel has the widest distribution of all the Anguilla eels.[3][6] It is usually found in tropical climates between 24°N to 33°S.[2] It has also been found in other more distant regions such as the Galapagos possibly due to abnormal larval transport associated with El Niño-Southern Oscillation events.[7] It is not on the IUCN Red List of Threatened Species, but in Taiwan, it is endangered.[3][8]

In 2002, a single eel was captured from a pond close to Kaupo, Maui, Hawaii, though it is not indigenous to the area.[3]

Ecology and behaviour

Life cycle of eels

The adults of this species are demersal, living on the bottom of fresh to brackish waters, in rivers, lakes, and tributaries.[2] This species and all anguillid eels are catadromous, migrating sometimes long distances out into the open ocean to spawning over deep water.[2] A spawning area of this species is known to be west of the Mariana Islands in an area of the North Equatorial Current in the western North Pacific, but other spawning areas are thought to exist in the western South Pacific and Indian Ocean.[9]

Marbled eels spend their adult lives in freshwater or estuarine habitats, and migrate to the ocean to reproduce.[3] When the eggs hatch, the leptocephali drift in ocean currents for months until they reach estuaries as glass eels where they migrate upstream into freshwater as elvers.[3] Then, after about 8 to 20 years in brackish or freshwater, the yellow eels grow up into silver eels (mature eels), and they return to the ocean for reproduction.[3]

Feeding

The marbled eel is carnivorous, but harmless, with a wide ranging diet, eating shrimp, crabs, bony fish, and frogs.[10] It is nocturnal, so it is active at night.[10]

Significance to humans

Like other anguillid eels, this species is used as a source of food in some regions.[3] Some restaurants buy live eels.[3] In 1992, for example, a typical 12 kilogram (26.5 lb) marbled eel retailed for one thousand US dollars in China.[3][11]

An eel habitat, Cheonjiyeon Waterfalls' pond, is a natural monument in South Korea.[12]

Large individuals of this species are also highly regarded and are not harmed by native people in some island groups of the western Pacific.

References

  1. ↑ Jacoby, D. & Gollock, M. (2014). "Anguilla marmorata". IUCN Red List of Threatened Species. Version 2014.1. International Union for Conservation of Nature. Retrieved 1 July 2014.
  2. 1 2 3 4 5 6 7 8 9 10 11 Froese, Rainer and Pauly, Daniel, eds. (2006). "Anguilla marmorata" in FishBase. February 2006 version.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 USGS. Species Fact Sheet "Anguilla marmorata" Check |url= value (help). Retrieved 2006-11-21.
  4. 1 2 3 Discover Life. "Anguilla marmorata". Retrieved 2011-06-28.
  5. ↑ Tsukamoto, K.; Aoyama, J. (1998). "Evolution of freshwater eels of the genus Anguilla: a probable scenario". Environmental Biology of Fishes. 52: 139–148. doi:10.1023/A:1007427724175.
  6. ↑ Robinet, T.; Guyet, S.; Marquet, G. R.; Mounaix, B. A.; Olivier, J. M.; Tsukamoto, K.; Valade, P.; Feunteun, E. (2003). "Elver invasion, population structure and growth of marbled eels Anguilla marmorata in a tropical river on Réunion Island in the Indian Ocean". Environmental Biology of Fishes. 68 (4): 339–348. doi:10.1023/B:EBFI.0000005761.51686.f7.
  7. ↑ McCosker, J. E.; Bustamante, R. H. & Wellington, G. M. (2003). "The freshwater eel, Anguilla marmorata, discovered at Galapagos" (PDF). Noticias de Galápagos. 62: 2–6. Retrieved 21 June 2011.
  8. ↑ Shiao, J. C.; Iizuka, Y.; Chang, C. W.; Tzeng, W. N. (2003). "Disparities in habitat use and migratory behavior between tropical eel Anguilla marmorata and temperate eel A. japonica in four Taiwanese rivers" (PDF). Marine Ecology Progress Series. 261: 233–242. doi:10.3354/meps261233.
  9. ↑ Miller, M.; Mochioka, N.; Otake, T.; Tsukamoto, K. (2002). "Evidence of a spawning area of Anguilla marmorata in the western North Pacific". Marine Biology. 140 (4): 809–814. doi:10.1007/s00227-001-0754-9.
  10. 1 2 Paul Harvey Skelton (10 September 2001). A complete guide to the freshwater fishes of Southern Africa. Struik. p. 108. ISBN 978-1-86872-643-1. Retrieved 23 June 2011.
  11. ↑ Williamson, Gordon R.; Boëtius, Jan (1993). "The eels Anguilla marmorata and A. japonica in the Pearl River, China, and Hong Kong". Asian Fisheries Science. 6: 129–138.
  12. ↑ Lee, Cecilia Hae-Jin. (2008). Frommer's South Korea. Hoboken, NJ: Wiley. p. 392. ISBN 978-0-470-18191-1.
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