Anguilla marmorata, known by many common names including the marbled eel, giant mottled eel and long finned eel, is one of about 19 species in its genus, the only genus in the small freshwater eel family Anguillidae. Of the angillid eels, the marbled eel has the widest distribution, found in several discrete but intermixing populations throughout the tropics and subtropics across the southwestern and central Pacific ocean, in the northwestern Pacific as far north as Japan, and in the southeastern Indian ocean to southern Africa (Wanatabe et al. 2008, 2009; Gagnaire et al. 2011).It has been recorded in small numbers from the Galapagos (McCosker et al. 2003) though whether this is the edge of their natural range or an introduction is unclear (Vishwanath and Mailautoka 2012).
Marbled eels, like other anguillid eels, have a complex life history, spending most of their life in the “yellow eel growth phase,” during which they inhabit the bottoms of fresh and brackish continental waters.This can last 2-3 years in warmer regions and up to 20 years in colder northern areas.The eels then migrate long distances as “silver eels” to spawning regions in open ocean gullies located at depths of 150-300 meters (500-1540 feet).The spawning areas for the different marbled eel populations are not well identified, although those in the northern pacific are known to share spawning areas in the Mariana trench with the Japanese eel Anguilla marmorata (Tsukamoto 2011). The planktonic larvae hatch at sea and develop into glass eel larvae to return to continental waters.There they metamorphose into the pigmented elver stage whereupon they begin to feed and travel in schools to freshwater inland rivers, lakes, streams and estuaries where they complete their development.In areas of large shallow coastal seas, they may stay as elvers without migrating upstream to fresh waters (Vishwanath and Mailautoka 2012).
Distinguished by their mottled brown, green and yellow coloration, adults reach up to 2 meters (6.6 feet) in length; one of the largest angillids.They are usually encased in slime making them very slippery.Nocturnal carnivores, the adult eels eat a diverse diet rich in fish, amphibians and invertebrates such as crab and shrimp (Froese and Pauly 2006).Like other anguillid eels, the marbled eel is a sought-after commercial food fish, eaten at many of its developmental stages, and its fishery may well expand as other species of angillids decline (especially A. anguilla and A. japonica).Currently it is listed by the IUCN as of least concern at it is common throughout its wide range, however its potential vulnerability to decline due to fisheries pressure and habitat loss is recognized as an important parameter to monitor (Vishwanath and Mailautoka 2012).
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]
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 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]
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]
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]
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]
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.
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.
