Marbled eel
Encyclopedia
The marbled eel, also known as the giant mottled eel, Anguilla marmorata, is a species of tropical anguillid eel
that is found in the Indo-Pacific
and adjacent freshwater habitats.
to French Polynesia
and as far north as southern Japan
. In Africa
, it may be found within Mozambique
and the lower Zambezi River. The marbled eel has the widest distribution of all the Anguilla eels. It is usually found in tropical climates between 24°N to 33°S. 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. It is not on the IUCN Red List of Threatened Species, but in Taiwan
, it is endangered.
In 2002, a single eel was captured from a pond close to Kaupo, Maui, Hawaii, though it is not indigenous to the area.
Similar to other anguillids, the marbled eel is cylindrical with small, well-developed pectoral fins and a protruding lower jaw. The eel has thick, fleshy lips. 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. It has small, oval-shaped scales that are embedded in the skin.
Unlike some other anguillid species, the marbled eel has a mottled color. The adult eels are yellow with a greenish-brown to black marbling on their back and a white belly. The young elvers
have less visible marbling and are grayish to yellow. The dorsal fin
of the marbled eel is closer to the gill
opening than to the anus
, more anterior than other species of Anguilla
. Like all anguillid eels, it does not have pelvic fins. The head is rounded and the snout is depressed. Its teeth are small and in bands. It has a total of 100 to 110 vertebrae.
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), which is larger than most other species of anguillid eels. The marbled eel can live up to about 40 years.
The adults of this species are demersal, living on the bottom of fresh to brackish waters, in rivers, lakes, and tributaries. This species and all anguillid eels are catadromous, migrating sometimes long distances out into the open ocean to spawning
over deep water. 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.
Marbled eels spend their adult lives in freshwater or estuarine habitats, and migrate to the ocean to reproduce. 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. Then, after about 8 to 20 years in brackish or freshwater, the yellow eels grow up into silver eels (mature eels), and they return back to the ocean for reproduction.
The marbled eel is carnivorous, but harmless, with a wide ranging diet, eating shrimp
, crabs, bony fish
, and frogs. It is nocturnal, so it is active at night.
Like other anguillid eels, this species is used as a source of food in some regions. Some restaurants buy live eels. In 1992, for example, a typical 12 kilogram (26.5 lb) marbled eel retailed for one thousand US dollars
in China
.
An eel habitat, Cheonjiyeon Waterfalls' pond
, is a natural monument in South Korea
.
Large individuals of this species are also highly regarded and are not harmed by native people in some island groups of the western Pacific.
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
that is found in the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
and adjacent freshwater habitats.
Distribution
This anguillid species can be found from East AfricaEast Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
to French Polynesia
French Polynesia
French Polynesia is an overseas country of the French Republic . It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...
and as far north as southern Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. In Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, it may be found within Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
and the lower Zambezi River. The marbled eel has the widest distribution of all the Anguilla eels. It is usually found in tropical climates between 24°N to 33°S. 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
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...
events. It is not on the IUCN Red List of Threatened Species, but in Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, it is endangered.
In 2002, a single eel was captured from a pond close to Kaupo, Maui, Hawaii, though it is not indigenous to the area.
Physical description
Unlike some other anguillid species, the marbled eel has a mottled color. The adult eels are yellow with a greenish-brown to black marbling on their back and a white belly. The young elvers
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
have less visible marbling and are grayish to yellow. The dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
of the marbled eel is closer to the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
opening than to the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
, more anterior than other species of Anguilla
Anguilla
Anguilla is a British overseas territory and overseas territory of the European Union in the Caribbean. It is one of the most northerly of the Leeward Islands in the Lesser Antilles, lying east of Puerto Rico and the Virgin Islands and directly north of Saint Martin...
. Like all anguillid eels, it does not have pelvic fins. The head is rounded and the snout is depressed. Its teeth are small and in bands. It has a total of 100 to 110 vertebrae.
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), which is larger than most other species of anguillid eels. The marbled eel can live up to about 40 years.
Ecology and behaviour
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
over deep water. A spawning area of this species is known to be west of the Mariana Islands
Mariana Islands
The Mariana Islands are an arc-shaped archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels north and along the 145th meridian east...
in an area of the North Equatorial Current
North Equatorial Current
The North Equatorial Current is a significant Pacific and Atlantic Ocean current that flows east-to-west between about 10° north and 20° north. It is the southern side of a clockwise subtropical gyre. Despite its name, the North Equatorial Current is not connected to the equator...
in the western North Pacific, but other spawning areas are thought to exist in the western South Pacific and Indian Ocean.
Marbled eels spend their adult lives in freshwater or estuarine habitats, and migrate to the ocean to reproduce. When the eggs hatch, the leptocephali drift in ocean currents for months until they reach estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
as glass eels where they migrate upstream into freshwater as elvers. Then, after about 8 to 20 years in brackish or freshwater, the yellow eels grow up into silver eels (mature eels), and they return back to the ocean for reproduction.
The marbled eel is carnivorous, but harmless, with a wide ranging diet, eating shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
, crabs, bony fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, and frogs. It is nocturnal, so it is active at night.
Significance to humans
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
.
An eel habitat, Cheonjiyeon Waterfalls' pond
Cheonjiyeon Waterfall
Cheonjiyeon Waterfall is a waterfall on Jeju Island, South Korea. Literally, the name Cheonjiyeon means sky connected with land . It is one of the main tourist attractions on Jeju-do. It is high and wide. Though water always falls in one particular area, depending on the amount of recent rain,...
, is a natural monument in South Korea
Natural monuments of South Korea
This is a partial list of natural monuments of South Korea. By 2009 a total of 576 animal, plants, landforms, geological formations, and nature reserves had been designated by the Cultural Heritage Administration of South Korea as natural monuments...
.
Large individuals of this species are also highly regarded and are not harmed by native people in some island groups of the western Pacific.