Anguillidae

The Anguillidae are a family of ray-finned fish that contains the freshwater eels. Eighteen of the nineteen extant species and six subspecies in this family are in the genus Anguilla. They are elongated fish with snake-like bodies, their long dorsal, caudal and anal fins forming a continuous fringe. They are catadromous fish, spending their adult lives in fresh water but migrating to the ocean to spawn. Eels are an important food fish and some species are now farm-raised but not bred in captivity. Many populations in the wild are now threatened and Seafood Watch recommend consumers avoid eating anguillid eels.

Anguillidae
Temporal range: Danian–0

Early Paleocene (Danian) to Present[1]
Anguillarostratakils
American eel, Anguilla rostrata
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Rafinesque, 1810
Genus: Anguilla
Garsault, 1764[2]
Species

See text.

Characteristics

Members of this family spend their lives in freshwater rivers, lakes, or estuaries, and return to the ocean to spawn.[3] The young eel larvae, called leptocephali, live only in the ocean and consume small particles called marine snow. They grow larger in size, and in their next growth stage, they are called glass eels. At this stage, they enter estuaries, and when they become pigmented, they are known as elvers. Elvers travel upstream in freshwater rivers, where they grow to adulthood. Some details of eel reproduction are as yet unknown, and the discovery of the spawning area of the American and European eels in the Sargasso Sea is one of the more famous anecdotes in the history of ichthyology. The spawning areas of some other anguillid eels, such as the Japanese eel, and the giant mottled eel, were also discovered recently in the western North Pacific Ocean.ě

Freshwater eels are elongated with tubelike, snake-shaped bodies. They have large, pointed heads and their dorsal fins are usually continuous with their caudal and anal fins, to form a fringe lining the posterior end of their bodies. They have small pectoral fins to help them navigate along river bottoms. Their scales are thin and soft. Freshwater eels go through physical changes in their bodies when going to and from the ocean for different stages of life.[4]

Uses

Anguillid eels are important food fish. Eel aquaculture is a fast-growing industry. Important food eel species include longfin eel, Australian long-finned eel, short-finned eel, and Japanese eel. Most eel production historically has been in Japan, Korea, and Taiwan, but in recent years, the greatest production has been in China.

Seafood Watch, one of the better-known sustainable seafood advisory lists, recommends consumers avoid eating anguillid eels due to significant pressures on worldwide populations. Several species used as unagi have seen their population sizes greatly reduced in the past half century. Catches of the European eel, for example, have declined about 80% since the 1960s. Although about 90% of freshwater eels consumed in the US are farm-raised, they are not bred in captivity. Instead, young eels are collected from the wild and then raised in various enclosures. In addition to wild eel populations being reduced by this process, eels are often farmed in open net pens which allow parasites, waste products, and diseases to flow directly back into wild eel habitat, further threatening wild populations. Freshwater eels are carnivores and as such are fed other wild-caught fish, adding another element of unsustainability to current eel-farming practices.[5]

Species

Phylogeny of Anguillidae by Inoue et al. 2010[6]
Anguilla

A. mossambica

A. borneensis

A. anguilla

A. rostrata

A. australis

A. dieffenbachii

A. reinhardtii

A. japonica

A. celebesensis

A. megastoma

A. marmorata

A. nebulosa

A. interioris

A. obscura

A. bicolor

References

  1. ^ Werner Schwarzhans (2012). "Fish otoliths from the Paleocene of Bavaria (Kressenberg) and Austria (Kroisbach and Oiching-Graben)". Palaeo Ichthyologica. 12: 1–88.
  2. ^ Pl. 661 in Garsault, F. A. P. de 1764. Les figures des plantes et animaux d'usage en medecine, décrits dans la Matiere Medicale de Mr. Geoffroy medecin, dessinés d'après nature par Mr. de Gasault, gravés par Mrs. Defehrt, Prevost, Duflos, Martinet &c. Niquet scrip. [5]. - pp. [1-4], index [1-20], Pl. 644-729. Paris.
  3. ^ McCosker, John F. (1998). Paxton, J.R.; Eschmeyer, W.N., eds. Encyclopedia of Fishes. San Diego: Academic Press. p. 89. ISBN 0-12-547665-5.
  4. ^ Pankhurst N. W. 1982. Relation of Visual Changes to the onset of sexual maturation in the European eel (Anguilla Anguilla L.). Journal of Fish Biol 21: 1287-140
  5. ^ Halpin, Patricia (2007). "Seafood Watch: Unagi" (PDF). Monterey Bay Aquarium. Archived from the original (PDF) on 2010-07-06.
  6. ^ Jun G. Inoue et al.: Deep-ocean origin of the freshwater eels. Biol. Lett. 2010 6, S. 363–366, doi:10.1098/rsbl.2009.0989
  • Froese, Rainer, and Daniel Pauly, eds. (2011). "Anguillidae" in FishBase. June 2011 version.
  • Berra, Tim M. (2001). Freshwater Fish Distribution. San Diego: Academic Press. ISBN 0-12-093156-7
African longfin eel

The African longfin eel (Anguilla mossambica), also known simply as the longfin eel, is an eel in the family Anguillidae. It was described by Wilhelm Peters in 1852, originally under the genus Muraena. It is a tropical eel known from freshwaters in southern Kenya, Cape Agulhas, Madagascar, and New Caledonia. The eels spend most of their lives in freshwaters far inland, but migrate to the Western Indian Ocean to breed. Males can reach a maximum total length of 150 centimetres; females can reach a maximum standard length of 120 centimetres and a maximum weight of 5,000 grams. The eels can live for about 20 years. Juveniles and adults are known to feed off of carcasses, crabs, and bony fish.

Anguilla bengalensis

The mottled eel (Anguilla bengalensis), also known as the African mottled eel, the Indian longfin eel, the Indian mottled eel, the long-finned eel or the river eel, is a demersal, catadromous eel in the family Anguillidae. It was described by John McClelland in 1844. It is a tropical, freshwater eel which is known from East Africa, Bangladesh, Andaman Islands, Mozambique, Malawi, Sri Lanka, Sumatra, and Indonesia and recently from Madagascar. The eels spend most of their lives in freshwater at a depth range of 3–10 metres, but migrate to the Indian Ocean to breed. Males can reach a maximum total length of 121 centimetres and a maximum weight of 7,000 grams. The eels feed primarily off of benthic crustaceans, mollusks, finfish and worms.The exact classification of the species was a debate in recent times, where some major fish websites (ex. Fish Base) classified the species under the name A. nebulosa. But according to the IUCN Red List 2015 version, the fish species should be classified as A. bengalensis with some subspecies.

Anguilla bengalensis bengalensis

Anguilla bengalensis bengalensis, the Indian mottled eel, is a subspecies of eel in the genus Anguilla of the family Anguillidae. It is found throughout the Indian subcontinent and neighbouring regions including the East Indies.Showing the typical characteristics of the Anguillidae, this species grows to 1.2 m and as much as 6 kg. Dorsal fin soft rays number 250–305, anal fin soft rays 220–250, vertebrae between 106 and 112 in number.

The Indian mottled eel is valued as a food fish. The mucus of this eel is used in a medicine for arthritis. It is known by numerous common names in the native languages of the regions it inhabits.

Anguilla bengalensis labiata

Anguilla bengalensis labiata, the African mottled eel, is a subspecies of eel in the genus Anguilla of the family Anguillidae.

Showing the typical characteristics of the Anguillidae, this species grows to 1.75 m and as much as 20 kg. The adult diet consists of crabs, frogs and insects as well as fish. It is found in east Africa: Lake Kariba, middle Zambezi, Pungwe and Buzi systems, Upper and Lower Save/Rhunde system, Umzingwani and Limpopo rivers. The dorsal side of the fish is mottled yellow olive, the ventral surface lighter; adults are less obviously mottled than the juveniles.

Anguilla bicolor

Anguilla bicolor is a species of eel in the genus Anguilla of the family Anguillidae, consisting of two subspecies.

Anguilloidei

The Anguilloidei are a suborder of the order Anguilliformes (the eels) containing three families:

Anguillidae (freshwater eels)

Serrivomeridae (sawtooth eels)

Nemichthyidae (snipe eels)This suborder traditionally included several other families that have recently been moved to new suborders:

Chlopsidae (false morays), Heterenchelyidae (mud eels), Moringuidae (worm eels), Muraenidae (moray eels), and Myrocongridae (thin eels).

Celebes longfin eel

The Celebes longfin eel (Anguilla celebesensis) is an eel in the family Anguillidae. It was described by Johann Jakob Kaup in 1856. It is a tropical eel known from freshwaters in the Western Pacific, including Indonesia, the Philippines, New Guinea, and Western and American Samoa. The eels spend most of their lives in freshwater but migrate to the ocean to breed. Males can reach a maximum total length of 150 centimetres.The Celebes longfin eel is minorly commercial in fisheries.

European eel

The European eel (Anguilla anguilla) is a species of eel, a snake-like, catadromous fish. They can reach a length of 1.5 m (4 ft 11 in) in exceptional cases, but are normally around 60–80 cm (2.0–2.6 ft), and rarely reach more than 1 m (3 ft 3 in).

Eels have been important sources of food both as adults (including the famous jellied eels of East London) and as glass eels. Glass-eel fishing using basket traps has been of significant economic value in many river estuaries on the western seaboard of Europe.

While the species' lifespan in the wild has not been determined, captive specimens have lived over 80 years. According to a report in The Local, a specimen lived 155 years in the well of a family home in Brantevik, a fishing village in southern Sweden.

Giant mottled eel

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.

Highlands long-finned eel

The Highlands long-finned eel (Anguilla interioris, also known as the New Guinea eel) is an eel in the family Anguillidae. It was described by Gilbert Percy Whitley in 1938. It is a tropical eel known from freshwaters in eastern New Guinea. The eels spend most of their lives in freshwater but migrate to the ocean to breed. Males can reach a maximum total length of 80 centimetres.Anguilla interioris is considered most similar morphologically to Anguilla celebensis and Anguilla megastoma.

Indian shortfin eel

The Indian shortfin eel, Anguilla bicolor pacifica, is a species of eel in the genus Anguilla of the family Anguillidae.

Indonesian shortfin eel

The Indonesian shortfin eel, Anguilla bicolor bicolor, is a subspecies of eel in the genus Anguilla of the family Anguillidae. It is found throughout the tropical coastal regions of the Indian Ocean and Western Pacific Ocean.Showing the typical habits, diet and characteristics of the genus, this species grows to 1.2 m and can live for up to 20 years. Dorsal fin soft rays number 240–250, anal fin soft rays 200-220, Vertebrae between 105 and 109 in number. This fish is lighter underneath, being olive/blue-brown on top. It is easily confused with the Pacific shortfin eel, Anguilla obscura.

Japanese eel

The Japanese eel (Anguilla japonica; Japanese: 日本鰻 nihon'unagi) is a species of anguillid eel found in Japan, Korea, China, Taiwan, and Vietnam, as well as the northern Philippines. Like all the eels of the genus Anguilla and the family Anguillidae, it is catadromous, meaning it spawns in the sea, but lives parts of its life in fresh water. The spawning area of this species is in the North Equatorial Current in the western North Pacific to the west of the Mariana Islands. The larvae are called leptocephali and are carried westward by the North Equatorial Current and then northward by the Kuroshio Current to East Asia, where they live in rivers, lakes, and estuaries. The Japanese eel is an important food fish in East Asia, where it is raised in aquaculture ponds in most countries in the region. In Japan, where they are called unagi, they are an important part of the food culture, with many restaurants serving grilled eel, which is called kabayaki. Eels also have uses in Chinese medicine.

New Zealand longfin eel

The New Zealand longfin eel (Anguilla dieffenbachii) is the largest and the only endemic freshwater eel species in New Zealand. (The others are the native Shortfin eel, Anguilla australis, also found in Australia, and the naturally introduced Australian Longfin eel Anguilla reinhardtii). Longfin eels are long-lived, migrating to the Pacific Ocean near Tonga to breed at the end of their lives. They are good climbers as juvenile and so are found in streams and lakes a long way inland. An important traditional food source for Māori, longfin eels are threatened and declining but still commercially fished.

Pacific shortfinned eel

The Pacific shortfinned eel (Anguilla obscura), also known as the Pacific shortfinned freshwater eel, the short-finned eel, and the South Pacific eel, is an eel in the family Anguillidae. It was described by Albert Günther in 1871. It is a tropical, freshwater eel which is known from western New Guinea, Queensland, Australia, the Society Islands, and possibly South Africa. The eels spend most of their lives in freshwater, but migrate to the Pacific Ocean to breed. Males can reach a maximum total length of 110 centimetres, but more commonly reach a TL of around 60 cm. The Pacific shortfinned eel is most similar to Anguilla australis (more commonly known as the Short-finned eel), and Anguilla bicolor (the Indonesian shortfin eel), but can be distinguished by the number of vertebrae.The Pacific shortfinned eel feeds primarily off of bony fish (including the genus Oreochromis), crustaceans and mollusks. It is a commercial eel in subsistence fisheries.

Philippine mottled eel

The Philippine mottled eel (Anguilla luzonensis) is an eel in the family Anguillidae. It was described by Shun Watanabe, Jun Aoyama, and Katsumi Tsukamoto in 2009. It is a tropical eel known from the Pinacanauan River system on Luzon Island (from which the species epithet is derived), in the Philippines. The eels spend most of their lives in freshwater but migrate to the ocean to breed.

Polynesian longfinned eel

The Polynesian longfinned eel (Anguilla megastoma), also known as the Pacific long-finned eel, is an eel in the family Anguillidae. It was described by Johann Jakob Kaup in 1856. It is a tropical eel found in freshwaters in the Pacific, including Sulawesi, Indonesia; the Society Islands, and Pitcairn. The eels spend most of their lives in freshwater, but migrate to the ocean to breed. Males can reach a maximum total length of 100 centimetres, while females can reach a maximum TL of 165 centimetres and a maximum weight of 9,000 grams.The Polynesian longfinned eel is commercial in fisheries.

Short-finned eel

The short-finned eel (Anguilla australis), also known as the shortfin eel, is one of the 15 species of eel in the family Anguillidae. It is native to the lakes, dams and coastal rivers of south-eastern Australia, New Zealand, and much of the South Pacific, including New Caledonia, Norfolk Island, Lord Howe Island, Tahiti, and Fiji.

Speckled longfin eel

The speckled longfin eel, Australian long-finned eel or marbled eel (Anguilla reinhardtii) is one of 15 species of eel in the family Anguillidae. It has a long snake-like cylindrical body with its dorsal, tail and anal fins joined to form one long fin. It usually has a brownish green or olive green back and sides with small darker spots or blotches all over its body. Its underside is paler. It has a small gill opening on each side of its wide head, with thick lips. It is Australia's largest freshwater eel, and the female usually grows much larger than the male. It is also known as the spotted eel.

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