Anguillidae
Encyclopedia
Anguillidae is a family
of fishes that contains the freshwater eels. There are 19 species/subspecies in this family, all in genus Anguilla. They are catadromous, meaning they spend their lives in freshwater
river
s, lake
s, or estuaries and return to the ocean to spawn. 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
. See Eel life history
. 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.
Freshwater eels are elongate with tubelike, snake-shaped bodies. They have large, pointed heads and their dorsal fins are usually continuous with their caudal fins and anal fins, to form a fringe lining the posterior end of the body. They have small pectoral fins to help them navigate along river bottoms. Their scales are thin and soft.
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 amount of production has been in China.
Seafood watch
, one of the most well known sustainable seafood advisory list
s, recommends that 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 eel consumed in the U.S. 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 carnivore
s and as such are fed other wild-caught fish, adding an additional element of unsustainability to current eel farming practices.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of fishes that contains the freshwater eels. There are 19 species/subspecies in this family, all in genus Anguilla. They are catadromous, meaning they spend their lives in freshwater
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s, lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s, or estuaries and return to the ocean to spawn. The young eel larvae, called leptocephali
Leptocephalus
A leptocephalus is the flat and transparent larva of the eel, marine eels, and other members of the Superorder Elopomorpha. Fishes with a leptocephalus larva stage include the most familiar eels such as the conger, moray eel, and garden eel, and the freshwater eels of the family Anguillidae, plus...
, 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
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....
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
Sargasso Sea
The Sargasso Sea is a region in the middle of the North Atlantic Ocean, surrounded by ocean currents. It is bounded on the west by the Gulf Stream; on the north, by the North Atlantic Current; on the east, by the Canary Current; and on the south, by the North Atlantic Equatorial Current. This...
is one of the more famous anecdotes in the history of Ichthyology
Ichthyology
Ichthyology is the branch of zoology devoted to the study of fish. This includes skeletal fish , cartilaginous fish , and jawless fish...
. See Eel life history
Eel life history
The eel is a long, thin bony fish of the order Anguilliformes. Because fishermen never caught anything they recognized as young eels, the life cycle of the eel was a mystery for a very long period of scientific history...
. 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.
Freshwater eels are elongate with tubelike, snake-shaped bodies. They have large, pointed heads and their dorsal fins are usually continuous with their caudal fins and anal fins, to form a fringe lining the posterior end of the body. They have small pectoral fins to help them navigate along river bottoms. Their scales are thin and soft.
Anguillid eels are important food fish. Eel aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
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
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...
, Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
and 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...
, but in recent years the greatest amount of production has been in China.
Seafood watch
Seafood Watch
Seafood Watch is one of the best known sustainable seafood advisory lists, and has influenced similar programs around the world. It is a program designed to raise consumer awareness about the importance of buying seafood from sustainable sources...
, one of the most well known sustainable seafood advisory list
Sustainable seafood advisory lists and certification
Sustainable seafood advisory lists and certification are programs aimed at increasing consumer awareness of the environmental impact and sustainability of their seafood purchasing choices....
s, recommends that consumers avoid eating anguillid eels due to significant pressures on worldwide populations. Several species used as unagi
Unagi
Unagi is the Japanese word for freshwater eels, especially the Japanese eel, Anguilla japonica. Saltwater eels are known as anago in Japanese. Unagi are a common ingredient in Japanese cooking...
have seen their population sizes greatly reduced in the past half century. Catches of the European Eel
European eel
The European eel, Anguilla anguilla, is a species of eel, a snake-like, catadromous fish. They can reach in exceptional cases a length of 1½ m, but are normally much smaller, about 60–80 cm, and rarely more than 1 m....
, for example, have declined about 80% since the 1960s. Although about 90% of freshwater eel consumed in the U.S. are farm-raised
Fish farming
Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young fish into the wild for recreational fishing or to supplement a species'...
, they are not bred in captivity
Captive breeding
Captive breedingis the process of breeding animals in human controlled environments with restricted settings, such as wildlife reserves, zoos and other conservation facilities; sometimes the process is construed to include release of individual organisms to the wild, when there is sufficient...
. 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 carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s and as such are fed other wild-caught fish, adding an additional element of unsustainability to current eel farming practices.
Species
- Anguilla anguilla (Linnaeus, 1758) (European eel)
- Anguilla australis J. RichardsonJohn Richardson (naturalist)Sir John Richardson was a Scottish naval surgeon, naturalist and arctic explorer.Richardson was born at Dumfries. He studied medicine at Edinburgh University, and became a surgeon in the navy in 1807. He traveled with John Franklin in search of the Northwest Passage on the Coppermine Expedition of...
, 1841- Anguilla australis australis J. RichardsonJohn Richardson (naturalist)Sir John Richardson was a Scottish naval surgeon, naturalist and arctic explorer.Richardson was born at Dumfries. He studied medicine at Edinburgh University, and became a surgeon in the navy in 1807. He traveled with John Franklin in search of the Northwest Passage on the Coppermine Expedition of...
, 1841 (Short-finned eel) - Anguilla australis schmidti Phillipps, 1925
- Anguilla australis australis J. Richardson
- Anguilla bengalensisAnguilla bengalensisAnguilla bengalensis is a species of eel in the genus Anguilla of the family Anguillidae and consists of two sub-species.-Subspecies:* Anguilla bengalensis bengalensis sometimes known as the Indian mottled eel....
(J. E. GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1831)- Anguilla bengalensis bengalensis (J. E. GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1831) (Indian mottled eel) - Anguilla bengalensis labiata (W. K. H. PetersWilhelm PetersWilhelm Karl Hartwich Peters was a German naturalist and explorer.He was assistant to Johannes Peter Müller and later curator of the Berlin Zoological Museum. In September 1842 he travelled to Mozambique via Angola. He returned to Berlin with an enormous collection of natural history specimens...
, 1852) (African mottled eel)
- Anguilla bengalensis bengalensis (J. E. Gray
- Anguilla bicolorAnguilla bicolorAnguilla bicolor is a species of eel in the genus Anguilla of the family Anguillidae consisting of two sub-species.-Subspecies:* Anguilla bicolor bicolor sometimes known as the Indonesian shortfin eel....
McClelland, 1844- Anguilla bicolor bicolor McClelland, 1844 (Indonesian shortfin eel)
- Anguilla bicolor pacifica E. J. SchmidtJohannes Schmidt (biologist)Johannes Schmidt was a Danish biologist credited with discovering in 1920 that eels migrate to the Sargasso Sea to spawn...
, 1928 (Indian shortfin eel)
- Anguilla breviceps Y. T. Chu & Y. T. Jin, 1984
- Anguilla celebesensis KaupJohann Jakob KaupJohann Jakob Kaup was a German naturalist.-Biography:He was born at Darmstadt. After studying at Göttingen and Heidelberg he spent two years at Leiden, where his attention was specially devoted to the amphibians and fishes. He then returned to Darmstadt as an assistant in the grand ducal museum,...
, 1856 (Celebes longfin eel) - Anguilla dieffenbachii J. E. GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1842 (New Zealand longfin eel) - Anguilla interioris WhitleyGilbert Percy WhitleyGilbert Percy Whitley was a British-born Australian ichthyologist and malacologist who was Curator of Fishes at the Australian Museum in Sydney for about 40 years. He was born at Swaythling, Southampton, England, and was educated at King Edward VI School, Southampton and Osborne House...
, 1938 (Highlands longfin eel) - Anguilla japonica TemminckCoenraad Jacob TemminckCoenraad Jacob Temminck was a Dutch aristocrat and zoologist.Temminck was the first director of the National Natural History Museum at Leiden from 1820 until his death. His Manuel d'ornithologie, ou Tableau systematique des oiseaux qui se trouvent en Europe was the standard work on European birds...
& SchlegelHermann SchlegelHermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...
, 1847 (Japanese eel) - Anguilla luzonensis S. Watanabe, Aoyama & Tsukamoto, 2009 (Philippine mottled eel)
- Anguilla malgumora KaupJohann Jakob KaupJohann Jakob Kaup was a German naturalist.-Biography:He was born at Darmstadt. After studying at Göttingen and Heidelberg he spent two years at Leiden, where his attention was specially devoted to the amphibians and fishes. He then returned to Darmstadt as an assistant in the grand ducal museum,...
, 1856 (Indonesian longfinned eel) - Anguilla marmorata QuoyJean René Constant QuoyJean René Constant Quoy was a French zoologist.Along with Joseph Paul Gaimard he served as naturalist aboard La Coquille under Louis Isidore Duperrey during its circumnavigation of the globe , and the Astrolabe under the command of Jules Dumont d'Urville...
and GaimardJoseph Paul GaimardJoseph Paul Gaimard was a French naval surgeon and naturalist.Along with Jean René Constant Quoy he served as naturalist on the ships L'Uranie under Louis de Freycinet 1817-1820, and L'Astrolabe under Jules Dumont d'Urville 1826-1829...
, 1824 (Giant mottled eel) - Anguilla megastoma KaupJohann Jakob KaupJohann Jakob Kaup was a German naturalist.-Biography:He was born at Darmstadt. After studying at Göttingen and Heidelberg he spent two years at Leiden, where his attention was specially devoted to the amphibians and fishes. He then returned to Darmstadt as an assistant in the grand ducal museum,...
, 1856 (Polynesian longfin eel) - Anguilla mossambica (W. K. H. PetersWilhelm PetersWilhelm Karl Hartwich Peters was a German naturalist and explorer.He was assistant to Johannes Peter Müller and later curator of the Berlin Zoological Museum. In September 1842 he travelled to Mozambique via Angola. He returned to Berlin with an enormous collection of natural history specimens...
, 1852) (African longfin eel) - Anguilla nebulosa McClelland, 1844 (Mottled eel)
- Anguilla nigricans Y. T. Chu & Y. T. Wu, 1984
- Anguilla obscura Günther, 1872 (Pacific shortfinned eel)
- Anguilla reinhardtii SteindachnerFranz SteindachnerFranz Steindachner was an Austrian zoologist.- Work and career :Being interested in natural history, Steindachner took up the study of fossil fishes on the recommendation of his friend Eduard Suess...
, 1867 (Speckled longfin eel) - Anguilla rostrata (LesueurCharles Alexandre LesueurCharles Alexandre Lesueur was a French naturalist, artist and explorer.Pictured here is the oil portrait by Charles Willson Peale of Charles-Alexandre Lesueur...
, 1817) (American eel)