Eel

Eelsareray-finned fishbelonging to theorderAnguilliformes(/æŋˈɡwɪlɪfɔːrmiːz/), which consists of eight suborders, 20families, 164genera, and about 1000species.Eels undergo considerable development from the early larval stage to the eventual adult stage and are usuallypredators.
The term "eel" is also used for some other eel-shaped fish, such aselectric eels(genusElectrophorus), swamp eels (orderSynbranchiformes), anddeep-sea spiny eels(family Notacanthidae). However, these otherclades, with the exception of deep-sea spiny eels, whose orderNotacanthiformesis the sister clade to true eels,evolved their eel-like shapes independentlyfrom the true eels. As a main rule, most eels are marine. Exceptions are thecatadromousgenusAnguillaand thefreshwater moray,which spend most of their life in freshwater, theanadromousrice-paddy eel, which spawns in freshwater, and the freshwater snake eelStictorhinus.
Eels are elongated fish, ranging in length from 5 cm (2 in) in the one-jawed eel (Monognathusahlstromi) to 4 m (13 ft) in theslender giant moray.Adults range in weight from 30 g (1 oz) to well over 25 kg (55 lb). They possess nopelvic fins, and many species also lackpectoral fins. Thedorsalandanal finsare fused with thecaudalfin, forming a single ribbon running along much of the length of the animal.Eels swim by generating waves that travel the length of their bodies. They can swim backward by reversing the direction of the wave.
Most eels live in the shallow waters of theoceanand burrow into sand, mud, or amongst rocks. Most eel species arenocturnal, and thus are rarely seen. Sometimes, they are seen living together in holes or "eel pits". Some eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 m (13,000 ft). Only members of theAnguillaregularly inhabit fresh water, but they, too, return to the sea to breed.
The heaviest true eel is theEuropean conger. The maximum size of this species has been reported as reaching a length of 3 m (10 ft) and a weight of 110 kg (240 lb).Other eels are longer, but do not weigh as much, such as theslender giant moray, which reaches 4 m (13 ft).
Eels begin life as flat and transparentlarvae, calledleptocephali. Eel larvae drift in the sea's surface waters, feeding onmarine snow, small particles that float in the water. Eel larvae then metamorphose into glass eels and become elvers before finally seeking out their juvenile and adult habitats.Some individuals of anguillid elvers remains in brackish and marine areas close to coastlines,but most of them enter freshwater where they travel upstream and are forced to climb up obstructions, such asweirs, dam walls, and natural waterfalls.
Gertrude Elizabeth Bloodfound that the eel fisheries atBallisodarewere greatly improved by the hanging of loosely plaited grass ladders over barriers, enabling elvers to ascend more easily.
Several sets of classifications of eels exist; some, such asFishBasewhich divide eels into 20 families, whereas other classification systems such asITISandSystema Naturae 2000include additional eel families, which are noted below.
Genomic studies indicate that there is amonophyleticgroup that originated among the deep-sea eels.
The earliest fossil eels are known from the LateCretaceous(Cenomanian) ofLebanon. These early eels retain primitive traits such aspelvic finsand thus do not appear to be closely related to any extant taxa. Body fossils of modern eels do not appear until theEocene, althoughotolithsassignable to extant eel families and even some genera have been recovered from theCampanianandMaastrichtian, indicating some level of diversification among the extant groups prior to theCretaceous-Paleogene extinction, which is also supported by phylogenetic divergence estimates. One of these otolith taxa, the mud-dwellingPythonichthys arkansasensis, appears to have thrived in the aftermath of the K-Pg extinction, based on its abundance.
Taxonomy based onEschmeyer's Catalog of Fishes:
OrderAnguilliformes
In some classifications, the familyCyematidaeofbobtail snipe eelsis included in the Anguilliformes, but in the FishBase system that family is included in the orderSaccopharyngiformes.
Theelectric eelof South America is not a true eel but is aSouth American knifefishmore closely related to thecarpsandcatfishes.
Phylogeny based on Johnson et al. 2012.
Based on the Paleobiology Database:
Freshwater eels (unagi) and marine eels (conger eel,anago) are commonly used inJapanese cuisine; foods such asunadonandunajūare popular, but expensive. Eels are also very popular inChinese cuisine, and are prepared in many different ways.Hong Kongeel prices have often reached 1000HKD(128.86 US Dollars) per kg, and once exceeded 5000 HKD per kg. InIndia, eels are popularly eaten in theNortheast.Freshwater eels, known asKusiainAssamese, are eaten with curry,often with herbs.TheEuropean eeland other freshwater eels are mostly eaten inEuropeand theUnited States, and is considered critically endangered.A traditional eastLondonfood isjellied eels, although the demand has significantly declined since World War II. TheSpanish cuisinedelicacyangulasconsists of elver (young eels)sautéedinolive oilwithgarlic; elvers usually reach prices of up to 1000europer kg.New Zealand longfin eelis a traditionalMāorifood inNew Zealand. InItalian cuisine, eels from theValli di Comacchio, a swampy zone along theAdriaticcoast, are especially prized, along with freshwater eels ofBolsena Lakeand pond eels fromCabras, Sardinia. In northernGermany,the Netherlands, theCzech Republic,Poland,Denmark, andSweden, smoked eel is considered adelicacy.
Elvers, often fried, were once a cheap dish in theUnited Kingdom. During the 1990s, their numbers collapsed across Europe.They became a delicacy, and the UK's most expensive species.
Eels, particularly themoray eel, are popular among marineaquarists.
Eel blood is toxic to humansand other mammals,but both cooking and the digestive process destroy the toxic protein.
High consumption of eels is seen in European countries leading to those eel species being considered endangered.
In 2010, Greenpeace International added theEuropean eel,Japanese eel, andAmerican eelto its seafood red list.Japan consumes more than 70% of the global eel catch.
The English name "eel" descends fromOld Englishǣl,Common Germanic*ēlaz. Also from the common Germanic areWest Frisianiel,Dutchaal,GermanAal, andIcelandicáll. Katz (1998) identifies a number ofIndo-Europeancognates, among them the second part of the Latin word for eels,anguilla, attested in its simplex formilla(in a glossary only), and the Greek word for "eel",ἔγχελυςenkhelys(the second part of which is attested inHesychiusaselyes).The first compound member,anguis("snake"), is cognate to other Indo-European words for "snake" (compare Old Irishescung"eel", Old High Germanunc"snake", Lithuanianangìs, Greekophis, okhis,Vedic Sanskritáhi,Avestanaži, Armenianauj, iž,Old Church Slavonic*ǫžь, all from Proto-Indo-European*h₁ogʷʰis). The word also appears in the Old English word for "hedgehog", which isigil(meaning "snake eater"), and perhaps in theegi-of Old High Germanegidehsa"wall lizard".
According to this theory, the nameBellerophon(Βελλεροφόντης, attested in a variant Ἐλλεροφόντης inEustathius of Thessalonica) is also related, translating to "the slayer of the serpent" (ahihán). In this theory, the ελλερο- is an adjective form of an older word, ελλυ, meaning "snake", which is directly comparable to Hittiteellu-essar-"snake pit". This myth likely came to Greece via Anatolia. In the Hittite version of the myth, the dragon is calledIlluyanka: theilluy-part is cognate to the wordilla, and the-ankapart is cognate toangu, a word for "snake". Since the words for "snake" (and similarly shaped animals) are often subject to taboo in many Indo-European (and non-Indo-European) languages, no unambiguous Proto-Indo-European form of the word for eel can be reconstructed. It may have been*ēl(l)-u-,*ēl(l)-o-, or something similar.
The large lake ofAlmere, which existed in the early MedievalNetherlands, got its name from the eels which lived in its water (the Dutch word for eel isaalorael, so: "ael mere" = "eel lake"). The name is preserved in the new city ofAlmereinFlevoland, given in 1984 in memory of this body of water on whose site the town is located.
The daylight passage in the spring ofelversupstream along theThameswas at one time called "eel fare". The word 'elver' is thought to be a corruption of "eel fare".
A famous attraction on theFrench Polynesianisland ofHuahine(part of theSociety Islands) is the bridge across a stream hosting three- to six-foot-long eels, deemed sacred by local culture.
Eel fishing inNazi-eraDanzigplays an important role inGünter Grass' novelThe Tin Drum. The cruelty of humans to eels is used as a metaphor for Nazi atrocities, and the sight of eels being killed by a fisherman triggers the madness of the protagonist's mother.
Sinister implications of eels fishing are also referenced inJo Nesbø'sCockroaches, the second book of theHarry Holedetective series. The book's background includes a Norwegian village where eels in the nearby sea are rumored to feed on the corpses of drowned humans, making the eating of these eels verge on cannibalism.
The 2019 bookThe Gospel of the Eelsby Patrick Svensson commented on the 'eel question' (origins of the order) and its cultural history.