The European eel (''Anguilla anguilla'') is a species of
eel, a snake-like,
catadromous fish. They are normally around and rarely reach more than , but can reach a length of up to in exceptional cases.
Eels have been important sources of food both as adults (including
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. A specimen known as "the
Brantevik Eel The Brantevik Eel () (Before 1859 - Before 7 August 2014), also known as Åle, was a European eel (''Anguilla anguilla'') that is believed to have lived for more than 150 years.
The eel was released into a well in the town of Brantevik, Sweden
...
" lived for 155 years in the well of a family home in
Brantevik
Brantevik is a locality situated in Simrishamn Municipality, Skåne County, Sweden with 409 inhabitants in 2010. It was the home of the Brantevik Eel The Brantevik Eel () (Before 1859 - Before 7 August 2014), also known as Åle, was a European ee ...
, a fishing village in southern Sweden.
Conservation status
The European eel is a
critically endangered species.
Since the 1970s, the numbers of eels reaching Europe is thought to have declined by around 90% (possibly even 98%). Contributing factors include
overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in t ...
,
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson h ...
s such as ''
Anguillicola crassus'', barriers to migration such as
hydroelectric
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...
dams, and natural changes in the
North Atlantic oscillation,
Gulf Stream, and
North Atlantic drift. Recent work suggests
polychlorinated biphenyl
Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act of 1976, Toxic Substances Contro ...
(PCB)
pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...
may be a factor in the decline.
TRAFFIC
Traffic comprises pedestrians, vehicles, ridden or herded animals, trains, and other conveyances that use public ways (roads) for travel and transportation.
Traffic laws govern and regulate traffic, while rules of the road include traffic ...
is introducing traceability and legality systems throughout trade change to control the decline and encourage a U-turn on the species. The species is listed in Appendix II of the
CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of intern ...
Convention.
Sustainable consumption
In 2010,
Greenpeace International added the European eel to its "seafood red list", and the Sustainable Eel Group launched the Sustainable Eel Standard.
Breeding projects
As the European eel population has been falling for some time, several projects have been started. In 1997,
Innovatie Netwerk in the Netherlands initiated a project where they attempted to get European eels to breed in captivity by simulating the journey from Europe to the
Sargasso Sea with a
swimming machine for the fish.
The first to achieve some success was DTU Aqua, a part of the
Technical University of Denmark. Through a combination of fresh and salt water, as well as hormones, they were able to breed it in captivity in 2006 and make the larvae survive for 4.5 days after hatching. By 2007, DTU Aqua scientists were able to set a new record where the larvae survived for 12 days by feeding the mother eel with a special
arginine
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...
-enriched diet. At this age the content of the larval
yolk sac
The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...
has been used, the mouth and digestive channel have developed, and it requires feeding. Attempts with various substances failed.
Galathea
''Galathea'' is one of the largest genera of squat lobsters, containing 70 currently recognised species (17 in the Atlantic Ocean, 22 in the Indian Ocean and 43 in the Pacific Ocean). Most species of ''Galathea'' live in shallow waters.
Species ...
3
Åleopdræt.
Retrieved 22 April 2017. Deep water sampling of the presumed habitat of larval European eel in the Sargasso Sea was performed by the
Galathea
''Galathea'' is one of the largest genera of squat lobsters, containing 70 currently recognised species (17 in the Atlantic Ocean, 22 in the Indian Ocean and 43 in the Pacific Ocean). Most species of ''Galathea'' live in shallow waters.
Species ...
3 expedition in 2006–07, in the hope of revealing the likely feeding preference at the early stage. Their results indicated that they feed on various
planktonic organisms, but especially microscopic
jellyfish
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbre ...
.
A follow-up expedition was performed by DTU's own
research ship to the Sargasso Sea region in 2014.
To further the research, the PRO-EEL project, led by DTU Aqua and involving several research institutes elsewhere in Denmark (
University of Copenhagen
The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in ...
and others), Norway (
Norwegian Institute of Fisheries and Food Research and others), the Netherlands (
Leiden University
Leiden University (abbreviated as ''LEI''; nl, Universiteit Leiden) is a public research university in Leiden, Netherlands. The university was founded as a Protestant university in 1575 by William, Prince of Orange, as a reward to the city o ...
and others), Belgium (
Ghent University), France (
French National Center for Scientific Research and others), Spain (ICTA at
Polytechnic University of Valencia
The Technical University of Valencia ( ca-valencia, Universitat Politècnica de València, UPV; , es, Universidad Politécnica de Valencia) is a Spanish university located in Valencia, with a focus on science, technology, and arts. It was founde ...
) and Tunisia (National Institute of Marine Sciences and Technologies), was started in 2010. By 2014, the eel larvae at their facilities typically survive 20–22 days, but the full
life cycle has still not been completed in captivity.
Life history
Much of the European eel's
life history was a mystery for centuries, as fishermen never caught anything they could identify as a young eel. Unlike many other migrating fish, eels begin their life cycle in the ocean and spend most of their lives in fresh inland water, or brackish coastal water, returning to the ocean to spawn and then die. In the early 1900s,
Danish researcher
Johannes Schmidt identified the
Sargasso Sea as the most likely spawning grounds for European eels. The
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e (
leptocephali) drift towards Europe in a 300-day migration.
When approaching the European coast, the larvae metamorphose into a transparent larval stage called "glass eel", enter estuaries, and many start migrating upstream. After entering their continental habitat, the glass eels metamorphose into
elvers, miniature versions of the adult eels. As the eel grows, it becomes known as a "yellow eel" due to the brownish-yellow color of their sides and belly. After 5–20 years in fresh or brackish water, the eels become sexually mature, their eyes grow larger, their flanks become silver, and their bellies white in color. In this stage, the eels are known as "silver eels", and they begin their migration back to the Sargasso Sea to spawn. Silvering is important in an eel's development because it allows for increased levels of the steroid hormone cortisol, which is needed for their migration from fresh water back to the sea. Cortisol plays a role in the long migration because it allows for the mobilization of energy during migration. Also playing a key role in silvering is the production of the steroid 11-Ketotestosterone (11-KT), which prepares the eel for structural changes to the skin to endure the migration from fresh water to saltwater.
Magnetoreception has also been reported in the European eel by at least one study, and may be used for navigation.
Eels May Use 'Magnetic Maps' As They Slither Across The Ocean
/ref>
Eel-life-circle1.svg, Life cycle of the European eel
Glasseelskils.jpg, Glass eels at the transition from ocean to fresh water
FMIB 35739 Anguilla vulgaris -- Anguilla.jpeg, Mature silver-stage European eels migrate back to the ocean
Ecology
Parasites
Parasite species infecting the European eel include '' Bothriocephalus claviceps'' and a range of other intestinal metazoans.
European eels generally have a low parasite diversity within individuals and ecosystems (component community). The parasite that is most commonly dominant is the acanthocephalan '' Acanthocephalus lucii''.
Commercial fisheries
References
External links
*
{{Authority control
Amphibious fish
European eel
Critically endangered animals
European eel
Fish of Europe
Fish of the Baltic Sea
Fish of the Black Sea
Fish of the Mediterranean Sea
Fish of the North Sea
Freshwater fish of Europe
Taxa named by Carl Linnaeus