European eel

The European eel (Anguilla anguilla)[2] 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. [3][4][5]

European eel
Anguilla anguilla
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Genus: Anguilla
Species:
A. anguilla
Binomial name
Anguilla anguilla
Eel inEurope
Range for wild European eel
Synonyms

Muraena anguilla Linnaeus, 1758
Anguilla malgumora Kaup, 1856

Conservation status

The European eel is a critically endangered species.[1] Since the 1970s, the numbers of eels reaching Europe is thought to have declined by around 90% (possibly even 98%). Contributing factors include overfishing, parasites such as Anguillicola crassus, barriers to migration such as hydroelectric dams, and natural changes in the North Atlantic oscillation, Gulf Stream, and North Atlantic drift. Recent work suggests polychlorinated biphenyl (PCB) pollution may be a factor in the decline. [6] TRAFFIC is introducing traceability and legality systems throughout trade change to control the decline and encourage a U-turn on the species.[7]

Sustainable consumption

In 2010, Greenpeace International added the European eel to its "seafood red list", [8] and the Sustainable Eel Group launched the Sustainable Eel Standard.[9]

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 6,500 km (4,000 mi) journey from Europe to the Sargasso Sea with a swimming machine for the fish.[10][11]

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.[12] 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-enriched diet.[13] At this age the content of the larval yolk sac has been used, the mouth and digestive channel have developed, and it requires feeding. Attempts with various substances failed.[14] Deep water sampling of the presumed habitat of larval European eel in the Sargasso Sea was performed by the Galathea 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.[14] A follow-up expedition was performed by DTU's own research ship to the Sargasso Sea region in 2014.[15]

To further the research, the PRO-EEL project, led by DTU Aqua and involving several research institutes elsewhere in Denmark (University of Copenhagen and others), Norway (Norwegian Institute of Fisheries and Food Research and others), the Netherlands (Leiden University and others), Belgium (Ghent University), France (French National Center for Scientific Research and others), Spain (ICTA at Polytechnic University of Valencia) and Tunisia (National Institute of Marine Sciences and Technologies), was started in 2010.[16][17] 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.[18]

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. [19] The larvae (leptocephali) drift towards Europe in a 300-day migration.[20]

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.

Magnetoreception has also been reported in the European eel by at least one study, and may be used for navigation. [21]

Eel-life-circle1

Lifecycle of the European eel

Glasseelskils

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

Commercial fisheries

Wild capture of Anguilla anguilla
↑  Wild capture, 1950–2010 [22]
Farmed production of Anguilla anguilla
↑  Farmed production, 1950–2010 [22]
Total production of Anguilla anguilla
↑  Total production of European eel in thousands of tonnes as reported by the FAO, 1950–2010[22]
European eel farming
↑  Main European countries producing farmed European eel

References

  1. ^ a b Jacoby, D. & Gollock, M. (2014). "Anguilla anguilla". The IUCN Red List of Threatened Species. IUCN. 2014: e.T60344A45833138. doi:10.2305/IUCN.UK.2014-1.RLTS.T60344A45833138.en. Retrieved 3 January 2018.
  2. ^ "Anguilla anguilla". Integrated Taxonomic Information System. Retrieved 11 March 2006.
  3. ^ "World's oldest eel dies in Swedish well". The Local. 8 August 2014.
  4. ^ "Anguilla anguilla (Linnaeus, 1758) European eel". FishBase. fishbase.org. Retrieved 3 January 2017.
  5. ^ Deelder, C.L. (1984). "SYNOPSIS OF BIOLOGICAL DATA ON THE EEL Anguilla anguilla (Linnaeus, 1758)" (PDF). www.fao.org. FOOD AND AGRICULTURE ORGAMZATION OF THE UNITED NATIONS. p. 12. Retrieved 3 January 2017.
  6. ^ "PCBs are killing off eels". New Scientist. 2452: 6. 2006.
  7. ^ "Other Aquatic species - Species we work with at TRAFFIC". www.traffic.org. Retrieved 2019-01-10.
  8. ^ Greenpeace International Seafood Red list Archived April 10, 2010, at the Wayback Machine
  9. ^ Sustainable Eel Standard
  10. ^ EOAS magazine, september 2010
  11. ^ Innofisk Volendam breedign project
  12. ^ Ritzau (6 July 2006). Danske forskere får ål til at yngle udenfor Sargassohavet. Politiken. Retrieved 22 April 2017.
  13. ^ Nywold, M. (5 October 2007). Dansk forskergennembrud kan sikre ålens overlevelse. Ingeniøren. Retrieved 22 April 2017.
  14. ^ a b Galathea 3: Åleopdræt. Retrieved 22 April 2017.
  15. ^ DTU (6 November 2014). Danish Eel Expedition 2014. Retrieved 22 April 2017.
  16. ^ PRO-EEL: Partners. Retrieved 22 April 2017.
  17. ^ Wageningen University and Research: PRO-EEL: Reproduction of the European eel: Towards a self-sustaining aquaculture. Retrieved 22 April 2017.
  18. ^ Borup, A.T. (13 December 2014). Ålens kode skal knækkes i Hirtshals. Nordjyske. Retrieved 22 April 2017.
  19. ^ Schmidt, J. (1912) Danish researches in the Atlantic and Mediterranean on the life-history of the Fresh-water Eel (Anguilla vulgaris, Turt.). Internationale Revue der gesamten Hydrobiologie und Hydrographie 5: 317-342.
  20. ^ "FAO Fisheries & Aquaculture Anguilla anguilla". Fao.org. 2004-01-01. Retrieved 2012-08-02.
  21. ^ Eels May Use 'Magnetic Maps' As They Slither Across The Ocean
  22. ^ a b c Based on data sourced from the FishStat database Archived November 7, 2012, at the Wayback Machine, FAO.

External links

Angling records of Europe

This list is of the heaviest European freshwater fish caught using the traditional angling method of rod and line.

The criteria for inclusion on this list is that the species, weight, date and venue have been published by a recognized publisher with a genuine photograph and a link to that publication is referenced here. The list is intended to include all categories of coarse and game fish caught by sport anglers.

Anguillicoloides crassus

Anguillicoloides crassus is a parasitic nematode worm that lives in the swimbladders of eels (Anguilla spp.) and appears to spread easily among eel populations after introduction to a body of water. It is considered to be one of the threats to the sustainability of populations of European eel (Anguilla anguilla). It was introduced to the European continent in the 1980s, where it was reported independently from Germany and Italy in 1982, having probably been introduced from Taiwan. It is thought to have reached England in 1987 from continental Europe. It is a natural parasite of the Japanese eel in its native range.

The life cycle of Anguillicoloides crassus begins when the adult nematode releases thousands of eggs in the eel's swimbladder. The eggs pass through the eel's digestive tract and the larvae emerge in the water and settle onto the substrate. They are ingested by their intermediate host, which is often a copepod or other crustacean but may also be a fish. The nematode larva reaches its infective stage within this intermediate host. The host is eaten by an eel, and the nematode finds its way from the eel's digestive tract to its swimbladder. An eel with an advanced parasite load shows symptoms such as bleeding lesions and swimbladder collapse. The eel becomes more susceptible to disease, its rate of growth slows, and if the infestation is severe enough, it may die. Since the swimbladder is the buoyant organ which allows the eel to swim, a severe parasite infestation can hamper its ability to reach its spawning grounds.

The state of being colonized by Anguillicola nematodes is termed anguillicolosis.

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.

Brantevik Eel

The Brantevik Eel (Swedish: Branteviksålen) 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 in 1859 by an eight-year-old boy, Samuel Nilsson. On 7 August 2014, the eel was reported to have died and sent to an expert who determined the eel's actual age to be over 150 years.The eel's head, presumed lost, was recovered later in a fridge. SVT's nature show Mitt i naturen extracted the eel from the well at one point, but eventually released it.

Dana (1919)

Dana was a four-masted motor schooner build for the Danish East Asiatic Company (EAK) and launched in 1919.. It was made available to the Danish marine biologist Johannes Schmidt, who used it for two expeditions to the Sargasso Sea in 1920-1921. The main goal of the expeditions, named the first and second Dana expeditions, was searching for the spawning grounds of the European eel.

The ship was returned to service in EAK after the expeditions and sold to Sweden in 1924, where it was renamed to Carina. Later sold to Italy (1934) and renamed to Guiseppina V. Lost 30th of August 1941 during the bombing of TripoliDana was succeeded by the research vessel Dana (II).

Dana (1937)

Dana III was the primary Danish research vessel for almost 40 years. It was build in 1937 and served research purposes until 1980.

On the first cruise into the North Atlantic in 1938 it was discovered that the ship was unsuited for its purpose, as it was not sufficiently stable to allow scientific work. It was returned to the shipyard and extended by 8 meter in 1939. During the second world war (1940-1945) the ship was kept and maintained in Copenhagen harbour, but with vital engine parts removed and thus never seized by the German occupation force.

The main work from Dana III was to conduct marine biological and hydrographical research in the Baltic, North Sea and waters around Faroe Islands and Greenland.

In 1966 Dana III was on a cruise to the Sargasso Sea and West Indies (cruise leader Erik Berthelsen), with primary aims to conduct hydrographical research and continue research on the reproductive biology of the European eel.

Dana (III) was succeeded by the research vessel Dana (IV) in 1980. The ship served for a period as guard and crew exhange vessel for oil and gas installations in the North Sea and was eventually sold to P&T Charters. It was completely refurbished, rigged as a 3-masted schooner under the name of Gulden Leeuw and continues to sail as a charter vessel.

Eel

An eel is any ray-finned fish belonging to the order Anguilliformes (), which consists of four suborders, 20 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage, and most are predators. The term “eel” originally referred to the European eel, and the name of the order means “European eel-shaped.”

The term “eel” is also used for some other eel-shaped fish, such as electric eels (genus Electrophorus), spiny eels (family Mastacembelidae), and deep-sea spiny eels (family Notacanthidae). These other clades, however, evolved their eel-like shapes independently from the true eels.

Eel life history

The eel is a long, thin bony fish of the order Anguilliformes. Because fishermen never caught anything they recognised as young eels, the life cycle of the eel was a mystery for a very long period of scientific history. Although more than 6500 publications mention eels, much of their life history remains an enigma.

The European eel (Anguilla anguilla) was historically the one most familiar to Western scientists, beginning with Aristotle, who wrote the earliest known inquiry into the natural history of eels. He speculated that they were born of "earth worms", which he believed were formed of mud, growing from the "guts of wet soil" rather than through sexual reproduction. Many centuries passed before scientists were able to demonstrate that such spontaneous generation does not occur in nature.

Other early scientists believed that the eelpout Zoarces viviparus was the "mother of eels" (the translation of the German name "Aalmutter").

Fauna of North Macedonia

The fauna of the Republic of Macedonia has a complex zoogeographical structure. It contains faunal elements of different origins and is characterized by a high degree of relict and endemic forms. Taxonomic diversity is also present; the total number of animal species reported until now is 10,354.

The fauna of Macedonian forests is abundant and includes bears, wild boars, wolves, foxes, squirrels, chamois and deer. The lynx is found, although very rarely, in the mountains of western Macedonia, while deer can be found in the region of Demir Kapija. Forest birds include the blackcap, the grouse, the black grouse, the imperial eagle and the forest owl.

The three natural lakes of the country represent a separate faunal zone, an indication of long-lasting territorial and temporal isolation. The fauna of Lake Ohrid is a relic of an earlier era and the lake is widely known for its letnica trout, lake whitefish, gudgeon, roach, podust, and pior, as well as for certain species of snails of a genus older than 30 million years; similar species can only be found in Lake Baikal. Lake Ohrid is also noted in zoology texts for the European eel and its baffling reproductive cycle: it comes to Lake Ohrid from the distant Sargasso Sea, thousands of kilometres away, and lurks in the depths of the lake for 10 years. When sexually mature, the eel is driven by unexplained instincts in the autumn to set off back to its point of birth. There it spawns and dies, leaving its offspring to seek out Lake Ohrid to begin the cycle anew.

Fish farming

Fish farming or pisciculture involves raising fish commercially in tanks or enclosures such as fish ponds, usually for food. It is the principal form of aquaculture, while other methods may fall under mariculture. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, tilapia, salmon, and catfish.Demand is increasing for fish and fish protein, which has resulted in widespread overfishing in wild fisheries. China provides 62% of the world's farmed fish. As of 2016, more than 50% of seafood was produced by aquaculture.Farming carnivorous fish, such as salmon, does not always reduce pressure on wild fisheries. Carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tonnes worth about $US 60 billion.

Goksjø

Goksjø is a lake in the municipalities of Sandefjord, Larvik and Andebu in Vestfold county, Norway. Goksjø is 5 km from north to south, and has a circumference of 20 km. At its deepest, Goksjø is no deeper than 26 meters. Goksjø has an elevation of 28 meters above sea level. It is the largest lake in Sandefjord, and the third-largest in Vestfold County. It is surrounded by rural agricultural lands, and flooding occurs on a regular basis.

The lake is used for ice-skating, canoeing, swimming, fishing, and other recreational activities.

The name derives from Gautsjór from the male name Gautr, which may have become Gok.

Both draining rivers and inlets are located on the lake’s northern shore. Storelv and Skorgeelva (Trollsåselva) are the two most important inlets. It is drained solely by Hagneselva, which flows into Åsrumvannet and eventually into Numedalslågen. Its most important inlet is the river Storelv, which flows from Askimvannet in Andebu.Fish species found here include Northern pike, European perch, Ide, Common dace, European eel, Salmon and Brown trout.

Grungstadvatnet

Grungstadvatnet is a lake in the municipality of Høylandet in Trøndelag county, Norway. There are salmon, sea trout, european eel, trout, and Arctic char in the lake. The 6.71-square-kilometre (2.59 sq mi) lake lies just to the north of the large lake Eidsvatnet.

Principle of Priority

Priority is a fundamental principle of modern botanical nomenclature and zoological nomenclature. Essentially, it is the principle of recognising the first valid application of a name to a plant or animal. There are two aspects to this:

The first formal scientific name given to a plant or animal taxon shall be the name that is to be used, called the valid name in zoology and correct name in botany.

Once a name has been used, no subsequent publication of that name for another taxon shall be valid (zoology) or validly published (botany).There are formal provisions for making exceptions to this principle. If an archaic or obscure prior name is discovered for an established taxon, the current name can be declared a nomen conservandum (botany) or conserved name (zoology), and so conserved against the prior name. Similarly, if the current name for a taxon is found to have an archaic or obscure prior homonym, the current name can be declared a nomen protectum (zoology) or the older name suppressed (nomen rejiciendum, botany).

River Allen (Truro)

The River Allen (Cornish: Dowr Alen, meaning shining river), or St Allen River, to the north of Truro is one of two watercourses in Cornwall which share this name.

The River Allen rises at Ventoneage (Cornish: Fentenyk, meaning little spring) north of St Allen and flows southwards through the Idless Valley into Truro. Here it joins the River Kenwyn to form the Truro River.

The river is home to healthy populations of Brown Trout (Salmo trutta), European Eel (Anguilla anguilla), Minnow (Phoxinus phoxinus) and Bullhead (Cottus gobio) also known as the ‘Miller’s Thumb. The lower tidal reaches also hold Bass (Dicentrarchus labrax), Grey Mullet (Chelon labrosus), and Flounder (Platichthys flesus). There is also a small run of Sea Trout (migratory Salmo trutta) into the river.

River Truro

The Truro River is a river in the city of Truro in Cornwall, England, UK. It is the product of the convergence of the two rivers named Kenwyn and Allen which run under the city: the Truro River (named after the city) flows into the River Fal, estuarial waters where wildlife is abundant, and then out into the Carrick Roads. The river is navigable up to Truro.

The river valleys form a bowl surrounding the city on the north, east and west and open to the Truro River in the south. The fairly steep-sided bowl in which Truro is located, along with high precipitation swelling the rivers and a spring tide in the River Fal, were major causes of flooding in 1988 which caused large amounts of damage to the city centre. Since then, flood defences have been constructed around the city, including an emergency dam at New Mill on the River Kenwyn and a tidal barrier on the Truro River, to prevent future problems. The valley of the Tresillian River is between the valleys of the Truro River and the Fal; the Tresillian River flows into the Truro River just upstream of where the latter joins the Fal. Early records give the Tresillian River the name "Seugar" (1297) or "Sowgar" (1530); the meaning of this name is unknown.

Sandoz chemical spill

The Sandoz chemical spill was a major environmental disaster caused by a fire and its subsequent extinguishing at Sandoz agrochemical storehouse in the Schweizerhalle industrial complex, Basel-Landschaft, Switzerland, on 1 November 1986, which released toxic agrochemicals into the air and resulted in tons of pollutants entering the Rhine river, turning it red.The chemicals caused a massive mortality of wildlife downstream, killing among other things a large proportion of the European eel population in the Rhine, although the situation subsequently recovered within a couple of years.

Thor (1903)

Thor was a Danish research vessel from 1903 to 1927. It was build in Newcastle in 1899 as a steam trawler. Thor conducted hydrographical and oceanographical research in the North Atlantic and the Mediterranean and helped locate the spawning grounds of the Icelandic cod. Most importantly, Thor conducted two expeditions to the Mediterranean Sea in 1908-1910 with Johannes Schmidt as cruise leader. The aim of the expeditions, funded by the Carlsberg Foundation, was to locate the spawning grounds of the European eel. Contrary to their expectations the expeditions found that fewer eel larvae (leptocephals) were found the deeper they went into the Mediterranean, but they also grew larger. The logical conclusion was that the spawning grounds were not in the Mediterranean, but in the Atlantic Ocean.

In a broader perspective the largest result from the two expeditions was the very large contribution to the general understanding of the oceanography and pelagic fauna of the Mediterranean.

Vegår

Vegår is a lake in the municipality of Vegårshei in Aust-Agder county, Norway. The 17.7-square-kilometre (6.8 sq mi) lake is located about 3 kilometres (1.9 mi) north of the municipal center of Myra and about 12 kilometres (7.5 mi) east of the village of Åmli in the neighboring municipality of Åmli.The three largest parts of the lake are named Vestfjorden, Nordfjorden, and Sørfjorden. The deepest point of the lake, in the Nordfjorden area, reaches 102 metres (335 ft) below the surface of the water. There are many small islands in the lake, the largest of which is Furøya. The primary exit for the water in the lake is through the river Storelva which flows south through the village of Myra to Nesgrenda in Tvedestrand municipality before turning northeast and flowing into the sea at the Sandnesfjorden.Vegår supports one of the country's most long-lived and stable beaver populations, as well as a fish fauna consisting of European perch, brown trout, Arctic char, and European eel.

Årungen

Årungen is a lake in Norway in the municipality of Ås about 18 miles (29 km) south of Oslo which is notable for being an environment containing microscopic creatures called collodictyons. Norwegian scientists have been studying the creatures for two decades and speculate that they may be one of the oldest known organisms, and may provide clues about the origins of life. One kilometre south of the lake lies the Norwegian University of Life Sciences.

The lake's elevation is 33 meters above sea level and it straddles both Ås and Frogn municipalities of Akershus county. The surface area is 1.2 square kilometres (0.46 sq mi). Its drainage basin is Østensjøvannet and a number of minor streams. It drains into Årungselva river northward to Bunnefjorden. The eastern shore of the lake has been adapted with strolling paths and picnic areas.

The water is shallow and rich with nutrients, and inflow from agriculture annually causes blooms of toxic blue-green algae. Nevertheless the lake is rich in fish life, with northern pike, European perch, Common Roach and European eel. The water quality has improved in recent years. The wetlands in the southern end is an important part of the local fauna and flora.

Årungen is also home to the Norwegian national center for rowing and paddling. Årungen was host to the 1993 World Rowing Junior Championships.

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