The European eel (Anguilla anguilla) is a species of eel. They are critically endangered due to overfishing by fisheries on coasts for human consumption and parasites.
Di
DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
Ca
CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
Sc
ScavengerScavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While sc...
Mo
MolluscivoreA molluscivore is a carnivorous animal that specializes in feeding on molluscs such as gastropods, bivalves, brachiopods, and cephalopods. Known mo...
In
InsectivoresAn insectivore is a carnivorous plant or animal that eats insects. An alternative term is entomophage, which also refers to the human practice of e...
Co
CongregatoryCongregatory animals tend to gather in large numbers in specific areas as breeding colonies, for feeding, or for resting.
Ov
OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
Po
PolygynandryPolygynandry is a mating system in which both males and females have multiple mating partners during a breeding season.
Mi
MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
Ca
CatadromousE
starts withEuropean eels are normally around 45–65 centimetres (18–26 in) and rarely reach more than 1.0 metre (3 ft 3 in), but can reach a length of up to 1.33 metres (4 ft 4 in) in exceptional cases. In addition, they range from having 110 to 120 vertebrae. While European eels tend to live approximately 15–20 years in the wild, some captive specimens have lived for over 80 years. A specimen known as "the Brantevik Eel" lived for 155 years in the well of a family home in Brantevik, a fishing village in southern Sweden.
Eels tend to range from 0 to 700 meters underwater and after spawning in the Sargasso Sea, disperse North throughout the Atlantic Ocean, its coasts, and the rivers that empty into it. Feeding occurs mainly at night, via scent and prey consists of worms, fish (including ones too big to eat without biting off chunks), mollusks such as slugs, crustaceans such as crayfish, and plankton on occasion when it's populous in large quantities. European eels are preyed upon by bigger eels, herons, cormorants, and pike. Seagulls also prey on elvers. Eels usually find and compete for shelter by hiding in plants or tube-shaped crevices in rocks. They also hide in muddy fields when inland.
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 larvae (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.
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, 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. TRAFFIC is introducing traceability and legality systems throughout trade change to control and reverse the decline of the species. The species is listed in Appendix II of the CITES Convention.
