The geographic range of adult European eels includes the English Channel and coasts of the Mediterranean Sea and northern Atlantic Ocean from Iceland to Mauritania (Ringuet et al., 2002). Their range also encompasses the Baltic and North Seas, as well as all accessible continental or coastal hydrosystems (Ringuet et al., 2002). In the early spring months, European eels migrate to the Sargasso sea for breeding. Larvae are hatched from the Sargasso Sea and can also be found along the coast of Europe. Silver (juvenile) stage eels of Anguilla anguilla live in tributaries along the European coast. (Ringuet, et al., 2002; Ringuet, et al., 2002; Tsukamoto, et al., 1998)
Depending on the lifestage of the individual eel, European eels can be found in marine, freshwater, and brackish aquatic environments. Typically, the European eel is found in depths of 0-700 m, most often on the floor of the ocean or river in which it is living. (Tsukamoto, et al., 1998)
The appearance of European eels varies greatly depending on life stage. As leptocephali, European eels are small, leaflike, and transparent (Deelder, 1970). After metamorphosing into the silver stage, European eels appear silvery in color with elongated dorsal and anal fins that are continuous with the caudal fin (Deelder, 1970). European eels lack pelvic fins (Deelder, 1970). Upon full sexual maturation, European eels develop enlarged eyes, lose their ability to feed, and turn green, yellow or brownish in color (Van Ginniken and Thillhart, 2000). (Van Ginneken and Van Den Thillart, 2000; Deelder, 1970; Van Ginneken and Van Den Thillart, 2000)
Female eels are generally substantially larger than males. The largest recorded mass of a female eel is 6.599 g (Dekker, van Os and van Willigen, 1998). The maximum published length of a European eel was 133 cm. (Dekker, et al., 1998; Dekker, et al., 1998)
European eels begin their life cycle as eggs on the bottom of the Sargasso Sea. They hatch as leptocephali, leaf-like larvae (Tsukamoto, Nakai and Tesch, 1998). After hatching, larvae spend a maximum of one year migrating to Europe, or occasionally North America, via ocean currents. The larvae will then metamorphose into 'glass eels,' the next stage of the life cycle, and enter estuarine areas. Male glass eels contineu to grow for approximately 6 to 12 years; females for 9 to 20 years (Deelder, 1970). After a final metamorphosis, European eels migrate back to the Sargasso Sea to spawn. (Deelder, 1970; Tsukamoto, et al., 1998)
Upon reaching sexual maturity, European eels migrate from freshwater streams back to the Sargasso Sea in order to spawn and die in the late winter months to the early summer months. European eel males release sperm into the water in which female European eels have already laid eggs, thereby fertilizing the eggs (Horie et al., 2004). Very little is known about the actual spawning mechanism, and time to hatching is variable. (Okamura, et al., 2004)
European eels spawn during the late winter to early spring months. There is little information on their reproduction, but since European eels are closely related to Japanese eels, Anguilla japonica, similar breeding patterns might be assumed. Female A. japonica can lay from 2,000,000 to 10,000,000 eggs, but die soon after spawning (Deelder, 1970). Eel larvae are independent from time of birth until time of death. (Deelder, 1970)
European eels invest a substantial amount of energy in reproduction, and die shortly thereafter (Deelder, 1970). Consequently, the only resource that female eels give to their offspring is enough food source to last the egg until hatching. After hatching, the larvae are completely independent and able to find food (Lecomte-Finiger, 1994). (Deelder, 1970; Lecomte-Finiger, 1994)
The lifespan of European eels is dependent on maturation time because once eels mature and spawn, they die. European eels can spawn as early as 7 years old. The maximum reported age of a European eel in the wild is 85 years (Dekker, van Os and van Willigen, 1998). (Dekker, et al., 1998)
European eels are essentially a solitary species. Although numerous eels can be found in a single location, there is no evidence that any form of schooling is present (Suzuki et al, 2003). European eels migrate to various regions during different stages of their life. They transport themselves by actively swimming with ocean currents (Deelder, 1970). European eels are active mainly during the day. (Deelder, 1970; Tsukamoto, et al., 2003)
European eels sense the environment using their sense of taste. They have been shown to locate necessary amino acids via chemotaxis (Sola and Tongiorgi, 1998). European eels also utilize olfaction, most probably for homing purposes. There is little if any documentation of social communication between eels (Deelder, 1970). (Sola and Tongiorgi, 1998; Sola and Tongiorgi, 1998)
European eels have completely different diets during different life stages. No food contents have ever been discovered in the guts of leptocephali, therefore their diet is unknown (Fisheries Global Information System, 2005). Glass eels consume insect larvae, dead fish, and small crustaceans (Sinha and Jones, 1975). Adult eels have a fairly broad diet and eat freshwater, marine, or terrestrial fauna. Their primary food source is aquatic invertebrates, but they will eat essentially any food they can find-- even dead organisms (Sinha and Jones, 1975). European eels are reported to leap out of the water during the winter and feed on terrestrial invertebrates (Deedler, 1970). ("Fisheries Global Information System", 2001; Deelder, 1970; Sinha and Jones, 1975)
European eels are preyed upon by larger eels and other fish and fish-consuming birds, such as cormorants (Phalacrocorax) and herons (Ardeidae) (Deelder, 1970). One defense mechanism employed by eels is that they hide under rocks and burrow in the sand, thus avoiding their predators. The coloring of eels at various life stagies (i.e. the transparency of leptocephali, the dark grey to green color of adults, etc.) also serves as camouflage. (Deelder, 1970)
European eels are both a food source and a predator of organisms in their ecosystem. They are consumed by birds and large predatory fish (Deelder, 1970). European eels also act as a host for the nematode Aguillicola crassus which infects the swim bladders of European eels (Deelder, 1970). European eels distribute nutrients between marine and freshwater ecosystems because they migrate between those habitats (Deelder, 1970). (Deelder, 1970)
European eels are a popular food source for humans, especially in Europe and Asia. The eels also feed on the eggs of predatory fish such as trout, which keep ecosystems from overpopulation (Deelder, 1970). (Deelder, 1970)
European eels thrive on a diet of marine and freshwater fauna, so impact populations of other marine and freshwater organisms (Deelder, 1970). There are no direct adverse effects to humans. (Deelder, 1970)
European eel populations are not currently threatened.
European eels can survive, and even reproduce, at temperatures as low as 0°C. Optimum temperatures for gametogenesis in Anguilla anguilla are between 0°C and 30°C (Deelder, 1970)-- quite a large range! (Deelder, 1970)
Tanya Dewey (editor), Animal Diversity Web.
Melissa Skupin (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
mainly lives in oceans, seas, or other bodies of salt water.
an animal that mainly eats dead animals
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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Lecomte-Finiger, R. 1994. The Early Life of the European Eel. Nature, 370: 424-425.
Okamura, A., H. Zhang, T. Utoh, A. Akazawa, Y. Yamada, N. Horie, N. Mikawa, S. Tanaka, H. Oka. 2004. Artificial hybrid between Anguilla anguilla and A. japonica. Journal of Fish Biology, 64/5: 1450.
Ringuet, S., F. Muto, C. Raymakers. 2002. Eels: Their Harvest and Trade in Europe and Asia. Traffic Bulletin, 19/2: 2-27.
Sinha, V., J. Jones. 1975. The European Freshwater Eel. Liverpool: Liverpool University Press.
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Tsukamoto, K., I. Nakai, W. Tesch. 1998. Do all freshwater eels migrate?. Nature, 396: 635-636.
Tsukamoto, K., T. Otake, N. Mochioka, T. Lee, H. Fricke, T. Inagaki, J. Aoyama, S. Ishikawa, M. Miller, S. Kimura, H. Hasumoto, M. Oya, Y. Suzuki. 2003. Seamounts, new moon and eel spawning: The search for the spawning site of the Japanese eel. Environmental Biology of Fishes, 66: 221-229.
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