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!
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).
Perception Channels: visual ; tactile ; chemical
European eel populations are not currently threatened.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: critically endangered
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.
Development - Life Cycle: metamorphosis
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.
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).
Positive Impacts: food ; controls pest population
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).
Commensal/Parasitic Species:
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).
Animal Foods: fish; eggs; carrion ; insects; mollusks; terrestrial worms; aquatic or marine worms; aquatic crustaceans; zooplankton
Other Foods: detritus
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Molluscivore , Eats other marine invertebrates, Scavenger )
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.
Biogeographic Regions: palearctic (Native ); atlantic ocean (Native ); mediterranean sea (Native )
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.
Range depth: 0 to 700 m.
Habitat Regions: saltwater or marine ; freshwater
Aquatic Biomes: benthic ; coastal ; brackish water
Other Habitat Features: estuarine
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).
Range lifespan
Status: wild: 85 (high) years.
Typical lifespan
Status: wild: 7 (low) years.
Average lifespan
Status: captivity: 55.0 years.
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).
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.
Range mass: 6,599 (high) g.
Range length: 133 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Mating System: polygynandrous (promiscuous)
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.
Breeding interval: European eels breed only once during their lifetime. Once spawning is complete, European eels die .
Breeding season: European eels spawn in late winter to early spring.
Range number of offspring: 2,000,000 to 10,000,000.
Range age at sexual or reproductive maturity (female): 9 to 20 years.
Range age at sexual or reproductive maturity (male): 6 to 12 years.
Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning; oviparous
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).
Parental Investment: no parental involvement; pre-fertilization (Provisioning)
