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Eel
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Eel

The Anguillidae family of freshwater eels is comprised of approximately 22 different species around the world.

Eels of the genus Anguilla are described as a catadromous fish, meaning that they spawn in salt water and metamorphose into glass eels when they reach the continental shelf. After the glass eel stage, they become pigmented and colonize freshwater systems. In the fall, they begin their sexual maturation and begin an epic migration during which they may swim 6,000 km back to the Sargasso Sea, where they will spawn.

Eels have a complex life cycle during which they migrate between freshwater and brackish (semi-catadromous behavior). Analyses of otoliths from the European eel (Anguilla anguilla), and also from other eel species in the world, reveal that some eels skip the freshwater phase. In Norway, eels appear to live predominantly in salt and brackish water.

Other individuals are able to alternate between waters that have completely different salinity, temperature, substrate, depth, and other environmental conditions. It is unclear what determines the eel’s life strategy, but the decision to migrate does not appear to have anything to do with gender, since both males and females display this migration flexibility. One hypothesis is that differences in productivity between river and saltwater areas influence the eel’s decision to move between salt and fresh water habitats (facultative diadromous behavior). Primary production in freshwater is often higher at lower latitudes than at higher latitudes. Therefore, eels tend to remain in brackish and salt water environments at higher latitudes, since in these areas migration into freshwater habitats is not as advantageous.
 

Facts about eel

Latin name: Anguilla anguilla
Genus: Anguilla
Maximum size: 133 cm 6 599 g
Lifespan: Variable, depends upon gender and environmental conditions. Typically 5–20 years
Distribution: From Africa/Canary Islands to Murmansk
Main spawning area: Sargasso Sea
Spawning season: Uknown, but likely March-June. The eel is a one-time spawner
Diet: Carnivorous, eating more-or-less everything
Distinctive features: Eel is strongly negatively phototactic (light averse). They can survive out of water for more than 24 hours and can move over land from freshwater to the sea at the beginning of their spawning migration.

Map of distribution

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