Quick answer
Freshwater eels are catadromous — they live in rivers but breed at sea. European and American eels migrate thousands of kilometres to the Sargasso Sea in the western Atlantic to spawn, then die. The eggs hatch into transparent larvae that drift on ocean currents for months before returning to rivers as glass eels. The actual spawning has never been directly filmed.
Key takeaway
Freshwater eels are catadromous — they live in rivers but breed at sea. European and American eels migrate thousands of kilometres to the Sargasso Sea in the western Atlantic to spawn, then die. The eggs hatch into transparent larvae that drift on ocean currents for months before returning to rivers as glass eels. The actual spawning has never been directly filmed.
Overview
Freshwater eels are catadromous — they live in rivers but breed at sea. European and American eels migrate thousands of kilometres to the Sargasso Sea in the western Atlantic to spawn, then die. The eggs hatch into transparent larvae that drift on ocean currents for months before returning to rivers as glass eels. The actual spawning has never been directly filmed.
Biology
European Eel (Anguilla anguilla (European eel)) is classified as Fish with conservation status Critically Endangered. Typical weight about 2.5 kg; lifespan around Up to 20+ years in rivers; dies after spawning.
Ecology
Diet: Carnivore (fish, worms, crustaceans). Habitat: Rivers, estuaries, and the open Atlantic Ocean. Movement and social systems reflect those pressures.
People and this species
Learn before you travel or keep related pets. Wild individuals are not toys; captive care needs species-specific husbandry.
Further reading
See the full European Eel profile for FAQs, taxonomy, and related guides on this site.
Where do eels reproduce?
Both the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata) spawn in the Sargasso Sea — a current-bounded region of the western Atlantic, bounded by the Gulf Stream to the west and the North Atlantic Current to the north. Danish biologist Johannes Schmidt traced eel larvae to this region in the 1920s by following progressively smaller larvae westward. In 2022, satellite tagging of adult European eels provided the first direct evidence of adult eels actually reaching the Sargasso Sea, confirming a migration of 5,000 to 10,000 km from European rivers.
The four life stages of an eel
Freshwater eels pass through four distinct stages. The leptocephalus is a transparent, leaf-shaped larva that drifts on ocean currents for 6 to 12 months. It then transforms into the glass eel — a tiny, see-through juvenile that arrives at coastlines and moves upstream into rivers. In rivers it becomes the yellow eel, the main feeding and growing stage lasting 10 to 20 years. Finally, as the reproductive drive activates, it transforms into the silver eel — sleek, silvery, with enlarged eyes and a fatty body — and migrates back to the sea to spawn once and die.
Why was it such a mystery?
For over two millennia, eel reproduction baffled observers. Aristotle believed eels arose spontaneously from mud. Sigmund Freud spent a frustrating period dissecting hundreds of eels trying to find their reproductive organs, without success. The reason is that eel gonads only fully develop during the final migration — the organs that would confirm sex do not exist in yellow eels at a mature stage. No one has ever filmed wild eels spawning, and no eel eggs have been found at the surface. Our understanding is entirely built from larvae, tracking data, and inference.
Research notes
Figures for european eels (Anguilla anguilla (European eel)) come from field studies, museum records, and conservation assessments that do not always agree on exact averages. Prefer ranges over single-point claims, and check whether a source describes wild, captive, or mixed populations.
Practical takeaways
If you encounter european eels in the wild, prioritise distance and local guidance. If you care for related domestic or captive animals, match diet and housing to species needs rather than generic pet advice. Share accurate status information (Critically Endangered) when discussing conservation.
Sources
FAQs
European Eel: Key Facts & Natural History?
Freshwater eels are catadromous — they live in rivers but breed at sea. European and American eels migrate thousands of kilometres to the Sargasso Sea in the western Atlantic to spawn, then die. The eggs hatch into transparent larvae that drift on ocean currents for months before returning to rivers as glass eels. The actual spawning has never been directly filmed.
What is the scientific name of the european eel?
Anguilla anguilla (European eel)
What do european eels eat?
Carnivore (fish, worms, crustaceans)
Where do european eels live?
Rivers, estuaries, and the open Atlantic Ocean
Are european eels endangered?
Listed here as Critically Endangered. Check IUCN and national lists for the latest assessment.