Fish
European Eel
Anguilla anguilla · also called European eel, common eel
The European eel has one of the most extreme life stories of any fish. It is born in the middle of the Atlantic, drifts as a transparent sliver to the rivers of Europe, lives there hidden for a decade or more, and then transforms its own body for a single 5,000-kilometre swim back out to sea to breed once and die. That journey has never been witnessed, and the eel is now Critically Endangered.
Overview
Adult European eels live in rivers, lakes, estuaries, ditches, and coastal water across Europe, North Africa, and the Mediterranean. They are nocturnal, secretive carnivores, spending the day buried in mud or hidden under stones and banks, and hunting insects, crustaceans, molluscs, worms, and fish at night. This river phase — the yellow eel — can last 5 to 20 years or more, and an eel that never gets the cue to migrate may live for many decades.
A life in five forms
The eel remakes itself repeatedly:
- Leptocephalus — a flat, clear, leaf-shaped ocean larva
- Glass eel — eel-shaped but transparent, arriving at the coast
- Elver — a small pigmented eel running up rivers
- Yellow eel — the long-lived river resident
- Silver eel — the migratory adult, with a silver belly, enlarged eyes, and a shut-down gut; it never feeds again
The unseen spawning
Every European eel is thought to breed in the Sargasso Sea, near Bermuda. Larvae ride the Gulf Stream back toward Europe over one to three years. Yet in centuries of study no one has observed a European eel spawn, found its eggs, or tracked a wild adult the whole way there — the heart of the life cycle is still a genuine mystery.
Collapse
Since the 1980s, the arrival of young glass eels in Europe has fallen by around 90–98%. The drivers combine: dams and turbines blocking and killing migrants, wetland loss, an introduced swim-bladder parasite, pollutants stored in eel fat, changing ocean currents, and fishing — including a large illegal trade smuggling live glass eels to Asian farms. With slow maturity and a single lifetime spawning, the species rebuilds only slowly.
Status
The European eel is Critically Endangered. It is covered by an EU recovery plan, CITES trade controls, dam-passage requirements, and glass-eel restocking, but recruitment remains near historic lows.
European Eel: common questions
Where do European eels come from?
Every European eel is believed to hatch in the Sargasso Sea, a still, weed-filled region of the western North Atlantic near Bermuda, thousands of kilometres from Europe. The leaf-shaped larvae drift on the Gulf Stream and North Atlantic Current for one to three years until they reach the European continental shelf, where they transform into transparent "glass eels" and push up estuaries and rivers. Remarkably, despite centuries of study, no one has ever seen a European eel spawn, found an eel egg in the wild, or tracked a wild adult all the way to the Sargasso — the spawning itself remains unobserved.
How does the eel change through its life?
It goes through a striking series of forms. It begins as a leptocephalus, a flat, clear, leaf-like larva. Near the coast it becomes a glass eel — eel-shaped but see-through. As it enters fresh water it darkens into an elver, then a yellow-brown "yellow eel," the stage that lives in rivers and lakes for years or decades, hiding by day and hunting at night. When it is finally ready to breed, it turns into a "silver eel" — its belly goes silver-white, its eyes and pectoral fins enlarge for the open ocean, its gut shrinks and it stops eating, and it sets off downstream on a one-way journey of roughly 5,000 kilometres.
Why is the European eel Critically Endangered?
The number of young glass eels arriving in Europe each year has collapsed by around 90 to 98 percent since the 1980s, and the causes stack up. Dams, weirs, and hydropower turbines block or kill migrating eels; wetlands have been drained; a parasitic swim-bladder nematode was introduced from Asia; pollutants accumulate in the eel's fat and may poison it during migration; ocean currents have shifted with climate change; and fishing pressure is heavy, including a large illegal trade that smuggles live glass eels to Asian eel farms. Because the species matures slowly and breeds only once, it recovers very slowly.
Can eels really travel over land?
To a degree, yes. European eels can absorb some oxygen through their skin as long as it stays moist, and they have been observed leaving the water to cross wet grass, work around obstacles, or move between ponds, usually on rainy nights. They cannot make long overland journeys, and the old belief that eels routinely march across fields is exaggerated, but short damp-weather excursions are real and help explain how eels turn up in isolated ponds with no stream connection.