European Eel

The European Eel (Anguilla anguilla) is a catadromous fish of the family Anguillidae, native to rivers, lakes, and coastal waters across Europe, and parts of North Africa and the Mediterranean. Like its American counterpart, it spends most of its life in fresh or brackish water before making a single long migration to the Sargasso Sea to spawn and die. Its life cycle passes through leptocephalus larva, glass eel, elver, yellow eel, and silver eel stages, each visually distinct. Once one of Europe's most abundant fish, the species has suffered a dramatic population collapse of over 90% since the 1980s due to river barriers, habitat loss, and disrupted ocean currents, and is now classified as Critically Endangered, with strict international trade regulations in place.

European Eels have a long, cylindrical, snake-like body with smooth-looking skin and tiny embedded scales that are not visible to the naked eye.

Key field marks:

• A single continuous fin running along the back, around the tail tip, and along the underside, with no clear separation between dorsal, caudal, and anal fins
• Small rounded pectoral fins; no pelvic fins present
• Yellow-brown to olive-green coloration in the freshwater yellow eel stage, shifting to a dark back with a silvery-white belly in the migratory silver eel stage
• Pointed head with small eyes that enlarge noticeably just before the silver-eel migration begins

Typical adult length is 60-100 cm. It is virtually indistinguishable from the American eel except by vertebral counts or DNA testing.

European Eels begin life as larvae in the Sargasso Sea, drifting for roughly one to three years on ocean currents toward Europe and North Africa before entering estuaries as glass eels. Juveniles and adults then occupy an extremely broad range of freshwater and brackish habitats, rivers, canals, lakes, ponds, and coastal marshes, from Scandinavia and Iceland south to Morocco and across the Mediterranean and Baltic basins. They favor soft, muddy, or vegetated bottoms offering cover, and can tolerate a wide range of salinities and oxygen levels. Mature silver eels eventually leave these inland waters entirely and travel thousands of kilometers back across the Atlantic to spawn in the Sargasso Sea.

European Eels are largely nocturnal, sheltering by day in burrows, under rocks, or in dense vegetation and emerging at night to feed on invertebrates, small fish, and carrion. They are highly tolerant of varied conditions and can even move briefly overland across wet grass to reach new water bodies. After years of growth, often a decade or more, eels transform into the large-eyed, silver-flanked silver eel stage and begin a single, one-way migration to the Sargasso Sea, where they spawn and die without returning. This unusual catadromous life history, combined with habitat fragmentation from dams and weirs, has made the species a major focus of European conservation efforts and fish-passage restoration projects.