European eel
Anguilla anguilla
The European eel is a catadromous migratory fish characterized by its distinct, snake-like body shape. It spends its growth phase in European inland waters and coastal areas before undertaking an impressive spawning migration of over 6,000 kilometers to the Sargasso Sea. Key features include its slimy skin, a continuous fin fringe, and a prominent lower jaw. Throughout its life cycle, it undergoes several stages from leptocephalus larva to glass eel and finally to the sexually mature silver eel.
Details
Identification
Snake-like body, dorsal, caudal, and anal fins form a continuous fringe, lower jaw longer than upper jaw, very small scales.
Social behavior
Predominantly solitary; only forms larger aggregations during migration phases.
Diet
Opportunistic carnivore; feeds on insect larvae, crustaceans, mollusks, and small fish.
Hunting strategy
Nocturnal searching on the water bottom using an intensive and highly sensitive sense of smell.
Spawning substrate
Pelagic in the deep waters of the Sargasso Sea (open water spawner).
Overwintering
Burrows into the sediment when water temperatures drop below 7-10 °C and enters a phase of inactivity.
Ecology
Ecological role
Important benthic predator and significant transporter of biomass between marine and limnic ecosystems.
Natural predators
Pike, catfish, cormorants, grey herons, and otters; juvenile stages also by perch and trout.
Competitor species
Other benthic predatory fish such as burbot or catfish.
Ecosystem service
Regulation of invertebrate populations and historical importance as a high-quality protein source for humans.
Threats
Migration barriers (dams), mortality in hydropower turbines, overfishing (esp. glass eels), parasites (swim bladder worm), and chemical pollution.
Scientific profile
Morphology & ID
Coloration
Back dark green to blackish-brown, belly yellowish (yellow eel) or silvery-white (silver eel).
Distinguishing features
Lower jaw protruding; dorsal, caudal, and anal fins form a continuous fringe; very small scales.
Confusion species
European conger (Conger conger) - which has a protruding upper jaw.
Sexual dimorphism
Significant size difference: females up to 150 cm, males rarely exceed 50 cm.
Habitat
Fish region
Eurytopic (found in almost all regions, focus on the bream zone).
Preferred zone
Benthic (bottom-dwelling).
Flow preference
Limnophilous to rheophilous (eurytopic).
Substrate preference
Mud, sand, crevices between stones or roots.
Oxygen requirement
Low; capable of cutaneous respiration (absorbing oxygen through the skin).
Migration
Migration behaviour
Catadromous; migrates from freshwater bodies to the Sargasso Sea (Western Atlantic) for spawning.
Reproduction
Spawning substrate
Pelagic in the open waters of the Sargasso Sea at great depths.