Species of the day one hundred and eight: European Eel (Anguilla anguilla)
Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Genus: Anguilla
Species: Anguilla anguilla
Description: Adult European Eels have long, narrow bodies, with a continuous dorsal, anal and tail-fin . The skin is slimy, the lower jaw is longer than the upper jaw, the scales are tiny or absent. The colour of adults depends on their age; they are often brown, black or olive-green with yellowish bellies. Some adults may be silvery (known as ‘silver eels’); the lifecycle stages differ greatly in appearance. Adult individuals may reach a maximum length of 1 m.
Habitat and Distribution: The European Eel varies its habitat dependent on life cycle stage, part is spent in the sea, and part in freshwater rivers. The species is often seen on the shore. Found in the rivers of the North Atlantic, Baltic and Mediterranean Seas; the European Eel also occurs along European coasts from the Black Sea to the White Sea in Russia. Spawning takes place in the Sargasso Sea in the western Atlantic.
Biology and Ecology: The European Eel has a fascinating life-cycle; it is a ‘catadromous’ species, breeding in the sea and migrating to freshwater in order to grow before returning to the sea to spawn. It is thought that all European Eels spawn in the Sargasso Sea. The larvae, which look like curled leaves and are known as ‘leptocephalli’, drift in the plankton for up to three years, and are carried by the Gulf Stream towards the coasts of Europe . They then undergo metamorphosis into young eels; at this stage they are known as ‘glass eels’ because they are transparent. They become darker in colour and start to migrate up freshwater streams in large numbers; they are known as ‘elvers’ at this time and measure around 50 millimetres in length. The eels, now called ‘brown’ or ‘yellow eels’ grow in freshwater, with males and females spending 6 to 12 and 9 to 20 years in freshwater, respectively. Towards the end of this time, they become sexually mature; they turn a silvery colour and migrate back towards the sea on dark, moonless and stormy nights; during this time they are known as ‘silver eels’. Upon returning to the sea, the European Eel lives in mud, crevices, and under stones. Spawning occurs during winter and early spring in the Sargasso Sea. This is a very long-lived species with a maximum life span of 85 years. This eel is predated upon by birds, including cormorants and gulls, as well as a number of species of fish. Remarkably, they can survive out of water for several hours on damp nights; they may travel overland on dark rainy nights.
Status and Threats: The European Eel is classified as Critically Endangered under the IUCN Redlist. The population of the European Eel is threatened at present, and eel stocks have declined in recent years. Despite this there is currently very little scientific knowledge of this species, which would aid its management. The threats facing the species are unknown; however, pollution, overfishing, habitat degradation, parasite infection and changes in climate have all been forwarded as potential causes of the decline.
