European Eel
Anguilla anguilla (Linnaeus, 1758)
Anguilla vulgaris Linnaeus, 1758: Kovatcheff, 1923: 111; Morov, 1931: 80.
Order Anguilliformes
Family Anguillidae
Conservation status: in Bulgaria: Endangered EN [A1a,c; B1b (i, ii, iii, iv, v); D].
General distribution. The northern part of the Atlantic Ocean, the fresh waters of Europe and Northern Africa, England, Iceland, the Baltic Sea. It is also found along the coasts of the Mediterranean Sea, the Black Sea and the Sea of Azov.
Distribution and abundance in Bulgaria. In the past, it was found in: the Danube River, adjacent marshes and some of its tributaries; Sozopol Bay, the Kamchiya River and most of the coastal lakes; the rivers Maritsa and Tundzha and the adjacent marshes [1, 2, 3, 4]. It was also recorded in some of the inland marshes – Batak and Straldzha, the latter being the largest habitat of the species in Bulgaria [2, 5]. After the 1950s, as a result of the extensive draining of the marshlands, the species disappeared from many of its habitats, and single specimens were caught only in the rivers of the Aegean Sea basin and some coastal lakes [5]. Later, it was recorded in the Maritsa River basin [6], in Varna Lake and Beloslav Lake [7] and the rivers Kamchiya, Ropotamo and Veleka [8]. At present, it is a rare species, with its occurrence confirmed in the rivers Mesta [9], Vacha [10], Arda [11], Veleka [12], in the Danube and in Burgas Lake (our data).
Habitats. Spawning takes place in the sea. It lives in fresh waters until it reaches sexual maturity. In Bulgaria, it has been found most frequently in the lower reaches of rivers, but it also occurs in standing water basins.
Biology. An anadromous species. Spawning takes place in the Sargasso Sea. Eggs are layed at a depth of 700-1000 m and water temperature of 16-17°C. The newly hatched larvae undergo metamorphosis, and after 3-4 years reach the European coasts. The females enter the rivers and migrate upstream. After attaining sexual maturity in about 8 years, they again head towards the sea. In the estuaries, they meet the males, and swim together actively, covering about 7-8 thousand km in the course of 3 years, until they reach the Sargasso Sea [13]. It feeds on mollusks, crustaceans and fish [5, 14, 15].
Similar species. None.
Negative factors. River regulation by dams and weirs; draining of the wetlands; water pollution.
Conservation measures taken. The species was listed in the Red Data Book of Bulgaria (1985).
Conservation measures needed. Protection of coastal lakes and inland rivers against pollution. Restriction on the river regulation activities in the smaller rivers flowing into the Black Sea and in the tributaries of the Maritsa River.
References. 1. Konsulov, 1921; 2. Kovatcheff, 1923; 3. Drensky, 1923; 4. Drensky, 1925; 5. Drensky, 1951; 6. Michailova, 1965; 7. Gheorghiev, 1967; 8. Karapetkova, 1976; 9. Penczak et al., 1985; 10. Stefanov, Trichkova, 2006; 11. Stefanov, Trichkova, 2005; 12. Dikov, Zivkov, 2004; 13. Lelek, 1987; 14. Stojanov et al., 1963; 15. Svetovidov, 1964.
Authors: Tihomir Stefanov, Teodora Trichkova, Yanaki Sivkov
