Schraetzer
Striped Ruffe
Gymnocephalus schraetser (Linnaeus, 1758)
Acerina schraetzer (Linnaeus, 1758): Kovatcheff, 1923: 27; Drensky, 1951: 186.
Order Perciformes
Family Percidae
Conservation status: in Bulgaria: Vulnerable VU [A1c], BDA-I, IV; International: IUCN [VU A1ace], BeC-III, HD-II, V.
General distribution. Europe, the Danube River basin.
Distribution and abundance in Bulgaria. In the past, the species was recorded in the Danube River (from Vidin to Silistra), and the Iskar River (near the village of Dolni Lukovit) [1, 2, 3, 4], as well as in the Golyama Kamchiya River (near the village of Ivanski) [5]. Later, it was found in the Danube River and the mouths of its tributaries Vidbol, Lom, Ogosta, Iskar (rarely), Vit, Osam and Yantra (single specimens reached as far upstream as the village of Polsko Kosovo) [6, 7, 8, 9, 10, 11]. In the period 2005-2006, single specimens were found in the Danube River along the entire stretch between the village of Vrav and the village of Vetren, but the species was not recorded in the Danube tributaries and in the Kamchiya River basin [our data].
Habitats. It is found in permanent large rivers.
Biology. It inhabits the deep sections of the rivers, with sandy and gravel bottom. It reaches sexual maturity in the second year, rarely, in the first year. Spawning occurs at water temperature of 8-14°C, in the period March-May. The fecundity of females ranges from 18 900 to 45 400 eggs. It is active during the night, when it moves to shallow places to feed. It feeds on crustaceans, worms, insect larvae and fish eggs. It reaches a maximum body length of 300 mm and a maximum weight of 250 g. The life span is 7 years. [11, 12, 13].
Similar species. The ruffe ( Gymnocephalus cernuus) and the Danube ruffe (G. baloni). The Schraetzer is distinguished by the elongated body with lower depth and by the presence of 3-4 dark longitudinal stripes on both sides.
Negative factors. River regulation by dams and weirs, which results in the loss of habitats of the species; water pollution.
Conservation measures taken. The species was included in Annexes II and IV of the Biological Diversity Act (2002).
Conservation measures needed. Development and implementation of an Action Plan for the protection of the species in Bulgaria. Restriction on the river regulation activities and protection of the Danube River against pollution.
References. 1. Kovatcheff, 1923; 2. Morov, 1931; 3. Chichkoff, 1939; 4. Drensky, 1951; 5. Chichkoff, 1934; 6. Paspalev, Peshev, 1955; 7. Marinov, 1966; 8. Karapetkova, 1972; 9. Sivkov, 1986; 10. Karapetkova, 1994; 11. Karapetkova, Zivkov, 1995; 12. Holcik, 1998; 13. Froese, Pauly, 2006.
Authors: Teodora Trichkova, Tihomir Stefanov
