Zingel streber (Siebold, 1763)
Aspro streber Siebold, 1863: Kovatcheff, 1923: 30; Drensky, 1951: 188.
Conservation status: in Bulgaria: Endangered EN [A1a; B1a, b], BDA-II; International: IUCN [VU A1ce+2ce], BeC-III, HD-II.
General distribution. Europe: in the Danube River from Bavaria to the Black Sea. Its finding was reported in Austria, Bosnia and Herzegovina, Bulgaria, Germany, Greece, Romania, Slovakia, Serbia, the Ukraine, Hungary, Croatia and the Czech Republic.
Distribution and abundance in Bulgaria. It was recorded in the Danube River and some of its biggest tributaries: the rivers Iskar, Vit, Osam and Yantra [1, 2, 3, 4, 5, 6, 7]. In the past, it ran far upstream the Danube tributaries – in the Iskar River as far upstream as Mezdra and Roman . At present, it is an extremely rare species found only in the Danube River [8, 9].
Habitats. Only in permanent large rivers.
Biology. It inhabits sections with rapid current and gravel bottom. The spawning period is from March to April. The fecundity is comparatively low: between 600 and 4 200 eggs. The eggs are deposited on stones. It feeds during the night on benthic invertebrate animals. It reaches a maximum length of 17 cm and a maximum weight of 170 g. The life span is about 5 years .
Similar species. The zingel (Zingel zingel), from which it differs by the longer and slender caudal peduncle and the lower number of rays in the two dorsal fins: 8-9 hard rays in the first dorsal fin, and 12-13 soft rays in the second one.
Negative factors. The main threats to the species are water pollution and fluctuations in river discharge as a result of river regulation activities. A negative influence is also exerted by competition of cyprinids whose abundance in recent years increased, as well as poaching.
Conservation measures taken. The species was included in Annex II of the Biological Diversity Act (2002).
Conservation measures needed. Development and implementation of an Action Plan for the protection of the species in Bulgaria; introduction of a ban on fishing of the species; protection of the Danube River against pollution.
References. 1. Kovatcheff, 1923; 2. Chichkoff, 1939; 3. Drensky, 1951; 4. Karapetkova, 1972; 5. Karapetkova, 1994; 6. Marinov, 1978; 7. Sivkov, 1987a; 8. Vassilev, 1994; 9. Karapetkova, Zivkov, 1995.
Authors: Tihomir Stefanov, Teodora Trichkova