Black Sea Chub
Petroleuciscus borysthenicus (Kessler, 1859)
Squalius borysthenicus Kessler, 1859: Chichkoff, 1930: 7; Leuciscus borysthenicus (Kessler, 1859): Drensky, 1951: 69; Karapetkova, Zivkov, 1995: 104.
Order Cypriniformes
Family Cyprinidae
Conservation status: in Bulgaria: Endangered EN [B1b]; International: IUCN [DD].
General distribution. Europe and Asia in the basins of the Black Sea, the Sea of Azov and the Sea of Marmara. It is also found in the basins of the rivers Struma and Maritsa flowing into the Aegean Sea. Its occurrence is reported in Byelorussia, Bulgaria, Georgia, Greece, Moldova, Romania, Russia, the Ukraine and Turkey.
Distribution and abundance in Bulgaria. It was first recorded in the rivers Kamchiya, Veleka and Poturnashka [1]. Later, it was recorded in most of the other Black Sea rivers: Batova, Devnya, Provadiyska, Perperek, Ropotamo, Dyavolska and Rezovska [2, 3, 4, 5, 6, 7, 8]. It was also found in some water bodies affiliated to the Aegean Sea basin: the Mochuritsa River, a tributary of the Tundzha River [9, 10], and in a small marsh within the Struma River basin [11]. A comparatively rare species. Although it was found in many habitats, its populations are extremely vulnerable. The species is extinct in some of its former habitats, such as the Mochurishta River [12]. In the Provadiyska River, it was not recorded as early as during the ichthyological investigations in the 1970s, and now it is considered extinct [13]. Recently, it has been confirmed in some of the southern Black Sea rivers [14, 15, 16]. At present, the only habitat of the species in the Aegean Sea basin is the canal passing through the Protected area "Rupite" and flowing into the Struma River [13].
Habitats. It inhabits slow-flowing rivers overgrown with macrophytic vegetation. It is also found in standing waters with a high degree of eutrophication, and in estuaries.
Biology. It reaches sexual maturity at the age of 3-4 years. Spawning occurs in the period April-May. Females release about 2 500 eggs at average. It feeds on invertebrate animals, small fish and fish eggs [13].
Similar species. The European chub (Leuciscus cephalus), from which it is distinguished most easily by the lower number of scales in the lateral line – 35-40 (in the European chub they are 43-47).
Negative factors. The main threats to the species are: intensive recreation development near its habitats; water pollution; draining of marshlands; direct competition from introduced fish species; poaching.
Conservation measures taken. Some of the habitats of the species are included within the following protected areas: Rupite, Mouth of the Veleka River, Sislistar.
Conservation measures needed. Restoration of the wetlands and measures for protection of the lower reaches of rivers that flow directly into the Black Sea. Control of observing fishing regulations.
References. 1. Chichkoff, 1930; 2. Chichkoff, 1934; 3. Chichkoff, 1936; 4. Drensky, 1951; 5. Pechev, 1969; 6. Karapetkova, Pechev, 1973; 7. Karapetkova, 1974; 8. Karapetkova, 1976; 9. Drensky, 1951a; 10. Stojanov, 1952; 11. Marinov, 1964; 12. Stefanov, 2004; 13. Stefanov, 2000; 14. Karapetkova et al., 2003; 15. Dikov, Zivkov, 2004; 16. Trichkova et al., 2006.
Authors: Tihomir Stefanov, Teodora Trichkova
