Struma Loach
Barbatula bureschi (Drensky, 1928)
Nemachilus bureschi Drensky, 1928: Drensky, 1951: 121; Noemacheilus angorae bureschi (Drensky, 1928); Karapetkova, Zivkov, 1995: 130.
Order Cypriniformes
Family Balitoridae
Conservation status: in Bulgaria: Vulnerable VU [A3, B2], BDA-II; International: IUCN [LC].
General distribution. Only in the Aegean Sea drainage basin. An endemic species in the rivers Struma and Mesta.
Distribution and abundance in Bulgaria. The species was first described from the Struma River, near the Zemen railway station [1]. Later, it was recorded in other sections of the upper and middle reaches of the Struma River, in some of its tributaries, and in the Mesta River [2, 3, 4, 5, 6, 7, 8, 9, 10]. It was also found in the Palakariya River, where, most likely, it had entered from the Iskar Reservoir, after an accidental introduction by fish stocking [11]. At present, it is found in the Struma River (from the Lobosh Reservoir to the border) and in some of its bigger tributaries (Dzherman, Eleshnitsa, Lebnitsa and Pirinska Bistritsa), as well as in the Mesta River (from Momina klisura to the border) and its tributaries Dospat and Bistritsa [our data].
Habitats. It is found only in the upper and middle reaches of permanent rivers with sandy and gravel bottom and a fast current.
Biology. Poorly known. A typical reophilic species, which has a nocturnal activity. It reaches sexual maturity at body length of about 5 cm. Spawning takes place in shallow water in the period May–July. Eggs are laid over stones and gravel, in a swift current. It feeds on benthic invertebrate animals, mainly worms and insect larvae. It reaches a maximum body length of 10 cm [7, 12].
Similar species. The stone loach (Barbatula barbatula). The Struma loach is distinguished by the deeply notched caudal fin (in the stone loach it is truncated).
Negative factors. River regulation by dams, barrages and weirs; deforestation (especially in the mountain regions); water pollution.
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. Imposition of restrictions on the construction of dams, barrages and weirs, as well as of micro-hydro power development in the upper and middle reaches of the rivers Struma and Mesta. Control of deforestation in the mountain regions. Protection of the rivers against pollution.
References. 1. Drensky, 1928; 2. Chichkoff, 1939; 3. Drensky, 1948; 4. Drensky, 1951; 5. Michailova, 1965; 6. Penczak et al., 1985; 7. Karapetkova, Zivkov, 1995; 8. Stefanov, 2001; 9. Vassilev, Pehlivanov, 2002; 10. Apostolou, 2005; 11. Dikov et al., 1988; 12. Maitland, 2000.
Authors: Tihomir Stefanov, Teodora Trichkova
