Pungitius platygaster (Kessler, 1859)
Pygosteus platygaster Kessler: Drensky, 1923: 77.
Conservation status: in Bulgaria: Critically endangered CR [A1c; B1a, b (i, ii, iii)]; International: IUCN [LR/lc], BeC-III.
General distribution. The basins of the Black Sea, the Sea of Azov and the Caspian Sea. In the Black Sea basin, it is found in the Danube River upstream to Belgrade, in the lower reaches of the rivers Dniester, Bug and Dnieper, as well as in the deltas of the Don and the Kuban Rivers.
Distribution and abundance in Bulgaria. In the past, the species was abundant in the marshes along the Danube . It was also recorded in the main channel of the Danube River, the Vidbol River, the marshes along the Kamchiya River, the lakes Shabla, Durankulak and Vaya, the Mandra Reservoir, the lakes Varna and Beloslav [2, 3, 4, 5, 6, 7, 8]. Recently, the species has become extremely rare, showing a continuous decline of its range. At present, it is found in Srebarna Lake , Durankulak Lake  and Varna Bay, where single specimens were caught , and most likely, in some Black Sea rivers, for example, in the mouth of the Marinka River .
Habitats. Permanent rivers, permanent fresh water lakes and marshes, coastal fresh water and brackish lagoons, as well as sea bays.
Biology. It reaches sexual maturity in the first year. The spawning period is during April-August. Fecundity varies between 10-20 and 600-700 eggs. The males build nests amongst the submerged vegetation and guard them until the eggs hatch. The life span is about 3 years. It feeds on small crustaceans, eggs and larvae of fish .
Similar species. Three-spined stickleback (Gasterosteus aculeatus), from which it is easily distinguished by the higher number (7-12) of dorsal fin spines, lack of well visible bony plates along the side and lack of a caudal peduncle keel.
Negative factors. Loss (degradation) of habitats, as a result of draining of marshlands; water pollution; pressure from introduced species.
Conservation measures taken. Listed in the Red Data Book of Bulgaria (1985) and Red Book of the Black Sea (1999). The habitats of the species in Srebarna Lake and Durankulak Lake are included within the borders of protected areas.
Conservation measures needed. Development of an Action Plan for the protection of the species in Bulgaria.
References. 1. Kovatcheff, 1923; 2. Drensky, 1951; 3. Gheorghiev, 1967; 4. Karapetkova, 1974; 5. Karapetkova, 1976; 6. Marinov, 1978; 7. Karapetkova, 1994; 8. Karapetkova, Zivkov, 1995; 9. Pehlivanov, 2000; 10. Vassilev, 1999; 11. Sivkov, 2003; 12. Trichkova et al., 2006.
Authors: Tihomir Stefanov, Teodora Trichkova