Eudontomyzon mariae (Berg, 1931)
Lampetra (Eudontomyzon) mariae Berg, 1931: Drensky, 1948: 13; Lampetra danfordi Regan, 1911: Drensky, 1935: 105; Lampetra (Eudontomyzon) danfordi Regan, 1911: Drensky, 1948: 13 and 1951: 20.
Conservation status: in Bulgaria: Critically endangered CR [B 1a, 2a; D; E]; International: IUCN [DD], BeC-III, HD-II.
General distribution. The species has occurred in the basins of the rivers Volga, Vistula, Kuban, Don, Dnieper, Dniester, Prut and the Danube. It has been recorded in Austria, Bosnia and Herzegovina, Bulgaria, Romania, Russia, Slovakia, Serbia, the Ukraine, Hungary and the Czech Republic.
Distribution and abundance in Bulgaria. In the first half of the previous century, the species was found in some of the Danube tributaries – the rivers Vit, Osam, Iskar and Mindevska (a tributary of the Yantra River), as well as in the Danube River near Lom, Oryahovo, Somovit and Ruse [1, 2, 3, 4] (in most sources the species is published as Eudontomyzon danfordi or Lampetra planeri). There are data that it also inhabited the rivers Zlatna Panega and Rusenski Lom . The lampreys had been considered extinct in Bulgaria for a long time , since their finding in the Danube River was last reported in the 1960s [7, 8] (published as E. danfordi). Recently, single specimens in the larval stage have been recorded again in the Bulgarian section of the river: near Ruse , as well as near Silistra and Belene [our data].
Habitats. The species inhabits only permanent rivers. Spawning takes place in the upper and middle reaches of rivers over sandy and gravel bottom. The larvae live in calm waters (lower reaches) on sandy and muddy substrate.
Biology. Spawning is from the end of April to the middle of May . A non-parasitic species. It spends from 4 to 6 years as larval form, feeding on detritus and phytoplankton (mainly diatoms). After the metamorphosis the adults do not feed. They migrate upstream and spawn in clear water with a strong current and sandy or gravel substrate. Soon after spawning, the adult individuals die. They have a life span of between 4.8 and 7.2 years .
Similar species. In many published sources, the only species of non-parasitic lamprey reported in Bulgaria is the European brook lamprey L. planeri [1, 4, 6]. This species, however, is known to occur only in the waters of Western Europe. Therefore, the individuals from Bulgaria identified as L. planeri must be considered as E. mariae [5, 11]. In the Bulgarian section of the Danube River and some of its tributaries, other authors reported the parasitic species E. danfordi [2, 3, 4, 6, 7, 8]. Its distribution, however, is restricted only to the basins of the rivers Tisa and Timish [12, 13]. Based on recent investigations, including a revision of all collected material from Bulgaria, it has been confirmed that in the Lower Danube, only the species E. mariae has occurred .
Negative factors. The main threats are: loss (degradation) of habitats as a result of river regulation by dams and weirs; water pollution.
Conservation measures taken. The species is included in the Red Data Book of Bulgaria (1985), under a different name.
Conservation measures needed. Protection of the middle and upper reaches of the Danube tributaries against pollution and a ban on construction of dams and weirs in these sections.
References. 1. Kovatcheff, 1923; 2. Drensky, 1935; 3. Drensky, 1948; 4. Drensky, 1951; 5. Stefanov, Holcik, 2007; 6. Karapetkova, Zivkov, 1995; 7. Kolarov, 1960; 8. Undzian, 1964; 9. Berg, 1948; 10. Holcik, Renaud, 1986; 11. Holcik, 1995; 12. Banarescu, 1969; 13. Renaud, Holcik, 1986.
Author: Tihomir Stefanov