Ship Sturgeon
Fringebarbel Sturgeon
Acipenser nudiventris Lovetsky, 1828
Acipenser glaber Heckel, 1836: Drensky, 1923: 66.
Order Acipenseriformes
Family Acipenseridae
Conservation status: in Bulgaria: Extinct EX, BDA-II, IV; International: IUCN [EN A1acde+2d]; CITES-II; HD-V.
General distribution. The species is found in the Black Sea, the Caspian Sea and the Aral Sea, from where the adults enter the rivers for spawning. In the Black Sea and in the Sea of Azov it is found very rarely. It is more numerous in the Caspian Sea, especially in its southern part, where it enters the rivers Kura, Lenkoranka and Astara for spawning. It has also inhabited the Danube River, upstream to Komarno (1 766 km from the river mouth), and some of its tributaries: Tisa, Sava, Drava, Prut and Seret Rivers.
Distribution and abundance in Bulgaria. In the past, it was found rarely in the Bulgarian section of the Danube, where only single specimens were caught [1, 2]. It was also reported from the Black Sea near Varna [3]. In recent years, it has not been recorded in Bulgaria [4].
Habitats. In different periods of the year it is found in different habitats. During the reproduction period, it inhabits permanent large rivers, and during the rest of the period – the open sea, coastal areas and estuaries.
Biology. The males reach sexual maturity at the age of 6-9 years, and the females at the age of 12-14 years [5, 6]. Spawning occurs from March to May at water temperature of 10-15°C. It takes place in swift current with stony or sandy bottom. Fecundity ranges between 200 000 and 1 300 000 eggs [5]. Adult individuals feed on insect larvae, mollusks and crustaceans [7].
Similar species. In the Bulgarian section of the Danube River and the Black Sea, another five species of sturgeons occurred: the beluga (Huso huso), the Russian sturgeon (Acipenser gueldenstaedtii), the sterlet (A. ruthenus), the starry sturgeon (A. stellatus) and the common sturgeon (A. sturio). The ship sturgeon is distinguished by the continuous lower lip and a high number of lateral scutes (52-74).
Negative factors. Loss (degradation) of habitats, as a result of hydrotechnical activities leading to river regulation by dams and weirs; water pollution; poaching and overfishing in the past.
Conservation measures taken. The species was included in the Red Data Book of Bulgaria (1985) and in Annexes II and IV of the Biological Diversity Act (2002). An Action Plan for the Conservation of Sturgeons in Bulgaria has been adopted (Ministry of Environment and Water, 2004). A temporary ban on catch of sturgeons in the Black Sea was initiated (Ministry of Agriculture and Forestry, 2006). A programme for captive breeding and reintroduction of the ship sturgeon into the Danube River has been developed (Ministry of Environment and Water, 2005).
References. 1. Kovatcheff, 1923; 2. Marinov, 1978; 3. Drensky, 1951; 4. Vassilev & Pehlivanov, 2003; 5. Banarescu, 1964; 6. Berg, 1948; 7. Sokolov & Vasil'ev, 1989.
Authors: Yanaki Sivkov, Tihomir Stefanov, Teodora Trichkova
