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Lower Danube – The Last Refuge For Surviving Of Sturgeon Fishes In The Black Sea Region

This article provides a brief overview of the Lower Danube as a crucial habitat for sturgeon fishes, which are classified under the order Acipenseriformes. It discusses the impact of human activities such as overfishing and the construction of hydro-technical constructions on sturgeon populations. The article also emphasizes the importance of conservation measures to protect sturgeon species and their habitats.

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Lower Danube – The Last Refuge For Surviving Of Sturgeon Fishes In The Black Sea Region

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  1. Lower Danube – The Last Refuge For Surviving Of Sturgeon Fishes In The Black Sea Region Milen Vassilev Institute of Zoology Bulgarian Academy of Sciences

  2. Brief characterization of the region The Danube River

  3. The Black Sea Region

  4. Sturgeon and Paddlefish Species - Classification and Distribution Sturgeons and Paddlefishes belong to the class Osteichthyes (Bony fishes) and the order Acipenseriformes, which contains the family Acipenseridae (Sturgeons) with 4 genera (Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus ) and family Polyodontidae (Paddlefishes) with 2 genera (Polyodon and Psephurus). The family of Sturgeons contains 26 species, and the family of Paddlefishes - 2 species. All of them inhabit the Northern Hemisphere - Ponto-Caspian-Aral region, North America and East Asia.

  5. The Danube and the Black Sea Region – 6 sturgeon species Atlantic sturgeon Ship sturgeon Sterlet

  6. Stellate sturgeon Russian sturgeon Great sturgeon

  7. Human Impact 1. Fishing According to the archaeological excavations, the draughts of Sturgeons date back to more than 20 centuries. Sturgeons have been fished for caviar as well as for meat. It is considered that the human impact on the number of Sturgeons started in the 17-th century. A permanent decrease of sturgeon stocks on global started at the end of the 19-th century and has continued up to present days. Nowadays the high economic value of caviar is the main reason for overexploitation of sturgeon stocks. Especially, caviar from the Danube River is considered as a delicacy. The Black Sea region takes up the second place in the World (after the Caspian Sea region) by sturgeon catches and production of caviar.

  8. Sturgeon catches in the Lower Danube

  9. Distribution of sturgeon catches per fishing zones

  10. Distribution of catches by countries and species

  11. Caviar production by countries and species

  12. 2. Building of hydro-technical constructions and barraging the rivers The spawning migrations of Sturgeons are interrupted by the building of the hydropower plants and barraging of the large rivers. The spawning areas can be drastic shortened. After construction of the “Dubosarskaya” and the “Kahovskaya” hydropower electric stations in the beginning of 1950s, respectively on the rivers Dnestr and Dnepr, the both of them lost their significance for the natural sturgeon reproduction in the Black Sea region. In the Upper and the middle Danube and some of their tributaries, migratory Sturgeon species have become extinct after disruption of their spawning migrations by the construction of Iron Gate I dam in 1972 (rkm 942) and Iron Gate II dam in 1984 (rkm 863).

  13. Iron Gate II

  14. 3. Water Pollution The pollution with nutrients (nitrogen and phosphorus) have increased after 1970 and contributed to the eutrophication of the Danube River and the North-western Black Sea. Pollution affects on the biota by discharges of substances from industry and mining, as well as water pollution by pesticides, oil products and heavy metals.

  15. Conservation Measures ▪ Protection of species and habitats. ▪ Restoration and protection of the key habitats: spawning and overwintering sites, migration routes. ▪ Management measures – preparation of “Action plans”. ▪ Trade regulations – by CITES. ▪ Artificial propagation and restocking. ▪ Scientific-research programs.

  16. Sturgeon Fish-Farm in Vidin, Bulgaria Restocking with sturgeon juveniles in the Danube

  17. Thank you for your attention!

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