Acipenser güldenstaedti (Brandt, 1833)

Synonyms: Acipenser güldenstaedti Berg, 1911; Acipenser güldenstaedti var. colchicus Marti, 1940; Acipenser güldenstaedti colchicus Berg, 1948.

Common names: Engl: Russian sturgeon; Bulg: Ruska esetra; Rom: Nisetru; Russ: Russkiy osetr; Turk: Karaca; Ukr: Oseter.

Order (Scientific): ACIPENSERIFORMES.

Family (Scientific): ACIPENSERIDAE.

Taxonomic descriptions: Subcylindrical and elongate body with large bony scutes arranged in 5 raws; one in the middle of the back, one pair on the sides and another pair on the belly; a pair of large triangular bonny scutes on the isthmus, beneath the head; the mouth placed beneath the head is small, transverse and can be protected as a short tube; gill membranes joined to the isthmus, thus not forming a free fold; lower lip interrupted in the mid-line snout blunt and short, barbels on the underside of the snout, not reaching the mouth and inserted on a transverse row nearer to the tip of the snout than to the mouth; colour of the back and sides variable from grayish-black to dark green, belly whitish. Size: maximum - 210 cm; common - 110-145 cm (males), 130-170 cm (females).

IUCN Status:
    World level:
    Black Sea Regional level:
    Subregion level: VU

Distribution:

Habitats type, Critical habitats, Limiting factors: Mainly coastal waters of the sea and rivers; enters the Don, Kuban, Dniepr, Danube and rivers of the Caucasian coasts of the Black Sea. Spends the winter in the zone with Mytilus and Modiolus biocoenosis (at 60-70 m depths). Abundant in the Azov Sea, also occurring in the Caspian Sea; absent in the Mediterranean Sea.

Biology: Feeds mainly on molluscs, crustaceans and fishes. Migratory anadromous species; in spring (February-May) enters the rivers and in autumn (August-November) in the sea on the hibernation grounds. During the spawning run the fish move separately or in small shoals. The Sexual maturity at 8-12 years (male) and 13-15 years (female); after reproduction, adults come back to the sea.

Population trends: Caught with drift and stake net, long lines and beach seines. In June 1903 - March 1904 in front of the Sf.Gheorghe branch 85,160t were caught , and in the Portita zone 60,175 kg; compared with the 1920-1940 period, the catches of this species diminished by 80% in 1940-1960; in front of the Danube mouths, the catches recorded for July-October of this period represented hundred tons/year; in 1989 - 19,000 t; in 1990 - 4,000 t and in 1991 - 15,000 t; for the 1993-1994 period, there were estimated (for the North-West zone of the Black Sea) stock of 3,300,000 specimens, 180,000 of them exploitable.

Threats: Overfishing, large hydraulic projects which block traditional migration routes and access to spawning areas.

Conservation measures taken: Development of experimental research concerning the artificial reproduction and growing of fry. This species is under the protection in Turkey since 1997. Total catch was 110 tons in 1995. A special recovery and monitoring programme was started by the Turkish Marine Research Foundation in Sakarya and Kizilirmak estuaries.

Conservation measures proposed: Respecting the feeding sites of the fry from the Danube mouths; interruption of fishing with pound nets during the great agglomerations of fry (July-August); protection of spawners during migrations and spawning times (April-July); production of fingerlings and populating the Danube river. Adoption of strict national measures to reduce poaching; fisheries under strict international control.

References:

1. Caloianu-Iordachel, M. 1965 - Data regarding the ecology of four species of sturgeons in the first post-embrionary development stages. Hydrobiology, VI. (In Rom.).
2. Antipa, Gr., 1941 - Black Sea - oceanography, bionomy and generally biology. I, 10, 55. (In Rom.).
3. Antipa, Gr., Les esturgeons de la Mer Noire, leur biologie et les mesures necessaires pour leur protection. Bull.Sect.Acad.Rom.
4. Busnita, Th., 1953 - The problems of sturgeons and clupeids from the Black sea. Bul.Inst.Cerc. Pisc., 4. (In Rom.)
5. Leonte, V., 1956 - Contributions to the study of the biology of marine sturgeons from the waters of the RPR. An.Inst.Cerc. Pisc.: 167-185. (In Rom.).
6. Manea, Gh., M.Mihai, 1957 - First experiments in the reproduction and artificial growing of sturgeons in RPR. Bul.Inst.Cerc.Pisc., 16, 1: 57-72. (In Rom.).
7. Manea, Gh., I. Alexandrescu, M.Mihai, 1963 - Actual and long-term state of the sturgeons and their culture in RPR. Hydrobiology, IV: 229-320. (In Rom.).
8. Leonte, V., N. Pogarneata, 1963 - Contributions to the knowledge of ages and sizes and migration of marine sturgeons from the Danube rivers, concerning their industrial fishing. Hydrobiology, IV: 287-297. (In Rom.).

Compiled by: A.Petranu, B.Öztürk.