Sturgeons

Sevryuga (Acipenser stellatus)
Beluga (Huso huso)
Russian sturgeon (Acipenser gueldenstaedtii)
Ship Sturgeon (Acipenser nudiventris)
Persian sturgeon (Acipenser persicus)
Sterlet (Acipenser ruthenus)

Acipenser stellatus Pallas, 1771 - Acipenseridae

Diagnostic Features

Spiracle present. Snout greatly elongated and sword-shaped, usually more than 60 % of the head length. Gill membranes joined to isthmus. Mouth transverse and lower lip with a split in the middle. The barbels are short and no fimbriate, not reaching the mouth but nearer to it than to tip of snout. D: 40-54; A: 22-35 fin rays. 9-16 dorsal scutes; 26-43 lateral scutes; 9-14 ventral scutes. The dorsal scutes have radial stripes and strongly developed spines with the tips directed caudal. Between the rows of scutes, the body is covered by star plates. The body colouration is blackish-brown dorsally and laterally. The belly is light, and the ventral scutes are dirty white coloured.

Geographical Distribution

Caspian, Azov, Black, and Aegean Seas, from which it migates into the rivers (Shubina et al., 1989).

Habitat and Biology

During the daytime they are often encountered in the upper layer, while at nigth, they are generally found at the bottom.The starry sturgeon inhabits the coastal sea waters (at depths from 100 to 300 m in the Caspian Sea) over clayey or sandy and clayey sediments, and the lowland section of rivers.Feeding habits vary with size, season and specific features of the water bodies (rivers or sea). The younger individuals feed primarily on crustaceans, while fishes (Gobiidae, Caspialosa, and Clupeonella) become more important in the diet as the grey older. Also molluscs, Polychaeta and other invertebrates. Sexual maturity is reached by males at an age of five or six years. Females mature with an average age of 9.7 years and rarely spawn more than three times in their lives. Enters rivers from April to June with a peak period when the water temperature reaches 10º to 15ºC. Eggs laid on beds of scattered stones, pebbles, gravel and sand. The juveniles stay near the mouth of rivers. Its population is supported by artificial propagation. Spawn from May to September at a water temperature of 12º to 29ºC.

Size

Maximum length of 218 cm (TL) and a maximum weight of 54 kg. They usually range from 100 to 120 cm and 6 to 8 kg.

Local Names

ALBANIA : Bli turigjate . AUSTRIA : Sternhausen . BULGARIA : Pastruga . FINLAND : Tähtissampi . FRANCE : Esturgeon étoilé . GERMANY : Sternhausen . HUNGARY : Söregtok . ITALY : Storione stellato . POLAND : Siewruga . PORTUGAL : Esturjao-estrelado . ROMANIA : Pastruga . RUSSIAN FED. : Sevryuga . SLOVENIA : Jeseter hviezdnaty . SPAIN : Esturión estrellado . SWEDEN : Stjärnstör . TURKEY : Mersin baligi . UKRAINE : Sevrjuga . UNITED KINGDOM : Starry sturgeon . USA : Sevruga , Star sturgeon .

Huso huso (Linnaeus, 1758) - Acipenseridae

Diagnostic Features

Spiracle present. Snout moderate and pointed, turning slightly upward. Gill membranes joined to one another to form a fold free from the isthmus. Mouth crescentic. Lower lip not continuous, interrupted at centre. Barbels oval or flat, leaf-like posteriorly reaching almost the mouth. 17-36 rod-shaped gill rakers. D:48-81; A:22-41 rays. 9-17 dorsal scutes; 37-53 lateral scutes and 7-14 ventral scutes. Dorsal scutes oval, with a longitudinal denticulate comb. First dorsal scute is the smallest. Lateral scutes smooth. Ventral scutes hidden beneath the skin. There are numerous small bony plates between the scute rows. Back ashen gray or black, gradually transitioning to white toward the underside. Belly white, and the snout is yellowish.

Geographical Distribution

The beluga is a diadromous species that inhabits the Black, Azov, Caspian, and Adriatic Seas. It is more numerous in the Caspian Sea and very rare in the Adriatic Sea (Pirogovskii et al. 1989).

Habitat and Biology

During the period of marine life, the adults mainly inhabits the pelagic zone descending at depths of 160-180 m. During both the seaward and the spawning migration, the beluga usually travels in the deepest parts of the riverbed. Juveniles during the first year of life remain in warmer, shallow habitats.The main food of juveniles appears to be insect larvae, especially of Ephemeroptera, crustaceans (gammarids, mysids, copepods, and cladocerans). Beluga begins preying on fishes , at a very early age (with a length of 24 cm in the lower Danube). Preferent prey items are Alosa spp., Engraulis encrasicolus, cyprinids (Cyprinus, Leuciscus, Scardinius, and Aspius). Marine fishes, such as Scomber scombrus, Trachurus mediterraneus ponticus and Sprattus sprattus are important in it diet between May and September, when the beluga are congregating near the coast prior to entering rivers; during the autumn and winter they descent into deep regions of the sea and feeds mainly on Mullus barbatus ponticus, Merlangius merlangus euxinus, Platichthys flesus flesus and Engraulis encrasicolus. First sexual maturity is reached by the great sturgeon very late. Most males of the Volga population mature at 14-16 years; most females reach this stage at 19-22 years. Subsequent spawning apparently begins at least 5 years later. The great sturgeon spawn far upstream in all rivers. Spawning period usually coincides with a high-water period in spring and begins at a water temperature of 6° to 7° C, and it ceased when the temperature reaches 21° C. The spawning sites are usually in the river bed, at a depth of 4 to 15 m, with a hard, stony or gravelly bottom; the hatchlings at an early age travel to the sea.

Size

Maximum size: about 6 m and a weigh exceeding 1000 Kg (Berg, 1948). Lengths of 8 m and weights of 3200 kg have been reported, but they raise doubts. Usually 120-260 cm and to 363 kg.

Local Names

ALBANIA : Bli turishkurte . AUSTRIA : Hausen . FINLAND : Beluga , Kitasampi . FRANCE : Beluga , Grand esturgeon . GERMANY : Europäischer Hausen , Hausenblase . GREECE : Akipíssios , Mocuna . HUNGARY : Viza . ITALY : Storione ladando . NORWAY : Belugastør . POLAND : Bieluga z , Wiz , Wyz . PORTUGAL : Esturjâo do Cáspio , Esturjão-beluga . ROMANIA : Morun . RUSSIAN FED. : Beluga . SLOVENIA : Beluga . SPAIN : Beluga , Esturión beluga . SWEDEN : Belugastör , Husblosstör . TURKEY : Mersin morinasi . UKRAINE : Beluga . UNITED KINGDOM : Beluga , Great Sturgeon . USA : Beluga , Great Sturgeon .

Acipenser gueldenstaedtii Brandt & Ratzeberg, 1833 - Acipenseridae

Diagnostic Features

Spiracle present. Snout short and blunt. Gill membranes joined to isthmus. Mouth transverse and lower lip with a split in the middle. The barbels are attached closer to the tip of snout than to the mouth and they are unfimbriated. 15-51 gill rakers, which are not fan-shaped, terminated by a single tip. D: 27-51; A: 18-33 rays. 8-18 dorsal scutes; 24-50 lateral scutes and 6-13 ventral scutes. Between the rows of scutes there are numerous bony plates. The colouration is greyish black, dirty green, or dark green dorsally. Laterally, it is usually greyish brown, and ventrally, grey or lemon. The juveniles are blue dorsally and white ventrally.

Geographical Distribution

Caspian, Black and Azov Seas and the rivers that empty into them (Vlasenko et al., 1989).

Habitat and Biology

In the sea, the Russian sturgeon inhabits shallow waters of the continental shelf; in the rivers it remains at depths from 2 to 30 m. The larvae are found at considerable depths and in rapid currents.Besides the main diadromus form, a freshwater form that does not migrate downstream to the sea has been reported from various rivers.The Russian sturgeon is a bottom-dwelling mollusc-feeder (Corbulomya, Abra, Cardium, Nassa). They also readily consume crustaceans (shrimps and crabs) fishes (Engraulis encrasicolus, Sprattus sprattus and gobiids) and polychaetes. The main food items of juveniles are crustaceans, including mysids and corophiids, and polychaetes. The grat majority of the males begin to reproduce at an age of 11 to 13 years, while the equivalent age for the females is 12 to 16 years (Berg, 1948). In the Volga River, the males requires two to three years to reproduce again after spawning, while the females take four to five years. Usually, the spawnin run of this species into the rivers begin in early spring, reaches its peak in mid o later summer and ceases in late autumn. In the Volga River the spawning period extends from mid-May through early june. The spawning sites are gravel or stony beds at depths from 4 to 25 m. Spawning at water temperatures between 8.9º C and 12º C.

Size

May reach 3 m, usually 110-140 cm. Reports of 4 m and about 600 kg may refer to Acipenser sturio.

Local Names

BULGARIA : Ruska esetra . FINLAND : Venäjänsampi . FRANCE : Esturgeon du Danube . GERMANY : Russischer stör . GREECE : Storioni . ITALY : Storione danubiano . NORWAY : Rysk stor . POLAND : Jesiotr kolchidzki . PORTUGAL : Sturjao do Danúbio . ROMANIA : Nisetru . RUSSIA : Chernamorsko-azovskyi osetr . SPAIN : Esturión del Danubio . SWEDEN : Rysk stör . TURKEY : Karaka baligi . UKRAINE : Ruskii osetr . UNITED KINGDOM : Danube sturgeon . USA : Azov-Black sea sturgeon , Kura sturgeon .

Acipenser nudiventris Lovetzky, 1828 - Acipenseridae

Diagnostic Features

The snout has an almost perfect conical shape. Snout and caudal peduncle subconical. Spiracle present. Gill membrane joined to isthmus. Mouth transverse and lower lip continuous, and not interrumpted in the middle. The barbels are fimbriate, halfway between tip of snout and mouth, reaching the later. 24-45 gill rakers. D:39-57. A:23-37 fin rays. 11-17 dorsal scutes. 49-74 lateral scutes (usually more than 50). 11-17 ventral scutes (in large specimens, these scutes wear away and are often almost fully lost). There are no small bony plates between the rows of scutes. The first dorsal scute is the largest and form an obtuse angle with the profil of head. Dorsum greyish green, becoming ligther on the sides. Ventral surface yellowish-white, and the fins are greyish.

Geographical Distribution

Black, Azov, Caspian and Aral Seas, from which adults ascend the rivers to spawn (Sokolov & Vasilev, 1989). According to Birstein (1993) it is extinct in the Aral Sea. Therefore, possibly a small population of this form still exists in Lake Balkhash (Zholdasova, 1997).

Habitat and Biology

The ship sturgeon remain in shallow water, above 50 m.Where the bottom is muddy. They are more abundant in the vicinity of river mouths. Freshwater forms seem to be present (Banarescu, 1964).Juveniles prey on insect larvae (Ephemeroptera, Trichoptera, Odonata and Plecoptera), other insects, molluscs, and crustaceans. Fully-grown ship sturgeon in the Caspian feed primarily on fishes , especially gobiids and, in recent years, a basic food item in their diet has become the introduced crab Rhitropanopus harrisi, which account for as much as 70 % of the food, by weight.). Enters rivers from March to May and in October/November, spawning from the end of April to June. Spawns at water temperatures between 12 and 17.9 ºC. Some non migratory forms, continously remains in the fresh water.

Size

Maximum of 221 cm, and weigh of 80 kg and a maximum age of 32 years.

Local Names

AUSTRIA : Glattdick . AZERBAIJAN : Ship . BULGARIA : Ship . FRANCE : Esturgeon à barbillons frangés . GERMANY : Glattdick . HUNGARY : Szintok . POLAND : Szypr . PORTUGAL : Esturjao-ventre-nu . ROMANIA : Bogzar . RUSSIAN FED. : Ship . SPAIN : Esturión barba de flecos . UKRAINE : Ship . UNITED KINGDOM : Fringebarbel sturgeon . USA : Ship sturgeon .

Acipenser persicus

Taxonomic description of species

Unlike Russian sturgeon, body more elongate and bulky, bluish in shade, head longer -17.6% of body length (TL), snout and postorbital distance increased. Corresponding differentiation rates (t) are 4.51, 4.17, and 4.25, respectively. Head depth at nape - 8.61% of TL. Maximum body depth in females - 17.44%, in males - 16.27% of TL. Ventral scutes/plates 6-12, D 31-50 (39.0 in average), A 16-30 (24.8 in average) (Putilina, 1983) Intraspecific forms. Persian sturgeon from the Caspian rivers, Kura and Ural, is homogeneous as regards the main meristic and plastic features (Peseridi, 1986). Existence of winter race was assumed based on different functional status/ maturity stages of spawners entering the Volga river (Putilina, Artyukhin, 1985). Related forms. Other sturgeon species within genus Acipenser.

Geographical Distribution

Persian sturgeon feeds at the shelf zone of the sea, primarily in the eastern part of the South Caspian. Individual specimens are found in the North Caspian, western part of the Middle and South Caspian (along Lenkoran shores) (Kuznetsova, Palgui, 1992) .

General characteristics of species

Ecologo-taxonomic group. Nekton Origin. Ponto-Caspian endemic species World distribution. Caspian and Black seas and rivers entering into them. Habitat. Bottom dweller save for the spawning migration, when fish traverse through water column. Occurs primarily at mud and/or sand bottoms (Legeza, 1972). Migrations. Undertakes feeding, spawning and post-spawning migrations. Enters the rivers for spawning, mainly Kura river, less - the Volga, Ural, rivers of Dagestan (Samur, Terek) and Azerbaijan (Lenkoranka, Astara), and Sefid-Rud.

Size

158 cm TL (male/unsexed;); 176.1 cm (female)

Acipenser ruthenus Linnaeus, 1758 - Acipenseridae

Diagnostic Features

Snout and caudal peduncle subconical. Snout length and form highly variable. Generally, sterlets with pointed snouts tend to be young specimens, and the average age of those with blunt snouts is greater. Spiracle present. Gill membranes joined to isthmus. Mouth transverse and lower lip with a split in the middle. Barbels fimbriate. 11-27 gill rakers. D:32-54, A:16-34. 11-18 dorsal scutes. 56-71 lateral scutes. 10-20 ventral scutes. Numerous bony plates between the rows of scutes. Colouration varies greatly. Back usually dark greyish-brown. Belly yellowish white. The scutes are dirty white and the fins, grey.

Geographical Distribution

The sterlet is a Eurasian species inhabiting rivers flowing into the Caspian, Black, Azov, Baltic, White, Barents, and Kara Seas (Sokolov & Vasilev, 1989).

Habitat and Biology

The sterlet is a potamal freshwater fish that seldom occur in large lakes. It inhabits the lowland and foothill zones of the rivers and usually stays in the current in deep depression in the riverbed. Small specimens are often encountered in sandy shallows. The two kinds of spawning sites are the river bed at a depth from 7 to 15 m, and floodplain sites flooded by the rising spring water, on pebbles and rarely on gravelly-sand bottoms.It generally behaves as a resident fish.Does not undertake long migrations.Their main food in all rivers is benthic organisms, mainly insect larvae ( Trichoptera , Chironomidae , Ephemeroptera , Plecoptera , and Simuliidae ); small mollouscs (Sphaeridium spp., Pisidium spp. and Viviparus), annelids, other invertebrates , and also fish eggs, including those of other acipenserids, are also included in their diet. Young specimens feeds mainly on trichopteran and chironomid larvae. In the Volga river near its mouth, gammarids account for over 90 % of the food by weigh in young specimens. With increasing size, the role of tricopterans increases while that of chironomidae decreases. Males reach sexual maturity at an age of 3-6 years old, one to two years earlier than the females. The spawning periodicity remains open: spawn every year or only after a pause (shorter for males than for females) of one or more years?. Possibly, in the northern part of the range, the onset of sexual maturity would be later, and a considerable proportion of the adult specimens would not reproduce during every spawning season (Sokolov & Vasilev, 1989). During the spring floods they do swim upstream in the river for spawning. Males appear at the spawning ground before females at the water temperature from 9 to 11 ºC. Females reach the spawning ground later, at a water temperature from 12 to 13 ºC. The optimal water temperature for the reproduction of sterlets ranges from 12 to 17 ºC. The sterlet has the shortest life span (22-24 years old) in the genus Acipenser and females live longer than males.

Size

Maximum size 125 cm and a weight of 16 kg; usually below 100 cm and 6 to 6,5 kg.

Local Names

AUSTRIA : Sterlett . BULGARIA : Chiga . DENMARK : Sterlet . FINLAND : Sterletti . FRANCE : Sterlet . GERMANY : Sterlet . HUNGARY : Kecsege . NORWAY : Sterlett . POLAND : Sterlet a. czeczuga . ROMANIA : Cega . RUSSIAN FED. : Sterlyad' . SPAIN : Esterlete . SWEDEN : Sterlett . UKRAINE : Sterljad . UNITED KINGDOM : Sterlet . USA : Sterlet .

Sourse :FAO