Acipenser stellatus, Pallas

Taxonomic description of species

Body elongate, fusiform, with 5 longitudinal rows of bony scutes/ plates. Scutes: dorsal 9-16, lateral 26-43 , and ventral 9-14 . Sides covered with light starry denticles located between rows of scutes. Top of head covered with bony shields. Snout elongate, its length more than half of head length. Mouth protrusible, appears as transverse slit,lower lip interrupted. Barbels without fringe. Gill rakers on first gill arch 24.7-25.5 in average. Rhombic scales on upper lobe of caudal fin. D 40-54, A 22-35.
Intraspecific forms. Acipenser stellatus in the Caspian Sea is represented by three populations: Volga, Ural and Kura; fish of the Volga River origin prevail in number.

Proportion dynamics of sevruga populations at sea
(Perevaryukha, 1989, 1997)

Population/ origin	Share of the population, %
	1981-1982	1992
Volga	54.0	66.0
Ural	34.0	28.0
Kura	12.0	6.0
Total	100.0	100.0

Related forms. Species of genus Acipenser.

Distribution of species within the Caspian Sea

Distributed throughout the Caspian Sea. Enters for spawning the Volga, Ural, Terek, Sulak, Samur, Lenkoranka, Sefid-Rud, Kura, Araks and rivers of the southern coast as far as Gorgan. The total distribution area varies from 10,300 to 16,000 km² depending on season.
Status as per International Red Data Book: IUCN Red Data Book - VU
Status as per National Red Data Books: VU
First record for the Caspian Sea: Pallas, 1771
Redescription of species: Acipenser stellatus Pallas, 1771; Acipenser sevruga Güldenstädt, 1772; Acipenser helops Pallas, 1814; Helops stellatus Bonaparte, 1846; Acipenser stellatus Berg, 1911; Borzenko, 1942; Berg, 1948; Helops stellatus Lukyanenko, 1979; Subbotkin, Subbotkina, 2000

General characteristics of species

Ecologo-taxonomic group. Nekton
Origin. Ponto-Caspian endemic
World distribution. Apart from the Caspian, Acipenser stellatus occurs in the Black Sea and Sea of Azov, a rare species for the Adriatic and Marmora Seas.
Habitat. Acipenser stellatus is a more pelagic species than Russian sturgeon, moves in the water column of deep zones. Within its range, Acipenser stellatus feeds at the areas of steep slope and shelf zone of the sea, rich in food supply, and prefers bottoms covered with silt or silt/ sand, prolific of Gammaridae and Corophiidae (Legeza, 1972). It spawns at riverbeds, mainly on stony ridges (Bokova, 1992; Veshchev, 1994, 1998).
Migrations. Anadromous fish.
In spring, Acipenser stellatus makes spawning (anadromous) migrations from the Middle and South Caspian to the North Caspian, and thence mature fish enter the Volga, Ural and rivers of Dagestan to spawn. Post-spawners migrate downstream to marine feeding grounds. Feeding migrations are defined as continuous movements of fish from one part of the sea to another in search of food. Pre-wintering migrations of stellate sturgeon begin earlier than those of other sturgeons, namely, in August. The Ural stellate sturgeon winters in the Ural and Mangyshlak deep trenches, the Volga stellate sturgeon - at Dagestan and Azerbaijani coasts. Immature fish prefer Turkmenian shelf zone, where the water is warmer in winter.
Larval stellate sturgeon migrates downstream the Volga River in June-August, predominantly within 3-m bottom layer (88.1%) (Veshchev, 1994).

Relation to abiotic environmental factors

Relation to salinity. Brackish-water, the most euryhaline species among Caspian sturgeons. Juveniles are less tolerant to saline environment than adults; water salinity of 8� is lethal to larvae at early stages of development. Adults and grown juveniles occur in the North, Middle and South Caspian at salinity range 0-14.34� (Legeza, 1972).
Relation to temperature. The most thermophilic/ warm-water sturgeon species. Temperature characteristics of habitat area is 2.4-29.5⁰C ("The Caspian Sea", 1989).
Relation to oxygen conditions. Occurs in areas with oxygen saturation 42.50- 131.10% at the bottom, forms significant aggregations at oxygen saturation 64.93-94.67% (Legeza, 1972).
Relation to fluctuations of the sea level.
In the years of the sea level drop young stellate sturgeon from the Volga and Ural Rivers migrated straightforward to the western shelf zone of the Middle Caspian without lingering in the northern part of the sea. A rise in seawater level promotes to increased number of stellate sturgeon migrating to the North Caspian during summer period.

Feeding

Feeding type. Heterotrophic/ holozoic
The diet is similar to that of benthic-feeders, but fish food is of greater importance (Shorygin, 1952; Kashentseva, 2001).
Feeding behavior. Active search
Feeds mostly on benthic organisms and fish. When food item is detected, the fish makes a rapid seizing-sucking movement with its protrusible mouth.
Food spectrum. When larvae transfer to active feeding (5th-9th day after hatching, 18-19 mm TL), the main food items are Oligochaetae, Polychaetae, Corophiidae, Gammaridae, Mysidae as well as larvae and pupae of Chironomidae. Corophiidae (66%) and Gammaridae (23%) dominate the diet of young stellate sturgeon (up to 10 cm TL) in the North Caspian.

Feeding habits of stellate sturgeon juveniles in the North Caspian, % of weight
(Polyaninova, 1983)

Food items	Length of stellate sturgeon, cm
	10	20	30	40
Vermes	3.1	6.4	21.2	-
Crustacea:	96.1	91.0	78.6	-
Gammaridae	23.0	14.0	-	-
Corophiidae	66.0	20.7	-	-
Mysidae	6,7	55.9	78.6	-
Other	-	2.3	-	82.1
Pisces	0.4	0.4	0.1	-
Chironomidae	0.8	0.3	0.1	17.9
Average weight,g	2.8	15.3	42.5	168.0

The diet of young fish (more than 10 cm TL) includes mostly Mysidae (56-70%), Corophiidae (20.7%) and Gammaridae (14%), though fish food (0.1-0.4%) also occurs (Polyaninova, 1983).
The food of adult stellate sturgeon in 1930-s was, basically, crustaceans (94%) (Zheltenkova, 1951). In the late 1940-s, Nereis diversicolor O.F. Muller (targeted introduction of this species into the Caspian was conducted in 1939), was included in its diet (Tarverdieva, 1965). In all subsequent years Nereis diversicolor, along with higher crustaceans represented the main food item of sevruga ("The Caspian Sea", 1985; Kashentseva, 2001)

Dynamics of diet composition of stellate sturgeon in the North Caspian

Food items, % of weight	Periods, years
	1935-37	1948-49	1954-57	1962-63	1974-80	1986-99
Vermes (Ampharetidae, Nereidae)	-	27.87	32.08	53.10	34.00	58.30
Crustacea (Amphipoda, Cumacea, Mysidacea, Decapoda)	94.00	65.23	49.08	32.90	46.00	29.60
Mollusca (Adacna, Monadacna, Didacna, Abra)	-	0.06	1.35	8.40	9.00	3.60
Insecta (Chironomidae)	0.15	0.64	11.08	0.20	1.00	3.30
Pisces (Gobiidae, Clupeonella)	0.80	1.60	0.93	1.20	3.00	4.80
Other	5.05	4.60	5.48	4.20	7.00	0.40
Total	100	100	100	100	100	100

Cited: - data for the year 1935- Belogurov, 1939
1937 - Zheltenkova, 1951
1948-49 - Sokolova, 1952
1954-57 - Sayenkova, 1964
1962-63 - Tarverdieva, 1982
1974-80 - Polyaninova, Kashentseva, 1985
1986-99 - Kashentseva, 2001
Fish, mainly Clupeidae (Clupeonella cultriventris and Cl. engrauliformis) and Gobiidae (genera Neogobius and Benthophilus), are rather important for stellate sturgeon in the Middle and South Caspian (Kashentseva, 2000), though they are rated third after Nereis diversicolor and mollusks. Certain disturbances in specific feeding habits occurred due to the drop of the sea level, i.e. transfer to substituting and constrained food items (Kashentseva, Polyaninova, 1989).

Food composition in stomach content (% of weight) and indices of stomach fullness (⁰/₀₀₀) of stellate sturgeon during 1986-1999
(Kashentseva, 2001)

Area of the sea Food items	North Caspian	Middle Caspian	South Caspian	Entire sea
Vermes	58.3	45.0	53.9	50.0
Crustacea	29.6	14.6	14.9	21.4
Mollusca	3.6	26.1	17.8	18.0
Insecta	3.3	-	-	0.6
Pisces	4.8	14.2	13.3	9.7
Other	0.4	0.1	0.1	0.3
Total	100.0	100.0	100.0	100.0
Total index of stomach fullness	8.3	10.2	6.6	8.3

Food supply. Zoobenthos: Polychaeta, higher crustaceans (orders: Amphipoda, Cumacea, Mysidacea, Decapoda), mollusks (Hypanis vitrea, H. angusticostata, Abra ovata), and fish (Clupeonella cultriventris, Cl. engrauliformis, gobies).
Presently, the share of benthic biomass consumed by sevruga, is low - 5g*m^-2 in 1999. Importance of crustaceans for feeding juvenile fish decreased in late years, their biomass averaged 2.2 g*m^-2 in 1999 - the minimum value recorded during 45 years of studies.
Quantitative characteristics of feeding. Average annual index of stomach fullness in population of stellate sturgeon around the Caspian Sea (1986-1990) is 8.3⁰/₀₀₀, in the North Caspian - 8.3⁰/₀₀₀, 10.2⁰/₀₀₀ - in the Middle, and 6.6⁰/₀₀₀ - in the South Caspian, respectively (Kashentseva, 2001). Feeding activity is more pronounced in nocturnal hours, digestion rate (diet of Nereis, crustaceans and gobies) is 9.77⁰/₀₀₀*hr^-1 (Dvornikov, 1992).).

Reproduction

Reproduction type. Sexual/ gamogenesis
Reproduction areas. After regulation of the Volga River stream, some 373 ha of sturgeon spawning sites remained of a total of 3,390 ha. Acipenser stellatus reproduces at spawning sites of the total area 248.4 ha located between the Volgograd dam and Seroglazovo Village (Veshchev, 1994, 1998).
Spawners ascended the Ural River as far as Uralsk City (850 km from the offing). At present, due to drastic decline in the spawning stock, most individuals spawn in the lower zone, up to 200-225 km from the mouth of the river (Kim, Bokova, 2000).
Spawning grounds in the Terek are located in the middle reaches of the river, in the Sulak - at 100-km area of the lower section. The total spawning area of these rivers constitutes currently only 20 ha. Only five sturgeon spawning sites with total area 112.8 ha remained of previous 53 ha in the Kura River and 290 ha in the Araks River (Voinova, Alekperov, 1992).
Terms of reproduction. In the Volga River, in the years with favorable hydrological conditions/ optimum regime of water discharges, vigorous spawning occurs at spawning grounds 4-8 m depth, with water velocity 1-1.4 m*sec^-1, water temperature 8-15⁰C, and maximum water level in the river, from the second 10-day period of May to the first 10-day period of June (Veshchev, 1998).
The peak run of spring spawners in the Ural River is recorded at the end of the second - third 10-day period of April. Spawning takes place in May-June at water temperature 13-20⁰C (Mitrofanov, Dukravets, Peseridi, 1986).
Spawning interval is approximately similar for females and males; it varies from 2 to 7 years. The first interval for females is 3.8 years in average, 3.2 years - for males (Veshchev, 1998).
Fecundity. In 1980-s, female spawners of the Volga produced about 214,000-236,000 eggs; in the Ural - 236,000-253,000 eggs varying from 53,000 to 916,000 eggs in some individuals. At present, because of reduced number of recurrent spawners, this value decreased to 136,400 eggs (Vlasenko, Dovgopol et al., 2001, in press); in the Ural River - 236,200-270,700 eggs.
Limiting factors. Decline in larval abundance occurs, primarily, due to impact of abiotic environmental factors (temperature, oxygen concentration, salinity, etc.). The next stages are mostly affected by biotic conditions (food supply and predatory fish), while adults are mainly influenced by anthropogenic factors (fishery and pollution) responsible for reduction in the number and degradation of quality of spawners (Zykova, Krassikov, Zhuravleva, 2000).

Life history and development

Life history stages. Acipenser stellatus passes in the course of development several life-history stages characteristic of all sturgeon species: embryo, prelarva, larva, fry and adult fish (Detlaf, Ginzburg, Shmalgauzen, 1981).
Relation to environmental factors. Heavy mortality is recorded at early developmental stages. The main factors, which contribute to increase of mortality are as follows: considerable variations and fall in water temperature during the period of embryogenesis, unfavorable oxygen conditions, food deficiency during the period of initiation of active feeding, predation by fish.
Age of maturity. Sevruga females at their first spawning season in the Volga River are 7 years old, 4.6 kg weight, and 117.5 cm TL. Males mature at the same age as females, but their size and weight are smaller: 4.0 kg and 114.6 cm, respectively (Vlasenko et al., 2001). Males in the Ural River mature at an earlier age than females, and some males are able to spawn at the age of 4-5 years.
Thermal conditions of development. Embryonic development lasts for some 6 days at temperature 15⁰C. Embryos hatch in 55-60 hours after fertilization at temperature 25⁰C.
Prelarvae - 16-20⁰C
Larvae - 18-22⁰C
Juveniles - 2.4-29.5⁰C
Adult fish - 2.4-29.5⁰C
Quantitative characteristics of growth. The maximum length of Acipenser stellatus sampled in the Volga River basin is 190 cm, at sea - 218 cm (Borzenko, 1942). Life span is 31 years. ("The Caspian Sea", 1989). Currently, females at the age of 15-17 years, 148.0-152.4 cm TL and 11.1-12.1 kg weight form the majority of spawners in the Volga River. Most males mature at the age of 11-13 years at 129.7-133.5 cm TL and weight 5.9-6.5 kg. Females reaching their age limit of 29 years are generally 182.5 cm TL and 14.4 kg in weight. Males at the age of 25 years (age limit for males) are usually 152.5 cm in length and 9.8 kg in weight (Vlasenko et al., 2001).
According to the data obtained in 1998, the mean length of sevruga females in the Ural River was 149.7 cm, that of males - 139.6 cm, they weighed 11.5 and 6.7 kg, respectively.
The mean length of the Kura stellate sturgeon in the 1980-s corresponded to 130 cm, weight - 6.3 kg. Age composition of the spawning population was within 7-24 years (Voinova, Alekperov, 1992). At present, stellate sturgeon from the Kura is 121.4 cm TL and 7.1 kg (4.3-10.3 kg) in weight (Kuliev, Zarbalieva, 2000).

Structural and functional population characteristics

Sexual structure. Sexual structure of population at sea indicates a long-term domination of females, which account for 55.6-70.8% of the population in the North Caspian, 54.8-69.9% in the Middle and South Caspian and 57.9-65.2% for the sea as a whole ("The Caspian Sea", 1989; Slivka et al., 2000). The number of pre-spawning females migrating to the Volga River decreases steadily: from 47% in 1996, to 15% in 2000 (Vlasenko et al., 2001). Sevruga females in the Ural River accounted for 59.9% of population number in 1974, 61.4% in 1983, 43.1% in 1997, 37.8% in 1998, 41.8% in 1999 (Kim, 2000). Currently, the proportion of females entering the Terek River spawning grounds is only 14%.
Age-size structure. Up to the late 1980-s, sea catches were composed by the fish aged 1 - 20 years; individuals aged 6 - 31 years were taken from the river ("The Caspian Sea", 1989). In 1990-s, age composition of stellate sturgeon population was considerably distorted. In recent years, females aged above 25 years, males - above 21 year, were not traced in catches. Age of sevruga from trawl catches at sea decreased to 14-16 years.
The age limit of stellate sturgeon in the Terek spawning population does not exceed 18 years. The maximum age of the Kura stellate sturgeon captured with stationary nets at the Azerbaijani coast decreased from 19 years in 1989 to 14 years in 1995 (Kuliev, Zarbalieva, 2000). Age composition of the Ural sevruga stock did not alter considerably, 5-34-year-old fish are harvested as previously (Kim, Pak, Mustafin, 2000).
Quantitative characteristics. During the period of 1991-1999, the absolute abundance of Acipenser stellatus in the Caspian Sea decreased by a factor of 2.2, from 30.1 to 13.8 million individuals. As evident from long-term data, the spawning part of sturgeons' populations migrating to rivers amounted to 9-12%; in 1998-2000, proportion of sevruga spawning population decreased to 2.2-4.6%.

Absolute abundance of stellate sturgeon in the Caspian Sea

Years	1968	1969	1970	1972	1974	1978	1983	1987	1988	1991	1994	1998	1999
Million individuals	79.0	90.0	87.0	78.0	62.0	69.7	53.1	44.9	41.8	37.9	13.6	11.6	13.8

Population trends. A decline in the commercial stock of Acipenser stellatus at sea is verified by decreased number of spawners, which enter the river and access spawning grounds. In 1993, the biomass of the spawning population of sturgeons in the Volga River was 9,100 tons; in 1999, it decreased to 3,920 tons. The number of sturgeon spawners that entered spawning grounds of the Volga River in 1993 was, on average, 322,000 individuals whereas in 2000 it decreased to 24,030 individuals (Vlasenko, Dovgopol et al., 2001).

Interspecific relations

Acipenser stellatus is a predatory species that consumes animal food including fish. Adults feed on gobies and kilka/ sprat. In some years, fish food may contribute to 27% of their diet (Polyaninova, 1983; Stygar, 1984). Eggs, larvae and young fish at early developmental stages, in their turn, are subject to pressure of piscivorous birds and fish predators: sterlet, zander, catfish, pike, perch, and ruff. Adult stellate sturgeon could be taken as food for large beluga sturgeon, catfish and seal.

Importance of species to bioresources production of the Caspian Sea

Economic significance of species. Valuable, commercially important species
Commercial characteristics of species, catches. . The largest catches of stellate sturgeon in the Caspian Sea basin were recorded in mid-1970-s (13,320 tons). At present, status of sturgeon stocks is disastrous. The total catch does not exceed 900-600 tons (except for Iran).
Fishing gears and fishing zones. Fishing at rivers (since 1962) was conducted with riverine beach seines.Currently, stellate sturgeon (as well as the other sturgeon species) is taken only from the Volga and Ural Rivers as by-catch in harvesting ordinary fish ("chastik").

Impact of fisheries on the population status

In 1960-s-1970-s, overfishing was mainly due to unsustainable fisheries management; since the second half of 1980-s - due to steadily increasing illegal/ unaccounted catches.
Human impact/Threats. Among anthropogenic factors that adversely affected the abundance and status of sturgeon stocks, the following should be indicated:

• development of hydroelectric power system (damming of rivers);
• pollution of water bodies from oil, petroleum products, pesticides and heavy metals;
• fisheries load, in particular, illegal harvest/ poaching at sea and in rivers.

Conservation measures. For conservation and sustainable utilization of stellate sturgeon stocks in the Caspian Sea basin, it is necessary to accelerate signing of "Agreement on Conservation and Management of Caspian Bioresources"; this document should outline international legal aspects of exploitation, artificial propagation and natural reproduction, protection of fish stocks and prevention of river and sea pollution. Additionally, enhancement of economic and legal measures for poaching control should be emphasized.

References

Alyavdina, L.A. 1951. On biology and taxonomy of sturgeons at early stages of development. Proceedings of the Saratov Department of VNIRO Caspian Branch.. Saratov. Pp. 33-69 (in Russian).
Berg, L.S. 1911. Fauna of Russia and adjacent states. Vol. 1. Fish. St.-Petersburg. 250 p. (in Russian)
Berg, L.S. 1948. Freshwater fish of the USSR and adjacent states. USSR AS Press. Moscow. 468 p. (in Russian).
Borzenko, M.P. 1942. Caspian stellate sturgeon. News of Azerbaijani Fisheries Research Station. Baku. 114 p.
Caspian Sea. Ichthyofauna and commercial resources. 1989. Nauka. Moscow. 236 p. (in Russian).
Dvornikov, P.I. 1992. Daily ration and rhythm of stellate sturgeon feeding in the Middle Caspian. In: Biological resources of the Caspian Sea. Book of Abstracts of the First International Conference (September 1992). CaspNIRKH Press. Astrakhan. Pp. 96-97.
Detlaf, T.A., A.S. Ginzburg and O.I. Shmalgauzen, 1981. Sturgeon development. Nauka Press. Moscow. 224 p. (in Russian).
Dovgopol, G.F., V.P. Veshchev, T.V. Ozeryanskaya, 2000. Growth of stellate sturgeon in conditions of some fluctuation in its reproduction. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. Pp. 48-49.
Fish of Kazakhstan. 1986. Comp. By V.P. Mitrofanov, G.M. Dukravets, N.E Pesseridi. Nauka Press of Kazkh. SSR. Vol. 1.. Alma-Ata. 272 p. (in Russian).
Gadirneyad, H., M. Moghom, V. Ahtoman, 2000. Dynamics of stellate sturgeon population in southern part of the Caspian Sea. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. P. 60.
Kashentseva, L.N. 2000. Stellate sturgeon feeding in the Caspian Sea during the feeding season in winter. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. P. 60.
Kashentseva, L.N. 2001. The state of feeding of stellate sturgeon population in the Caspian Sea. In: Status of commercial species stocks in the Caspian Sea and their management. CaspNIRKh Press. Astrakhan. Pp. 171-184. (in Russian).
Khodorevskaya, R.P., G.F. Dovgopol and O.L. Zhuravleva, 2000. Dynamics of commercial sturgeon stocks in the Volga-Caspian region. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. Pp. 103-104.
Kim, Yu. A. and E.B. Bokova, 2000. Sturgeon reproduction in the Ural-Caspian region. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. P. 62.
Kochneva, L.A. 2000. Development of benthic fauna of the Middle Caspian in the area of sturgeon feeding. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. P. 65.
Kuliev, Z.M. and T.S. Zerbaliev, 2000. Present status of sturgeon population in the Azerbaijan sector of the Caspian Sea. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. P. 67.
Legeza, M.I. 1972. Importance of abiotic environmental factors for sturgeon (the family Acipenseridae, Pisces) distribution in the Caspian Sea. J. Voprosy Ichthyologii (Problems of Ichthyology) Vol. 121, 1: 13-24 (in Russian).
Legeza, M.I. 1973. The present distribution of sturgeons (the family Acipenseridae) in the Caspian Sea. J. Voprosy Ichthyologii (Problems of Ichthyology). Vol. 13, 6(63): 1008-1015 (in Russian).
Legeza, M.I., M.I. Pirogovsky and R.P. Khodorevskaya, 1989. Distribution, qualitative structure of populations and sturgeon abundance in the sea. In: Caspian sea. Ichthyofauna and commercial resources. Ch.3. Moscow. Pp. 27-76.
Perevaryukha, Yu.N. 1989. Genetic-population research of Russian and stellate sturgeon in the Caspian Sea. In: Sturgeon fisheries in the USSR water bodies. Astrakhan. Pp. 247-249. (in Russian).
Pesseridi, N.I., T.N. Shubina and A.P. Slivka, 1972. Comparative characteristics of age composition of stallate sturgeon harvested in the Volga and Ural Rivers. P.p. 130-131. Book of Abstracts of TSNIORKH Reporting Session. Astrakhan (in Russian).
Piskunov, I.A. 1983. Feeding and food supply of hatchery-produced sturgeon juveniles in the western part of the Northern Caspian. In: Biological principles of sturgeon culture. Nauka Press. Moscow. P.. 200-216. (in Russian).
Polyaninova, A.A. 1979. Daily feeding and diets of Russian and stellate sturgeon in the Northern Caspian. In: Biological principles of sturgeon fisheries development in the USSR water bodies. Nauka Press. Moscow. Pp. 170-180. (in Russian).
Shorygin, A.A. 1952. Feeding and food relations of Caspian fish. Food Industry. Moscow. 276 p. (in Russian).
Scientific principles of sustainable fishery, regional distribution of commercial species in the Caspian Sea. 1998. Belyaeva, V.N., V.P. Ivanov, V.P.Zilanov (ed.) VNIRO Press. Moscow. 167 p. (in Russian).
Stygar, V.M. 1984. Feeding and food relations of young sturgeons and other fish in the lower reaches of the Ural River. Author's Abstract. 24 p. (in Russian).
Tarverdiev, M.I. 1965. Importance of acclimatized organisms for Russian and stellate sturgeon feeding. In: Changes in biological complexes of the Caspian Sea over the last decade. Nauka Press. Moscow. Pp. 234-256. (in Russian). 
Veshchev, P.V. 1994. Scales of natural reproduction of the Volga stellate sturgeon under the present environmental conditions. Ecology, 2: 59-68 (in Russian).
Veshchev, P.V. 1977.The Volga stellate sturgeon maturation. J. Pybnoye Khozyaistvo (Fisheries), 3: 23-25 (in Russian).
Vlasenko, A.D., P.V. Veshchev et al. 2001. Assessment of the status of Caspian stellate sturgeon stocks and predication of its catch in 2002. In: Fisheries research in the Caspian Sea. (Results of research work in 2000). Astrakhan. Pp. 155-163. 
Voinova, I.A. and A.P. Alekperov, 1992. Fisheries requirements to water consumption in the Kura River depending on its runoff into the sea. In: Biological resources of the Caspian Sea. Book of Abstracts of the First International Conference (September 1992). Astrakhan. Pp. 74-76.
Zykova, G.F., O.L. Zhuravleva and E.V. Krasikov, 2000. Assessment of unaccounted and illegal catches of Russian sturgeon in the Volga River and Caspian Sea. In: Sturgeons on the Threshold of the 21st Century. Book of Abstracts of the International Conference (September 11-15, 2000). Astrakhan. Pp. 54-56.

Compiled by:

G.F. Zykova, ( CaspNIRKh, Astrakhan, Russia)
Yu.A. Kim, (KazNIIRKh Atyrau Branch, Atyrau, Kazakhstan)

Acknowledgements:

The authors are grateful to L.N. Kashentseva and Dr. A.A. Polyaninova for providing data on stellate sturgeon feeding during the river and marine periods of life, to I.M. Aminova for assistance in collecting data and structuring tables on the Ural stellate sturgeon, to Dr. E.V. Krassikov for providing data on stellate sturgeon distribution in the Caspian Sea.