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V.P. Ivanov, S.I. Nikonorov, Yu. N. Perevaryukha
Caspian Fisheries Research Institute, Russia
Interdepartmental Ichthyological Commission, Russia
e-mail: kaspiy@astranet - interdepichthyocom@mtu-nt.ru

As to the information concerning the presence of Siberian sturgeon (Acipenser baerii) caviar in the caviar of Russian sturgeon (Acipenser gueldenstaedtii) supplied to the USA from Astrakhan, we can report that:

The description of sturgeon species was completed by the late ₁₉th century by outstanding scientists of that time (Berg, 1904). During the ₂₀th century, this problem was repeatedly examined by experts on the basis not only of morphometric characteristics and peculiarities of biology, but also using updated methods (biochemical, genetic). This allowed rather an objective classification and identification of species of the genus Acipenser. Specifically, the independence of the species A. barii and A. gueldenstaedtii is beyond doubt. In addition, the phylogenetic relationship was revealed between Siberian, Persian and Russian sturgeons (Birstein, De Salle, 1998; Sokolov, Vasiliev, 1989) which was associated with common ancestors that migrated into the Ponto-Caspian basin from Siberian rivers through the system of water bodies during the period of maximum freezing (Berg, 1928, 1949). Common phylogenetic ancestry gave rise to the affinity of genetic features of these fish species.

The results of studies of antigenic composition of serum proteins, fractional composition of hemoglobin and blood serum proteins, isoelectric focusing of hemoglobin, isoenzymic composition of muscular malate dehydrogenase and other biochemical characteristics show clear specific distinctions between Russian, Persian and Siberian sturgeons. At the same time, these data make it possible to regard Russian and Siberian sturgeons as the most affinitive species representing a common phyletic line (Bal, Karnaukhov, Geraskin, 1981; Vasiliev, 1999; Geraskin, 1979; Lukyanenko, Umerov, Altufiev, 1970; Perevaryukha, 2001).

The Russian sturgeon in the Caspian Sea has rather a complicated intraspecific composition. First of all, it should be noted that there are Russian sturgeon populations which display homing to certain spawning rivers. The largest of them are Volga, Ural and Kura populations. The Volga River population is the most abundant. There are also small populations spawning in the rivers Terek, Sulak, Samur and Sefidrud. The largest populations are divided into two seasonal races spring and winter that differ in the time of entering rivers and spawning seasons. The spawning population of Russian sturgeon is also divided into biological groups that are different in reproductive biology. I.A. Barannikova (1957) gave a description of four biological groups of the Volga River population of Russian sturgeon depending on the rate of gonad maturation and time of spawning: early and late spring, winter forms of summer and autumn run. Three biological groups (early and late spring, winter) were revealed in the Ural River population of Russian sturgeon (Gerbilsky, 1957).

The Persian sturgeon may also be divided into the Volga, Ural, Kura and Sefidrud populations. The Kura and Sefidrud populations are the most abundant. Like Russian sturgeon, the Persian sturgeon has two seasonal races: spring and winter. N.L. Gerbilsky (1950) described five biological groups in the Kura population of Persian sturgeon: early and late spring, spring form of summer and autumn run. Two biological groups were described in the Volga River population of Persian sturgeon -early and late spring, and one group (late spring) in the Ural River population (Artyukhin, 1983).

Thus, only Russian sturgeon has at least some twenty populations and biological groups while Persian sturgeon has not less than 18. In other words, the intraspecific composition of these species is too complicated which should be taken into account when performing investigations including those under CITES (Perevaryukha, 2001).

Anadromous migration of the greater part of Russian sturgeon (as well as beluga and stellate sturgeon) into the northern rivers - Volga and Ural indicates their northern origin. The spawning populations of sturgeons in the southern rivers of the Caspian Sea basin - Terek (Dagestan), Kura (Azerbaijan), Sefidrud (Iran), are not abundant and could appear later.

Because of removal of spawning sites due to river damming, the natural reproduction of sturgeons occurs mostly in the Volga (about 60%) and Ural (more than 30%) Rivers while southern Caspian sturgeons turned out to be on the verge of extinction. They may have been caught for culture purposes and are maintained at hatcheries now which facilitates their conservation.

Being aware of the fact that the Caspian sturgeon population is the most abundant in the sea (52.3 million specimens of beluga, Russian and stellate sturgeon in 1999) and the most diverse in species (six species), it was decided to prohibit the introduction of any other sturgeon species into the sea and rivers of the basin and rearing of sturgeon hybrids including those of indigenous fish species for their release into the basin in order to preserve the unique gene pool. This provision is observed at present by all the Caspian Sea States. Introduction of any living aquatic organism into the sea and rivers of the basin should be based on biological consideration, sound expertise, agreement with all the Caspian States. But unintentional invasion of some animals can not be excluded and individual species, mostly invertebrates, invade the Caspian Sea through the Volga-Don Canal. Just in this way, the Caspian Sea was invaded by comb jelly fish Mnemiopsis leidey that is responsible for a drastic decline in the biomass of plankton and planktivorous fish (kilka).

At the same time, it may be asserted with certainty that despite the fact that the Caspian Sea is not an absolutely isolated water body now, intentional or unintentional introduction of Siberian sturgeon into it is excluded. This species can not get into the Caspian Sea unintentionally because of a long distance, isolation and low abundance of the species, lack of possibility to transport it unnoticed and survival of fish during transportation. Intentional introduction of Siberian sturgeon into the rivers was not carried out. The captive breeding of Siberian sturgeon is conducted in small quantities in ponds isolated from natural water bodies, it is under strict control of Glavrybvod and the State Fisheries Committee of Russia that prevents their release or adventitious invasion of the rivers.

The output of commercial breeding of sturgeons (mostly bester) is rather small and the proportion of Siberian sturgeon is quite negligible. The fish breeding farm of the Scientific and Production Center "BIOS" (the Astrakhan Region) began the experimental production of caviar harvested from cultured fish.

During the whole 20^th century and especially in its second half, CaspNIRKH conducted regular studies of sturgeons in the basin: assessed their abundance and distribution in the sea, studied their feeding, growth, spawning, downstream migration of larvae and fingerlings. Many thousands of specimens were examined each year, fish from the control catch and commercial catches were analyzed. And for all those years, there were no cases of finding Siberian sturgeon or other species of this family unusual for the Caspian Sea basin either in experimental or commercial catches (Caspian Sea, 1989; Ivanov, 2000). Sturgeons in the Volga River and sea are studied, besides CaspNIRKH, by a number of research institutes of Russia and Caspian littoral states (Kazakhstan, Azerbaijan, Iran) that have never recorded Siberian sturgeon in catches either.

We have no reason to suggest that the caviar of Siberian sturgeon produced in Siberia can be sold through Astrakhan as that of Russian sturgeon to benefit commercially. Catches of Siberian sturgeon have always been rather small never reaching 100 tonnes since 1990 while in the past five years they may hardly have been more than 50 tonnes (Ruban, 1999).

Thus, the presence of caviar of Siberian sturgeon in batches of Russian sturgeon caviar supplied from Russia and, specifically, from Astrakhan is impossible. Siberian sturgeon was not seen in the Volga River which was witnessed by long-term data of regular investigations. Small quantities of sturgeons, mainly bester, have been reared in fish breeding farms. Catches of Siberian sturgeon have no practical commercial importance.

The suggestion that caviar of Siberian sturgeon was present in Russian sturgeon caviar from Russia which was based on the analysis of two small segments of mitochondrial DNA is thought to be the result of unrepresentativity of the method applied for its identification and supports the hypothesis of phylogenetic relationship between Siberian and Russian sturgeons that have several heterogenous biological groups.

Artyukhin, E.N. 1983. Differentiation of Persian sturgeon populations and prospects of its captive breeding in the Volga River. P.p. 54-61. In: Biological principles of sturgeon culture. Nauka. Moscow.

Barannikova, I.A. 1957. Biological differentiation of the Volga-Caspian sturgeon stock (in view of the objectives of commercial sturgeon culture in the Volga River delta). In: LSU Scientific Notes. Biological Science, 228 (44). Fish stock reproduction in view of hydroelectric development. Part 1: 54-71.

Bal, N.V., G.I. Karnaukhov and P.P. Geraskin, 1981. Characteristics of the fractional composition of serum proteins in two populations of Siberian sturgeon. P.p. 27-28. In: Rational principles of sturgeon culture management. Volgograd.

Berg, L.S. 1928. On the origin of northern elements in the Caspian fauna. USSR AS Reports. Series A, 7:107-112.

Berg, L.S. 1949. Fish in fresh waters of the USSR and adjoining states. Parts IIII. Moscow-Leningrad. 1382 p.

Berg, L.S. 1904. Zur Systematic der Acipenseriden. Zool. Tuz. XXI, 22: 665-667.

Birstein, V.J. and R. De Salle, 1998. Molecular phylogeny of Acipenseridae. Molecular phylogenetics and evolution. Vol.5, 1:141-145.

Caspian Sea. 1989. Ichthyofauna and commercial resources. Nauka. Moscow. 235 p.

Gerbilsky, N.L. 1950. Biological groups of the Kura sturgeon (Acipenser gueldenstaedtii persicus Borodin) and grounds for its hatchery rearing. USSR AS Reports. V.71, 4: 785-788.

Gerbilsky, N.L. 1957. Ways of development of the intraspecific biological differentiation, type of anadromous migrants and the problem of migration impulse in sturgeons. In: LSU Scientific Notes. Biological Science, 228 (44). Fish stock reproduction in view of hydroelectric development. Part 1:11-32.

Geraskin, P.P. 1978. Specific fractional composition of sturgeon blood hemoglobin and dynamics of its development in early ontogenesis. Author's Abstract of Dissertation for Ph.D. Degree in Biology. Sevastopol. 20 p.

Ivanov, V.P. 2000. Biological resources of the Caspian Sea. Astrakhan. 100 p.

Lukyanenko, V.1., Zh.G. Umerov and Yu.V. Altufiev, 1970. Antigenic features of serum proteins of three species of the genus Acipenser. USSR AS News. Biology, 1:148-150.

Perevaryukha, Yu.N. 2001. Present state of Caspian sturgeon biodiversity and some problems of their specific identification by molecular-genetic method including caviar. In: Extended Abstracts. The _4th International Symposium on Sturgeon. Oshkosh, Wisconsin, USA. July 8-13, 2001.

Perevaryukha, Yu.N. 2001. On the problem of phylogenetic affinity of Russian (Acipenser gueldenstadtii) and Siberian (Acipenser baerii) sturgeons (data on biochemical taxonomy). In: Extended Abstracts. The ₄th International Symposium on Sturgeon. Oshkosh, Wisconsin, USA. July 8-13, 2001.

Ruban, G.I. 1989. Siberian sturgeon Acipenser baerii Brandt (structure of the species and ecology). GEOS. Moscow. 235 p.

Sokolov, L.I., V.P. Vasiliev, 1989. Acipenser baerii Brandt, 1869. Pp.263-284. In: The freshwater fishes of Europe. Vol. I, II. General introduction to fishes Acipenseriformes. AULA-verlag. Wiesbaden.

Vasiliev, A.S. 1999. Heterogeneity, polymorphism and functional characteristics of fish hemoglobin. Author's Abstract of Dissertation for Doctor's Degree in Biology. Petrozavodsk. 41 p.

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