Sturgeons – contemporaries of dinosaurs
107
Beluga has few enemies in the sea. The embryonic, larva and fry life-cycle
phases of beluga are the most vulnerable to contamination, oxygen defi ciency,
and predator fi sh.
Since young beluga in its fi rst year of life in the river and in the sea is a
benthophage species, it may compete in searching for food with the off spring
of other sturgeon species, gobies and carps.
The adult beluga can compete in searching for food with seals and sanders,
eating carps and, in particular, the Caspian roach. In the sea, beluga has most
competitive trophic relations with another major predator – the Caspian seal.
On
the other hand, the young seals are the sources of food for large belugas,
particularly in winter and early spring.
The beluga lives a very long life; certain species live up to 100 and more
years.
A 1.5-ton beluga was caught in 1827 in the Volga-Caspian area. In 1924,
a 1,228 kg fi sh was caught in the area of the Biryuchya Spit (Volga-Caspian).
On May 11, 1922, a female beluga weighing up to 1,220 kg was caught in the
area of the Volga River mouth. Belugas with an overall weight of 1,400 kg and
whose ovaries weighed 400 kg have also been found. A case is recorded when
a beluga with a weight exceeding 1,000 kg was caught near the Ural River
mouth, and its caviar weighed 180 kg. In 1973, a scientist from the Azerbaij an
Fishery and Sturgeon Breeding Research Institute caught a beluga weighing
over 1,000 kg. In spring 1988, fi shermen of the Neft chala region of Azerbaij an
caught two belugas weighing 690 and 727 kg. In April 1986, a beluga weighing
867 kg was caught in the Urals, and its caviar weighed 156 kg.
Sturgeons – contemporaries of dinosaurs
109
The construction of hydro stations on the Volga River and the blocking
of migration routes resulted in low replenishment of beluga stocks through
natural reproduction. The beluga has lost practically all of its spawning
grounds, and more than 90% of it is now artifi cially reproduced at commercial
hatcheries.
Overfi shing, poaching, and pollution of the rivers and the Caspian Sea
cause a sharp reduction of beluga populations. At present (since 2001), the
commercial caught of beluga has been banned; however, poaching is widely
spread, both in rivers and the Caspian Sea.
STURGEON GENUS – ACIPENSER
To date, 16
species are known in the genus Acipenser, and some of them
are endangered. Five of them inhabit the Caspian Sea.
The
Russian sturgeon is the most valuable and abundant sturgeon in the
Caspian.
Russian Sturgeon – Acipenser gueldenstaedtii Brandt, 1833
Zootaxy position:
Type: Chordata
Group: Osteichthyes
Order: Acipenseriformes Berg, 1940
Family: Acipenseridae Bonaparte, 1832
Genus: Acipenser Linnaeus, 1758
Species: Acipenser gueldenstaedtii Brandt, 1833
Latin name is given in honor of the Russian naturalist I.A.
Guldenshtedt.
Common names: Russian –
Russian sturgeon; Azerbaij an –
nere, rus neresi;
Iranian –khaviari rusi, tas; English –
Russian sturgeon
Related forms. The Persian sturgeon
– Acipenserpersius, Borodin; the
Atlantic sturgeon –
Acipenser sturio, Linnaeus; the Siberian sturgeon –
Acipenser
G.M.Palatnikov, R.U.Qasimov
110
baeri baeri, Brandt; the Baikal sturgeon –
Acipenser baeri baeri n.baicalensis,
A.Nikolskiy; the Amur sturgeon –
Acipenser schrencki, Brandt; the Sakhalin
sturgeon –
Acipenser medirostis, Ayres; the Adriatic sturgeon –
Acipenser
naccari, Bonaparte; the Chinese sturgeon –
Acipenser sinensis, Gray,
Acipenser
dabrianus, Dumeril; the Japanese sturgeon –
Acipenser kikuchii, Tanaka,
Acipensermultisculatus; the snub-nosed sturgeon –
Acipenser brevirostris,
Le Seuer; white sturgeon –
Acipenser transmontanus, Richardson; the lake
sturgeon –
Acipenser fulvescens, Rafi nesque.
Origin. There is no consensus on the origin of sturgeons. Some
ichthyologists
believe the genus Acipenser, as well as the genera
Polyodon and
Scaphirnynchus, originated in the territory of North America (the Mississippi
River). According to other explorers, sturgeon-like fi sh originated in the
territory of Central Asia in Tethys Sea basin.
Russian sturgeon
Distribution. The Russian sturgeon is endemic to the Pontic-Caspian
basin; inhabits the waters of the Caspian Sea, Sea of Azov, and Black Sea.
There are diadromus and non-anadromous forms of sturgeon. The
diadromus form has fast and slow matured varieties. Non-anadromous
(permanent dwellers of the river) forms are in the Volga,
Kama and, perhaps, in
the Ural River. The Volga river population is most abundant in the Caspian.
In the Sea of Azov-Black Sea basin, sturgeon comprises the following
populations: Black Sea-Caucasus (Rioni), Black Sea-Ukraine (Dnepr), and
Azov.
The Russian sturgeon from the Caspian enters the Volga for spawning,
fewer enter the Ural River, and very few enter the Terek, Sulak and Samur
rivers. Along the Iranian coast the sturgeon enters the Sefi d Rud River, and
rarely the Gorgan, Babol, and other rivers.