Principal habitats (marine and wetlands)
The Caspian Sea offers a variety of habitats in which
well-adapted species thrive.
1.1. Principal habitats for fish species
For a fish to complete its life cycle it must move through 3 different habitats: spawning
habitat, pasturing habitat and wintering habitat. For fish species with limited migration
range these three habitats coincide.
Semi-migrating fish species may find pasture habitats out
at sea, but during the wintering and spawning seasons they move to rivers. Some marine
fish carry out considerable migrations within the seawater area, while others may inhabit
relatively limited areas of the sea. The majority of the Caspian fish species inhabit the
coastal zone of the sea at depths ranging between 50 – 70 m.
Semi-migrating fish species:
These fish spawn in the deltas and downstream reaches of rivers and use the fresh water
deltas as pasture habitats. The optimal levels of salinity for most of the commercial fish
is approximately 8g/l. During years of high water levels, optimal saline waters cover all
of the northern Caspian as well as coastal areas adjacent to the river mouths within the
Middle Caspian zone.
Migrating fish species:
Sturgeon – the most valuable commercial fish - spawn in the rivers of the Caspian
basin. These fish migrate upstream from the river basins for hundreds of kilometers.
Sturgeons select areas with pebbly or hard sandy ground as spawning grounds. However, the
construction of dams have been restricted fish monement to the lower reaches of the rivers
prevent the sturgeon from migrating up the rivers to spawn and has led to a decrease in
the natural reproduction. Previously, 53 spawning grounds existed in Kura and 290 in
Araks, however only 5 in-channel spawning grounds remain in this nine system with an area
of 112.8 hectares (Voinova, Alekperov, 1992).
Marine fish species:
Commercial marine fish of live throughout the Caspian Sea. Different geographical regions
within the sea play specific roles: the shallow northern regions are important for
reproduction as well as for development at early stages of life. Typical fish found to
reproduce in the northern Caspian region include the Dolginka herring (Alosa
brashnikovi brashnikovi), the big eye shad (Alosa saposhnikovi) as well as the
ordinary sprat (Clupeonella delicatula caspia). The Middle and Southern Caspian
regions are feeding and fattening areas. The Caspian marine species do not have any
clearly expressed wintering period. This can be attributed to the consistent climatic
conditions year round which leads to ongoing development of fodder organisms. These fodder
organisms act as a continual food source for the fish.
1.2. Principle habitats for bird species
The Caspian Sea is situated on major migratory routes for many bird species (Dolgushin,
1960-1974; Belik, 1996; Birds of USSR, 1987, 1988; Fauna of USSR. Birds, 1961, 1962; Birds
of the Soviet Union, 1952), and it is therefore of important value for the whole of
Eurasia. The majority of migratory birds stem from the Siberian-Asian region. In the
autumn the birds concentrate on the northeast and northern coasts of the Caspian.
Gradually, they begin moving along the western coast towards the south. At this point
different species may take different routes; some continue moving south along the western
coast others migrate further west along the Caucasian mountain range. The birds
originating from the central and northwestern districts of Russia migrate to the seacoast
along the Volga. In the delta area of the Volga this stream of migrant birds merges with
those from Asia. The Ural and Emba rivers are also important migratory paths. During
spring, the migration routes move back in the opposite direction.
1.3. Principle habitats for mammals
The only sea mammal living in the Caspian Sea is the seal. In the winter the seals
concentrate in the Northern Caspian, near edges of ice packs, where they carry out their
whelping, and molting. A small proportion of seals remain on islands near the coast of
Turkmenistan throughout the winter. In the summer the seals migrate to the Middle and
Southern Caspian in order to fatten up. However, a few do remain in the Northern Caspian.
The coastal mammals live mainly throughout coastal strips
in bushes and reed thickets. Typical mammals to be found in these habitats include wild
boar, otter, European mink, striped raccoon and muskrat. Many species of rodents and hares
may inhabit coastal areas characterized by steppe and semi desert environments. Species
such as the saigak antelope (Saiga tatarica) as well as the djeiran (Gasella
subgutturosa) can be found within the desert and semi-desert ecosystems along
the coastal regions. Three herds of saigak (Saiga tatarica) live in the northern
near-Caspian zone: the Ustiyur herd (between the Caspian and Aral Sea), Guriev herd (area
between the Volga and Ural Rivers) and the Kalmyk heard. Since the prohibition of saigak
hunting (1991) their number has increased to 300 thousand. Saigaks are migratory and may
migrate as far as 300-500km. However, in recent years no considerable migration has been
observed. Most of the saigak stock stay within the southern regions of Astrakhan. Recent
migrations to the coast during wintertime was observed only in saigak herds living between
the Volga and Ural Rivers.
|
