The Caspian is the biggest lake in the world: It is an endorheic, brackishwater natural reservoir. The Caspian has changed its look and dimensions as well as the composition of its vegetable and animal populations several times during its period of existence.

Saline or desalinated basins, alternating with each other, have occupied the place of the modern Caspian. Approximately 8-10 million years ago the Caspian was inhabited only by marine flora and fauna. The brackishwater organisms inhabiting it today only appeared later.

The lower seaweeds
The vegetable kingdom of the Caspian consists of 728 species, of which 723 are lower plants, i.e. seaweeds, and the other 5 species are higher water plants. The sea flora of the Caspian suffered radical changes under the influence of repeated salinizations and desalinations and this led to the enrichment
of the lake by freshwater species and to the extreme impoverishment of the sea flora: many species of seaweeds inhabiting seas of a normal salinity are absent in the Caspian.

Among the seaweeds of the Caspian, Aphanizomenon and Microcystis (Cyanophyta) are widespread. The seaweeds brought by the Volga are mostly present, in various occurrences, in the North Caspian. The South
Caspian is poorly inhabited by Cyanophyta because of the high salinity (13%) of the water.

Diatom seaweeds prevail in the plankton of the Caspian, but in the North Caspian Cyanophyta predominates in late summer and early autumn. Another species of the seaweeds, Pyrrophyta prevails in the summer plankton and forms an important part of food of the Caspian crustaceans. Other groups mostly inhabit coastal substrates and play an important role in feeding invertebrates.

The higher seaweeds
There are 5 species of higher plants in the whole territory of the Caspian. Among them sea grass (Zostera minor) is a perennial plant inhabiting sandy and sand-shell sea bottoms, except grounds covered with silt. Potamogetan recptinatus is
met with in coastal areas, Najas marina mostly inhabits bays. Both Ruppia spiralis and Ruppia maritime also are found in bays of the Caspian. Various species of crustacean larvae and young fishes live amongst them.

Most of the higher water plants are food for fishes and waterfowl. Vobla, wild carp and bream spawn on them in the bays of the Caspian.

The animal kingdom
The Caspian is inhabited by 1814 species of animals, 1394
of them are invertebrates, which make up 77.1% of the whole fauna. There are 100 species of fishes, 312 species of birds and one specie of mammals (the Caspian seal). The Caspian, in contrast to other seas, is not inhabited by many sea invertebrates such as Radiolaria, Spongia (particularly Caliarea, Corracus pengia),
Siphonophora, Scyphozva, Anthozoa, Ctenophora, Echiurida, Brachiopoda and others.

The fishes
The fishes form the base of the biological resources of the Caspian. Though the Caspian is inferior to open seas in the number of fish species, the great quantity of all fish individuals makes up for the scarcity of species to a considerable extent. The total quantity of some species, for example, sprats, makes milliards of individuals. Clupeidae (herring, 18 species), Cyprinidae (carp, 24 species) and Gobidae (bull-heads, 35 species) are predominant in terms of the quantity of species, making up more than 70% of the whole Caspian fauna.

Fishes of the Caspian are represented by species of different origins: herring and bull-heads have marine origins but sturgeon, salmon, carp, perch, pike, sheat-fishes, and sticklebacks have a freshwater origin.

Among these, the pike, perch and crucians have preserved the features of freshwater inhabitants until now, and they are usually met within the zones before the mouths of rivers. Pike-perch, vobla, bream, and wild carp inhabit the rivers as well as freshwater areas of the lake.

Only sturgeons are spread throughout the Caspian, coming to the rivers for reproduction. True sea fishes are atherina, (Atherina), grey mullet and flat-flash. All of them came to the Caspian from the Sea of Azov and the Baltic Sea and found here favorable conditions for growth and development (except flat-flashes). Far- Eastern salmon, humpbacks and Siberian salmon are also acclimatized. They are met with in the Caspian very rarely.

The Caspian is inhabited also by conger eel, which is often found near the Azerbaijan and Iranian seaboards.

Sturgeon fishing
Since ancient times, people living on the Caspian coasts have used the fish resources of the Caspian. According to Herodotus, 2500 years ago Scythian tribes wandering in the lower reaches of the Araks river lived mostly on the fishes of the Caspian.

In the 2^nd century AD sturgeons were fished in the Kura and a part of the production was exported to other countries. People also derived a business from sturgeon fishing in the Volga and the Ural for a long time. The findings of fish bones in the burial grounds of Privolgie and Prikamye, which date from the New Stone Age, demonstrate this. A glue produced from sturgeon bones, according to a Roman writer Elaine Klawdey (2^nd-3^rd century AD), was rated highly by ancient experts of ivory.

The caviar of the sturgeon has played a part in political affairs. Sea wars between Venice and Genoa were held
because of this caviar. The caviar led to Moskowvie and Toskan proprietors establishing diplomatic relations.
In the Middle Ages sturgeon fishing was the privilege of English kings, Novgorod and Moscow princes, Chinese
emperors, and Spanish and Russian monks. The sturgeon was also rated highly in later times.

On average, each hectare of the Caspian contains 81 kilograms of fish and this is six times as much as the Black Sea. Nevertheless a task in the near future is to increase the fish reserves of the Caspian.

It should be noted that 85% of the world catch of sturgeon comes from the Caspian. In 1994 about 4,000 tons of sturgeon were fished. At present the total number of sturgeon is about 140 million, from which 50.3% is osetra; 40.5% sevruga and 8.8% beluga, and only 0.4% is made up of the remaining sturgeon species.

The portion of the Volga-Caspian area provides 67.8% of the total catch, the portion of the Ural- Caspian area 24.7%, and the Kura-Caspian’s portion 0.9%. In the Iranian area of the Caspian the annual catch of sturgeon
makes up about 30 thousand centners, from which sevruga takes the first place (48.6%), osetra (45.8%) and beluga (5.5%) come next.

A modern sturgeon industry of the Caspian is based on bringing into agreement the regulations on fishing while maintaining natural and artificial breeding on a large scale. Eleven fish breeding plants put about 75 million young sturgeons into the Caspian every year.

Herring
The herring is also an important food-fish of the Caspian. Before the sixties it was one of the main objects of the fisheries. From 18 species of herring only six have an industrial significance: Alosa caspia caspia, A. saposhnicovi nicovi, A. brashnicovi brashnicovi, A. brashnicovi agraihanica, A. kessleri kessleri, A. kessleri volgenses. In recent times the catch of herring has reached 3,062 thousand centners and 80% of the total catch is made up of Alosa Saposhnikovi. In 1991- 1994 the catch of herring was reduced to 1.51 thousand tons a year.

This is explained by the emergence of unfavorable conditions for the development of the herring spawn and larvae between the mouth of the Volga and Volgograd. In the past, before the Volga was regulated, young herrings were carried down to the sea, but now only herring larvae get to the sea and this situation is leading to a decrease in numbers. Modern reserves of sea herring (400-500 thousand centners) are enough to increase the fishery a little.

But this should be done via selective fishing, to avoid damage to the reserves of other valuable fish, for example, the sturgeon.

Sprats, vobla, bream and others
Sprats are the most numerous family of fish in the Caspian. Among them Clupeonella engrauliformis takes the first place in catches, Clupeonella grimmi takes the second place and Clupeonella delicatura caspia follows them. C. engrauliformis inhabits the Middle and the South Caspian at a depth of 20 meters.

It avoids sea areas, where the salinity of water is less than 8%. C. grimmi is found at a depth of less than 50-70 meters. C. delicatula inhabits the whole of the Caspian, mostly in coastal areas at a depth of 50-100 m. It
breeds in shallow areas of the North Caspian, near to the Volga and the Ural.

Vobla also has some industrial significance. It breeds in the lower reaches of the rivers flowing into the aspian.
After the draining of the Volga has been regulated near to Volgograd, voblas moved for reproduction to the lower part of the delta, and an area of voblas in the North Caspian was abruptly reduced, and therefore the catch of vobla declined.

Bream does not play a leading role in the whole fishery of the Caspian. Mainly, it is met with at the mouths of rivers. The greatest reserves of breams are in the Volga-Caspian area. In summer breams are found in the sea areas where the water salinity is 4-8%. A lot of breams stay in desalinated areas of the Volga and the Ural for feeding and growth.

Kutum (Rutilus frisii kutum) is one of the valuable food- fishes. It inhabits, mainly, the Enzeliyskiy and the Great Kizilagachskiy gulfs. Usually it is found at a depth of 9-24 meters. Kutum fishing is carried out in Yalama, Lenkoran and by the Iranian coast. A catch of kutum in Azerbaijan is 1.1-5.0 thousands centners a year compared to 10.2 thousands centners a year by the Iranian seaboard.

Among the fishes of the Caspian that have little value, bull-heads play a very important role in feeding food-fishes (sturgeon, pike-perch etc) and the Caspian seals. However, the bull-heads fished as an additional catch
attached to the fishery of valuable fishes are directed to industrial processing.

The reserves of bull-heads are great. In the seventies on average 23.4 thousand centners of bull-heads were fished every year in the western part of the Middle and the South Caspian, including 378 centners fished on
the Azerbaijanian coast.

Artificial fish breeding
To date there are a lot of reserves of feeding-stuffs and owing to this fact it is possible to increase the population of valuable species of food-fishes by the expansion of artificial
breeding.

Twelve fish-hatcheries have been built on the Volga, five on the Terek, two on the Sefidrud and three on the Kura. The fish-hatchery built on the Terek produces 4 million young osetra and beluga and 2 million young kutum. About 100 million young sturgeons are released into the Caspian every year and 7% of the sum total comes from the fish-hatcheries on the Volga.

Industrial breeding of the Caspian salmon is put into practice by the Azerbaijanian Chaykend and hukhurkabala
fish-hatcheries and also by the Russian Tersk Fish-hatchey. About 634 thousand young salmons are put in the lake every year.

For industrial breeding of white salmon several additions to the Volga plants have been built in Kirzan, Volgograd and Alexandrovsk. The annual production of young white salmon gives 3.6 million individuals. The breeding of kutum is carried out in Iran, Azerbaijan and Russia (Dagestan), totaling 50-52 thousand individuals of larvae and young fishes.

For artificial breeding of Cyprinidae 16 spawning facilities with a total area of 16.7 thousand hectares operate
in the Caspian. Wild carp, bream, vobla, kutum, pike-perch and others are bred in these areas. The total production of young fishes comes to 2 billion individuals, of which 40-50% is made up of bream and wild carp.

To increase the fish reserves of the Caspian it is necessary to expand the scale of artificial breeding of the sturgeon. Construction of seven new sturgeon plants and the reconstruction of old plants as well as spawning facilities is required. It is necessary to carry out a reclamation of fish spawning in the Volga, the Kura, the Ural, and the Terek.