THE CASPIAN SEA 629 



A most characteristic feature of the Caspian Sea ichthyofauna is the wide 

 range of its species between those of fresh and saline waters, with most varied 

 forms of adaptation to water of different salinity — from fresh water (with the 

 development of settled breeds) to the high salinity of the eastern inlets of the 

 Caspian Sea. Thus Caspialosa caspia salina lives at a salinity of 35-8% . 

 The western species Pomatoschistus caucasicus, Syngnathus nigrolineatus 

 caspius and Atherina mochon pontica caspia live and multiply at a salinity of 

 59-5% . Derzhavin correctly remarks that: 'such a variation in the behaviour 

 of Caspian fish is a manifestation of a wide adaptation during the Quaternary 

 history of this body of water to the changing conditions of water, climate and 

 salinity in different parts of the Caspian Sea'. The formation of one single 

 fauna from marine and fresh-water forms through a complex history of 

 a fauna of diversified genesis is graphically shown from the example of Caspian 

 fish ; in individual biological groups of this fauna fresh- water and marine forms 

 are found side by side. A prolonged coexistence under changing conditions 

 had erased the features linked with the early diversified genesis of species 

 and a single fauna was evolved, bound together by its conditions of existence 

 in a given body of water and by the history of the latter. 



Biological groups of fish. Among the fish of the Caspian Sea the group of 

 migratory fish inhabiting the Sea itself and moving up the rivers for spawning 

 is chiefly distinguishable. Vobla, Acipenseridae (except sterlet), Stenodus 

 leucichthys, salmon and some herrings may be included in this group. The 

 second group, of semi-migratory fish, includes primarily those which keep 

 to the less saline areas of the Sea and move up the rivers for spawning (pike 

 perch, golden shiner, carp and Pelecus), and secondly those which keep only 

 to the much more diluted waters of the river mouths and also move upstream 

 for spawning {Abramis bal/erus, Abramis sapa, Rutilus rutilus, Aspius aspius 

 and others). The third group consists of the native river fish. They are either 

 absent or rare even in the areas of the Sea with a reduced salinity (sterlet,Tinca, 

 Carassius auratus). Finally, the fourth group comprises fish which very rarely 

 enter waters of lowered salinity (marine pike perch, some varieties of the 

 South Caspian herrings such as Caspialosa braslmikovi grimmi, C.b. kissele- 

 vitschi, C. caspia knipovitschi, С braslmikovi autumnal is, Clupeonella and a 

 series of the species of bullheads and Benthophilus). Some of them move to 

 the shore for spawning, others make regular migrations from the Central 

 and Southern Caspian into the Northern. Marine pike perch and three breeds 

 of Southern Caspian herrings never enter the zones of lowered salinity at all. 

 Most of these groups include species of ancient autochthonous forms and 

 fresh-water immigrants. 



The great differences in the manner of life of the Caspian fish attracted the 

 attention of workers long ago. K. Kessler (1887), the author of the first 

 biological classification offish, based his work on his observations of Caspian 

 fish. 



Fish migration. The exceptional richness in migratory fish is the interesting 

 feature of the Caspian Sea (and also of the Sea of Azov). All the Acipenseridae 



