434 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



Table 179. Number of poly chaete families, genera and species 



Sea 



Families 

 Total Per 



number cent 



Genera 

 Total Per 



number cent 



Species 

 Total Per 



number cent 



The Bosporus region, the most saline sector of the Black Sea, gives shelter 

 to immigrants from the Mediterranean, which are not found anywhere else 

 in the Black Sea. Twenty forms of this type, including anthozoa echinoderms, 

 molluscs, polychaetes and others have been found there. 



The heterogeneity of the Black Sea fauna is conditioned, like that of the 

 Caspian Sea, by its past history and its lowered salinity. Its fauna comprises 

 three main components: (7) relict autochthonous fauna (commonly called 

 Pontic or Caspian) ; (2) Mediterranean immigrants, and (3) fresh-water forms. 

 These three elements are partly territorially separated, partly mixed ; this pro- 

 vided N. Knipovitch (1933) with an opportunity of giving a more detailed 

 classification of the Black Sea fauna according to its habitat. Knipovitch dis- 

 tinguishes the following groups mostly from the instances of fish (see also 

 Table 180). 



1. Pontic relicts, which have survived only in the parts of the Black Sea 

 with very much lowered salinity, especially in its inlets, and the fresh waters 

 of the lower reaches of its rivers. 



2. Pontic relicts inhabiting the Black Sea generally, but not met in the 

 Sea of Azov ; for example, some herrings : Caspialosa nordmanni, С pontica 

 and others. 



3. Pontic relicts inhabiting both the Black Sea and the Sea of Azov. To this 

 group belong the sturgeon family, some herrings, for example, the Azov 

 herring (Caspialosa maeotica), and C. tanaica etc. 



4. Mediterranean immigrants forming part of the settled population of the 

 Black Sea. This includes the main mass of organisms living in the Black Sea. 



5. Mediterranean immigrants, which appear in the Black Sea temporarily, 

 and do not multiply in it. 



Table 180. Composition of the Black Sea fish 



Total number Number of Number of Number of 

 of species and Pontic Mediterranean fresh- 

 sub-species relicts immigrants water forms 



According to 



Knipovitch (1932) 159 



According to 



Slastenenko (1938) 180 



28 

 31 



97 

 112 



34 

 37 



