10 

 The Sea of Azov 



I. GENERAL CHARACTERISTICS 



The Sea of Azov is a body of water attached to the Black Sea which is remark- 

 able in many respects. It is essentially a broad, very shallow inlet of the Don, 

 with water only slightly saline. Owing to a number of circumstances it is 

 supplied with abundant mineral substances. 



A rich bottom-population, an abundance of organic substances, great 

 warmth in summer, and a readily established saline stratification cause the 

 upper limit of the reduction zone to rise easily from the sea-floor into the 

 water of the deepest, central part, with the consequent phenomenon of suffo- 

 cation of the bottom-fauna. 



The Sea of Azov is populated mainly by the most euryhaline forms of the 

 Mediterranean fauna, chiefly molluscs, which are exceptionally abundant 

 there. Relict Caspian Sea fauna lives only in the most eastern corner of the 

 Gulf of Taganrog. 



For a large number of Black Sea fish and for some river fish the Sea of 

 Azov is a plentiful feeding ground in the warm season of the year. 



The Sea of Azov is the most productive sea in the world, its fish catch being 

 80 kg/hectare in some years. 



II. HISTORY OF EXPLORATION 



First period 



The first reliable information about the fauna of the Sea of Azov resulted 

 from the research of A. Ostroumov (1892, 1896, 1897) and V. Sovinsky 

 (1894, 1902). During the first fifteen years of the present century biological 

 collections were made in the Sea of Azov by N. Borodin (1901) and S. Zernov 

 (1901). All these investigations were concerned with classification of the fauna 

 and the Sea as such was hardly studied at all, either as regards its hydrological 

 conditions or its biology. 



Second period 



Investigations made in recent years have led to a situation where the Sea of 

 Azov can now perhaps be placed among those seas of the u.s.s.r. which have 

 been most comprehensively studied. From 1923 to 1927 the Azov and Black 

 Seas scientific-industrial expedition, under the leadership of N. M. Knipovitch, 

 worked in the Sea of Azov. N. Tchougounov (1926), a member of this expedi- 

 tion, has given in his work a general picture of the quantitative distribution 

 of the fauna and some general principles of this distribution. An elaborate 

 taxonomic-faunal investigation of the most interesting group of relict crus- 

 taceans of the basin of the Sea of Azov was carried out by A. Martynov 

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