THE CASPIAN SEA 643 



Yield cf fish. Fish yield in the Northern Caspian in 1935 was about 31-6 

 kg/hectare (24 kg/hectare for benthophages), in the Sea of Azov 73 kg/hectare, 

 in the Aral Sea 4-5 kg/hectare, and in the North Sea about 17 kg/hectare (in 

 ponds 60 to 160 kg/hectare, and when fertilized up to 2,000). Thus the yield of 

 fish from the Caspian Sea is comparatively high. The FIB coefficient for these 

 Seas is also most significant. For the Northern Caspian it is about 1/12, for 

 the Sea of Azov 1/20, for the Aral Sea 1/50, for the North Sea 1/140. Hence 

 North Caspian benthos is utilized in the most efficient manner, and evidently 

 there is strong rivalry for food between its consumers. Partly in connection 

 with this, and partly owing to the existence of an abundant provision of 

 food in the form of nereids* in the Sea of Azov, fish grow in it much better 

 than in the Caspian Sea. 



Schorygin's comprehensive examination of fish nutrition in the Northern 

 Caspian makes it possible to come to a most reliable prognosis of the state of 

 fish feeding under possible changes in the conditions and surface of the body 

 of water. On the other hand, the examination of Caspian fish nutrition and a 

 comparison of its results with data on the growth of commercial fish points 

 to the existence of competition between some fish and to a considerable 

 rivalry as regards provision of food. This in fact led to the idea that the Cas- 

 pian Sea could be widely used for the acclimatization of the Mediterranean 

 (Azov-Black Seas) fauna. 



Commercial fish resources. The rough quantities of fish resources of the Cas- 

 pian Sea given by some authors are based mostly on data from commercial 

 statistics and on the examination for age of catch. 



The Caspian Sea occupied the first place in our fisheries during the first 

 two decades of this century. Later, however, owing to vigorous development 

 of fisheries in the Barents Sea and in the Far Eastern Seas the Caspian trade 

 dropped to third place. Recent yields of the Caspian fisheries were only 

 65-4 per cent (4-3 million centners in 1954) of the 1913 catch (L. Berdichevsky, 

 1957). This reduction has affected the most valuable breeds offish — herring, 

 vobla and pike perch; the yield of Acipenseridae is about half that of 1913, 

 but it has remained on the same level since 1930. Sprat fishery has developed 

 greatly. The fisheries of the Caspian Sea have changed a great deal during the 

 last 30 years {Table 274). 



In 1956 the catch of fish in the Caspian Sea was 4-3 million centners 

 (Table 275). 



* The data given refer to the period before the implantation of Nereis. 



