THE SEA OF AZOV 521 



would correspond approximately to 600 to 900 thousand tons of fish, i.e. 

 similar results are obtained by both methods.* 



Feeding offish. The high benthos- and plankton-productivity of the Sea of 

 Azov determines the exceptional qualities of this body of water as a feeding 

 ground not only for the Azov fish, but also partly for those of the Black Sea 

 (herring, anchovy, red mullet, grey mullet, etc.). Herring, anchovy and 

 other pelagic fish prey on zooplankton; bullhead, Percarina, Benthophilus 

 and Atherinopsis feed on benthos. In their turn they serve as food for pike 

 perch. Some fish, like striped mullet (Mugil cephalus) and mullet {Mugil 

 auratus), live mostly on detritus. 



So far there has been no general summary of fish nutrition in the Sea of 

 Azov like that made by A. Schorygin for the Caspian Sea. The fullest quan- 

 titative data exist on the nutrition of anchovy and some other plankton-eating 

 fish (A. Okul, 1939 and A. Smirnov, 1938). Of the benthos-eating fish the 

 bream alone has so far been thoroughly studied (V. P. Vorobieff, 1938). 

 Finally, for the predatory fish there are some data on the nutrition of pike 

 perch (N. Tchougounov, 1931; V. Maisky, 1939 and V. P. Vorobieff in 

 manuscript). In recent years comprehensive studies of the nutrition of Sea 

 of Azov fish have been made, and were published in 1955 (E. Bokova, 

 M. Zheltenkova, V. Kornilova, V. Kostyuchenko, E. Fesenko and M. Sheinin). 



Plankton-eating fish. During periods of its multiplication the mass of plankton 

 in the Sea of Azov must be not less and very probably larger than the mass of 

 benthos. Taking into account the fact that the production of the Azov phyto- 

 plankton must considerably exceed that of benthos, it becomes clear that the 

 plankton of the Sea of Azov has a higher productivity than its benthos. The 

 intensively productive Azov plankton serves as a plentiful source of food for 

 the fish which gather there from the Caspian Sea and from the rivers to fatten. 



The Azov anchovy {Engraulis encrassicholus maeoticus) — one of the main 

 commercial objectives of the Black and Azov Sea fisheries — enters the Sea 

 of Azov in the spring (April-June) for intensive feeding and spawning. The 

 anchovy leaves the Sea of Azov from the second half of August till the end 

 of November ; it hardly feeds at all during its stay in the Black Sea. 



Coming into the Sea of Azov the anchovy begins to feed intensively (Fig. 

 248). A. Smirnov (1938) and A. Okul (1940) have shown that the western half 

 of the Sea serves as a specially rich feeding ground. Plankton forms the main 

 part of the anchovy's food ; when this is short, it feeds on benthos (poly- 

 chaetes, molluscs). The anchovy's feeding proceeds intensively and by June 

 its repletion index is 128; by July it is 117. In some individual areas of the 

 Sea its repletion index may be even higher (up to 210). In the coastal areas 

 in June it feeds mainly on worms (40 per cent), copepods (30 per cent), bar- 

 nacles (13 per cent) and molluscs (10 per cent). At that time phytoplankton 

 constitutes a small part (2 per cent) in the anchovy's diet. In some individual 



* The census of anchovy carried out recently from the air (I. Golenchenko, 1947) 

 leads to the conclusion that the resources of anchovy in the Sea of Azov are considerably 

 larger. 



