THE SEA OF AZOV 535 



Gammarus, Ostracoda and Artemia ; and in the southern only with Artemia, 

 which all dies out in the second half of the summer. 



In the central and southern Sivash the biocoenoses acquire a sharply pro- 

 nounced oligo-mixed character and are really a combination of two species, 

 Chironomus and Artemia. In summer the mean biomass of these organisms 

 is 18-8 and 2-3 g/m 2 , in autumn 24-5 and 0-5 g/m 2 , in winter 2-7 and 00 g/m 2 , 

 and in spring 7-7 and 0-03 g/m 2 respectively; Ostracoda and Ephydra are 

 mixed with these two forms in small numbers only. 



Together with Artemia salina and Chironomus, Cladophora siwaschensis, 

 which inhabits the central and southern Sivash in vast numbers, gives this 

 area its particular character. 



On the whole benthos biomass decreases gradually as one moves farther 

 into the Bay ; this can be seen on the charts in Fig. 254. On the other hand we 

 observe that sites of increased biomass as well as the main vegetation growths 

 lie close to the eastern shores. 



In winter the benthos biomass of all the biocoenoses falls sharply. 



The mean annual biomass of the outer half of the northern Sivash is equal 

 to 360 g/m 2 , that of the inner 140 g/m 2 . The mean annual biomass of the 

 central Sivash comprises 22 g/m 2 , and of the southern 4-26 g/m 2 . 



The macrophytes play an important part in the phenomena of biological 

 production in the Sivash. In the first northern Sivash, where Cladophora 

 is weakly developed owing to low salinity, there are Zostera and Ruppia ; in 

 the rest of the Sivash Cladophora produces a very high biomass. Owing to 

 the large amounts of Cladophora in the central and southern Sivash, the mean 

 annual total biomass of the whole (zoo- and phyto-) benthos is found to be 

 approximately uniform throughout the area : 



1st northern Sivash 564 g/m 2 



2nd northern Sivash 514 g/m 2 



Central Sivash 257 g/m 2 



Southern Sivash 515 g/m 2 



Fish 



Of the 12 species of fish living permanently in the Sivash the flatfish Pleuro- 

 nectes flesus luscus, some bullheads, pipefish, sea horses and sticklebacks 

 may be noted. Of all these species only the flatfish and the bullhead (Zostricola 

 ophiocephalus) have some commercial significance. 



Eight species of fish (all commercial) enter the Sivash to feed : two species 

 of grey mullet (Mugil auratus and M. cephalus), anchovy (Engrau/is encras- 

 sicholus maeoticus), herrmg(Caspiolosa maeotica), Atherina {Atherina pontica), 

 jackfish {Trachurus trachurus), garfish (Be/one acus) and bullhead (Gobius 

 fluviatilis). 



Finally there are about 30 species of Azov Sea fish which occasionally visit 

 the Sivash. 



The limits of the distribution of some fish are given in Fig. 255. 



Fish fed in the Sivash grow faster and fatter. Grey mullet, which goes into 

 the Black Sea to spawn, is particularly fat. 



