524 



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



eating fish in the Sea of Azov (Fig. 249), he calculated the total amount 

 of plankton consumed. In 1937 this quantity for the Sea of Azov was 

 1,700,000 tons, and for the Gulf of Taganrog 200,000 tons. This amount is 



ANCHOVY 



*esoUP££--^ , 



60 ui — """ У 



У 



20 



4 PLANKTON 



.1.1 dl 



1931 



1935 



1936 



1937 



Fig. 250. Alterations from year to year in the development of plankton and 

 anchovy resources in the Sea of Azov (Okul). 



considerably higher than the plankton biomass observed at any moment of 

 the year. Azov plankton-eating fish consume no less than 1,200,000 tons of 

 Copepoda alone, and for them the P/B coefficient is hardly less than 30. It is 

 interesting to note that Copepoda — the main food reserve of the plankton- 

 eating fish— is, like Cladocera and Cirripedia larvae, used only in small 

 quantities as food by benthos. 



Finally, over a number of years Okul likewise established for the Sea of 

 Azov a certain direct dependence between the amount of plankton and the 

 fish preying on it for the Sea as a whole and for some points in it, by means 

 of individual catches (Fig. 250). The yield of fish is usually large when the 

 plankton they feed upon is abundant. 



Benthos-eating fish. Some breeds of Azov Sea benthos-eating fish prefer a 

 definite quarry. Bullheads (Gobius melanostomus) feed preferably on clam- 

 worms, Mytilaster and Syndesmya. Bream chooses the same quarry, and adds 

 crustaceans and Hydrobia as well. Starred sturgeon feeds mainly on crabs, 

 worms and bullheads ; sturgeon on Syndesmya, Cardium and worms ; roach 

 on Mytilaster, Syndesmya, Hydrobia, crustaceans and worms. As has already 

 been shown by Tchougounov the Azov Sea benthos is suitable for fish to feed 

 on almost exclusively. 



