526 



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



cent of all the fish caught in the Azov-Black Sea basin; only 10 per cent of 

 this came from the Kerch Strait. In recent years the proportion has dropped 

 to 65 per cent or so. The yield from the whole area of the Sea of Azov is 

 73 kg per hectare (in some years up to 82 kg/hectare). 



V. CONCLUSION 



V. Pauli (1939) gives a very good description of the Sea of Azov as a eutrophic 

 sea: 'In the Sea of Azov not only do the reduction processes fall behind the 

 activity of the producers, but the production itself does not correspond to the 

 amount of biogenic compounds. According to the data for phosphorus pent- 

 oxide, and probably some other biogenic compounds as well, these are not 

 completely used up by the autotrophic population even at the time of maxi- 

 mum plankton development.' 



The masses of organogenic compounds brought down by the rivers Don 

 and Kuban into the Sea of Azov are only partly consumed by fish. Consider- 

 able quantities of them are converted into the organic compounds of plankton 

 organisms and are not used by fish. An appreciable part of the biogenic 

 compounds is carried away into the Black Sea. 



Datzko has given the biomass of the annual production of the main groups 

 of the Sea of Azov population {Table 217). 



Table 217 



Forecast of changes in the biological productivity of the Sea of Azov in con- 

 nection with reduction of river inflow. The hydrology and biology of the Sea of 

 Azov are bound to change as a result of hydrotechnical construction on the 

 river Don and the losses which it will involve in river inflow and in a certain 

 part of the dissolved or suspended substances brought down by the Don 

 into the Sea. A number of investigators have speculated on these possible 

 changes. 



The salinity of the Sea of Azov would increase by 2% with an assumed loss 

 of 10 km 3 of Don water, and by 5% with a loss of 20 km 3 . Taking into con- 

 sideration the fact that in the south Russian seas fisheries are concentrated 

 mainly in the less saline parts, V. Samoilenko (1955) supposes that a reduction 



