shores and in the open zones of the Barents Sea for a longer period of time . Thus the rate of return 

 migration of the growing herring is undoubtedly conditioned by the growth rate and age at which they 

 become sexually mature . These same factors account for the fact that Norwegian herring in the 

 southern Norwegian provinces migrate away from the shores earlier than schools populating the 

 northern fjords. 



The varying increment observed in different herring year classes is a result of a very 

 complex sum of factors, to provide an analysis of which would be an almost impossible task at this 

 time . The connection between the growth rate of different year classes and the number of speci- 

 mens forming these year classes can be revealed with great precision. All the abundant year 

 classes are characterized by hig^ growth indices . 



Table 2. RELATIVE NUMBERS OF SPECIMENS FORMING DIFFERENT YEAR' CLASSES OF 

 MURMAN HERRING, AREA OF THEIR PROPAGATION, AGE AT WHICH THEY BE- 

 COME SEXUALLY MATURE, AND DURATION OF THEIR STAY IN BARENTS SEA. 



Similar regularity has been established for the herring from other regions and a number of 

 other fish species . Moreover, the reason for the decrease in the growth rate of the herring of 

 abundant year classes Is attributed as a rule to the intraspecies relations , which are a result of 

 llie excessive population density . 



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