industry, which now conducts fishing on these herring along the entire extent of their migration 

 paths , from the spawning grounds to the polar front and back . 



Simultaneously with the movement of the main bulk of Norwegian herring to the feeding 

 grounds in northern latitudes, a portion of the schools feeds in Icelandic waters. The latter fact 

 has been recently confirmed by the results of the tagging, as outlined in the 132nd volume of the 

 Rapports Proces Verbaux (46), 



The type of tag used by Norway and Iceland can be detected only by means of special mag- 

 netic installations and therefore, cannot contribute to the formation of a correct conception of the 

 migration paths of herring. These tags are recovered only where there exist the magnetic installa- 

 tions, i.e. in Iceland and Norway. On board our ships, the internal tags cannot be detected. 



We believe that only a small portion of Norwegian school feeds in Icelandic waters . The 

 course of migration of that school to Iceland passes along the southern edge of the East-Iceland 

 current . 



Growth and sexual maturation. 



A correct idea of the development of Atlantic-Scandinavian herring may be obtained only 

 after their biological peculiarities have been studied in detail . The isolated existence of different 

 biological groups and formation of these groups by lengths, and the drastically varying individual 

 growth rate are the main obstacles to the solution of our problem. 



When determining the sizes of herring according to the data obtained through direct obser- 

 vations, we knowingly arrive at erroneous conclusions, since within the borders of different re- 

 gions occupied by individual biological groups the prevalent age groups alone have the length close 

 to the mean indices . The lengths of younger and older herring deviate considerably from the mean 

 figures . 



If we endeavored to establish the average size of herring of the Lofoten-Barents school on 

 the basis of data collected in the southern zone of Barents Sea, we would arrive at a relatively 

 correct conclusion only concerning the length of the first three- and four-year-old groups. The 

 lengths of fishes of the older age groups will be determined incorrectly and be much lower than the 

 established mean length . This is easily understandable in view of the fact that the herring having 

 a hi^ rate of growth leave the southern zone of the Barents Sea earlier than the herring developing 

 at a slower rate. 



The mean length of herring of different ages may be established on the basis of data obtained 

 througti direct observations only according to the prevailing age groups of different biological group- 

 ings. Mean dimensions of 2- and 3-year-old herring may be determined in the regions of mass 

 development of small herring, the length of fishes at the stage of sexual maturation - according to 

 the data obtained from the regions of pre-spawning concentrations, and so forth. 



Determination of the growth rate of herring by scales, according to the method of back cal- 

 culation, involves errors identical to those committed when applying the method of direct observa- 

 tions. Young specimens found in the schools that are formed of older age groups are character- 

 ized by a very hig^ growth rate and vice versa, the old herring found among younger fish have a low 

 rate of development . 



The range of variations in the growth rate among Atlantic -Scandinavian herring is very 

 large. Five-year-old specimens from the Barents Sea usually reach 22.5-23 cm. in length. In the 



50 



