'•^NM^.,-**^" 



Figure 6. Structure of first annual ring of summer spawning Iceland herring. (Enlarge- 

 ment of Figure 5). 



The young of the summer -spawning herring during an incomplete first year reach 4 to 4.5 

 cm. The summer -spawning herring has the same dimensions in March, i.e. at the moment when 

 the larvae of the spring race hatch out. During the second year, the young of the summer -spawning 

 herring reach 9 10 cm., increasing, that is, by 5 to 5.5 cm. The young of the spring- spawning 

 herring during the same period of growth reach 8 to 8.5 cm. Thus, the young of the summer race 

 in their second year have a smaller increment than the young of the spring hatching during the 

 same period of time . 



These data create the impression that the young of the siunmer- spawning race have no 

 growth advantages in their second year of life over the young of spring origin, in spite of the fact 

 that at the beginning of the second growing period they already have a length of 4 cm. We shall have 

 to draw a different conclusion if we reproduce the weigfit increments of the young of the two races 

 during the same period of time . The weight of the young of the summer race at the beginning of 

 the second year of life should be about 0.3-0.5gm. By the end of the summer, their weight should 

 reach 5-6 gm. For example, the weight increment for the second summer is 5 gm. The weight 

 increment for the young of the spring race for the first year of life is 3-3.5 gm. Thus, in weight 

 indices the young of the summer spawning herring during the first year grows more than the spring 

 race by 1.5-2 gm., i.e. by more than 1.5 times. - 



1/ In determining the weight of the young for the above calculations we used the proportions of 

 weight to length in young herring collected at Murmansk, 



176 



