5 cm. Sharply outlined rings, corresponding to the first winter, are few. Well marked rings can 

 be seen in Figure 5 (structure of annual rings of summer-spawning Iceland herring) and Figure 6 

 (structure of first ring of same scale greatly enlarged). 



TABLE 2. AGE COMPOSITION OF SUMMER-SPAWNING HERRING IN ICELAND 

 AND FAROE REGIONS.- 



The first ring on a scale can be traced much better by modifying the lighting of the prepara- 



tion. 



A characteristic peculiarity of the structure of the scale of the summer -spjawning herring 

 are the fragmented sclerites /2/in the center of the scale (Figure 7, greatly magnified). Such a 

 structure of the center of the scale in the spring herring is never observed (Figure 8). 



For calculating the rate of growth of the summer -spawning herring, we used a sample ob- 

 tained on August 16 in the region south-west of Iceland. Table 3 gives the rate of growth in separ- 

 ate growth categories . 



The average increment for the first year (increment for the first 5-6 months of life) varies 

 from generation to generation within the limits 3.3 to 4.6 cm., the average being 3.8 cm. At the 

 end of the second year, the young reaches 9.2 cm., varying from generation to generation within 

 the limits 8.4 to 10.0 cm. The average length of a herring v/ith three rings is 16.0 cm., the limits 

 of variation being 12.0 to 18 cm. 



Thereafter, beginning at 4 years, the annual increments decrease; herring with 5 rings are 

 24 to 25 cm. in length; at age 9-10 years herring reach a length of 29-30 cm. 



It is characteristic that the younger age categories, examined in Table 3, have a higher rate 

 of growth than the older categories . For example, the length of a herring at the age of three in the 

 four -year-old categories is 18.9 cm., in the seven-year-olds 16.8, in the ten-year-olds 16.9 cm. 



1/ Number of annual rings counting first ring, which is formed in the first winter. 



174 



