TABLE 11. DIAMETER IN MM. OF EGGS OF SUMMER -SPAWNING AND 

 SPRING-SPAWNING HERRINGS (PERCENTAGES). 



TABLE 12. NUMBER OF EGGS IN 1 GM. , FOR SUMMER AND SPRING- SPAWNING 

 HERRINGS (PERCENTAGES). 



As a result of the considerable difference in the size of the eggs in the two races, 

 summer herring has a higher fecundity than the spring Atlantic -Scandinavian herring. 



the 



Table 13 gives data on the fecundity of summer and spring herring of the same size and 

 this gives even stronger grounds for declaring that there are fundamental differences in the fecun- 

 dity of the two races . 



Thus, the fecundity of the siunmer-spawning herring is somewhat more than twice as high 

 as that of the spring- spawning herring of the same size. 



Figures 9 and 10 show the fecundity in conjunction with age and size of the summer herring 

 of Iceland and the Faroes and the spring Atlantic -Scandinavian herring. The difference between 

 the two races as regards fecundity is great, as Figures 9 and 10 show. 



One should note the non-parallel nature of the fecundity curves of the two races. Figure 9 

 shows the dependence of the fecundity on the length of the fish. In the summer herring, fecundity 

 increases as the size changes, up to and including the largest fishes; in the spring herring, after a 

 length of 30-31 cm. has been reached, the fecundity increases only slightly. 



Farran notes in his work (3) a higher fecundity in the autumn- spawning herring of the Sea 

 of Iceland. According to L. A. Rannak, a higher fecundity is to be noted in the autumn sprat as 

 compared with the spring sprat. 



The higher fecundity of the summer and autumn populations in comparison with the spring- 

 spawning herring is their distinctive characteristic and this, in our opinion, should be considered 

 an adaptation which compensates for the greater mortality of the young of the summer and autumn 

 herrings in the first winter of their lives . 



186 



