million grams 

 n 



25 JO 3S M 



isso nss 



Figure 13. Catches of herring obtained in Norwegian waters. 1.- smaU; 2. - fat; 3. - 

 winter herring. 



As is well known, there exist in Norway three types of herring fisheries - for adult herring 

 during the spawning season, for fat sexually immature herring 4-5 years of age, and for 1- and 

 2-year-old small herring. Figure 13 illustrates the respective developments of these three types 

 of fisheries . 



Adult herring during the season of migration to the spawning grounds play the most impor- 

 tant part in the Norwegian fishing industry. Having at our disposal the data on catches, age compo- 

 sition (76), and mean weight of adult herring, we are now able to reproduce tentative indices of the 

 nimiber of specimens of individual year classes of different years that were caught in the process 

 of fishing the given group. 



The most abundant year classes provided the fishing industry with the following number of 

 adult specimens: 1904 year class - 5.2 billion; 1918 year class - 4.2 billion; 1923 year class - 4y6 

 billion; 1930 year class - 4.6 billion; 1934 year class - 2.7 billion; 1937 year class - 2,7 billion^. 



These most numerous year classes ensured the success of Norwegian winter fishing from 

 1910 until 1942. 



Catches of large herring increased in Norway during that period from 1 to 5 million centners . 

 We naturally assume that the fishing intensity on different year classes was unequal and increased 

 during the more recent years of that period. Comparing the catches of the 1904, 1918, and 1930 year 



_1/ At this time, the 1937 year class was not yet fully exploited by fishing. 



57 



