- 32 - 



tions in dealing with the material under consideration, since, as will be seen from 

 Table V, seine catches taken at the same place and time exhibit similar differences. 



Table V. Seine samples from approximately same place 

 and time, (1904 year-class). 



Locality and date. 

 Length, cm. d 



— — 9.... 



Closer investigation as to the extent of selection exercised by the net 

 would have to be made by laying out nets within the area enclosed by a seine, 

 and comparing the net samples thus obtained with those taken by the seine 

 itself. Such a comparison ought also to be made; in the first place because it 

 would furnish us with definite data on which to work, and in addition, would 

 be of interest in considering the large herring material, which consists exclusively 

 of netted fish. We may, however, from the foregoing presume, that the selection 

 effected by the nets is inconsiderable, and cannot be responsible for the variation 

 indicated. 



Biological conditions. 



It remains then, to ascertain how far the variation may possibly be ac- 

 counted for by certain features in the biology of the herring. And having in 

 mind the character of the fishery, an examination of the variation in the samples 

 according to place and time of capture immediately suggests itself. In order to 

 obtain such subjects for comparison as lie not too far apart in a table of corre- 

 lations, the time has been divided into three main periods of about one month, 

 the localities being grouped in four large areas from north to south. In addition, 

 the material has been arranged in three large age-groups, 1) under 7 years, 

 2) between 7 and 10, and 3) over 10 years old. These three groups are indicated 

 in Table VI as I, II and III respectively, the corresponding figures showing the 

 percentage of individuals examined falling to each group. The numbers of the 

 samples are stated in separate columns. 



Table VI. Percentage of the three age groups; the samples arranged 

 according to time and place. 



Locality 



No. of 



Dec. and Jan. 

 I II III 



No. of 

 samples 



February 



I 



II 



III 



No. of 



March 



II 



III 



N Sulen (Nordre) a 



I Âlesund, Kalvâgb'.. 



j Feie-Karmsund c 



S Egersund Chr'sand d 



»/o 



6.6 

 6.7 



"/o 



86.4 

 69.7 



"/o 



7.2 

 24.2 



"/o 



% 



»/o 



3.4 81.9 16.6 



6.1 85.2 8,8 



28.1 166.8 '. 5.6 



«/o 



4.4 

 16.2 

 16.1 



84.3 

 76.0 

 80.6 



»/o 



11.6 

 7.9 

 3.4 



