420 ye ee AEN 
1904. In 1910 the VI year-class, with 77-3 per cent., completely domin- 
ates the others ; still the fish born in 1904. In 1911 the VII year-class, 
in 1912 the VIIT year-class, and in 1913 the IX year-class still form from 
64 to 70 per cent. of the whole population, the fish in each case being 
those born in 1904. In 1914 these fish still form 54:3 per cent. of the 
whole. Thus it will be seen that for six or seven years this one year-class 
of 1904 dominates the fishery. If we look at the figures still more closely 
we shall see further evidence that a particular year-class may be of 
special importance over a series of years. In 1910 the fish of year-class 
V formed 9-9 per cent. of the sample, being the second largest of the 
year-classes present. These fish were born in 1905. In 1911 these 1905 
1896 $9 
Fro, 9.—Yield of the Norwegian spring herring fisheries for the years 1896-1913. 
15=1,500,000 hectolitres. 1 hectolitre=22 gallons. (After Hjort.) 
Hoot 2°3°4 5.6 7 8-9 @ Ww 12% 
born fish belong to the VI class, and again they are second in importance 
with 17-3 per cent. The class occupies the same position in 1912 and in 
1915, when the fish are seven and eight years old respectively. Similarly 
the fish born in 1899 form the VIII group in 1907, the IX group in 1908, 
and the X group in 1909, the group in each case being present in con- 
siderably greater numbers than fish of the adjacent groups. 
The herring fishery is one which is subject to very great fluctuations 
from year to year, and to those who have watched the fishery for many 
years it is a well-recognized fact that bad and good years often run in 
