276 
BULLETIN OF THE BUREAU OF FISHERIES 
ANNUAL VARIATIONS IN WEIGHT OF THE INDIVIDUAL HERRING 
In addition to the availability of the fish, another factor that influences the 
yield of the fishery is the variation in the average weight of the fish caught each 
season, since a smaller number of older fish may yield the same poundage as will a 
larger number of younger ones. If the relative abundance of the age classes were 
to remain constant, this factor would not need to be taken into consideration, because 
as each annual age increment would have approximately the same numerical strength 
a uniform distribution of age and size classes would be maintained from year to 
year from which the fishery would draw its supply. If such were the case, the 
average weight of the fish taken would approach a norm. However, the presence 
of dominant year classes causes the average size and weight to fluctuate to a marked 
degree, as shown by Table 9. 
This table shows clearly the effect produced by the growth of dominant year 
classes. Thus in 1928, when the 1926 year class first entered the catch, the number 
of fish taken exceeded the average, but owing to their small size the catch was 
below normal. In 1930, after two years of growth, the size of the catch exceeded 
its mean more than did the number of fish. 
It is thus plain that the increase in weight of the individual fish, especially 
during the earlier part of their existence, aids in minimizing the effects of fishing 
and of natural mortality. 
Table 9. — Showing the annual changes in the average weight of individual herring from 1924 to 1930, 
inclusive, and comparing the total catch with the number of fish 
Average 1 
Total catch 3 
Number of fish caught 
Year 
weight 
of fish 
(grams) 
Actual 
(pounds) 
As per 
cent of 
average 
Actual 
As per 
cent of 
average 
1924 
86.86 
17. 130. 000 
23, 260, 000 
9. 239. 000 
7. 406. 000 
15. 076. 000 
13. 673. 000 
31. 288. 000 
102.4 
89. 454.000 
98. 621. 000 
28, 502, 000 
25. 837. 000 
74. 104. 000 
54. 797. 000 
111, 774,000 
129. 6 
1925 _ 
106.98 
138.5 
142.9 
41. 3 
1926 
147. 03 
55. 2 
1927 
130. 02 
44. 3 
37.4 
1928 
92.28 
90. 1 
107.4 
1929 - 
113. 18 
81.8 
79.4 
1989 
126.97 
187. 1 
162.0 
A verapfi 
109. 92 
16, 725, 000 
100.0 
69, 013, 000 
100.0 
> Computed by weighting the per cent of fish at each length (smoothed twice by 3’s) by the weight at that length from the 
formula W =— (Rounsefell, 1930). 
> Includes the Evans Island, southern Knight Island, and Montague Island areas. 
SIZE AND AGE COMPOSITION OF THE CATCH 
The presence of dominant year classes has been the largest factor in causing the 
fluctuations in abundance which have taken place. (Rounsefell, 1930.) Since this 
last report additional data, covering 1928, 1929, and 1930 have been secured. These 
body length measurements were taken from samples caught in the vicinity of Latouche 
(including the Evans Island area, Montague Island, and southern Knight Island) 
during June and July, and are fairly representative of the entire Prince William Sound 
district since 90 per cent of the total catch is taken in the area included, and 50 per 
cent of the total seasonal catch is taken during these months. Lacking definite evi- 
dence of racial differences these data may be used to represent the fishery of the 
entire district, with the possible exception of the Main Bay area, in which the age 
