PACIFIC HERRING 
311 
being less than in the previous years. However, any slight error in the comparison 
introduced by the inclusion of this small amount of gill-net catch, being present only 
since 1924, is an error that will tend to obscure rather than to emphasize any deple- 
tion that may have occurred. Up to 1925 the catch increased at a very slightly lower 
rate than the number of boats, then the catch declined sharply in 1926 and 1927, 
rising only a trifle in 1928. The fact that the catch declined in spite of the exploitation 
of new areas suggests depletion. 
Prince William Sound . — The fishery of Prince William Sound — the largest pro- 
ducing district in central Alaska — deserves special mention. Figure 48 shows that 
the total catch rose to a maximum in 1922 and has since declined. Reference to 
Figure 50, in which the catch, the number of purse-seine boats, and the pickled por- 
tion of the catch are plotted on a logarithmic scale shows that the catch and the 
number of boats increased almost proportionately until 1922, while since that time 
so 
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/9/a /920 /922 /924 /926 /92Q 
Figure 50.— The catch of raw herring and the gear used in Prince William Sound from 1918 to 1928, inclusive, 
plotted on a logarithmic scale to show the comparative rate of change. Broken line, number of purse-seine 
boats. Solid line, total catch in millions of pounds. Dot and dash line, portion of catch used for pickling 
the number of boats shows a slight increase but the catch has declined rapidly. The 
low catch per boat in 1918 is undoubted^ due to the fact that nearly all of the 
Prince William Sound plants were built in that year. 
Of far greater importance, however, than the fall in the total catch, is the decline 
in the amount of the catch used for pickling, since this portion of the catch (composed 
of fish over 9 % to 10 inches in total length) represents the bulk of the mature spawning 
population on which the fishery must depend for its continuance. From 1922 to 1928 
the amount of herring used for pickling has decreased at the average rate of about 45 
per cent per year. Even this does not give an adequate picture of the true significance 
of the fall unless one remembers that the bulk of the herring pickled in 1926 and 1927 
(see figs. 37 and 39) were spawned as early as 1920, and the very small portion of the 
