138 
BULLETIN OF THE BUREAU OF FISHERIES 
ANALYSIS OF YEAR CLASSES 
Differences in the relative proportions of different year classes present in the 
populations may be of value as an indication of the extent of intermingling. The 
relative abundance of any particular year class in the catch is influenced chiefly by 
three factors: First, the relative number of larvae of that year class hatching and sur- 
viving through the juvenile period until of an age or size to enter the catch; second, 
by the rate of natural mortality; and third, by the increased rate of mortality induced 
by the fishery. However, the relative abundance of any particular year class in the 
catch may change during the season. Such a progressive change from younger to 
older age groups is apparent as the season advances, for instance, in Prince William 
Sound. Owing to such fluctuations in the relative proportions of each age group 
present at any particular time, only the major differences between localities can be 
emphasized without further data. 
In figure 10 are given histograms of the percentage age distributions for the major 
fishing grounds during the 1929 and 1930 seasons. Several features are worthy of em- 
phasis. These are (1) the approximate equality of the 1926 and 1927 year classes at 
Noyes Island as contrasted with the overwhelming dominance of the 1926 year class 
at most of the other localities, (2) the great dominance of the 1927 year class at Todd, 
(3) the dominance of the 1923 year class at Douglas Island and Favorite Bay, (4) the 
large percentage of the catch older than the 1923 year class at Douglas Island. 
These salient facts all support the indications given by the analyses of the vertebral 
counts and of the growth rates which separate the Noyes Island area, Todd, and the 
Juneau-Icy Strait area (including Douglas Island) as independent of neighboring 
areas. Whether Favorite Bay is independent of Point Gardner we hesitate to say 
without further data. 
TAGGING 
Curtailment of fishing operations during 1932 and 1933, due to economic condi- 
tions, and an increased abundance in the Cape Ommaney tribe of herring, owing to the 
accession to the catch of certain dominant year classes, caused fishing during 1932 to 
be carried on almost wholly in the area between Noyes Island and the lower end of 
Baranof Island. During 1933 the boats did not fish farther south than Warren 
Island. Tins condition, which was in contrast to the widespread fishing conducted 
for several years previously, made our tagging work of less value than it would have 
been under normal conditions, as obviously the presence of tagged herring cannot 
be detected where no fishing operations are being conducted. However the results 
are presented for what they are worth. For a full discussion of tagging methods and 
manner of recovery of the tags, see Rounsefell and Dahlgren (1933). 
During the fishing season of 1933 (June 1 to September 30) 101 belly tags and 7 
opercle tags were recovered from 2,499 of the former and 1,470 of the latter affixed 
to herring released at Jamestown Bay (Sitka) between April 21 and April 25, 1933. 
All of these tags were recovered around Cape Ommaney, between Larch Bay and 
Port Alexander, giving the first definite proof of a migration of some length, as it is 
approximately 66 miles by water from Jamestown Bay to Port Alexander. 
On the other hand, out of 996 belly tags and 824 opercle tags affixed to herring 
released at Cape Bendel, just under 60 miles from Port Alexander, on August 17, 
1932, not a tag has been recovered. This may be considered rather definite evidence 
of a lack of migration between Cape Bendel and Cape Ommaney. 
