PROGRESS IN BIOLOGICAL INQUIRIES, 1938 45 
AGE AND GROWTH 
The second question can be answered by determining the ages of the 
fish making up the population each year, thus learning the relative 
abundance of the individual broods of previous years (income) and 
how fast they are removed by fishing and by natural mortality 
(outgo). To begin with, the relationship between age and size must 
be established. Once that is done, the findings can be applied to past 
records to detect any changes in the balance between income and 
outgo. 
Age determination is being attempted by interpreting marks in 
hard structures, by observing the growth of young pilchards, and by 
identifying modes in frequency distributions of the adult population. 
During 1988, a series of frequency curves of young fish measured in 
southern California was collected, from which the growth rates of 
the first two or three age classes may be traced. A sample of young 
was also collected for comparative purposes at Magdalena Bay, Lower 
California, and others from Coos Bay, Oreg., and from various points 
in Washington. 
Scales and otoliths were collected through the year from the young 
fish samples. Most of these, numbering over 10,000, have already been 
mounted by a W. P. A. project, and they are now being studied to 
learn the time of appearance of a year-mark and the extent to which 
pilchard scales can be used for age determination. During 1938, 
sampling of young fish was carried on at San Pedro, Newport Beach, 
and San Diego. This work will be continued in 1939 so as to com- 
plete at least one year’s cycle of growth. 
For studies on various phases of the biology of the commercial- 
sized fish, the South Pacific staff sampled the catch at Grays Harbor 
during the summer at Washington, and during the subsequent fall 
and winter at San Francisco. In addition to age and growth studies 
by analysis of the frequency curves, these data will be examined to 
determine the extent to which the populations of the two regions can 
be identified with each other. The work will be much facilitated by - 
comparable samples from Oregon, taken by the Oregon Fish Com- 
mission. 
A history of the size composition of the pilchard population in 
California, going back almost to the beginning of the fishery, has 
been kept by the California State Fisheries Laboratory, whose staff 
has sampled the catch systematically since 1919. Thus is recorded 
the rise, growth, and decline of the various dominant year classes that 
have appeared since then. This vast amount of data is being made 
available to the South Pacific Investigations for use in connection 
with current studies. During the year part of these records have been 
transcribed to a punch-card sort system. Through the aid of a 
W. P. A. project, it is expected that the remainder of the transcrip- 
tion will be completed during 1939. The records will be treated 
statistically in an effort to recognize homologous component age 
groups, to measure the rate of their removal, and hence to compare 
the effect of the lower fishing intensities of former years with higher 
current intensities. 
