ays U. S. BUREAU OF FISHERIES 
surviving to commercial size. Though an approximate knowledge 
of age and growth has been attained through a study of the size 
composition of the commercial catch, a gre eater precision is necessary 
for determining the relative numbers of each year-class surviving 
from year to year; and, also, the relative mortality rates, once the 
fish attain commercial size. Such precision is possible by determin- 
ing the age composition of the commercial catch. Age determina- 
tion is a technic ally difficult task, having been first attempted some 
14 years ago, and, up to the time of this investigation, not yet ac- 
complished. By intensive experiments during the eet 2 years it 
has been found that the age of juvenile pilchards, i. e., those up 
through the third year of life, can be determined by rings formed 
annually on the seales and also on the otoliths. It was found that 
in California, fish of the year among the samples studied in 1938 had 
a modal body (standard) length of about 70 mm. (total length of 
about 3.3 in.) in June, when they first saeaitedl in the bait fishery, 
and grew to about 120 mm. (total length of about 5.6 in.) by the 
following April, by which time the first annual mark had formed. 
At that time the modal length of fish having 2 marks was about 
165 mm. (total length of about 7.7 in. ), and of those having 3 marks, 
around 195 mm. (total length of about 9.1 in.). Though the study 
1as been concerned only with young fish, it has, by ‘defining age 
marks and proving their annual occurrence, made way for a similar 
study of the scales of older fish. Of these, there are 2 groups: Young 
adults usually caught during the fall months, and older adults caught 
in northern waters during the summer and in California waters 
during the winter. During 1939 an extensive collection was made 
of the scales of both groups from Grays Harbor, Wash., and from 
Monterey, Calif. A preliminary examination of the scale samples 
gives promise of success in determining the age of commercial-sized 
fish. 
SAMPLING 
Sampling of the commercial catch was carried on in California at 
San Pedro, Monterey, and San Francisco shore plants by the Cali- 
fornia State Fisheries Laboratory; at floating reduction plants op- 
erating off San Francisco and at Grays Harbor, W ashington, by the 
U.S. Bureau of Fisheries; at Astoria by the Oregon Fish Commis- 
sion; and at British Columbia by the Fisheries Research Board of 
Canada. Preliminary study of these samples, and of those taken 
in California in each of the preceding 20 years by the California 
State Fisheries Laboratory, indicates that the pilchard population 
is by no means distributed at random and that a simple summation 
of samples. however intensively taken, cannot be expected to repre- 
sent fairly the population. Apparently the fishery draws on a suc- 
cession of “runs” in each locality. These runs vary in their duration, 
and differ significantly with reference to the size and the abundance 
of fish composing them. These variations are probably connected 
with peculiarities in hydrographic conditions which change during 
the season, and from season to season. For example, a set of hydro- 
graphic conditions conducive to catching small fish for a relatively 
long period of time in one season, as compared with another set of 
conditions which permit fish of that size to be caught during a short 
