44 U. S. BUREAU OF FISHERIES 
The basic problem remaining for solution is this: What is the 
optimum level of catch below which the stock would go to waste 
through underutilization, above which it would become reduced to 
commercial unimportance through overexploitation? Before this 
level can be determined, three questions must be solved: (1) How 
much is the stock reduced by the fishing? (2) How has the relation 
in the stock of income to outgo changed during the growth of the 
fishery? (83) How much does fishing in specific areas affect the stock 
in other areas? 
Answering these questions necessitates the determination of abun- 
dance, age, reproductive success, and of the importance of intermi- 
eration. These necessities determined the program of the South 
Pacific Investigations during 1938. 
STUDIES OF ABUNDANCE 
Since the conventional method of estimating abundance from the 
performance of fishing fleets is limited to the range of fishing opera- 
tions, attempts were made to measure directly the size of the pil- 
chard population by aerial observations. This work, done in planes 
of the United States Navy and Coast Guard from January to May, 
covered an aggregate of 13,000 miles of flying distance, extending 
from Cape San Quentin on the south to Santa Barbara on the north, 
and several hundred miles to sea, and covering the more important 
schooling grounds of the pilehard a number of times. Although 
schools were sighted frequently and identified as pilchards, it was 
found to be unfeasible to estimate their size because their limits 
could not be defined. Also, judging from the time and places of 
occurrence, it was concluded that they did not appear near the sur- 
face by day in proportion to their abundance. Night observations 
were even less satisfactory, and the aerial method had to be 
abandoned. 
Consequently, a measurement of changes in relative abundance by 
an analysis of the commercial catch, begun in 1937, took on added im- 
portance. The catches of boats delivering pilchards to the floating 
reduction plants, operating off San Francisco since 1931, were made 
available for this purpose by the plant owners; and the shore land- 
ings of the fleet considered were furnished by the California State 
Fisheries Laboratory. 
Obviously, the boat catches alone are not directly indicative of the 
availability or abundance of the fish, for the activities and success of 
fishing boats are modified by the weather, the number of hours of 
darkness, since pilchard fishing is carried on in California only in 
the dark, and by other less tangible influences. Consequently, it was 
necessary to treat the data statistically so as to account, as far as 
possible, for the effects of these influences. Transcription of the rec- 
ords was completed and the analysis was under way during 1938. It 
is anticipated that a report on this subject will be completed in 1939, 
The findings in relation to comparable work being carried on for the 
ports of Monterey and San Pedro by the California State Fisheries 
Laboratory, and for Oregon and Washington by the Fish Commis- 
sion of Oregon, should answer question 1. 
