SIZE COMPOSITION 



The sizes of sardine larvae taken on monthly 

 survey cruises, 1951-59, are summarized in 

 tables 10-18, and of anchovy larvae in tables 

 38-46. Numbers of larvae of both species 

 decreased markedly with increase in size. 

 These tables are included to make size data 

 available and to demonstrate that about the 

 same proportions of larvae of different sizes 

 are taken each year. To emphasize further 

 the latter point, I have grouped the anchovy 



larvae into somewhat coarser size groupings, 

 usually 3 mm., in table 7. This two-part 

 table summarizes numbers of larvae by size 

 group in the upper part and by percentages 

 m the lower. In only 1 year, 1956, were per- 

 centages of small larvae conspicuously low 

 and percentages of other size groupings of 

 larvae correspondingly high. The consistency 

 of representation of different sizes of larvae 

 year after year is evidence that total numbers 

 per se are meaningful values for comparing 

 abundance of larvae. 



Table 7. --Numbers of anchovy larvae of grouped sizes taken on CalCOFI surveys, 1951-59, and percentage contribution of each 



size group to annual total 



INCREASE IN ABUNDANCE OF ANCHOVY 

 LARVAE SINCE 1951 



On the basis of increase in abundance of 

 larvae, the anchovy population has increased 

 markedly since 1951. To make the quarterly 

 survey coverages obtained since 1961 equiv- 

 alent with the more frequent coverages (mostly 

 monthly) obtained during 1951-60, the follow- 

 ing procedure has been adopted. For the decade 

 1951-60, average quarterly values derived for 

 each year were based on data from the three 

 or fewer comprehensive survey cruises made 

 during the quarter; each yearly total repre- 

 sents the summation of "average" quarterly 

 values (table 8). The data given for 1961-64 

 represent the quarterly survey totals, summed 

 to obtain the yearly estimates. 



The population increased rapidly between 

 1951 and 1954, reached a plateau that continued 

 through 1957, increased rapidly again through 

 1962, and since then appears to have maintained 

 a high level. A conservative method of esti- 

 mating the increase in population size is to 

 use the average of the annual estimates for 

 3 years at the beginning of the period of 

 increase (1951-53), and of the most recent 

 years (1962-64). The average number of an- 

 chovy larvae was 21,875 in 1951-53. In com- 

 parable coverage during 1962-64, the 

 average number was 195,000. Thus, ap- 

 proximately nine times as many anchovy 

 larvae were taken per year during the 

 recent period as during the early 1950's. 

 The increase in abundance is illustrated in 

 figure 6. 



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