1937 can be traced from early youth to the size at entrance into the 

 fall commercial fishery for adults; and though data for year class 

 1936, also included, are rather scanty, they are sufficient to give 

 some indication of size composition and growth. A similar figure made 

 from otolith readings was essentially identical with figure 9, and 

 is therefore not here reproduced (Table 6 ). 



TABLE v.- Comparison of Age Readings by Scales and by Otoliths 



Number of Number of otolith Number of otolith Percen- 

 annuli by readings matching readings not match- tage agree- 

 scale reading scale readings ing scale readings nent 



1 355 6 98 



2 UI9 36 92 



3 166 5U 75 



9hO 96 



Precise knowledge of the growth of the pilchard is seriously 

 impeded by the difficulties of sampling, discussed on page U , Growth 

 is illustrated in figure 10 (Table 8 ) where the average lengths of 

 each year class among fish taken in California are plotted by months. 

 Data are from the bait fisheries and from the fall commercial fishery 

 for adults. 



The differences from year to year bet'reen the average length 

 of fish of corresponding ages in figure 10 are no doubt due in part 

 to actual differences betvreen the year classes. In large part also, 

 however, they are due to differential selection. I.ioreover, valuations 

 from a smooth growth curve for individual year classes are probably 

 due to varying selection. 



Samples of fish of year class 1937, taken from April, 1938, to 

 May, 1939, were mostly from the southern California bait fisheries, 

 where there is a tendency for bait fishe"rmen to select against the larger 

 fish, resulting in over-representation of the smaller members of that 

 year class. Furthermore, judging from figure 9, there was a tendency 

 for the larger fish of year class 1937 to leave, and for smaller ones 

 to enter, the field of' the fishery at intervals during the year. The 

 consequent selective availability undoubtedly contributes to the irregu- 

 larities of figure 10. From June to October, j'-ear class 1937, as well 

 as 1936, was sampled from the San Francisco bait fisheries, which seemed 

 to select against the smaller fish, producing an effect opposite to 

 that obtained in southern California. At the same time, beginning in 

 September, samples were taken from the fall fishery for adults at Monterey. 

 Here a selection results from a rather conplex differential availability. 

 Fish of year class 1938 taken in the fall coniuercial fisher;/- for adults 

 appear to represent the larger membersof their class, perhaps partly 



47 



