because the latter were schooling with older fish, and partly because 

 the fishermen consciously selected against very small fish, which have 

 low economic value for reduction or canning purposes. In general the 

 fish available during most of the fall are sjnaller and yoimger than 

 those available during the winter. This results in a selection, by 

 differential availability, against the larger fish of year classes 1937, 

 1936, and 1935. 



Because of these differences in demand and availability from place 

 to place, from fishery to fishery, and from month to month, and the 

 consequent imperfections in our sampling of the population, figure 10 

 shows a very irregular series of .points to which such a curve as might 

 be fitted could only rather roughly represent the average growth of the 

 pilchard in California during its first four years. Nevertheless, in 

 all essential respects, the points, as far as they go, are in harmony 

 with the points (designated by large asterisks) obtained from the modes 

 of frequency curves in figure 2, and from data published by the CaLLifornia 

 State Fisheries Laboratory (Clark, table 2, I936). 



Difference in Size Betv/een Localities 



The foregoing discussion has referred only to fish collected in 

 California. The statistics given in figure 10 and table 8, therefore, 

 describe only a portion of the total Pacific coast population of those 

 year classes. That this is true is shown by figure 11, which gives the 

 age composition of such samples as were obtainable in Washington, Oregon, 

 and Lower California. Obviously, if it were possible to sample properly 

 the entire coast, the range of each year class would probably be broader 

 than shown in figure 9. Though the data from northern and southern 

 grounds are too scanty to deserve very extensive interpretation, they 

 show that fish found north of California in 193Q-39 averaged smaller 

 by the end of their first year than those of the same age from Californiaj 

 and fish taken from Lovrer California averaged larger than those of the 

 same age taken in California. These differences are no doubt reflected 

 in the scale grov/th increments, and should furnish a tiseful tool for 

 studying migrations. 



DISCUSSION AND CONCLUSIONS 



The scales and otoliths of most fishes are characterized by folds 

 or sculpturing in which variations of pattern may be related to age. 

 If they are so related, for a given species, they need not correspond 

 in number vrlth years of life; or, if they do correspond, they may not 

 be recognized, for they may be so obscure as to be counted incorrectly. 

 It is no wonder, then, that scale and otolith reading is a process 

 peculiarly open to subjective influences, and requires, for serious work, 

 a stringent test and proof of validity. 



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