Although the first two year-marks are generally well defined on 

 otoliths, the third is less so; and the subsequent ones are so closely 

 crowded and so easily confused with false year marks that they cannot 

 be counted with a very high degree of confidence. 



To determine whether or not the "annulus" is formed once annually 

 in otoliths, a stratified random sample of 2600 specimens, representing' 

 about equally all the months of a year, was examined, and the marginal 

 increments, -vrfiich included the band comprising the annnlus, were measured 

 as described on page 8. To avoid possible confusion between true and false 

 year marks in otoliths, no translucent zone was considered until it was 

 wide enough to preclude its being a false annulus. 



TJie marginal increments for otholiths, when plotted in the same way 

 as had been done for scales in figure 4, proved also to be narrowest during 

 one part of the year, and to increase progressively thereafter. In figure 

 7, age classes 1937, 1936, and 1938 have been assigned to fish having, 

 at their first appearance in our samples, one, two, and zero rings on 

 their otoliths, respectively. It is evident, in figure 7, that the annulus 

 is a true year mark in otoliths as well as in scales, and became visible- 

 earlier in otoliths than-in scales in 1939, showing as early as June in 

 some specimens, and by October in all. This is consistent with the con- 

 clusion reached above that in scales the year mark forms during the summer 

 and fall. 



To define more exactly a time when the annulus became evident in 

 otoliths, we can choose, from the data used for figure 7, arbitrary boun- 

 daries to separate "narrow" from "wide" marginal increments, as was done 

 for scales. Thus the 35-mm. point was selected for year class 1938, the 

 20-mm. point for year class 1937, and the 15-mm» point for year class 1936. 

 The proportion of fish having "narrow" marginal increments, in percentage, 

 by months, is given in figure 8, 



Parallel age determinations, by scales and by otoliths, were made 

 in 1036 specimens. The results, given in table V. indicate a high agree- 

 ment for the first two year classes, and a moderate agreement for the thirdi 

 Doubtless a large portion of the disagreements among the three-year-olds 

 may be attributed to the difficulty of counting the rings on otoliths 

 ■with more than two marks. 



Growth of Juvenile Piloharde 



The age composition of samples from the 1938-39 bait fisheries of 

 southern and central California, as determined by scales, is indicated 

 in figure 9 where the growth of fish comprising year classes 1938 and 



46 



