KIMURA and SAKAGAWA: SCALE PATTERNS OF PACIFIC SARDINE 



and older fish. If this was the case, and assuming 

 that growth has not appreciably changed, then 

 the number of fish that was incorrectly aged as 

 age I by recent scale readers was at most equal 

 to the number of fish correctly aged as age I. This 

 is deduced from the fact that the presumably 

 overestimated Li of 131.5 mm is about midway 

 between our Li of 103 mm and L2 ( — length at 

 time of second annulus formation) of about 

 160 mm. 



Back-calculated lengths for Pacific sardines 

 (Marr, 1960) have been based on Method 1. A 

 statistical test of the intercept of our body 

 length-scale radius relation (Figure 2) indicated 

 that the intercept is not significantly different 

 from zero (t = 1.831, df = 282). Although 

 this indicates that Method 1 is acceptable, the 

 back-calculated lengths at first annulus are ap- 

 preciably and significantly different between 

 Method 1 and Method 2 (Table 3). It is there- 

 fore advisable that Method 2 be used since it is 

 the better procedure (Ricker, 1969). 



We conclude from these results that a bias may 

 be present in published accounts of the age comp- 

 osition of the Pacific sardine catch, which in turn 

 may have affected studies on the population dy- 

 namics of the Pacific sardine. We recommend 

 that the method of aging Pacific sardines be re- 

 evaluated, perhaps with the consideration of 

 modifying the scale method so that the scale 

 reader is made aware of the length of fish being 

 aged or even utilizing other hard parts for aging, 

 and that appropriate steps be taken to eliminate 

 aging errors in the historic records on age comp- 

 osition of the catch. We realize that this task 

 will not be easy, but it may be worthwhile be- 

 cause of the frequent use of the records to an- 

 alyze fisheries hypotheses. 



ACKNOWLEDGMENTS 



We thank C. E. Blunt, Jr., J. E. Hardwick, 

 and J. S. MacGregor for participating in our 

 test to determine whether accessory marks can 

 be misidentified as annuli. P. Paloma and A. 

 Saraspe assisted in hatching and rearing the 

 sardines. D. Kramer, W. H. Lenarz, J. S. Mac- 

 Gregor, and A. M. Vrooman kindly reviewed the 



manuscript and gave helpful suggestions. J. R. 

 Thrailkill drew the figures. We are indebted to 

 these individuals. 



LITERATURE CITED 



Ahlstrom, E. H. 



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 Brown, M. E. 



1957. Experimental studies on growth. In M. E. 

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HOGMAN, W. J. 



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KiMURA, M. 



1970. Formation of a false annulus on scales of 

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Landa, a. 



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