798 



Fishery Bulletin 100(4) 



cohort occurring after one year is a realistic representation 

 of what occurs in the early life history of striped bass. Al- 

 though the number of fish that a cell represented could be 

 less than one, this number was used as a relative weight- 

 ing to all other cells; thus, proportionally, the value was 

 valid. Consequently, the actual starting number of fish of 

 the cohort was irrelevant for this study but could be used to 

 calibrate the model to a particular population of interest. 



I was able to simulate a number of dissimilarly shaped 

 OR-TL relationships by modifying the parameter used to 

 convert brain weight to otolith weight from a constant to a 

 function. However, trial runs showed that when this param- 

 eter was held constant, the resulting OR-TL relation was 

 not linear I later determined that because both soma and 

 otolith growth were modeled as functions of weight and be- 

 cause the exponent of the weight-length equation (0.31) did 

 not exactly equal the exponent of the equation that calcu- 

 lates the radius of a sphere (0.333), two rates must at some 

 point diverge from linearity. For the purposes of this study, 

 it was not necessary that the equations precisely depict the 

 actual bioenergetics processes, only that true length of fish 

 at annulus formation be known with certainty 



This study yields several conclusions important to studies 

 of growth estimates from otolith back-calculations. The best 

 back-calculation technique was directly related to how well 

 the OR-TL model fitted. The percent error of any given meth- 

 od was rarely consistent across ages, although estimates of 

 older ages were more accurate than those of younger ones. 

 Younger ages were generally best estimated by using direct 

 proportionality on the last annulus only Thus, it may be 

 necessary to use multiple methods to accurately estimate a 

 growth curve. However, it would be difficult to select which 

 combination of methods would be most accurate without 

 prior knowledge of the tioie length-at-age. 



Acknowledgments 



I would like to acknowledge the following people for their 

 contributions to this work: J. A. Bohsack, C. P. Goodyear, P. 

 Johnson, S. Quackenbush, and J. C. Trexler And I would 

 like to thank the manuscript reviewers for their editorial 

 comments. 



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