618 



Fishery Bulletin 89(4), 1991 



often perform well on adult fish, they are sometimes 

 unable to depict the complex growth processes char- 

 acterizing the complete life history. In such cases, 

 segmented models should be considered because they 

 allow for life history changes and growth stanzas 

 (Ricker 1979). For example, Watanabe et al. (1988) 

 found that for Pacific saury Cololabis saira, two Gom- 

 pertz curves produced a better fit to the relationship 

 of length and the number of daily otolith increments 

 than did a single Gompertz curve. Zweifel and Lasker 

 (1976) showed that a two-stage Gompertz curve 

 described the growth of anchovy Engraulis mordax 

 larvae better than a simple single-stage Gompertz 

 curve. These authors also noted that although other 

 models had high coefficients of determination, they 

 exhibited unacceptable predictions for small larvae. 

 Likewise, Nishimura and Yamada (1988) found that 

 three linear segments described the relationship be- 

 tween otolith length and total length for walleye pollock 

 Theragra chalcogramma, and that the intersection 

 points between segments represented changes from 

 larval to juvenile growth and juvenile to adult growth. 



Changes in growth stages or stanzas are character- 

 ized by a fundamental alteration or discontinuity in 

 development, such as hatching, first feeding, matura- 

 tion, or a change in habitat (Ricker 1979). Above we 

 presented and reviewed some evidence for this idea 

 from studies of fish. The concept is likely to have 

 validity for many organisms. For example, allometric 

 relationships for physiological rates in Daphnia are 

 stage-dependent (McCauley et al. 1990). 



Some authors (Reznick et al. 1989, Secor and Dean 

 1989) have shown that otolith growth rate is relative- 

 ly insensitive to factors that cause more extensive 

 variation in somatic growth rate (e.g., alterations in 

 temperature and food ration). Under extreme condi- 

 tions, however, daily increment deposition arrests or 

 is otherwise seriously perturbed (Tanaka et al. 1981, 

 Campana 1983, Neilson and Geen 1985; reviews in 

 Campana and Neilson 1985 and Jones 1986). Nonethe- 

 less, in many instances the otolith can be considered 

 a conservative growth structure that is buffered from 

 environmental factors affecting somatic growth. The 

 otolith continues to record significant events, such as 

 transitions to other life stages, even when somatic 

 growth is seriously impaired. Conversely, this buffer- 

 ing tends to obscure the otolithic record of somatic 

 growth fluctuations arising from exogenous factors, 

 e.g., temperature fluctuation, changes in prey density, 

 and turbidity. 



Insulation of the otolith to ambient conditions can 

 lead to a somatic:otolith size ratio that is positively 

 related to growth rate. Recently, Campana (1990) 

 showed that this can lead to biased estimates of length- 

 at-age and the appearance of Rosa Lee's phenomenon, 



when lengths are back-calculated by the Fraser-Lee 

 method. He noted that this problem is unlikely to be 

 significant when the intercept is well fixed by aging 

 young larval fish, or through use of independent bio- 

 logical measurements. In our study, many of the aged 

 fish were young larvae. In addition, the estimated 

 length of a fish with an otolith radius equal to the mean 

 radius at the extrusion check was in good agreement 

 with the mean length of late-stage gestating pre- 

 extrusion larvae. Lastly, we found no evidence that 

 back-calculated lengths of fish captured as juveniles 

 differed from directly measured lengths of fish cap- 

 tured as larvae. 



Acknowledgments 



The crew of RV David Starr Jordan and RV Ed Rick- 

 etts and the scientific personnel onboard assisted in the 

 collection of fish. Greg Cailliet provided access to the 

 RV Ed Ricketts, and Diana Watters helped organize 

 these cruises. Don Pearson wrote the computer pro- 

 gram used to record age data from the digitizer. Steve 

 Campana provided us with a prepublication copy of 

 his 1990 paper. Izadore Barrett, Joseph Hightower, 

 William Lenarz, Alec MacCall, Anne McBride, Carol 

 Reilly, and three anonymous reviewers made helpful 

 comments on this manuscript. 



Citations 



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