NOTE Piner et al : Use of oxygen stable isotopes and the 1983 El Nino to assess accuracy of aging Sebastes melanops 557 



0.6 

 0.4 

 0.2 

 0.0 

 -0.2 

 -0.4 

 -0.6 



-0.8 



1978 1980 1982 1984 1986 1988 1990 1992 



a 



| 0.6 • 



< 



0.4 



0.2 

 0.0 

 -0.2  

 -0.4 • 

 -0.6 



-0.8 



1978 1980 1982 1984 1986 1988 1990 1992 

 Year 



Figure 3 



The year-specific average model residual from (A) all 

 nine black rockfish (Sebastes melanops) and (B) ages 

 6-8 (•, solid line) and ages 11-12 (D, dashed line) fish. 

 Error bars are ±1 SE. 



various ages and from various collection dates and by 

 performing the same analysis on each fish. Lastly, this 

 method of age validation can be difficult to implement 

 for fish with small otoliths or for long-lived fish be- 

 cause of the difficulties in obtaining sufficient otolith 

 material from small growth increments. 



The detection of El Nino events using o a8 may allow 

 the use of this reoccurring climatic event as a natural 

 tag for age validation. Because previous studies that 

 used El Nino events as time markers were forced to 

 measure biological reactions to environmental chang- 

 es, the use of d m O may be an improvement because it 

 avoids assuming the intermediate step, namely that 

 environment affects a biological process. The results 

 from this study, however, were based on a small sample 

 size and are, therefore, only preliminary. Further work 

 in this area is warranted. 



Acknowledgments 



We are grateful to Maria Marcano of the University of 

 Michigan geochemical laboratory for her help in setting 



up the assays. Bill Miller of the Oregon Department of 

 Fish and Wildlife provided aging expertise.We thank 

 the Sea Grant Fellowship in Population Dynamics and 

 the National Marine Fisheries Service Northwest Fish- 

 eries Science Center for financial support. Finally, the 

 anonymous reviewers and Christian Reiss greatly helped 

 our efforts. 



Literature cited 



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 Beamish, R. J., and G. A. McFarlane. 



1983. The forgotten requirement for age validation in 

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 Campana, S. E. 



1997. Use of radiocarbon from nuclear fallout as a dated 



