384 
Fishery Bulletin 106(4) 
lucent zone (Fig. 2). In specimens from category 1, 
the translucent zones were usually compact and well 
defined; hence any apparent splits could easily be in- 
terpreted and decisions could be made as to how they 
should be enumerated. In category-2 specimens, the 
potential annual zones were not well defined, often due 
to splits that created interpretative options. Splits in a 
potential annual zone that occur before the transition 
to slow growth are especially problematic. In hindsight, 
it was reasonable to conclude that the two specimens 
(numbers 146 and 317) that diverged from the loess- 
smoothed category-1 data were over-aged probably be- 
cause of broad splits. The specimen with the largest 
discrepancy, number 146, was one where the pattern in 
the broken-and-burnt cross section could be aged at 16 
years (more in line with the loess-smoothed category-1 
data), or on a second reading axis could be interpreted 
as 26 years. Similarly, in Figure 2 an age of 32 years 
was estimated along an axis closer to the sulcus, but 
a more correct age estimate of 20 years was chosen 
from an adjacent reading axis. Some of this discrep- 
ancy could be the result of splitting translucent zones. 
In reality, the five specimens in category 2 are not 
enough to draw firm conclusions on how these difficult 
otoliths should be aged. A further study of category-2 
type specimens may help to refine the aging criteria 
for Dover sole otoliths. 
The region in the otolith cross section before the tran- 
sition to slow growth can be an area of splitting or dif- 
fuse translucent zones. This is a situation that can lead 
to over-aging; therefore the reader must exercise care 
to count only prominent translucent zones. Splitting 
and diffuse translucent zones are a frequent problem 
in age reading many species (e.g., Francis and Horn, 
1997; Gregg et ah, 2006; Hutchinson et al., 2007). The 
fish in category 1 were correctly aged by counting only 
the prominent translucent zones preceding the transi- 
tion to slow growth. 
Conclusions 
The ages estimated for the GOA Dover sole were vali- 
dated as accurate based on the easy-to-age otoliths in 
category 1. When the age bias of -1 or -2 years was 
applied, the A 14 C in the validation samples had the same 
timing as the z\ 14 C in the Pacific halibut reference chro- 
nology and was consistent with the expected 1-year core- 
size shift. An age-structured stock assessment model 
is used for management of the GOA Dover sole com- 
mercial fisheries and hence the age data validated here 
are important for population modeling and setting the 
total allowable catch (Stockhausen et ah, 2005). In the 
future, analysis of additional difficult-to-age category-2 
otoliths may help to further answer questions regard- 
ing aging criteria for these specimens. In reality, the 
lower-than-average between-reader precision for growth 
zone counts will likely persist, but now we have a high 
degree of confidence in the accuracy of ages estimated 
from specimens with clear growth zones. 
Acknowledgments 
We thank the staff at the Age and Growth Program of 
the Alaska Fisheries Science Center for support during 
this study. We also wish to thank T. Wilderbuer and W. 
Stockhausen of the Alaska Fisheries Science Center for 
helpful reviews and comments on early versions of this 
manuscript. K. Mckinney provided photographic sup- 
port for which we are grateful. We thank A. Andrews of 
Moss Landing Marine Laboratories and two anonymous 
reviewers for insightful comments on the manuscript. S. 
Handwork and K. Elder of the National Ocean Sciences 
Accelerator Mass Spectrometry Facility at the Woods 
Hole Oceanographic Institution provided support and 
technical advice regarding the A 14 C measurements for 
which we are grateful. 
Literature cited 
Abookire, A. A., and K. M. Bailey. 
2007. The distribution of life cycle stages of two deep- 
water pleuronectids, Dover sole ( Microstomus pacificus) 
and rex sole ( Glyptocephalus zachirus), at the northern 
extent of their range in the Gulf of Alaska. J. Sea 
Res. 57:198-208. 
Abookire, A. A., and B. J. Macewicz. 
2003. Latitudinal variation in reproductive biology and 
growth of female Dover sole ( Microstomus pacificus) in 
the North Pacific, with emphasis on the Gulf of Alaska 
stock. J. Sea Res. 50:187-197. 
Abookire, A. A., J. F. Piatt, and B. L. Norcross. 
2001. Juvenile groundfish habitat in Kachemak Bay, 
Alaska, during late summer. Alaska Fish. Res. Bull. 
8(1 ):45 — 56. 
Andrews, A. H., E. J. Burton, L. A. Kerr, G. M. Cailliet, K. H. 
Coale, C. C. Lundstrom, and T. A. Brown. 
2005. Bomb radiocarbon and lead-radium disequilibria 
in otoliths of bocaccio rockfish ( Sebastes paucispinis ): a 
determination of age and longevity for a difficult-to-age 
fish. Mar. Freshw. Res. 56:517-528. 
Andrews, A. H., L. A. Kerr, G. M. Cailliet, T. A. Brown, C. C. 
Lundstrom, and R. D. Stanley. 
2007. Age validation of canary rockfish (Sebastes pin- 
niger) using two independent otolith techniques: lead- 
radium and bomb radiocarbon dating. Mar. Freshw. 
Res. 58:531-541. 
Beamish, R. J., and G. A. McFarlane. 
1983. The forgotten requirement for age validation in fish- 
eries biology. Trans. Am. Fish. Soc. 112(6):735 — 743. 
Campana, S. E. 
1997. Use of radiocarbon from nuclear fallout as a dated 
marker in the otoliths of haddock Melanograrnmus 
aeglefinus. Mar. Ecol. Prog. Ser. 150:49-56. 
2001 . Accuracy, precision and quality control in age deter- 
mination, including a review of the use and abuse of age 
validation methods. J. Fish Biol. 59:197-242. 
Campana, S. E., and C. M. Jones. 
1998. Radiocarbon from nuclear testing applied to age 
validation of black drum, Pogonias cromis. Fish. Bull. 
96(2):185-192. 
Campana, S. E., L. J. Natanson, and S. Myklevoll. 
2002. Bomb dating and age determination of large pelagic 
sharks. Can. J. Fish. Aquat. Sci. 59:450-455. 
