84 
Fishery Bulletin 1 14(1) 
that validation through bomb radiocarbon 
levels has high scientific merit and therefore 
is preferable to most other techniques, and 
only modest sample sizes (20-30 individuals) 
are needed. 
Annual increment formation in the otoliths 
of wreckfish was validated by the radiocarbon 
dating method used in our study for wreckfish 
from the North Atlantic, and by the compari- 
son with the haddock standard. As expected, 
with the exception of one outlier believed to 
have resulted from contamination, we detect- 
ed no measurable radiocarbon in the otolith 
cores that were formed before 1958. One ca- 
veat for the use of a bomb radiocarbon tech- 
nique for age validation is that it allows for 
validation of a maximum age only to the year 
of bomb radiocarbon onset (1958). Because all 
specimens of North Atlantic wreckfish used in 
this study were collected in 1991, we were able 
to validate a maximum age of up to 33 years 
with this technique. Collection and validation 
of age of otoliths in later years should elim- 
inate the need for this caveat in the future. 
Still, the results of this study are useful today. 
The bomb radiocarbon technique validated the 
structure and annual formation of increments, 
indicating increment counts can successfully 
be used to age otoliths from wreckfish. 
A distinct phase shift of approximately 
5-6 years was apparent when comparing the 
chronology of radiocarbon levels in wreckfish 
with the standard chronology of haddock. 
of the 4 methods. We defined age at full recruit- 
ment to the fishery as the age calculated for the 
most common (900 mm FL and 12 years old) 
length in the fishery-dependent samples based 
on our calculated VBGM. This approach result- 
ed in 2.5%, 2.1%, 1%, and 0% recruits surviving 
to maximum age with Equations 4, 5, 6, and 7, 
respectively. 
Discussion 
Age validation, here referring to confirmation 
of absolute age and periodicity of growth incre- 
ment formation, is a crucial step for stock as- 
sessment of any fish species. Without validat- 
ed age data, greater uncertainty in estimates 
of age-related life history parameters (e.g., 
growth and natural mortality) and age compo- 
sitions would persist, resulting in an increase 
in uncertainty in stock assessment models. 
Particularly daunting is the task of validat- 
ing the ages of long-lived fishes because few 
techniques are applicable to these species and 
most attempts have unclear results (Tracey 
and Horn, 1999; Harris et al., 2004). For the 
techniques available, Campana (2001) suggests 
Age estimate (yr) 
Figure 5 
Observed length-at-age data for wreckfish ( Polyprion america- 
nus ) collected in the North Atlantic from 2000 through 2011 
used in the growth analysis. The solid line represents esti- 
mates from the fitted von Bertalanffy growth model. 
90 ^ Age and growth 
Sample population 
80 
70 - 
60 - 
>, 
O 
c 
300 360 420 480 540 600 660 720 780 840 900 960 1020108011401200126013201380 
FL (mm) 
Figure 4 
Length frequency (in 10-mm bins) of fork lengths (FLs) from the 
samples of wreckfish ( Polyprion americanus) collected in the North 
Atlantic in 1991 and used in age and growth analysis (n=563; 
black), the data of which are overlaid on the total sample popula- 
tion from which these samples were randomly selected. Note that 
the specimens that had sizes <700 mm FL or >1100 mm FL were 
not randomly selected. 
