Campana and Jones: Radiocarbon applied to age validation of Pogonias cromis 
191 
carbon is thought to provide about one third of the 
carbon to the otoliths (Kalish, 1991; Schwarcz et al., 
1998). 
Although the 14 C assays reported here provided 
absolute age determinations for black drum between 
the ages of 15 and 42 yr, they were of greater value 
for their use in confirming the accuracy of the crite- 
ria generally used to interpret otolith annuli. Com- 
pared with otoliths of many other fish species, black 
drum otoliths form remarkably clear annuli; thus it 
would have been somewhat surprising if their inter- 
pretation had proven to be incorrect. Indeed, on the 
basis of marginal increment analysis, an annual rate 
of otolith annulus formation has already been dem- 
onstrated for black drum (Beckman et al., 1990), as 
well as for the closely related red drum, Sciaenops 
ocellatus (Murphy and Taylor, 1991). An annual rate 
of formation has also been reported for annuli in 
young black drum scales (Matlock et al., 1993), de- 
spite the fact that scale annuli indicate a maximum 
age of only 10 yr for black drum in Chesapeake Bay. 
In any event, confirmation of the frequency of annu- 
lus formation cannot be used to infer absolute age 
with the same accuracy as a direct measure of abso- 
lute age. In light of the statistical uncertainty around 
the correspondence between the black drum 14 C chro- 
nology and that expected of an estuary, it appears 
reasonable to conclude that otolith annuli can be used 
to determine the age of a sample of black drum with 
an accuracy of at least ±1-3 yr, corresponding to 3- 
7% for a collection of 40-yr-old fish. The confidence 
interval for an individual fish would be, of course, 
somewhat larger. 
Although techniques such as the mark-recapture 
of chemically tagged fish can be used to validate the 
annual frequency of formation of growth increments 
in the otolith accurately , especially in young or abun- 
dant fishes, only radiocarbon from nuclear testing 
has the potential to confirm both annulus formation 
and absolute age in individual fish. The results of 
this study suggest that bomb radiocarbon can be used 
to determine the accuracy of an alternative ageing 
technique to within 1-3 yr. In addition, the presence 
of a strong phase coherence across a broad array of 
organisms and areas has excellent implications for 
the age determination of other North Atlantic fish 
species. The only constraints to this procedure are 
the relatively high costs (~$700-$l,000 per otolith) 
and the requirement for fish hatched during the 
1958-65 period, so as to take advantage of the unique 
14 C values during that period. Although the avail- 
ability of suitable otolith samples may limit the ap- 
plicability of this approach to specific stocks and spe- 
cies, use of bomb-derived radiocarbon as a dated 
otolith marker appears to provide one of the most 
accurate and logistically feasible methods for age 
validation that is currently available. 
Acknowledgments 
We thank Joanne Hamel for her technical expertise 
in preparing the otoliths, John Kalish for helpful com- 
ments on the interpretation of freshwater 14 C sig- 
nals, and an anonymous reviewer for numerous ex- 
cellent suggestions and insights. The 14 C assays were 
carried out under contract to Beta Analytic Inc. This 
study was supported by a Wallop/Breaux Grant for 
Sport Fish Restoration from the U.S. Fish and Wild- 
life Service through the Virginia Marine Resource 
Commission (FR-88-R3-7) and by the National Sci- 
ence Foundation (OCE-9416579). 
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