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Fishery Bulletin 96(2), 1998 
spheric testing of atomic bombs in the 1950’s and 
1960’s (Nydal and Lovseth, 1983). This product of 
nuclear testing was subsequently incorporated into 
the world’s oceans in a manner which has been well 
described at large spatial scales (Broecker et al., 1985; 
Duffy et al., 1995). Through analysis of annular 
growth rings in coral, other workers demonstrated 
that bomb radiocarbon was incorporated into the 
accreting coralline structure in concentrations pro- 
portional to those present in the water column 
(Druffel and Linick, 1978; Nozaki et al., 1978). Thus 
the time series of bomb radiocarbon in the coral was 
shown to reflect that present in the surface marine 
environment, which increased by about 20% between 
1950 and 1970. Using accelerator mass spectrometry 
(AMS) as a sensitive and accurate assay tool, Kalish 
(1993) was able to demonstrate that the otoliths of a 
New Zealand fish species also incorporated 14 C and 
that the time series of radiocarbon reconstructed 
from the presumed otolith annuli was similar to that 
present in nearby corals. Thus he was able to infer 
that the otolith annuli had been interpreted and aged 
correctly because systematic under- or over-ageing 
would have resulted in a phase shift between the 
otolith 14 C and the coral 14 C time series. 
Subsequent work by both Kalish (1995a, 1995b; 
Kalish et al., 1996) and Campana (1997) has con- 
firmed the value of the bomb radiocarbon technique 
for solving problems of age validation in a variety of 
fish species. Furthermore, recent work by Campana 
(1997) has confirmed that the assumption of 
synchronicity between otolith and marine carbonate 
14 C chronologies is justified, because the period of 
rapid increase in the 14 C chronology recorded in age-1 
haddock ( Melanogrammus aeglefinus ) otoliths was 
synchronous with that reported for other taxa in the 
North Atlantic, whether based on corals (Druffel, 
1989) or bivalves (Weidman and Jones, 1993). Such 
large-scale synchronicity implies that the 14 C time 
series reconstructed from the otolith cores of old fish 
can be compared to one of the other North Atlantic 
time series; errors in annulus-based age determina- 
tions would manifest themselves as noncoherent time 
series. The only constraint to such an age determi- 
nation procedure is the requirement for otoliths of 
fish spawned during and adjacent to the 1958-65 
period, so as to take advantage of the unique 14 C 
values during that period. 
The black drum, Pogonias cromis, with its puta- 
tive lifespan of some 60 yr and estuarine dependence 
during early life (Jones et al., 1997), is an ideal can- 
didate for age validation with 14 C. This large sciaenid 
is distributed along the east coast of the U.S. (Jones 
et al., 1997) and throughout the Gulf of Mexico, where 
it is fished commercially. However its relatively low 
abundance results in low recapture rates after tag- 
ging. Accordingly, attempts to validate annulus for- 
mation with mark-recapture techniques in the older 
age groups have been unsuccessful. Yet such valida- 
tion is critical to the proper management of this fish 
in the Chesapeake Bay region, where the greatest 
numbers of presumably old fish are harvested. 
Here we report the first pre- and post[atom]bomb 
14 C otolith chronology for black drum, and the first 
such chronology for any long-lived fish species in the 
North Atlantic. We use this 14 C chronology to deter- 
mine the absolute ages of individual fish, and through 
comparison with otolith annulus counts from the 
same fish, we then confirm the accuracy of otolith 
annuli as indicators of absolute age in this species. 
Materials and methods 
Adult black drum (n=31) with a mean ±SE total 
length of 111 ±1 cm (range=95-119 cm) were collected 
with anchored and drifted gill nets during research 
surveys of the eastern shore of Chesapeake Bay in 
Apr-May 1990. To estimate age based on annuli, one 
randomly selected sagittal otolith of each otolith pair 
was sectioned transversely through the core, and the 
annuli were counted under reflected light. The ra- 
dius of the presumed first annulus was confirmed 
through measurements of the dimensions of intact 
sagittae collected from young-of-the-year black drum, 
which indicated that the first annulus in a trans- 
verse section should be approximately 7 mm wide 
and 2 mm thick. After ageing with reflected light 
microscopy, the remaining halves of each otolith were 
stored dry in paper envelopes in preparation for 14 C 
assay. 
To extract a sample of the first year’s growth from 
each otolith, a transverse section 1-mm thick was 
made with an Isomet saw immediately adjacent to 
that made for ageing. Although this second section 
was adjacent to the otolith core, the length of the 
age-1 otolith (~8 mm) indicates that most of the first 
year’s growth was still present in the section. After 
recording a digital image of the annuli, a Dremel tool 
was used to remove all otolith material distal to the 
first annulus. The remaining core material was then 
stored in aluminum foil and submitted for 14 C assay 
by AMS. All samples were also individually assayed 
for 8 13 C, which was used to correct for isotopic frac- 
tionation effects. Radiocarbon values were subse- 
quently reported as A 14 C, which is the per mil ( %c ) 
deviation of the sample from the radiocarbon con- 
centration of 19th-century wood, corrected for sample 
decay prior to 1950 according to methods outlined 
by Stuiver and Polach (1977). 
