456 
Fishery Bulletin 109(4) 
Table 1 
Size, year of capture, estimated age, and sex of sandbar shark (Carcharhinus plum 
beus) sampled in this study. 
Specimen 
number 
Fish fork length 
(cm) 
Year of capture 
Estimated age 
(yr) 
Estimated 
birth year 
Sex 
SB 43 
136.5 
1965 
10.3 
1955 
F 
SB 47970 
160.0 
1985 
14.2 
1971 
F 
SB 745 
167.0 
1976 
16.4 
1960 
M 
SB 118 
167.5 
1966 
15.6 
1950 
F 
SB 749 
170.0 
1981 
16.1 
1965 
F 
Cailliet et al., 2006). The location of the series of 
drill holes was carefully chosen to extract the tar- 
geted growth-band pair within the corpus calcareum 
and to minimize the possibility of including external 
vertebral material not formed during that year of 
growth. The intermedialia of the vertebral centrum 
was avoided because banding is poorly defined near 
the corpus calcareum. The width of growth-band pairs 
was used as the target size for extraction therefore, 
the amount of material extracted decreased as the 
width of growth band pairs decreased. Drilling depth 
was just short of the depth required to pass completely 
through the section to provide a secure mount for the 
extracted block of vertebral material. Final removal 
of the sample was made with a razor blade, firmly 
pressed to the slide. 
A total of thirteen growth-band pairs were extracted 
from the corpus calcareum of the five sandbar shark 
vertebrae. The first growth-band pair after the birth 
band (estimated to be the first year of growth after 
birth) and one to four subsequent growth band pairs 
farther toward the outer edge of the corpus calcareum 
were extracted from each vertebra. The last band pair, 
corresponding to the last year of growth, was targeted 
to provide a sample where time of formation was con- 
strained by the collection date. The location for extrac- 
tion of the most recent vertebral sample was usually 
proximal to the distal tip of the corpus calcareum be- 
cause of reduced band width and poor edge condition at 
the tip, The extracted samples weighed approximately 
10 mg; the specific values were not specifically recorded 
owing to an oversight. 
Demineralization of vertebral samples was performed 
to isolate the organic portion (collagen) by dissolving 
the inorganic component that can increase carbon yield 
from the accelerator mass spectrometry (AMS) graphi- 
tization process (Brown et al., 1988). Samples were 
soaked in 0.25 N HC1 for 24 hours at refrigerator tem- 
peratures to reduce reaction rate. Treated samples were 
dried in an oven at 60°F (16°C) and placed in clean 
quartz tubes. Copper oxide (CuO, oxidizing agent) and 
silver (Ag, for impurity removal: SOx and NOx) were 
added to the treated organic samples at levels specified 
for AMS (Center for Accelerator Mass Spectrometry 
[CAMS], Lawrence Livermore National Laboratory). 
Quartz tubes were evacuated, sealed, and heated for 2 
hours at 900°C to convert the organic carbon to C0 2 . 
Sample C0 2 was converted to graphite (Vogel et al., 
1984, 1987) and measured for 14 C content with AMS 
at the CAMS. The 14 C values were reported as 4 14 C 
(Stuiver and Polach, 1977) and age corrected by using 
the estimated year of formation in relation to 1950. 
The 14 C values were then adjusted for fractionation by 
using an assumed <? 13 C value of -15%e based on a previ- 
ous study (Campana et al., 2002) and other standards 
(Stuiver and Polach, 1977). 
Sandbar shark 4 14 C data were compared with exist- 
ing hermatypic coral Z\ 14 C records for the WNA for a 
temporal alignment. Because this species is known to 
cover great distances along the Atlantic seaboard sea- 
sonally and ontogenetically (Grubbs et al., 2007), the 
Z\ 14 C records from hermatypic coral off the Florida Keys 
and Bermuda (Druffel and Linick, 1978; Druffel, 1989) 
and validated shark vertebrae (porbeagle from western 
North Atlantic; Campana et al., 2002) were used as 
reference chronologies for comparison to the measured 
values from aged sandbar shark vertebrae. Fish otolith 
4 14 C records were also considered for calibration pur- 
poses (i.e. , Campana et al., 2008) but were not used in 
our analysis because the Z\ 14 C record was intermediate 
in time and magnitude to the coral and shark 4 14 C 
records and did not provide additional temporal clar- 
ity. Age of sandbar sharks was calibrated by aligning 
measured 4 14 C values with the z\ 14 C reference chronolo- 
gies, and estimated age was adjusted for some sharks 
according to the temporal alignment of these data. 
OTC tag-recapture dating 
Tag-recapture data were obtained and analyzed by 
using the methods of Casey et al. (1985) and by using 
only recaptures obtained since the publication by Casey 
and Natanson (1992). In addition, vertebrae were pro- 
cessed from OTC-injected and recaptured specimens. 
Two adjacent vertebrae were sectioned and examined 
concurrently to align band pairs with the OTC mark. 
One section was removed for histological examination 
(Casey et al., 1985) and the other, a thicker section, was 
made to preserve the OTC mark. The thicker section 
was made by using a gem saw (Raytech, Middleton, CT) 
