346 
Abstract — Preliminary validation 
of annual growth band deposition 
in vertebrae of great hammerhead 
shark (Sphyrna mokarran) was con- 
ducted by using bomb radiocarbon 
analysis. Adult specimens (n= 2) were 
collected and thin sections of verte- 
bral centra were removed for visual 
aging and use in radiocarbon assays. 
Vertebral band counts were used to 
estimate age, and year of formation 
was assigned to each growth band by 
subtracting estimated age from the 
year of capture. A total of 10 samples 
were extracted from growth bands 
and analyzed for A 14 C. Calculated 
A 14 C values from dated bands were 
compared to known-age reference 
chronologies, and the resulting pat- 
terns indicated annual periodicity of 
growth bands up to a minimum age 
of 42 years. Trends in A 14 C across 
time in individual specimens indi- 
cated that vertebral radiocarbon is 
conserved through time but that 
habitat and diet may influence A 14 C 
levels in elasmobranchs. Although 
the age validation reported here must 
be considered preliminary because 
of the small sample size and narrow 
age range of individuals sampled, it 
represents the first confirmation of 
age in S. mokarran, further illustrat- 
ing the usefulness of bomb radiocar- 
bon analysis as a tool for life history 
studies in elasmobranchs. 
Manuscript submitted 22 December 2009. 
Manuscript accepted 19 May 2010. 
Fish. Bull. 108:346-351 (2010). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Age validation of great hammerhead shark 
( Sphyrna mokarran ), determined by 
bomb radiocarbon analysis 
Michelle S. Passerotti (contact author ) 1 
John K. Carlson 1 
Andrew N. Piercy 2 
Steven E. Campana 3 
Email address for contact author: Michelle.Passerotti@noaa.gov 
1 Southeast Fisheries Science Center 
National Marine Fisheries Service 
National Oceanic and Atmospheric Administration 
3500 Delwood Beach Road 
Panama City, Florida 32408 
2 Florida Program for Shark Research 
Florida Museum of Natural History 
University of Florida 
P.O. Box 117800 
Gainesville, Florida 32611 
3 Bedford Institute of Oceanography 
PO. Box 1006 
Dartmouth, Nova Scotia, Canada B2Y 4A2 
Validation of the periodicity of ver- 
tebral growth band deposition over 
the entire life span of a species is an 
important aspect of age estimation 
and growth determination in elasmo- 
branch fishes (Caillet and Goldman, 
2004; Francis et al., 2007). Accurate 
age estimation is critical because it 
forms the basis for calculating growth 
and mortality rates, age at maturity, 
and estimates of longevity, all of which 
are essential for population assess- 
ment. The need for accurate age and 
growth estimates is especially great 
for many elasmobranch species, which 
tend to be data poor and highly vul- 
nerable to fishing pressure (Musick, 
1999). Bomb radiocarbon dating has 
been successfully used to validate age 
estimates for several elasmobranch 
species (e.g., Campana et al., 2002; 
Kneebone et al., 2008; McPhie and 
Campana, 2009). The peak in atmo- 
spheric radiocarbon ( 14 C) from test- 
ing nuclear bombs in the 1950s and 
1960s is used as a marker that can 
be dated in the calcified structures 
of marine organisms. Bomb testing 
yielded synchronous known-age refer- 
ence chronologies in corals, bivalves, 
and fish otoliths worldwide (Campana, 
1997; Druffel, 1989), which can be 
used to confirm the accuracy of age 
estimates for various marine species 
(Campana et al., 2002). The presence 
of a tracer over such a protracted time 
span makes bomb radiocarbon analy- 
sis highly suitable for age validation, 
especially for typically long-lived elas- 
mobranchs. 
The great hammerhead shark 
(Sphyrna mokarran) is a large (maxi- 
mum size of 550-610 cm total length 
[TL] ) cosmopolitan species found cir- 
cumtropically in both inshore and 
oceanic habitats to depths of over 
80 meters (Compagno, 1984). Great 
hammerhead sharks tend to be reef- 
associated, but some populations un- 
dertake seasonal offshore migrations 
(Compagno, 1984). Life history in- 
formation for the great hammerhead 
shark is very limited; reports consist 
mostly of notes on their reproduction 
(Stevens and Lyle, 1989). There are 
no published age validations for S. 
mokarran. 
The vulnerability of great ham- 
merhead sharks to fishing pressure 
is potentially high given the tenden- 
cy of elasmobranchs to exhibit slow 
growth, late age at maturity, and 
