454 
Bomb radiocarbon and tag-recapture dating 
of sandbar shark ( Carcharhinus plumbeus ) 
Allen H. Andrews (contact author ) 1 
Lisa J. Natanson 2 
Lisa A. Kerr 3 
George H. Burgess'* 
Gregor M. Cailliet 5 
Email address for contact author: allen.andrews@noaa.gov 
1 NOAA Fisheries, Pacific Islands Fisheries Science Center 
99-193 Aiea Heights Drive #417 
Aiea, Hawaii 96701 
2 NOAA Fisheries, Apex Predators Program 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
3 University of Massachusetts Dartmouth 
School for Marine Science and Technology 
200 Mill Road, Suite 325 
Fairhaven, Massachusetts 02719 
4 Florida Program for Shark Research 
Florida Museum of Natural History 
University of Florida 
Gainesville, Florida 32611 
5 Moss Landing Marine Laboratories 
8272 Moss Landing Road 
Moss Landing, California 95039 
Abstract — The sandbar shark (Car- 
charhinus plumbeus) was the corner- 
stone species of western North Atlan- 
tic and Gulf of Mexico large coastal 
shark fisheries until 2008 when they 
were allocated to a research-only 
fishery. Despite decades of fishing 
on this species, important life history 
parameters, such as age and growth, 
have not been well known. Some vali- 
dated age and growth information 
exists for sandbar shark, but more 
comprehensive life history informa- 
tion is needed. The complementary 
application of bomb radiocarbon and 
tag-recapture dating was used in this 
study to determine valid age-estima- 
tion criteria and longevity estimates 
for this species. These two methods 
indicated that current age interpre- 
tations based on counts of growth 
bands in vertebrae are accurate to 
10 or 12 years. Beyond these years, 
we could not determine with certainty 
when such an underestimation of age 
begins; however, bomb radiocarbon 
and tag-recapture data indicated that 
large adult sharks were considerably 
older than the estimates derived 
from counts of growth bands. Three 
adult sandbar sharks were 20 to 26 
years old based on bomb radiocar- 
bon results and were a 5- to 11-year 
increase over the previous age esti- 
mates for these sharks. In support of 
these findings, the tag-recapture data 
provided results that were consistent 
with bomb radiocarbon dating and 
further supported a longevity that 
exceeds 30 years for this species. 
Manuscript submitted 3 June 2011. 
Manuscript accepted 8 August 2011. 
Fish. Bull. 109:454-465 (2011). 
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. 
Bomb radiocarbon dating has evolved 
as a useful method for validating the 
age of fishes. The validation of age 
relies on a preserved record of the 
rapid increase in radiocarbon ( 14 C) 
that occurred in the world’s oceans as 
a result of atmospheric testing of ther- 
monuclear devices in the 1950s and 
1960s (Broecker and Peng, 1982). The 
uptake of bomb-produced 14 C by the 
marine environment, reported as A 14 C 
in reference to an established prenu- 
clear 14 C record (Stuiver and Pollach, 
1977), was virtually synchronous in 
the mixed layer of mid-latitude oceans 
and was first recorded from marine 
carbonates in hermatypic corals 
(Druffel and Linick, 1978). Applica- 
tion for the dating of fishes began 
with an innovative comparison of A 14 C 
values recorded in otolith carbonate 
in relation to regional A 14 C records 
from hermatypic corals (Kalish, 1993). 
The temporal specificity of otolith 
A 14 C provided an independent deter- 
mination of age and corroborated age 
estimates determined from counting 
growth zones in otoliths (Campana, 
2001). Bomb radiocarbon dating has 
since been successfully applied to 
validate age estimates of numerous 
teleost fishes (e.g., Andrews et al., 
2007; Ewing et al., 2007; Neilson and 
Campana, 2008), elasmobranchs (e.g., 
Campana et ah, 2002, 2006; Kneebone 
et ah, 2008), and other marine organ- 
isms (e.g., Frantz et ah, 2005; Roark 
et ah, 2006; Stewart et ah, 2006; 
Kilada et ah, 2007). 
The first application of bomb radio- 
carbon dating to validate ages in long- 
lived sharks addressed the porbeagle 
( Lamna nasus) and, preliminarily, 
the shortfin mako ( Isurus oxyrinchus', 
Campana et ah, 2002). Unlike the 
otoliths of bony fishes, in which the 
source of 14 C is inorganic and up- 
take is mostly synchronous with the 
marine environment, the vertebrae 
of porbeagle provided evidence for 
a phase lag of approximately three 
years in the timing of the rise in A 14 C. 
This lag was attributed to a trophic- 
level delay in the propagation of 14 C 
or to depth-related dilution of carbon 
sources, or to both, in relation to the 
