Despite the overwhelming fame and notoriety of the
great white shark (Carcharodon carcharias)
in the media, the reality is that there exists relatively little scientific
data on this species. A group of researchers, led by Li Ling Hamady at Woods
Hole Oceanographic Institution, used radiocarbon analysis to confirm the age of
8 white sharks and found that white sharks in the northwest Atlantic Ocean
(NWA) were likely to live up to 70 years.
The previous method of aging great white sharks –
as with most fishes - was to count the number of mineralised layers laid down in
specific tissue such as vertebrae; with this method it is assumed that the
layers are laid down on an annual basis. However this method can be vulnerable
to misinterpretation and collaboration of results gained in this manner by
using radiocarbon dating has gained popularity.
The study, which was published in the journal PLOS ONE, increase exponentially
the estimated longevity of C. carcharias in
NWA. These results not only have implications for a need to reassess the
methods by which sharks are aged, but an increased expected longevity in white
sharks raises grave conservation issues. Like most sharks, white sharks are
slow to reach maturity and have small litters. If NWA white sharks exhibit even
greater longevity than we first thought, this could mean that their expected
age to reach sexual maturity could also be longer than originally estimated and
this would make white sharks even more vulnerable to fishing pressure and
population decline. The white shark is listed as Vulnerable in the IUCN Red
List of Threatened Species; many countries protect white sharks but a poor
media image has left white sharks vulnerable to persecution – such as the
recent decision of the Western Australian Government to bait for large sharks.
Obtaining a greater knowledge of the growth rates
and longevity of white sharks will be beneficial for ensuring the protection of
this species.
Hamady LL, Natanson LJ, Skomal GB, Thorrold SR (2014) Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks. PLoS ONE 9(1):
e84006. doi:10.1371/journal.pone.0084006
