Thanks to atomic testing during the Cold War, scientists have discovered a way to find out the age of whale sharks.
Many divers dream of the day they find themselves swimming beside a whale shark. Its gentle demeanour and huge size presents a unique humbling experience that is second to none.
Yet, there is much we still do not know about whale sharks.
Today, one of their hidden mysteries have been unlocked–their age.
Until recently, it was hard to fix a number to their age, as they do not have bony structures (otoliths) which are traditionally used to calculate the age of fish.
Another method–counting the distinct bands in their vertebrae, akin to counting rings in tree trunks–was not conclusive, as scientists do not know with certainty how frequently new bands developed and for what reason.
Today, thanks to the atomic bomb tests conducted in the 1950s and 1960s, researchers now have a way of finding out the age of these magnificent creatures.
A by-product of these tests was the radioactive element carbon-14. The tests caused the levels of the carbon-14 isotope in the atmosphere to increase, first in the atmosphere, then subsequently in the oceans. Eventually, it penetrated the food webs and found its way into every living thing on the planet.
"So any animal that was alive then incorporated that spike in carbon-14 into their hard parts," said Mark Meekan, from the Australian Institute of Marine Science in Perth, in a BBC news article. He is one of the authors in a study that was published in the Frontiers in Marine Science journal.
The key to using the carbon-14 as a dating device is due to the fact that we know the rate it decays. So, the older the shark, the less carbon-14 they would have in their body.
"That means we've got a time marker within the vertebrae that means we can work out the periodicity at which those isotopes decay," Dr Meekan added.
The findings of the study revealed that whale sharks do indeed live a very long life, leading Dr Meekan to conclude that "the absolute longevity of these animals could be very, very old, possibly as much as 100-150 years old."
This implies that the species is very vulnerable to being overharvested.
With this discovery, scientists can now provide better guidance on how well a population is doing and whether any fishing can be allowed in a particular area.