Cold War atomic bomb testing has helped scientists correctly determine the age of whale sharks for the first time to help ensure the future of the endangered and protected species.
Until now, the age of the sharks has been difficult to measure, as sharks and rays lack bony structures that are used to age other fish.
A team of researchers, including Mark Meekan from the Australian Institute of Marine Science in Perth, turned to the radioactive legacy of the Cold War’s nuclear arms race.
During the 1950s and 1960s, the US, Soviet Union, Britain, France and China conducted tests of nuclear weapons, many of which were detonated several kilometres in the air.
One result of the blasts was an atmospheric doubling of an isotope called carbon-14.
Carbon-14 is commonly used by archaeologists and historians to date ancient bones and artefacts due to its constant rate of decay.
The isotope gradually moves through food webs into living animals and plants, producing an elevated carbon-14 signature.
Scientists have found distinct bands in whale shark vertebrae.
Measuring the radioisotope levels in successive growth rings allowed a clear determination of how often they were created, giving an indication of the shark’s age.
Using bomb radiocarbon data, Dr Meekan and his team conducted testing of two deceased whale sharks in Pakistan and Taiwan.
“We found that one growth ring was definitely deposited every year,” Dr Meekan said.
“This is very important, because if you over or under-estimate growth rates you will inevitably end up with a management strategy that doesn’t work, and you’ll see the population crash.”
One of the sharks was conclusively established as 50 years old at death – the first time such an age has been unambiguously verified.
Today, whale sharks are endangered and protected as a high-value species for eco-tourism.