The whale shark is a slow-moving, filter-feeding carpet shark and the largest known extant fish species, with the biggest on record measuring 62 feet. They are found in open waters of the tropical oceans and are rarely found in temperatures below 21C. Studies looking at vertebral growth bands and the growth rates of free-swimming sharks have estimated a whale shark can live between 80 to 130 years, but scientists have struggled to accurately age them for years.
But using the world’s radioactive legacy they now have a workable method that can help the species’ survival.
From the late Forties, several countries including the US, the Soviet Union, Britain, France and China conducted atomic bomb tests in different locations.
One side effect of all these explosions was the doubling of an atom type, or isotope, called Carbon-14 in the atmosphere.
Over time, every living thing on the planet has absorbed this extra Carbon-14 which still persists.
But as scientists know the rate at which this isotope decays, it is a useful marker in determining age – the older the creature, the less Carbon-14.
And now it has shed new light on the whale shark.
Dr Mark Meekan, from the Australian Institute of Marine Science in Perth, said: “So any animal that was alive then incorporated that spike in Carbon-14 into their hard parts.
“That means we’ve got a time marker within the vertebrae that means we can work out the periodicity at which those isotopes decay.”
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While the species has recently been upgraded from threatened to endangered on the IUCN Red List, the scientists believe that their work could help efforts at conservation.
By being able to accurately estimate the age of whale sharks, the scientists will be able to provide more accurate guidance on how well a population is doing and whether any fishing can be allowed.
Dr Meekan continued: “Whale sharks are a fantastic ambassador for marine life and one that has lifted so many people out of poverty.
“This is a good news story – and it shows there is a silver lining to the mushroom cloud after all.”