KARACHI: Data from atomic bomb tests conducted during the Cold War have helped scientists accurately age the world’s biggest fish, according to a BBC report.

According to a study published in the journal Frontiers in Marine Science, whale sharks can live an incredibly long time.

Whale sharks are both the biggest fish and the biggest sharks in existence.

Growing up to 18m in length, and weighing on average of about 20 tonnes, their distinctive white spotted colouration makes them easily recognisable.

However, the species is now classified as endangered because of over-fishing in places like Thailand and the Philippines, the report said.

To date, scientists have tried to count distinct lines in the vertebrae of dead whale sharks. These act like rings in a tree trunk, increasing as the animal gets older. But scientists, it said, had been unsure about how often these rings could form and the reasons behind them.

The BBC reported that the researchers from the Australian Institute of Marine Science had come up with a more accurate way of determining the whale sharks’ true age.

The team managed to find two long-dead specimens stored in Pakistan and Taiwan.

“The absolute longevity of these animals could be very, very old, possibly as much as 100-150 years old,” author Dr Mark Meekan, from the Australian Institute of Marine Science in Perth told BBC.

“This has huge implications for the species. It suggests that these things are probably intensely vulnerable to over-harvesting,” he added.

The scientists said their results explained why whale shark numbers had collapsed in locations like Thailand and Taiwan where fishing has taken place.

“They are just not built for humans to exploit,” said Dr Meekan in the report.

Atomic bomb analysis

From the late 1940s, several nations including the US, the Soviet Union, Great 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, the BBC report said.

Over time, every living thing on the planet had absorbed this extra Carbon-14 which still persisted. But as scientists knew the rate at which this isotope decays, it was a very useful marker in determining age.

The older the creature, the less Carbon-14 one would expect to find, the report said.

“So any animal that was alive then incorporated that spike in Carbon-14 into their hard parts,” Dr Meekan told BBC.

Published in Dawn, April 7th, 2020