Scientists Use Cold War Nuclear Bombs to Determine Age of Whale Sharks

This is AIMS researcher Mark Meekan swimming with a whale shark. (Photo courtesy of Wayne Osborn)

(CN) — Scientists have finally been able to determine the age of whale sharks, all due to atomic bomb testing conducted during the Cold War, in new research released Sunday.

A study published in the journal Frontiers in Marine Science detailed how researchers were able to do it, ensuring the survival of the largest fish in the world currently classified as endangered.

Scientists have had difficulty in determining the age of whale sharks due to their lacking of bony structures known as otoliths, used to measure the age of other species of fish.

The vertebrae of whale sharks have unique bands, comparable to the rings of a tree trunk, that increase in number as the fish grows older. Biologists, however, were uncertain just how long it took for the bands to form. Some studies hypothesized new bands formed every year, while others said they took six months.

A multinational team of researchers decided to look at the legacy of the Cold War to find the answer.

The U.S., China, the Soviet Union and other countries conducted several nuclear weapon tests during the 1950s and 1960s, with many such weapons detonated several miles in the air. The result of such testing led to the temporary atmospheric doubling of isotope carbon-14.

The naturally occurring radioactive element is used by archaeologists to carbon date ancient artifacts and fossils. Since carbon-14’s rate of decay is constant, it allows scientists to accurately estimate ages of anything more than 300 years old.

As a by-product of nuclear explosions, carbon-14 also moves through the oceans, producing an elevated signature in ocean life.

Measuiring the carbon-14 levels in two long-dead whale sharks, scientists were able to clearly determine the age of the fish.

“We found that one growth ring was definitely deposited every year,” said Mark Meekan of the Australian Institute of Marine Science. “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.”

Meekan said earlier estimates concluded whale sharks could live as long as 100 years.

“However, although our understanding of the movements, behaviour, connectivity and distribution of whale sharks have improved dramatically over the last 10 years, basic life history traits such as age, longevity and mortality remain largely unknown,” he said.

Meekan added, “Our study shows that adult sharks can indeed attain great age and that long lifespans are probably a feature of the species. Now we have another piece of the jigsaw added.”

Whale sharks can grow up to 40 feet long and can weigh as much as 11 tons. They are popular in international markets where there is a demand for their fins, oil and meat.

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