Data compiled from atomic bomb tests that were conducted during the Cold War have helped scientists to accurately predict the age of the world’s largest fish.

Whale sharks are slow-moving, filter-feeding carpet sharks and are the largest known living species of fish. In fact, the largest confirmed individual whale shark had a monstrous length of 18.8 m. The whale shark also holds many records for size in the animal kingdom, most notably being by far the largest living non-mammalian vertebrate.

These creatures are long-lived but scientists have always struggled to work out the exact ages of these endangered fish. However, using the world’s radioactive legacy scientists now have a workable method that can help with the species survival.

To date, scientists have tried to count distinct lines in the vertebrae of dead whale sharks. These lines act like rings within a tree trunk, increasing as the fish ages. However, scientists have always been unsure as to how often these rings can actually form and the reasons behind their formation.

Now researchers have suggested a more accurate method of determining the whale sharks’ true age.

From the late 1940s, several nations including the US, the Soviet Union, Great Britain, France and China conducted multiple atomic bomb tests in different locations throughout the world. One side effect of all these nuclear 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. Considering scientists know the rate at which the Carbon-14 isotope decays, it is a very useful marker in determining age.

Basically the older the creature, the less Carbon-14 you’d expect to find within their body.

By accurately estimating the age of whale sharks, these scientists will be able to provide more intelligent guidance regarding how well a population is surviving and whether any fishing can be allowed in specific regions.

In many tropical regions, whale shark tourism is now a major attraction. The researchers suggest that encouraging co-operation between different countries along the vast routes that whale sharks follow could ultimately be key to their survival.

The study has been published in the journal Frontiers in Marine Science.