There are nuclear-bomb layers in whale sharks’ bones.

Science News has what’s practically a Godzilla story: the discovery that residue from Cold War-era nuclear bomb tests can be found inside the bodies of the world’s largest fish, providing a means to accurately determine their age:

New measurements of carbon-14 in the vertebrae of two whale sharks that lived during the 20th century suggest that growth bands form annually, researchers report in the April 2020 Frontiers in Marine Science. Soviet and American nuclear weapons tests in the 1950s and 1960s produced that carbon-14, which built up in Earth’s atmosphere and oceans. By matching the amount of carbon-14 in different vertebral growth bands with the known carbon-14 levels in surface seawater in different years, the researchers estimated when each band formed — and found that subsequent bands generally grew a year apart.

The total number of growth bands in each dated vertebra indicated that one whale shark, a 10-meter male found in Taiwan, was about 35 years old when it died. The other shark, a female of about the same size collected in Pakistan, was around 50 years old.

Images of vertebrae showing growth bands at the link.