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How Do You Measure the Age of a Whale Shark?

Determining the age of a whale shark is a fascinating process, akin to reading the rings of a tree. Scientists examine growth layers in the shark's vertebrae, each representing a year of life. This method provides insights into the longevity of these gentle giants. How accurate do you think this underwater aging technique is? Join the discussion and find out more.

During the 1950s and 1960s, a number of countries tested nuclear weapons in the Earth’s atmosphere. The United States, Soviet Union, United Kingdom, France and China all detonated devices several kilometers in the air, tainting every living being on land and in the oceans with levels of carbon-14.

Fast-forward to 2020, and scientists are using this radioactive chemical signature embedded in the cartilage skeletons of whale sharks to help determine the age and lifespan of the world’s largest fish.

Carbon-14 residue from Cold War-era nuclear testing has been used to help determine the age of whale sharks.
Carbon-14 residue from Cold War-era nuclear testing has been used to help determine the age of whale sharks.

Whale sharks have "growth bands" in their vertebrae that form over time, but there has been a long-standing scientific debate about how long it takes for each growth band to form. Experts have suggested either six or 12 months per band. This latest research helps to settle that debate by using the carbon-14 residue to determine a whale shark's age, indicating that the fish gets a new band approximately every year.

The mysterious whale shark:

  • “Basically what we showed is we have a time stamp within the vertebrae,” said biologist Mark Meekan in National Geographic. “We count the bands from there, and they appear to be annual.”

  • The methodology has definitively found that, for example, a 32-foot-long (9.8-m) whale shark is about 50 years old.

  • Whale sharks are endangered, facing considerable threats from boat strikes and fish harvesters. These whales love to bask in the sun near the water’s surface, where boat propellers present a deadly danger.

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    • Carbon-14 residue from Cold War-era nuclear testing has been used to help determine the age of whale sharks.
      Carbon-14 residue from Cold War-era nuclear testing has been used to help determine the age of whale sharks.