Beautifully patterned with white spots and stripes, the 60-foot-long whale shark is the largestand one of the most strikingfish in the sea. Though it’s beloved by ecotourists and native to temperate oceans the world over, very little is known about these behemothsincluding how long they live.
Recent investigations into other shark species have revealed astounding life-spans: The Greenland shark, for example, can live nearly 300 years, longer than any other vertebrate on Earth. (Many more sharks, such as the great white, near the 100-year mark.)
Those discoveries are largely because of advanced methods for determining a shark’s age, such as tracing carbon-14, a rare type of radioactive isotope that is a byproduct of Cold War-era bomb detonations, in shark skeletons. Measuring amounts of this element can tell scientists a shark’s age more accurately than the previous approach, counting tree-like growth rings on whale shark vertebrae. That’s because how much time each ring represents has long been a subject of dispute.
Now, researchers using radiocarbon dating have identified the remains of a whale shark that lived 50 years, the most ever for that species, says study leader Mark Meekan, a fish biologist at the Australian Institute of Marine Science.
He adds that it seems possible that these really big sharks could live to be about a hundred years old.
Meekan says his study, published April 6 in the journal Frontiers in Marine Science, is crucial to the conservation of these endangered species.
That’s because the whale shark’s longevity makes the species as a whole more vulnerable to threats such as legal and illegal fishing, warming ocean temperatures, and ship strikes.
This study is really important because it gets rid of some of those questions about the age and growth patterns of whale sharks, says Taylor Chapple, a research scientist specialising in sharks at Oregon State University.
Conservationists need to know the growth rate of a species, he says, because a slower-growing species is more susceptible to extinction than one that reproduces quickly. The whale shark’s global population has fallen by more than half over the past 75 years, according to the International Union for Conservation of Nature.
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