How long does a Whale Shark live?
One of the big marine species that all divers want to see. The slow moving and placid Whale Shark, Rhincodon typus, is the largest living fish species. Growing up to 62ft (18.8m) long, this majestic creature can be found in tropical waters (rarely below 70F/21C) around the world.
A filter-feeder, this shark, along with mega mouths and basking sharks, need very large mouths to be able to feed on plankton and other small fish. They are easily recognised by the white spots that decorate their skin.
The Whale Shark is listed as endangered by the IUCN (International Union for Conservation of Nature), due to it’s long life span and late maturity combined with the impact of fisheries, by-catch and vessel strikes.
Scientists have struggled to work out the age of this species with measurements being difficult. This information is useful to conservationists by helping them develop species survival plans and help to protect them in the wild.
Sexual maturity isn’t reached until the age of about 30yrs with the original estimate of living to an age of 70 yrs. Scientists used counting the rings on a specimens’ vertebrae to see how old they were but weren’t sure that the rings were formed once or twice a year.
Surprisingly, Atomic bomb tests from the cold war have now been used to help scientists calculate more accurately the age of the whale sharks. During the 1950’s and 60’s several countries conducted nuclear tests which resulted in a temporary doubling in the atmosphere of an isotope called Carbon-14. This fallout saturated the air and also the oceans, moving through food webs to leave an elevated carbon signature in every living thing on the planet. A naturally occurring element, Carbon-14 can be used to measure aging as it has a constant and easily measured decay rate. So by studying the levels of carbon-14 in vertebrae of some samples of whale sharks deceased in previous years, the scientists were able to establish that the growth rings do only form one time a year.
So this study was able to prove that whale sharks do grow very slowly and are thus populations are very vulnerable to overfishing. Making conservation of these amazing animals very important.
And it shows that whale sharks live up to 100yrs, some estimate, even a little longer!
Fun Facts:
The name for whale sharks in the native language of Madagascar, marokintana, translates as “many stars” after the beautiful markings on its skin.
By law in the Philippines you must stay at least 4ft from whale sharks. There are fines and possible prison sentences for anyone who touches them
