But despite their wide range, whale sharks are endangered , says the International Union for the Conservation of Nature. A family out snorkeling freed a whale shark caught in a heavy fishing rope. Their status and unique body structure has made it difficult to study them, which in turn makes it difficult to create an effective survival plan.
Progress in improving whale shark populations reversed in , when the species was reclassified from vulnerable to endangered. Their lifespan was an essential piece that's been missing for decades -- until Meekan and the team took a novel approach to dating the fish.
How to age the world's largest fish. Previous attempts at aging whale sharks were mixed. To do it, researchers need to slice into vertebrae that, when cut, reveal growth bands -- similar to the rings in tree trunks -- that could prove how old they are.
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The era of greyhound racing in the U. See how people have imagined life on Mars through history. Instead, sharks are aged based on growth rings in their cartilaginous vertebrae — but these growth rings form at different rates in different species and may stop forming after sexual maturity. Nuclear bomb tests carried out from the s onwards created distinctive peaks in carbon This technique has shown that the age estimates for many sharks were wildly off.
For instance, it was thought great white sharks lived only 12 to 15 years, but recent studies have revealed individuals as old as The tests about doubled the amount of carbon in the air, which eventually settled in the ocean, where it became embedded in marine animals from shells to sharks.
About 20 years ago, study co-author Steven Campana of the University of Iceland developed a method to figure out shark ages using the carbon in their cartilage skeletons. Using this method, the team found that based on vertebrae stripes, a foot-long whale shark would be about 50 years old. But whale sharks can grow up to 60 feet long, so they may live much longer. Long-lived, slow-growing animals take longer to recover from population loss.
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