Scientists Estimate Age of World's Largest Fish
2020-04-19
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1Scientists have recently discovered how to compute the age of whale sharks, Earth's largest fish.
2Researchers used information about radioactivity levels from Cold War-era atomic bomb testing.
3They determined that bands form in the shark vertebrae every year, like a tree's growth rings.
4They reached their conclusion by measuring levels of carbon-14.
5The naturally occurring radioactive element is also a product of nuclear explosions.
6It was already known that these bands existed and increased in number as sharks aged.
7But it was unclear whether new rings appeared yearly or every six months.
8The researchers compared carbon-14 levels in the rings to data on changes in carbon-14 levels over time.
9They compared them, especially, to the years of atmospheric nuclear tests in the 1950s and 1960s.
10Joyce Ong is a marine scientist at Rutgers University in New Jersey.
11She was the lead author of the study that was published recently in the journal Frontiers in Marine Science.
12"These elevated levels of carbon-14 first saturated the atmosphere, then oceans and moved through food webs into animals, producing elevated levels in structures such as the vertebrae of whale sharks," Ong said.
13Whale sharks have a brownish-grayish color on the back and sides with white spots.
14The largest ones measure some 18 meters in length.
15They swim great distances through the world's tropical oceans to find food and feed on small organisms taken out of the water.
16The discovery enables scientists to measure a whale shark's age after its death.
17But just as importantly, it shows that these endangered marine giants grow slowly.
18Mark Meekan, a co-author, is with the Australian Institute of Marine Science in Perth.
19He said, "For the management of any marine species, knowledge of growth rate is critical as it determines the resilience of populations to threats such as fishing."
20Meekan said, "We thought that it was possible that they could reach ages of as much as 100 years, but we weren't really sure..."
21The researchers tested carbon-14 levels in long-dead whale sharks whose remains were stored in laboratories.
22The oldest one tested, stored in Pakistan, had lived 50 years.
23I'm John Russell.
1Scientists have recently discovered how to compute the age of whale sharks, Earth's largest fish. 2Researchers used information about radioactivity levels from Cold War-era atomic bomb testing. They determined that bands form in the shark vertebrae every year, like a tree's growth rings. 3They reached their conclusion by measuring levels of carbon-14. The naturally occurring radioactive element is also a product of nuclear explosions. 4It was already known that these bands existed and increased in number as sharks aged. But it was unclear whether new rings appeared yearly or every six months. 5The researchers compared carbon-14 levels in the rings to data on changes in carbon-14 levels over time. They compared them, especially, to the years of atmospheric nuclear tests in the 1950s and 1960s. 6Joyce Ong is a marine scientist at Rutgers University in New Jersey. She was the lead author of the study that was published recently in the journal Frontiers in Marine Science. 7"These elevated levels of carbon-14 first saturated the atmosphere, then oceans and moved through food webs into animals, producing elevated levels in structures such as the vertebrae of whale sharks," Ong said. 8Whale sharks have a brownish-grayish color on the back and sides with white spots. The largest ones measure some 18 meters in length. They swim great distances through the world's tropical oceans to find food and feed on small organisms taken out of the water. 9The discovery enables scientists to measure a whale shark's age after its death. But just as importantly, it shows that these endangered marine giants grow slowly. 10Mark Meekan, a co-author, is with the Australian Institute of Marine Science in Perth. He said, "For the management of any marine species, knowledge of growth rate is critical as it determines the resilience of populations to threats such as fishing." 11Meekan said, "We thought that it was possible that they could reach ages of as much as 100 years, but we weren't really sure..." 12The researchers tested carbon-14 levels in long-dead whale sharks whose remains were stored in laboratories. The oldest one tested, stored in Pakistan, had lived 50 years. 13I'm John Russell. 14Will Dunham reported on this story for Reuters. John Russell adapted it for Learning English. Hai Do was the editor. 15_____________________________________________________________ 16Words in This Story 17vertebrae - n. one of the small bones that are linked together to form the backbone 18data -- n. facts or information used usually to calculate, analyze, or plan something 19atmospheric -- adj. of or relating to the atmosphere of the Earth or another planet 20elevated -- adj. higher than normal 21saturate - v. to fill (something) completely with something 22species -- n. a group of animals or plants that are similar and can produce young animals or plants : a group of related animals or plants that is smaller than a genus 23resilience - n. the ability to become strong, healthy, or successful again after something bad happens