90% of world’s open-ocean sharks died 19 mn yrs ago in mystery extinction event: Study

Nearly 19 million years ago, more than 90 per cent of the world's open-ocean sharks died. A new study by scientists from Yale and the College of the Atlantic has revealed the massive die-off of sharks. The recent discovery has stunned the scientists as the reason for the deaths of the sharks remains unknown. 

90 per cent of the world's sharks died?

It came at a period in history when there were more than 10 times as many sharks patrolling the world’s oceans than there are today. Scientist Elizabeth Sibert and her team were trying to learn more about the fish and shark abundance over the last 80 million years when they stumbled upon this. Elizabeth Sibert, a postdoctoral associate in Yale University’s earth and planetary sciences department and the Yale Institute for Biospheric Studies, lead author of the study has said that extinction happened almost by accident. 

"I study microfossil fish teeth and shark scales in deep-sea sediments, and we decided to generate an 85-million-year-long record of fish and shark abundance, just to get a sense of what the normal variability of that population looked like in the long term", Sibert said in the press release.

"What we found, though, was this sudden drop-off in shark abundance around 19 million years ago, and we knew we had to investigate further", added Sibert.

Sibert said more than 70% of the world's sharks died off -- with an even higher death toll for sharks in the open ocean, rather than coastal waters. It was twice the level of extinction that sharks experienced during the Cretaceous-Paleogene mass extinction event 66 million years ago that wiped out three-quarters of the plant and animal species on Earth.

According to Sibert, the interval is not known for any big changes like climate calamity or ecosystem disruption in the earth's history that led to the steep drop in shark's population.

Leah Rubin, co-author and an incoming doctoral student at the State University of New York College of Environmental Science and Forestry, who was a student at the College of the Atlantic at the time of the research said that the decline in shark population is a matter of concern and this study helps to find the decline in population of shark for last 40 million years.

"This work could tip-off a race to understand this time period and its implications for not only the rise of modern ecosystems, but the causes of major collapses in shark diversity," said Pincelli Hull, an assistant professor of Earth and planetary science at Yale, who was not part of the study.

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