About 19 million years ago, a mysterious event wiped out about 70 per cent of the world’s shark population, found a study published on June 4 in the journal Science. The extent of the shark die-off was twice the number of sharks killed when an asteroid had hit the earth 66 million years ago. The new study was published on June 4 in the journal Science. However, the scientists have no idea about what could be the cause of the shark population going almost extinct. “We happened upon this extinction almost by accident," said Elizabeth Sibert, the lead author of a study and a postdoctoral researcher at Yale’s Department of Earth and Planetary Sciences, in a news release by the Yale University.
According to Sibert, her team decided to build an 85-million-year long record of shark and fish populations. The scientists wanted to understand how the populations varied in the long term and that is when they found this mysterious drop-off. They found that the death toll for the sharks living in the open ocean was much higher compared to those who lived near coastal areas.
However, there is no big ecosystem disruption or climate calamity known at the time but the population of the sharks was drastically reduced.
According to Sibert, the interval is not known of any big changes in the earth’s history, “yet it completely transformed the nature of what it means to be a predator living in the open ocean."
Another part of the mystery is that the shark population did not rebound after the sudden die-off.
Studying how this drastic extinction affected the remaining shark populations, and if they changed their habitat to avoid the open ocean, can help us understand how the decline in shark population can affect marine ecosystems. According to scientists, sharks are declining at an alarming rate. According to a study that was published in Nature in January, the shark population living in the open ocean has reduced by 70 per cent over the past half-century. The reasons for this decline is unsustainable overfishing. However, for the die-off that happened 19 million years ago, humans were not present on the earth.
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