A team of researchers with members from the U.S., France and the U.K. has found evidence showing reductions in shark populations in a part of the Indian ocean thought to be nearly pristine—the Chagos archipelago. In their paper published on the open access site Science Advances, the group describes their study of shark populations in the archipelago over time and what they found.
In this modern age of human encroachment across the planet, there are still some places that are believed to be very much like they were before humans arrived, including the Chagos archipelago in the middle of the Indian Ocean, thousands of miles away from any major land mass. In this new effort, the researchers wondered if, despite its remoteness, the archipelago might actually have been changed by humans. They chose this particular archipelago because unlike similar ones, it has a recorded history. Humans have been visiting the archipelago and places near it for hundreds of years, and many of them have kept records of things like fish and shark population estimates. The researchers chose to focus on sharks, because they are so abundant and because they are a dominant species, and thus have a major impact on the environment in which they live.
The researchers gathered data from a variety of sources, starting with a survey conducted in the area back in 1948. They were also able to obtain data from the 1970s as teams of researchers in the area began conducting surveys by actually getting in the water. They also consulted catch records going back approximately half a century.
The team analyzed their data with an algorithm designed to offer population predictions given a variety of environmental conditions. It suggested that despite appearances, shark populations in the archipelago are far lower than they would have been had humans not appeared on the scene—in some cases, dramatically so.
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Provided by phys.org