Aldabra, possibly the archipelago’s most famous island, is one of the world’s largest coral atolls and has been a World Heritage site since 1982. Minimally impacted by human activity, it serves as a refuge for hundreds of endemic species and subspecies and is home to the largest population of giant tortoises in the world; more than 150,000 roam a 155-square-kilometer area.
Map by NGS Staff; Charles Preppernau
Departing from Mahé, Seychelles’ most populated island, the Pristine Seas team sailed 965 kilometers to the remote Outer Islands, stopping at Assumption, Cosmoledo, Astove, and Aldabra. Conducting rigorous surveys of the fish and coral species during 200 hours of scientific surveys at 39 locations, they were able to calculate the areas’ fish biomass (or total weight) and analyze their biodiversity.
At Assumption, they followed in the footsteps of Jacques Cousteau and National Geographic writer and photographer Luis Marden—whose legendary dives were featured in the pages of National Geographic magazine in 1956—and had similar experiences with curious groupers. On Cosmoledo, expedition conservationist Mike Fay conducted an overland transect and explored some of the most intact mangroves on Earth, which serve as a nursery habitat for many fish species.
But it was at the “Galápagos of the Indian Ocean”—Aldabra—that the underwater team found what they’d been looking for: sharks. These top predators are the ultimate sign of a healthy marine ecosystem. And they weren’t alone. Parrotfish in schools of hundreds, huge humphead wrasses, rockfish, turtles, groupers, clownfish, triggerfish, and fusiliers flew along with the sharks on a tide coursing from the open sea to the Aldabra lagoon. As expedition leader Paul Rose said, “ … to experience that life-giving pulse at Aldabra together as the Pristine Seas team was remarkable, joyous, and incredibly moving—in all senses of the word!”
With the exception of a previous study at Aldabra Atoll, no comprehensive marine resource assessment had been conducted at these distant locations prior to this expedition. Given their low human populations and limited fishing pressure, remote islands like the Aldabra and Cosmoledo groups offer ideal opportunities for understanding the resilience of reef ecosystems as they face increasing global threats.
Following the expedition, a short film was aired on local TV. A longer film, updated short film, and scientific report were presented to the government of Seychelles in December 2015.
Seychelles now has an opportunity to protect the islands’ unique marine assets and could create the Indian Ocean's second largest marine reserve.