Pristine Seas Expeditions - Outer Seychelles Islands

Aldabra, possibly the Seychelles 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.

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.