First-Ever Sighting of Sliteye Shark in Chagos Archipelago
A sliteye shark (Loxodon macrorhinus) has been recorded for the first time in the Great Chagos Bank, the world’s largest coral atoll system in the remote Chagos Archipelago, Indian Ocean. This groundbreaking discovery marks an important step in understanding the species’ geographic range and highlights the ecological value of deepwater seagrass ecosystems.
The sliteye shark is currently listed as a near-threatened species on the IUCN Red List, with populations facing up to a 29% decline in the next 15 years due to fishing pressures.
Why the Discovery Matters
The Chagos Archipelago Marine Protected Area (MPA) is home to vast reefs, coral systems, and seagrass meadows. The discovery of the sliteye shark here shows the region harbors even more undocumented biodiversity than previously thought.
This finding also emphasizes the importance of deepwater habitats—areas often overlooked in conservation research. Protecting these ecosystems is vital not only for sharks but also for the 110+ fish species and green turtles that depend on them.
Unique Features of the Sliteye Shark
The sliteye shark gets its name from its distinctive slit-shaped eyes, which are believed to improve vision in low-light conditions. This adaptation makes it well-suited for both dimly lit deepwater environments and clear shallow waters.
The Chagos sightings occurred in previously unstudied seagrass beds on the southern rim of the Great Chagos Bank. Using Baited Remote Underwater Video (BRUV) systems, researchers observed the sharks at depths of 23–29 meters, just 11 km apart.
Credit: Charlotte Oulton
Insights From the Research Team
Lead researcher Charlotte Oulton, a Marine Conservation student at Swansea University, expressed excitement about the finding:
“Discovering the sliteye shark in the Chagos Archipelago was incredibly exciting. Not only is it a new record for the region, but it also highlights how much we still have to learn about deepwater seagrass ecosystems and their role in supporting marine biodiversity in remote parts of the Indian Ocean.”
Marine ecologist Dr. Nicole Esteban added that the team first discovered extensive deepwater seagrass meadows in 2016, guided by satellite tracking of green turtles. These meadows—far deeper than expected—now appear to provide food and shelter for a wide range of marine species, including the newly recorded shark.
Conservation Implications
With sliteye shark populations already under threat, this new record strengthens the argument for:
- Protecting deepwater seagrass habitats in the Indian Ocean.
- Expanding research into the role of sharks in marine ecosystems.
- Prioritizing conservation strategies in remote protected areas like the Chagos Archipelago.
This discovery forms part of a collaborative research project between Swansea University and international partners. The complete findings are expected to be published in 2026.