The sliteye shark (Loxodon macrorhinus) has been observed for the first time in the Chagos Archipelago, according to recent findings from a research team led by Swansea University. The discovery was made in deepwater seagrass meadows on the southern rim of the Great Chagos Bank, highlighting new biodiversity within the region’s Marine Protected Area.
Researchers used Baited Remote Underwater Video (BRUV) systems to record the sharks at depths between 23 and 29 metres. These sightings occurred just 11 kilometres apart and mark a significant addition to knowledge about marine life inhabiting previously unstudied seagrass habitats. These habitats were first identified by the team in 2016.
Charlotte Oulton, study lead and Master’s by Research student in the Marine and Conservation Ecology Lab at Swansea University, stated: “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, particularly in remote regions of the Indian Ocean.”
Dr Nicole Esteban, Associate Professor in Marine Ecology at Swansea University, said: “Satellite tracking of green turtles led us to discover extensive seagrass meadows on the Great Chagos Bank at depths of 25–30 metres—far deeper than expected. We have now recorded a wide diversity of marine life using this seagrass habitat for shelter and food, including over 110 fish species, and as we now know, the sliteye shark.”
The researchers note that while sliteye sharks are widely distributed across their range, populations could decline by up to 29 percent over the next 15 years due to fishing pressures. This discovery raises questions regarding abundance and habitat use for this species as well as conservation priorities related to deepwater environments.
The surveys took place in late 2024 as part of an international collaboration involving Swansea University and other partners. Funding was provided by the Bertarelli Foundation through its Indian Ocean Marine Science Programme. The project seeks to map current seagrass coverage across the archipelago, model habitat suitability for predicting future growth areas, and assess ecological importance of these deepwater ecosystems.