First confirmed whale shark movement between Madagascar and Seychelles revealed

A newly documented 1,200-kilometre journey highlights the need for regional conservation cooperation in the western Indian Ocean

Researchers at Madagascar Whale Shark Project and the Marine Conservation Society Seychelles have confirmed the first documented movement of a whale shark between Madagascar and Seychelles, revealing that endangered whale sharks regularly cross national boundaries in the western Indian Ocean.

Photo-identification analysis confirmed that a juvenile male whale shark first recorded off Nosy Be, Madagascar, in 2019 was resighted off Mahé, Seychelles, in August 2025.

This is the first verified resighting of a whale shark moving from Madagascar to another country in the region, adding rare evidence that whale sharks form a shared, transboundary population. The discovery comes amid declining sightings in Madagascar and increasing sightings in Seychelles, suggesting potential shifts in feeding grounds linked to environmental change and growing threats in the region, such as bycatch from industrial fishing and targeted fishing locally. 

“We’ve been recording whale sharks since 2015 and to see an individual travelling more than 1,200km between Madagascar and Seychelles is astounding. This first-of-its-kind event is what we were waiting for,” says Stella Diamant of the Madagascar Whale Shark Project. “This discovery underscores the importance of long-term monitoring and international collaboration. Without shared photo-identification databases, this movement would have gone unnoticed.”  

Whale sharks are listed as Endangered on the IUCN Red List and face threats including fisheries bycatch, vessel strikes, and climate-driven changes to ocean productivity. While the species has been protected in Seychelles since 2003, it currently lacks formal protection in Madagascar—highlighting the importance of regional cooperation.

“In 2015, MCSS suspended its long-term whale shark monitoring programme due to a marked decline in local sightings. With the species’ reappearance in Seychelles waters in 2023 and the subsequent recommencement of systematic surveys, it is incredibly exciting to document, for the first time, the transboundary movement of a whale shark between Madagascar and Seychelles. This record highlights the significant gaps that remain in our understanding of the spatial ecology and migratory behaviour of the world’s largest fish.” – Christophe Mason-Parker, MCSS

The finding is published today in Oryx.

Miss Diamant is available for interview and comment on this study.