On 3 December 2025, the Madagascar Whale Shark Project and Marine Conservation Society Seychelles documented the first confirmed movement of an Endangered whale shark Rhincodon typus between Madagascar and Seychelles. The record was established through a collaborative comparison of photo-identification databases, providing information for regional whale shark management in the western Indian Ocean.

Since 2015, the Madagascar Whale Shark Project has identified 545 individual juvenile whale sharks around Nosy Be, north-west Madagascar, through long-term photo-identification involving Malagasy students, tourism operators and citizen scientists. However, sightings in Nosy Be declined from 147 individuals in 2019 to 39 in 2025. The Marine Conservation Society Seychelles recorded an increase in whale shark sightings in the Seychelles during 2022–2025, reversing a decline in its estimated population size from 348–488 in 2007 to just 33 in 2014. These contrasting trends prompted renewed photo-identification comparisons.

In November 2025, the Marine Conservation Society Seychelles shared 20 identification photographs from 2025. Using the semi-automated software I3S, these images were matched against the complete Madagascar whale shark catalogue by the Madagascar Whale Shark Project team. Both organizations confirmed that one shark—MD-393 (Mistral), first recorded on 26 November 2019 as a 4.5 m long male feeding off Nosy Be, Madagascar—was subsequently photographed off Mahé, Seychelles, on 29 August 2025, where it was estimated to be 6 m in length. This is the first resighting of a whale shark from Madagascar in another western Indian Ocean country.

The estimated 1,200 km movement of Mistral adds to the limited number of confirmed multi-country resightings in the region, previously documented only between Mozambique and Seychelles in 2010, and between Mozambique and Tanzania in 2018. Such cases remain rare and highlight the need for coordinated photo-identification and data sharing across national boundaries.

Although many whale sharks show strong seasonal fidelity to Nosy Be, long-distance movements are known to occur. Earlier satellite tagging studies revealed that individuals using Madagascar’s western coastal waters can travel several thousand kilometres, moving along the coastline before returning in subsequent years. The newly confirmed movement between Madagascar and Seychelles supports the hypothesis that juvenile whale sharks may migrate between feeding grounds, depending on prey availability.

Whale sharks face multiple threats across the region, including bycatch in tuna fisheries, vessel strikes and climate-change-driven shifts in oceanographic conditions. Although the whale shark is protected in Seychelles since 2003, Madagascar currently lacks formal protection for the species. This confirmed transboundary resighting underlines the urgency of regional cooperation. The Madagascar Whale Shark Project and Marine Conservation Society Seychelles will continue to share photo-identification data, to improve our understanding of whale shark movements and the emerging shifts in regional distribution. Both organizations plan to expand satellite tagging and acoustic telemetry studies.