By Christophe Mason-Parker & Stella Diamant, 5th March 2026
Whale sharks Rhincodon typus are the largest extant fish species, but despite their impressive size, reaching lengths of over 18 metres, they remain amongst the least understood marine megafauna. These filter‑feeding sharks inhabit warm tropical and subtropical waters, where they aggregate seasonally in response to plankton blooms and other predictable food sources. Each individual carries a unique pattern of spots and stripes that can be used as a biometric identifier, enabling researchers to track movements and population trends through photo‑identification. Although generally slow‑moving, whale sharks undertake extensive migrations that can span thousands of kilometres, linking distant ecosystems across ocean basins. Classified as Endangered on the IUCN Red List, the species faces mounting pressures from fisheries bycatch, vessel strikes and climate‑driven shifts in productivity. Understanding their spatial ecology and movement patterns is critical for designing effective conservation strategies in an increasingly fluctuating ocean environment.
Left: Nosy Be view (photo: Rémi Conte). Right: Map of the distance covered (hypothetical track; photo: MWSP).
Whale shark, left ID in Madagascar. Photo: Stella Diamant.
The Marine Conservation Society Seychelles (MCSS) is an environmental NGO registered in Seychelles in 1997. Since its inception, the whale shark has been the flagship species of the Society and featured on its logo. In 2002, the MCSS developed an aerial and boat-based operation to combine ecotourism and vital conservation work for these little-understood giants. A research vessel offered opportunities for tourists to snorkel in the vicinity of whale sharks, under strictly controlled conditions to ensure the animals would not be unduly disturbed, and participate in citizen science by collecting identification photographs as part of a long-term monitoring programme. This has enabled the Society to conduct research, improve public awareness of whale sharks and finance its operations, without depending on unpredictable and often sporadic donor funding. The success of this programme provided the justification for the designation of the species as Protected in Seychelles in 2003. It continued until 2014, when declining sightings around Mahé forced operations to pause. However, an unexpected resurgence of whale shark observations in 2023 prompted the MCSS to relaunch its monitoring efforts.
The 2025 teams of the Madagascar Whale Shark Project (MWSP; top) and Marine Conservation Society Seychelles (MCSS; bottom).
MWSP boat. Photo: Alizée Guimbaud.
Across the Mozambique Channel, since 2015, the Madagascar Whale Shark Project (MWSP) has been developing a comprehensive whale shark photo‑identification catalogue. To this day, the MWSP is still the only project dedicated to whale sharks or any elasmobranch species in Madagascar. Thanks to collaborative efforts with local tourism operators, the Project has established itself in Nosy Be, north-west Madagascar, where it uses scientific data to guide the development of tourism and the establishment of protection measures for whale sharks and other marine megafauna. Through citizen science and dedicated local scientists, the Project collects standardized data on each encountered shark—including GPS location, estimated size and sex—which are paired with high‑quality identification photographs. Its primary goal is to understand occurrence patterns, residency and population structure in Malagasy waters. Thanks to its dedicated efforts across eight seasons, the MWSP has identified 546 whale sharks, all juvenile males. Yet since the Covid-19 pandemic, the number of sighted whale sharks has declined rapidly in the Nosy Be archipelago, west side, from 140 in 2019 to only 38 in 2025.
Left: Whale shark in Madagascar. Right: Volunteer takes a Photo ID in Madagascar. Photos: Stella Diamant.
Whale Shark from above in Madagascar. Photo: Stella Diamant.
Given the geographical proximity of the Seychelles and Madagascar, and the fluctuating population trends from both aggregations, researchers from both organizations began to wonder whether they might be documenting the same individuals. Whale sharks are known for their long‑distance movements, but no confirmed connection had ever been established between the two island nations. This shared curiosity led MCSS and MWSP to exchange photo‑identification images, opening the door to a new level of regional collaboration.
Stella Diamant and whale shark Hugo. Photo: Anthony Colas.
Then, on 3 December 2025, a remarkable observation was made. For the first time, following the comparison of photos, the MWSP and the MCSS confirmed the movement of a recognized individual whale shark between Madagascar and Seychelles. The shark, nicknamed ‘Mistral’, had travelled an estimated distance of 1,200 km across open ocean, appearing along Mahé’s coastline 6 years after he was first sighted near Nosy Be, Madagascar. Mistral’s journey adds a crucial new piece to the puzzle of whale shark movements in the western Indian Ocean and confirms what researchers had long suspected but never yet proven: these sharks are not just residents of one nation’s waters; they are regional travellers, responding to ecological cues that we are only just beginning to understand. Moreover, it is a reminder that even a single animal can reshape our understanding of an entire region. This exciting discovery highlights the importance of long-term monitoring, citizen science and cross‑border collaboration for the conservation of wide-ranging species such as the iconic whale shark.
Mistral. Photo: MWSP.
The Conservation News item ‘First documented movement of a whale shark between Madagascar and Seychelles’ is available open access in Oryx—The International Journal of Conservation.
A pair of whale sharks near the Mahé coast, Seychelles. Photo: MCSS.
