The Alphonse Shark Project has completed the fieldwork part of its two-year tagging and sampling programme, and the preliminary findings paint a vivid picture of just how vital this corner of the Indian Ocean is for some of the world’s most threatened marine predators.
Led by Island Conservation Society (ICS) and the Alphonse Foundation, in partnership with Blue Safari Seychelles, Save Our Seas Foundation – D’Arros Research Centre, and the University of Western Australia (UWA), the project has spent two years tagging sharks, deploying underwater cameras, and collecting DNA samples across the Alphonse Group, a cluster of remote atolls some 400km south of Mahé. We now have acoustic tracking data from 50 tagged sharks across five species groups, 248,529 individual detections logged across our receiver array, and faecal DNA samples from over 100 sharks currently under analysis.
The data is already showing conservation considerations. Lemon shark residency data has directly supported the 2024 designation of St François lagoon as an Important Sharks and Rays Area (ISRA), wedgefish site fidelity findings are informing conservation management strategies with implications beyond the Seychelles, and spatial hotspot data is allowing protection measures to be targeted with greater precision than has previously been possible in this region. This is what the data is telling us.
Bull sharks: corridors and disappearances
Of the 10 bull sharks tagged, one has provided the most sustained dataset. A69- 62661, known to the team as The Dentist, is a large male tagged in 2024 whose 20 months of detections concentrated consistently around the western edge of Alphonse and the mouth of the Alphonse channel. His data confirms what reef ecologists have long argued: channels and reef passes function as wildlife corridors, concentrating movement and ecological activity in ways that make them critical habitats for multiple species.
Previous tagging studies in the Seychelles have tracked bull sharks moving between Mahé, the Amirante islands, and as far as Madagascar, and The Dentist’s disappearance from the array in July 2025 suggests he is doing the same. Whether he returns, and when, is a question the longer-term dataset will answer. The remaining nine bull sharks were tagged in October–November 2025, giving us three months of data, enough to see patterns emerging, but not yet enough to draw firm conclusions.
Wedgefish: critically endangered and real homebodies
Five Whitespotted Wedgefish (Rhynchobatus australiae)were tagged in November 2025. All five were detected exclusively inside the Alphonse lagoon. Tagged individuals barely moved more than 1–2 kilometres over three months, an extraordinary level of site fidelity that underscores how vulnerable this species is to overfishing in any single location. This is pioneering data, as nothing is currently known about the spatial ecology of wedgefish in atoll environments, and these findings can be incorporated into conservation management strategies for the species, not just in the Seychelles but across other island ecosystems where equivalent studies have not yet been conducted.
Tiger sharks: following the seagrass
Three tiger sharks were tagged during the 2025 season, two in October and one earlier in the year. Unlike every other species in our array, which use the Alphonse channel as their primary corridor between the outer reef and the lagoon, the tiger sharks show a consistently different pattern. Acoustic detections trace a path between an outer reef site known as Bazinga and the lagoon interior, travelling across seagrass meadows dominated by turtle grass, rather than through the channel.
This is ecologically consistent with what other studies have found. Tiger sharks are among the most documented predators of green turtles, and green turtles are dependent on seagrass. The sharks appear to be using the same habitat as their prey. The highest densities of tiger shark detections in our array cluster around Bijoutier and the Alphonse flats, where turtle grass cover is most extensive. Two of the three tiger sharks tagged in October 2025 were still present in the array when data was downloaded in February 2026.
Lemon sharks: permanent residents of the Alphonse Group
The lemon shark dataset is the most complete we have, with animals tagged in 2024 now carrying close to 20 months of detections. Lemon sharks, listed as endangered on the IUCN Red List, appear to be permanent residents: some individuals were detected daily for an entire year, never leaving the atoll group. The lagoons of St François in particular appear to be critical nursery habitat for these animals. This finding directly supports the 2024 designation of the area as an Important Sharks and Rays Area (ISRA), confirming that the protections put in place reflect the biological reality on the water.
The data shows clear habitat boundaries. Grey reef sharks patrolled the steep reef slopes on either side of the Alphonse channel, with some entering the shallow lagoons, but lemon sharks tagged around Alphonse and Bijoutier rarely crossed the deep-water channel between the atolls. The channels at La Passe and Petit La Passe appear to act as a barrier to their movements. These spatial boundaries are precisely the kind of information that allows conservation measures to move beyond broad habitat protection and target the specific areas where animals are most active.
What the data enables
The 248,529 detections across our array allow us to move from broad conservation assumptions to precise, targeted protection. We have now identified the western edge of Alphonse, particularly around receiver stations AA18, AA19 and AA20, and the western side of Bijoutier as high-traffic zones for multiple shark species simultaneously. As the project team has noted: “Every detection we record is another piece of evidence for where protections need to be focused.”
Our faecal DNA samples from over 100 sharks are currently under analysis. Results will give us dietary information across all species, placing each animal within the food web and helping us understand the trophic structure these sharks are maintaining, especially in the face of decreasing marine biodiversity and a changing climate.
Rare sightings and seasonal surprises
The 90 pelagic BRUV deployments completed in October–November 2025 revealed a striking seasonal surge in open-ocean species, with highlights including a Shortfinned Mako Shark, a first recorded sighting for the Alphonse Group, Dusky Sharks (Carcharhinus obscurus) and Silky Sharks (Carcharhinus falciformis), both globally threatened species, Striped Marlin, and a pair of orca. The orca sighting is only the third recorded time these animals have appeared in the Marine Futures Lab BRUV deploymentsat the University of Western Australia, which spans seven ocean basins and thousands of hours of underwater footage.
“The first tentative glimpse into the lives of these sharks through looking at their movements and habitat use both confirms theories we’ve long held such as the use of certain areas as nursery sites but also raises other uestions and concerns. Becoming more involved with shark conservation over the past few years has not been easy as these animals are facing such significant threats from fishing and there’s very few positive news stories out there. At least through the research we are doing we are confirming this little corner of the Indian Ocean can offer some respite for them in an area that is clearly so important- it just now about stregthening policy in Seychelles to ensure they are protected across the whole archipelago.” Elle Brighton.
How you can help
More than 75% of the shark species we encounter in this study are threatened with extinction. There are practical ways to reduce the pressure they face. Sustainable seafood choices matter: opt for pole-and-line caught tuna, which is readily available in supermarkets across Europe and the USA, avoid all seafood caught using bottom trawls, and consider joining campaigns such as Fish-Free February, where you commit to eating no seafood for a month to reduce the pressure placed on sharks and rays.
Blue Safari also runs an adopt-a-shark programme, where you can choose from tracked species, including grey reef, lemon, and silvertip sharks. When you adopt a shark, you get to name it, and in return for your donation, you will receive annual updates showing where your shark has been and what it has been doing over the last 12 months. Sponsorship funds telemetry work, faecal DNA analysis, and the protection of essential habitats for these animals. To support the project or make a donation, please contact Elle at eleanor@bluesafari.com Blue Safari is a registered charity in both the UK and Seychelles.
The full research report, covering all five species groups and the complete acoustic dataset, is available here.
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