In the end it all comes down to poop
Integrated into two long-term mark-recapture studies of sharks, this study uses recently developed methods to investigate juvenile shark diets. Cloacal swabbing offers a rapid and minimally invasive means to gather dietary information and builds on previous diet research at the site to assess its viability. Collected faecal DNA data will be used to reveal the precise diet composition of juvenile blacktip reef sharks (Carcharhinus melanopterus) and sicklefin lemon sharks (Negaprion acutidens) using St Joseph atoll as a critical nursery habitat and allow us to understand how these juvenile sharks interact and share or partition resources. Samples will be collected from 200 individuals over several seasons and across a range of sub-habitats at the St Joseph site.
Ellie Moulinie
I am a young Seychellois who is very passionate about animals and the ocean. Growing up in a family of fishermen, my school holidays were always spent by the sea. My brother would sometimes take me snorkelling over the reef and I still remember being in awe of the vastness of the open ocean. Despite this, it was not until I went to university and started diving that I knew I wanted to study marine science.
Diet assessment of two reef associated shark species at a remote tropical nursery site in the Indian Ocean
Reconstruct the precise diet composition of two sympatric shark species populations: blacktip reef shark and sicklefin lemon shark, in and around the St Joseph atoll through collection of faecal DNA (fDNA). We aim to gain insights into differences in feeding and trophic ecology of these two shark species and identify ontogenetic shifts in their diets over time.
Sharks play crucial roles in our oceans, maintaining health and stability by occupying various predatory roles in the food-chain, yet relatively little is still known about what they are eating. Revealing the precise diet composition of threatened shark species whose feeding behaviour is difficult to observe in the wild can provide intrinsic information on their feeding ecology and trophic roles in an ecosystem. Juvenile shark diet information can also help reveal mechanistic processes behind shark community dynamics during the early stages of their lives. Further, identifying ontogenetic shifts in diet is essential in understanding animal movement and site fidelity of species on a larger spatio-temporal scale. Diet sampling of sharks has typically been invasive, therefore testing the viability and sensitivity of new and less invasive techniques, such as those used here, is important in driving ethically responsible research. Finally, understanding the ecological requirements of these two threatened species paired with an understanding of changing environmental conditions over space and time can help conservation managers better protect nursery areas for the survival of juvenile reef shark populations in the Western Indian Ocean.
St Joseph Atoll is a closed remote coral reef atoll system located in the Amirantes group of the Seychelles archipelago and was declared a Zone 2 sustainable use area in 2020 under the Seychelles Marine Spatial plan initiative. Surrounded by a protected ring of coral, the St Joseph atoll provides an important nursery habitat to juveniles of threatened species and was recently declared an important shark and ray area (ISRA) in 2023. Its closed system, lack of major anthropogenic stressors and abundance of wildlife makes St Joseph atoll the perfect place to work with sharks at different life stages living in close proximity to one another. This research aims to build on existing shark diet data previously collected in St Joseph atoll and further contribute to bridging the knowledge gap on reef shark feeding ecology in the Western Indian Ocean. Additionally, we will update the current knowledge of marine species that occupy the critical sanctuary of the St Joseph Atoll.
- Establish an accurate understanding of diet composition of two sympatric shark species; Blacktip reef shark (Carcharhinus melanopterus) and Sicklefin lemon shark (Negaprion acutides) that use St Joseph atoll as a tropical nursery through the collection and analysis of feacal DNA (fDNA).
- Identify ontogenetic shifts in shark diet across species particularly between lagoon restricted juveniles and reef associated adults.
- Gain valuable insight into the trophic ecology of two focal shark species by better understanding their coexistence and resource partitioning in the St Joseph atoll.
- Identifying knowledge gaps and using new research methods to inform conservation on the importance of St Joseph atoll as a productive tropical nursery area for juvenile sharks in the broader Western Indian Ocean.
- Understand processes that drive species to adapt to their specific ecology and behaviour in isolation will allow us to protect distinct populations and their associated habitats.