To supplement much of the research conducted on site (e.g. coral monitoring and reef fish surveys) and to help better understand the lives of the animals using D’Arros Island and St Joseph Atoll, it is important to measure and monitor environmental conditions. One of the most important of these is sea temperature. A series of small loggers deployed at different areas and depths around the islands constantly record the water temperature. Additionally, via our on-site weather station, we collect meteorological data every day, including on wind, rainfall and air temperature.
The key objective of this project is to provide long-term baseline environmental information for other projects, both for historical reference and to monitor potential trends in patterns of local weather that may affect SOSF-DRC research.
Recording and monitoring environmental data can benefit all research projects and help understand how weather and sea conditions impact different species.
Continuous long-term data on the climatic and oceanographic conditions of a region help us to expand our knowledge and understanding of broader weather patterns and changes, both locally around D’Arros and St Joseph and regionally across the wider equatorial Indian Ocean. Long-term environmental data collection is valuable in supporting and corroborating a range of research outcomes for a variety of different study species.
The key objective of this monitoring project is met by several specific study objectives:
D’Arros Island and St Joseph Atoll have been identified as one of the most important areas in Seychelles and the broader Western Indian Ocean for hawksbill Eretmochelys imbricata and green Chelonia mydas turtles, with both species using the beaches for nesting. We continually monitor their presence at the islands, collecting data both from individual animals present on the beaches and from the tracks they leave behind. From these we can estimate the population sizes and growth of these two turtle species.
A large population of reef manta rays Mobula alfredi occupies the near-shore waters of D’Arros Island. Each of these rays has unique markings on its ventral surface (belly) that enable us to identify different individuals. From this we gather information about how many mantas are using the site, where they spend their time and for how long. We use various photograph and video techniques to identify manta rays at D’Arros, including the deployment of cameras at a regularly visited cleaning station. Working with the Manta Trust, we incorporate our data into a broader regional understanding of the population and ecology of these threatened animals in Seychelles.
Across D’Arros Island, St Joseph Atoll and the broader region we have an array of stationary acoustic receivers that are constantly recording information about the presence of individual animals that we have tagged with acoustic transmitters. When a tagged animal moves within its range, the receiver records the ID tag (and thus the animal), date and time. Together as a network, these receivers tell us about the movements and distributions of different animals across different spatial scales. We have a total of 89 receiver stations, and we have tagged many individuals of different species of shark, ray, fish and turtle, so a lot of data is constantly being recorded on these receivers. Our staff download the data from and maintain these receivers every six months.