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.
Ever since I was a little girl I knew I wanted to be a scientist – but I didn’t know what kind. What I did know was that I loved animals, especially ‘cold’ animals – reptiles, amphibians and insects – and that I loved the outdoors. I grew up in the big city of Chicago in the USA, but from the age of six to 20 I spent all my summers at my family’s fishing lodge in the lakes region of north-western Ontario in Canada. There I worked as a waitress, a fishing guide and a house painter and in...
The key objective of this research project is to gain a better understanding of the population numbers, nesting activity and movements of marine turtles that use D’Arros Island and St Joseph Atoll.
Hawksbill and green turtles are listed as Critically Endangered and Endangered, respectively, on the International Union for Conservation of Nature’s (IUCN) Red List and both are experiencing population declines that are driving them to extinction. Research into turtle populations using important nesting habitats provides the critical information needed to support efforts for their conservation.
Sea turtles are found in all oceans except in the polar areas, and the Republic of Seychelles represents a globally important region for nesting. These turtles play an important role in ecosystems as one of their primary food types is sea grass. Sea-grass meadows are a critical habitat for many species and need to be constantly cut short to support growth. Sea turtles grazing on the sea grass helps to keep the meadows healthy.
The key objective of this monitoring programme is met by several specific study objectives:
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.
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.