Academic literature on the topic 'D'Arros Island (Seychelles)'

Stable isotope analyses provide the means to examine the trophic role of animals in complex food webs. Here, we used stable isotope analyses to characterize the feeding ecology of reef manta rays ( Mobula alfredi ) at a remote coral reef in the Western Indian Ocean. Muscle samples of M. alfredi were collected from D'Arros Island and St. Joseph Atoll, Republic of Seychelles, in November 2016 and 2017. Prior to analysis, lipid and urea extraction procedures were tested on freeze-dried muscle tissue in order to standardize sample treatment protocols for M. alfredi . The lipid extraction procedure was effective at removing both lipids and urea from samples and should be used in future studies of the trophic ecology of this species. The isotopic signatures of nitrogen (δ 15 N) and carbon (δ 13 C) for M. alfredi differed by year, but did not vary by sex or life stage, suggesting that all individuals occupy the same trophic niche at this coral reef. Furthermore, the isotopic signatures for M. alfredi differed to those for co-occurring planktivorous fish species also sampled at D'Arros Island and St. Joseph Atoll, suggesting that the ecological niche of M. alfredi is unique. Pelagic zooplankton were the main contributor (45%) to the diet of M. alfredi , combined with emergent zooplankton (38%) and mesopelagic prey items (17%). Given the extent of movement that would be required to undertake this foraging strategy, individual M. alfredi are implicated as important vectors of nutrient supply around and to the coral reefs surrounding D'Arros Island and St. Joseph Atoll, particularly where substantial site fidelity is displayed by these large elasmobranchs.

Thesis (DTech. degree in Nature Conservation.)--Tshwane University of Technology, 2010.
Hawksbill sea turtles (Eretmochelys imbricata) have been reduced by more than 80% worldwide in the last century and are considered critically endangered. Although nesting populations have been subject to numerous studies, there is a considerable lack of knowledge pertaining to the in-water behaviour and ecological functions of wild foraging hawksbill populations. This is especially true for the Western Indian Ocean as important topics such as habitat use and dietary items have scarcely been explored. Between 2006 and present, more than 178 hours of in-water observations of foraging hawksbill activity was recorded on a small insular reef at D'Arros Island, Seychelles. Most of the 827 sightings were of known, resident turtles (> 90%), facilitating analyses on both a population and individual level. Habitat types were identified and described, turtle densities estimated, population dynamics established, home ranges calculated, food items identified, food intake quantified, feeding behavior described, food resources quantified, diet selectivity indices calculated, intra/interspecific competition quantified and activity and dive patterns were described.