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Larue, Seychelles

Phillips K.P.,University of East Anglia | Phillips K.P.,University of Sheffield | Mortimer J.A.,Island Conservation Society | Mortimer J.A.,rros Research Center | And 5 more authors.
Journal of Experimental Marine Biology and Ecology

The concept of 'effective population size' (Ne), which quantifies how quickly a population will lose genetic variability, is one of the most important contributions of theoretical evolutionary biology to practical conservation management. Ne is often much lower than actual population size: how much so depends on key life history and demographic parameters, such as mating systems and population connectivity, that often remain unknown for species of conservation concern. Molecular techniques allow the indirect study of these parameters, as well as the estimation of current and historical Ne. Here, we use genotyping to assess the genetic health of an important population of the critically endangered hawksbill turtle (Eretmochelys imbricata), a slow-to-mature, difficult-to-observe species with a long history of severe overhunting. Our results were surprisingly positive: we found that the study population, located in the Republic of Seychelles, Indian Ocean, has a relatively large Ne, estimated to exceed 1000, and showed no evidence of a recent reduction in Ne (i.e. no genetic bottleneck). Furthermore, molecular inferences suggest the species' mating system is conducive to maintaining a large Ne, with a relatively large and widely distributed male population promoting considerable gene flow amongst nesting sites across the Seychelles area. This may also be reinforced by the movement of females between nesting sites. Our study underlines how molecular techniques can help to inform conservation biology. In this case our results suggest that this important hawksbill population is starting from a relatively strong position as it faces new challenges, such as global climate change. © 2014 Elsevier B.V. Source

Bijoux J.,IRD Montpellier | Bijoux J.,Seychelles Fishing Authority | Bijoux J.,South African Institute For Aquatic Biodiversity | Dagorn L.,IRD Montpellier | And 5 more authors.
Endangered Species Research

The protection of grouper spawning aggregations is a global conservation issue: populations of many grouper species are threatened with collapse due to exploitation of this critical life history behaviour by fisheries. Effective protection of spawning aggregations requires information on spawning site fidelity, residence time and timing of arrivals at, and departures from, the site. To estimate these parameters at a spawning aggregation site at Farquhar Atoll, southern Seychelles, 12 brown-marbled groupers Epinephelus fuscoguttatus and 20 camouflage groupers E. poly phe ka dion were tagged with acoustic transmitters, and their presence and absence was monitored by an array of acoustic receivers positioned at the site over 2 spawning seasons (2010/2011 and 2011/2012). Spawning aggregations formed during 3 consecutive spawning months each season and overlapped spatially and temporally in the 2 species. Intra- and inter-season site fidelity was high, with 91.7% of tagged E. fuscoguttatus and 89.5% of tagged E. polyphekadion detected at the site 1 yr after tagging. The majority (2010/2011: 82.4%, 2011/2012: 80.0%) of fish detected in a spawning season visited the site during at least 2 spawning months. Residence time at the fish spawning aggregation site was influenced by sex (E. fuscoguttatus only) and spawning month (both species). Distinct periodicity in lunar timing of arrivals and departures was observed in both species. This study highlights the spatio-temporal scales involved during spawning aggregations of 2 long-lived, slow-growing coral reef fishes, which need to be considered for their effective management. © Inter-Research 2013. Source

Le Goff G.,IRD Montpellier | Bousses P.,IRD Montpellier | Julienne S.,Ministry of Health | Brengues C.,IRD Montpellier | And 3 more authors.
Parasites and Vectors

Background: During recent periods, the islands of the Republic of Seychelles experienced many diseases such as dengue, chikungunya, Bancrofts filaria and malaria. Mosquitoes transmit the agents that cause these diseases. Published information on mosquitoes in the Seychelles is notably dispersed in the literature. The maximum number of species obtained on a single field survey does not exceed 14 species. Methods. We performed a comprehensive bibliographic review using mosquito and Seychelles as the key words, as well as conducted a mosquito field survey for larval and adult stages during the rainy season in December 2008. Sixteen sites were sampled on four granitic islands (Mahé, Praslin, La Digue and Aride) and six sites on coralline atolls in the extreme southwest of the country (Aldabra group). Results: We found published references to 21 mosquito species identified at least on one occasion in the Seychelles. Our collections comprised 18 species of mosquitoes, all of them from the subfamily Culicinae; no Anophelinae was found. We also confirm that Aedes seychellensis is a junior synonym of Ae. (Aedimorphus) albocephalus. The first records for Culex antennatus and Cx. sunyaniensis are presented from the country, specifically from Aldabra and Praslin, respectively. Based on a comparison of the taxa occurring on the granitic versus coralline islands, only three species, Ae. albocephalus, Cx. scottii and Cx. simpsoni are shared. Aedes albopictus appeared to exclude largely Ae. aegypti on the granitic islands; however, Ae. aegypti was common on Aldabra, where Ae. albopictus has not been recorded. The notable aggressiveness of mosquitoes towards humans on coralline islands was mainly due to two species, the females of which are difficult to distinguish: Ae. fryeri and Ae. (Aedimorphus) sp. A. The number of mosquito species collected at least once in the Seychelles is now 22, among which five species (Ae. (Adm) sp. A, Cx. stellatus, Uranotaenia browni. Ur. nepenthes and Ur. pandani) and one subspecies (Ae. vigilax vansomerenae) are considered as endemic. Two illustrated identification keys, one for adult females and the other for larval stages, are presented. Conclusions: The knowledge of the culicidian fauna in the Seychelles has been notably updated. The number of mosquito species is relatively large with regards to land surface and distances to continental Africa, although the anophelines are totally lacking. The complex natural history of mosquitoes in the Seychelles provides examples of both vicariance- and dispersal-mediated divergences. They present superb examples for theoretical and applied island biology. © 2012 Le Goff et al. Source

Robert V.,IRD Montpellier | Rocamora G.,Island Conservation Society | Julienne S.,Ministry of Health | Goodman S.M.,Field Museum of Natural History
Malaria Journal

Background: Species of anopheline mosquitoes are largely distributed over emerged lands around the world and, within the tropics, few areas are without these insects, which are vectors of malaria parasites. Among the exceptions is the Seychelles archipelago in the western Indian Ocean. However, in the Aldabra island group, located in the extreme western portion of the archipelago, Anopheles gambiae s.l. was introduced, leading to massive proliferation and then elimination, with the most recent autochthonous malaria cases recorded in 1931. Methods. In order to re-examine the absence of anopheline mosquitoes in the Seychelles, an entomological field survey was conducted in December 2008 at 17 sites on four granitic islands, including Mahé and Praslin, and ten sites on coralline atolls in the extreme west, including Aldabra. Results: No evidence of larval or adult anophelines was found at the surveyed sites, which supports their absence in the Seychelles. Conclusions: In the granitic islands of the Seychelles, the climate is favourable for anophelines. However, these islands are protected by their remoteness and prevailing seasonal winds. In addition, stagnant freshwater, required in anopheline larval development, is relatively uncommon on the granitic islands because of the steep slopes. In the southwestern atolls (Aldabra and Providence-Farquhar groups), the presence of a long dry season of up to nine months and the total absence of permanent natural freshwater prevents the breeding of anophelines and their successful colonization. The Seychelles does not have any native land mammals and like in other parts of the world (Antarctica, Iceland, New Caledonia, Central Pacific islands) their absence is associated with the lack of anophelines. This suggests an obligatory relationship for anophelines to feed on terrestrial mammals, without alternative for blood-feeding sources, such as bats, birds and reptiles. © 2011 Robert et al; licensee BioMed Central Ltd. Source

Friedlander A.M.,University of Hawaii at Manoa | Obura D.,Coastal Research and Development in the Indian Ocean CORDIO | Aumeeruddy R.,Island Conservation Society | Ballesteros E.,CSIC - Center for Advanced Studies of Blanes | And 4 more authors.

We report a reef ecosystem where corals may have lost their role as major reef engineering species but fish biomass and assemblage structure is comparable to unfished reefs elsewhere around the world. This scenario is based on an extensive assessment of the coral reefs of Farquhar Atoll, the most southern of the Seychelles Islands. Coral cover and overall benthic community condition at Farquhar was poor, likely due to a combination of limited habitat, localized upwelling, past coral bleaching, and cyclones. Farquhar Atoll harbors a relatively intact reef fish assemblage with very large biomass (3.2 t ha -1) reflecting natural ecological processes that are not influenced by fishing or other local anthropogenic factors. The most striking feature of the reef fish assemblage is the dominance by large groupers, snappers, and jacks with large (>1 m) potato cod (Epinephelus tukula) and marbled grouper (E. polyphekadion ), commonly observed at many locations. Napoleon wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum ) are listed as endangered and vulnerable, respectively, but were frequently encountered at Farquhar. The high abundance and large sizes of parrotfishes at Farquhar also appears to regulate macroalgal abundance and enhance the dominance of crustose corallines, which are a necessary condition for maintenance of healthy reef communities. Overall fish biomass and biomass of large predators at Farquhar are substantially higher than other areas within the Seychelles, and are some of the highest recorded in the Indian Ocean. Remote islands like Farquhar Atoll with low human populations and limited fishing pressure offer ideal opportunities for understanding whether reefs can be resilient from global threats if local threats are minimized. © 2014 Friedlander et al. Source

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