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Letteratura scientifica selezionata sul tema "Fishes – Tristan da Cunha"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 18 febbraio 2022

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Articoli di riviste sul tema "Fishes – Tristan da Cunha"

ANDERSON, M. E., D. L. STEIN e H. W. DETRICH. "Additions to the ichthyofauna of the Tristan da Cunha Group, South Atlantic Ocean". Zootaxa 1072, n. 1 (28 ottobre 2005): 27. http://dx.doi.org/10.11646/zootaxa.1072.1.2.

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Specimens of two, possibly three, rare species of fishes were collected at the Tristan da Cunha Group toward the end of a 2004 South Atlantic cruise (ICEFISH). The dragonet Synchiropus valdiviae (Trunov, 1981), was previously known from only two adult males taken on Walvis Ridge. We collected two adult females and three juveniles, which are described here. The pearlfish Echiodon atopus Anderson, 2005, was recently described from a specimen collected north of Inaccessible Island. It differs from congeners in its high precaudal vertebral count, equivalent dorsal and anal rays anterior to vertebra 31 and other features of the axial skeleton and fins. Lastly, an unusual specimen of the rockfish genus Sebastes taken in a commercial lobster pot represents either a previously unreported variant of S. capensis or an undescribed species. It differs from the typical South Atlantic S. capensis in its coloration and lack of supraocular spines.

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Entwistle, N. "Tristan da Cunha". British Dental Journal 196, n. 3 (febbraio 2004): 125–26. http://dx.doi.org/10.1038/sj.bdj.4810972.

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Freshwater, D. Wilson, Sue Scott, Enrico M. Tronchin e Gary W. Saunders. "Reassessment of Tristan da Cunha Gelidium (Gelidiales, Rhodophyta) species". Botanica Marina 63, n. 5 (25 ottobre 2020): 455–62. http://dx.doi.org/10.1515/bot-2020-0036.

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AbstractThree endemic species of Gelidium have been described from the remote Tristan da Cunha archipelago. A recent barcode survey of Tristan da Cunha red algae in combination with the clarification of vouchers for previously sequenced specimens has prompted a molecular and morphological reassessment of these species. Analyses of rbcL and COI-5P data indicated that all sequenced Tristan da Cunha specimens represented a single taxon, and furthermore that this genetic group was conspecific with Gelidium micropterum from southern Africa. Morphologically the Tristan da Cunha specimens represented either Gelidium concinnum or Gelidium regulare, and there was a grade of character states between both of these species, as well as G. micropterum. Based on these results the synonymy of G. concinnum and G. regulare under G. micropterum is proposed and an expanded description of G. micropterum provided. None of the studied Tristan da Cunha specimens clearly fit the description of the third endemic species, Gelidium inflexum, and its status could not be determined.

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Woodworth, PL. "Wave setup at Tristan da Cunha". African Journal of Marine Science 42, n. 2 (2 aprile 2020): 233–45. http://dx.doi.org/10.2989/1814232x.2020.1776390.

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Bourne, W. R. P. "Oil pollution at Tristan da cunha". Marine Pollution Bulletin 18, n. 3 (marzo 1987): 100–101. http://dx.doi.org/10.1016/0025-326x(87)90114-7.

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Hänel, Christine, e John Irish. "Introduced Fishmoths identified from South Atlantic Tristan da Cunha Island (Thysanura: Lepismatidae)." Beiträge zur Entomologie = Contributions to Entomology 59, n. 2 (15 dicembre 2009): 527–33. http://dx.doi.org/10.21248/contrib.entomol.59.2.527-533.

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Zwei weltweit verbreitete Lepismatidae-Arten, die auf der Süd-Atlantischen Insel von Tristan da Cunha gesammelt wurden, sind identifiziert. Damit wird bestätigt das Vertreter der Ordnung Thysanura (Borstenschwänze) dorthin eingeschleppt worden sind. In der Fauna des Archipels Tristan da Cunhas und anderer, weiter südlich liegenden Inseln, sind einheimische Thysanura-Arten nicht bekannt. Im Gegensatz hierzu existieren einige Arten auf den Inseln St. Helena und Ascension. Deren geographische Lage sowie deren politische und soziale Verbindungen zu Tristan da Cunha stehen mit der Ausbreitung im Zusammenhang. Borstenschwänze werden hauptsächlich durch den Handel verbreitet. Im Falle von Tristan da Cunha verstärkt der zunehmende Tourismus die Einschleppung. Um weitere Probleme durch Import fremder Arten zu verhindern, wird der Aufbau eines Quarantänesystems vorgeschlagen, dass für den ankommenden Schiffsverkehr zuständig sein sollte.StichwörterThysanura, Lepismatidae, Lepisma, Ctenolepisma, Fishmoth, Silverfish, Tristan da Cunha, Gough Island, South Atlantic, introduction.

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ROBSON, BRAD, TREVOR GLASS, NORMAN GLASS, JAMES GLASS, JERRY GREEN, CLIFTON REPETTO, GRAHAM RODGERS et al. "Revised population estimate and trends for the Endangered Northern Rockhopper Penguin Eudyptes moseleyi at Tristan da Cunha". Bird Conservation International 21, n. 4 (6 maggio 2011): 454–59. http://dx.doi.org/10.1017/s0959270911000013.

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AbstractAround 80% of the world population of Northern Rockhopper Penguin Eudyptes moseleyi is found at Tristan da Cunha and Gough Island in the South Atlantic Ocean, where populations appear to be declining. However, numbers of birds at Middle Island, a small satellite island of Nightingale Island at Tristan Cunha, have not been counted since 1973 when an estimated 100,000 pairs were recorded. Updated population counts were obtained for all four islands at Tristan da Cunha (Tristan, Inaccessible, Nightingale and Middle islands) in 2009 providing a census of the whole island group and the first repeat count of Middle Island. Estimated breeding numbers at these four islands were Tristan 6,700 pairs, Inaccessible 54,000 pairs, Nightingale 25,000 pairs and 83,000 pairs at Middle Island. These counts confirm that Tristan da Cunha is a vitally important site for this ?Endangered? species holding over 65% of the global population and that breeding number have been relatively stable over the last 30 years.

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Rocha Júnior, Eduardo R. V., Leila Soares Marques, Fábio Braz Machado e Antonio José Ranalli Nardy. "The Headless Tristan da Cunha Mantle Plume". Revista Brasileira de Geociências 37, n. 4S (1 maggio 2013): 1–8. http://dx.doi.org/10.25249/0375-7536.200737m492110.

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Steinfurth, A., S. Oppel, MP Dias, T. Starnes, EJ Pearmain, BJ Dilley, D. Davies et al. "Important marine areas for the conservation of northern rockhopper penguins within the Tristan da Cunha Exclusive Economic Zone". Endangered Species Research 43 (3 dicembre 2020): 409–20. http://dx.doi.org/10.3354/esr01076.

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The designation of Marine Protected Areas has become an important approach to conserving marine ecosystems that relies on robust information on the spatial distribution of biodiversity. We used GPS tracking data to identify marine Important Bird and Biodiversity Areas (IBAs) for the Endangered northern rockhopper penguin Eudyptes moseleyi within the Exclusive Economic Zone (EEZ) of Tristan da Cunha in the South Atlantic. Penguins were tracked throughout their breeding season from 3 of the 4 main islands in the Tristan da Cunha group. Foraging trips remained largely within the EEZ, with the exception of those from Gough Island during the incubation stage. We found substantial variability in trip duration and foraging range among breeding stages and islands, consistent use of areas among years and spatial segregation of the areas used by neighbouring islands. For colonies with no or insufficient tracking data, we defined marine IBAs based on the mean maximum foraging range and merged the areas identified to propose IBAs around the Tristan da Cunha archipelago and Gough Island. The 2 proposed marine IBAs encompass 2% of Tristan da Cunha’s EEZ, and are used by all northern rockhopper penguins breeding in the Tristan da Cunha group, representing ~90% of the global population. Currently, one of the main threats to northern rockhopper penguins within the Tristan da Cunha EEZ is marine pollution from shipping, and the risk of this would be reduced by declaring waters within 50 nautical miles of the coast as ‘areas to be avoided’.

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Hänel, Christine, e Adrian C. Pont. "Houseflies of the Tristan da Cunha Islands: new records, including the first for Fannia albitarsis Stein, 1911 (Diptera: Fanniidae, Muscidae)." Beiträge zur Entomologie = Contributions to Entomology 58, n. 1 (15 luglio 2008): 211–22. http://dx.doi.org/10.21248/contrib.entomol.58.1.211-222.

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In der Arbeit werden historische und aktuelle Funde von Hausfliegen der Familien Fanniidae und Muscidae auf den Inseln der Tristan da Cunha-Gruppe im Südatlantik zusammengefaßt und diskutiert. Das aktuelle Material wurde 2005 auf den nördlichen Inseln, Tristan da Cunha und Nightingale, gesammelt. Insgesamt sind fünf Arten in vier Gattungen nachgewiesen, einschließlich der Erstnachweise von Fannia albitarsis Stein, 1911 innerhalb des Archipels und von Muscina stabulans (Fallén, 1817) auf der Insel Nightingale. Die korrekte taxonomische Einordnung von Coenosia trina Wiedemann, 1830 wird diskutiert. Auf die offensichtlich starke Verbreitung dieser Art und den möglichen negativen Einfluss auf die heimische Fauna wird ebenfalls hingewiesen.StichwörterDiptera, Muscidae, Fanniidae, Housefly, Lesser Housefly, Stable fly, Tristan da Cunha, Nightingale, Gough, Inaccessible, Island, South Atlantic.

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Più fonti

Tesi sul tema "Fishes – Tristan da Cunha"

Glass, James Patrick. "The fishery and biology of the rock lobster Jasus tristani at the Tristan da Cunha Islands group". Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/2033.

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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Oceanography in the Faculty of Applied Sciences at the Cape Peninsula University of Technology 2014
The Tristan lobster Jasus tristani is distributed among several isolated islands and submerged seamounts in the South East Atlantic Ocean. This species occurs only at the Tristan da Cunha group, a British Overseas Territory and the World’s most remote inhabited island, and in international waters at Vema Seamount 1680 km ENE of Tristan. All these populations are exploited commercially. The catch, processing and export of J. tristani is the most important economic activity for the inhabitants of Tristan da Cunha, providing the livelihood of many families and accounting for approximately 80% of the Island’s revenue. Sustainable harvesting of this valuable resource requires accurate long-term data on catch and effort, as well as information on the most important biological parameters such as growth, recruitment, moulting and reproductive cycles. This information is critical for robust assessments and management strategies. This thesis describes the history of the lobster fishery at the Tristan da Cunha island group, reporting on catches and trends in Catch Per Unit Effort between 1967 and 2010. A total of 247,014 lobster samples, both sexes combined, was sampled for size composition and sex ratios, as well as 1,526 lobsters for length/weight relationships, between 1997 and 2010. This confirms earlier findings that females have broader and heavier tails than males for the same carapace length (CL). Results show that males dominate catches at all islands, and their average size was larger than that of females (83.5 ± 14.46 versus 73.4 ± 8.64 mm CL, respectively). Inter-island differences in lobster population structure appear to be caused by differences of food availability as well as in density-dependent growth and survival of young lobsters. The largest lobsters were found at Gough Island (87.2 ± 15.13 mm CL), and the smallest at Inaccessible island (73.2 ± 11.39 mm). Tristan was the next largest to Gough Island (84.0 ± 12.56 mm) followed by Nightingale island (78.2 ± 11.33 mm). Lobsters caught inshore were larger than those caught offshore, although this may be related in part to differences in catches between fishing gear types. This study showed that fecundity increases in a linear manner with CL, and although larger lobsters clearly produce more eggs than smaller ones, the gain in fecundity is not as great as in some lobster species where fecundity is more closely associated with weight. The study showed no significant differences in egg size between islands, or between large and small females at one island. The egg production per gram of body weight and mean egg diameter both seem to be less than reported in an earlier study in the 1990s. While it seems likely that this is due to differences in the way in which samples were collected (with only stage 2 ova collected and measured in this study), the possibility of a decline in fecundity needs to be investigated further. A range of management measures have been developed over the history of the fishery, and important current measures include an annual total allowable catch (TAC) for each island, minimum size limits, and a closed season timed to protect egg-bearing females. The fishery has recently been awarded certification by the Marine Stewardship Council. The study has confirmed that current conversion factors are broadly correct and that different size limits established for each island are justified. Concern is raised, however, by the fall in catch per unit effort and the mean size of lobsters at the three northern islands over the past 7 years. These trends will need to be closely monitored. There are still many uncertainties over key parameters such as growth and recruitment and the intention is to increase the knowledge base and our understanding of the dynamics of the lobster stock. A research plan has been developed, so that progress can be monitored through the gradual implementation of scientifically defendable fisheries management procedures and increased research and monitoring capacity.

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Andrew, Tim. "The fishes of Tristan Da Cunha and Gough Island (South Atlantic), and the effects of environmental seasonality on the biology of selected species". Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005128.

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This study focuses on the taxonomy, biogeography and biological aspects of the fishes of Tristan da Cunha and Gough Island in the cental South Atlantic Ocean. Oceanographic measurements were undertaken to determine the position and nature of the Subtropical Convergence (STC) in the vicinity of the islands. The Tristan da Cunha group is thought to be situated on the northern edge of the STC while Gough Island is situated on the southern edge of the front. The seasonal environmental cycle at the islands is characterised by an annual sea surface temperature fluctuation of approximately 5 °C and an annual change in stratification of the water column. It is suggested that this increase in stratification at the STC, brought about in the summer by insolation warming the surface layers of the ocean, enhances primary production. The STC is identified as a unique habitat for fishes and as an important barrier to dispersal of species in the Southern Ocean. The present study has produced 18 new distributional records from the shelf waters of Tristan da Cunha and Gough Island. The fish fauna known from the shelf waters of these islands is reviewed, and a diagnosis, synonymy, and in some cases an illustration are provided. For certain species, brief notes on their biology, relative abundance and seasonal distribution are included. An analysis of the ichthyofaunal relationships between shallow water areas in the vicinity of the STC has resulted in the identification of a characteristic neritic STC ichthyofauna. The circumglobal distribution of many of these species is thought to be a consequence of a dispersive pelagic phase in their life-cycles. Biological processes in fishes at these islands are temporally and spatially affected by seasonal changes in oceanographic conditions. Seasonal sea temperature variation was identified as being an indicator of other oceanographic phenomena that may affect processes such as growth, reproduction and feeding in fishes at the islands. Most species have a summer spawning season and growth rate increased during the summer months. It was hypothesised that enhanced primary production and a related increase in food quality and availability during the summer were the major factors temporally regulating the growth and reproduction of fishes at the islands. Twenty families of neritic fishes have been recorded in the shelf waters of Tristan da Cunha and Gough Island. Most families are represented by only one species. Because of this a wide range of life-history strategies are apparent in the fauna. Nevertheless, there are a number of common life-history characteristics shared by most of the neritic species. Firstly, the early lifehistory of many species included an extended pelagic phase which might have facilitated colonisation throughout the STC zone in the past, thereby regulating extant species diversity in this region. Secondly, the common occurrence of an extended summer breeding season and iteroparity suggested that these characters also contributed to survival in what is considered to be an unpredictable environment. It would appear that these common characteristics hold the key to the success of many fishes in the STC zone. This study has contributed to our understanding of oceanic island ecosystems and has revealed distributional patterns of fishes that were unknown previously. By focusing on the biological processes of selected species the regulatory role played by local environmental conditions became apparent. The results of this study are also relevant to proposed conservation measures for Tristan da Cunha and Gough Island.

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Booth, Jenny Marie. "Trophic ecology of breeding northern rockhopper penguins, Eudyptes Moseleyi, at Tristan da Cunha, South Atlantic Ocean". Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005476.

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Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.

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Rousset, Thierry Jean-Marie. "Island bodies: registers of race and 'Englishness' on Tristan da Cunha c.1811 - c.1940". Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26951.

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Tristan da Cunha, a small island in the South Atlantic, is perhaps best known today as the remotest inhabited island in the world. Historical scholarship relating to the island has either focused on its supposed insularity, or has completely elided it in the broader thematic and theoretical studies that often dominate scholarship of the Atlantic world. By placing Tristan da Cunha and metropolitan Britain together within the same analytic field and using an interdisciplinary approach, this work traces metropolitan representations of the island from c.1811-c.1940. Part One traces the ways in which Tristan da Cunha was drawn into the European geographic imagination as well as the economic networks and channels of global circulation during the era of mercantile capitalism. This process saw the island framed as a Romantic English rural idyll displaced into the South Atlantic, and resulted in a metonymic linkage being created between the island body and the bodies that inhabited it. The shift from mercantile capitalism to industrial capitalism and the rise of modernity in the metropole led to (re)negotiations regarding who formed part of the social body of the metropole and Part Two traces the impact of this shift on the island body(ies) of Tristan da Cunha. The (re)negotiation and (re)constitution of the island body(ies) as a result of new metropolitan optics and debates regarding race, degeneration, social belonging, and bourgeois norms resulted in the increasing nativisation and concurrent racialisation of the islanders in metropolitan representations. The island bodies became both coloniser and colonised, Briton and nativised other, Anglo-Saxon and racialised other. These discourses - the island as Romantic English rural idyll, or as isolated, degenerating and inhabited by nativised others - would coexist from the turn of the nineteenth century. They sometimes cut across one another, at other times they reinforced one another, only to diverge and then cut across one another once again. This work unpacks the polyphonic and often contradictory registers of race and Englishness in these metropolitan representations. At the same time it unsettles and attempts to reconstitute the dominant lenses through which the island has previously been analysed.

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Hicks, Anna. "An interdisciplinary approach to volcanic risk reduction under conditions of uncertainty : a case study of Tristan da Cunha". Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/39139/.

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Schlömer, Antje [Verfasser], Wilfried [Akademischer Betreuer] [Gutachter] Jokat e Wolfgang [Gutachter] Bach. "Tristan da Cunha hotspot : Mantle plume or shallow plate tectonics? / Antje Schlömer ; Gutachter: Wilfried Jokat, Wolfgang Bach ; Betreuer: Wilfried Jokat". Bremen : Staats- und Universitätsbibliothek Bremen, 2016. http://d-nb.info/1124975764/34.

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Machado, Pessanha Ivo Bruno. "Évolution Temporelle et Spatiale du Système d'Interaction entre le point chaud de Tristan da Cunha et la Dorsale de l'Atlantique Sud". Phd thesis, Université de Bretagne occidentale - Brest, 2011. http://tel.archives-ouvertes.fr/tel-00652905.

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Dans ce travail nous avons abordé l'évolution spatiale et temporelle du système d'interaction entre le point chaud de Tristan da Cunha et la dorsale de l'Atlantique Sud. Le point chaud de Tristan da Cunha et les structures associées du fond océanique (à savoir la chaîne volcanique de Walvis dans la plaque africaine et l'élévation du Rio Grande dans la plaque sud-américaine) sont parmi les plus importantes de l'océan l'Atlantique Sud. Cependant, ce système est moins étudié que les systèmes présents dans l'Atlantique Nord (par exemple Açores et Islande), et leur origine et évolution restent sujets à débat. La compilation des données de sondage bathymétrique hébergées auprès du Centre National de Données Géophysique (National Geophysical Data Center - NGDC), et les données de bathymétrie dérivées de l'altimétrie de satellites furent utilisées pour l'élaboration d'un modèle numérique de terrain (MNT) de l'ensemble de l'Atlantique Sud. Les données d'anomalie à l'air libre dérivées de l'altimétrie de satellites et les données d'épaisseurs sédimentaires furent utilisées pour le calcul de l'anomalie de Bouguer réduite au manteau (Mantle Bouguer Anomaly - MBA) et avec les données des isochrones du fond océanique furent calculées l'anomalie résiduelle de Bouguer réduite au manteau (Residual Mantle Bouguer Anomaly - RMBA), la bathymétrie résiduelle et des nouveaux pôles du mouvement relatif entre les plaques de l'Amérique du Sud et Afrique. Les données de géoïde dérivées de l'altimétrie de satellites et le Modèle Gravitationnel de la Terre (Earth Gravitational Model - EGM2008) furent utilisés pour la séparation des différentes composantes dans le signal du géoïde, grâce à des filtres retenant différents ordres et degrés d'harmoniques sphériques. À partir des reconstructions cinématiques basées sur les nouveaux pôles calculés dans ce travail, et en se basant surl'hypothèse communément admise que l'île volcanique de Tristan da Cunha se situe à l'aplomb dela position actuelle du point chaud, la chronologie des phases de mise en place des structures volcaniques a pu être précisée. Ceci a mis en évidence l'existence de plusieurs sauts d'axes et des variations périodiques de l'apport magmatique à l'axe entrainant une alternance entre périodes de construction et de rupture du plateau axial. La comparaison détaillée de la position estimée pour le point chaud de Tristan da Cunha et de la localisation des structures volcaniques de la chaine Walvis dont les âges sont connus a souligné que la formation de la chaîne Walvis ne peut pas être expliquée dans sa totalité par un modèle d'évolution faisant appel à une interaction entre la dorsale de l'Atlantique Sud et un point chaud dont la position actuelle serait l'île de Tristan da Cunha. Ensuite, nous avons évalué l'évolution temporelle de l'influence du point chaud à l'axe de la dorsale, sur aux variations de la bathymétrie résiduelle (BR) et de l'anomalie résiduelle de Bouguer réduite au manteau (RMBA), et avec l'analyse des variations du taux d'ouverture et de la distance point chaud-dorsale. Les valeurs des anomalies de RMBA et BR, lors des premières étapes d'ouverture de l'Atlantique Sud, sont plus fortes sur la plaque africaine que sur la plaque sud-américaine. Cela suggère que la position du point chaud a été sous la plaque africaine depuis le début de l'ouverture. En synthèse, on observe trois différentes périodes dans le système d'interaction entre le point chaud de Tristan da Cunha et la dorsale de l'Atlantique Sud. Une période de rapprochement de la dorsale vers le point chaud entre 115 Ma et 100 Ma, lors de laquelle on remarque l'influence du point chaud sur la dorsale sur une distance d'au moins 150 km. Ensuite, entre 95 Ma et 60 Ma, on observe que la dorsale est à l'aplomb ou très proche (< 50 km) du point chaud. Et depuis 60 Ma, un éloignement graduel et progressif de la dorsale par rapport à la position du point chaud est observé. On a pu montrer que lors des périodes de rapprochement et de proximité de la dorsale au point chaud, les variations périodiques d'apport magmatique observées sont liées aux variations du flux de panache. A partir de l'analyse de l'évolution des structures volcaniques, en association avec les données d'anomalie à l'air libre et de géochimie, les structures volcaniques ont pu être divisées en deux groupes. Un groupe formé par la bordure nord-ouest de la chaîne Walvis et appelé première phase, cohérent avec l'évolution des structures dans un contexte de transition d'une mise en place à l'axe vers une situation intraplaque, en accord avec les trois étapes (rapprochement, fixation à l'aplomb et éloignement) décrites ci-dessus. L'autre groupe, formé par la bordure sud-est de la chaîne Walvis et appelé deuxième phase, montre une signature gravimétrique caractéristique d'une mise en place intraplaque, y compris pour les structures à l'âge desquelles la dorsale est à l'aplomb du point chaud. Les deux groupes possèdent signatures géochimiques différentes en termes de rapports Zr/Nb et d'abondance en Ti. Ensuite, à partir de l'analyse comparative des différents degrés d'harmoniques sphériques du géoïde et des nouveaux résultats de tomographie sismique disponibles dans la littérature, nous avons pu montrer l'existence d'une association en profondeur entre les panaches responsables des structures volcaniques de l'élévation du Rio Grande et de la chaîne Walvis et le superpanache africain. L'identification de trois anomalies mantéliques proches des îles de Gough et RSA semblent en faire une meilleure alternative d'emplacement que l'île de Tristan da Cunha, qui est l'hypothèse communément acceptée aujourd'hui.

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Machado, Pessanha Ivo Bruno. "Évolution temporelle et spatiale du sytème d’interaction entre le point chaud de Tristan de Cunha et la Dorsale de l’Atlantique Sud". Brest, 2011. http://www.theses.fr/2011BRES2016.

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Dans ce travail nous avons abordé l’évolution temporelle spatiale du système d’interaction entre le point chaud de Tristan da Cunha et la dorsale de l'Atlantique Sud. Le point chaud de Tristan da Cunha et les structures associées du fond océanique (i. E. La chaîne volcanique de Walvis dans la plaque africaine et l’élévation du Rio Grande dans la plaque sud-américaine) sont parmi les plus importantes de l’océan l’Atlantique Sud. Cependant, ce système est moins étudié que les systèmes présents dans l’Atlantique Nord (e. G. Açores et Islande), et leur origine et évolution reste sujet de grand débat. La compilation des données de sondage bathymétrique hébergé auprès du Centre National de Données Géophysique (National Geophysical Data Center - NGDC), et les données de bathymétrie dérivées de l’altimétrie de satellites furent utilisées pour l’élaboration d’un modèle numérique de terrain (MNT) de l’ensemble de l’Atlantique Sud. Les données d’anomalie à l’air libre dérivées de l’altimétrie d satellites et les données d’épaisseurs sédimentaires furent utilisés pour le calcul de l’anomalie de Bouguer réduite au manteau (Mantle Bouguer Anomaly - MBA) et avec les données des isochrones du fond océanique furent calculé l’anomalie résiduelle de Bouguer réduite au manteau (Residual Mantle Bouguer Anomaly - RMBA), la bathymétrie résiduelle et des nouveaux pôles du mouvement relatif entre le plaques de l’Amérique du Sud et Afrique
In this work we have studied the space and time evolution of the Tristan hotspot and south Mid-Atlantic Ridge interaction system. The Tristan hotspot and its associated bathymetrical features (i. E. Walvis Ridge in the African plate and Rio Grande Rise in the South American plate) are one of the most significant features of the South Atlantic Ocean. However, this system is not as well studied as the systems in the North Atlantic (e. G. Azores and Iceland), and their origin and evolution is an open subject. Data compilation of the available surveys from the National Geophysical Data Center (NGDC) and satellite-derived bathymetry were treated to generate a Digital Elevation Model (DEM) for the entire South Atlantic Ocean. Satellite-derived free-air anomaly data and sediment thickness data were used to calculate the mantle Bouguer anomaly (MBA) and digital isochrons of the ocean floor were used to calculate the residual mantle Bouguer anomaly (RMBA), residual bathymetry and new poles for the South America and Africa relative plate motions. Satellite-derived geoid data and the Earth Gravitational Model - EGM2008 were used for the separation of the different components in the geoid data with the calculation of filters using different levels and degree of spherical harmonics. From kinematics reconstructions based on new rotation poles calculated in this work and using the most accepted hypothesis for the current position of the hotspot, as the volcanic island of Tristan da Cunha, the chronology of the emplacement of the volcanic structures could be detailed

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Grant, Tyron James. "Molecular evolution and population genetics of Nesospiza buntings". Diss., 2004. http://hdl.handle.net/2263/24610.

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Nesospiza is a genus of buntings restricted to the Tristan da Cunha Islands in the central South Atlantic Ocean. They have undergone an adaptive radiation at the islands and currently two species are recognised based on morphology: the small-billed Tristan bunting (N. acunhae), which is a dietary generalist and the large-billed Wilkins' bunting (N. wilkinsi), a dietary specialist. Both species occur on Nightingale Island with no apparent hybridisation between them. On the neighbouring Inaccessible Island there appears to have been a breakdown of the species barrier and the two species hybridise extensively. Also two altitudinally segregated colour morphs of N. a. acunhae occur on Inaccessible Island. The morphological differentiation of Nesospiza is not reflected in either the mitochondrial DNA or the microsatellite data. Rather the data suggest that there are two island lineages and that the sympatric populations on each island are more closely related to each other than to their allopatric (presumed conspecific) island neighbours. The molecular data support sympatric speciation with parallel evolution in Nesospiza, possibly as a result of divergent selection, acting on the sympatric populations on each island, which could have resulted from a change in feeding ecology. Furthermore the molecular data differentiate between the two sympatric colour morphs of N. a. acunhae, which appear to be speciating as a result of assortative mating.
Dissertation (MSc (Genetics))--University of Pretoria, 2005.
Genetics
unrestricted

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Libri sul tema "Fishes – Tristan da Cunha"

St. Helena, Ascension, and Tristan da Cunha. Oxford: Clio Press, 1997.

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Tristan da Cunha, oder, Die Hälfte der Erde: Roman. München: Hanser, 2003.

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Andreas, Munch Peter. Glimpsing Utopia: Tristan da Cunha 1937-38 : a Norwegian's diary. Winchester: George Mann, 2008.

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Isolation and language change: Contemporary and sociohistorical evidence from Tristan da Cunha English. Houndmills, Basingstoke, Hampshire: Palgrave Macmillan, 2003.

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Cookson, Ted. A diary of the final cruise of the RMS St. Helena to Tristan da Cunha, January 15-28, 2004. Greenville, Me: Moosehead Communications, 2004.

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Ltd, Stanley Gibbons Publications. Foreign countries: Great Britain, Tristan da Cunha, British Commonwealth : also featuring Baltic States including Estonia, Egypt, Yugoslavia and Middle East ... 13-14 October 1999. London: Stanley Gibbons Publications Ltd., 1999.

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Helyer, Patrick, e Michael Swales. Bibliography of Tristan Da Cunha. Anthony Nelson, 1998.

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St Helena: Ascension, Tristan Da Cunha. Bradt Travel Guides, 2021.

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Schreier, Daniel, e Karen Lavarello-Schreier. Tristan da Cunha: History. People. Language. Battlebridge Publications, 2003.

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Barrow, K. M. Three Years in Tristan Da Cunha. Echo Library, 2005.

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Capitoli di libri sul tema "Fishes – Tristan da Cunha"

Schreier, Daniel. "Tristan da Cunha". In Isolation and Language Change, 41–72. London: Palgrave Macmillan UK, 2003. http://dx.doi.org/10.1057/9780230505261_3.

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Galbraith, Iain. "Schrott, Raoul: Tristan da Cunha". In Kindlers Literatur Lexikon (KLL), 1–2. Stuttgart: J.B. Metzler, 2020. http://dx.doi.org/10.1007/978-3-476-05728-0_19243-1.

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Schreier, Daniel. "Greetings as an act of identity in Tristan da Cunha English: From individual to social significance?" In Phraseology and Culture in English, 353–74. Berlin, New York: Mouton de Gruyter, 2007. http://dx.doi.org/10.1515/9783110197860.353.

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"Saint Helena (UK): Ascension Island (UK): Tristan da Cunha(UK)". In South America, Central America and Africa, 439–41. Elsevier, 1991. http://dx.doi.org/10.1016/b978-1-85166-661-4.50093-1.

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Schreier, Daniel. "English transported to the South Atlantic Ocean: Tristan da Cunha". In Legacies of Colonial English, 387–401. Cambridge University Press, 2005. http://dx.doi.org/10.1017/cbo9780511486920.016.

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Roberts, D. F., e H. Soodyall. "Population ancestry on Tristan da Cunha–the evidence of the individual". In Molecular Biology and Human Diversity, 196–204. Cambridge University Press, 1996. http://dx.doi.org/10.1017/cbo9780511525643.015.

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"9. Tristan da Cunha in 1961: Exile to the Twentieth Century". In Volcanoes in Human History, 209–27. Princeton University Press, 2002. http://dx.doi.org/10.1515/9781400842858-013.

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"Die Insel als Welt und Text in Raoul Schrotts Roman Tristan da Cunha oder Die Hälfte der Erde". In Inseln und Archipele, 99–114. transcript-Verlag, 2011. http://dx.doi.org/10.14361/transcript.9783839412428.99.

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Schreier, Daniel. "Englishes in Tristan da Cunha, St Helena, Bermuda and the Falkland Islands: PCE, non-PCE or both? Blurred Boundaries in the Atlantic". In Modelling World Englishes, 298–321. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474445863.003.0014.

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This chapter looks at the interplay of extra- and intra-territorial forces that shaped the evolution and sociolinguistic characteristics of four varieties of English spoken in the Atlantic Ocean: the Bermudas, St Helena, Tristan da Cunha and the Falkland Islands. It evaluates general and locally specific forces that operated in the formation of these varieties, with a focus on the nature of various co-existing dialects (ENL, ESL and EFL) in the early contact scenarios that straddle current dividing lines between social and ethnic communities in the respective communities. Some sort of historic ‘push and pull’ operated between extra- and intra-territorial forces in all four varieties. There are domains where the two types cannot be subdivided (attitudes to tourism and immigration) so that external factors (such as settlement policy) have provided the petri dish for the enactment of internal forces at a later stage. This is discussed with reference as to whether dialect contact conditions lend themselves to theorizing and how lesser-known varieties fit into current models of English as a world language.

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"Rwanda, Saint Helena, Ascension and Tristan da Cunha; Saint Kitts and Nevis, Saint Lucia, Saint Martin (French part), Saint Pierre and Miquelon". In Publishers' International ISBN Directory 2015, 3876–77. De Gruyter, 2021. http://dx.doi.org/10.1515/9783110337358-142.

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Atti di convegni sul tema "Fishes – Tristan da Cunha"

Vonk, Robert, Dave Phelp, Chris Boysons e Ruwaida Edries. "SURVEY OF THE OLD DOLOS BREAKWATERS, TRISTAN DA CUNHA". In Proceedings of the 5th Coastal Structures International Conference, CSt07. World Scientific Publishing Company, 2009. http://dx.doi.org/10.1142/9789814282024_0009.

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Pessanha, Ivo, Marcia Maia e Sidney Mello. "Space and time evolution of the interaction system between Tristan da Cunha hotspot and South Mid Atlantic Ridge". In 10th International Congress of the Brazilian Geophysical Society. European Association of Geoscientists & Engineers, 2007. http://dx.doi.org/10.3997/2214-4609-pdb.172.sbgf0475_07.

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Pessanha, Ivo, Marcia Maia e Sidney Mello. "Space and time evolution of the interaction system between Tristan da Cunha hotspot and South Mid–Atlantic Ridge". In 10th International Congress of the Brazilian Geophysical Society & EXPOGEF 2007, Rio de Janeiro, Brazil, 19-23 November 2007. Society of Exploration Geophysicists and Brazilian Geophysical Society, 2007. http://dx.doi.org/10.1190/sbgf2007-210.

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Rapporti di organizzazioni sul tema "Fishes – Tristan da Cunha"

Lewis, R. Camogli Hospital Tristan da Cunha Concept Design and Specification Development. Evidence on Demand, giugno 2014. http://dx.doi.org/10.12774/eod_cr.june2014.lewisretal.

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Di Bella, Veronica. Environmental screening note for the proposed hospital development on Tristan da Cunha. Evidence on Demand, aprile 2015. http://dx.doi.org/10.12774/eod_hd.november2013.bella.

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Lange. Camogli Hospital redevelopment: background evidence on approach to building a new hospital on Tristan Da Cunha. Evidence on Demand, agosto 2013. http://dx.doi.org/10.12774/eod_hd043.jul2013.lange.

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