Terrestrial and Marine Ecology of Marie-Louise, Amirantes, Seychelles
(2010)
Please find an excerpt of the full PDF below
Terrestrial and Marine Ecology of Marie-Louise, Amirantes, Seychelles
The Amirantes group, Seychelles, comprises 24 islands and islets lying between 5o and 6o south of the equator on the Amirantes Bank, western Indian Ocean. The islands were discovered by the Portuguese navigator Vasco da Gama on his second voyage to India in 1502, soon after acceding to the rank of Admiral, and the islands were subsequently named Ilhas do Almirante or Admiral’s Islands (Lionnet, 1970). The group extends over a distance of 138 km, from African Banks in the north to Desnoeufs in the south. Marie-Louise lies at the southern end of the Amirantes group at 6o10′S, 53o08′E, approximately 13 km from Desnoeufs and 280 km south-west of the granitic island of Mahé (Wilson, 1983).
Marie-Louise was first sighted, and named, by Chevalier du Roslan in 1771 but remained uninhabited until the end of the nineteenth century (Ridley and Percy, 1958). In 1771 the island was reported to be densely wooded (Fauvel, 1908-9) but human settlement has greatly altered the natural vegetation. Marie-Louise was first leased in 1905, when the island had a population of 86 people. In 1905, two co-lessees ran the island, one overseeing the production of guano and the other developing agriculture (Wilson, 1983). Over 3,500 tons of guano were exported from the island in late 1905 but by 1906 it was reported that the economically workable deposits had been exhausted (Tonnet, 1906). In 1963, however, it was estimated that approximately 3,000 tons of guano remain on the island, of which half could be taken for local use without damaging agricultural potential (Baker, 1963). In recent times, it has been reported that guano for agricultural purposes has been imported from Desnoeufs (Wilson, 1983). The second lessee in 1905 was involved in establishing agriculture on the island. Eight hundred coconut palms (Cocos nucifera) and numerous casuarina trees (Casuarina equisetifolia) had already been planted on the west coast, holes were dug through the sandstone to increase planting effort and wells were sunk beneath the sandstone. Following the exhaustion of guano supplies, the island’s main commodities turned to fishing and agriculture, supporting an island population of around 20 people. The island was neglected in 1969 and by 1979-1980 little change had occurred, although pigs, poultry, vegetables, maize, tortoiseshell and saltfish were produced for island use and to augment copra exports (Wilson, 1983). Space for an airstrip was cleared in the east of the island in the mid-1960s although the work was never completed. Since 1981, the lease of Marie-Louise has been taken over by the Island Development Company (a Seychelles government parastatal) and in 1983 it was reported that the island was permanently inhabited by approximately 15 agricultural workers and fishermen “based at a small settlement on the west coast above the beach and opposite the only safe anchorage” (Wilson, 1983:185). Copra production continued until 2004 but by 2005 there were no commercial activities at Marie-Louise, only island maintenance by 6 Island Development Company workers.
In 1882 the survey ship H.M.S. Alert found it unsafe to land because of the heavy surf (Coppinger, 1882) and the Percy Sladen Trust Expedition decided that the islands of Marie-Louise and Desnoeufs were best avoided “owing to their lack of suitable anchorage, the only one offering any protection having been ruined by a guano-steamer, which took fire and foundered” (Gardiner and Cooper, 1907:17). Landing by boat is difficult due to the swell coming directly from the open seas surrounding the small island and waves permanently breaking on the surrounding shelf and steep beach (Plates 1 and 2). Perhaps due to this access difficulty, scientific studies at Marie-Louise have been relatively limited.
Previous studies on the terrestrial environment of Marie-Louise include those of G. Auchinleck (November 1921), E.S. Brown (November 1952), M.W. Ridley and Richard Percy (May and July 1955), C.J. Piggott (November 1960) and J.R. Wilson (14 – 15 June 1979 and 10 – 11 July 1980). These studies resulted in brief accounts of the physical geography, vegetation and vertebrate fauna, especially the birds (Auchinleck, 1921; Brown – unpublished diary; Ridley and Percy, 1958; Piggott, 1969; Wilson,1983). The only mention of insect life was by Auchinleck (1921) regarding “the appalling prevalence of white scale [insects] (Aspidiotus)” (Order Hemiptera, suborder Homoptera Sternorrhyncha, superfamily Coccoidea, Family Diaspididae) on coconut palms. Fletcher (1910) mentioned two moths (Order Lepidoptera), that were apparently collected by Rivalz Dupont, Curator of the Seychelles Botanical Gardens, who had visited the “outer” islands in 1906 and 1909 (Dupont, 1929). Other visitors have looked at the marine environment of Marie-Louise: Jacques-Yves Cousteau and Gustave Cherbonnier stopped there onboard Calypso in May 1954 to survey the seabed (Cherbonnier, 1964); Jeanne A. Mortimer visited Marie-Louise in August 1981, December 1981 and December 1982, as part of her study of marine turtles (Mortimer, 1984).
A collaborative expedition between Khaled bin Sultan Living Oceans Foundation, Cambridge Coastal Research Unit and Seychelles Centre for Marine Research and Technology – Marine Parks Authority to the southern Seychelles was conducted onboard M.Y. Golden Shadow, from 10th – 28th January 2005. The primary aim of the expedition was to use a CASI (Compact Airborne Spectrographic Imager) sensor onboard a seaplane to conduct large-scale mapping of the southern Amirantes, Alphonse/St. Francois (Spencer et al., 2009) and Providence Bank. All surveys at Marie-Louise were conducted on 24th January 2005.
