Stimulating investment in pearl farming in ... - World Fish Center

Suitability of Habitats for Growth of Black-Lip and Silver-Lip Pearl Oysters Final, June 2008Mamanucas/Yasawas/Great Sea Reef System (Vuki et al. 2000). Fringing reefs, the majortype of coral reef, are found around most of the high islands and are distributed from thesouthern end of the Mamanuca Group almost to Beqa, south of Viti Levu (Wells and Jenkins1988). Barrier reefs, the second major type of reef, are found at the edges of island shelvesand are separated from the mainland by a fairly narrow, shallow lagoon channel in whichthe water is generally turbid and of low salinity at the surface. Oceanic ribbon reefs, anothertype of barrier reef, occur in association with lagoons or areas of sea with normal salinity.The Great Sea Reef, Beqa Barrier Reef, Great Astrolabe Reef and some of the barrier reefs inthe Lau Group are oceanic ribbon reefs. Platform reefs are found only in shelf waters andare common inside the Great Sea Reef and within the Mabualau-Ovalau barrier reefs offeastern Viti Levu. There are only two shelf atolls: one in the Lau Group and the other to theeast of Vanua Levu.Coral reefs in Fiji have also been classified according to their position on the insular shelf(outer-, mid and inner shelf) and their exposure to the prevailing wind and seas (windwardand leeward) (Zann and Vuki, 2000). Windward reefs are found on the eastern, south andsouthwestern sides of exposed islands. The outer margins of the fore reef wave terrace havespurs-and-grooves and there is often a large amount of coral debris on the upper reef slopeand low coral cover. Barrier reefs have moderate coral cover and diverse assemblages ofhard and soft corals. Leeward inner-shelf reefs are well protected and their slopes aregenerally composed of coral rock with a low coral cover. The reef tops consist of coral rockand rubble and slope into areas dominated by macroalgae and seagrasses.4.4 French PolynesiaFrench Polynesia stretches across 2,500,000 km 2 of ocean from 134º 28’ W to 154º 40’ W and7º 50’ S to 27º 36” S. There is 3,430 km 2 of emergent land, 12,800 km 2 of reef formationtotalling more than 2,000 km in length (Gabrié, 1998 in Salvat et al. 2000) and about 7,000 km 2of lagoon (Wells and Jenkins 1988). French Polynesia consists of 118 islands distributedacross five archipelagos: Society, Tuamotu, Gambier, Marquesas and Austral Islands, each ofwhich is situated along a south-east to north-west axis (Salvat et al. 2000) (Figure 4). Eightyfourof the islands are atolls and most of the others are mountainous, volcanic islands.Tuamotu, the largest archipelago, consists of 76 islands, 75 of which are low atolls, cappingthe tops of cones which rise steeply from a huge ridge (Wells and Jenkins 1988). The otherisland, Makatea is a raised atoll. The atolls vary in size (from a few to more than 1,000 km 2 ),their lagoons, if present, cover a few to 92 % of the total area of the atoll and range in depthfrom 2 to 60 m (Dufour 2001). The characteristics of the apertures in the atoll rim, the areaand depth of the lagoon and position of gaps, natural channels and immersed coral ringwith respect to the predominant currents affect the rate of renewal of water. The degree ofconnection between the lagoons and the surrounding ocean, as expressed by the ratio of theperimeter of passes + gaps + immersed crown to the perimeter of the atoll varies from 0.01to 0.59. Forty-five atolls lack natural passages to the surrounding ocean, whereas 10 haveseveral passages.The Society Archipelago comprises nine high, volcanic islands and five atolls. Tahiti, thelargest high volcanic island, has discontinuous fringing reefs with a chain of interruptedbarrier reefs partially enclosing a lagoon. Moorea, the second largest high volcanic island,has a barrier reef with twelve passes enclosing a shallow (0.5-3.0 m) lagoon that is 500-1500m wide. Deeper channels in the lagoon are orientated parallel to the coast and open into thepasses. The small twin volcanic islands, Huahine Nui and Huahine Iti are surrounded by anarrow barrier reef which has five passes and raised terrace at its northern end. There isThe Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 14