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Menoud M.,University of French Polynesia | Menoud M.,French Research Institute for Exploitation of the Sea | Van Wynsberge S.,University of French Polynesia | Van Wynsberge S.,University of New Caledonia | And 5 more authors.
Journal of Shellfish Research | Year: 2016

Monitoring gonadmaturation for protandrous and functional hermaphrodite species such as the giant clamTridacna maxima is difficult due to the juxtaposition and relative proportion ofmale and female tissues in the gonad [gonadal sex ratio (GSR)]. Here, the relevance of the widely used gonadosomatic index (GSI) as proxy of giant clam gonad maturation is tested with a large dataset (n = 265). Gonadosomatic index is compared with other indices, namely the proportion of the male part harboring spermatozoids, the proportion of empty oocyte follicles, the mean oocyte diameter, and the oocyte elongation. At gonad scale, high index variability highlighted partial spawning. At individual scale, male and female maturation proxies were contrasted, showing either asynchronous emissions of male and female gametes or contrasted spermatogenesis and oogenesis duration. The GSI was mostly driven by the number and diameter of oocytes and therefore it is recommended here as primary proxy for female maturity. Except for the oocyte elongation, all indices were affected by the GSR, which ruled out drawing conclusions at population scale. These results highlight the need for maturation stage proxies that are optimized for functional hermaphrodite species. Source

Andrefouet S.,Institute Of Recherche Pour Le Developpement | Bruckner A.,The Khaled bin Sultan Living Ocean Foundation | Chabran L.,Institute Of Recherche Pour Le Developpement | Campanozzi-Tarahu J.,Direction des Ressources Marines et Minieres | And 2 more authors.
Ocean and Coastal Management | Year: 2014

In 1967, 42 specimens of the green gastropod snail Turbo marmoratus (Linnaeus 1758) from Vanuatu were introduced in one single Tahiti reef, in French Polynesia. The population has been since protected to maximize its chance of spreading, to eventually provide an additional resource for local fishermen. After 45 years of natural dispersal and controlled transfers throughout Society, Tuamotu and Gambier Archipelago, we investigated the population status on 23 different islands and atolls. T.marmoratus failed to colonize Tuamotu and Gambier archipelagos, and Society western atolls. Conversely, it successfully established on the forereefs of all other Society islands and atolls. Densities were the highest on the windward side of Raiatea-Tahaa Islands, with up to 180 individuals per hectare. The observed densities and preliminary extrapolated stock for these two islands justify the rotational opening of the fishery, although additional local investigations on the biology of the species would be useful. The influence of this alien species on the ecology of local reefs remains unknown. © 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Source

Andrefouet S.,Institute Of Recherche Pour Le Developpement | Van Wynsberge S.,Institute Of Recherche Pour Le Developpement | Van Wynsberge S.,University of French Polynesia | Fauvelot C.,Institute Of Recherche Pour Le Developpement | And 2 more authors.
Molluscan Research | Year: 2014

The giant clam subfamily Tridacninae (family Cardiidae) is an important group of bivalve molluscs found throughout the Red Sea and Indo-Pacific, from East Africa to the Eastern Pacific biogeographic region. The Tridacna genus is currently revised with numerous cryptic species identified with molecular markers. New Tridacna records from the fringe of the known distribution areas are extremely useful to identify genetically unique species, geographic ranges, and to examine processes associated with species differentiation. While Tridacna maxima is abundant in French Polynesia (Central South Pacific Ocean) the larger fluted giant clam Tridacna squamosa was formerly reported only in the Austral Islands in the south. Following a recent survey that spanned 23 islands and atolls of the Society, Tuamotu and Gambier Archipelagos, the presence of T. squamosa between the Cook Islands and Pitcairn Islands is confirmed using both morphological and molecular information, suggesting a relic distribution across the Central Pacific Ocean. Tridacna squamosa is rare, but present throughout Tuamotu and Gambier. However, it remained undetected from the Society Islands, probably due to historical over-fishing. This species is valued by local inhabitants, and is sought after mainly as gifts and also for a limited local shell trade. The rarity of T. squamosa may call for conservation measures in the near future. © 2014, © 2014 The Malacological Society of Australasia and the Society for the Study of Molluscan Diversity. Source

Bertucci F.,CNRS Insular Research Center and Environment Observatory | Bertucci F.,University of Liege | Legraverant Y.,CNRS Insular Research Center and Environment Observatory | Berthe C.,CNRS Insular Research Center and Environment Observatory | And 4 more authors.
Estuarine, Coastal and Shelf Science | Year: 2016

Biofouling increases the operational and economic costs associated with pearl production. As current procedures for reducing oyster biofouling can be detrimental to survival and growth and may pollute the surrounding environment developing alternative, biologically-mediated, methods could potentially increase both production and ecological sustainability. With this in mind, the present study investigated natural cleaning of black-lipped pearl oysters, Pinctada margaritifera, by butterflyfishes (Chaetodon). The feeding behaviour of six butterflyfish species was examined at Rangiroa Atoll, French Polynesia: Chaetodon auriga, Chaetodon citrinellus, Chaetodon ephippium, Chaetodon lunulatus, Chaetodon trifascialis and Chaetodon ulietensis. All species cleaned the surface of pearl oysters by removing epibionts (from 16% to 40% of total biomass), although dietary variation may explain different cleaning efficiencies. Generalist omnivores (C. auriga, C. citrinellus, C. ephippium and C. ulietensis) were the most efficient cleaners (% cleaning range: 26-40% of total biomass). Within this group, C. ephippium removed the most biomass (average of 41%) targeting algae and anemones. However, C. auriga targeted the most diverse range of epibionts, removing significant amounts of algae, sponges, tunicates, and anemones. These results suggest that foraging by butterflyfishes can substantially reduce biofouling on economically-important tropical bivalves. © 2016 Elsevier Ltd. Source

Ky C.-L.,French Research Institute for Exploitation of the Sea | Blay C.,French Research Institute for Exploitation of the Sea | Sham-Koua M.,French Research Institute for Exploitation of the Sea | Lo C.,Direction des Ressources Marines et Minieres | Cabral P.,Gauguins Pearl Farm
Aquaculture | Year: 2014

The top aquaculture species in French Polynesia is Pinctada margaritifera, a mollusc grown for the production of a unique gem: the black pearl. One of the challenges facing the pearl farming industry is to "produce less but better pearls" through genetic improvement. An experimental hatchery system was used to generate full-sib families to be tested for their potential as donor "oysters". A large-scale grafting experiment was done and seven cultured pearl quality traits: grade, surface defects, lustre, darkness level, visual colour categories, circles and shape categories were recorded. Our results revealed, for the first time, significant phenotypic relationships between these quality traits. The grade A cultured pearl class had the largest proportion of pearls with a green overtone (65%), the lowest number of circled pearls (15%) and the maximum of round-shaped pearls (45%). In contrast, the "reject" cultured pearl class had the largest proportion of pearls with grey body color (65%), the greatest number of circled pearls (35%) and the maximum with a baroque shape (nearly 60%). When grade components were studied separately, cultured pearls in the zero surface defect class exhibited the same tendencies as grade A pearls, contrasting with the class where there were more than ten defects on the surface of each pearl. When cultured pearls were classified according to the presence or absence of lustre, pearls with lustre mostly had a green overtone colour, whilst pearls without lustre did not. These findings have major implications for cultured pearl quality improvement, as modern genetic breeding methods can increase the proportion of high quality cultured pearls though selected lines of donor oysters capable of producing pearls with a green overtone. Selection of appropriate donor phenotypes, incorporation of pigmentation traits into a pearl oyster breeding programme and production of lines with desirable colours will be developed for oyster aquaculture in French Polynesia. © 2014 Elsevier B.V. Source

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