Éditeur(s) : Actes du IIIème Congrès International des Sociétés Françaises de Malacologie. Les mollusques dans la recherche actuelle, La Rochelle, France, 24-27 juin 2003
Résumé : We analysed a few aspects of oyster culture in New Caledonia. Oyster culture there is not very important, one farm producing 30 tonnes of Japanese oysters per year and the other one, 3 tonnes of rock oysters. Mangrove oyster deposits are traditionally exploited, and this exploitation lead to a decrease of the densities and biomasses observed in the most exploited estuaries. On the four monitored sites, the maximum size observed is comprised between 7.2 to 10 cm, for a mode comprised between 3.6 and 4.8 cm. Densities go from 31 to 251 oysters and biomasses, from 0.751 to 2.553 kg/m2. Regulations focus on the minimum collection size (6 cm) and a fishing prohibition period of 8 months. Based on our observations, we suggest that these dispositions be maintained. We also suggest that a fishing licence for professional fishermen be created, and that leisure fishing be maintained.
On a analysé quelques aspects de l'exploitation des huîtres en Nouvelle Calédonie. La conchyliculture y est faiblement présente, une ferme produisant 30 tonnes par an d'huîtres japonaises et une autre, 3 tonnes d'huîtres de rocher. Les gisements d'huître de palétuvier font l'objet d'une exploitation traditionnelle, qui a conduit à l'affaiblissement des densités et des biomasses observées dans les estuaires les plus exploités. Dans les quatre sites échantillonnés, la taille maximale observée allait de 7,2 à 10 cm, pour un mode compris entre 3,6 et 4,8 cm. Les densités allaient de 31 à 251 huîtres et les biomasses, de 0,751 à 2,553 kg/m2 . Les mesures réglementaires en vigueur concernent la taille minimale de capture (6 cm), et une période de fermeture de la pêche de 8 mois. Les observations faites suggèrent de maintenir ces dispositions. Il est également proposé de créer une licence de pêche pour des pêcheurs professionnels, et de maintenir une pêche de loisir.

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http://archimer.ifremer.fr/doc/2003/acte-6527.pdf
http://archimer.ifremer.fr/doc/00000/6527/

Éditeur(s) : Actes de colloques. Ifremer. Brest [ACTES COLLOQ. IFREMER.]. 1995
Résumé : Informations gathered in the mangrove of the Fort-De-France bay of Martinique (F.W.I.) showed a decreased physiological condition of Crassostrea rhizophorae in the south part of the bay explained by the presence of zinc and by physico-chemical parameters modified in the wet season, such as decreased salinity and decreased levels of nutrients. Bioaccumulation of zinc, lead and cadmium was highly correlated to sediment contamination. Contamination by pesticides and organochlorides was found mainly in oysters from the North part of the bay, characterized by industrial activities and agricultural inputs.

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http://archimer.ifremer.fr/doc/1992/acte-1601.pdf
http://archimer.ifremer.fr/doc/00000/1601/

Éditeur(s) : World Aquaculture Society, Aquaculture 2006
Résumé : Oysters are among the most familiar of all marine invertebrate taxa. However our knowledge of oyster phylogeny and systematics is fragmentary. This is principally due to the plastic growth patterns of these animals, which result in a wide range of overlapping, ecophenotypic variants that greatly reduce the value of analysis based on shell morphology. Besides that, many intentional or accidental anthropogenic transfers have emphasised this situation. In several cases of misclassification or misidentification of oysters, DNA molecular data, have provided valuable new insights on the tracing of introductions or more generally on the phylogeographic relationships between oyster species. We will illustrate this issue with recent case studies from our lab on several flat and cupped oysters: (1) the Crassostrea gigas – Crassostrea angulata couple of Asian species and their successive introductions in Europe, (2) the new species of cupped oysters, Crassostrea honkongensis, described in Hong-Kong and very divergent from the species Crassostrea gigas it was initially supposed to be, (3) the mangrove oyster Crassostrea gasar that was shown not only to be present along the coasts of Western Africa but also along the Atlantic coasts of South America, and (4) the geographic disjunction between Ostreola stentina, described in the Mediterranean Sea, and the genetically closely related species Ostrea aupouria (from New Zealand) and Ostreola equestris (from Mexico Gulf/Atlantic). At the intra specific level, we will focus on one of the main documented case in Europe, the flat oyster, Ostrea edulis. It is a marine bivalve whose natural geographical distribution ranges along the European Atlantic coast from Norway to Morocco, in addition to the Mediterranean and Black Sea. Studies of allozymes, microsatellites and mitochondrial differentiation over the whole range concluded that a significant divergence existed between Mediterranean and Atlantic populations, together with an isolation-by-distance pattern. However, the average mitochondrial haplotypic diversity displayed a high among populations variance, reflecting smaller effective population size in some locations. Additionally, a ten-fold quantitative difference was observed in the same study in Fst between the mitochondrial and the nuclear genomes, which could be due to sex biased differential reproductive success between males and females. In order to further document this hypothesis, two experiments at the population level were conducted. First, brooding females were sampled in a wild population and the number of males fertilizing a given female estimated. Then, parentage analyses were achieved under experimental conditions: successive mass spawnings were collected from a population of potential genitors kept in hatchery, whose genotypes were known, in order to infer a posteriori the relative contribution of each genitor. Moreover, we aimed to better understand the reproduction dynamics of this species. Several patterns of spawning could be distinguished: unique, successive or extended in time. The different parental contributions and reproductive behaviors observed in these experiments are discussed in the context of the hypothesis of a variance in the reproductive success of males and females and consequences in local and temporal reduced effective population sizes.

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http://archimer.ifremer.fr/doc/2006/acte-3475.pdf
http://archimer.ifremer.fr/doc/00000/3475/

Éditeur(s) : Actes Journées Conchylicoles, Ifremer Nantes, 3-4 avril 2001
Résumé : Mangrove oysters include various species that are also present on different coasts. In the southern part of the Atlantic Ocean, Crassostrea rhizophorae has been observed along the southern coast of America and Crassostrea gasar along the western coast of Africa. Fifteen populations of these oysters were sampled from these two geographic areas. Their polymorphism was studied on the 16S mitochondrial fragment both by par sequencing and RFLP analysis. Some samples' caryotype were also analysed. Two haplotypes were identified: C. gasar was found in Africa, but also for the first time in South America, whereas C. rhizophorae was only found on the coasts of South America.
Les huîtres de mangrove englobent plusieurs espèces qui sont présentes sur différentes côtes. Dans la partie sud de l'Océan Atlantique, Crassostrea rhizophorae a été décrite le long des côtes sud américaines et Crassostrea gasar le long des côtes ouest africaines. Quinze populations de ces huîtres ont été échantillonnées dans ces deux zones géographiques. Leur polymorphisme a été étudié sur le fragment mitochondrial 16S par séquençage et analyse en RFLP, le caryotype de certains échantillons a aussi été examiné. Deux haplotypes ont été identifiés: le type C. gasar a été trouvé en Afrique, mais aussi pour la première fois en Amérique du Sud, alors que le type C. rhizophorae a été rencontré seulement sur les côtes d'Amérique du Sud.

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http://archimer.ifremer.fr/doc/2001/acte-3278.pdf
http://archimer.ifremer.fr/doc/00000/3278/

Éditeur(s) : World Aquaculture Society
Résumé : Mangrove oysters encompass several species and their taxomony is unclear. Among then, Crassostrea rhizophorae has been described along the Central and South American Atlantic coasts and Crassostrea gasar along African Atlantic coasts. Most taxonomic studies have so far been based on morphological criteria which are particularly susceptible to plasticity and new insight can be provided by molecular markers. The present work aims to provide information on the phylogeography of these two taxa.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2000/acte-3496.pdf
http://archimer.ifremer.fr/doc/00000/3496/

Résumé : Three species of man.-rove oysters, Crassostrea rhizophorae, C. brasiliana, and C. gasar, have been described along the Atlantic shores of South America and Africa. Because the distribution of these molluscs is of great biological and commercial interest, their taxonomy and distribution deserve further clarification. Therefore, 15 populations were sampled from both continents. Their 16S mitochondrial polymorphism was studied by sequencing and PCR-RFLP analysis. Two haplotypes were identified. Haplotype a was the only one observed in Africa, but it was also observed in South America together with haplotype b. Because C. gasar is the only mangrove oyster identified on the west coast of Africa, haplotype a was attributed to this species, which has thus been shown to occur in South America. Haplotype b is attributed to C. rhizophorae. The karyotypes of specimens of C. gasar, from Africa and from South America, were very similar, and both species were observed at the same location in Brazil. The occurrence of C. gasar in South America adds a third species-in addition to C rhizophorae and C. brasiliana-to the list of species present along these coasts. The predominant surface circulation patterns in this part of the Atlantic Ocean favor the hypothesis that C. gasar was transported from Africa to America. Finally, a phylogenetic tree built with seven 16S sequences from Crassostrea and Saccostrea species showed that C. gasar is intermediate between the American Crassostrea species (C virginica and C. rhizophorae) and the Asian species (C. gigas and C ariakensis).
Biological Bulletin (0006-3185), 2002-06 , Vol. 202 , N. 3 , P. 232-242

Droits : Marine Biological Laboratory.
http://archimer.ifremer.fr/doc/2002/publication-2790.pdf
http://archimer.ifremer.fr/doc/00000/2790/