Soft-bottom benthic molluscs from the Baye of Marennes-Oléron : stock assessment and mapping of non cultivated specie, spatial and trophic competition, population dynamics of the cockle Cerastoderma edule (L.)

• Main Author: Sauriau, Pierre-Guy
• Other Authors: LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Bourse de thèse DGRST (CNRS), contrat G.l.S. Sud Vilaine n° 84 & 85/5080582, contrats E.C.O.C.E.A.N. La Rochelle n° 89/1002 & 90/1208, Université de Nantes, ISTPM la Tremblade, Ifremer La Tremblade, Université de Bretagne Occidentale (UBO), Maurice Héral, Albert Lucas
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1992
• Subjects: molluscs; Cerastoderma edule; Marennes-Oléron Bay; stratified sampling; population dynamics; biochemical components; stock assessment; Crepidula fornicata; Mollusque; baie de Marennes-Oléron; échantillonnage stratifié; dynamique de population; biochimie; estimation de stock; compétition trophqiue; [SDE]Environmental Sciences; [STAT]Statistics [stat]; Crassostrea gigas
• Online Access: https://hal.science/tel-04274651; https://hal.science/tel-04274651/document; https://hal.science/tel-04274651/file/Sauriau-PG_1992_THESE-DOCTORAT-UBO-BRESTpp309.pdf

Stock assessment of benthic mollusc species in the Marennes-Oléron Baye was carried out by stratified random sampling preceded by optimal allocation of sampling effort. After correction of methodological biases, the total biomass of uncultivated malacological stocks was estimated, in spring 1984, at 15,500 ± 3,000 tonnes. Statistical precision obtained by this sampling strategy turned out to be very similar to that calculated by a geostatistical procedure. Suspension-feeder molluscs as trophic competitors of the farmed oysters Crassostrea gigas representedalmost 75% of this stock with mainly Cerastoderma edule (5000 ± 2400 tonnes), Mytilus edulis , Crepidula fornicata and Solen marginatus . Their impact in terms of trophic competition with cultivated oysters seems locally appreciable but negligible at the whole scale of the bay. Mapping of malacological populations reveals that the Macoma balthica community was the dominant component in all intertidal areas with a preponderance of Cerastoderma edule populations on sandy bottoms. Multi-year monitoring of population dynamics of C. edule based on a stratified random sampling made it possible to quantify the natural variability of recruitment, growth, mortality and stock-recruitment relationships with regard to the impact of local hand-fishing n this species. Models of seasonal growth are presented. In addition, seasonal and year-to-year changes of the main biochemical constituents of the flesh of C. edule (proteins, lipids and carbohydrates) highlighted the close links between their temporal cycles and the seasonal phenomena of reproduction, growth and natural mortality. L'estimation des stocks des mollusques benthiques du bassin ostréicole de Marennes-Oléron a été effectuée par échantillonnage aléatoire stratifié précédé d'une allocation optimale de l'effort d'échantillonnage. Après correction des biais méthodologiques, la biomasse totale des stocks malacologiques non cultives est évaluée, au printemps 1984, a 15500 ± 3000 tonnes. Le niveau de précision obtenue ...