Le Musclomètre : Mesure de la vitalité du muscle adducteur chez les juvéniles de coquille Saint-Jacques

Les eaux côtières françaises, depuis les années 60, ont vu les gisements de coquilles Saint-Jacques régresser jusqu'à atteindre un niveau moyen de 25 t environ en Rade de Brest alors que le tonnage débarqué était de 1520 tonnes en 1962-63. Devant ce déclin, dans les années 80, un programme de repeuplement des gisements de coquilles St-Jacques en Rade a vu le jour. L' objectif principal de ce programme était de forcer le recrutement. C'est à dire, de remonter le stock reproducteur, par apport de juvéniles, à un niveau tel que la pêche pourrait redémarrer. Ce premier programme a été réorienté fin des années 80 début des années 90 de tel sorte que l'on est passé d'un objectif de repeuplement (effet induit des géniteurs) à une aquaculture extensive par la technique de semis-recaptures en recapturant les animaux semés et non leurs  enfants. Des coquilles de 30 mm sont donc semées puis récoltées environ trois ans plus tard quand elles ont atteint une taille minimale de pêche d'environ 102 mm. Ce type d'aquaculture nécessite donc un semis des coquilles. Ce dernier entraîne un stress qui par voie de conséquence induit une réussite plus ou moins régulière des semis. Plusieurs facteurs, biotiques ou abiotiques, comme, par exemple, le site, la saison du semis, peuvent contribuer à une meilleure réussite. Mais aussi et peut-être surtout le facteur Coquille, c'est à dire la taille, la qualité, la « santé» ou encore la «vitalité» des juvéniles semés. Mais comment  peut-on mesurer la qualité ou la vitalité des juvéniles avant le semis ? Parmi les nombreux indices de qualité ou de vitalité déjà expérimentés : Indices de condition (biométrie), charge énergétique adénylique (biochimie), l'étude suivante porte sur un nouvel indice physique, à savoir la force physique du muscle. Après avoir présenté la biologie de la coquille Saint-Jacques, ce rapport traitera des expériences que j'ai  menées dans l'objectif de déterminer des références de vitalité des coquilles avec ce nouvel indice. Ces références sont destinées à pouvoir ultérieurement comparer ('noter') tout futur lot de juvéniles, en fonction de ces classes de référence

NMR study of the LiMnPO(4)*OH and MPO(4)*H(2)O (M = Mn, V) homeotypic phases and DFT calculations.

Following our previous work on the tavorite-like LiFePO(4)*OH and FePO(4)*H(2)O phases, we report here the magnetic and NMR characterizations of analogous LiMnPO(4)*OH, MnPO(4)*H(2)O and VPO(4)*H(2)O phases together with the DFT calculations of the NMR shifts. The first two compounds exhibit Curie-Weiss type magnetic behavior with Curie constants close to the theoretical ones for HS Mn(3+), while the vanadium compound is very close to a pure Curie-type behavior. (7)Li, (31)P and (1)H MAS NMR spectra are reported for the three compounds, and show strong Fermi-contact shifts for the first two nuclei, while the sign and magnitude of the (1)H shifts are very different for the three phases. DFT calculations (FLAPW in GGA+U approximation) using the WIEN2k code and the experimental susceptibilities are shown to reproduce closely the experimental data. This situation is compared to the case of the homologous and isostructural Fe compounds, which exhibit much more complex magnetic behaviors

Contrasting trends between species and catchments in diadromous fish counts over the last 30 years in France

The decline and collapse of populations have been reported for a large range of taxa. Diadromous fishes migrate between fresh water and the sea and encounter many anthropogenic pressures during their complex life cycle. In spite of being of ecological, cultural and economic interest, diadromous fishes have been in decline for decades in many parts across the world. In this study, we investigated the change in five diadromous fish counts in France over a 30-year period using 43 monitoring stations located in 29 rivers across 18 catchments. Our hypothesis was that the counts of these species evolved in a contrasting way between catchments. We also tested the effect of five drivers potentially contributing to the observed trends: catchment, latitude, presence of commercial fisheries, improvement of ecological continuity and salmon stocking. We found contrasting trends in fish counts between species at the national scale, with some taxa increasing (Anguilla anguilla and Salmo trutta), some showing a slight increase (Salmo salar) and some decreasing (Alosa spp. and Petromyzon marinus). For each taxon, except Anguilla anguilla, we highlighted a significant catchment effect indicating contrasting trends between catchments and stations. However, we found no significant effect of catchment characteristics for any of the studied taxa

Les Ports normands : un modèle ?

Le colloque “Les Ports Normands : un modèle ?” dont les actes sont publiés dans ce recueil, s'est tenu à Rouen le 28 mai 1998 et au Havre le 29, à l'initiative du CRHCT (Centre de Recherches sur l'Histoire Comparée de la Transition, Université de Rouen). Il a réuni, pour une réflexion sur les ports normands et la notion plus générale de "modèle portuaire”, des spécialistes reconnus de disciplines et de domaines de recherches différents, historiens des époques moderne et contemporaine, géographes, économistes, sociologues

Diadromous fish modified timing of upstream migration over the last 30 years in France

International audienc

Focused hydrocarbon-migration in shallow sediments of a pockmark cluster in the Niger Delta (Off Nigeria)

International audienceThe Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil, and pore-water were sampled for geochemical studies. The resulting dataset combined with seismic data reveal that shallow hydrocarbon migration in the upper sedimentary section was focused exclusively within the pockmarks. There is a clear tendency for gas migration within the hydrate-bearing pockmarks, and oil migration within the carbonate-rich one. This trend is interpreted as a consequence of hydrate dissolution followed by carbonate precipitation in the course of the evolution of these pockmarks. We also demonstrate that Anaerobic Oxidation of Methane (AOM) is the main process responsible for the depletion of pore-water sulfate, with depths of the Sulfate-Methane Transition Zone (SMTZ) ranging between 1.8 and 33.4 m. In addition, a numerical transport-reaction model was used to estimate the age of hydrate-layer formation from the present-day sulfate profiles. The results show that the sampled hydrate-layers were formed between 21 and 3750 years before present. Overall, this work shows the importance of fluid flow on the dynamics of pockmarks, and the investigated cluster offers new opportunities for future cross-site comparison studies. Our results imply that sudden discharges of gas can create hydrate layers within the upper sedimentary column which can affect the seafloor morphology over few decades

High Risk of Anal and Rectal Cancer in Patients With Anal and/or Perianal Crohn’s Disease

International audienceBackground & AimsLittle is known about the magnitude of the risk of anal and rectal cancer in patients with anal and/or perineal Crohn’s disease. We aimed to assess the risk of anal and rectal cancer in patients with Crohn’s perianal disease followed up in the Cancers Et Surrisque Associé aux Maladies Inflammatoires Intestinales En France (CESAME) cohort.MethodsWe collected data from 19,486 patients with inflammatory bowel disease (IBD) enrolled in the observational CESAME study in France, from May 2004 through June 2005; 14.9% of participants had past or current anal and/or perianal Crohn’s disease. Subjects were followed up for a median time of 35 months (interquartile range, 29–40 mo). To identify risk factors for anal cancer in the total CESAME population, we performed a case-control study in which participants were matched for age and sex.ResultsAmong the total IBD population, 8 patients developed anal cancer and 14 patients developed rectal cancer. In the subgroup of 2911 patients with past or current anal and/or perianal Crohn’s lesions at cohort entry, 2 developed anal squamous-cell carcinoma, 3 developed perianal fistula–related adenocarcinoma, and 6 developed rectal cancer. The corresponding incidence rates were 0.26 per 1000 patient-years for anal squamous-cell carcinoma, 0.38 per 1000 patient-years for perianal fistula–related adenocarcinoma, and 0.77 per 1000 patient-years for rectal cancer. Among the 16,575 patients with ulcerative colitis or Crohn’s disease without anal or perianal lesions, the incidence rate of anal cancer was 0.08 per 1000 patient-years and of rectal cancer was 0.21 per 1000 patient-years. Among factors tested by univariate conditional regression (IBD subtype, disease duration, exposure to immune-suppressive therapy, presence of past or current anal and/or perianal lesions), the presence of past or current anal and/or perianal lesions at cohort entry was the only factor significantly associated with development of anal cancer (odds ratio, 11.2; 95% CI, 1.18-551.51; P = .03).ConclusionsIn an analysis of data from the CESAME cohort in France, patients with anal and/or perianal Crohn’s disease have a high risk of anal cancer, including perianal fistula–related cancer, and a high risk of rectal cancer