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| Hoch, Thierry. |
| Biological test allow to measure the global effect of a presumed polluted solution. They are of great importance in the control of the marine medium quality. described experiences, made on bivalve molluscs, are concerning sediment, which accummulates a lot of toxicants. In corder to obtain quickly precise test results, an optimization of the experimental protocol isproposed. The particular data treatment is then taken up and an analyse of the results of the year is detailed. This analyse brings out the interest of the performed test as well as the orientations to take and the eventual modifications to bring in the future. |
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| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00040/15116/12452.pdf |
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| Labelle, Marc; Hoch, Thierry; Liorzou, Bernard; Bigot, Jean-louis. |
| Sampling operations are not routinely conducted in France to monitor the landings of bluefin tuna caught by purse seiners in the Mediterranean. The length, weight and age frequencies of bluefin caught by this fleet are predicted based on sale records, length-at-age and weight-length relations, trends in fishing and natural mortality rates, and other ancillary data. The resulting length frequencies are more accurate than those predicted by Liorzou and Bigot (1992) using a simpler algorithm, and are spread more evenly across adjacent size classes. Catch-per-unil-effort (CPUE) was expressed as the numbers of age 2 bluefin caught per successful seine fishing trip in the Gulf of Lions fall fishery. CPUE indices were computed by several methods, and compared to... |
| Tipo: Text |
Palavras-chave: Thon rouge; Senne tournante; Prises-par-unité-d'effort; Indices d'abondance; Taux de croissance; Évaluation des stocks; Mer Méditerranée; Bluefin tuna; Purse seine; Catch-per-unit-effort; Abundance indices; Growth rates; Stock-assessment; Mediterranean sea. |
| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00188/29880/28357.pdf |
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| Hoch, Thierry; Menesguen, Alain; Bentley, D. |
| A simple model of the nitrogen cycle in the Channel is proposed. Based on the long-term circulation, this box-model permits the description of the spring phytoplankton bloom in the whole Channel. Spring western thermal stratification has not been taken into account; consequently, the earliest phytoplanktonic development is observed in the eastern Channel, followed by the western, deeper part. This model also shows the influence of nutrient supply from the rivers on the Channel ecosystem, and particularly the influence of the river Seine on the chlorophyll concentrations along the eastern French coast. Comparison of calculated data with measurements shows a fairly good agreement in the eastern Channel but discrepancies are encountered for the western part.... |
| Tipo: Text |
Palavras-chave: CHANNEL; BOX-MODEL; NITROGEN; PHYTOPLANKTON. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00100/21128/18748.pdf |
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| Hoch, Thierry. |
| Ce travail présente un modèle du cycle de la matière organique en Manche, à travers les cycles de l'azote, du phosphore et du silicium. Ces éléments ont été choisis car ils limitent principalement la production primaire en Manche. Dans un premier temps, un sous-modèle physique en boîtes a été' retenu. Grâce au logiciel "ELISE", la Manche a été découpée en 71 boîtes, entre lesquelles les flux d'eau sont automatiquement calculés. A ce modèle de transport horizontal a été couplé un modèle thermo-halin vertical bicouche. Ce dernier simule la température et la salinité dans une couche de surface et une couche de fond, séparées par une pycnocline d'épaisseur nulle. Il permet également le calcul des vitesses d'échange entre les deux couches. Un couplage a été... |
| Tipo: Text |
Palavras-chave: Modèles en boites; Modèles écologiques; Manche; Analyse de sensibilité. |
| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00101/21225/18842.pdf |
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| Hoch, Thierry. |
| This paper deals with a model of the pelagic ecosystem in the English Channel The model takes into account nitrogen biogeochemical cycle explicitly and indirectly phosphorus, silicon and carbon ones. The pelagic ecosystem is described precisely, on the one hand with the help of three phytoplanktonic compartments, and the other by considering the microbial food web. Primary production appears to be mainly controlled by stratification and turbidity, except in the Bay of Seine where high terrestrial nutrient inputs generate a sharp enrichment. Moreover, the model allows some general ecological conclusions to be drawn. From the simulation, it appears that inorganic nitrogen in the water column is mainly produced by an intense recycling. In accordance with in... |
| Tipo: Text |
Palavras-chave: Nitrogen fluxes; Primary production; Ecological model; English Channel; Flux d'azote; Production primaire; Modèle écologique; Manche. |
| Ano: 1998 |
URL: http://archimer.ifremer.fr/doc/1998/publication-841.pdf |
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| Menesguen, Alain; Hoch, Thierry. |
| This paper presents the general framework of an ecological model of the English Channel. The model is a result of combining a physical sub-model with a biological one. in the physical submodel, the Channel is divided into 71 boxes and water fluxes between them are calculated automatically. A 2-layer, vertical thermohaline model was then linked with the horizontal circulation scheme. This physical sub-model exhibits thermal stratification in the western Channel during spring and summer and haline stratification in the Bay of Seine due to high flow rates from the river. The biological sub-model takes 2 elements, nitrogen and silicon, into account and divides phytoplankton into diatoms and dinoflagellates. Results from this ecological model emphasize the... |
| Tipo: Text |
Palavras-chave: Ecological box-model; Thermohaline stratification; English Channel; Primary production. |
| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00337/44790/44479.pdf |
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| Menesguen, Alain; Cugier, Philippe; Loyer, Sophie; Vanhoutte Brunier, Alice; Hoch, Thierry; Guillaud, Jean-francois; Gohin, Francis. |
| The general trend in ecosystem modelling is to improve the spatial resolution by shifting from rough box-models to fine 3D models. Despite the continuous speeding-up of computing, 3D models involving numerous state variables may remain intractable, especially for parameter calibration, when processes with long half-life periods (i.e, from years to decades) are introduced, such as the behaviour of organic matter in sediment and population dynamics of benthic species. In these cases, a first approach can be provided by fast-running box-models, if they take into account the most crucial hydrodynamic properties of the system. In a macrotidal shelf sea such as the English Channel, the long-term horizontal transport can be summarized by the tidal residual... |
| Tipo: Text |
Palavras-chave: English Channel; Stratification; Diatom/dinoflagellate succession; 3D model; Layered box model. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2315.pdf |
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