De l'heuristique au thaumaturgique en traitement des données d'écologie marine

In an answer to FRONTIER (1975)à the authors try to define their philosophy about data processing by mathematical methods in marine ecology. They point out that the ecologist may not expect miracles from these methods, but that, correctly used, they provide an especially heuristic tool if not a thaumaturgic one. They first discuss the exact suggest the main features of what should be any correct strategg in data processing, and try to give FRONTIER an answer on certain precise topics. [NOT CONTROLLED OCR]Dans cet article les auteurs définissent leur philosophie quant au traitement mathématique des données en écologie marine. Le texte est articulé en deux grandes parties qui débattent successivement de l'apport potentiel des méthodes mathématiques en écologie marine et de la stratégie d'utilisation de ces techniques. Dans la premeière partie, ils insistent sur la nécessité de ne pas considérer ces méthodes comme miraculeuses (thaumaturgiques), créatrices d'une information absente des données récoltées, mais comme des outils forts utiles (heuristiques) permettant, par une utilisation correcte, une description et une structuration de l'information recueillie. Elles permettent ainsi à l'écologiste de formuler d'une manière explicite et rigoureuse d'une part ses choix fondamentaux comme ses hypothèses, d'autre part ses conclusions. Dans ce chapitre, ils insistent sur deux points essentiels : - les problèmes de reconnaissance de structures sur un ensemble de points qui peuvent être par exemple des prélèvements, n'ont de sens que pour une topologie donnée ; - la possibilité de progresser dans la compréhension d'un pénomène écologique passe par le choix d'un modèle (être mathématique que l'on substitue à la réalité parce que plus maniable), qui peut être simplement descriptif ou explicatif selon les ambitions de départ. [OCR NON CONTRÔLE

Trammel net catch species composition, catch rates and metiers in southern European waters: A multivariate approach

We identified and quantified the effect of season, depth, and inner and outer panel mesh size on the trammel net catch species composition and catch rates in four southern European areas (Northeast Atlantic: Basque Country, Spain; Algarve, Portugal; Gulf of Cadiz, Spain; Mediterranean: Cyclades, Greece), all of which are characterised by important trammel net fisheries. In each area, we conducted, in 1999-2000, seasonal, experimental fishing trials at various depths with trammel nets of six different inner/outer panel mesh combinations (i.e., two large outer panel meshes and three small inner panel meshes). Overall, our study covered some of the most commonly used inner panel mesh sizes, ranging from 40 to 140 mm (stretched). We analysed the species composition and catch rates of the different inner/outer panel combinations with regression, multivariate analysis (cluster analysis and multidimensional scaling) and other 'community' techniques (number of species, dominance curves). All our analyses indicated that the outer panel mesh sizes used in the present study did not significantly affect the catch characteristics in terms of number of species, catch rates and species composition. Multivariate analyses and seasonal dominance plots indicated that in Basque, Algarve and Cyclades waters, where sampling covered wide depth ranges, both season and depth strongly affected catch species compositions. For the Gulf of Cadiz, where sampling was restricted to depths 10-30 m, season was the only factor affecting catch species composition and thus group formation. In contrast, the inner panel mesh size did not generally affect multidimensional group formation in all areas but affected the dominance of the species caught in the Algarve and the Gulf of Cadiz. Multivariate analyses also revealed 11 different metiers (i.e., season-depth-species-inner panel mesh size combinations) in the four areas. This clearly indicated the existence of trammel net 'hot spots', which represent essential habitats (e.g., spawning, nursery or wintering grounds) of the life history of the targeted and associated species. The number of specimens caught declined significantly with inner panel mesh size in all areas. We attributed this to the exponential decline in abundance with size, both within- and between-species. In contrast, the number of species caught in each area was not related to the inner mesh size. This was unexpected and might be a consequence of the wide size-selective range of trammel nets. (c) 2006 Elsevier B.V All rights reserved

Energy dependence of fission product yields from 235

Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and γ-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of two months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from thermal irradiations at the MIT research reactor will also be presented and compared to present data and evaluations. This work was performed under the auspices of the U.S. Department of Energy by Los Alamos National Security, LLC under contract DE-AC52-06NA25396, Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and by Duke University and Triangle Universities Nuclear Laboratory through NNSA Stewardship Science Academic Alliance grant No. DE-FG52-09NA29465, DE-FG52-09NA29448 and Office of Nuclear Physics Grant No. DE-FG02-97ER41033

Remarques d'A. Laurec (biologiste à l'IFREMER) sur le thème 3

Laurec A. Remarques d'A. Laurec (biologiste à l'IFREMER) sur le thème 3. In: Norois, n°133-135, Janvier-Septembre 1987. Espaces côtiers et sociétés littorales. Colloque international des 28, 29 et 30 novembre 1986 à Nantes. p. 316

Remarques d'A. Laurec (biologiste à l'IFREMER) sur le thème 3

Laurec A. Remarques d'A. Laurec (biologiste à l'IFREMER) sur le thème 3. In: Norois, n°133-135, Janvier-Septembre 1987. Espaces côtiers et sociétés littorales. Colloque international des 28, 29 et 30 novembre 1986 à Nantes. p. 316

Le cycle annuel du zooplancton à pointe noire (rp congo)-description mathématique

As part of a general oceanological programme zooplankton samples were collected over a period of 6 years, at least weekly, from a wharf off Pointe-Noire (4°49.2'S; 11°50.3'E).This paper provides a description of the zooplankton seasonal cycle, with special emphasis on the relationships with hydrology. Considering an average year, on a weekly basis, its first aim is to summarize the main features of the similarities and dissimilarities between the weeks of this average cycle.The second aim is to relate these features to different taxa.The paper concludes with a study of annual peculiarities. Mathematical data processing is used to achieve these ends.In addition to its concern with plankton, the paper has a methodological aspect, related to the use of mathematical data processing.The first stage involves the definition of mathematical variables associated with zooplanktonic taxa. [NOT CONTROLLED OCR]6 années de récolte de zooplancton, à partir d'un wharf minéralier, ont été analysées sur une base hebdomadaire.L'étude porte sur une description d'un cycle annuel moyen, sur ses liens avec les différents taxons, enfin sur les particularités annuelles, l'accent étant constamment mis sur les relations avec l'hydrologie. Elle comporte un volet semiquantitatif où l'information est traduite en variables logiques (exemple : absence, présence en faible densité, grande abondance d'une espèce), et un volet proprement quantitatif où les effectifs des taxons dans les prélèvements sont utilisés après transformation. Elle fait appel à des analyses factorielles et comporte à ce propos, des remarques méthodologiques.Les analyses révèlent un cycle saisonnier relativement simple, directement relié aux saisons hydrologiques.Le lien se retrouve, de façon très étroite, au niveau des singularités annuelles pour le zooplancton et l'hydrologie. [OCR NON CONTRÔLE