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| Chardy, Pierre; Desbruyeres, D.; Laurec, A.. |
| Two initial methods are used to define benthic annelid taxocoenoses within the Morbihan gulf. 139 samples and 83 species are included in the matrix data. Correspondence analysis is shown to be appropriate in the classification of heterogeneous systems. It isolates Mesopsio moorei sand population from winole other samples. General analysis is better appropriate within homogeneous systems, and is able to study populations with regard to production. Results are comparable with those got fromthe whole fauna. In addition, a biogeographic limit is pointed out, within amphicteis gunneri sponge spicule muds. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1976 |
URL: http://archimer.ifremer.fr/doc/1976/publication-4983.pdf |
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| Chardy, Pierre; Glemarec, M.; Laurec, A.. |
| The various so-called inertia methods, the aim of which is to summarize the relationships between points by a configuration of reduced dimension, may all be considered variants of a more general method. In this regard, the links existing between Principal Component Analysis, Principal Coordinates Analysis and the Analysis of Correspondences appear clearly. Three fundamental options (inherent in all inertia methods) determine the divergences among these techniques: choice of distance, choice of weights attributed to the points, choice of position of the origin. This viewpoint also shows up the relationships between the analysis of the R and Q matrices of one and the same set of data. The application of these techniques to data of the benthic bionomy of the... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1976 |
URL: http://archimer.ifremer.fr/doc/1976/publication-4999.pdf |
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| Boer, M.; Laurec, A.. |
| SPARRE (1985) has generalized the technique initiated by SCHNUTE et FOURNIER (1980), FOURNIER et BREEN (1983) in order to deal with several length frequency distributions, instead of a single histogram. This paper develops the same approach. Beyond some considerations about the possible constraints, the new points correspond on one hand to analytical derivation of the first and second derivatives of the objective function, on the other hand to the analysis of colinearities. It is suggested for the second question to perform a principal component analysis of the invert of the Hessian matrix of the objective fonction. An example, borrowed from SPARRE (1985) is treated, which suggests that colinearity problems could be extremely important, reducing severely... |
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| Ano: 1987 |
URL: http://archimer.ifremer.fr/doc/00394/50577/51268.pdf |
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| Gros, Philippe; Laurec, A.; Dupouy, Herve. |
| This paper is devoted to statistical problems associated to the estimation of the parameters of a Von Bertalanffy growth curve. A first part corresponds to theoretical considerations, first within the classical regression point of view, corresponding to residuals normaly and independently distributed, then to resampling techniques (Jackknife/Bootstrap). The possibility of using not only the arithmetic mean of observed lengths for a given age, but also medians and modes is discussed. A software has been written in Fortran, which makes it possible to fit by (Weighted) least squares either mean, median or modal length at age, and provides estimates of variances/covariances using the classical approximation within regression theory or resampling techniques. An... |
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| Ano: 1987 |
URL: http://archimer.ifremer.fr/doc/00394/50575/51267.pdf |
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| Laurec, A.; Perodou, Jean-bernard. |
| multiplicative models, applied to the estimation of fishing powers lead after logarithmic transformations to linear systems, the dimension of which can be large. It is however possible to decrease the dimensions of the matrices corresponding to the linear systems created (Morrison, 1976) through a substitution technique. This technique is applied to the classical methods due to Robson (1966) Laurec et Fonteneau, 1979) Gavaris, (1980). The estimation of the variancecovariance of the output is discussed, the duali ty between techniques calculating such quantities, and simpler ones providing just a best fit solution. The practical influence of the correction factor (Laurent, 1963) discussed in a first appendix. A second appendix is devoted to a situation... |
| Tipo: Text |
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| Ano: 1987 |
URL: http://archimer.ifremer.fr/doc/00394/50569/51260.pdf |
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| Laurec, A.; Souplet, Arnauld. |
| Following HARDING (1984-) maximum likelihood techniques are used to estimate recruitment through abundance indices. The first new point in this paper corresponds to the possible use of the historical average recruitment as a shrinkage pole. Under specific assumptions this can lead to the usual regression line where on past data recruitment is explained by the abundance index (e.g. I.Y.F.S.). The second point is related to the possibility of taking into account several abundance indices, corresponding for example to several fleets or research vessels. A maximum likelihood multicalibration technique is suggested. It corresponds to a software which has been implemented in ICES head quarter. Previous comparisons (Method Working Group, 1987) suggests that on... |
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| Ano: 1987 |
URL: http://archimer.ifremer.fr/doc/00398/50907/51681.pdf |
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