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Contributions géostatistiques à la biologie halieutique

Abstract : The work, based on several fisheries research survey data, is divided into two parts. The first part is an indicators approach aiming at monitor stocks. A number of indices describing the spatial distribution of a fish population has been selected. These indices do not depend on an arbitrary delimitation of the domain, by receiving a zero contribution from the zero density data samples. In the example of hake in the Bay of Biscay, these indices allow us to describe its spatial dynamics. Such spatial indices are also related to the population dynamic, as shown by some significant correlations with demographic parameters observed for a variety of European stocks. In order to ensure a better monitoring of the stock status, spatial and biological indices have been combined through Min/max Autocorrelation Factors that aim at reducing white noise by extracting the most time-continuous components. This technique has been applied to cod in the North Sea and to anchovy in the Bay of Biscay. The second part aims at evaluating the part of uncertainty coming from the spatial sampling pattern, when estimating abundances from acoustic surveys. The estimation of the abundance is derived from the acoustic backscattering recorded along transects together with biological factors measured at trawl stations, and it is necessary to combine the uncertainties from both sources. This has been done by performing geostatistical conditional simulations within specific multivariate models (based on transformed Gaussian simulations and on a Gibbs sampler to handle the numerous zero acoustic values). The method has been applied to herring around the Shetlands and to anchovy in the Bay of Biscay.
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Submitted on : Wednesday, February 27, 2008 - 8:00:00 AM
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Mathieu Woillez. Contributions géostatistiques à la biologie halieutique. Planète et Univers [physics]. École Nationale Supérieure des Mines de Paris, 2007. Français. ⟨NNT : 2007ENMP1498⟩. ⟨pastel-00003347⟩

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