Faugeras Blaise auteur aut IRD Maury Olivier auteur aut IRD text journalArticle eng text/pdf born digital access In this paper, we address the problem of modeling fish population movements. We first consider a description of movements at the level of individuals. An individual -based model is formulated as a biased random walk model in which the velocity of each fish has both a deterministic and a stochastic component. These components are function of a habitat suitability index, h, and its spatial gradient Vh. We derive an advection-diffusion partial differential equation (PDE) which approximates this individual- based model (IBM). The approximation process enables us to obtain a mechanistic representation of the advection and diffusion coefficients which improves the heuristic approaches of former studies. Advection and diffusion are linked and exhibit antagonistic behaviors: strong advection goes with weak diffusion leading to a directed movement of fish. On the contrary weak advection goes with strong diffusion corresponding to a searching behavior. Simulations are conducted for both models which are compared by computing spatial statistics. It is shown that the PDE model is a good approximation to the IBM. specialized population dynamics biased random walk individual based model partial differential equation 036 020 247 4 837-848 2007 0022-5193 https://www.documentation.ird.fr/hor/fdi:010040753 10.1016/j.jtbi.2007.04.012 0022-5193 [F B010040753] https://www.documentation.ird.fr/hor/fdi:010040753 https://www.documentation.ird.fr/intranet/publi/2007/10/010040753.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2007-11-06 2017-08-23 fdi:010040753 fre