Contrôles de la distribution spatiale de l'habitat de reproduction chez les populations de poissons. Approche multi-modèles appliquée à la plie et au merlan de Mer du Nord et à l'anchois du Golfe de Gascogne

Spawning is a crucial phase of fish life cycle as it ensures the renewal of individuals in the population. The identification of factors that influence its spatial dynamic is therefore a key feature as it will affect the reproduction success of fish population. A multi-model approach has been developed in order to identify factors that control the spatial distribution of spawning adults of plaice and whiting in the North Sea and of anchovy in the Bay of Biscay. Generalised additive models have been used to relate presenceabsence of adults and their abundances to several hypotheses of control external (geographical position and environment) and internal to the population (spatial dependency, size, age structure and memory). Models were then ranked according to their ability to reflect theobserved distribution. Relevant hypotheses of control were then identified from the best models. The spawning habitat depicts a strong spatial structure. The multi-model approach highlights that (1) environmental factors influence the occupation of spawning areas and (2) population internal factors determine the degree of abundance by which spawning areas are occupied. Temporal persistence of spawning distribution is ensured by attachment of adults to their spawning site. This attachment is stronger for bentho-demersal fish like plaice and whiting than for pelagic fish like anchovy.