Mise en place des premiers comportements et utilisation de l'habitat après l'émergence chez les salmonidés d'eau courante

Abstract

In rheotactic salmonids, the short period (a few days) after émergence from the gravel is critically important for individual survival. In allopatric or sympatrie situations, fry have to select an habitat providing shelters against predators or downstream displacement by water current, or food as invertebrates drift. Experiments done during the last few years with différent salmonid species such as Brown trout (Salmo trutta), Atlanti c salmon (Salmo salar) an d Grayling (Thymallus thymallus) showed post-emergent behavioural variabilit y correspondin g to varied environmental conditions. Différent forms of fry dispersai appeared through downstream movement or displacement towards the banks and/or in the vicinity of the redd area, to more or less benthic microhabitats well adjusted to the size and swimming capacity of the différent species. The présence of conspecifics influenced microdistribution through compétition for the best stations for prey capture (invertebrates drift). The présence of predators could delay émergence or cause reburial of fry in the gravel, but more often increase downstream movement. Article