Impact of vegetation structure dynamics and usage on the nursery function of West Europeen tidal salt-marshes

The study of the fish population of the Bay of Aiguillon salt marsh (France) and the Mont Saint-Michel Bay enabled us to demonstrate the existence in this singular system of a structuration in colonizing guilds. Some species colonize the marsh exclusively during their first year or first years (salt marsh colonizing year's youths and juveniles) Other species reside in the marsh, like the gobies Pomatoschistus spp. and spend their entire biological cycle around the marsh (salt marsh colonizing resident species). Another category of species goes about the marsh in an opportunist way, using it as a privileged feeding area during their early stages or when adults (salt marsh colonizing opportunist species). The activities linked to the conservation of the avifauna bring about some changes in the initial vegetal architecture in short-cropped puccinellies prairies, leading to a reduction of prey arthropod communities like Orchestia gammarellus. These management measures seem antagonistic to the feeding function of these ecosystems which contribute to the survival of some halieutic populations like the bass [...]