Écologie trophique des juvéniles de merlu (Merluccius merluccius) dans le golfe du Lion : Implications biologiques de la variabilité spatio-temporelle des ressources alimentaires exploitées dans les zones de nourricerie

European hake (Merluccius merluccius) is a commercial and ecological important species in the Gulf of Lions. Juveniles are mainly located on the continental shelf, and abundance of smaller individuals (< 15 cm) is highest during spring in deeper areas principally. Juvenile hake (5 to 24 cm) density, relative condition factor, food resources and food web structure were investigated in four locations of the continental shelf (distributed with depth : shallow-deep, and distance from the Rhone river mouth : Rhone-Agde) during three springs (2002-2003-2004). Changes of food resources were identified with hake length, spatio-temporal variations were also observed for smaller juveniles (< 15 cm). Despite of hake prey diversity, the same organic source is at the base of their food web : phytoplanktonic marine production. High density of 5 to 19 cm hake and best condition of 15 to 24 cm individuals in Rhone location relative to the more distant one suggest that Rhone dissolved inputs affect juvenile hake biology indirectly in the continental shelf part located near the river. Inter-annual variability study of smaller hake (< 15 cm) density, condition and food resources in deep nursery areas highlight key role of feeding on their habitat quality. Suprabenthic crustaceans (euphausiids and mysids) are specially suitable prey for juvenile hake growth and survival during their early life stage, and affect fisheries of the Gulf of Lions, hake being the most important demersal species of commercial landings.