In a globalized context, the migratory space-borders, crossroads and relays are privileged spaces of contemporary socio-space recombinings. An intense place of mixing of population, Nouadhibou is one of the most important towns in a country having known major urban transformations during the last half-century. The city belongs to the emergent whole of the new Saharan migratory relays, but is made conspicuous by the importance of its harbour activities. The port is at the origin of the urban development. The migrations, first Canarian then Senegalese, Malian and Guinean, have fed the dynamism of the artisanal fisheries sector and the growth of the city for more than one century . The history of the city is obviously linked with the one of the migrations and the one of the development of the harbour activities. But, since 2005, the migrants who arrive at Nouadhibou do not only come for fishing. Indeed, the city acquired the reputation of a passage to Europe through the Canaries Island. From transit migration to long-term settlement, many people stop in Nouadhibou and work in the fisheries sector to provide for their needs, to send money to their families or to gain what is necessary to buy their tickets for Europe. Analysing urban socio-space dynamic by both the demographic and the economic approaches leads us to consider the town as a place of movement and to focus on the observation of the social actors and the urban entities. The interactions between migratory strategies and dynamics of the activities of fishing make Nouadhibou, as a harbour-city, a privileged laboratory of observation of current urban reconfigurations in Middle East and North Africa countries.