Accumulation of migratory micronekton crustaceans over the upper slope and submarine canyons of the northwestern Mediterranean

The distribution of migratory micronekton crustaceans in the axis and in the vicinity of three submarine canyons off the Mediterranean coast of France was investigated. Some species accumulated on the upper slope and in canyon heads. The fauna consisted mainly of two pelagic communities: (i) epipelagic, mesopelagic and infrapelagic oceanic fauna (hyperiids, euphausiids), which were advected to shelf waters during their nocturnal upward migration and were trapped after their morning descent into the canyon heads or on the upper-slope bottoms; (ii) neritic benthopelagic fauna (mainly peracarida species), which were advected offshore during their nocturnal stratification at the surface. Some bathypelagic species (euphausiids, hyperiids and mysids) were concentrated in slope bottoms at the limit of their vertical migration in deep waters.