SUPRABENTHIC MYSIDS FROM THE SOUTHERN MARGIN OF THE CAP-FERRET TRENCH (BAY OF BISCAY) - BATHYMETRIC DISTRIBUTION AND NEAR-BOTTOM SWIMMING ACTIVITY

In the Bay of Biscay there had been no specific study on the deep sea suprabenthic assemblages. This work presents the first observations made in the bathyal suprabenthic communities from the southern margin of the Cap-Ferret trench. Samplings had been made between -350 and -1100 m with a modified MACER-GIROQ sledge allowing a simultaneous sampling at four levels: 0.10 to 0.40, 0.45 to 0.75, 0.80 to 1.10 and 1.15 to 1.45 m above the bottom. Factorial correspondence analysis permited to identify three bathymetric zones: shallow assemblage between -350 and -520 m with the species: Erythrops sp., Atlanterythrops crassipes, Leptomysis gracilis, Mysideis parva, Mysidella biscayensis, Parapseudomma calloplura, Paramblyops rostrata; intermediate assemblage between -520 and -925 m with the species: Hypererythrops serriventer, Gnathophausia zoea, Boreomysis arctica, Pseudomma affine, P. kruppi, P. nanum, Dactylamblyops goniops, Amblyops trisetosa, Mysidetes farrani, Mysideis insignis; and stations under -1000 m with the species: Eucopia hanseni, Parerythrops obesa, Dactylamblyops thaumatops, Chunomysis diadema, Bathymysis helgae, Boreomysis tridens, Dactylerythrops dimorpha. This bathymetric distribution might be explained by sedimentation and food. Swimming activity of mysids had been studied according to their near-bottom vertical zonation; three groups of swimming organisms were distinguished: lower suprabenthic species, upper suprabenthic species and intermediate suprabenthic species.