Bathyal cumaceans of the Catalan Sea (North-western Mediterranean): faunistic composition,diversity and near-bottom distribution along the slope (between 389 and 1859 m)

Deep-water epibenthic/suprabenthic species of Cumacea were studied in the Catalan Sea (Western Mediterranean). Samples (21) were taken at depths from 389 to 1859m, using a Macer-GIROQ type sledge, 32 cumacean species were collected. Diastyloides serratus and Leucon longirostris were the commonest species on the upper slope and middle slope, respectively. On the lower slope (1250–1859 m) dominance by any single species was not apparent and Cyclaspis longicaudata, Procampylaspis bonnieri and Platysympus typicus were the most abundant species. Two leuconids (Leucon cf. serratus, and Leucon (Crymoleucon) sp. A) were recorded for the first time in the Mediterranean Sea. The highest total abundance of cumaceans was encountered over the middle slope. Highest values of species richness and diversity (H') were registered at intermediate depths on the lower slope (1250–1355 m). The low H' value on the middle slope was attributable to the dominance of L. longirostris. Swimming coefficients calculated from near-bottom samples revealed intraspecific differences in the most abundant species. Thus, while mancas, juveniles, immature males and females, and adult females were captured almost exclusively in the lower level of the sledge, adult males of L. longirostris swam in the water column indistinctly between 10 and 140cm above the bottom. Similar trends, although less evident, have been established for other deep-sea cumaceans.