Structure and diversity patterns of deep-sea pelagic fish assemblages in relation to the Mid-Atlantic Ridge (45°N to 50°N)

No abstracts are to be cited without prior reference to the author.

Pelagic fishes from depths of 250 m to 3200 m from 45 °N to 50 °N were sampled during a cruise over the Mid-Atlantic Ridge and adjacent waters in 1982. Cluster analysis revealed 6 assemblages, which were connected to ridge habitats, the continental shelf edge and oceanic habitats. Spatial boundaries for the clusters were set by frontal systems, of which the Southern Subarctic Front and the Mid-Atlantic Front determined the northern and western boundaries. Over the ridge, Melamphaidae, Serrivomeridae, Stomiidae and Centrolophidae increased in abundance. The abyssopelagic assemblages were characterised by the gonostomatid Gonostoma bathyphilum. The myctophid Benthosema glaciale indicated the transition from temperate to subarctic waters. The gadid Micromesistius poutassou and the alepocephalid Xenodermichthys copei were discussed as characteristic species for the shelf edge assemblage. The increase of gelatinous plankton feeders over the ridge, in particular for the centroplophid Schedophilus medusophagus, was discussed with respect to a probable increase of gelatinous plankton abundance in the area considered.