Vertical and horizontal distribution of mesopelagic fishes along a transect across the northern Mid-Atlantic Ridge

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A research cruise was made in the Irminger Sea west and southwest of Iceland and adjacent waters on the Icelandic vessel Árni Friðriksson, from 03 Jun-04 Jul 2003. The main purpose was to study distribution and abundance of deepwater redfishes, Sebastes mentella et sp., other pelagic fishes, zooplankton, phytoplankton and the hydrography of the area. Part of the cruise was devoted to a special study on community structure at transect over the northern part of the Mid-Atlantic Ridge (Reykjanes Ridge). In this paper, an overview is given on the composition of the pelagic fish community, both vertically and horizontally, over the northern part of the Reykjanes Ridge. In total, nine trawl hauls were made with a “GLORIA” midwater trawl outfitted with a small mesh size (9-mm) cod-end. Three hauls were made at three different depths west of the Ridge, three above it and three East of the Ridge. A total of 230 nautical miles separated hauls taken west of the Ridge and east of it. A minimum total of 44 species were identified from 23 families. Lanternfishes (Myctophidae), pearlsides (Sternoptychidae), barracudinas (Paralepididae), dragonfishes (Stomiidae) and deep-sea smelts (Microstomatidae) dominated fish catches. Results show that the total number of fishes caught was lowest east of the Ridge, coinciding with warmer deep waters. At all positions both number of species and families increased with depth as the number of individuals decreased with depth.