Ichthyofauna Research On Underwater Mountain Within The North-Atlantic Ridge And Adjacent Areas

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From the mid-1970s to the late 1980s the active fishery researches aimed at revealing the fishery potential of ichthyofauna associated with the North-Atlantic ridge and adjacent areas were carried out by AtlantNIRO and Zaprybpromrazvedka. These researches included species composition and zoogeographic structure of ichthyofauna associated with the North-Atlantic ridge and other underwater mountains. In the work the data on ichthyofauna species composition of the northern part of the North-Atlantic ridge (43-57ºN, 28-34ºW), Corner Mountains (34-35ºN, 48-52ºW, underwater mountains (guyots) southwards of Azores (28-32ºN 30-34ºW) and Rockall underwater mountains are presented based on considerable sampling material (about 200 species). Peaks of high mountains (minimum depths up to 300 m), located eastwards of the Mid-Atlantic ridge (Rockall and the underwater mountains southwards of Azores), are inhabited by the bottom ichthyofauna associated with European and North-African shelf. In this area the East-Atlantic species significantly prevail as compared to amphi-Atlantic and common tropical. On the Rockall plateau boreal and boreal-tropical European species prevail, while on the underwater mountains southwards of Azores the north-subtropical, boreal-subtropical and common tropical East-Atlantic species typical of the self of the Southern Europe and North-west Africa predominate. At mesobenthonic depths (more than 500m) the pattern of zoogeographic structure changes with ichthyofauna species composition variations. Ichthyofauna acquired similar pattern irrespective of the geographical location on the Mid-Atlantic ridge westwards or eastwards of it. Everywhere at these depth levels common tropical, amphi-atlantic and boreal-subtropical species predominate considerably. The number of East-Atlantic species is insignificant as compared to the above categories, though the increase of the East-Atlantic species is observed at the slope of the Rockall plateau and underwater mountains southwards of Azores, as well as the increase of common tropical species in Corner Mountains and the Mid-Atlantic ridge. The West-Atlantic fauna component on the peaks and slopes of researched mountains is small, and even on Corner Mountains located westwards of the Mid-Atlantic ridge the proportion of East-Atlantic species is twice more than West-Atlantic species (8:4). At mesobenthonic depths (more than 500m) in all areas the bathyal-pelagic fishes considerably predominate as compared to the bottom ones both by species diversity and biomass.