||Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1976-09 , Vol. 40 , N. 3-4 , P. 439-460
||Atlantic, Marine fish, Geographical distribution
||Some problems in the geographical distribution of oceanic midwater fishes in the Atlantic Ocean are discussed. Remarkable differences were observed in the latitudinal distribution of mesopelagic fish species in the North Atlantic Ocean. These can be related to the oceanic circulation. The Gulf Stream system gives rise to a discontinuity in the position of the oceanic Polar Front. This front, a sharp bounary between subpolar and subtropical waters, follows the northern edge of the Gulf Stream in the western part of the Ocean. East of about 25 degree W the Polar Front becomes weak and untraceable. Relatively warm, high-saline-water of the North Atlantic Current flows North and northeastward by the spreading of the Mediterranean Intermediate Water. Due to the pecularities of the circulation, secondary Polar Fronts are built up at the borders of the results in a broad zonal range extension of midwater fishes to the north and northeast. An analysis of the fishes captured during the International Overflow '73 Expedition of ICES confirms the well known earlier observations of an unhampered northward drift of many temperate and subtropical species to the secondary Polar Fronts. The waters of the Atlantic sector of the Antarctic Ocean harbour a faunal community of midwater fishes quite distinct from communites found to the north of the Subtropical Convergence. PARIN et al. (1974) subdivided the fauna into a subantarctic or notalian, and an antarctic group. This classification is rechecked in the light of the recent 'Walther Herwig' cruises to the area. Four distribution patterns at least are described for the species of the Notalian Zone. The existence of a genuine Antarctic midwater fish fauna remains doubtful at present. The distribution patterns of deep-living mesopelagic fishes rarely taken by smaller gear are compred with those of the common diurnally migrating species. A tendency of the constantly deep-living fishes to enlarge their areas is observed. Bathypelagic species may belong either to the 'Widespread Pattern' or to specialized patterns, which are interpreted as niches acquired or enforced by competition. Such patterns are known as yet in some alepocephaloid fishes only.