From bibliographical information on bathymetric and latitudinal distribution of 110 marine fish species of western Patagonia (42º-57ºS), the ichthyogeographic zonation of the area is discussed. The bathymetric distribution of the fish species shows a species association distributed at depths less than 100 m, a second association between 50 and 500 m, and a third association below 500 m depth. This third one is interpreted as a transitional situation of the second one, because of the scarcity of endemic species. These associations present similar latitudinal zonation patterns, including separation into a northern sector, characterized by species of lower latitudes, a southern sector with characteristic and endemic elements of that zone, and an intermediate transition sector considered as an independent association by its large extension and species composition. The Straits of Magellan represent an important faunistic exchange zone between the bottom fish communities of the Southwestern Atlantic and the Southeastern Pacific.