Structure and zonation of demersal fish assemblages off the Azores Archipelago (mid-Atlantic)

Abstract

Listen

Translate article

The assemblages of the demersal fish fauna of the Azores Archipelago are described from longline surveys that extended from the coastline to 1200 m water depth. A total of 104 fish spe- cies from 47 different families were caught, and despite the changes of biogeographic affinities with depth, most species caught are of subtropical origin (mainly from the Eastern Atlantic/Mediterranean areas) or have a broad geographic distribution. Four large-scale fish assemblages following a depth- aligned structure were found: a shallow-shelf/shelf-break assemblage at depths < 200 m, an upper- slope assemblage at 200-600 m, a mid-slope assemblage at 600-800 m and a deep mid-slope assem- blage at 800-1200 m. Within the main shallow assemblage, 4 small-scale fish assemblages were found: an inner-shelf-island assemblage, an outer-shelf-island assemblage, a seamount/island- shelf/shelf-break assemblage and a transitional shelf/break assemblage. The bathymetric delin- eation of the mid-slope assemblages coincides with the known distributions of the North Atlantic Central Water (NACW), Mediterranean Water (MW) and the upper influence of the intermediate waters in the region: the northern sub-polar waters (Subarctic Intermediate Water (SAIW), the Labrador Sea Water (LSW)) and the Antarctic Intermediate Water (AAIW). The delineation of the shallow small-scale fish assemblages appears to be determined by small-scale environmental factors (e.g. bottom characteristics, seamounts or island areas).