Links between marine fauna and oceanic fronts on the Patagonian Shelf and Slope

摘要

One of the main oceanographic features in the Southwest Atlantic is the transport of cold waters of Sub-Antarctic origin along the Patagonian slope to temperate latitudes (40-42ºS) by the Falkland Current. Originating from the Antarctic Circumpolar Current in the Drake Passage, the Current splits into two main northward streams skirting the Falkland Islands from west and east. The strongest eastern branch meanders onto the shelf to the south of Beauchêne Island and north-east of the Falkland Islands and creates four fronts with strong upwellings of the Sub-Antarctic Surface Water Mass (SASW). Extension of SASW to the shelf break and its mixture with shelf waters creates quasi-stationary areas of high productivity. Sub-Antarctic fishes (e.g., southern blue whiting) utilise these areas as their feeding and spawning grounds. Deepwater toothfish and squid (Onykia ingens) use them as pathways to migrate from the shelf to deepwater habitats. Temperate fish (e.g., hoki and rock cod) and squid (Illex argentinus) feed mainly at the frontal zones with mixture of SASW and Patagonian Shelf waters. The presence of four quasi-stationary meso-scale fronts between the deepwater Falkland Current and shelf waters plays an important role in distribution, migrations and spawning of marine fauna that use them in accordance to their Sub-Antarctic and temperate origins.