Ecological implications of recently enhanced transport of warm temperate waters into the southern Patagonian Shelf

Alexander Arkhipkin

Abstract:

In the last five years it has been observed a notable trend in meteorology of the Southern Ocean that resulted in shifting the Antarctic chain of macroscale Low Pressure Cyclonic Eddies to the north. Prevalent westerly air flows over the southern Patagonian Shelf changed to northerly/southerly air flows with an increased wind intensity and duration. Strong northerly and north-westerly winds enhanced the spread of the warm inflow of temperate waters from the northern to the south-eastern parts of the Patagonian Shelf down to the northern coasts of the Falkland Islands. Consequent southern shift of the ecotone zone between temperate and subantarctic waters caused some major changes in fish communities with temperate common hake becoming the main abundant fish predator whilst subantarctic hoki and red cod moving to the western and southern parts of the shelf. Another abundant predator, Argentine shortfin squid Illex argentinus also penetrated further south. In a particular warm autumn season 2015, dense aggregations of I. argentinus emerged in the nursery and feeding grounds of subantarctic Patagonian squid Doryteuthis gahi and quickly dispersed its commercial aggregations, causing early closure of the fishing season. Enhanced south-easterly drift of temperate waters transported pelagic larvae of large shallow water crab Lithodes santolla from inshore areas of Argentina to the Falkland Islands, where it has not been seen before. Possible ecological implications of these temperate water shifts on the marine ecosystem structure of the southern Patagonian Shelf are discussed together with challenges in fisheries management and stock assessments.

Biography:

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