Efectos de la variabilidad de la Corriente de Malvinas sobre la abundancia de recursos pesqueros asociados al frente del talud continental

Abstract

Muchas poblaciones marinas presentan fluctuaciones en sus abundancias y principalmente a nivel del reclutamiento, el cual se refiere a la incorporación anual de nuevos individuos a la población (o a la pesquería). Esta variabilidad tiene repercusiones sobre la ecología del ecosistema donde viven; y sobre la economía, en el caso de tratarse de recursos pesqueros, ya que el reclutamiento está estrechamente vinculado al éxito o fracaso de las pesquerías. Los niveles de reclutamiento están débilmente relacionados con la abundancia del stock parental y al esfuerzo pesquero sobre los adultos; y fuertemente asociados a una diversidad de forzantes físicos y biológicos que actúan durante las etapas iniciales de la ontogenia (huevos, larvas y juveniles). La vieira patagónica (Zygochlamys patagonica) y el calamar argentino (Illex argentinus) son recursos pesqueros asociados al frente del talud, que poseen ciclos biológicos con larvas planctónicas y exhiben marcadas fluctuaciones naturales en los niveles de reclutamiento. El objetivo de esta tesis es explorar los efectos de la variabilidad ambiental en el ecosistema del frente de talud sobre las fluctuaciones poblacionales de estas especies de interés económico.

Oceanic circulation off the Argentine continental shelf is dominated by the opposing flows of the Brazil and Malvinas (CM) currents. The transition between the relatively warm and slightly saline waters of the shelf and the cold and higher salinity waters of CM creates a strong thermo-haline gradient known as the shelf-break front. This front constitutes one of the most productive ecosystems in the region and it has a great ecological and economic importance. The CM borders the continental slope, from Drake Passage to approximately 38º S latitude, where it collides with the Brazil Current, generating one of the most energetic regions of the global ocean: the Brazil-Malvinas Confluence. This region, which represents the northern end of the shelf-break front, is characterized by high primary productivity throughout the year and the generation of warm and cold core eddies that export shelf waters to the open ocean. The high contrast of the surface water properties in the frontal area makes satellite images of sea level, ocean temperature and ocean color a very useful tool for studying its variability over a wide range of a temporal and spatial scales. Many marine populations show fluctuations in their abundance, mainly at the recruitment level, which refers to the annual incorporation of new individuals to the population (or to the fishery). This variability has repercussions on the ecology of the ecosystem where they live; and economy in the case of fishing resources, since it is closely linked to the success or failure of fisheries. Recruitment levels are weakly related to parental stock abundance and fishing effort on adults; and strongly associated with a diversity of physical and biological forcing that act over the initial stages of ontogeny (eggs, larvae and juveniles). The Patagonian scallop (Zygochlamys patagonica) and the Argentine squid (Illex argentinus) are fishery resources associated with the slope front, which have biological cycles with planktonic larvae and exhibit marked natural fluctuations in recruitment levels. The objective of this thesis is to explore the effects of environmental variability in the ecosystem of the slope front on the population fluctuations of these species of economic interest.