Trophic ecology of the pelagic fish P. antarcticum in East Antarticum

• Main Author: Giraldo, Carolina
• Other Authors: Laboratoire d'océanographie de Villefranche (LOV), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, Philippe Koubbi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2012
• Subjects: Ecologie trophique; indice de condition; ichtyoplancton; écosystème pélagique; Océan Austral; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Antarctic; Austral; Antarc*; Antarctique*; antartic*
• Online Access: https://tel.archives-ouvertes.fr/tel-00829475; https://tel.archives-ouvertes.fr/tel-00829475/document; https://tel.archives-ouvertes.fr/tel-00829475/file/ThA_se_Carolina_GIRALDO.pdf

The East Antarctic pelagic ecosystem is dominated by the pelagic fish Pleuragramma antarcticum which represents up to 90% of the fish biomass. P. antarcticum is the only species of the Nototheniidae family to have an entire pelagic life cycle. This species is characterized by a particularly long larval stage that lasts over a year and a vertical distribution with larvae in the surface layer and the older individuals in deeper ones. P. antarcticum is planktivorous at all stages of development and is the main prey of numbers of top predators. Thus, P. antarcticum appears as an important species in the ecosystem that links phytoplankton / zooplankton and the higher trophic levels. In this thesis we studied the trophic ecology of this species. In the first part of this study we studied fish larvae abundances and the vertical distribution of all developmental stages. We determined what parameters influenced the individual's larval condition and whether P. antarcticum can be considered as a good indicator of environmental changes. The second part of this thesis intended to clarify trophic relationships of P. antarcticum and its role in the ecosystem. We used different methods which allowed us to analyze the immediate diet (gut contents), the one from a period of few weeks (fatty acids) and finally the integration over a period of a month (stable isotopes). P. antarcticum emerges as a key species in a "wasp waist" ecosystem. As a result, changes in this species could have a significant impact on lower and upper trophic levels. L'écosystème pélagique Est Antarctique est dominé par le poisson Pleuragramma antarcticum qui représente jusqu'à 90% de la biomasse des poissons dans la colonne d'eau. P. antarcticum est la seule espèce de la famille des Nototheniidae dont la totalité du cycle de vie se déroule dans la colonne d'eau. Cette espèce se caractérise par un état larvaire particulièrement long qui dure un an et une distribution verticale avec les larves en surface et les individus les plus âgés en profondeur. P. ...