Acoustic monitoring of Antarctic blue whales in the Southern Indian Ocean : data processing, analysis and interpretation

• Main Author: Leroy, Emmanuelle
• Other Authors: Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Jean-Yves Royer, Julien Bonnel
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2017
• Subjects: Antarctic blue whale; Bioacoustic; Passive acoustic monitoring; Automated detection; Spatial distribution; Seasonality; Migration; Frequency variations; Southern Indian Ocean; Baleine bleue Antarctique; Bioacoustique; Acoustique passive; Détection automatique; Distribution géographique; Saisonnalité; Variations de fréquence; Océan Indien austral; [SDV.OT]Life Sciences [q-bio]/Other [q-bio.OT]; Antarctic; Austral; Baleine; Baleinière; Bleue; Indian; la Baleine; The Antarctic; Antarc*; Antarctique*; Balaenoptera musculus; Baleine bleue; Blue whale
• Online Access: https://theses.hal.science/tel-01686443; https://theses.hal.science/tel-01686443/document; https://theses.hal.science/tel-01686443/file/These-2017-EDSML-Acoustique_sous_marine_et_traitement_du_signal-LEROY_Emmanuelle.pdf

The Antarctic blue whale, Balaenoptera musculus intermedia, is currently critically endangered since the commercial whaling in the 20th century. The population recovery of this species, as well as its ecology, are still poorly known. Due to the ineffectiveness of visual observations, passive acoustics is a preferred method to monitor this highly vocal species. This dissertation presents an analysis of 7 years of passive acoustic monitoring in the southern Indian Ocean, known as a particularly important area of habitat and migration for the Antarctic blue whale. Deployed since 2010 over an area of about 9,000,000 km2, the OHASISBIO hydrophone network provides a multi-site and multi-year acoustic database. An algorithm for the automated detection of Antarctic blue whale calls, first tested and validated, has been applied to characterize the seasonal and geographic patterns of the species presence in the study area. The systematic analysis of these vocalizations also allowed to characterize intra- and inter-annual variations of their frequency, with a long-term decline and seasonal variations. A preliminary analysis of other vocal signatures recorded by the network, from 3 populations of pygmy blue whales and fin whales, highlighted similar variations of their frequencies and outlined their geographic and seasonal patterns of presence in the area. Finally, two previously undescribed vocalizations, with characteristics close to that of blue whale calls, were identified and characterized. La baleine bleue Antarctique, Balaenoptera musculus intermedia, est en danger critique d’extinction depuis la chasse baleinière intensive du 20e siècle. L’état de ses populations et leur écologie restent encore mal connus. En raison de l’inefficacité des observations visuelles, la surveillance par acoustique passive est privilégiée pour étudier cette espèce vocalement très active. Cette thèse porte sur l’analyse de 7 ans de surveillance acoustique passive dans l’océan Indien austral, région d’habitat et de migration ...