2023_programme: Baleen whale seasonal pattern in the Northern part of the Mozambique Channel (Indian Ocean) using a seismo-acoustic survey network.

• Session: 05. Marine Bioacoustics
  Organiser(s): Jennifer Miksis-Olds
• Lecture: Baleen whale seasonal pattern in the Northern part of the Mozambique Channel (Indian Ocean) using a seismo-acoustic survey network.
  Paper ID: 2035
  Author(s): Dréo Richard, Crawford Wayne, Barruol Guilhem, Bazin Sara, Royer Jean-Yves, Samaran Flore
  Presenter: Dréo Richard
  Abstract: Since March 2019, two permanent networks of Ocean Bottom Seismometers (MAYOBS) and SOFAR hydrophones (MAHY) have been deployed by the REVOSIMA (Réseau de surveillance volcanologique et sismologique de Mayotte) seismology group to monitor the seismo-volcanic crisis which started in 2018 offshore Mayotte Island in the Northern part of the Mozambique channel, Indian Ocean. Past studies have demonstrated the high potential of these opportunistic seismo-acoustic records for environmental monitoring, including baleen whales studies. Indeed, baleen whales emit strong, stereotyped, and regular songs in the very low frequency band (less than 50-100 Hz) for hours, that can be recorded by both OBS or hydrophones at distances of tens of kilometers.\nThe 3-year REVOSIMA dataset provides the first opportunity to study the seasonal pattern of baleen whales in this remote and poorly known area. For this study, we developed an automated detector of stereotyped and regular signals, avoiding the complex step of detecting the call itself. Our detector is indeed based on the known Inter Calls Intervals (ICI) characterizing each whale species, without analyzing the full structure of the song itself. Because of this simple principle, this detector can be easily adapted to all species having stereotyped songs and regular ICI such as different blue whale acoustic populations, fin whales or minke whale.\nThe 3 years of analyzed seismo-acoustic data evidenced many baleen whale calls, with seasonal patterns that improve our knowledge about the boundaries of seasonal migration movements of Antarctic blue whales, pygmy blue whales and more specifically the western Indian ocean population, minke whales and fin whales. \nThese new results are crucial to conservation purposes and particularly for monitoring the post-exploitation recovery of baleen whales.\nThis work is co-funded by the French Biodiversity Agency.
• Corresponding author: Mr Richard Dréo
  Affiliation: Institut de Physique du Globe de Paris
  Country: France
  e-mail: