First demographic insights on historically harvested and poorly known male sperm whale populations off the Crozet and Kerguelen Islands (Southern Ocean)

• Published in: Marine Mammal Science
• Main Authors: Labadie, Guillemette, Tixier, Paul, Barbraud, Christophe, Fay, Rémi, Gasco, Nicolas, Duhamel, Guy, Guinet, Christophe
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Département Milieux et Peuplements Aquatiques, Muséum national d'Histoire naturelle (MNHN)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: mark-recapture; Antarctic; abundance; robust design; sperm whale; multistate; Physeter macrocephalus; [SDE]Environmental Sciences; Kerguelen; Kerguelen Islands; Southern Ocean; Antarc*; Sperm whale
• Online Access: https://hal.archives-ouvertes.fr/hal-01767651; https://doi.org/10.1111/mms.12469

International audience Age and sex dependent spatial segregation has resulted in limited knowledge of the ecology and demography of sperm whale adult males feeding seasonally in high latitudes. This study focused on adult males interacting with the Patagonian tooth-fish (Dissostichus eleginoides) fishery operating off the Kerguelen and Crozet Archipela-gos. Demographic parameters were estimated using a 10-yr-long photo-identification data set paired with multistate closed robust design capture-mark-recapture models. The examination of a set of 29,078 photographs taken from fish-ing vessels during sperm whale depredation events resulted in identification of 295 individuals with nine visiting both study areas. Dispersal between both study regions was estimated to be 1% per year. The mean annual number of interacting sperm whales was estimated to n = 82 (95% CI 58–141) in Crozet and n = 106 (95% CI 76–174) in Kerguelen. Transient proportions were 13% in Crozet and 26% in Kerguelen. Corrected for transience, apparent survival estimates were 0.953 (95% CI 0.890–0.993) in Crozet, and 0.911 (95% CI 0.804–0.986) in Kerguelen. These survival and population size estimates are the first for depredating adult males in high latitudes, and can be used in evaluating the current conservation status of this historically harvested stock and to investigate depredation trends in 35 both Crozet and Kerguelen Islands.