Seasonal occurrence of the killer whale (Orcinus orca : morphotype A) off New Caledonia

• Main Author: Borsa, Philippe
• Other Authors: Institut de Recherche pour le Développement (IRD), Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE Nouvelle-Calédonie ), Institut de Recherche pour le Développement (IRD Nouvelle-Calédonie )-Délégation Ifremer de Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche pour le développement
• Format: Article in Journal/Newspaper
• Language: French
• Published: HAL CCSD 2022
• Subjects: Coral Sea; seasonality; predation; morphotype; marine mammal; mer de Corail; saisonnalité; migration; prédation; mammifère marin; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Killer Whale; Orca; Orcinus orca; Killer whale
• Online Access: https://hal.science/hal-03697529; https://hal.science/hal-03697529/document; https://hal.science/hal-03697529/file/Orques%20NC_BullSZF_v.%20haL.pdf

International audience Little is known about the population of killer whales Orcinus orca that occurs in the Coral Sea. Only three sightings made during the decade 1991-2000 have been reported in the scientific literature; no stranding has been recorded up to 2006; no killer whale has been sighted during extensive aerial surveys all around New Caledonia from October to December 2014. However, several images and video records are available from the Internet. The objectives of the present work are to compile observations of killer whales made over the last three decades off New Caledonia in the eastern Coral Sea, to examine the temporal pattern of killer whale occurrence, and to identify their morphotype. Accounts of killer whale sightings were obtained from interviews with yachtsmen and women, from searching the local daily newspapers Nouvelles Calédoniennes, and from searching the Internet. Nine unpublished sightings of killer whales were recorded between 1993 and 2017. Six of these observations were supported by photographs or videographic records, making it possible to characterize individual morphotypes. All sightings but one were outside the barrier reef off the western coast of New Caledonia; one observation was made inside the southern lagoon of New Caledonia in a channel between two passes. The period of killer whale occurrence was from July to December with a peak in August, that is, mostly during the austral winter season, with an extension into the first month of the austral summer. All individuals for which there was sufficient photographic evidence of pigmentation patterns had the following characteristics: supra-ocular white patch elongated and roughly elliptical, with long axis horizontal or quasi-horizontal; its length was ~0.85 to ~1.1 times that of the basis of dorsal fin (N = 6) and ~0.22 to ~0.24 times the distance of snout to abscissa of dorsal fin origin (N = 6); long axis was ~2.8 to ~3.8 times the small axis (N = 2); grey saddle patch posterior to dorsal fin moderately large and ...