Depredation of Patagonian toothfish (Dissostichus eleginoides) by two sympatrically occurring killer whale (Orcinus orca) ecotypes: Insights on the behavior of the rarely observed type D killer whales
2016
Tixier, Paul | Gasco, Nicolas | Duhamel, Guy | Guinet, Christophe | Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC) ; Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS) | Biologie des Organismes et Ecosystèmes Aquatiques (BOREA) ; Université de Caen Normandie (UNICAEN) ; Normandie Université (NU)-Normandie Université (NU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA) | Département Milieux et Peuplements Aquatiques ; Muséum national d'Histoire naturelle (MNHN)
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Show more [+] Less [-]English. Sympatric forms of ecologically distinctive killer whales (Orcinus orca) have beendocumented worldwide. This study focused on a new case of such sympatric occurrenceof the “Crozet” type and the recently described “type D” killer whales off theCrozet Islands. The two ecotypes are morphologically and genetically distinct, butthey both depredate the same local longline fishery. We used observational,photo-identification, and fishing data, collected between 2003 and 2015, to examinedifferences in their patterns of depredation. Of the 828 sets where ecotype could beconfirmed, type D killer whales interacted with 82 (11%) of the sets, including 9(1%) sets that were simultaneously depredated by both ecotypes. Associationsbetween the two types were never observed. Type D killer whales typically occurredin larger groups and both ecotypes preferentially depredated Patagonian toothfish(Dissostichus eleginoides). GLMM modeling revealed that the probability of type Ddepredation significantly increased throughout the study period, especially in deepwaters, and photo-identification data suggested that a subset of all individuals werehabituating to depredation. This study documents the partitioning of resourcesbetween two distinct ecotypes of killer whales and provides preliminary insight intothe feeding ecology of the rare type D killer whale.
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