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

• Published in: Marine Mammal Science
• Main Authors: Tixier, Paul, Gasco, Nicolas, Duhamel, Guy, Guinet, Christophe
• Other Authors: Terres Australes et Antarctiques Françaises (TAAF), Réserve Naturelle des Terres Australes, Reunion Island Fisheries Companies (SARPC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Crozet Islands; Killer Whale; Orca; Orcinus orca; Patagonian Toothfish; Killer whale
• Online Access: http://dx.doi.org/10.1111/mms.12307; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fmms.12307; https://onlinelibrary.wiley.com/doi/pdf/10.1111/mms.12307

Abstract Sympatric forms of ecologically distinctive killer whales ( Orcinus orca ) have been documented worldwide. This study focused on a new case of such sympatric occurrence of the “Crozet” type and the recently described “type D” killer whales off the Crozet Islands. The two ecotypes are morphologically and genetically distinct, but they both depredate the same local longline fishery. We used observational, photo‐identification, and fishing data, collected between 2003 and 2015, to examine differences in their patterns of depredation. Of the 828 sets where ecotype could be confirmed, type D killer whales interacted with 82 (11%) of the sets, including 9 (1%) sets that were simultaneously depredated by both ecotypes. Associations between the two types were never observed. Type D killer whales typically occurred in larger groups and both ecotypes preferentially depredated Patagonian toothfish ( Dissostichus eleginoides ). GLMM modeling revealed that the probability of type D depredation significantly increased throughout the study period, especially in deep waters, and photo‐identification data suggested that a subset of all individuals were habituating to depredation. This study documents the partitioning of resources between two distinct ecotypes of killer whales and provides preliminary insight into the feeding ecology of the rare type D killer whale.