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Marine Ecology Progress Series

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MEPS 613:197-210 (2019)  -  DOI:

Importance of toothfish in the diet of generalist subantarctic killer whales: implications for fisheries interactions

Paul Tixier1,2,*, Joan Giménez3, Ryan R. Reisinger2,4, Paula Méndez-Fernandez5, John P. Y. Arnould1, Yves Cherel2, Christophe Guinet2

1School of Life and Environmental Sciences (Burwood campus), Deakin University, Geelong, Victoria 3125, Australia
2Centre d’Etudes Biologiques de Chizé (CEBC), UMR 7372 Université de la Rochelle-CNRS, 79360 Villiers-en-Bois, France
3Institut de Ciències del Mar (ICM-CSIC), Passeig Marítim de la Barceloneta 27-49, 08003 Barcelona, Spain
4CESAB-FRB, Bâtiment Henri Poincaré, Domain du Petit Arbois, Ave Louis Philibert, 13100 Aix-en-Provence, France
5Observatoire PELAGIS, UMS 3462 du CNRS, Pôle Analytique, Université de la Rochelle, 5 allées de l’Océan, 17000 La Rochelle, France
*Corresponding author:

ABSTRACT: Fisheries may generate new feeding opportunities for marine predators, which switch foraging behaviour to depredation when they feed on fish directly from fishing gear. However, the role of diet in the propensity of individuals to depredate and whether the depredated resource is artificial or part of the natural diet of individuals is often unclear. Using stable isotopes, this study investigated the importance of the commercially exploited Patagonian toothfish Dissostichus eleginoides in the diet of generalist subantarctic killer whales Orcinus orca depredating this fish at Crozet (45°S, 50°E). The isotopic niche of these killer whales was large and overlapped with that of sperm whales Physeter macrocephalus from the same region, which feed on toothfish both naturally and through depredation. There was no isotopic difference between killer whales that depredated toothfish and those that did not. Isotopic mixing models indicated that prey groups including large/medium sized toothfish and elephant seal Mirounga leonina pups represented ~60% of the diet relative to prey groups including penguins, baleen whales and coastal fish. These results indicate that toothfish are an important natural prey item of Crozet killer whales and that switching to depredation primarily occurs when fisheries facilitate access to that resource. This study suggests that toothfish, as a commercial species, may also have a key role as prey for top predators in subantarctic ecosystems. Therefore, assessing the extent to which predators use that resource naturally or from fisheries is now needed to improve both fish stock management and species conservation strategies.

KEY WORDS: Diet · Fisheries · Southern Ocean · Killer whale · Stable isotopes · Fishery interactions

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Cite this article as: Tixier P, Giménez J, Reisinger RR, Méndez-Fernandez P, Arnould JPY, Cherel Y, Guinet C (2019) Importance of toothfish in the diet of generalist subantarctic killer whales: implications for fisheries interactions. Mar Ecol Prog Ser 613:197-210.

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