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Marine Ecology Progress Series

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MEPS 668:149-161 (2021)  -  DOI:

Contribution of toothfish depredated on fishing lines to the energy intake of killer whales off the Crozet Islands: a multi-scale bioenergetic approach

Johanna Faure1,*, Clara Péron1, Nicolas Gasco1, Félix Massiot-Granier1, Jérôme Spitz2,3, Christophe Guinet2, Paul Tixier2,4,5

1Laboratoire de Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS, IRD, SU, UCN, UA, 75005 Paris, France
2Centre d’Etudes Biologiques de Chizé (CEBC), UMR 7372 La Rochelle Université - CNRS, 79360 Villiers-en-Bois, France
3Observatoire Pelagis, UMS 3462, La Rochelle Université - CNRS, 17000 La Rochelle, France
4MARBEC, Université de Montpellier - CNRS-IFREMER-IRD, Avenue Jean Monnet CS 30171, 34203 Sète, France
5School of Life and Environmental Sciences, Faculty of Science & Technology, Deakin University, 221 Burwood Highway, Burwood, VIC 3125, Australia
*Corresponding author:

ABSTRACT: Fisheries modify prey availability for marine predators by extracting resources but also by providing them with new feeding opportunities. Among these, depredation, which occurs when predators feed on fish caught on fishing gear, is a behavior developed by many species as a way to acquire food through limited foraging effort. However, the extent to which depredated resources from fisheries contribute to the energetic requirements and affect the demography of depredating individuals is unknown. We investigated the contribution of Patagonian toothfish Dissostichus eleginoides depredated on longlines to the energetic requirements of killer whales Orcinus orca around the Crozet Islands (southern Indian Ocean) over the period 2007-2018. Our results indicate that during days when depredation occurred, depredating individuals fulfilled on average 94.1% of their daily energetic requirements with depredated toothfish. However, the contribution varied from 1.2 to 13.3% of the monthly energetic requirements and from 2.4 to 8.8% of the yearly energetic requirements of the total population. Together, these findings suggest that intake of depredated toothfish can be substantial at a fine scale (daily and individually), potentially leading to temporary provisioning effects and changes in predation pressures. These effects become minor (<10%), however, when considering the full population over a whole year. The contribution of depredated fish to the annual energetic requirements of the population has increased in recent years, likely due to larger fishing quotas and greater opportunities for whales to depredate, which stresses the importance of accounting for depredation in ecosystem-based management of fishing activity.

KEY WORDS: Marine mammals · Depredation · Bioenergetic model · Fisheries interaction · Ecosystem-based management · Top predator conservation · Dissostichus eleginoides · Orcinus orca

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Cite this article as: Faure J, Péron C, Gasco N, Massiot-Granier F, Spitz J, Guinet C, Tixier P (2021) Contribution of toothfish depredated on fishing lines to the energy intake of killer whales off the Crozet Islands: a multi-scale bioenergetic approach. Mar Ecol Prog Ser 668:149-161.

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