ORIGINAL RESEARCH Assessing the impact of toothed whale depredation on socio-ecosystems and fishery management in wide-ranging subantarctic fisheries Paul Tixier . Paul Burch . Fe ´lix Massiot-Granier . Philippe Ziegler . Dirk Welsford . Mary-Anne Lea . Mark A. Hindell . Christophe Guinet . Simon Wotherspoon . Nicolas Gasco . Clara Pe ´ron . Guy Duhamel . Rhys Arangio . Renzo Tascheri . Sobahle Somhlaba . John P. Y. Arnould Received: 6 November 2019 / Accepted: 12 February 2020 Ó Springer Nature Switzerland AG 2020 Abstract Marine predators feeding on fisheries catches directly on the fishing gear, a behaviour termed ‘‘depredation’’, has emerged as a major human-wildlife conflict globally, often resulting in substantial socio-economic and ecological impacts. This study investigated the extent of this conflict in commercial Patagonian toothfish (Dissostichus elegi- noides) fisheries across subantarctic waters where both killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) feed on toothfish caught on longline hooks. Using long-term datasets from six major fishing areas, from southern Chile to the Indian Ocean sector of the Southern Ocean, statistical models were developed to quantify the catch removals due to whale depredation interactions. The results indicated that these removals were large, totalling more than 6600 t of toothfish between 2009 and 2016 with an annual mean of 837 t [95% CI 480–1195 t], comprised of 317 t [232–403 t] and 518 t [247–790 t] removed by killer whales and sperm whales, respectively. Catch removals greatly varied between areas, with the largest estimates found at Crozet, where on average 279 t [179–379 t] of toothfish per year, equivalent to 30% [21–37%] of the total catches. Together, these findings provide metrics to assess the impacts of depredation interactions on the fishing industry, whale populations, fish stocks and associated ecosystems. With an estimated $15 M USD worth of fish depredated every year, this study highlights the large geographic scale and economic significance of the depredation issue and its potential to compromise the viability of some Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11160-020-09597-w) contains supplementary material, which is available to autho- rized users. P. Tixier (&)  J. P. Y. Arnould School of Life and Environmental Sciences (Burwood Campus), Deakin University, Geelong, VIC, Australia e-mail: p.tixier@deakin.edu.au P. Burch Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Hobart, TAS, Australia F. Massiot-Granier  N. Gasco  C. Pe ´ron  G. Duhamel Laboratoire de Biologie des Organismes et Ecosyste `mes Aquatiques (BOREA), MNHN, CNRS, UCN, IRD, SU, UA, Paris, France P. Ziegler  D. Welsford Department of the Environment, Australian Antarctic Division, Kingston, TAS, Australia M.-A. Lea  M. A. Hindell  S. Wotherspoon Ecology and Biodiversity Centre, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia C. Guinet Centre d’Etudes Biologiques de Chize ´ (CEBC), UMR 7372, CNRS-Universite ´ de la Rochelle, Villiers-en-Bois, France 123 Rev Fish Biol Fisheries https://doi.org/10.1007/s11160-020-09597-w