Assessing the impact of toothed whale depredation on socio-ecosystems and fishery management in wide-ranging subantarctic fisheries

• Main Authors: P Tixier, P Burch, F Massiot-Granier, P Ziegler, D Welsford, MA Lea, MA Hindell, C Guinet, S Wotherspoon, N Gasco, C Péron, G Duhamel, R Arangio, R Tascheri, S Somhlaba, John Arnould
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2020
• Subjects: Fisheries sciences not elsewhere classified; Zoology not elsewhere classified; Policy and administration not elsewhere classified; Science & Technology; Life Sciences & Biomedicine; Fisheries; Marine & Freshwater Biology; Fisheries interactions; Depredation; Subantarctic; Patagonian toothfish; Killer whales; Sperm whales; HUMAN-WILDLIFE CONFLICT; KILLER WHALE; LONGLINE FISHERIES; MARINE MAMMALS; ORCINUS-ORCA; SHARK DEPREDATION; SOUTHERN-OCEAN; BLUEFIN TUNA; SPERM-WHALES; TOOTHFISH; School of Life and Environmental Sciences; 3005 Fisheries sciences; 3103 Ecology; Indian; Southern Ocean; Killer Whale; Orca; Orcinus orca; Patagonian Toothfish; Physeter macrocephalus; toothed whale; Killer whale
• Online Access: http://hdl.handle.net/10536/DRO/DU:30135079; https://figshare.com/articles/journal_contribution/Assessing_the_impact_of_toothed_whale_depredation_on_socio-ecosystems_and_fishery_management_in_wide-ranging_subantarctic_fisheries/20715958

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 eleginoides) 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 toothfish fisheries which are the primary socio-economic activity in subantarctic regions.