Fishing behaviours of skippers, killer whales Orcinus orca and sperm whales Physeter macrocephalus in the context of competition around the Patagonian toothfish Dissostichus eleginoides longline fishery in French sub-Antarctic waters

• Main Author: Janc, Anaïs
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), La Rochelle Université, Christophe Guinet, Paul Tixier
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2019
• Subjects: Depredation; sperm whales; killer whales; optimal foraging; human behavioural ecology; mitigation; Déprédation; cachalots; orques; approvisionnement optimal; écologie comportementale humaine; atténuation; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.ES]Environmental Sciences/Environment and Society; [SDV.SA.STP]Life Sciences [q-bio]/Agricultural sciences/Sciences and technics of fishery; Antarctic; Kerguelen; Indian; Orques; Antarc*; Orca; Orcinus orca; Patagonian Toothfish; Physeter macrocephalus
• Online Access: https://hal.science/tel-04178074; https://hal.science/tel-04178074/document; https://hal.science/tel-04178074/file/Janc%20%282019%29%20-%20Thesis%20manuscript.pdf

Overexploitation of fisheries resources leads to increasing competition between fisheries and marine biodiversity. This competition gives rise to depredation-type interactions (consumption of fish directly on the fishing gears by marine predators). Depredation has i) socio-economic consequences for fisheries (reduced yields); ii) ecological for marine predators (increased risk of bycatch or exposure to a lethal response) and iii) ecosystems (impacts on target and auxiliary resources). This thesis proposes to study, on one of the most lucrative fisheries, the most selective but also the most exposed to depredation, the decisional mechanisms (captains) and behavioural (marine predators) involved in the depredation exerted by the orcas (Orcinus orca) and sperm whales (Physeter macrocephalus) on the demersal longline fishery targeting Patagonian toothfish (Dissostichus eleginoides) in the French Exclusive Economic Zones of the Crozet and Kerguelen, Indian Ocean. By an original approach combining human and animal ethology against the backdrop of optimal foraging theory at two spatio-temporal scales, we show that i) this depredation is marked with a competition all the more important as the captains are experienced; (ii) odontocetes adjust their natural behaviour to benefit from the supply of food from the fisheries; (iii) no decision-making simultaneously allows high fishing yield and reduced depredation. These results highlight the importance of fisheries pressure on natural resources and the relevance of future bio economic and socio-ecosystem assessments to ensure the economic viability of fisheries and the sustainability of exploited and ancillary natural resources. La surexploitation des ressources halieutiques entraîne une compétition croissante entre les pêcheries et la biodiversité marine. Cette compétition donne lieu à des interactions de type depredation (consommation des poissons directement sur le matériel de pêche par les prédateurs marins). La déprédation engendre des conséquences i) socio-économiques ...