Résumé
Fishermen aim to optimize the cost and benefit ratios of their behaviourswhen exploiting resources. Over the past 60 years, their decisions havebeen driven by an increasingly complex set of variables including thegrowing interactions with marine predators feeding on catches on fishinggear, a behaviour termed depredation. How skippers, as decisionmakers, minimize these interactions while maximizing fishing success, isstill poorly understood. This question was investigated in commercialPatagonian toothfish (Dissostichus eleginoides) longline fisheriesoperating in subantarctic waters where skippers are confronted toextensive depredation by sperm whales (Physeter macrocephalus) andkiller whales (Orcinus orca). Using a 15-year fishing dataset andmultivariate analyses, fishing behaviours were characterized from spatiotemporaland operational descriptors, and associated with the frequencyof whale interactions as a cost and the fishing success as a benefit.Three general behaviours were identified (exploitation, exploration andmixed behaviour) but none combined high fishing success with lowfrequency of interactions. In fact, skippers, as they gained moreexperience, were found to favour fishing in productive areas with highfrequencies of interactions over implementing avoidance behaviours.This type of decision, while potentially optimal on the short-term, isunlikely sustainable as intensifying the local impact fish stocks anddepredating whales. However, large variation in behaviours acrossequally experienced skippers was detected suggesting heterogeneity inindividual perceptions. Together, these findings, by comprehensivelydescribing fishing behaviours and highlighting the importance of theskipper effect, are determinant in developing sustainable management ofsocial-ecological systems stressed by conflicts with whales.