The French pelagic fishery in the Bay of Biscay is currently facing new challenges. To anticipate and support future adaptations of fishers’ strategies, we proposed to scrutinize fishers’ past behaviours and determine the driving factors of their adaptations using a combination of quantitative and qualitative analysis. Annual strategies deployed by the pelagic fleet between 2010 and 2018 were identified through fishing data. Individual sequences of strategies used by vessels then served as a basis for the definition of a new fleet segmentation, revealing behavioural patterns and bridges between strategies. Fishers from two segments were then interviewed to identify the factors underlying their decisions at four different time scales. Fishers surveyed felt in control of both long-term (pluri-annual) and short-term (daily) decisions. Social aspects and personal preferences were found to be preponderant at these time scales. On the contrary, seasonal and annual activities were perceived as being dictated by market opportunities and ecological cycles. We showed that fishers were forced toward a greater dependence on sardine by regulatory constraints and the lack of opportunities on other species. Our study draws perspective by combining historical fishery data analysis with fisher’s experiential knowledge to understand fishing behaviours.