Global change challenges coupled natural-human systems such as fisheries social-ecological systems (SES) because they are confined by spatial and functional ecosystem boundaries.

Understanding the capacity of an SES to adapt to changing environmental or socio-economic conditions is complex and entails an analysis of the system´s properties such as resilience, resistance, vulnerability, and adaptive capacity. We used a modified Ostrom framework to structure our analyses and to define the SES components, attributes and indicators of the German mixed demersal fishery SES operating in the southern North Sea. Combining analyses of 20-year time series of environmental and socio-economic data with network analysis and semi-structured interviews allowed for a detailed description of past SES adaptations. Hence, our analysis revealed autonomous adaptations of the SES to environmental and socioeconomic change, which entailed a shift in target species, fishing strategies as well as a distinct decrease in number of actors. We found that the adaptive capacity of the SES has declined over time, and that the SES is now on the brink of being unable to withstand future environmental and socio-economic change. It is therefore captured in an undesirable state, reflecting a social-ecological trap where social and environmental feedbacks negatively reinforce each other. The main barriers to the adaptive capacity of the SES are related to fishing cultures, economic structures, policy frameworks and increasing conflicts over the use of marine space. An in-depth understanding of the linkages between the identified key SES components and related indicators is a prerequisite for developing future management approaches to enhance the adaptive capacity of SES to global change. Our findings highlight the need for tailored and context-specific co-management approaches for all decision-making processes affecting SES.