Thinking of fisheries as a system is a relatively new approach in fisheries science and management. As part of my contribution to this perspective, this thesis uses mental models as a new approach to gain insights into how individuals conceptualize fisheries. Mental models are internal representations of the surrounding world (e.g., phenomena, processes, problems) and they are important because these representations shape how individuals solve problems, take decisions, and communicate. Following an established methodology for analyzing mental models, this thesis begins with establishing a reference model of fishery systems. This reference model is then compared with: 1) the conceptualization extracted from 18 definitions of fisheries formulated by various organizations involved in fisheries management and reference materials; 2) the conceptualization extracted from South African learning material (textbooks used in Grade 9, last compulsory grade, and textbooks used in the only BSc with a major in fisheries offered in the country). The analysis indicates that neither the definitions nor the textbooks manage to provide a comprehensive and balanced understanding of fisheries as systems. Shifting the focus from artefacts (i.e., definitions, textbooks) to human subjects, this thesis developed and tested a novel instrument for eliciting mental models about fisheries. This instrument can be used to elicit the mental models that various stakeholders have about fisheries and the analysis of these representations can guide targeted raising awareness efforts so that gaps or misunderstandings are addressed. The mental models elicited through the three studies are then compared. This thesis introduces the mental models approach as a new method that has the potential to push research further on the path of conceptualizing fishery as a system from a holistic approach.