The legal regime for the management of high seas fisheries has evolved extensively in the past decades, through the development of several instruments, through the work of regional fisheries management organizations, and through the growing involvement of non-State actors. Such developments have led to the inclusion of sustainability objectives in the management of fisheries, and to a more holistic understanding of the interconnectedness between fisheries and the broader marine environment. Yet, despite such developments, overexploitation continues to plague marine living resources, and fishing activities remain the main threat to marine biodiversity in areas beyond national jurisdiction (ABNJ). In order to grasp the reasons behind the failure of the regime to deliver, the first part of the study aims to shed light on whether the current framework is sufficiently stable and/or effective to achieve more sustainability for the socio-ecological system that high seas fisheries represent. To do so, the study describes how the interaction between the law of the sea and environmental law has evolved through the various instruments and entities forming the regulatory regime for fisheries, and then analyzes how the principles governing the oceans act as unifying elements among this extensive and fragmented regime. Attention is also dedicated to the process for the development of a new treaty on marine biodiversity beyond national jurisdiction, and to its role as a catalyst for interconnectedness between the law of the sea and biodiversity law on the high seas. This first part of the study concludes with an overview of the challenges currently affecting the effectiveness of high seas fisheries law in achieving sustainable outcomes. It is suggested that these challenges are mostly due to a lack of cooperation, coordination and coherence among instruments, actors and structures. Ensuring cooperation and coordination, however, goes beyond the capacity of existing legal structures only, and this brings the narrative of this study at a crossroads between law, international relations and policy. The second part of the study delves into an exploration of the concept of governance, as well as its application to the oceans, as a basis upon which alternative and complementary regulatory avenues towards sustainability in fisheries management in ABNJ could be examined. The study questions how the broader approach suggested by governance positions the law among other components for social action, and explores the role that governance plays in developing a model to understand the adaptive capacity of the law. The study posits that this dialogue between governance and adaptability leads to the use of alternative mechanisms to improve the interplay between fisheries management and environmental protection, so that this interplay permeates institutions, actors’ behaviours, and, eventually, the legal framework itself. The study explores two of these mechanisms: smart mixes and interplay management, and suggests that such mechanisms should be deliberately considered in decision- and policy-making. The study therefore maps potential ways of rethinking the legal design for high seas fisheries, one that would assist actors in navigating more effectively through the complex interconnectedness between fisheries management and sustainability.