LAUSR

Abstract Transparency is one of the most influential themes in global environmental governance, however it has received limited treatment in transboundary fisheries. Transparency is essential to ensure officials are held accountable for the use of public resources and the achievement of environmental objectives, such as sustainable harvest. Here, we use a case study approach to assess transparency in transboundary fisheries governance, evaluating transshipment in the Western and Central Pacific Ocean, one of the world's most abundant and lucrative fisheries. Transshipment at sea occurs extensively in these fisheries, but often lacks strong monitoring and oversight, and has been associated with illegal or illicit activities. However, actors that rely heavily on transshipment at sea maintain that it can be a legitimate part of the fish commodity chain, under effective regulation. Here we assess whether at-sea transshipment in one of the most regulated and visible fisheries in the world is traceable, verifiable, and legal. Using AIS data and qualitative information from regional and sub-regional sources, we find that 68% of observed potential transshipments remain unsubstantiated even after triangulating with diverse data. We identify three primary areas for improving traceability and transparency of transshipment at sea in the WCPO, and suggest that transparency is ultimately hindered less by technical or administrative constraints, but by tensions between the actors and objectives within management institutions. Increased transparency, and a focus on the underlying dynamics that inhibit it, is necessary to ensure effective conservation and management of transboundary fish stocks, now and in the future.