Unveiling the Mask of Transshipment: Detecting Transshipment Behavior with VMS Data

Maritime transshipment by carrier vessels refers to the exchange of catches between fishing vessels and carrier vessels at sea, a key process that helps to prolong operational time and boost the efficiency of offshore operations. However, this practice also complicates regulation efforts and could facilitate illegal, unreported, and unregulated (IUU) fishing. In this study, candidate transshipment segments are extracted by analyzing large volumes of vessel positioning data from the Vessel Monitoring System (VMS). Moreover, the spatiotemporal interactions between carrier vessels and fishing vessels are examined to pinpoint transshipment events. To enhance data processing efficiency, a Spark-based distributed computing framework was employed for parallel spatial analysis. The study also investigates the variation in transshipment durations across different periods and explores the dynamic changes in transshipment hotspot areas. The proposed method's validity is confirmed through correlation analysis with real-time fishing effort data. Experimental results show that this method effectively detects transshipment activities between vessels, reduces computation time by more than 90%, and offers solid technical support for monitoring IUU fishing, thus providing a reliable foundation for fisheries management. This work aids in promoting sustainable fisheries and the conservation of marine resources.