At-sea transshipment of fishery catches: a systematic literature review

Introduction At-sea transshipment is the process of transferring cargo, fuel, crew, and supplies between vessels at sea. Fishery catch transshipment specifically refers to the transfer of fish catches from fishing vessels to refrigerated cargo carriers (reefers) operating beyond national jurisdictions. By enabling fishing vessels to remain at sea for up to 13.3 months, compared with approximately 3 months for non-transshipping vessels, the practice enhances operational efficiency for distant-water fleets while simultaneously functioning as the primary logistical channel for illegal, unreported, and unregulated (IUU) fishing, catch laundering, labor abuses, and the depletion of global marine stocks; IUU losses linked to these activities are estimated at USD 10-23.5 billion annually. Methods A systematic literature review was conducted on 35 peer-reviewed articles published between 2011 and 2025. A multi-database search of Scopus, Web of Science, and Springer Nature returned 2,826 initial records, which were filtered, deduplicated, and screened in full text to yield the final sample. Articles were coded across five thematic categories: monitoring and technology, policy and governance, geopolitical and international relations, economic and social aspects, and environmental sustainability. Results Research interest surged after 2018, with peak output in 2024. Quantitative methodologies dominated (65.7%), followed by mixed-methods and qualitative approaches (17.1% each). Machine learning and satellite-based tracking applied to AIS data are the most common detection tools, but only 50%–70% of events are captured because of AIS disabling, signal manipulation, and dark-vessel activity. Activities concentrate in the Northwest Pacific, West Africa, and the Indian Ocean, frequently involving vessels registered under flags of convenience. Comparative analysis of 17 regional fisheries management organizations showed that only three mandate full observer coverage. Discussion A persistent misalignment between surveillance capabilities and regulatory frameworks remains, sustained by inconsistent reporting and weak enforcement. Three priority gaps emerge: the spatial relationship between transshipment hotspots and ecologically sensitive zones is unexamined; no study has linked vessel registries with port inspection databases into an integrated compliance system; and interdisciplinary research tracing the full chain from at-sea transfer through catch laundering to market entry and labor conditions is absent. Mandatory electronic monitoring, standardized data sharing, and increased transparency in vessel ownership are needed to transform transshipment from a regulatory blind spot into a leverage point for sustainable ocean governance.