Key finding
Of the 61 foreign tuna vessels monitored in Peruvian waters during 2022, 56 (92%) were detected operating inside the Peruvian Exclusive Economic Zone. Approximately 42% of those with valid permits committed at least one form of IUU activity. Six vessels exceeded their authorised permit days. Three vessels operated with no permit at all. And 16 vessels, despite holding valid permits, entered the Dorsal de Nasca Marine Protected Area, a zone where all fishing is strictly prohibited.
What the research asks
Illegal, unreported, and unregulated (IUU) fishing undermines marine conservation, distorts markets, and deprives coastal states of revenue, but its true scale is hard to measure because the actors are actively concealing their activity. Peru's waters are among the world's richest tuna fisheries and also among the most poorly enforced. This study asked whether a systematic combination of AIS, VMS, and satellite imagery could detect and characterise IUU fishing by foreign tuna vessels in the Peruvian Exclusive Economic Zone, and whether the same vessels behave differently in jurisdictions with stronger enforcement.
What it finds
Of the 61 foreign tuna vessels monitored in Peruvian waters during 2022, 56 (92%) were detected operating inside the Peruvian Exclusive Economic Zone. Approximately 42% of those with valid permits committed at least one form of IUU activity. Six vessels exceeded their authorised permit days. Three vessels operated with no permit at all. And 16 vessels, despite holding valid permits, entered the Dorsal de Nasca Marine Protected Area, a zone where all fishing is strictly prohibited.
The research team combined three data sources: AIS (Automatic Identification System) signals that broadcast vessel position, VMS (Vessel Monitoring System) data required by fishery management organisations, and satellite imagery including Synthetic Aperture Radar (SAR) and the Visible Infrared Imaging Radiometer Suite (VIIRS). The combination of these sources made it possible to detect vessels that turned off their AIS transmitters, a common tactic for concealing illegal activity.
A particularly revealing finding emerged from comparing the behaviour of these same vessels in other jurisdictions. Vessels that fished illegally in Peru showed substantially higher compliance in the Galapagos Marine Reserve, which is patrolled more intensively by Ecuadorian authorities. This suggests that enforcement credibility, not just the existence of regulations, is the decisive factor in deterring IUU fishing.
Why it matters
This paper demonstrates a practical, replicable approach to ocean monitoring that combines satellite technology with regulatory data. The method could be extended to other EEZs and fisheries, providing a scalable tool for coastal states, particularly in the Global South, to monitor their waters without deploying expensive patrol assets.
The finding about enforcement credibility is especially relevant. It confirms that surveillance and sanctions work. The same vessels that broke rules in Peru respected rules in the Galapagos because Ecuador had invested in credible enforcement. For supply chain transparency, this paper offers a model for verifying seafood legality at the harvest stage. Companies sourcing tuna from the Eastern Pacific can use similar methods to assess whether their suppliers are operating legally.