New Research: Satellite Imagery Detects Illegal Fishing Activity, Shows Strict Protections Work

Scoop

24-07-2025

The first-of-its-kind study reveals that the worlds most strongly protected marine reserves successfully curb industrial fishing activity, offering a new way to assess fishing compliance and bridge blind spots in current monitoring methods.
Washington, D.C. (July 24, 2025) — New peer-reviewed research in the journal Science demonstrates the power of strict legal bans against industrial fishing in marine protected areas (MPAs). The analysis — which combines satellite imagery and artificial intelligence technology to detect previously untraceable vessels — reveals that most of the globe's fully and highly protected MPAs successfully deter illegal fishing. The study is the first of its kind to demonstrate that the most strictly protected marine reserves are well respected and are not simply 'paper parks.'
The study, 'Little-to-no industrial fishing occurs in fully and highly protected marine areas' finds that:
78.5% of the 1,380 MPAs studied had no commercial fishing activity;
Of the MPAs where satellite images detected illegal fishing activity, 82% of them averaged less than 24 hours of activity per calendar year;
Strongly protected MPAs had, on average, nine times fewer fishing vessels per square kilometer than unprotected coastal areas; and
MPAs designated as strictly-protected with significant fishing activity included those in the Chagos Marine Reserve, the South Georgia and South Sandwich Islands and the Great Barrier Reef Marine Park (combined with the Great Barrier Reef Coast Marine Park), each with approximately 900 hours per year.
'Because strictly protected marine areas discourage illegal fishing, fishes are far more abundant within their boundaries, they produce more babies, and help replenish surrounding areas,' remarked Enric Sala, one of the study's co-authors, a National Geographic Explorer in Residence, and founder of Pristine Seas. 'In other words, the fishing industry benefits from following the rules.'
Illegal fishing poses a significant global threat, jeopardising both the health of ocean ecosystems and the economic stability of the fishing industry. Scientific evidence shows that strictly protected MPAs restore marine life within their boundaries, improve local fishing, provide jobs and economic benefits, and build resilience against a warming ocean. But when MPAs are minimally or lightly protected, the benefits practically disappear.
'The ocean is no longer too big to watch. With cutting-edge satellites and AI, we're making illegal fishing visible and proving that strong marine protections work,' said Juan Mayorga, a scientist with Pristine Seas and co-author of the study.
To arrive at their conclusions, researchers analysed five billion vessel positions from the Automatic Identification Systems (AIS), a GPS-based safety signal transmitted by many industrial fishing vessels, and paired this with satellite images generated by Synthetic Aperture Radar (SAR), which can detect vessels regardless of weather or light conditions. The combination of the datasets — and the use of AI models developed by Global Fishing Watch — allowed researchers to detect the majority of fishing vessels over fifteen meters long, including so-called dark vessels that do not broadcast their location and often operate to evade detection.
'No single dataset can solve the challenge of monitoring fishing activity at sea; each has its blind spots,' asserted Mayorga. 'But when we combine them, their power emerges. By fusing AIS tracking with satellite radar imagery and AI, we are now much closer to the full picture of human activity across the ocean. That's especially important in the crown jewels of the ocean — the world's most strongly protected areas — where the stakes for enforcement and biodiversity are highest.'
Researchers found that the AIS data missed almost 90% of SAR-based fishing vessel detections within these MPAs. Inaccurate data, limited resources and the vastness of the ocean have made effectively monitoring MPAs for industrial fishing a challenge. This groundbreaking methodology offers a powerful new way to assess fishing compliance and bridge blind spots in current monitoring methods, the authors found.
'By using satellites to track fishing vessels, countries can predict the locations of illegal activities and target patrol efforts, saving both manpower and money,' said Jennifer Raynor, the study's lead author and a professor of natural resource economics in UW–Madison's Department of Forest and Wildlife Ecology.
A growing body of research shows that MPAs produce spillover of fishes and invertebrates that increases the catches of species from small and sedentary (lobsters, scallops) to large and migratory (tuna). A 2024 study revealed that fishing catch per unit effort increases, on average, 12% to 18% near the boundaries of large fully protected MPAs.
'Illegal fishing takes place in areas of the ocean set aside for protection, but using satellites we have found — for the first time ever — that the level of protection determines how much risk industrial fishers are willing to take on,' Sala remarked. 'Fully and highly marine protected areas discourage illegal fishing. The stricter the rules in place to conserve ocean areas, the more benefits nations receive — including more fish to be caught outside protected areas' boundaries.'
National Geographic Pristine Seas
Pristine Seas works with Indigenous and local communities, governments, and other partners to help protect vital places in the ocean using a unique combination of research, community engagement, policy work, and filmmaking. Since 2008, our program has conducted nearly 50 expeditions around the world and helped establish 30 marine reserves, spanning more than 6.9 million square kilometers of ocean.
Pristine Seas is part of the global non-profit, the National Geographic Society. Our mission is driven by science and filmmaking — we are fully independent from National Geographic publishing and its media arm.