Illegal fishing remains a serious global threat, endangering marine ecosystems and the sustainability of fishing industries worldwide. Marine protected areas (MPAs), designed to conserve ocean life by limiting extractive activities, are crucial for marine conservation. However, monitoring industrial fishing within these zones has long been a challenge.

A research team including scientists from the University of California, Santa Barbara (UCSB) has demonstrated that combining satellite data with artificial intelligence (AI) can effectively track industrial fishing activity within MPAs. This innovative method addresses gaps in traditional monitoring techniques. Published in the journal Science, the study revealed that MPAs with the strongest protections show minimal to no industrial fishing.

Gavin McDonald, part of the UCSB Marine Science Institute and senior project scientist at the Environmental Markets Lab (emLab), emphasized, “It is often assumed that many MPAs exist only on paper and that fishing continues despite protections. However, our findings indicate that strictly protected MPAs are largely free of industrial fishing.”

Jennifer Raynor, lead author and professor at the University of Wisconsin–Madison, added, “MPAs with firm fishing bans perform better than many critics suggest. Despite incentives for illegal fishing due to recovering fish populations, we observed very little such activity, which is encouraging for marine conservation efforts.”

The research compared fishing activity inside strongly protected MPAs to surrounding waters, finding these areas hosted about nine times fewer fishing vessels per square kilometer than unprotected coastal zones. Notably, a quarter of MPAs analyzed had no detected fishing vessels over a five-year period.

The study examined 1,380 MPAs that prohibit industrial fishing, spanning 2.1% of the world’s oceans within national jurisdictions. These include well-known regions like Australia’s Great Barrier Reef and Hawaii’s Papahānaumokuākea Marine National Monument.

To detect fishing activity, researchers first analyzed 5 billion vessel location signals from the Automatic Identification System (AIS), which transmits ship identities and positions to coastal stations. While AIS data indicated little fishing effort inside MPAs, some vessels avoid detection by disabling transponders or operating in areas with poor signal reception.

To identify these “dark vessels,” the team used synthetic aperture radar (SAR) satellite images combined with AI, which reliably detects fishing boats over 15 meters long. This approach confirmed an extremely low presence of industrial fishing inside MPAs, reinforcing the AIS findings.

Interestingly, the AIS data missed nearly 90% of the vessels detected by SAR, highlighting limitations in relying solely on AIS for monitoring. McDonald noted, “I was surprised and encouraged to see how few industrial fishing vessels operate within these strictly protected zones, even when accounting for hidden vessels.”

MPAs not only protect biodiversity within their boundaries but also provide benefits beyond, as abundant fish populations inside protected areas help replenish neighboring fisheries. Enric Sala, marine ecologist and founder of Pristine Seas, which supported the study, explained that legal protections in MPAs lead to healthier fish stocks, which ultimately benefit the fishing industry.

While these results show that industrial fishing is largely absent in strongly protected MPAs, further investigation is needed to understand whether these zones successfully deter fishing or if they were established in regions with naturally low fishing pressure. Sara Orofino, an ocean scientist at The Nature Conservancy and co-author, noted that this distinction is important for shaping future conservation strategies.

Building on this work, McDonald and the emLab team are developing new satellite-based methods to better understand environmental challenges, including measuring greenhouse gas emissions from marine vessels by integrating AIS and SAR data.

Raynor hopes that these findings will inform global conservation policies. “Satellite monitoring can help nations target enforcement efforts efficiently, supporting international goals like protecting 30% of the ocean by 2030,” she said.

Adapted from original reporting by Harrison Tasoff, “Satellite Technology Reveals Industrial Fishing Is Largely Absent in Strictly Protected Marine Areas,” The Current, UC Santa Barbara, 2025. This story was also reported by the Santa Barbara Independent.