Maps suggest the ocean has been getting a lot more protection lately. But satellites offer a much less encouraging view.
On paper, the size of so-called marine protected areas (MPAs), designed to shield ecosystems from harm by humans, has grown from less than 5 million square kilometers at the start of the century to over 25 million today. That’s more than 9% of the world’s oceans.
However, scientists with access to the unblinking eyes of satellites have found that many of these supposed protected areas are still being targeted by industrial fishing fleets. The new research shows the pitfalls of relying on simply declaring new reserves as a way to meet numerical targets, like the widely-touted goal of protecting 30% of the ocean by 2030.
But it’s not all bad news. There are hints that strict, enforced protections might help ensure these places live up to their promises. And some of the same high-tech tools used by these scientists could help.
“Fisheries monitoring must be strengthened and made more transparent,” wrote Raphael Seguin, an ecologist at the University of Montpelier in France, and lead author of one of two studies on the issue that appeared last week in Science.
Seguin and colleagues scrutinized more than 6,000 protected areas along the world’s coastlines. These spots represented just 17% of the area covered by such reserves, because many of the largest ones are far from shore. But the spots closer to land often encounter the heaviest fishing pressure. And they also fall under the gaze of the European Union’s Sentinel-1 satellites, equipped with radar that can detect larger boats.
When the scientists checked these satellite images, supplemented with tracking information from beacons required on most large vessels, they found industrial fishing vessels inside nearly half of these reserves between 2022 and 2024. Around two-thirds of those visits were “invisible” to people monitoring the beacons, either because a boat didn’t have one, it’s transmission wasn’t being picked up, or someone had turned it off to avoid detection. But they couldn’t dodge the satellites.
While there is debate about whether all kinds of fishing need to be banned for a healthy reserve, there is widespread agreement among conservation researchers that industrial-scale fishing isn’t compatible with robust protected areas. For instance, guidelines set by the International Union for Conservation of Nature (IUCN) excludes such fishing from any of six types of marine reserves.
In the new study, scientists estimated that vessels spent an eye-popping 24 million hours fishing in these coastal reserves, based on observations paired with a computer model. And that doesn’t account for smaller boats that wouldn’t use beacons or be seen by the satellites. The biggest hotspots tended to occur in wealthier countries which have both active fishing fleets and more of the ocean inside protected reserves, including Japan, the United Kingdom and Spain. Likewise, the places where fishing boats were most crowded together inside protected areas was offshore of Belgium and the Netherlands, as well as China.
At first glance, it might appear that the reserves with the most restrictions did a better job of keeping out fishing. Places that fell in the IUCN’s toughest categories, I and II, tended to have fewer fishing boats. But those places also tended to be harder to reach. When the scientists took into account the size and remoteness of each of the reserves—factors that affect how attractive they are to fishers—the places with tougher rules performed no better. For Seguin, this suggests that policymakers are imposing strict regulations where it’s easy to score “points” for conservation, rather than where fishing pressures are highest.
“This reveals an opportunistic strategy for locating MPAs, often placed in little-fished areas in order to more easily achieve international objectives,” he wrote in a commentary for The Conversation (translated from French).
The findings suggest the results from a companion study published in the same issue of Science might not be as encouraging as they appear. A different group of scientists used similar methods to scrutinize how much fishing was happening inside the most tightly regulated marine reserves.
They found these patches of ocean were largely devoid of fishing boats. In 455 protected areas spanning 3.2 million square kilometers, satellite images revealed just one fishing boat for every 20,000 square kilometers—9 times fewer boats per square kilometer than in unprotected coastal waters.
The overall message, is “that proper investment in protected areas will pay off and that satellite technology can be one of the key tools to help ensure that such investments are kept safe,” wrote Boris Worm, a biologist at Canada’s Dalhousie University who was not involved in either study.
The scientists behind this more upbeat paper wrote that the seemingly contradictory findings compared with the other study might be the result of their use of a more comprehensive rating system, created by the organization ProtectedSeas, to find the most highly regulated reserves.
But part of their analysis suggests the results could also be shaped by the same factors Seguin’s group identified—that these spots weren’t popular fishing spots to begin with. When the group looked at 72 places where there were satellite or beacon observations before and after strict reserves were created, 61 of them had little to no fishing activity before. The results “suggest that many MPAs may have been placed in areas with little prior fishing,” the scientists wrote.
The main exception was the Palau National Marine Sanctuary, where fishing activity fell from 51,000 hours per year to just 215 once the sanctuary was created, the researchers found.
While the work by the two groups takes different views of the current state of marine reserves, they both agree on one thing: tools such as satellites could be powerful ways to watch for illegal fishing inside reserves in the future, and to make sure these aren’t just “paper parks” created for show.
Seguin, et. al. “Global patterns and drivers of untracked industrial fishing incoastal marine protected areas.” Science. July 24, 2025.
Raynor, et. al. “Little-to-no industrial fishing occurs in fully and highly protected marine areas.” Science. July 24, 2025.
Worm, B. “A catch in ocean conservation.” Science. July 24, 2025.
Photo:© Athanassios Lazarides | Dreamstime.com
