Marine protected areas are often framed as one of the most powerful tools we have for ocean conservation. Draw lines on a map, restrict fishing, and biodiversity rebounds. Sounds like a good plan, right? And for reef fish and many coastal species, that story can hold true. But what happens when the species you are trying to protect does not stay put? A new study tracking silky sharks in the Eastern Tropical Pacific forces us to confront an uncomfortable reality: for highly mobile ocean predators, our current approach to protection may be fundamentally wrong.
The Eastern Tropical Pacific (also known as the “ETP”) is a region of extraordinary productivity. Oceanographic and meteorological processes fuel rich food webs that support tuna fisheries, ecotourism, and coastal livelihoods across multiple countries. Yet the same fisheries that drive economic value also generate high levels of bycatch, entangling marine mammals, seabirds, sea turtles, and sharks in their operations. Over the past decade, governments in the region have made ambitious commitments. Between 2010 and 2023, 53 MPAs were created, covering more than 2.5 million square kilometers. At COP26, Panama, Ecuador, Colombia, and Costa Rica pledged to collaborate on even more large-scale protections. But the new tracking data highlights a critical limitation.
Silky sharks (Carcharhinus falciformis) are sleek, fast, and built for life on the move. Named for their smooth(er)-to-the-touch skin, the species is known to roam vast stretches of open ocean, often far from land and far from human sight. That same lifestyle has made them especially vulnerable to industrial fishing. Over the past 30 to 40 years, global silky shark populations have declined by an estimated 47 to 54 percent, driven largely by overfishing and their heavy presence in the international fin trade. Today, they are listed as Vulnerable on the IUCN Red List due to being one of the most commonly caught sharks in pelagic fisheries. In the first assessment of its kind, researchers from institutions including the Guy Harvey Research Institute, Save Our Seas Foundation Shark Research Centre, Charles Darwin Foundation, and the Galapagos National Park Directorate set out to understand how well the existing marine protected areas safeguard silky sharks. Using fin-mounted satellite tags, the team tracked the movements of 40 adult silky sharks over nearly two years after tagging them around Darwin and Wolf Islands in the Galápagos Marine Reserve. The results were striking. “According to our research, silky sharks spent around half their time outside of MPAs and made little use of recently established ones designed to protect areas thought to be a movement corridor of large pelagic species, including sharks,” said Dr. Jeremy Vaudo, of the Guy Harvey Research Institute and Save our Seas Foundation Shark Research Centre at Nova Southeastern University, and lead author of the study. Specifically, on average, silky sharks spent only about 47 percent of their time inside the Galápagos Marine Reserve, an area often held up as a global gold standard for marine protection. “Upon leaving the MPAs, they run the gauntlet of a range of threats including longline and purse-seine fisheries. They are among the most heavily fished shark species in the Eastern Tropical Pacific (ETP) ecoregion and not only are they a major victim of the global fin trade, but their tendency to spend time on the high seas outside of the region’s MPAs also puts them at risk of being incidentally taken as bycatch by industrial fishing fleets.” In fact, they tended to move west and northwest into largely unprotected high seas; some individuals traveled extraordinary distances, with one shark logged nearly 28,000 kilometers in less than two years. According to lead author Vaudo, this suggests that well-intentioned conservation efforts may be missing the areas that matter most.
As Dr. Pelayo Salinas de León, Senior Marine Scientist of the Charles Darwin Foundation for the Galapagos Islands and co-author of the study, says: “Our research also highlights that MPA networks by themselves are not going to be enough to revert ongoing silky shark population declines. MPAs need to be complimented by fisheries policies aimed at ensuring that industrial fishing fleets operating around MPAs, including within biological corridors, are sustainably managed.” That means enforcing bycatch limits, regulating fishing effort, and improving monitoring on the high seas. It also means filling in some of the most basic gaps in our knowledge. We still do not know where silky sharks mate or give birth, so, how can we protect these critical life stages if we do not even know where they occur?
There is some good news, however. The fact that silky sharks spent nearly half their time inside the Galápagos Marine Reserve shows that large, well-enforced MPAs around oceanic islands can provide meaningful protection… at least part of the time. But partial protection is not the same as recovery, especially for a species facing such intense and widespread pressure. One third of pelagic sharks and rays are now threatened with extinction. It forces us to ask if we can really afford solutions that only work half the time. It also makes us look to bigger questions about how we do ocean conservation: Are we too focused on drawing static boxes in a dynamic system? Should protection for migratory species rely more on adaptive management, seasonal closures, or international agreements that follow animals rather than borders? And perhaps most importantly, are we willing to confront the reality that saving species like the silky shark will require changes not just in protected area design but in how we fish, trade, and value the open ocean?
Thus, this new publication is not just about one species slipping in and out of protected zones. It is a test case for how conservation keeps pace with life in the open ocean. If our protections only work when animals stay still, then the most wide-ranging species will always be left exposed. The challenge now is whether our conservation strategies can become just as mobile.