- Drifting fish aggregating devices, or dFADs, are widely used by tuna fleets to gather and catch fish, but they can drift into marine protected areas without vessels crossing the boundary.
- A new Science Advances study found that dFADs have likely interacted with 53% of the global MPA network by area and stranded in 174 protected areas, including sites that harbor at least 490 at-risk species.
- The problem exposes a weakness in ocean protection: MPAs can regulate fishing boats inside their boundaries, but they are less equipped to manage mobile industrial gear that crosses those boundaries, sinks, breaks apart, or washes ashore.
- The costs often fall on MPA managers, island communities, and conservation groups, making dFADs a test of whether fishing governance can assign responsibility before protected areas become cleanup sites for other people’s gear.
For a marine protected area, a line on the map is supposed to carry legal weight. It tells fishing vessels where they may not go. It tells managers where their authority begins. It tells governments what they have promised to protect.
In the open ocean, that line can be hard to defend. Fish move through it. Currents cross it. Plastic and lost gear drift into it. A reserve may be closed to fishing vessels and still receive the debris of industrial fishing.
A recent paper in Science Advances shows how serious that problem has become for one widely used fishing technology: drifting fish aggregating devices, or dFADs. These are floating rafts, often fitted with satellite buoys and echosounders, that help purse seine fleets find and catch tuna. Tuna and other species gather around floating objects. For fishing companies, dFADs make a mobile and unpredictable ocean easier to search.
For protected areas, they create a different problem. A dFAD can be deployed outside a reserve, drift into it, aggregate fish, entangle wildlife, break apart, sink, or wash ashore on reefs and beaches. It can do this without a vessel crossing the boundary. It can also do it without being visible to managers, since buoy data are usually controlled by fishing companies.
Lauren Schiller and her co-authors analyzed dFAD drift tracks, stranding records, and interviews with experts and practitioners. They found that dFADs have likely interacted with 53% of the global MPA network by area and stranded in 174 protected areas. Those places are home to at least 490 at-risk species. The hotspots include the central Pacific, the western Indian Ocean, and the Caribbean.
The study raises a practical question for ocean protection: what can MPAs actually protect against?
The answer depends partly on the threat. MPAs can reduce fishing pressure when rules are clear, boundaries are known, and enforcement has the staff, boats, budget, and political backing to act. They can protect spawning grounds, rebuild depleted populations, reduce habitat damage, and give ecosystems a chance to recover. The strongest evidence comes from areas that are well designed, well managed, and highly protected.
Many MPAs fall short of that standard. Some exist mainly on paper. Others have rules but limited enforcement. Some have staff and patrols but too little money to monitor a vast area. The MPA Guide, published in Science, tried to bring more precision to this field by distinguishing between areas that are fully or highly protected and those that allow more extractive use. That distinction matters because a target such as protecting 30% of the ocean by 2030 can conceal wide differences in actual conservation effect.
Capacity matters as much as designation. A global study led by David Gill found that many MPAs lack the staff and budgets needed to deliver ecological outcomes. This is a central problem in conservation. Legal designation can move faster than the institutions and budgets needed to make protection real.
The dFAD problem adds another layer. Even a well-managed MPA may struggle with fishing gear that drifts in on its own. The vessel may remain outside the protected area. The device may have no visible owner. The debris may arrive weeks or months after deployment, far from the fleet that released it. Protection built around controlling human entry is poorly suited to a technology that separates the fishing asset from the fishing vessel.
That leads to a second question: what happens when industrial fishing gear moves across legal boundaries?
In legal and ecological terms, dFADs sit in an awkward space. While they are being tracked and used to aggregate fish, they are active fishing tools. When they are abandoned, deactivated, or lost, they become debris. They are also unlike vessels, which can be tracked through vessel-monitoring systems. A dFAD can move through protected waters while the boat that deployed it remains outside.
Some devices are deactivated when they leave fishing grounds because companies no longer want to pay for satellite transmission. Once that happens, managers may have little idea where they are headed. The gear can continue drifting, sinking, or stranding after it has lost commercial value.
The Schiller paper describes several pathways of harm. A dFAD can enter an MPA and aggregate tuna that are later caught after the device leaves the boundary. The authors did not find strong evidence that fleets systematically target large MPAs this way, although interviewees said some captains may deploy near boundaries in hopes of drawing fish. A dFAD can also entangle turtles, sharks, rays, and other wildlife. Older designs often used netting suspended below the raft, creating a web that could trap animals. New non-entangling designs should reduce that risk, and regional fisheries management organizations have begun requiring them.
The effects continue after entanglement risk is reduced. dFADs can strand on coral reefs, dragging ropes and raft structures across living habitat. They can block nesting turtles and hatchlings on narrow beaches. They can break apart into plastic debris. When they sink, they may damage deep or mesophotic habitats that are rarely observed. These impacts are hard to measure because much of the evidence disappears below the surface or lands in remote places.
The issue fits within the wider problem of ghost gear. Abandoned, lost, or discarded fishing gear is among the more damaging forms of marine debris because it is designed to catch and hold animals. Reviews of ghost gear have documented entanglement among marine mammals, reptiles, sharks, and rays. Global estimates of fishing-gear loss show that nets, traps, and lines enter the sea in large quantities each year. dFADs are a specialized part of this larger problem: fishing systems still absorb some gear loss as a cost of doing business, while the ecological and cleanup costs fall elsewhere.
There has been progress. Tuna fisheries and regional management bodies have moved toward non-entangling and biodegradable dFAD designs. Trials of alternative materials have grown. Some fleets and conservation groups have retrieval partnerships. In the Seychelles, FAD Watch has used buoy data to warn island managers when a device is likely to strand, allowing retrieval before it hits a reef. Modeling work by Thomas Imzilen and colleagues suggests that spatial management can reduce dFAD beachings by restricting deployments in areas that are likely to produce downstream strandings. Other work has examined at-sea recovery of abandoned or lost dFADs.
These measures point in the right direction. They also show how much of the burden still falls downstream. A stranded dFAD may have been deployed by a distant fleet, licensed by one jurisdiction, tracked by a private buoy company, certified through a seafood standard, managed through a regional fisheries body, and removed by a small island conservation team. The people cleaning the reef may have received none of the economic benefit from the tuna catch.
That leads to the third question: who pays when protected places absorb the damage?
At present, the answer is often local managers, communities, or conservation organizations. Schiller and her co-authors found that dFAD removals place financial and logistical burdens on MPA staff and nearby communities. The work can require boats, fuel, staff time, disposal capacity, and safe access to remote beaches or reefs. In small island states, waste systems may already be under pressure. A large mass of rope, plastic, bamboo, netting, and electronics is difficult to store, recycle, or discard.
A study from Aldabra Atoll in the Seychelles put numbers to this kind of cost. Removing accumulated marine plastic litter from that remote site was estimated to require millions of dollars and thousands of person-hours. Much of the debris by weight came from fishing activity. Aldabra is a protected place of global importance, yet it receives waste generated by activities outside its own management authority.
This is a cost-transfer problem. If a company deploys a device that later strands in an MPA, the damage is foreseeable. Large numbers of floating devices are released into currents. They are tracked while useful. Some are abandoned or deactivated when they drift away from profitable fishing grounds. Ownership can be hard to prove, which makes accountability harder. The damage remains.
A stronger system would move more responsibility upstream. Deployment limits would reduce the number of devices at sea. No-deployment buffers around vulnerable MPAs and high-risk drift corridors could reduce strandings. Mandatory buoy tracking through the full life of the device would make loss harder to hide. Durable labeling and traceability rules would help managers identify owners when debris strands. Retrieval deposits could be built into each buoy or dFAD purchase, refunded only when the whole device is recovered. Polluter-pays rules could fund cleanup, disposal, and ecological restoration.
Seafood certification also has a role. Many dFAD-using tuna fisheries have been certified as sustainable, yet the Schiller paper shows that dFAD impacts can fall on protected areas far from the point of harvest. Certification systems that assess bycatch, habitat effects, and endangered species impacts need to account for drifting gear after deployment, including what happens when it crosses into MPAs or strands in jurisdictions that did not authorize the fishery.
For MPAs, the lesson is specific. Protection works best against threats that can be governed at the scale of the protected area. It is weaker against mobile pressures, distant industries, and debris whose origin is hidden by poor transparency. That does not weaken the case for MPAs. It clarifies what they need around them.
An MPA is a management commitment as well as a boundary. It needs rules for what happens inside. It also needs rules for industries that can affect it from outside. In the case of dFADs, there are solutions at hand: fewer devices, better designs, full tracking, spatial planning, retrieval before stranding, and financial responsibility when damage occurs.
The ocean will always move across human lines. Fishing governance needs to account for that movement. A protected area should not become the place where other people’s gear becomes someone else’s problem.
Banner image: Linda Ingham with Pacific white-sided dolphin caught in Japanese driftnet, north Pacific. Photo © Greenpeace / Roger Grace
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Cite this article
Rhett Ayers Butler (2026). A marine protected area can ban fishing boats. It cannot stop drifting gear. Mongabay Conservation news. DOI: https://doi.org/10.66709/news-323159Credits
