Marine protected areas (MPAs) may prohibit industrial fishing within their boundaries, but they cannot stop fishing gear released elsewhere from drifting inside.
A new global study estimates that drifting fish aggregating devices (dFADs) used by industrial tuna fleets affect more than half of the world’s protected marine areas. Some travel thousands of kilometers before sinking or washing ashore, where they can damage coral reefs, entangle wildlife and leave coastal communities with the burden of removing the debris.
Published in Science Advances in June 2026, the study combined fishing records, published research, an online survey of MPA staff and experts, and follow-up interviews to assess the global distribution, strandings and impacts of drifting FADs in MPAs.
“We were surprised to find that FADs appear to affect more than half of the world’s protected marine area, and that impacts often occurred thousands of kilometers from the original fishing grounds,” study co-author Boris Worm, a marine ecologist at Dalhousie University in Canada, told Mongabay by email.
dFADs are floating rafts deployed by purse-seine fishing vessels — industrial boats that encircle schools of tuna with large nets — to attract skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye tuna (Thunnus obesus).
The devices carry satellite-linked buoys and echo sounders that allow companies to track them and estimate the fish below. But many are later deactivated, abandoned or lost and continue drifting beyond the fishing grounds where they were released.
A 2025 study led by Laurenne Schiller, a marine conservation scientist at Dalhousie University, estimated that tuna fishers deployed 1.41 million dFADs from 2007-2021 that drifted across more than one-third of the world’s oceans. Schiller, who also led the new study, found they traveled well beyond tuna fishing grounds, potentially reaching biodiversity hotspots and protected areas.
Previous studies had already shown that dFADs could enter individual protected areas.
Worm said their new research expanded the analysis from one modeled MPA to protected areas worldwide, using empirical evidence to examine how often dFADs entered them and what impacts managers observed.
The team documented at least 6,324 dFAD strandings across 174 protected areas, including 161 MPAs and 13 shark sanctuaries, in 53 maritime jurisdictions.
Hotspots occurred in the western and central Pacific, western Indian Ocean and the Caribbean Sea. French Polynesia recorded 1,539 strandings, followed by Seychelles with 1,404 and the Maldives with 746.
Around 30% of protected areas with recorded or inferred strandings were in “small island developing states,” where local authorities often bear recovery and disposal costs, according to the study.
Stranded dFADs can break, smother or entangle corals, while their submerged tails can entangle sharks, turtles and other animals. Their plastic and electronic components may persist even when rafts are made mainly from biodegradable materials.
The researchers cautioned that finding a stranded dFAD in habitat occupied by threatened species does not prove direct harm. The effects of devices that sink offshore also remain largely undocumented.
The researchers also examined whether tuna fleets increasingly concentrated dFAD fishing just outside large MPAs to exploit fish crossing their boundaries.
Study co-author Juan Carlos Villaseñor-Derbez, a marine scientist at the University of Miami in the U.S., said this question interested him most.
Using publicly available data, the researchers found that dFAD fishing near the examined MPAs had increased, but at roughly the same rate as fishing farther away.
“This tells us two things,” Villaseñor-Derbez told Mongabay by email. “First, confirmation that dFAD fishing has become more common, which was already known. And second, that fishers are likely not strategically fishing on dFADs near MPA boundaries, at least at the very broad spatial scales at which we were able to measure this.”
The findings do not rule out deliberate deployments near individual MPAs. One industry interviewee, according to the study, said crews sometimes release dFADs near MPA boundaries to attract tuna from protected waters, but available data were too coarse to show how widespread this is.
Villaseñor-Derbez said the lack of public dFAD tracking data remains a major obstacle to more detailed analyses. Real-time locations may need to remain confidential, he said, but companies and regulators could release historical records once their commercial sensitivity has passed.
