These Common Fishing Devices Cause Major Problems, But Researchers Are Working to Make Them Better

The vast quantity of fish aggregating devices floating across our oceans is a lesser-known but critical environmental issue for fisheries. These often raft-like structures with submerged webbing are designed to attract fish — since they naturally gather around floating objects like fallen trees, seaweed and even trash. By concentrating fish like tuna, swordfish, and mahi mahi in one area, fish aggregating devices make them easier to catch while also reducing the costs and carbon footprint of fishing.

Sounds good, right? But there’s literally a catch. Sea turtles, sharks, and marine mammals can get caught and injured by the nets, mesh, ropes and lines that make up these devices. Marine mammals and turtles can potentially drown when caught since they need to come to the surface to breathe. And these devices — made from metal, plastics and netting — can pollute and damage marine environments.

Despite the drawbacks, fish aggregating devices are still widely used. The International Seafood Sustainability Foundation is working to fix this unsavory side of seafood. By designing biodegradable and non-entangling fish aggregating devices from materials like bamboo or cotton, it’s offering safer seas for marine life and aligning fishers with a more sustainable future.

Fish aggregating device downfalls

Fish aggregating devices are nothing new. They’ve been used since Roman times, and they’re incredibly abundant. The Pew Environment Group estimates 47,000 to 105,000 fish aggregating devices are sent into our oceans every year. These devices can be moored close to shore, but most are allowed to drift in the open ocean with an electronic buoy transmitting their position. This pays off for fishers since about 38 percent of the global supply of tropical tuna was caught with these devices from 2018 to 2022, according to the International Seafood Sustainability Foundation.

“The issue is that because it's very effective — a very effective fishing tool — fishers have been relying more and more on their fish aggregating devices and changing their strategies towards using more fish aggregating devices,” said Gala Moreno, a research scientist at the International Seafood Sustainability Foundation. “So in the last two decades, there has been a steady increase in their use, and this comes with an impact.”

That impact goes deep. Some of the marine life attracted to the devices can accidentally end up in fishing nets, and most fish aggregating devices are eventually lost, stolen or abandoned — leading to additional problems.

“They've been constructed and still are constructed using netting panels,” Moreno said. “When the fish aggregating devices are deployed at sea, they can entangle sharks and tortoises. But even when they are lost or abandoned by fishers, which happens, they continue producing this mortality, and this is called ghost fishing.”

Research shows lost or abandoned devices can pollute marine environments with microplastics, and about 10 percent wash ashore where they can damage coastal habitats like coral reefs and seagrasses. They may also attract more juvenile tuna than free-swimming schools. Along with large catches, this can lead to the overfishing of some tuna stocks. 

A jellyfish-inspired design

Given these setbacks, the International Seafood Sustainability Foundation set out to improve these devices. 

“To reduce all these impacts, especially ghost fishing and marine pollution, we've been working for 10 years to move towards the use of fish aggregating devices that are made of organic materials,” Moreno said. 

The initial design only lasted half the time the fishers needed them, Moreno said. Collaborating with fishers and oceanographers, the team eventually hit upon a nature-inspired design: the jelly-FAD.

“It drifts like a jellyfish,” Moreno said. “This means that the structure is lighter, the structural stress is reduced and it lasts longer.”

These new devices are constructed from bamboo, clay, cotton, and other natural fibers like manila hemp and fique. With a submerged raft, tail and ropes, only the buoy is made of plastic for flotation. Plus, they don’t have any netting that could entangle marine life, which was recently prohibited in fish aggregating devices in the United States.

The new design lasts around 12 months, which is sufficient since fishers usually use them for around six months, Moreno said. If they’re not retrieved, the biodegradable devices start breaking down at that point.

So far, the foundation has tested these devices on three oceans with a wide range of stakeholders, including conservation and sustainable development organizations, individual fishers, fleets in the Western Pacific and Indian Oceans, an international development organization and other research institutes in Spain.

The challenges of more sustainable fishing 

Despite these tailwinds, it’s not all smooth sailing. For instance, if the biodegradable versions wash ashore, they can damage coral reefs just like their traditional counterparts. But the foundation is working on retrieving all types of fish aggregating devices before they’re stranded, reducing rates of abandonment, and developing best practices to avoid losses in the first place, Moreno said.

Changing habits, especially those mired in tradition, also takes time. “There is a clear gap from the scientific solution to adoption,” Moreno said. “Implementing this jelly-FAD requires a strong collaboration with fleets and with the other stakeholders — for instance, government representatives or key players in tuna regional fishery management organizations.”

But the transition is inevitable.

“The good thing is in the Atlantic Ocean, in the eastern Pacific Ocean and the Indian Ocean, it's now required to transition to [biodegradable fish aggregating devices],” Moreno said. This change is set to occur between 2026 and 2030.