Electronic monitoring could provide data needed to help regulate use of fish aggregating devices.

Fish aggregating devices on board a purse seine vessel in Micronesia. Image Credit: The Pew Charitable Trusts

Every year, hundreds of thousands of pieces of man-made debris are cast adrift on the world’s oceans. This is not random littering; fishermen set the materials afloat to attract fish. These objects, called fish aggregating devices (FADs), are used extensively by purse seine vessels and supporting craft to catch tuna.

Fishermen have known for years that tuna like to gather under floating objects, from logs and mats of seaweed to dead whales. But the trend of systematically making and deploying large numbers of FADs—composed of buoys, synthetic ropes, and webbing that hang up to 80 meters below the surface—took off only in the 1990s. Their numbers have grown ever since, resulting in a largely uncontrolled proliferation of FADs. A study by The Pew Charitable Trusts published in November 2015 estimated that up to 121,000 FADs are deployed annually across the world’s oceans.

Unfortunately, because recovering FADs can be more expensive than abandoning them and making new ones, deserted FADs are adding to a growing pile of marine litter that is polluting the ocean globally. In addition, the objects are contributing to the overfishing of tunas, which are declining in number worldwide—an ominous sign for some of the most economically valuable species on the planet. The seven most commercially important tuna species are worth nearly $42 billion (U.S.) annually, a separate Pew report found. An industry that helps feed the world and supports tens of thousands of jobs should want to protect that resource, not jeopardize it.

FADs attract large numbers of small and juvenile bigeye tuna that have not yet reproduced, further imperiling the future of these populations. In a 2015 study, researchers estimated that 10 percent of FADs in the Atlantic and Indian oceans run aground and that some of them ‰ÛÏcan eventually wash up on coral reefs.‰Û As FADs drift, their webbing can snag and kill marine animals. One study estimated that up to 960,000 silky sharks are killed this way each year.

Purse seine vessels and gear in Ecuador. Image Credit: The Pew Charitable Trusts

Unregulated and growing in number, FADs need oversight

FAD use is largely unregulated around the world, and the international bodies responsible for managing tuna fishing have been slow to respond to the rapid rise in the numbers deployed.

A growing chorus of scientists, fishery managers, fishermen, and conservationists are calling on those organizations to move now to regulate the use of FADs to help depleted populations of tunas recover and to limit marine debris worldwide.

As a start, some scientists and fishery managers recommend that fishing vessels share—with fishing oversight bodies and governments—basic information on FAD use and deployments. To date, the exact numbers of FADs deployed and retrieved have been known only to fishing companies, which don’t share the information.

So far, regulators have taken only small steps. In some ocean areas, international bodies are embracing the use of FADs made of biodegradable materials and designed to reduce the entangling of marine life. However, such improvements are not mandated worldwide, nor do they reduce the overfishing of small and juvenile tunas.

There also has been little progress on developing consistently applied methods of physically marking FADs with unique codes that can be recorded by fisheries observers aboard purse seiners, which could help fishery managers learn more systematically where, when, and how FADs are deployed and used.

Better data will drive improved FAD management

The pathway to solving the many challenges associated with FADs should start with advances in data gathering. Fishing vessels already track their own FADs, using transponders attached to the devices that send data, via satellite, to each vessel. The information includes the FAD’s location and time of transmission. Increasingly, it also includes an indication of how many tuna are gathered underneath the FAD, along with oceanographic data such as sea surface temperatures and current speeds. åÊ

A project led by eight Pacific island countries could serve as a model in collaboration: Using existing satellite technology, the members of the Parties to the Nauru Agreement (PNA), a group of countries in the equatorial Pacific Ocean, are tracking and monitoring FADs electronically, creating what may be the world’s most complete effort to understand the use of this gear.

Please read the accompanying article to this story, ‰ÛÏWhen Fishing Becomes Harvesting: Tracking Fish Aggregating Devices to Reduce Pollution, Poaching‰Û for an in-depth look at PNA’s satellite FAD monitoring in its waters.

Officials found that those data can be simultaneously relayed to the PNA’s Fisheries Information Management System—the platform already in use to manage fishery data.

The countries, home to the world’s largest skipjack tuna fishery, began a large-scale trial of the project earlier this year and asked purse seine vessels fishing in their waters to participate. With the PNA members’ leadership, the commercial fishing industry should step up and contribute to improving the understanding of this gear.

Sharing data with appropriate bodies will help scientists learn more about the impact of FADs, inform more effective tuna management and conservation, and provide a new tool for tracking compliance with conservation measures. It will also likely prove safer and more effective than delegating monitoring to the observers who work on tuna vessels.

Electronic tracking is the future of managing fish aggregating devices. As the market continues to demand responsible fishing practices, the electronic tracking and monitoring of FADs offers yet another level of transparency to the tuna supply chain.

Amanda Nickson directs the global tuna conservation program at The Pew Charitable Trusts in Washington, D.C. Her work focuses on improving the conservation of tuna populations in the Pacific and Atlantic oceans through science-based policy development and advocacy. She can be reached at anickson@pewtrusts.org.

See also, from Earthzine, “When Fishing Becomes Harvesting: Tracking Fish Aggregating Devices to Reduce Pollution, Poaching“