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Throughout a fishing career that has spanned many decades, José Festas has spent countless hours and euros searching for lost nets. “It’s a huge problem,” says Festas, today the president of Portugal’s national fishermen’s association. Lost nets cost time and money—and waste the lives of fish when they get “caught with no one to pull the net.”

These so-called ghost nets pose a huge threat to marine life. Around 640,000 tonnes of gear goes missing annually, drifting lost in the ocean and killing at least 136,000 seals, sea lions, and large whales. Marine debris also collides with corals, breaking their fragile skeletons, damaging their soft tissue, and ultimately killing swaths of reefs. Now, Portuguese, Spanish, and British organizations and universities, and representatives from the European fishing industry, have teamed up to tackle ghost nets through a project called NetTag. The project has two strategies: invest in new technologies that reduce the number of lost nets, and teach fishermen new practices to cut down on losses.

On the technology side, the team has designed a special underwater acoustic transponder, called the NetTag, that fishers can attach to their nets and other gear. They are also refining a device for a surface vessel that fishers can use to ping the subsea transponders. By measuring the time between when the ship sends out a signal and when the transponder responds, they can home in on a lost net.

Next year, the NetTag project will inch up to full field trials with fishers in Portugal and Spain. The team will also hold workshops and other educational programs for fishers, hammering home the urgent need for change, says Sandra Ramos, a coordinator on the project with the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) in Portugal. Marisa Almeida, another project coordinator also with CIIMAR, believes that change will come by illustrating to fishers a series of best practices. “We will show them actions to reduce marine litter. We will explain to them how to use the technology and how to track and recover lost gear. We will propose ways to bring to land both the litter they produce and the litter they fish,” Almeida says. And at the end of the sessions, they will distribute a booklet outlining best practices that fishermen can consult when they are back on board their boats.

NetTag’s alchemy is equal parts technology and economics, says Jeff Neasham, an electrical engineer at Newcastle University in England. He says the transponders he helped design are tiny—less than the size of a matchbox—and consume around the same power as a smartphone, which means they can survive months attached to a ghost net. The transponders also work using acoustic signals, which lets them be smaller, more efficient, and transmit over longer distances than standard radio wave-based devices.

Dario Pompili, an electrical engineer at Rutgers University in New Jersey who is also working on tracking technology, says the transponders could stand to be improved even more. Pompili says NetTag is a promising endeavor, but it needs to address certain technical challenges. “The three kilometer target range between the surface vessel and the transponder should be more like 30 kilometers to make the application more practical, given the vast body of water these ghost nets usually travel,” he says.

Though there is still a lot to figure out about the best way to mount and use the transponders, Neasham argues that for a cost of about US $330 each the NetTag offers fishers a way to protect assets worth thousands of dollars. “It’s got to be a win-win situation for fishers,” Neasham says. If it is, “the environmental benefit will follow.”

Seasoned piscator Festas is confident the NetTag project will encourage his colleagues to alter harmful tactics, but stresses the equipment needs to be cheap enough for fishers to buy. Festas’s organization is one of two fishing associations participating in the project. He is sanguine about the project’s potential, though he says the technology is only fitting for vessels like trawlers and seiners.

“Festas makes a perfectly valid point,” Neasham says. “The investment in transponder technology might only be justified for fishermen who deploy high-value nets and gear. Small artisanal fishing vessels may not be putting out gear of sufficient value for the transponders to make economic sense.”

The big challenge for his team, Neasham says, is to make the transponders as cheap as possible. But he is quick to add that the environmental argument for their use is strong, and authorities may one day require fishers to use the NetTag or similar technology. If adoption of a device like the NetTag becomes widespread, Neasham says, “90 percent of lost fishing gear might be recovered in the developed world over the next 10 years.”