Using acoustic sonar technology to locate and tackle ghost gear

© Shutterstock / Mohamed Abdulraheen / WWF-Peru

Lurking on the ocean floor, entangled among colourful corals, rocks and sand, or simply floating in the water waiting to set its trap, is something terrifying, ghost gear. Ghost gear is a collective name for any abandoned, lost or otherwise discarded fishing gear found in seas or lakes. 

Every year, 640,000 tonnes of fishing gear is abandoned, lost or discarded in the ocean. This deadly gear accounts for a minimum of 10 per cent of all marine litter and can persist for up to 600 years before eventually disintegrating into toxic microplastics. 

Most discarded fishing gear is composed of plastic. Marine plastic debris impacts 66 per cent of marine mammals, including whales, 50 per cent of seabirds and all species of sea turtles. Across all species groups, ghost gear is most likely to prove lethal. 

© Shutterstock / VisionDive / WWF-Sweden

“Ghost gear is a hugely destructive environmental problem as it continues to ensnare fish unnecessarily and trap marine mammals, birds and other animals, who are thereby subjected to unnecessary suffering and death,” says Théa Jacob, the marine species and sustainable fisheries expert for WWF France. 

Since it’s intentionally designed to capture fish, it’s hardly surprising that fishing gear continues to catch fish and other marine life even after it’s been lost or discarded. This abandoned or discarded fishing gear can continue to catch target and non-target species for years, potentially decimating important food resources and other species.

Ghost gear in the Mediterranean

“The amount of fishing gear lost in the Mediterranean Sea is estimated to be between 2,637 and 3,342 tons per year,” says Théa. “Recent research carried out in several locations of the Mediterranean Sea shows that ghost gear may account for the largest portion of marine litter, with figures reaching up to 89 per cent. However, the full impact of ghost gear is still unknown.”

In the Mediterranean, victims of ghost gear include 35 per cent of birds, 27 per cent of fish, 20 per cent of invertebrates, 13 per cent of marine mammals, and 5 per cent of marine turtles. Ghost gear can also physically impact important marine and nearshore habitats, including seagrass beds and coralligenous (i.e., gorgonians and corals), characteristic of Mediterranean underwater seascapes and crucial nurseries for many species.

Taking action to help eliminate ghost gear

© Gabriele Dederer-WWF

“WWF France is helping tackle ghost gear in the Mediterranean Sea,” says Théa. “Our main goal is to help reduce the amount of lost gear in French Mediterranean waters by using an innovative and efficient way to locate ghost gear: acoustic sonar technology. We are working hand in hand with our colleagues from WWF Germany, who have been working on ghost gear for years using acoustic sonar in the Baltic Sea.”

Sonar technology uses sound waves to explore the ocean. This tool is usually used to develop nautical charts, identify underwater hazards, search for objects such as archaeological sites, or generate maps of the seafloor.

The first step to using sonar technology to locate ghost gear is to identify hot spots. Hot spots are areas where the likelihood of ghost gear presence and impact on species and the seabed ecosystem is high. WWF France works closely with fishers and authorities managing Marine Protected Areas (MPAs) to identify these areas.

© Guillaume Labarde

“We completed the first test in October 2022 in Corsica, where the team used sonar technology to help locate lost nets targeting crayfish,” says Théa. “We searched 900 hectares in six days at sea and found nets at every site.”

They identified 90 net/line targets, which represent, at minimum, tens of kilometres of ghost gear. In October 2023, the team is returning to check on the most significant nets and decide how they should be removed. Additional trips are already scheduled in other French MPAs, to locate ghost gear and work with relevant partners on the best way to remove the gear from the environment.

© Florian Monot

Solutions to stop ghost gear

Three categories of solutions exist for tackling ghost gear. Preventing any fishing gear from being lost at sea is the top priority. Prevention involves everything from building awareness among fishing gear designers of best practices to educating fishers on issues such as proper gear disposal to instituting regulatory measures. It also includes actions such as marking gear and systematic reporting of lost gear. The second involves mitigation measures like the use of biodegradable fishing gear or ropeless gear. The third is curative action which involves locating, identifying, and retrieving ghost gear. 

Launched in September 2015, the Global Ghost Gear Initiative (GGGI) is the world’s largest cross-sectoral alliance committed to driving solutions to the problem of ghost gear worldwide. GGGI is composed of the fishing industry, private sector, corporates, NGOs, including WWF,  academia and governments all focused on solving the problem of lost and abandoned fishing gear worldwide.

“Implementing recycling programs, with relevant sites for disposal, is an important step to help stop ghost gear from ending up in our oceans,” says Théa. “We need to build collective projects with fishers and communities, so we can work together on the reporting, locating and retrieving of ghost gear. Finally, removing the gear that’s already out there, so that we can protect our oceans from this unrelenting and destructive debris, is a key component of eliminating ghost gear.”