About 2% of all fishing gear used around the world ends up polluting the ocean, enough to circle the Earth more than 18 times if tied together, according to a new study. The striking amount has deadly consequences for marine life, the researchers said, and there’s an urgent need to control and limit the amount of fishing pollution.

Commonly known as “ghost gear,” drifting nets, abandoned traps, and other lost fishing equipment can remain in the ocean for centuries, tangling, injuring, and killing many marine creatures in the process. The magnitude of the problem has been challenging to quantify, but this new study provides the first global estimate of the amount of equipment lost every year.

“This lost fishing equipment can cause heavy social, economic and environmental damage. Hundreds of thousands of animals are estimated to die each year from unintentional capture in fishing nets. Derelict nets can continue to fish indiscriminately for decades,” the researchers behind the study wrote in The Conversation. If current loss rates continue, in 65 years there would be enough ghost gear to cover the planet, they said.

Understanding the scale of the problem

For their study, the researchers interviewed over 450 fishers from seven of the world’s largest fishing countries, including the United States, Morocco, Indonesia, and Peru, to find out exactly how much fishing gear enters the global ocean.

They asked fishers how much gear they used and lost every year, and what gear and vessel features could be worsening the problem. This included vessel and gear size, the amount of gear used by the vessel, and whether the gear contacts the seafloor. They then coupled the surveys with data on the amount of commercial fishing globally.

Annual losses included:

• 740,000 kilometers of longline mainlines;
• almost 3,000 square kilometers of gill nets;
• 218 square kilometers of trawl nets;
• and 75,000 square kilometers of purse seine nets.

In addition, fishers were also estimated to lose over 25 million pots and traps and almost 14 billion longline hooks every year, the study found.

In reality, the problem could be even larger, as the study only covers commercial fisheries, leaving out the amount of fishing line and other gear lost by recreational and artisanal fishers. The researchers also left out illegal, unreported, and unregulated (IUU) fishing activities, also known to be an important driver and cause of discarded fishing gear.

Almost 700 species of marine life interact with marine debris, many of which are threatened. A 2016 study found that fishing gear was the main entanglement threat to marine fauna such as sea turtles and marine mammals. Lost fishing gear also has an economic impact on fishers themselves, as every meter of line lost comes with a cost.

The researchers called for further efforts to tackle the problem, suggesting incentives such as reduced loans to net replacements and port receptacles to encourage fishers to return used fishing gear. Technological improvements can also make a difference, such as requirements to mark and track gear and gear maintenance — but pushing for fishing reforms is of utmost importance.

The study was published in the journal Science Advances.