Ghost Nets: the Silent Killers

Have you ever walked for a day without noticing a single piece of waste? Have you ever been in remote corners, close to nature and far from humans, while having this dark vision of a bottle or a plastic bag spoiling the landscape? Unfortunately, all this visible pollution is only the minority of the actual amount of waste in the oceans.  

Ocean plastic has gathered lots of attention in recent years, as it should. However, ALDFG (abandoned, lost or discarded fishing gear) makes up a huge chunk of that problematic plastic but as it receives less media attention, the issue of ghost fishing is unknown to many. This fishing gear is designed for one purpose: catching and killing sea life. And it continues to do so if it is lost at sea. The plastics that make up most of the nets in the ocean today take around 600 years to break down and even then will remain in the ocean as microplastics.  

A report from the international non-profit World Animal Protection (WAP) estimates that at least 640,000 tonnes of nets, lines, pots and traps used in commercial fishing are lost or discarded in the sea every year (the same weight as 55,000 double-decker buses).

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Once there, it can harm all kinds of sea life, including turtles, penguins, sea lions, dolphins, whales, and diving shorebirds. The report found that 45% of all the marine mammals listed on the International Union for Conservation of Nature’s Red List of Threatened Species have been killed or harmed by abandoned fishing gear. 

For example, almost 5000 derelict nets, removed from Puget Sound through retrieval programs, were entangling over 3.5 million marine animals annually, including 1300 marine mammals, 25,000 birds, and 100,000 fish. 

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A recent study of the “great Pacific garbage patch”, an area of plastic accumulation as large as Texas in the north Pacific, estimated that it contained 42,000 tonnes of mega plastics, of which 86% was fishing nets. Ghost gear is estimated to make up 10% of ocean plastic pollution but forms the majority of large plastic littering the waters. One study found that as much as 70% (by weight) of macroplastics (in excess of 20cm) found floating on the surface of the ocean was fishing related.  

The deadly effects of ghost nets can be felt far from their point of origin. Ghost nets drift with ocean currents for years, or even decades. As they travel huge distances, they continue to catch and kill marine animals in a process called “ghost fishing”. Entanglement in ghost nets can lead to exhaustion, suffocation, starvation, amputations of limbs and, eventually, the death of a marine animal. Entangled fish often act as bait, attracting larger predators such as turtles, sharks, and dolphins, which may themselves become entangled in the same net, therefore creating a vicious circle and negatively impacting the marine ecosystem. Lost fishing gear, or so-called ‘ghost gear’ is among the greatest killers in our oceans, and not only because of their numbers. 

A drifting ghost net might eventually become so heavy due to its catch that it sinks to the bottom of the ocean. On the seabed, smaller ocean dwellers start feeding on the entangled marine animals, which, along with natural decomposition, reduces the weight of the net to the extent that it floats back up to the surface. Once the ghost net is drifting with the ocean currents again, it starts its cycle of ghost fishing, sinking and floating back up all over again. Due to the durability of modern fishing nets, this circle of devastation can continue for decades. 

Image: Recovered nets and consumer plastic on the deck of S/V Kwai. Ocean Voyages Institute, 2020

Amongst the effects on marine life, ghost nets can also impact humans. There is a danger to humans swimming, surfing and diving in the oceans and perhaps a little ironically, ghost nets are also a menace, and financially painful, for local fishermen. Nets get entangled in boat propellers, reducing manoeuvrability and ghost gear has caused an estimated 5-30% decline in some fish stocks, which would otherwise form part of the catch. Further to these problems, gear replacement and repair costs also negatively affect fisheries in a variety of ways, including loss of fishing time or the financial impact of replacing lost gear. It is therefore also in the fishing industry’s interest to help ensure fishing gear is returned to shore safely, where it can be reused, repaired or recycled. 

The giants are also affected! 

Whales are often victims of ghost nets. They ingest the nets and can die a slow painful death, for example from starvation. When North Atlantic right whales migrate along North America’s eastern seaboard, they find fishing lines in their path. Today 83% of the population shows signs of entanglement, a leading cause of death for this endangered species. Fishing for crabs and lobsters involves placing traps (also called pots) on the ocean floor, which are marked using a surface buoy that’s connected to the traps using a sturdy line. These lines routinely harm whales; they cut into flesh and impede the whales’ diving, surfacing for air, and feeding.  

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Why do ghost nets end up in the ocean? 

Illegal fishing 

  • If a fishing vessel is fishing in an illegal area or using illegal gear and is in danger of being caught, nets may be cut off or thrown overboard. 
  • Unlikely to be using marked gear. 

Economic causes 

  • Proper disposal of discarded fishing nets can be very costly and some fisheries are not able to afford it. Dumping nets into the sea may be their preferred alternative. For example, Korea has a buy-back program where fishermen get money for returning their nets but in many countries you have to pay because it’s considered industrial waste.  
  • High cost of retrieval 
  • When a particularly good catch is made but the boat is full, it can happen that nets are thrown overboard to make room for the catch.  

Environmental influences 

  • Trawl nets towed behind a boat may get caught on corals, wrecks or other obstacles and tear off. 
  • Trammel nets that are firmly anchored to the bottom of the sea can be torn out of their mounts and drift away by the current in a strong storm. 
  • Nets may go overboard in the event of an accident at sea. 

But there’s hope! Many nets are made out of highly recyclable materials, so instead of ending the lives of hundreds of thousands of animals they could give life to new products. As well as this, there are people all over the world working on solutions to prevent fishing gear from becoming ghost nets in the first place. Keep an eye out for our next blog post, where we’ll talk about some innovative solutions.

Authors: Chris Storey, Amy Kenworthy and Arthur Félétou.

Read more here: 

National Geographic https://www.nationalgeographic.com/animals/article/endangered-north-atlantic-right-whales-thin 

Olive Ridley Project https://oliveridleyproject.org/what-are-ghost-nets 

Ocean Voyages Institute https://www.oceanvoyagesinstitute.org/ 

WAPhttps://www.worldanimalprotection.org/sites/default/files/media/int_files/ghosts_beneath_the_waves.pdf  

Images:

  • Recovered nets and consumer plastic on the deck of S/V Kwai. Ocean Voyages Institute, 2020 
  • Entangled Turtles. Dave Bretherton, Olive Ridley Project.
  • The ghost fishing cycle. Olive Ridley Project.
  • North Atlantic Right Whale getting entangled. Diana Marques, NGM staff. Tania Velin. Art: Joe McKendry. International Fund for Animal Welfare; IUCN

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