What Are Ghost Nets?

three turtles entangled in ghost net Maldives

 

The Silent Killers

 

Ghost gear, or ghost nets, are commercial fishing nets that have been lost, abandoned, or discarded at sea. Every year they are responsible for trapping and killing millions of marine animals including sharks, rays, bony fish, turtles, dolphins, whales, crustaceans, and birds. Ghost nets cause further damage by entangling live coral, smothering reefs and introducing parasites and invasive species into reef environments.

 

Graphic describing ghost nets as silent killers

 

In addition, ghost nets affect the sustainability of well managed fisheries by damaging boats and killing species with economic value. They also impact the beauty of shorelines, resulting in expensive cleanup costs and financial loss for the tourism and diving industry.

Find out more about the devastating effect of ghost nets in the Indian Ocean in this short video documentary

 

 

Ghost Fishing

 

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, traveling huge distances while continuing to catch and kill marine animals in a process called “ghost fishing”. Historically, fishing gear was made from naturally occurring materials such as coconut, palm leaves, jute, or bamboo, which broke down quickly in the oceans. But over the past 60 years, fishers around the world have switched to gear made from synthetics such as nylon, polypropylene, and polyethylene. Those plastics are extremely resistant to ultraviolet radiation and may remain in the marine environment a very long time without degrading.

Entanglement in ghost nets can lead to exhaustion, suffocation, starvation, loss of limbs, and, eventually, 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.

 

Shark entangled in a ghost net Maldives

 

The Destructive Ghost Fishing Cycle

 

 

Graphic describing the ghost fishing cycle

 

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 again drifting with the ocean currents, 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.

 

Watch the short animation below to learn more about the threat of ghost fishing

 

 

Why Do Ghost Nets End Up In The Ocean?

 

Research is ongoing to better understand why ghost nets end up in the ocean, yet the cause and magnitude of the negative impact of ghost nets on the economic and ecological resources in the Indian Ocean remains unknown.

The Olive Ridley Project focuses on identifying the key factors contributing to ghost nets in the Indian Ocean, some of which are:

  • Bad weather conditions;
  • Catch overload;
  • Snagging on the bottom;
  • Poor gear maintenance;
  • High cost of retrieval;
  • Fishery conflicts or vandalism;
  • Poor or no access to disposal or recycling facilities;
  • Illegal or unregulated fishing activities;
  • Destructive fishing techniques.

 

ghost net drifting in Indian Ocean

 

Problematic Fishing Techniques That Create Ghost Nets

 

Many fishing techniques and practices are destructive to the marine environment by causing over-fishing, massive by-catch, damage to the sea bottom and coral reefs, and ghost fishing. Trawling and the use of gillnets, purse seine and FADs (Fish Aggregating Devices) are some of the problematic fishing techniques that create ghost nets. Pole and line, the primary fishing technique in the Maldives, is a low impact and sustainable fishing technique.

 

Gillnets
Fishing by drifting gill-net

Click on the infographic to enlarge.

The dominant fishing gear in the Indian Ocean is gillnets. Gillnets  contributes as much as 30-40% of the total catch in artisanal and semi-industrial fisheries.

Gillnets are sets of panels of uniform mesh size, which form a large net-wall hanging vertically in the water. Suspended in the top- or mid-depths of the water (a drift gillnet), or anchored to the seafloor (bottom gillnet), gillnets trap fish by their gills. They are very effective – and particularly destructive.

 

Trawling
Fishing by trawling

Click on the infographic to enlarge.

Trawling involves dragging a large fishing net with heavy weights behind a boat, either mid-water or across the bottom. The net indiscriminately catches or crushes everything in its path. Consequently, by-catch is extremely high and nets are often lost due to snagging on the bottom.

Trawling is a common fishing technique in India and Sri Lanka.

 

 

Purse Seine
Fishing by purse seine using DFADs

Click on the infographic to enlarge.

Purse seine is a long wall of netting deployed around a school of fish. When it is pulled tight, it encloses the school of fish (and also any other animals) in a purse-like structure.

Purse seines targets pelagic fish of all sizes, including tuna. They are therefore frequently used in the western Indian Ocean, often in combination with FADs (see below).

 

 

 

Fish Aggregating Devices (FADs)
dFAD-Maldives

Example of a dFad found in the Maldives. ©Guy Stevens|Manta Trust

Fish Aggregating Devices (FADs) are man-made objects used to improve a vessel’s catch by attracting fish beneath them. FADs are usually a square of bamboo with netting and buoys attached, sometimes with a solar-powered GPS tracker on-board to allow the boat that deployed it to track it. The devices are either in a static location or deployed in the open ocean as drifting devices (dFADs).

dFADs frequently drift with the currents in Maldivian waters. Some have even been traced back to specific boats operating in the Western Indian Ocean.

 

 

 

 

 

Actively Fighting Ghost Nets

The Olive Ridley Project is actively fighting ghost nets in the Indian Ocean on several fronts. Since February 2015 we have physically removed 120 ghost nets and documented 185 turtle entanglements in the Maldives. Our team of Community Outreach Officers and Field and Project Coordinators focus on educational outreach and organize talks and workshops in local communities and schools. We work with local fishers to develop ways to minimise and reuse fishing gear. Our Marine Turtle Rescue Centre in Baa Atoll has rehabilitated more than 25 turtles rescued from ghost nets in Maldives since opening in February 2017, out of which most have been released back into the wild.

Through research, we are still searching for the answers to the following questions:
  • What is/are the major source(s) for the nets we find in the Maldives?
  • How long can ghost nets remain in the oceans?
  • Why are Olive Ridley sea turtles, and particularly juveniles at such a risk?
  • What breeding population are these turtles from?
  • Do turtles released from a ghost net survive long term?
  • How can we prevent these nets from entering the Indian Ocean?
  • What can global consumers do to help mitigate this problem?

 

Huge ghost net removed by crane Maldives

 

One of the greatest obstacles the Olive Ridley Project probably faces, is knowing just what to do with the vast quantity of ghost gear collected and finding ways to recycle end of life fishing nets. We have recently embarked on an exciting partnership with Seher Mirza, a textile researcher at the Royal College of Arts. Our partnership with her will enable us to reuse ghost gear in creative community projects in Pakistan.

As part of his PhD at the University of Derby, our founder and CEO, Martin Stelfox, has been exploring different techniques to age drifting ghost nets found in the Maldives.  A reliable technique to estimate the age of ghost nets in combination with ocean current modelling programs, could finally give us a better understanding of drifting paths, turtle interaction, and possibly the origin of ghost net loss.

Marine fishing is vital in providing communities around the world with protein and a source of income. The Olive Ridley Project aim to work with fisheries to prevent ghost nets from entering the Indian Ocean in the first place. We hope that our research results will prompt changes in net and gear designs,  as well as influence fishing legislation.

 

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