Floating Ghost Nets Keep Fishing for Years

The new report comes as nations prepare to gather for next week's World Oceans Conference in Manado, Indonesia, where the restoration of healthy marine environments will be high on the agenda.

The report finds that most fishing gear is not deliberately discarded but is lost in storms or strong currents or results from gear conflicts - fishing with nets, for instance, in areas where bottom traps that can entangle them are already deployed.

A ling cod entangled in a ghost net (Photo by Pete Naylor courtesy REEF)

Gill nets, fishing pots and traps are most likely to "ghost fish," continuing to catch continued fish, turtles, seabirds, and marine mammals, which are trapped in the nets and die, according to the report.

In the largest U.S. estuary, Chesapeake Bay, an estimated 150,000 crab traps are lost each year out of an estimated 500,000 total deployed.

On just the single Caribbean island of Guadeloupe, about 20,000 of all traps set each year are lost each hurricane season – a loss rate of 50 percent. Like gill nets, these traps can continue to fish on their own for long periods of time.

Longlines are more likely to ensnare other marine organisms and trawls are most likely to damage sub-sea habitats.

The problem of abandoned, lost and discarded fishing gear is getting worse due to the increased scale of global fishing operations and the introduction of highly durable fishing gear made of long-lasting synthetic materials, the two UN agencies report.

"There are many ghosts in the marine environment machine from overfishing and acidification linked with greenhouse gases to the rise in de-oxygenated dead zones as a result of run off and land-based source of pollution," said UNEP head Achim Steiner.

"Abandoned and lost fishing gear is part of this suite of challenges that must be urgently addressed collectively if the productivity of our oceans and seas is to be maintained for this and future generations, not least for achievement of the UN Millennium Development Goals,” said Steiner.

Abandoned, lost or discarded fishing gear in the oceans makes up around 10 percent (640,000 metric tonnes) of all marine litter, the report estimates.

"The amount of fishing gear remaining in the marine environment will continue to accumulate and the impacts on marine ecosystems will continue to get worse if the international community doesn't take effective steps to deal with the problem of marine debris as a whole," said Ichiro Nomura, FAO assistant director-general for fisheries and aquaculture.

Sea turtle entangled in a ghost net (Photo courtesy NOAA)

"Strategies for addressing the problem must occur on multiple fronts, including prevention, mitigation, and curative measures," he said.

The report suggests new technologies that could help reduce ghost fishing.

The use of passive acoustic pingers on nets can help prevent cetacean entanglement when fishing and remain active if gear is lost. Experiments in the addition of sound-reflecting substances to netting material are underway.

Designs are being developed that incorporate pieces of cord to nets that function normally during fishing but break when trapped large animals begin to thrash, freeing them.

The addition of magnets to gear can deter sharks from approaching too closely. Sea-bed imaging can be used to avoid undersea snags and obstacles.

In some countries fish traps and pots are constructed with a biodegradable escape hatch that disintegrates when left under water too long, rendering the trap harmless. As this would not necessarily reduce the levels of debris, a reporting and retrieval system should also be adopted, the report advises.

To retrieve lost gear, vessels with GPS can mark locations where gear has been lost, facilitating retrieval, and transponders can be fitted to gear in order to do the same. Improvements in weather monitoring technology can be used to help skippers avoid deploying nets when very bad weather is imminent.

Financial incentives could encourage fishers to report lost gear or bring to port old and damaged gear, as well as any ghost nets they might recover while fishing.

Marine debris on a Hawaiian beach (Photo courtesy NOAA)

Putting disposal bins on docks and providing boats with oversized, high-strength disposal bags for old fishing gear could help achieve proper disposal of old, damaged and retrieved fishing gear. The report finds that most ports do not have facilities on site that allow for proper disposal.

A key recommendation of the report is that vessels should be required to log gear losses as a matter of course. However a "no-blame" approach should be followed with respect to liability for losses, their impacts, and any recovery efforts, the report advises. The goal should be to improve awareness of potential hazards and increase the opportunity for gear recovery.

"Clearly solutions to this problem do exist, and our hope is that this report will prompt industry and governments to take action to significantly reduce the amount of lost or abandoned fishing gear in the marine environment," said Nomura.

Marine litter is separate but related problem. The total input of marine litter into the oceans has been estimated at 6.4 million metric tonnes annually, of which nearly 88 percent comes from merchant shipping.

Some eight million items of marine litter are thought to enter the oceans and seas every day, about 63 percent of which are solid waste thrown overboard or lost from ships.

It has been estimated that currently over 13,000 pieces of plastic litter are floating on every square kilometer of ocean.

Mass concentrations of marine debris in high seas accumulation areas are of particular concern, the report states. In some areas, rafts of debris, including various plastics; ropes; fishing nets; and cargo wastes such as dunnage, pallets, wires and plastic covers, drums and shipping containers, mixed with oil slicks, extend for many kilometers.

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