Ghost Nets: The Ocean’s Silent Killers

What are ghost nets?

Anyone with even a passing interest in marine conservation knows that overfishing is one of the greatest threats to the health of our oceans. But many fewer people know that a staggering 5 percent of the annual global commercial catch can be attributed to ghost nets — fishing gear that has been lost, discarded or abandoned at sea. Barely visible in low light, these nets are found drifting in open ocean or snagged on the sea floor. They are responsible for the deaths of millions of sea creatures every year. Animals that are caught in the nets suffer injury, infection and often, amputation. Those that must return to the surface to breathe die of suffocation, while those that don't die slowly of starvation.

According to a report issued by the Food and Agriculture Organization and the U.N. Environment Program, it is estimated that ghost nets account for 10 percent of all oceanic litter, which translates to 640,000 tons of lethal equipment lost at sea. The increased use of synthetic materials in fishing equipment over the past five decades has exacerbated the problem significantly. Whereas nets made of hemp or cotton may once have disintegrated after only a short time at sea, modern nets made of nylon and other plastics take centuries to degrade, if at all. In that time, they can be travel great distances via ocean currents, leaving a trail of destruction in their wake. The extent of this destruction is hard to comprehend — in the Puget Sound alone, ghost nets are believed to kill more than 500,000 marine animals every year.

The Damage Done

Specific types of fishing gear wreak specific kinds of havoc. Among the worst culprits are gill nets, great vertical walls suspended from floats on the surface, or which float upwards from anchors on the sea floor. Once lost or abandoned, these nets continue to catch marine creatures indiscriminately, including fish, turtles, dolphins, seabirds, sharks and more. Eventually, the net sinks under the weight of its victims, until they decay or are eaten by other creatures, and the net is free to float back towards the surface and begin its deadly cycle all over again.

Crab traps and lobster pots are equally destructive, albeit on a smaller scale. The first animal trapped acts as bait for the next, in a vicious circle that continues indefinitely. Crab and lobster traps are particularly deadly because they are so easily lost. On the Caribbean island of Guadeloupe, for example, approximately 50 percent of all traps deployed are lost every hurricane season.

Although gill nets and crustacean traps are arguably the worst ghost gear in terms of directly catching and killing marine creatures, other types of equipment cause severe indirect damage. Lost trawling nets, for example, sink to the seafloor and cover great expanses of the substrate with their crushing, immovable weight. In sensitive areas, one net can do untold damage, perhaps by smothering coral reefs or disrupting fragile sea grass beds. Ghost nets have a detrimental human impact as well in terms of financial loss to commercial fisheries, and to those areas who depend upon healthy reefs for sustenance fishing or income from tourism. Nets that float into shipping lanes can also cause damage to passing vessels, and may be responsible for maritime accidents as a result.

Causes and Solutions

When seeking a solution to the problem of ghost nets, it is important to acknowledge that most equipment is not deliberately discarded. Instead, fishing gear is sometimes lost in bad weather, breaks as a result of unintentional catch overload, or becomes irretrievably caught on the seafloor. Sometimes, however, the fishermen are at fault. For example, if fishermen do not properly maintain their equipment, or if they abandon nets while illegally fishing. In many countries, there are no facilities for appropriately discarding broken or unwanted fishing gear, and the threat of high retrieval costs may discourage some fishermen from reporting equipment losses.

The report issued by the Food and Agriculture Organization and the UNEP recommends using financial incentives to encourage fishermen to report lost gear, or to retrieve any equipment that they happen to find while at sea. Other suggestions include prioritizing the creation of proper disposal bins in ports across the world, where fishermen can safely discard damaged equipment, as well as the introduction of an obligatory logging system whereby all vessels are legally required to register the loss of any fishing gear. The latter would be implemented with the understanding that registering a loss would not render the fishermen in question liable. Instead, the purpose would simply be to increase the success rate of subsequent recovery efforts.

Ultimately, the answer to the ghost-net problem lies in technology. It is hoped that improved technology will not only limit the impact of lost fishing gear, but that it may also limit the amount of equipment lost in the first place. More accurate weather forecasting will allow fishermen to avoid deploying nets and traps in bad weather; while better seafloor imaging could help commercial outfits to select fishing grounds free from underwater obstacles that could snag or damage their equipment.

When losses inevitably do occur, improved GPS technologies make it easier to pinpoint the location, thereby aiding recovery efforts. Most importantly, scientists are working to develop materials that are both durable and biodegradable, so that the impact of lost gear can be mitigated. In some areas, such equipment is already in use, including crab pots supplied with an escape hatch constructed of a biodegradable material that disintegrates after only a short time in the water.

Inventions like these provide a spark of hope for the future, a hope that the ghostly threat of lost and discarded fishing equipment may one day be eradicated.

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