New biodegradable nets could contribute to solving ghost fishing

A team of researchers from Korea has developed a new biodegradable net that could help address the issue of lost fishing gear persisting in the oceans for decades, known as ghost fishing.

What is ghost fishing and why is it a problem

All fishing nets, lines and traps that get lost or abandoned at sea continue to operate long after we lose track of them. The main resulting threat for the marine environment is so-called ghost fishing: abandoned floating nets keep catching fish and other marine animals for decades, unattended.

ghost fishing net
Old fishing net lost on the ocean floor near Marseille, France © Getty Images

Ghost fishing can affect commercially important fish stocks, resulting in high wastage (up to 30 per cent of the fish that is brought ashore) that can compromise the viability of both the fishing industry and fish populations. Other marine megafauna (for example, turtles, seabirds or marine mammals) can also get trapped in this derelict gear and die. In addition, discarded nets contribute to pollution and accumulation of debris in our oceans, adding to high levels of microplastics and releasing toxic compounds (lead, for example) that accumulate in the food web. Floating gear also offers a means for invasive species to travel over large distances and occupy non-native habitats. And when it sinks, it can affect the biological communities living on the seafloor.

ghost fishing mola mola
Sunfish, also known as mola mola, trapped in lost fishing net in Cap de Creus, Costa Brava, Spain © Reinhard Dirscherl/ullstein bild via Getty Images

The expansion of ghost fishing

The problem of derelict gear and ghost fishing has become more pressing with the advancement of technology, which has led to the geographical expansion of fishing efforts and the use of synthetic, more durable and buoyant fishing materials. These materials may take decades to degrade, and their impact on the oceans is therefore long term and large scale. This is particularly problematic for gillnets, which trap fish by their gills. Gillnets and other passive gear that capture organisms swimming into them are generally made of nylon and therefore maintain high fishing efficiency for many years. When possible, the removal of these ghost nets can be extremely expensive.

ghost fishing net
Lost fishing net over a reef in Cap de Creus, Costa Brava, Spain © Reinhard Dirscherl/ullstein bild via Getty Images

Biodegradable nets

In a recent study published in the scientific journal Animal Conservation, researchers from the National Institute of Fisheries Science in Korea, in collaboration with FAO, presented an alternative biodegradable material for gillnets. This new polymer gets degraded by microbes after only 2 years in seawater, substantially reducing the potential duration of ghost fishing. At the same time, the nets would remain economically viable, since the material ensures catch rates similar to conventional nylon nets.

Experts caution that this is not the panacea for tackling ghost fishing. Biodegradable nets might break or get lost more easily than standard nets. They are also likely to cost more and, as a result, fishermen may be less inclined to adopt them. In general, in addition to remedies to lost gear, cheaper preventative measures should be put in place to reduce the amount of gear that gets discarded in the first place. However, if integrated into a wider management framework that includes strategies to mark nets, reduce loss and improve recovery, biodegradable materials could play an important role in shortening the impact of discarded fishing gear, thus reducing its socioeconomic and conservation costs.

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