A team of Korean scientists has invented a biodegradable net that could solve the problem of lost fishing gear that persists in the oceans for decades, known as ghost fishing.
Fishing nets and lines that are lost or abandoned at sea continue to be active long after all trace of them is lost. The most disastrous consequence for the marine environment is what is known as ghost fishing: abandoned fishing nets continue to catch fish and other marine animals for decades, unattended.
Ghost fishing can have considerable commercial repercussions on fish stocks, causing enormous waste (up to 30 per cent of the fish that is landed) that can jeopardise the survival of both the fishing industry and fish populations. Aquatic megafauna (for example turtles, birds and other marine animals) can also become trapped in abandoned fishing gear and die. As if that were not enough, nets discarded at sea contribute to increasing pollution and the accumulation of waste in the oceans, adding to the already high levels of microplastics and releasing toxic compounds (such as lead) that accumulate in the food chain. Gear that remains afloat provides a means by which invasive species can travel long distances and colonise new habitats. And, once sunk, it can damage the seabed ecosystem.
The problem of abandoned gear and ghost fishing has been exacerbated by advances in technology, which have led to the use of synthetic materials that are more buoyant and durable. It can take decades for these materials to degrade, and their impact on the oceans is therefore long-term and large-scale. The problem is more acute when it comes to gillnets. Gillnets, like other passive gear that traps organisms swimming into them, are generally made of nylon and for this reason continue to ensnare fish for many years. Where it is possible to remove these ghost nets, doing so can prove very costly.
In a recent study published in the scientific journal Animal conservation, researchers from the Korean National institute of fisheries science, in collaboration with the Fao, have presented a biodegradable alternative material for gillnets. This new polymer is broken down by microbes present in seawater within two years, which substantially reduces the potential duration of ghost fishing. Moreover, the nets remain economically viable, since the material used delivers a catch rate similar to that of traditional nylon nets.
Experts warn that this invention will not solve all the problems relating to ghost fishing. Biodegradable nets can break and be lost more easily than conventional nets. They are also more expensive, and fishermen may therefore be less inclined to use them. In general, beyond remedies for fishing gear that is lost, preventive measures — which are cheaper — should first and foremost be adopted to reduce the quantity of nets that end up in the sea. Nevertheless, if integrated within a broader management framework that includes strategies for marking lost nets, limiting their loss and improving their retrieval, these new biodegradable materials could play an important role in reducing the duration of the impact of abandoned fishing gear, thereby diminishing their socio-economic and marine conservation costs.
Translated by Francesca Clemente