Every year, they decimate hundreds of creatures that populate the seas and oceans: true silent killers! it's about ghost nets. Abandoned or lost, they haunt seabeds and account for about 10% of marine litter. This phenomenon is unfortunately too little known to the public.
Ghost nets are fishing gear such as lines and hooks, sinkers, lures, pots, traps, nets and longlines. their loss is, most often, accidental but this phenomenon is also due to:
• drifting gear with the current, natural disasters like storms,
• Poor equipment maintenance;
• A lack of knowledge of the seabeds (young fishermen).
• Illegal or unregulated fishing activities
Fishing gear has a heavy cost of 15,000 to 20,000 euros. Fishermen have no interest in losing them. Unfortunately, some do not hesitate to discard used nets in the sea because of difficult or non-existent access to disposal or recycling facilities. Others do it maliciously or with the desire to harm.
New fishing techniques are as problematic as fishing with gillnets. These consist of sets of uniform mesh panels that form a large wall suspended vertically in the water. Suspended at the bottom or depth of the water (a drifting gillnet) or anchored at the bottom of the sea (lower gillnet), gillnets catch fish by their gills. They are very effective and particularly destructive.
Trawling involves pulling a large fishing net with heavy weight behind a boat, either halfway or at the bottom. The net seizes or crushes indifferently everything that is in its path. As a result, bycatch is extremely high and nets are often lost due to clashes and clashes on the bottom.
Ghost fishing is the continual capture of fish or other animals such as turtles, seabirds and marine mammals. Once alone at sea, the net will continue to trap animal species that will degrade, attracting predators scavengers. They too will be trapped thus continuing the infernal cycle. The net can therefore continue to fish on its own for months, sometimes for years. Longlines are likely to trap other marine organisms and damage the underwater habitat. This continual fishing generates a big loss of money. In fact, 30% of the world's fishing is done by ghost nets.
They also cause alterations of the marine subsoil. The fishing nets used are, in fact, made of nylon, a very resistant material that takes between 400 and 600 years before breaking down. The nets also prevent the formation and development of corals.
They are also dangerous for navigation because they can cause accidents at sea and damage boats. Divers can also get trapped in ghost nets. The underwater landscapes are also affected. They lose their beauty which is detrimental to tourism.
Fishing gear is, in most cases, expensive, and many fishermen make considerable efforts to recover lost gear. A technology that would help them in this research would be useful, for example, the use of GPS and boats that can identify the location where the equipment was lost and facilitate its recovery. Transponders can follow suit. Progress in weather forecast can help fisherman to not use nets when bad weather is announced.
The manufacture of nets made of biodegradable material could finally be the key to fight against this plague. Several countries have come to the task. In France, we are starting to focus on biodegradable nets In the Hauts-de-France area, the Marine Nature Park of Picardy estuaries and the Opal Sea has launched, in 2018, a test for a future action program .
Research expeditions: Several associations make shipments at sea to recover their fishing nets and then recycle them. The finished products are varied: sunglasses, carpets, furniture, hammocks or skates. The possibilities are limitless. We could eradicate the problem by installing bins directly on the docks or by providing the boats with very large, resistant bags for the old equipment.
The regulation of fishing is an equally important factor. The prohibition of deep fishing beyond 800 meters is a first step. It has, moreover, entered into force for some years in European waters.