Bottom trawling is exhausting deep-sea species

More and more groups of scientists, including those at the ICES, are calling for these fisheries to be closed down.

Press Release Date: August 19, 2013

Location: Madrid


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Oceana fears that deep-sea shark populations are on the verge of collapse.

Cod, hake and red bream are disappearing, while forkbeards, ling, golden-eye perch, orange roughy and tusk are gradually replacing these traditional and increasingly scarcer species. During the last few years, many of these “new species” have been reaching European markets, but if the current rate of overexploitation continues, some of them may well have disappeared before we have even learnt their names.

The nets of bottom trawlers are now reaching depths of almost 2 kilometres, where they catch species that have only recently become known to science. Other fishing gear, such as deep-sea longlines, fixed gill nets and fish pots are also used to catch these species.

The majority of deep-sea fish stocks are overexploited or even exhausted, despite the fact that the fisheries of these species have been operating for barely twenty years.

The deep-sea fisheries were started in the Eighties by part of the old Soviet fleet, which was rapidly joined by many European countries. Today, the main countries involved in these fisheries are Norway and Iceland, followed by the Faeroe Islands, France, Spain, the United Kingdom and Denmark, amongst others, with catches close to 200,000 tonnes per year. The main target species for these fleets are Greenland halibut, grenadiers, tusk, ling, greater Argentine smelt and deep-sea sharks, as well as some crustaceans such as deep-sea shrimp and deep-sea red crab.

Many of these are slow-growing species with low reproductive rates and long life-expectancy, which makes them particularly vulnerable to commercial exploitation.

Various scientific studies have calculated that the acceptable catch levels to avoid overexploiting these fish populations would have to be so low that it would not be economically viable to fish them. A recent study estimated that less than 5% of the virgin biomass of these species would represent an acceptable volume of catches. In other words, it would be unadvisable to catch more than five per cent of the total weight of the original populations. In some cases, such as the orange roughy, the acceptable catch limit may be no more than 1% or 2% of the virgin biomass.

In addition, some of these fisheries give rise to a huge number of accidental catches and discards, thus also endangering other species that are of no commercial interest.

Added to this is the destruction that certain fishing techniques, such as bottom trawling, wreak on the sea bed, which in a matter of seconds can destroy marine habitats that have taken thousands of years to form, such as deep-sea coral reefs.

The International Council for the Exploration of the Sea (ICES) – to which more than 1,600 scientists from the whole North-East Atlantic area belong, including many from the Spanish Institute of Oceanography (IEO) – has raised the alarm and has called for many of the deep-sea bottom trawling fisheries to be closed down, for a drastic reduction in other fisheries, and for them to be prevented from expanding to other areas or stocks. It also claims that the lack of reliable data on the fisheries catches of these species from the countries responsible for these practices is concealing a far greater impact than what is already regarded as worrying.

All the “new species” on which information is available show evident signs of decline, exhaustion or overexploitation. The fisheries of species such as orange roughy, tusk, blue ling and deep-sea sharks are of particular concern.

The scientists have placed a special emphasis on the precarious situation of these sharks, calling for all fisheries of these species to be suspended.

There are several dozen species of deep-sea shark. Normally these species are small in size (little more than a metre long). In European fisheries, Portuguese sharks or dogfish, gulper sharks and freckled catsharks are the main catches. In recent years there have been reports of catches of close to 10,000 tonnes of deep-sea sharks, but it is believed that the true figure could be very much higher.

Recently, scientists from different countries have also appealed to the British presidency of the EU and to other North Atlantic governments to ban deep-sea bottom trawling, one of the main practices to which this situation and the deterioration of marine ecosystems at great depths are attributed.

“At the end of 2004, Oceana raised the alarm about the precarious situation of the Cantabrian anchovy and nobody took any notice; we also asked the EU to ban catches of deep-sea sharks, and once again we were ignored. Now their populations are on the verge of collapse. It is not a question of clairvoyance or making predictions, but simply opening your eyes and taking note of scientific data, something that very rarely happens in EU fisheries policy”, says Xavier Pastor, the director of Oceana in Europe.

Other sharks, such as the spiny dogfish and the porbeagle (or mackerel shark) – which last year Oceana asked the EU to include on the lists of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), are also cited by the ICES as the species in the worst situation, recommending their urgent protection.