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If the damage being done to deep seas happened on land, there would be uproar

Trawling off the West of Scotland is a causing concern. soilse, CC BY-SA

Some years ago New Yorker magazine printed a cartoon showing a group of high society ladies enjoying an afternoon cup of tea. One lady turns to her neighbour and says, “I don’t know why I don’t care about the bottom of the ocean, but I don’t.”

It’s often argued that we know more about the surface of the moon than we do about the bottom of the ocean, and the New York society ladies perfectly reflect the issue – what’s out of sight is out of mind. Does it matter that we know so little about the largest areas on our planet? Does the deep sea do anything for society? Is it important?

An eclectic group of scientists, fishing representatives and government policy makers is meeting today in Edinburgh to discuss the future of Scotland’s deep seas. Here in the UK the vast majority of deep-sea territory is to the west of Scotland beneath the Atlantic waters that stretch out to Rockall.

Deep sea fishing off Rockall is causing trouble down below. Irish Defence Forces, CC BY-SA

From the surface, the grey expanse of the Atlantic hides a seabed that is far from a featureless expanse of sand and mud. The edge of the continental shelf is strewn with rocks dropped from icebergs at the end of the last glaciation.

These rocks provide a perch for corals and sponges to settle and feed, growing into elaborate colonies that can live for hundreds of years. In some places these corals and sponges cover the seabed, forming deep-water coral reefs and sponge fields.

Secrets of the deep

Although these deep-sea habitats have been known since the 19th century oceanographic expeditions led by Edinburgh’s Charles Wyville Thomson, it is only in the past two decades that researchers have begun to uncover their true extent and diversity.

Using acoustic technologies borrowed from the military and oil industry, marine scientists can now map the seabed in glorious three-dimensional detail. These surveys are revealing not only the diversity of habitats in Scotland’s deep seas, but they also tell us that many have been damaged.

From linear scars cutting across sonar surveys to photographs of smashed coral colonies, evidence has accumulated not only from Scotland but also Ireland, Norway and beyond that deep-water trawl fishing has damaged and in some cases destroyed deep-sea habitats that have developed since the last ice age 10,000 years ago.

But if the fish caught are an essential part of our food security and the populations of deep-sea fish are in good shape, perhaps this is a price worth paying.

The deep seas west of Scotland have been fished for more than 30 years. Populations of deep-water fish have declined. Some deep-sea sharks are now on the International Union for Conservation of Nature’s Red List as “endangered” (Portuguese dogfish and leafscale gulper shark) and “critically endangered” (gulper shark).

Endangered: leafscale gulper shark. Brian Suda, CC BY-SA

Deep-sea fish catches follow characteristic cycles of boom in the early days and bust as the populations are fished down. Why is this? The pace of life in the deep sea is slow. Food rains down from the surface waters and the animals of the deep sea are adapted with slow growth, long lifespans and low rates of reproduction.

For these reasons, the scientific consensus is that for the vast majority of deep-sea fisheries to be sustainable, the harvest rates must be very, very low. Because deep-sea fish live in mixed populations, it is also hard to target any one species of fish without catching others.

Neither are deep-sea fish a significant part of food security. The combined catch of fish from the water column and seabed from the seas around Rockall, Bailey and the Faroe-Shetland channel, which are mostly relatively shallow stocks of haddock and monkfish, add up to just 8% of the value of the catch landed in Scotland.

The policy battle

In March 2013 the European Union’s environment committee voted in favour of a proposal to phase out deep-sea bottom trawling and gill net fishing below 200m, but this measure was subsequently rejected by the fisheries committee. In December when put to a vote, the European Parliament was split but narrowly rejected this proposal.

There are a number of reasons for the close nature of the vote. Not all the fish populations taken at 200m depth are in decline. Some are well managed and are important to vulnerable local communities in areas such as the western Highlands.

There was also the question that if Europe had completely banned deep-water fishing, would some of the vessels have moved further afield to waters off west Africa, or to international waters where there is little or no regulation?

In life there are no simple answers, but we can look for guiding principles and examples of good practice. Good work has been done to create marine protected areas (MPAs) in the deep waters west of Scotland. But these MPAs have been put in place without understanding how the areas are connected ecologically.

The challenges of deep-sea sampling mean that we know very little about how deep-sea animal populations are structured. Larger-scale projects integrating genetics with new models of ocean circulation are needed to fill these major gaps.

But perhaps the most important issue is to celebrate the diversity of deep-sea life and share the information beyond the confines of academic journals and dry policy documents.

People don’t care about things they have never seen and know nothing about. But I expect the New York ladies would object noisily if someone suggested bulldozing the pyramids or felling the last few stands of giant redwoods.

The issues of deep-sea fishing and its sustainability are a global concern, and the debate in Europe has reached a critical point. It now remains to be seen if a scientifically credible and politically feasible agreement can be reached that will allow the European Union to show global leadership in managing its share of the largest ecosystem on Earth.

A Sustainable Future for Scotland’s Deep Seas will take place in Edinburgh at Our Dynamic Earth at 6pm on Monday April 28. To register email

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