Ground-breaking Research Confirms Case for the EU to Close the Deep Sea to Bottom Trawling Below 600 Metres

Date: September 1, 2015

As officials meet this week to consider new EU legislation to manage deep-sea fisheries, a new scientific study highlights a pragmatic solution to protecting one of the most vulnerable environments on earth.

Based on an analysis of the catch of fish in deep-sea research trawl surveys in the northeast Atlantic, the paper, A Scientific Basis for Regulating Deep-Sea Fishing by Depth, published in Current Biology concludes that:

  • The rate of bycatch and discards is likely to increase dramatically below 600m;
  • The number of species impacted increases significantly as well because of the increasing diversity of fish species with depth;
  • The catch of particularly vulnerable species of sharks and rays also increases dramatically below 600m depth;
  • The value of the catch declines.

The authors concluded, “Limiting bottom trawling to a maximum depth of 600 metres could be an effective management strategy that would fit the needs of European legislations”.

The European Commission released a proposal in July 2012 to replace the currently failing regulation for deep-sea fishing in the northeast Atlantic. The EU’s 28 Fisheries Ministers have yet to adopt a position though the European Parliament voted on the new regulation in December 2013. Luxembourg, which currently holds the Presidency of the EU, indicated that the negotiation of a Council position on this legislation is a priority and discussions are scheduled to restart this September on the basis of a draft text which includes a depth-limit below which deep-sea bottom-trawling and bottom gillnetting would be prohibited.

The report’s lead author, Joanna Clarke from the University of Glasgow, in a statement issued by the paper’s publishers, explained that: “The most notable thing to consider about our findings is that the trend in catch composition over the depth range of 600 to 800 meters shows that collateral ecological impacts are significantly increasing while the commercial gain per unit effort is decreasing. Going deeper causes greater and greater damage for a reducing benefit to fishermen and it appears that there would be some very specific conservation benefits to a depth limit at around 600 meters.”

Deep-sea bottom trawling, the process of dragging massive nets affixed to steel plates and cables across the deep seabed, is widely recognized to be the most serious and destructive threat to deep-sea ecosystems in the northeast Atlantic. Moreover, the deep-sea bottom trawl fishery by French fleets off Ireland and Scotland has been shown to catch 100 species or more, most of which are of no commercial value and are discarded. In addition, ground breaking scientific research over the past year has shown that deep-sea fish and deep-sea sediment ecosystems act as major sinks for CO2 but that their ability to do so is diminished by deep-sea bottom trawling.

“Our deep oceans are in serious trouble. Policy-makers must listen to the science and prohibit deep-sea bottom-trawling in areas below 600 meters,” said Matthew Gianni, co-founder and policy advisor to the Deep Sea Conservation Coalition. “The environmental benefits far outweigh economic costs. When member states meet this week in Brussels, they owe it to the citizens of the European Union to support measures that will protect a huge area of the oceans around Europe.”

In addition to a phase out of bottom trawling and gill-netting below 600m, the DSCC is calling on EU member states to protect the deep-sea ecosystems associated with the seabed and ensure sustainable fisheries by:

  • Requiring environmental impact assessments for all deep-sea fisheries;
  • Ensuring that the use of low impact, environmentally sustainable fishing gears is prioritized;
  • Closing areas to bottom fishing where vulnerable marine ecosystems, such as deep-sea corals and sponges, are known or likely to occur;
  • Better managing both the catch and by-catch of deep-sea species.


Notes to editors:
The Deep Sea Conservation coalition is an organisation of more than 70 non-governmental organisations, fishers’ organisations, and law and policy institutes that are committed to protecting the deep sea.

The Report: Current Biology, Clarke et al.: “A Scientific Basis for Regulating Deep-Sea Fishing by Depth” Published August 27th 2015.

The researchers collected data from trawl surveys between the depths of 240 and 1,500 meters in the northeast Atlantic. Those surveys used different gear types at various locations between 1978 and 2013. An analysis of those data revealed a clear transition in catches at depths of 600 to 800 meters, including a significant increase in biodiversity, the ratio of discarded to commercial biomass, and the ratio of sharks and rays to commercial biomass. As the ecological impacts increased, the commercial value per unit of effort decreased. 

Why reform is needed:
The current regulation for the management of EU deep-sea fisheries has failed to maintain most deep-sea stocks inside safe biological limits and to restore some of the most depleted fish populations in the region. It has also failed to protect vulnerable deep-sea marine ecosystems from highly destructive fishing.

Numerous scientific papers and reports from ICES, the EU’s Hermione Project, UNEP and others have consistently identified bottom-trawl fishing as the greatest threat to deep-sea coral and sponge ecosystems.[1]

Beginning in 2004, the United Nations General Assembly adopted a series of resolutions committing nations to take “urgent action” to protect the vulnerable marine ecosystems of the deep sea from the destructive impacts of bottom trawling and other potentially harmful deep-sea fishing.

In 2013, more than 300 scientists called on European governments to phase-out deep-sea bottom trawling.

A review by the European Commission in 2007 concluded, “Many deep-sea stocks have such low productivity that sustainable levels of exploitation are probably too low to support an economically viable fishery”.

In 2010, the International Council for the Exploration of the Sea (ICES) classified the EU’s deep-sea catch to be 100% “outside safe biological limits”.

The International Union for Conservation of Nature (IUCN), in June 2015, released the first European Red List of Marine Species, which classified two of the main fish species targeted by French and Spanish deep-sea trawlers off the Irish and Scottish coasts as Endangered (roundnose grenadier) and Vulnerable (blue ling).


Also provided in:
Spanish | French | German | Portuguese | Italian


Nature – Evidence Supports Trawling Depth Limit
New Scientist – Europe to Discuss Deep-sea Trawling Ban to Protect Biodiversity
SPIEGEL – Fanganalysen: Unter 600 Metern sollte nicht gefischt werden
Europapress – 
La pesca de arrastre aumenta la vulnerabilidad de más especies
Intrafish – EU Consideres New Laws to Limit Deep-sea Fishing
Sciences et Avenir – Plus la pêche est en eau profonde, plus elle cause de dégâts


  • [1] Cefas (2014) Economic Impact Assessment and Alternative Options Appraisal of European Commission Proposals for Specific Conditions to Fishing for Deep Sea Fish Stocks. July 2014. page 38.
  • Clarke et al. (2015) A Scientific Basis for Regulating Deep-Sea Fishing by Depth. Current Biology August 2008.
  • UNGA resolution 64/72, paragraph 119 (a) states as follows: “Conduct the [impact] assessments called for in paragraph 83 (a) of its resolution 61/105, consistent with the Guidelines [the UN FAO International Guidelines for the Management of Deep-Sea Fisheries in the High Seas], and to ensure that vessels do not engage in bottom fishing until such assessments have been carried out;”
  • Pusceddu A., et al., 2014. Chronic and intensive bottom trawling impairs deep-sea biodiversity and ecosystem functioning. Proceedings of the National Academy of Sciences of the United States.
  • Trueman, C. et. al., 2014 . Trophic interactions of fish communities at midwater depths enhance long-term carbon storage and benthic production on continental slopes. Proc. R. Soc. B 281: 20140669.
  • International Guidelines for the Management of Deep-sea Fisheries in the High Seas. Rome, FAO. 2009. 73p. Paragraph 13
  • Report of the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP). The International Council for the Exploration of the Sea. 2008. Pages 70–71. Nieto, A. et al., European Red List of Marine Fishes. IUCN. June 2015