Deepwater sharks in extreme decline: ICES recommends zero catch

10 November 2005 The slow and steady life strategy of sharks may have served them well for millions of years, but now these fearsome fish are under serious threat from a combination of destructive fishing practices. In the marine area covered by the International Council for the Exploration of the Sea (ICES) - the North Atlantic, Baltic and North Sea - over 100 species of sharks and their relatives (together known as elasmobranchs) have been recorded. Yet from the wide diversity of European species, only a few have supported fisheries. As coastal fisheries have become increasingly depleted, a number of European fleets have diversified into deepwater fishing and are now fishing in the ICES area for deepwater sharks, mainly the leafscale gulper shark (Centrophorus squamosus) and the Portuguese dogfish (Centroscymnus coelolepsis). These sharks, known as 'siki' are valued for their meat in French and Spanish markets and, to a lesser extent, for their oil-rich livers. Large numbers (approx. 10,000 tonnes per annum) of deepwater sharks are now being caught, mainly by French and UK trawlers, Spanish-based gill netters registered in UK, Germany and Panama, and Portuguese artisanal longliners. Ireland and Norway have also become involved. The threat to deepwater sharks in the Northeast Atlantic that is currently achieving greatest publicity is that posed by deepwater set nets. (1) Although the European Commission recently drafted emergency measures to close the fishery, the proposal was put on ice after objections by a number of the fishing nations involved. Deepwater sharks are also taken by line fishing. Both of these static fishing techniques can be used in areas where deep sea bottom trawling is not possible, thus removing sharks that would otherwise occupy refuges from trawl fishing. For example, the east coast Australian endemic deepsea gulper shark Centrophorous harrissoni has been reduced to approximately 1% of its original numbers and is Critically Endangered because of the combination of deepwater trawling in trawlable areas and droplining in the un-trawlable areas of its limited range. (2) Sharks are not only caught in target fisheries. Fishers in deepwater areas cannot avoid catching deepwater sharks alongside other fish species, due to their diversity and widespread nature. The quantity of unwanted species of deep-water sharks such as Deania discarded is probably greater than the landings of the leafscale gulper shark and the Portuguese dogfish. In both the bottom trawl and longline fisheries, deep-water sharks can form a significant component of unwanted bycatch. (3) Deepwater sharks are particularly vulnerable to today's fishing practices because they have such very slow reproductive rates – much slower than deepwater bony fish species. An initial assessment of the ICES area in 2000, based on catch from French deepwater trawlers, suggested that in 1998 the combined stocks of Portuguese dogfish and leafscale gulper shark were below 50% of their initial biomass. (4) The ICES Working Group on Elasmobranch Fisheries subsequently pulled together all available data from France, UK, Ireland and Norway. The results confirmed a stark trend – an extreme decline, particularly in Portuguese dogfish, once abundant in deepwater catches. The low reproductive output of the Portuguese dogfish, coupled with the fact that females—including pregnant females dominate the catches, explains this decline. (5) A review into the deep gillnet fishery instigated by the Norwegian Fisheries Directorate concluded that deepwater shark stocks had declined to approximately 20% of their original levels in less than ten years. (6) As a result, the latest ICES report advises zero catch of depleted deep-sea sharks. (7) According to David Griffith, General Secretary of ICES, "Deep-sea fish... are long-lived, slow reproducing fish that can withstand only low levels of fishing pressure. All our evidence indicates that the current fishing pressure on these stocks is much too high. We are particularly concerned about deep-sea sharks such as the Portuguese dogfish and leafscale gulper shark, which are now heavily depleted." (8) Sarah Fowler, co-chair of the World Conservation Union's Shark Specialist Group (SSG) said "The critical problem for deepwater sharks is that of unsustainable exploitation rates focused on species that have, because of their life histories and very low productivity environment, incredibly slow population growth rates - far more so than sharks from shallower more productive environments - and which are therefore unable to replace the numbers taken in fisheries." Commercially-exploited species of deep-sea sharks are among the marine taxa at highest risk of extinction, according to preliminary results from the SSG's Red List assessments. (9) Case studies presented at a deepwater shark workshop in New Zealand prior to the Deepsea Conference 2003 demonstrate that small numbers of vessels operating target fisheries can seriously deplete previously unexploited stocks in just a few years of fishing. Recovery of depleted stocks is likely to be extremely slow because of these species' life history constraints. Although most target fisheries for deep-sea sharks are short-lived because of this pattern of rapid depletion, they will still continue to be taken as bycatch and may ultimately be wiped out by mixed deepwater fisheries. "Deepwater shark fishing is effectively mining. The conservation and management advice for deepwater sharks has to be 'no target fishing'. Large, representative deep-sea Marine Protected Areas, closed to all fisheries, certainly have my strong support," Fowler concluded. Around the world scientists are calling for a halt to one of the destructive fishing practices resulting in the depletion of deepwater sharks – deep sea bottom trawling in international waters. Following up on a statement from over 1,000 scientists signed in 2004 (10), scientists in the UK, Canada and Australia have written to their governments calling on them to support a moratorium on high seas bottom trawling at this year's United Nations General Assembly. (11) Notes: (1) Experts Say Spanish Fishing Devastates Sharks, Environmental News Network, 5 October 2005 A preliminary Investigation on Shelf Edge and Deepwater Fixed Net Fisheries to the West and North of Great Britain, Ireland, around Rockall and Hatton Bank, Theme session on Elasmobranchs (Sharks, skates and rays) paper, ICES Annual Science Conference, September 2005. Download (pdf) (2) The Conservation Status of Australian Chondrichthyans: Report of the IUCN Shark Specialist Group Australia and Oceania Regional Red List Workshop. Cavanagh, R. D, P.M. Kyne, S.L. Fowler, J.A. Musick, and M.B. Bennett (Editors). 2003. The University of Queensland, School of Biomedical Sciences, Brisbane, Australia. 182pp. Download pdf (3) Management considerations of deep-water shark fisheries (Gordon, J.D.M.(1999). In: Shotton, R. Case studies of the management of elasmobranch fisheries. FAO Fisheries Technical Paper. No 378, pp 774-818 (4) Sharks in trouble? ICES article (5) See (4) above. (6) A preliminary Investigation on Shelf Edge and Deepwater Fixed Net Fisheries to the West and North of Great Britain, Ireland, around Rockall and Hatton Bank (pdf) (7) The full report on fish stocks in the northeast Atlantic is available on the ICES website as a series of pdf files, including:
Deep water sharks overview (pdf) Deep water sharks in the NE Atlantic (pdf) (8) Overhaul deep-sea fisheries, sharks in trouble, good and bad news for other fish stocks, ICES press release, 17 October 2005 (pdf) (9) Conclusions of Deepsea Chondrichthyan Workshop, University of Otago, Dunedin, New Zealand, 27-29 November 2003 (Word). (10) Scientists' statement, MCBI website (11) Scientists call on Australia to support the moratorium, DSCC news, 4 November 2005 Scientists Speak Out: Action Urgently Needed in the Deep Seas, DSCC news, 20 October 2005