F I S H and F I S H E R I E S 2006 7 24 34 Fishing down the deep Telmo Morato1 2 Reg Watson2 Tony J Pitcher2 Daniel Pauly2 1 Departamento de Oceanografia e Pescas Universidade dos Ac ores PT 9901 862 Horta Portugal 2Fisheries Centre AERL Building 2202 Main Mall University of British Columbia Vancouver BC V6T 1Z4 Canada Abstract Global landings of demersal marine fishes are demonstrated to have shifted to deeper water species over the last 50 years Our analysis suggests deep water fish stocks may be at serious risk of depletion as their life histories render them highly vulnerable to overfishing with little resilience to over exploitation Deep sea fisheries are exploiting the last refuges for commercial fish species and should not be seen as a replacement for declining resources in shallower waters Instead deep water habitats are new candidates for conservation Keywords deep sea deep water fisheries fisheries crisis global trends Correspondence Telmo Morato Fisheries Centre AERL 2202 Main Mall University of British Columbia Vancouver BC V6T 1Z4 Canada Tel 1 604 822 1636 Fax 1 604 822 8934 E mail t morato fisheries ubc ca Received 4 Mar 2005 Accepted 14 Nov 2005 Introduction 24 Methods 25 Results 26 Global trends 26 Atlantic Ocean 27 Pacific Ocean 28 Indian Ocean 29 Antarctic 29 Mean longevity of the catch 29 Discussion 31 Acknowledgements 33 References 33 Introduction A global crisis in marine fisheries was regarded with scepticism by many fisheries scientists as recently as 10 years ago Today however few dispute worry24 ing trends Pitcher and Pauly 1998 Pitcher 2001 Pauly et al 2002 Christensen et al 2003 Hilborn et al 2003 Pauly and Maclean 2003 Food and Agriculture Organization FAO 2004 Historical data from marine ecosystems clearly suggest that 2006 The Authors Journal compilation 2006 Blackwell Publishing Ltd Fishing deeper T Morato et al overfishing has had for thousands of years a major impact on target species and have fundamentally altered marine ecosystems Jackson et al 2001 Pitcher 2001 including coral reefs Pandolfi et al 2003 A dramatic depletion of large predators Baum et al 2003 Christensen et al 2003 Myers and Worm 2003 has triggered fisheries to target species of lower trophic levels in a process called fishing down marine food webs Pauly et al 1998a More recently fisheries exploitation has spread from coastal areas to the open ocean and a general decline in fish biomass has been reported Baum et al 2003 Christensen et al 2003 Myers and Worm 2003 as a consequence many marine species are of serious conservation concern Casey and Myers 1998 Spotila et al 2000 Baum et al 2003 Sadovy and Cheung 2003 Not surprisingly there has been a decline in global fisheries catches since the late 1980s Watson and Pauly 2001 Zeller and Pauly 2005 at an approximate rate of 0 4 million tonnes per year Nevertheless a global increase of fishing effort and catching power has continued Gre boval 2003 With the decline of shallow coastal waters resources increasing demand and new technology fisheries are evidently expanding offshore e g Christensen et al 2003 Myers and Worm 2003 Pauly et al 2003 and into deeper waters Koslow et al 2000 Garibaldi and Limongelli 2003 FAO 2004 Gianni 2004 The expansion into offshore areas has been well documented for example fisheries targeting oceanic tuna billfishes and their relatives covered the world ocean by the early 1980s Myers and Worm 2003 but the extension into deeper waters is less well analysed While many local examples of fisheries expansion into deeper waters have been reported e g some European Soviet USA Canada New Zealand and Australian fishing fleets see references in Hopper 1995 Moore 1999 Koslow et al 2000 Roberts 2002 we lack a global quantitative analysis Deep water fish resources are generally considered to have high longevity slow growth late maturity and low fecundity Thus they have been considered more vulnerable to exploitation than most species exploited on the continental shelf upper continental slope or in open ocean pelagic ecosystems Merrett and Haedrich 1997 Koslow et al 2000 Deep water stocks can be rapidly depleted and recovery can be very slow although this will not apply to a few deep water species with life history traits comparable to shallow water species Large et al 2003 Whereas previous studies on global trends of fisheries have focused on catch or biomass changes over time e g Christensen et al 2003 Myers and Worm 2003 in this paper we have analysed changes in the mean depth of fishing to test if the predicted expansion into deeper waters can be detected in global landings datasets We also tested for the predicted higher vulnerability of deep water fisheries resources using longevity as the main proxy for vulnerability Methods We used three publicly available databases official landings statistics from the FAO from 1950 to 2001 which are based on reports submitted annually by FAO member states FishBase http www fishbase org an information system with key data on the biology of fishes Froese and Pauly 2004 and the Sea Around Us Project database SAUP http www seaaroundus org which contains estimated maps of global fisheries catches from 1950 to the present The SAUP database includes data from the FAO International Council for the Exploration of the Seas ICES Northwest Atlantic Fisheries Organization NAFO and other sources Watson et al 2004 and was used to compile catch data for high seas areas In this study depth range is defined as the extremes of the depths reported for juveniles and adults but not larvae while common depth is the range where adults are most often found and is more precisely defined as the range within which approximately 95 of the biomass of a species occurs Froese and Pauly 2004 For those taxa not reported to species level the average for the genus or family was calculated using the species most likely to be present at that locality FishBase was used to estimate the average depth of occurrence for most of the 775 different species or groups of marine fishes included in the FAO landings statistics and to gather data on their longevity Average depth of occurrence for taxa identified at species level in the landings statistics was estimated as the mean of the common depth range or as one third of the total depth range In the latter case we assume fish to have a lognormal distribution with depth whose peak in abundance is at one third of their range Alverson et al 1964 Pauly and Chua 1988 We have
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