Fishing down the deepTelmo Morato1, 2, Reg Watson2, Tony J. Pitcher2& Daniel Pauly21Departamento de Oceanografia e Pescas, Universidade dos Ac¸ores, PT 9901-862, Horta, Portugal;2Fisheries Centre, AERLBuilding, 2202 Main Mall, University of British Columbia, Vancouver, BC, V6T 1Z4, CanadaIntroduction 24Methods 25Results 26Global trends 26Atlantic Ocean 27Pacific Ocean 28Indian Ocean 29Antarctic 29Mean longevity of the catch 29Discussion 31Acknowledgements 33References 33IntroductionA global crisis in marine fisheries was regarded withscepticism by many fisheries scientists as recently as10 years ago. Today, however, few dispute worry-ing trends [Pitcher and Pauly 1998; Pitcher 2001;Pauly et al. 2002; Christensen et al. 2003; Hilbornet al. 2003; Pauly and Maclean 2003; Food andAgriculture Organization (FAO) 2004]. Historicaldata from marine ecosystems clearly suggest thatAbstractGlobal landings of demersal marine fishes are demonstrated to have shifted to deeperwater species over the last 50 years. Our analysis suggests deep-water fish stocks maybe at serious risk of depletion, as their life histories render them highly vulnerable tooverfishing with little resilience to over-exploitation. Deep-sea fisheries are exploitingthe last refuges for commercial fish species and should not be seen as a replacementfor declining resources in shallower waters. Instead, deep-water habitats are newcandidates for conservation.Keywords deep-sea, deep-water fisheries, fisheries crisis, global trendsCorrespondence:Telmo Morato, Fish-eries Centre, AERL,2202 Main Mall,University of BritishColumbia, Vancou-ver, BC, V6T 1Z4,CanadaTel: +1 604 822 1636Fax: +1 604 822 8934E-mail: [email protected] 4 Mar 2005Accepted 14 Nov 200524 ! 2006 The Authors. Journal compilation ! 2006 Blackwell Publishing LtdF I S H and F I S H E R I E S , 2006, 7, 24–34overfishing has had, for thousands of years, a majorimpact on target species and have fundamentallyaltered 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; Myersand Worm 2003) has triggered fisheries to targetspecies of lower trophic levels in a process called‘fishing down marine food webs’ (Pauly et al.1998a). More recently, fisheries exploitation hasspread from coastal areas to the open ocean and ageneral decline in fish biomass has been reported(Baum et al. 2003; Christensen et al. 2003; Myersand Worm 2003): as a consequence, many marinespecies are of serious conservation concern (Caseyand Myers 1998; Spotila et al. 2000; Baum et al.2003; Sadovy and Cheung 2003). Not surprisingly,there has been a decline in global fisheries catchessince the late 1980s (Watson and Pauly 2001;Zeller and Pauly 2005) at an approximate rate of0.4 million tonnes per year. Nevertheless, a globalincrease of fishing effort and catching power hascontinued (Gre´boval 2003).With the decline of shallow coastal watersresources, increasing demand, and new technol-ogy, fisheries are evidently expanding offshore (e.g.Christensen et al. 2003; Myers and Worm 2003;Pauly et al. 2003) and into deeper waters (Koslowet al. 2000; Garibaldi and Limongelli 2003; FAO2004; Gianni 2004). The expansion into offshoreareas has been well documented, (for example,fisheries targeting oceanic tuna, billfishes and theirrelatives covered the world ocean by the early1980s; Myers and Worm 2003), but the extensioninto deeper waters is less well analysed. Whilemany local examples of fisheries expansion intodeeper waters have been reported (e.g. someEuropean, Soviet, USA, Canada, New Zealandand Australian fishing fleets: see references inHopper 1995; Moore 1999; Koslow et al. 2000;Roberts 2002), we lack a global quantitativeanalysis.Deep-water fish resources are generally consid-ered to have high longevity, slow growth, latematurity, and low fecundity. Thus, they have beenconsidered more vulnerable to exploitation thanmost species exploited on the continental shelf,upper continental slope or in open ocean pelagicecosystems (Merrett and Haedrich 1997; Koslowet al. 2000). Deep-water stocks can be rapidlydepleted and recovery can be very slow, althoughthis will not apply to a few deep-water species withlife history traits comparable to shallow waterspecies (Large et al. 2003).Whereas previous studies on global trends offisheries have focused on catch or biomass changesover time (e.g. Christensen et al. 2003; Myers andWorm 2003), in this paper we have analysedchanges in the mean depth of fishing to test if thepredicted expansion into deeper-waters can bedetected in global landings datasets. We also testedfor the predicted higher vulnerability of deep-waterfisheries resources, using longevity as the mainproxy for vulnerability.MethodsWe used three publicly available databases; officiallandings statistics from the FAO from 1950 to2001, which are based on reports submitted annu-ally by FAO member states; FishBase (http://www.fishbase.org), an information system withkey data on the biology of fishes (Froese and Pauly2004); and the Sea Around Us Project database(SAUP: http://www.seaaroundus.org), which con-tains estimated maps of global fisheries catches from1950 to the present. The SAUP database includesdata from the FAO, International Council for theExploration of the Seas (ICES), Northwest AtlanticFisheries Organization (NAFO), and other sources(Watson et al. 2004) and was used to compile catchdata for high seas areas.In this study, depth range is defined as theextremes of the depths reported for juveniles andadults (but not larvae), while common depth is therange where adults are most often found, and ismore precisely defined as the range within whichapproximately 95% of the biomass of a speciesoccurs (Froese and Pauly 2004). For those taxa notreported to species level, the average for the genusor family was calculated using the species mostlikely to be present at that locality.FishBase was used to estimate the average depthof occurrence for most of the 775 different species orgroups of marine fishes included in the FAOlandings statistics, and to gather data on theirlongevity. Average depth of occurrence for taxaidentified at species level in the landings statisticswas estimated as the mean of the common depthrange or as one-third of the total depth range. In thelatter case, we assume fish to have a lognormaldistribution with depth, whose peak in abundance isat one-third
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