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Sea Around Us project newsletter, issue 64, March/April 2011 Bailey, Megan; Sea Around Us Project Mar 31, 2011

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Sea Around UsThe Sea Around Us Project NewsletterIssue 64 – March/April 2011Atlantic cod:Past and presentby Ashley McCrea Strub and Daniel PaulyContinued on page 2 - CodIn February, Dr Pauly was contacted byMaya Lin, esteemed artist and architectbest-known for designing the VietnamVeteran’s Memorial in Washington D.C.  Sheis creating an exhibit to illustrate severedeclines in species due to humanexploitation, and asked Daniel if the SeaAround Us could provide ideas andinformation for a fish species.  Whenconsidering overfishing and the collapse offisheries, Atlantic cod (Gadus morhua) istypically one of the first species thatsprings to mind. Cod occurs throughoutthe North Atlantic, along the shores of thefirst countries to develop industrialfisheries, notably England.  The differentcod stocks, (e.g., in the North Sea), aregenerally in parlous states, and those of theNorthwestern Atlantic, off the coast of theUnited States and Canada, are noexception. Indeed, the collapse of easternCanadian stocks off the coast ofNewfoundland in 1992 had devastatingeconomic, social and ecologicalconsequences still visible today.At the end of the last ice age, nearly 10,000years ago, the availability and expansion ofcapelin and herring following the retreat ofsea ice provided an abundant food sourceenabling the proliferation of Atlantic cod inthe Northwest Atlantic (Rose 2007).  Thegreat abundance of this predator inecosystems had a dominating influenceover the community. Historical recordsindicate that massive populations of thispredominantly bottom-feeding specieswere targeted by fisheries as early as the15th century (Hutchings and Myers 1994).Technological advances allowed fisheriesfor cod to develop from hook-and-line tocod traps in the 1860s, the latter becominglarger and more efficient over time.  Thetraps were then complemented by gillnets, but the key change was theintroduction of bottom trawling early inthe 20th century in New England as well asduring the mid-20th century in EasternCanada.  As the vessels supporting thesevarious domestic operations grew in sizeand power, distant-water factory trawlers,mostly from Europe, but some from as faras East Asia, were added to the fishery andgenerated catches in excess of 800,000tonnes in the late 1960s and early 1970s.However, Atlantic cod is a relatively long-lived, slow growing species whoseproductive capacity could not keep upwith the increasing rate of mortality dueto fishing.  As the great majority ofspawning adults were packed into ships’freezers, catches began to decline. By 1975,Canada and the United States declarednational jurisdiction over what laterbecame their 200 nautical-mile ‘ExclusiveEconomic Zones’,  indirectly claimingownership over the dwindling cod stocksand forcing out foreign fleets.  Thereduction in fishing, and recovery of codthat followed, was short-lived as overlyoptimistic fishery management measuresand excessive subsidization led to record-low levels of biomass and a resultantfishing moratorium on the largestCanadian stocks in 1992.  Despitesignificantly reduced fishing pressure,most stocks of cod in the NorthwestAtlantic are still struggling to rebuild, andremain classified as ‘overfished.’To help Maya Lin with the creation of herart exhibit, we conducted a study to helpus better understand the extent ofoverfishing and the recent state of AtlanticPage 2Sea Around Us – March/April 2011The Sea Around UsProject newsletter ispublished by theFisheries Centre atthe University ofBritish Columbia.Six issues of thisnewsletter arepublished annually.Subscriptions are freeof charge.Our mailing address is: UBC FisheriesCentre, Aquatic Ecosystems ResearchLaboratory, 2202 Main Mall, Vancouver,British Columbia, Canada, V6T 1Z4. Our faxnumber is (604) 822-8934, and our emailaddress is SeaNotes@fisheries.ubc.ca. Allqueries, subscription requests, and electronicaddress changes should be addressed toMegan Bailey, Sea Around Us NewsletterEditor.The Sea Around Us website may be foundat www.seaaroundus.org and contains up-to-date information on the Project.TThe Sea Around Us Project is a scientific collaborationbetween the University of British Columbia and the PewEnvironment Group that began in July 1999. The PewEnvironment Group works around the world to establishpragmatic, science-based policies that protect our oceans, wildlands and climate. Pew also sponsors scientific research thatsheds new light on the dimensions of and solutions to theproblems facing the global marine environment. Despitesignificantlyreduced fishingpressure, moststocks of cod intheNorthwesternAtlantic are stillstruggling torebuild, andremain classifiedas ‘overfished.’Cod- Continued from page 1cod off the eastern coast of Canada and the U.S.,relative to a time when this species was still themost abundant predator in the region. To begin,information regarding the relative abundance ofAtlantic cod from the northern coast of Labradorto Cape Hatteras, North Carolina was obtainedfrom the global fisheries database developed andmaintained by the Sea Around Us Project at theFisheries Centre, University of British Columbia.Using historical spatial distribution data, as wellas biological data including preferred depth,latitudinal limits and proximity to critical habitat,the likely geographic distribution of over 1000commercially fished species, including Atlanticcod, has been defined (Watson et al. 2004;  Closeet al. 2006).  This database enables the productionof maps illustrating the relative abundance orlikelihood of locating a particular species in aspatial grid of cells measuring 0.5° latitude by 0.5°longitude.  Populating such a map to reflect theactual numbers or biomass of fish present in agiven area during a specific time period is thenpossible given suitable data on fish density.Information regarding the size of the Atlantic codpopulation in approximately 1850 was gatheredfrom an analysis of mid-19th century logbooksmaintained by a handline fleet that fished theScotian Shelf, the centre of the range ofNorthwesternAtlantic cod,prior to theindustrializationof fishing(Rosenberg etal. 2005).  Dueto therelatively lowlevel of fishingpressure, thispopulationwas assumed,for thepurposes ofthis study, to be relatively close to its unfishedmaximum at this time. Using detailed, spatiallyspecific logs, Rosenberg et al. (2005) estimatedthe historical biomass of cod on the eastern andwestern Scotian Shelf (encompassing an area ofover 160,000 km2) as 1.26 million tonnes.Accordingly, the average biomass density of codon the Scotian Shelf in 1850 was approximately8 tonnes per km2.  In the absence of similarinformation for other areas, this estimate ofaverage density was assumed to berepresentative of the entire region consideredhere.  To create a map of the density of codbiomass in 1850, this average density was scaledaccording to spatially specific estimates of therelative abundance of cod, resulting in valuesdefining the density of cod in each grid cellincluded in the study region.To estimate recent biomass, the results of stockassessments conducted by the U.S. NationalMarine Fisheries Service (NMFS) and Fisheriesand Oceans Canada (DFO) were assembled.  Asstock assessments have not been performed forevery Northwestern Atlantic cod stock in thepast year, and to avoid uncertainty associatedwith the most recent assessments, biomassestimates for 2005 were collected for each stock.This process enabled the production of maps ofcod biomass density as well as theapproximation of total biomass for the years1850 and 2005.  As estimates of fish populationsize are typically based partially or wholly onrecords of catches from previous years, thepopulation considered usually includes thoseindividuals that are vulnerable to fishing gear(e.g., age 3-4+ Northwest Atlantic cod) orsexually-mature individuals (i.e. the spawningstock, age 5-7 in the case of Northwest Atlanticcod).  Unless otherwise noted, population sizeestimates calculated in this study refer to theportion of the Northwest Atlantic codpopulation vulnerable to fishing.Continued on page 3 - CodPage 3 Sea Around Us – March/April 2011Cod biomasswas nearly30 timeslower in2005 relativeto 1850...Continued on page 4 - CodIn addition to the total size of the NorthwestAtlantic cod stock during these contrasting timeperiods, the change in size of an ‘average cod’ since1850 due to the effects of (over)fishing was alsoestimated.  Calculating average cod size firstrequired biological information describing the rateat which this species grows in length and weightover its lifetime (Sinclair 2001).  When used inconjunction with the approximate total mortalityrate (due to both natural causes and fishing) during1850 and 2005, the average length and weight of acod during each of these time periods wascalculated1.The maps created as a result of this study providevery different pictures of the abundant codpopulation in the Northwestern Atlantic prior tothe onset of industrial-scale fishing in 1850 (Figure1) and the severely depleted population followingdecades of intense fishing pressure in 2005 (Figure2).  In 1850, the total biomass of Atlantic cod wasapproximately 10.2 billion (10.2 x 106) tonnes.  By2005, it was estimated that this biomass haddecreased by over 96% to 0.36 x 106 tonnes.  Thus,the average density of cod biomass across thestudy region fell from 8 tonnes/km2 to 0.3 tonnes/km2, 3.5% of the initial value.Fishing not only reduces population abundance,but also the size of an average fish in thepopulation.  Thus, in 1850, the average cod morethan 3 years in age would have been about 63 cmin length and weighed 3.0 kg, while the averagemature adult was 78 cm and weighed nearly 6 kg.By 2005, the size of an average cod greater thanage 3 had fallen to 58 cm and 1.3 kg, and anaverage mature cod measured 68 cm and weighed3.6 kg.  It is important to note that the ‘average cod’size in 1850 presented here is conservative and maybe an underestimate of the true average size duringthis time period.  This is due to the fact that moststudies of Northwest Atlantic cod growth wererelatively recent and parameter estimates werebased on fish sampled from stocks already affectedby many years of fishing. Thus, potential fisheries-induced changes in growth rate were notconsidered here.Knowledge of population biomass and averageweight enables an approximation of the number ofAtlantic cod during each time period.  In 1850 thepopulation of Atlantic cod in this region wascomposed of roughly 3.4 trillion (3,400 x 106)individuals, and had decreased by approximately92% by 2005 (i.e., to 285 billion or 285 x 106 cod).  Asyounger, smaller individuals tend to be moreabundant in a population, particularly in the case ofheavily fished populations, merely analyzing thechange in abundance of cod masks the true effectsof overfishing; biomass was nearly 30 times lower in2005 relative to 1850, while the abundance of codwas only 12 times lower in 2005 compared to 1850.At a time when healthy, under-exploited fish stocksappear to be the exception rather than the ruleacross the globe and the ‘shifting-baselines’syndrome has become widespread, numbers suchas those presented here provide a perspective onthe extent of human impacts on species andecosystems, and of what we have lost.  The data andmaps generated as a result of this study will be usedby Maya Lin to guide the design of her upcomingexhibit, providing an exciting vehicle for the SeaAround Us Project to communicate our work to abroad audience.ReferencesClose, C., W. Cheung, S. Hodgson, V. Lam, R. WatsonCod - Continued from page 2Figure 2:  Map of the spatially variable density of Northwest Atlantic codbiomass (including the proportion of the population vulnerable to thefishery) estimated for 2005, following decades of intense fishing pressure.Figure 1:  Map of the spatially variable density of Northwest Atlanticcod biomass estimated for 1850, a time when the stock was assumed tobe similar to its unfished, ‘pristine’  state.  The study region extends fromthe northeastern coast of Labrador southward to Cape Hatteras, NorthCarolina.Page 4Sea Around Us – March/April 2011Cod- Continued from page 3and D. Pauly. (2006). Distribution ranges ofcommercial fishes and invertebrates, p. 27-37In: Palomares, M.L.D., K.I. Stergiou and D. Pauly(Editors). 2006. Fishes in Databases andEcosystems. Fisheries Centre Research Reports14(4).Hutchings, J.A. and R.A. Myers. (1994). What can belearned from the collapse of a renewableresource? Atlantic Cod, Gadus morhua, ofNewfoundland and Labrador. Canadian Journalof Fisheries and Aquatic Sciences 51: 2126-2146.Rose, G. (2007). Cod: An Ecological History of theNorth American Fisheries. Breakwater BooksLTD., St. John’s, Newfoundland. 580 pp.Rosenberg, A.A., W. J. Bolster, K.E. Alexander, W. B.Leavenworth, A.B. Cooper, and M.G. McKenzie.(2005). The history of ocean resources:modeling cod biomass using historical records.Frontiers in Ecology and the Environment 3: 84-90.Sinclair, A.F.  (2001) Natural mortality of cod(Gadus morhua) in the southern Gulf of St.Lawrence.ICES Journal of Marine Science 58:1-10.Watson, R., A. Kitchingman, A. Gelchu, and D. Pauly.(2004). Mapping global fisheries: sharpeningour focus. Fish and Fisheries 5: 168-177.Endnote1 Cod were assumed to grow in length according to the vonBertalanffy growth equation, where  Linf = 118 cm, K = 0.11year-1, and t0 = -0.44  yrs. (Sinclair 2001).  Total length (cm) wasthen converted to weight (kg) using the relationshipW = 0.0081*L3.03 (www.fishbase.org).  The natural mortalityrate (M) was assumed to equal 0.2 year-1.  Fishing mortality (F)for the entire study region was calculated using themean F reported by each stock assessment, weightedaccording to the estimated biomass of each assessedstock, resulting in an estimate of 0.3 year-1 for 2005.Our birthday celebrant, Dr Pauly, was born inpost-war Paris in May 1946 and to this daycarries a French passport (though hewishes to be Canadian sometime in the future).But, he never really lived in Paris, because Daniel’sroller coaster life seems to always involve traveling.In his younger years, these travels wereundertaken as a quest for meaning (which atcertain points in his life included religion), purposeand education leading to a doctorate from theInstitute für Meereskunde in Kiel, Germany. Thisdegree started Daniel’s journey to far and distantlands, e.g., Indonesia (GTZ project), the Philippines(ICLARM, Manila), Peru and Tanzania (FAO/DANIDAtraining courses), New Caledonia, Trinidad andTobago, Kenya and Namibia (FishBase trainingcourses), to name a few. And finally, to Vancouver,where he had the permanent task of being anadvisor to graduate students and leader of SeaAround Us team members since the mid-1990s.Still cranking out a long list of publications like apaper mill and still going places as an invitedspeaker, (the ‘guru’) Daniel, mentor to some of usand professor to many, had an aversion tocelebrating his own birthday for some reason henever really identified. This earned him the name‘KJ’ (for ‘Kill Joy’) among staff at ICLARM in theearly days (because Filipinos like parties andespecially the food!). We at the Fisheries Centre arelucky that Daniel now seems to enjoy thesecelebrations (remember his 60th with that bigevent?). And this year’s birthday (total surprise)bash for our bashful celebrant is unique, his firstbirthday party onboard a cruise! Daniel had noclue that preparations were under way for hisparty, thanks to the deft planning committee(Grace, Aylin), those who avidly put their art andcooking skills to work (Leah, Sarah, Kristin, Fred,Veronica) with special mention to Sandra Paulywho provided us with lunch, those who providedthe materials for the artwork, the poems andbaking paraphernalia, him who told Daniel lies toget him out of the office (Dirk), thephotographers and film makers (Dawit, Dalal,Ling Huang) and to all of you who came to theparty! It was well worth a sunny afternoonout on a boat, wasn’t it!Daniel sails through his 65thonboard the Eloquentby M.L. Deng PalomaresDaniel Pauly celebrates his 65th birthday with his wife Sandra, andsurrounded by Sea Around Us Project volunteers, colleagues,students and post docs.         Photo by Ben Neal.Daniel,mentor tosome ofus andprofessorto many,had anaversiontocelebratinghis ownbirthday...


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