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Sea Around Us project newsletter, issue 29, May/June 2005 Forrest, Robyn; Sea Around Us Project May 31, 2005

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SSSS Seeee e aaaa a     AAAA Arrrr r ouououou ounnnn ndddd d     UUUU Ussss sThe Sea Around Us Project NewsletterIssue 29 – May/June 2005The Marine Trophic Index:A new output of the SeaAround Us websiteby Daniel PaulyThe first demonstrationthat the mean trophiclevel of fisheries isdeclining (i.e., that globalfisheries catchesincreasingly consist ofsmaller fish andinvertebrates low in thefood web) occurred in thelate 1990s (Pauly et al.1998). Over the next fewyears, this finding wasreplicated and refined by anumber of authors and thisled to the process, nowknown as ‘fishing downmarine food webs’,becoming widely knownand accepted (review inPauly and Watson 2005). Asa result, the Parties of theConvention on BiologicalDiversity decided, at ameeting held in KualaLumpur in February 2004, touse mean trophic level offisheries catches,  renamedthe  ‘marine trophic index’(MTI), as an indicator ofbiodiversity, specifically ofthe richness and abundanceof large, higher trophic-levelfish species (CBD 2004).This implies that the Parties(i.e., member countries ofthe CBD) will have to reportannually on the MTI of theirfisheries, along with sevenother indicators ofbiodiversity. The point hereis that if the mean trophiclevel of the fisheriescatches (= MTI) from themarine ecosystems of agiven country is steadilydeclining, then thesefisheries are not exploitingthe resources sustainably,whatever one’s definition ofsustainability. As a result, thebiodiversity of theseresources will bethreatened as well.To facilitate reporting to theCBD and other applications,we have incorporated intothe Sea Around Us website(www.seaaroundus.org) aroutine which computesthe MTI from 1950 to thepresent, for any country’sEEZ, Large MarineEcosystem (LME) or HighSeas area (see box on p. 3for summary of how the MTIand related indices arecalculated).Experience indicates thatthe MTI is very sensitive tofisheries catches beingaccurate, and particularlynot being taxonomicallyand spatially over-aggregated. Thus, we areworking on disaggregatingthe catch statistics for manycountries. Until this iscompleted for all countriesfor which this is necessary,we cannot guarantee that thecatch database of the SeaAround Us, mapped bycountries’ EEZ, LME and HighSea areas, will allow accurateMTI trends to be computed.Trends of MTI and relatedindices (see Figure 1 for anexample) are thus offeredmainly for indicative purpose,and must always beinterpreted with caution,especially when theunderlying catch statistics areunreliable.To enable various definitionsof the MTI, particularly MTIcomputed from certain cut-off values of trophic levels toexclude the stronglyfluctuating lower trophic-level fishes (Pauly andWatson 2005), we allow forthe user to identify groups tobe deleted from thecomputation of the MTI. Inmany cases, this will makeapparent a fishing downContinued on page 2 - MTIPage 2Sea Around Us – May/June 2005The Sea Around Us project is a Fisheries Centre partner-ship with the Pew Charitable Trusts of Philadelphia,USA. The Trusts support nonprofit activities in the areas ofculture, education, the environment, health and human serv-ices, public policy and religion. Based in Philadelphia, the Trustsmake strategic investments to help organisations and citizensdevelop practical solutions to difficult problems. In 2000, withapproximately $4.8 billion in assets, the Trusts committed over$235 million to 302 nonprofit organisations. ISSN 1713-5214   Sea Around Us (ONLINE)The Sea Around Us project newsletter ispublished by the  Fisheries Centre at theUniversity of British Columbia. Included withthe Fisheries Centre’s newsletter FishBytes,sixissues of this newsletter are published an-nually. Subscriptions arefree of charge.Our mailing ad-dress is: UBC Fish-eries Centre, LowerMall Research Sta-tion, 2259 LowerMall, Vancouver,British Columbia,Canada, V6T 1Z4. Ourfax number is (604) 822-8934, and our emailaddress is SeaNotes@fisheries.ubc.ca. Allqueries (including reprint requests), sub-scription requests, and address changesshould be addressed to Robyn Forrest, SeaAround Us Newsletter Editor.The Sea Around Us website may be foundat saup.fisheries.ubc.ca and contains up-to-date information on the project.trend that was not visible initially.Ecosystem indicators related tothe MTIBesides a fractional trophic level(see box  on p. 3), which isneeded for computing the MTI,each taxon included in the worldmarine fisheries statistics (species,genus, family, etc.) has anapproximate maximum length(ML, in cm) assigned to it. Thisenables computation of timeseries of mean ML as anotherecosystem and biodiversityindicator - again on theassumption that an ecosystem isnot managed for sustainability ifthe catch extracted from itconsists of ever-smaller species.Thus, mean ML (which on the SeaAround Us website is output onlyin tabular form, see below) iscomplementary to the MTI.Another indicator, like the MTIoutput in graphic and tabularform, is the FiB index, a measureof the ‘balance’ between catchesand trophic level. The FiB index isdesigned so that its valueremains constant if a decline introphic level is matched by anecologically appropriate increasein catch, and conversely forincreasing trophic level (see box,p. 3). Thus, a time series of theFiB index can be useful ininterpreting a series of MTIvalues, as it allows us todetermine whether a decreasein trophic level was ‘worth it’, interms of increasing catches (seeFigure 1). Also, the FiB indexallows assessment of whetherfisheries have been expandinggeographically (the logicinvolved here is detailed in anote available as a pop-upwindow).The FiB index is computed using1950 as a baseline year, but thiscan be changed as required.Also, the FiB index requires ameasure of the transferefficiency (TE) between thetrophic level of an ecosystem,and a default value of 10 % isprovided. The routine allows thisto be changed but, as may beseen, the overall shape of timeseries of the FiB index are littleaffected by the precise value ofthe transfer efficiency.Implementation andprospectsOn the Sea Around Us website,ML and the FiB index can all beaccessed under the ‘Ecosystem’button for any country’s EEZ, LMEor High Sea area. The outputs aretwo graphs (as illustrated inFigure 1) and a table listing thevalues of all indices from 1950sonward. Also, a list of speciesincluded or excluded, and theirmean trophic level andmaximum size, as used in thecomputation, can be printed.Under the ‘Method’ button, anote is provided as a ‘pop-up’MTI - Continued from page 1Continued on page 3 - MTIFigure 1. Time series of MTI and FiB index for the east coast of Canada, 1950-2002.Top: time series of MTI (mean trophic level), showing strong decline, especially inthe 1990s ; Bottom: Corresponding series of the FiB index, indicating that thedecreasing TL were not matched by increasing catches (see text).[Theindices] canall beaccessedunder the‘Ecosystem’button foranycountry’sEEZ, LME orHigh SeaareaPage 3 Sea Around Us – May/June 2005MTI - Continued from page 2We hopethat thisroutine,elaboratedincollaborationwith theCBD, will befounduseful andwe lookforward toyourfeedbackwindow, which explains theconcept presented here andprovides access to peer-reviewed literature on the MTIand related indices.We hope that this routine,elaborated in collaboration withthe CBD, will be found usefuland we look forward to yourfeedback. Notably, we wouldlike in-country collaborators,which would help us (and theircountry) to improve thefisheries statistics upon whichthese indicators are based.Trophic levels (TL) express the position of an animal in a food web, relative to the primaryproducers (which have a definitional TL of 1). TL can be calculated from:TLi =  Σj TLj × DCij                                                               …1)where TLj represents the fractional trophic levels of prey j, and DCij represents the fraction of j in thediet of i. Using catch data, and TL estimates for species (or groups thereof ), mean TL and, hence, MarineTrophic index values, can be computed, for each year k from:Mean TLk =  Σi (Yik x TLi) / Σi Yik             …2)where Yi refers to the landings of species (group) i, as  included in fisheries statistics. [Note that, ideally,mean TL should be based on catches - i.e., all animals killed by fishing (landings + discards) - ratherthan only on the landings included in most fisheries statistics. This is ignored here, where we deal onlywith landings].  Mean maximum length (ML) is calculated similarly to mean TL, by weighting by thecatches.The fishing-in-balance (FiB) index is defined as:FiBk = log[Yk x (1/TE)TLk] – log[Y0 x (1/TE)TL0] …3)where all parameters and subscripts are defined previously, except TE, the mean transfer efficiency(specific to an ecosystem, often set at 0.1), and 0, which refers to any year used as a baseline tonormalize the index. This definition implies that the FiB index:- Does not change (remains = 0) if TL changes are matched by ‘ecologically correct’ changes in catch;- Increases (>0) if: either ‘bottom up effect occurs, e.g., increase in primary production, or if ageographic expansion of the fishery occurs (and the ‘system’ definition has in fact changed);- Decreases (<0) if the fisheries withdraws so much biomass from the ecosystem that its functioning isimpaired.Further details on these indicators and their interpretation are given in the literature cited, and on thewebsite in pop-up windows which present further details on TL and their estimation, and on the MTIand related indicators (www.seaaroundus.org).The Marine Trophic Index andrelated indicatorsReferencesCBD. 2004. Annex I, decision VII/30 The2020 biodiversity target: aframework for implementation, p.351. Decisions from the SeventhMeeting of the Parties of the CBD,Kuala Lumpur,   February 2004.Montreal, Secretariat of the CBD.Pauly, D., V. Christensen, J. Dalsgaard, R.Froese and F.C. Torres Jr. 1998.Fishing down marine food webs.Science 279: 860-863.Pauly, D. and M.L. Palomares. 2005.Fishing down marine food webs: itis far more pervasive than wethought. Bull. Mar. Sci. 76(2): 197-211.Pauly, D. and R. Watson. Background andinterpretation of the ‘MarineTrophic Index’ as a measure ofbiodiversity. Phil. Trans. R.Society:Biological Sciences 360: 415-423.We are pleased to announcethat we have been officiallyinformed that the Board of thePew Charitable Trusts approvedcontinuation of the Sea AroundUs project grant in its lastmeeting.Also, UNESCO has officiallyapproved a project proposal byVilly Christensen to expand hiswork on Large MarineEcosystems.  Details ofthis project soon.FundingnewsPage 4Sea Around Us – May/June 2005Reconstructing the JohnMurray/Mabahiss expeditionby Dawit TesfamichaelExpeditions are a goodsource of bio-geographicalinformation (Palomaresand Mohammed 2005).  Afamous example is theexpedition of Challenger, whichis commonly accepted to haveushered in the birth of modernoceanography. In this article, Ipresent another expedition,done in the west Indian Ocean -the geographic area of my PhDresearch. Both expeditions have alot in common and one stronglink.The John Murray/MabahissExpedition, known for short as theJohn Murray Expedition wasintended to investigate thephysical, chemical and biologicalcharacteristics of the West IndianOcean and adjacent seas. Theexpedition was named after JohnMurray, a Canadian-bornoceanographer, and was largelyfunded by money he bequeathedtwenty years before theexpedition. Murray was a memberof the Challenger expedition andwas responsible for theexpedition’s final report.The John Murray was an Anglo-Egyptian expedition, whichstarted on Sept 3, 1933 from PortAlexandria, Egypt and finishedMay 25, 1934 at the same port(see map). It was carried outaboard the 138’ Egyptian researchvessel, Mabahiss (Arabic for‘research’), rented by acommittee of scientists mainlyfrom the British Natural HistoryMuseum, with chief scientist, R. B.Seymour Sewell.  The expeditioncovered the Red Sea, the Gulf ofAden, the South Arabian Coast,the Gulf of Oman, the Arabian Sea,Zanzibar and the Maldives (seeRice 1986).The vessel was equipped withwater samplers, plankton nets,trawls and dredges. Water,plankton and fish samples weretaken from 209 major and someminor stations over a period of 9months and 3 weeks. At the endof the expedition, 2700 fishspecimens representing 276species had been collected. Thespecimens are kept in the ZoologyDepartment of the BritishMuseum of Natural History.My task was to create anelectronic database of theexpedition, based on publishedreports and web resources. Thedatabase consists of descriptionsof the sampling stations; depth;temperature at the surface anddifferent depths; bottom type;gear used; and salinity. Informationabout stations was obtainedmainly from Sewell (1935).  Dataon fish specimens were obtainedmainly from Norman (1939). Foreach specimen the following dataare given: scientific name, stationsampled, sex, length and life stage.The valid scientific name isaccording to the EschmeyerCatalogue of Fishes(Eschmeyer, 1998). Thedatabase of the British NaturalHistory Museum (http://flood.nhm.ac.uk/cgi-bin/perth/fish/indextaxon.dsml)was used to obtain thecatalogue number of thespecimens.Reconstructing expeditionscan be a painstaking, butworthwhile job.  When I first tookthis assignment, I thought it wouldtake me a month. However, amonth was gone before I waseven halfway, although I amhappy to say I finished it in lesstime than the actual expedition!The database is now available inthe expedition table of FishBase(www.fishbase.org) and from theSea Around Us project(www.seaaroundus.org).ReferencesEschmeyer, W.N. (Ed. ) 1998. Catalog offishes. Special Publication, CaliforniaAcademy of Sciences, San Francisco. 3vols. 2905 pp.Norman, J.R. 1939. Fishes. In: BritishMuseum (Natural History), The JohnMurray expedition 1933 – 1934:Scientific reports. Vol VII, No. 1, pp. 1 -116, London.Palomares, M.L.D. and E.  Mohammed.2005. The natural history of theFalkland Islands traced throughEuropean expeditions. Sea Around Usnewsletter,  Issue 27.Rice, A.L. (Ed.) 1986. Deep-sea challenge:the John Murray/Mabahissexpedition to the Indian Ocean,1933-34. The Chaucer Press Ltd.,Bungay.Sewell, R.B.S. 1935. Introduction and listof stations. In: British Museum(Natural History), The John Murrayexpedition 1933 – 1934:Scientific reports. Vol. 1 (1)  pp.1 – 43, London.Track of the voyage of Mabahiss in the JohnMurray expedition.At the endof theexpedition,2700 fishspecimensrepresenting276 specieshad beencollectedIndianOceanIndiaArabiaAfricaRed Sea


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