Fishing Down Coastal Food Webs... by Gulf of California Marine Program

FISHING DOWN COASTAL FOOD WEBS IN THE GULF OF CALIFORNIA

ENRIC SALA, OCTAVIO ABURTO-OROPEZA, MIRIAM REZA, GUSTAVO PAREDES AND LUIS G. LĂ&#x201C;PEZ-LEMUS

This electronic reprint is provided by the author(s) to be consulted by fellow scientists. It is not to be used for any purpose other than private study, scholarship, or research. Further reproduction or distribution of this reprint is restricted by copyright laws. If in doubt about fair use of reprints for research purposes, the user should review the copyright notice contained in the original journal from which this electronic reprint was made.

This article was downloaded by: [University of California, San Diego] On: 26 November 2012, At: 10:43 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Fisheries Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ufsh20

Fishing Down Coastal Food Webs in the Gulf of California a

Enric Sala , Octavio Aburto-Oropeza , Miriam Reza , Gustavo Paredes & Luis G. L贸pez-Lemus a

Scripps Institution of Oceanography, La Jolla, CA, USA

Universidad Aut贸noma de Baja California Sur (UABCS), La Paz, Baja California Sur, Mexico c

Gulf of California Program-World Wildlife Fund, Hermosillo, Sonora, Mexico

Scripps Institution of Oceanography, La Jolla, California, USA

UABCS, La Paz, Baja California Sur, Mexico Version of record first published: 09 Jan 2011. To cite this article: Enric Sala, Octavio Aburto-Oropeza, Miriam Reza, Gustavo Paredes & Luis G. L贸pez-Lemus (2004): Fishing Down Coastal Food Webs in the Gulf of California, Fisheries, 29:3, 19-25 To link to this article: http://dx.doi.org/10.1577/1548-8446(2004)29[19:FDCFWI]2.0.CO;2

PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Fishing down coastal food webs in the

Gulf

of California

We usedinformationfrom interviewswith fishers,fisheriesstatistics, and field surveysto document changesin fisheriesand fish assemblages in shallowcoastalhabitatsin the Gulf of

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

California, Mexico. Coastalfood webs in the Gulf of California have been "fished down" dur-

ing the last 30 years--fisheriesshifted from large, long-livedspeciesbelongingto high trophiclevelsto smallshort-livedspeciesfrom lower trophiclevels.In addition,the maximum individuallengthof the landingshasdecreasedabout 45 cm in only 20 years.Although some catchesare stagnantor stillincreasing for somespecies groups,catch-per-unit-effort declined for mostspeciesgroupsafter 1980.Thesedeclineswere associatedto a dramaticincreasein fishingeffort in the region in the late 1970s-early1980s,mostlyin the numberof gillnets. Fishingnot only impactedtarget species,but alsocausedcommunity-widechanges.These resultssuggestthat coastalfisheriesin the Gulf of Californiaare unsustainableand their managementneedsto be reevaluatedwith soundregulatorymeasuresto preventfurther degradationof coastalfood webs,and the concurrentinefficiencyof artisanalfishing. 2002).The totalnumberof localcommercial fishersin thestudyregionis10,600(SEMARNAP,1990-2000), Fisheries catches worldwide havegradually shifted although theseshores arealsousedbyhundreds offishftom long-lived, high-trophic levelspecies to short- ersbasedon mainlandMexico, fromSonorato asfar lived, low-trophiclevel speciesin what has been southas Chiapas.The fisherytargetscoastalfishes called"fishingdownmarinefoodwebs"(Paulyet al. belonging to 25 families 1998a;Baumet al. 2003; Myersand Worm 2003; (Table 1). The most Wormet al. 2003).This patternisconsistent among commonlyusedfishing Enric Sala marineand fteshwater ecosystems at both regional gearis a motoredfiberandlocalscales (Paulyet al. 1998a,1998b,2001).The glassskiff with hand OctavioAburto-Oropeza consequences of fishingdown food websextend linesandgillnets. Miriam Reza beyondthedirecteffects on the targetspecies became Fisheries in Baja Gustavo Paredes the removalof large predatorscan came changes California Sur showed affecting entireecosystems (Esteset al. 1998;Jackson a general pattern of LuisG. Lbpez-Lemus et al. 2001). In Mexico,82% of the fisheries fully increasingcatch since exploitorover-exploit theirtargetspecies (Hernandez 1950 but decreasing Sala is associatedirector,Center for Marine and Conservation,and assistant andKempton2003),butthereareno published anal- catch-per-unit-effort Biodiversity ScrippsInstitutionof Oceanography, La ysesoffisheries shiftsandtheirecosystem effects. Here (CPUE) after 1980 professor,

Introduction

wepresent evidence offishing downmarinefoodwebs in the Gulf of California,a tropicalmarinebiodiversityhotspot(Robertset al. 2002), and address the needforrigorous fisheries management in the region. In spiteof its low humanpopulation density,the

Gulf of Californiais subjectedto intensefishing. Presently, sixspecies of marinefishes(Serranidae and Sciaenidae) arethreatened or at riskof extinctionin the Gulf of California(Musicket al. 2000). Sinceno published analyses of the ecosystem impacts of coastal fishingin the Gulf of Californiaexist,we describe changes overtimein fishcatches andmeantrophic

(Figure1, Secretaria de Marina Secretaria

1950-1960; de Pesca

1970-1980; Ramirez 1988; SEMARNAP

1990-2000). The only exception of CPUE decrease

after

1980

Jolla, CA. He can be reached at esala@ucsd.edu.

Aburto-Oropeza isa researcher, Universidad Autbnomade BajaCaliforniaSur(UABCS),La Paz, BajaCaliforniaSur,Mexico.Rezaisconservation scientist, Gulfof CaliforniaProgram-World Wildlife Fund, Hermosillo,Sonora, Mexico. Paredesis a

graduatestudent,ScrippsInstitutionof Oceanography, LaJolla,California.Lbpez-Lemus is adjunctprofessor at UABCS,La Paz,BajaCalifornia

wasfor a multi-species Sur, Mexico.

BONY FISHES levelof the coastal fisheryin the southern Gulf of Serranidae California. In addition, weattempted to determine the changes in the structure of coastalfishassemblages Lutjanidae Carangidae associated with documented fishingpressure, and Haemulidae changes in thespatial distribution oftheartisanal fleet. Balistidae

SHARKS

RAYS

Alopiidae

Rhinobatidae

Carcharhinidae

Mobulidae

Lamnidae

Myliobatidae Dasyatididae

Echinorhinidae

Scaridae

Heterodontidae

Labridae

We studiedthe coastalartisanalfisheryin Baja CaliforniaSur.Thisfishery operates froma largetown

Mullidae

Kyphosidae

Ginglymostomatidae Odontaspidae Scyliorhinidae

Malacanthidae

Triakidae

ing villagesrangingfrom 13 to 177 people(INEGI March 2004 I www.fisheries.org I Fisheries

in the southern Gulf of California.

Squalidae

Baja California Sur Fisheries (La Paz,154,314inhabitants)and severalsmallfish-

Table 1. Major fish familiestargetedby the artisanalfishery

Sphyrnidae

Figure1. Annualfishcatch(solidcircles) andcatch peruniteffort(CPUE;metrictons/boat) (open squares) in the southernGulfof California.

5harksinclude:37 species from11families (Table 1)caughtinnearshore andoffshore fisheries. Jacks: greenjack(Caranx caballus), Pacific crevalle jack(C caninus), bigeye (•evalle jack(C sexfasciatus), rainbowrunner(Elagatis bipinnula•a), Padticmoonfish (Selene peruviana), and gafftopsail pompano (Trachinotus rhodopus) Redsnapper:Lutjanus peru. Othersnappersinclude:

categoryof medium- and small-sizedgroupers(Figure h "other groupers").The catches of the goliath grouper (Epinephelus itajara)and snappers(exceptred snapper)also showed declines in catch after 1980. Because CPUE declined

over time, the fluctuations and increase of catch in multi-

speciesgroupsmaybe dueto the shift in targetspeciesover time (see Results).These changeswere associated with a strikingincreasein the numberof motoredfishingboatsand gillnets in the region since 1980 (Figure 2) (Secretariade Marina

1950-1960;

Secretaria de Pesca 1970-1980;

SEMARNAP 1990-2000). This patternis similarto that of all Mexican fisheries•in the late 1970snational policies induceda significantmigrationof unemployedfield workers towardscoastalstates,then landingspeakedin 1981, and catchesdeclinedafterwardsin spite of a huge increasein fishingeffort (Hernandezand Kempton 2003).

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

yellowsnapper (Lutjanus argentiven•), dogsnapper (L novemfasciatus), mulletsnapper (L aratus), spotted snapper (L.guttatus), colorado snapper (L.colorado), and barredpargo(Hoplopagrus gunther/). Goliathgrouper:Epinephelus itajara Othergroupersinclude: Methods leopard grouper (Mycteroperca rosacea), spotted sandbass (Paralabrax maculatofasciatus), Because the catchispooledinto coarsetaxonomicgroups Panama graysby (Epinephelus panamensis), in the Gulf of California, fisheriesstatisticsdo not allow calflagcabrilla (E.labriformis), and

culationof the meantrophiclevel (Paulyet al. 2000). Catch

Pacificcreolefish (Paranthias colonus).

5000

1000

Sharks

4000]

0.5

2 200

0.0

600 400 200 0

0.5300 [ 200 1 100 0.0 0+

1000 ,

•

0.0• 2.0

/Other

5ooo ] groupers 1.04000 1/ 3000,,2'

•

600 1

-0.5 800• /

200

0•-•

0.0

1960

0.3 •

- 1.5 6000I

' Goliath grouper

1970

1980

Year

1.0

400

1950

800

1000

400

1.5

600

3000 ] 2000 i

800

Jacks

1990

2000

1.5

7 1.0

- 0.5

0.0

1950

1960

1970

1980

1990

2000

Year

Fisheries I www.fisheries.org I vol 29 no 3

Figure 2. Temporalchangesin the numberof fishers,fishingboats,and gillnetsin the

lengthof eachspeciestimesits relativecontribu-

southern Gulf of California.

tion to the total catch.

To assess the temporalshiftsin the spatialdis4000;

F 12000

tribution

of the artisanal fleet we interviewed

fishersfrom the fishingcampof E1Parditoabout the locationof fishingsitesandtheir useovertime. / Fishers / / / F 10000 Foreveryfishingsiteusedsince1970we estimated a numberof fishingdaysperyear.We then entered 8000 the locationanduseof everyfishingsitefor every time periodinto a geographic informationsystem (ESRI Arc View 3.2a). Maps of fishingintensity wereobtainedinterpolatingthe dataon a matrixof 4000 72 points(on a 1:150,000scalemap). The firsteffectsof fishingarea reductionin the 2000 abundanceand averagesize of target species (Daytonet al. 2002). To determinethe impactsof O• the fisheryon the sizestructureof selectedtarget 1950 1960 1970 1980 1990 2000 species weuseddataobtainedduringvisualcensuses conductedfrom 1998 to 2001 in 21 rocky reefs betweenLa Pazand Loreto(Sala et al. 2002). Fish datasetsfor pelagicspecies suchasdolphinfish(Coryphaena hipincluded140 non-crypticspecies. Thesereefscouldbe purus)and billfish (Istiophoridae),exclusivelyreservedfor the censuses ranked along a gradient in fishing pressure. Fishingpressure was sport fishery,are misreported(Ramirez1988). Furthermore, because not all fishersbelongto organized fishingcooperatives,quantifiedasdensityof fishingboats(Haro et al. 2001;Salaet al. their catchisunderreported. Hereweturnedtraditionalecologi- 2002). Coastalfishingboatscarry3-4 fisherseachandcarryout that effortperboatisconstant. cal knowledgeobtained from interviewswith fishersinto dailyfishingtrips,soweassumed Fishingdownthe foodwebhaseffectson the entirecoastal quantitativeinformationto assess fishingdownand spatialeffort fishassemblage beyondthe directeffecton the targetspecies. We allocation. investigated the changes in the structure (species composition To estimatethe relativecontributionof fish speciesto the andabundance)of the fishcommunityusinga principalcompocatchwe interviewed63 fishersbelongingto 4 fishingvillages nent analysis, whichshowslatitudinaldifferences in the structure locatedin the southernGulf, betweenCaboPulmoandSanJose of the assemblages (Salaet al. 2002).Topreventthesedifferences Island(El Pardito,El Sargento, La Ribera,CaboPulmo).All fishfrom confounding effectswe usedonly datafrom the 11 sitesin erson thesevillages werecommercial fishers, andsoldtheircatch the southernregionof study.The first principalcomponent in the townof La Paz.We selectedthe mostknowledgeable fish(PC1, which accountsfor asmuchof the variabilityin the data erson the basisof previousinterviews.Fishers rangedfrom25 to aspossible)explained86% of the variance,thereforethe scores 67 yearsold, and they provideddata only for the time periods of samplingsiteson PC1 wereconsidered goodproxiesof the when they wereactive.Interviewswith individualfisherswere structureof fish assemblages. We then performeda nonlinear conducted overa periodof oneyear.Fishers wereaskedaboutthe regression betweenfishingpressure and the scoresof eachsamrelativeimportance of eachspecies in the catchin the 1970s, plingsiteon PC1. 1980s,1990s,and 2000.We useda categorical indexof fishing importance from0 to 5, where0 meansthat the species wasabsent Results fromthe catch,and5 that it wasthe mostimportant(by weight). There wasa markedshift in the composition of the catchin We thenestimatedthe changes overtime in the meantrophic the coastalfisheryin the southernGulf of California(Fig.3; Chilevel of the catch (Paulyet al. 1998a).Mean trophiclevel in square= 95.65, df = 16, P < 0.001). Largepredatoryfishessuch marineecosystems rangesfrom 1 (primaryproducers) to 5 (top as sharks,gulf grouper (Mycteroperca jordani), gulf coney predators,e.g., killer whale,humans,Pauly et al. 2000). We (Epinephelus acanthistius), goliathgrouper,andbroomtailgrouper obtainedthe maximumreportedsizeand trophic level of the (M. xenarcha) wereamongthe mostimportantfisheriesin the species in thisstudyfrom Fishbase (Froeseand Pauly2002). We 1970s,but becamerare by 2000. Althoughtotal sharkcatches estimated meantrophic level(TLi)fortimeperiod i bymultiply- havesteadilyincreased in the southernGulf of California,these ing the fishingimportanceindex(I, seeabove)timesthe trophic includeboth coastalandpelagicfisheries (Figure1). Our results level of the individualspecies j, then takinga weightedmean indicatethat the nearshore fisherycollapsed andwassubstituted (modifiedfromPaulyet al. 1998): by an offshorefishery.Catch of other speciessuchas leopard groupers(Mycteroperca rosacea),snappers,and jacks also decreased, but theyarestill commonlycaught.In contrast,some species that werenot appreciated or not targetedin the 1970s, TLi suchas parrotfishes (Scarusspp.),whitefish(Caulolatilus princeps),spottedsnapper(Lutjanusguttams),tilefish (Caulolatilus colonus),have now become When fisherscould not provide informationfor individual affinis),and creolefish(Paranthias have species within a group,we usedthe averagetrophiclevelfor the commontargets.Becausethe largerspeciesof groupers rare in the catch, most of the growthin species in that group.We alsoestimated the meanmaximumsize becomeincreasingly fishinghasbeenrelatedto the leopardgrouper(Figure3). of the catchas the summationof the productof the maximum grouper

3000

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

1000

• T•Iij •Iij

March 2004 I www. fisheries.org I Fisheries

Maximum fish size in the catch decreased45 cm

Discussion and recommendations

from 1970 to 2000, and 33 cm in the 1980salone

The mean trophic level of the catch in Baja CaliforniaSur in the 1970swas4.2, significantly depletionof fishstocksnearfishingvillagesforced higherthan any otherfisheryin the worldat that fishers to moveto fishing siteslocated fartheraway.In time (Paulyet al. 1998a).Thismeansthat themost caughtwere largepredators El Pardito,whilemostof the fishingactivitiesin the importantorganisms while todaythe 1970swereconducted nearthefishing camp(< 10km suchassharksand largegroupers, most important targets are medium-size benthicradiusin average),fishingnowoccursmostly50 km The declinein meantrophiclevelof fromit (Figure5). We assume that thisisrepresenta- feedingfishes. tiveofotherfishinggrounds in theGulfofCalifornia. fishlandedin onlyonedecade(1980s)wasgreater since1950, Meantrophicleveldecreased from4.2 in the 1970s thanthat of the globalmarinefisheries to the largestregionaldeclinesin to 3.8 in 2000,the greatest reductionbeingin the andcomparable (Figure4).

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

The results of the interviews showed that the

1980s.The averagesizeof four abundantspecies Canada, northwestand westerncentral Atlantic, decreased alonga gradientin fishingfor both car- andsouthPacific(Paulyet al. 1998a,2001).These nivorous(leopardgrouper,yellowsnapper, Lutjanus estimates are, however, conservative. The first of a fisheryarereductionin abtnâ&#x20AC;˘dance and argentiventris ; greybargruntHaemulon sexfasciatum ) impacts Because smallindividuals and herbivorous fishes(bluechinparrotfishScarus sizeof the targetspecies. ghobban) (Figure6). We foundsimilarpatternsfor tendto havelowertrophiclevelsthan largeadults (Paulyet al. 1998a,b), the declinein meantrophic most commercial fishes. The structureof fishassemblages changedalong level of the catch musthave been greaterthan the gradientin fishingpressure (Figure7). These reportedhere. These resultsindicate that the results indicate

the

existence

of a threshold

coastal fisheries in the Gulf of California have had

strongerimpactsin the shortterm (around7 fishingboats/km)beyondwhichaverage comparatively than most other fisheriesin the world.Although fishsizeissignificantly reduced andthestructure of there were no rigorousfisheriesstatisticsat the the fishassemblage significantly changed. specieslevel for the Gulf of California,the low variancein the data obtainedfrom independent interviews(Figure3) allowsusto believethat the patternsdescribed in thisstudyareconsistent. Figure3. Shiftsin fishcatchesin the southernGulfof Californiacoastalfishery.Bars Sharkswereamongthe mostimportantspecies representâ&#x20AC;˘ndexof fishingimportance(mean+ S.E.)(seetext for details).Leopard in the catch in the 1970s, but now have been

grouper(Mycteroperca rosacea); gulf grouper(M. jordanl);jacks(Caranxcaballus,C caninusand C sexfasciatus); gulfconey(Epinephelus acanthistius); goliathgrouper (Epinephelus itajara);barredpargo(Hoplopagrus gunthen);broomtail(M. xenarcha); yellowsnapper (Lutjanus argentiventris); dogsnapper(L.novemfasciatus); triggerfish (Balistes polylepis); red snapper(L.peru);parrotfish(Scarusghobban,S. compressus, and S.perrico);oceanwhitefish(Caulolatilus princes); spottedsnapper(L.guttatus);

replacedby smallerspeciesof bony fishes.The declinein nearshore sharkcatches mayberelatedto an offshoresharkfisheryand to the fact that the fishedcoastalsitesmay harbornurseryareas.The possible interactinns betweenthe coastalartisanal

Pacifictilefish(Caulolatilusaffinis);creolefish(Paranthiascolonus).

1970s

1980s

1990s

2000

Sharks

Leopard grouper Gulf grouper Jacks

Gulf coney Goliath grouper Barred pargo Broomtail

Yellow snapper Dog snapper Triggerfish Red snapper Ocean

Parrotfish whitefish

Spotted snapper Tilefish Creolefish

Index of fishing importance 22

Fisheries I www.fisheries.org I vol 29 no 3

4.3

150

4.2

140

fishery,andthe sportandoffshore fisheries targeting pelagicspecies arenotclearandcannotbeexplored at presentbecause datafor the latter isyet unavailable.Nonetheless, the existingdata indicatethat

sharks were abundant inshallow rocky habitats in

1970,wheretheynowhavebeendepleted. The decrease of the meantrophiclevel of the catch is alsoassociated with the disappearance of - 120 some spawningaggregations of large predatory fishes(suchasthe goliathgrouper)in the southern 11o E Gulf of Californiadueto fishing(Salaet al. 2003). The eliminationof theseaggregations accelerates -100 the declinein meantrophiclevelat a rate higher than that causedby a fisherytargetingnon-repro90 ductive individuals.In order to prevent further 2000 declines,fisheriesmanagementin the Gulf of Californianeedsto incorporate the spatio-temporal patternsof fishspawning. The removalof largepredators frommarineecosystems hascascade effects on foodwebs(Esteset al. 1998;Jackson et al. 2001).Our results clearlyindicatethat increasing fishingpressure causes significant changes in the structure of the fish assemblages beyond thedirecteffects ontargetspecies. Thissupports at localscales Paulyet al.'s(1998)hypothesis thatlanding datacanbeusedasecosystem indicators,that is,changes in meantrophiclevelof the catchreflectchanges in the ecosystem. The results of thisstudysuggest thatreducing thepotential density of

130

4.0 3.9 3.8

3.7

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

1970s

1980s

1990s

Figure4. Temporal changesin meantrophicleveland maximumfishsizeof coastalfisherieslandingsin the southern Gulf of California.

Figure 5. Smallscalechangesin fishinggroundsover time aroundEl Parditofishingvillage.Valuesare deviations from meanfishinguse.

1970s

1980s

-1

Mean

10Km hrdito

ito

â&#x20AC;˘ E! Pardito

March 2004 I www.fisheries.org I Fisheries

fisheries management, while boats below 7boats/km 2could -prevent marked reduc-soundecosystem-based offishing gear(mainlygfilnets) tionsin average fishsizeand the degradation of fish theuseofcertaintypes at risk of local assemblages. This meansthat fisheries managementis revised.Protectingthosespecies should bespatially-explicit andregulate effortasa func- extinction(Musicket al. 2000) and the spawning of commercial species (Salaet al. 2002, tionof 1) numberofboatsperfishing campand2) the aggregations 2003) is also necessary. density of boatsonfishinggrounds at anytime. The overallpatterns ofspecies shifts, anddedineof Acknowledgements

CPUE andmeantrophiclevelindicatethat coastal

We aregrateful to fishers fromthefishingcommuLa Paz,E1Sargento, LaRibera,and tainable. Foodwebcollapses mightnot haveoccurred nitiesofE1Pardito, yetbecause the dedinein meantrophiclevelhasnot Cabo Pulmo who providedinformationon fish Preliminary catch,effort,andgearanalysis at beenassociated with overall&dining catches (Pauly catches. et al. 2001),although mostspecies showed stagnant la Riberawasprovidedby A. Klett of the Centro Pesqueras in La Paz. catches.Althoughcoastalfisheriesregulations for Regionalde Investigaciones individuals andinstitutions provided helpand sharks andfinfishintheGulfofCalifornia theoreticallySeveral L. Findley,I. Parra, limitfishing effort,theydonotmentionhowit isto be advice:G. Anaya,J.C. Barrera, IslasdelGolfo,Parque MarinoNacionalCabo reached, beyond restricting fishing zones andgearspec- Reserva ifications (DOF 2000).Thereare no fishingquotas, Pulmo,and World Wildlife Fund--Gulf of California and enforcement is virtuallynon-existant. Urgent Program.Thanks to J. Curriss,L. Fichman, G. andA. Tombafortheirhelpwithourdivmeasures needto be takento develop andimplement Thompson,

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

fisheriesin the southernGulf of California are unsus-

ing operations.We are also grateful to three anonymous

Figure6. Meansize(+ S.E.) of four abundant reef fishes

in 21 sitesalonga gradientin fishingpressure in the

40 ,

•ß

N = 1646

30 •

southern Gulf of California. N= number of individuals for which size was estimated

duringvisualcensuses.

'•

Figure7. Changesin the

'•

Communitystructureis

i •0i

expressed asthe scoreon the firstaxisof a principal component analysis, providing a quantitative descnption of species abundance similarity at differents•tes.Fishing pressure explains 99% of the

the World Wildlife Fund•ulf of California

Haemulon sexfascialurn ,e ß

Foundation,The Tinker Foundation,the Robins

•

FamilyFoundation,and -

structure of fish communities

on rockyreefsalonga gradientinfishingpressure.

N= 977

Scarusghobban N = 759

40 35

•

are

and M. del Enebro for

continuous help and encouragement throughoutthe study. Thisarticle

Program.

indebtedto P. Dayton

reviewers

who greatly improved Lutjanus argentnventrls i the manuscript.This N = 1485 study was funded by the Moore Family

20 o

dedicated

the

memory of B. Montes

who helpedus in many ways throughout the

Fishingboats/km 2

study. •

variance in the data.

Literature

cited

Baum,J. K., R. A. Myers, D. G. Kehler,B. Worm, S. J. Harley, and P. A. Doherty. 2003. Collapseand conservation of shark populationsin the NorthwestAtlantic. Science299: 389-392.

Dayton,P. K., S. Thrush,andF. C. Coleman.2002.Ecological effectsof fishingin marineecosystems of the United States. PewOceansCommission, Arlington,Virginia. DOF--Federal Gazette.2000.Acuerdoporel quesedaa conocer la cartanacionalpesquem 2000.PoderEjecutivo--Secretarfa

de Medio Ambiente,Recursos Naturalesy Pesca.Diario Oficialde la Federaci6n(Mexico),MexicoD.E, 28 August 2000.

Estes, J. A., M. T. Tinker, T. M. Williams, and D. F. Doak.

1998.Killerwhalepredationon seaotterslinkingoceanicand 6

Fishing boats km -2 24

nearshoreecosystems. Science282:473-476. Froese,R., and D. Pauly. Editors. 2002. FishBase. World Wide

Webelectronic publication. www. fishbase.org, 19July2002. Haro, A., I. Parra, and H. Lie6n. 2001. Metodologfapara el reconocimientode amenazaspotencialesen el Golfo de Fisheries I www.fisheries.org I vol 29 no 3

California. Technical Report World Wildlife Fund PP22,

Pauly, D., M. L. Palomares,R. Froese,P. Sa-a, M. Vakily, D. Preikshot, and S. Wallace. 2001. Fishingdown Canadian Hernandez, A., and W. Kempton. 2003. Changesin fisheries aquaticfoodwebs.CanadianJournalof Fisheriesand Aquatic Sciences 58:51-62. managementin Mexico: effectsof increasingscientificinput and public participation. Ocean and Coastal Management Ramirez, R. M. 1988. La pescaen Baja California Sur: capturas 46:507-526. de 1952 a 1985. Pages31-37 in VII SimposioInternacionalde INEGI (Instituto Nacional de Estadistica, Geografia e BiologlaMarina. La Paz,B.C.S., Mâ&#x20AC;˘xico.

Downloaded by [University of California, San Diego] at 10:43 26 November 2012

Hermosillo, Mexico (2001).

Informfitica). 2002. Anuario estadisticode BajaCalifornia Sur. Instituto Nacional de Estadistica,Geograflae Informfitica.La Paz,BajaCalifornia Sur. Jackson,J. B.C., M. X. Kirby, W. H. Berger,K. A. Bjorndal, L. W. Botsford,B. J. Bourque,R. Bradbury,R. Cooke, J. A. Estes,T. P. Hughes, S. Kidwell, C. B. Lange, H. S. Lenihan, J. M. Pandolfi, C. H. Peterson,R. S. Steneck, M. J. Tegner, and R. W. Warner. 2001. Historicaloverfishingand the recent collapseof coastalecosystems. Science293:629-638 Musick, J. A., M. M. Harbin, S. A. Berkeley,G. H. Burgess,A. M. Eklund, L. Findley, R. G. Gilmore, J. T. Golden, D. S. Ha, G. R. Huntsman, J. C. McGovern, S. J. Parker, S. G. Poss,E. Sala, T. W. Schmidt,G. R. Sedberry,H. Weeks, and S. G. Wright. 2000. Marine, estuarineand diadromusfish stocks at risck of extinction in North America (exclusive of Pacific salmonids).Fisheries25(11 ):6-30.

Roberts, C. M., C. J. McClean, J. E. N. Veron, J.P. Hawkins, G. R. Allen, D. E. McAllister,

C. G. Mittermeier, F. W.

Schueler, M. Spalding, E Wells, C. Vynne, and T. B. Werner. 2002. Marine biodiversityhotspotsand conservation prioritiesfor tropicalreefs.Science295: 1280-1284. Sala, E., O. Aburto-Oropeza, G. Paredes, I. Parra, J. C. Barrera, and P. K. Dayton. 2002. A general model for designingnetworksof marine reserves.Science 298: 19911993.

Sala, E., O. Aburto-Oropeza, G. Paredes,and G. Thompson. 2003. Spawningaggregations and reproductivebehavior of reef fishes in the Gulf of California. Bulletin of Marine Science 72: 103-121. Secretarla de Marina. 1950-1960. Anuario estadlstico de

actividades pesquerasen aguas territoriales Mexicanas. Gobierno de los EstadosUnidos Mexicanos, Mexico D.E

Myers, R. A., and B. Worm. 2003. Rapidworldwidedepletionof Secretaria de Pesca. 1970-1980. Anuario estadfsticopesquero. Gobierno de los EstadosUnidos Mexicanos, Mexico D.E predatoryfish communities.Nature 423:280-283. (Secretarla del Medio Ambiente, Recursos Pauly, D., V. Christensen, J. Dalsgaard, R. Froese, and F. SEMARNAP Torres. 1998a. Fishing down marine food webs. Science Naturales y Pesca). 1990-2000. Anuarios estad[sticosde 279:860-863. pesca.Secretariadel Medio Ambiente, Recursos Naturalesy Pesca. Mâ&#x20AC;˘xico D.E Pauly, D., R. Froese,and V. Christensen.1998b.How pervasive is "Fishingdown marinefoodwebs?"Science282:1383. Worm, B., H. K. Lotze, R. A. Myers. 2003. Predatordiversity hotspots in the blue ocean. Proceedingsof the National Pauly, D., V. Christensen,R. Froese,and M. L. Palomares. 2000. Fishingdown aquatic food webs. American Scientist Academyof Sciencesof the United Statesof America 100: 88:46-51.

March 2004 I www.fisheries.org I Fisheries

9884-9888.