Fishing Down Coastal Food Webs in the Gulf of California
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Fisheries ISSN: 0363-2415 (Print) 1548-8446 (Online) Journal homepage: http://www.tandfonline.com/loi/ufsh20 Fishing Down Coastal Food Webs in the Gulf of California Enric Sala , Octavio Aburto-Oropeza , Miriam Reza , Gustavo Paredes & Luis G. López-Lemus To cite this article: Enric Sala , Octavio Aburto-Oropeza , Miriam Reza , Gustavo Paredes & Luis G. López-Lemus (2004) Fishing Down Coastal Food Webs in the Gulf of California, Fisheries, 29:3, 19-25, DOI: 10.1577/1548-8446(2004)29[19:FDCFWI]2.0.CO;2 To link to this article: http://dx.doi.org/10.1577/1548-8446(2004)29[19:FDCFWI]2.0.CO;2 Published online: 09 Jan 2011. Submit your article to this journal Article views: 361 View related articles Citing articles: 53 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ufsh20 Download by: [The University of British Columbia] Date: 09 May 2016, At: 08:31 Fishing down coastal food webs in the Gulf of California We usedinformation from interviewswith fishers,fisheries statistics, and field surveysto doc- ument changesin fisheriesand fish assemblagesin shallowcoastal habitats in the Gulf of California, Mexico. Coastal food webs in the Gulf of California have been "fished down" dur- ing the last 30 years--fisheriesshifted from large, long-livedspecies belonging to high trophic levelsto smallshort-lived species from lower trophic levels.In addition,the maximum individuallength of the landingshas decreased about 45 cm in only 20 years.Although some catchesare stagnantor stillincreasing for somespecies groups, catch-per-unit-effort declined for mostspecies groups after 1980.These declines were associatedto a dramatic increasein fishingeffort in the region in the late 1970s-early1980s, mostly in the numberof gillnets. Fishingnot only impactedtarget species,but alsocaused community-wide changes. These resultssuggest that coastalfisheries in the Gulf of Californiaare unsustainableand their managementneeds to be reevaluatedwith soundregulatory measures to preventfurther degradationof coastalfood webs,and the concurrentinefficiency of artisanalfishing. Introduction 2002). The totalnumber of localcommercial fishers in the studyregion is 10,600(SEMARNAP, 1990-2000), Fisheriescatches worldwide have gradually shifted althoughthese shores are also used by hundreds of fish- ftom long-lived,high-trophic level species to short- ersbased on mainlandMexico, fromSonora to asfar lived, low-trophiclevel speciesin what has been southas Chiapas.The fisherytargets coastal fishes called"fishing down marine food webs" (Pauly et al. belongingto 25 families 1998a;Baum et al. 2003; Myers and Worm 2003; (Table 1). The most Wormet al. 2003).This patternis consistentamong commonlyused fishing Enric Sala marineand fteshwaterecosystems at both regional gearis a motoredfiber- andlocal scales (Pauly et al. 1998a,1998b, 2001). The glassskiff with hand Octavio Aburto-Oropeza consequencesof fishingdown food websextend linesand gillnets. Miriam Reza beyondthe directeffects on the targetspecies became Fisheries in Baja Gustavo Paredes the removalof large predatorscan came changes California Sur showed affectingentire ecosystems (Estes et al. 1998;Jackson a general pattern of LuisG. Lbpez-Lemus et al. 2001). In Mexico,82% of the fisheriesfully increasingcatch since exploitor over-exploittheir target species (Hernandez 1950 but decreasing Sala is associatedirector, Center for Marine andKempton 2003), but thereare no publishedanal- catch-per-unit-effort Biodiversityand Conservation,and assistant ysesof fisheriesshifts and their ecosystem effects. Here (CPUE) after 1980 professor,Scripps Institution of Oceanography,La Jolla, CA. He can be reached at [email protected]. wepresent evidence of fishing down marine food webs (Figure1, Secretariade Aburto-Oropezais a researcher,Universidad in the Gulf of California,a tropicalmarine biodiver- Marina 1950-1960; sity hotspot(Roberts et al. 2002), and addressthe Secretaria de Pesca Autbnomade BajaCalifornia Sur (UABCS),La Paz, BajaCalifornia Sur, Mexico. Reza is conservation needfor rigorousfisheries management in the region. 1970-1980; Ramirez scientist,Gulf of CaliforniaProgram-World Wildlife In spiteof its low humanpopulation density, the 1988; SEMARNAP Gulf of Californiais subjectedto intensefishing. Fund, Hermosillo,Sonora, Mexico. Paredesis a 1990-2000). The only graduatestudent, Scripps Institution of Downloaded by [The University of British Columbia] at 08:31 09 May 2016 Presently,six species of marinefishes (Serranidae and exception of CPUE Oceanography,La Jolla,California. Lbpez-Lemus is Sciaenidae)are threatened or at riskof extinctionin decrease after 1980 the Gulf of California(Musick et al. 2000). Sinceno adjunctprofessor at UABCS,La Paz,Baja California wasfor a multi-species Sur, Mexico. publishedanalyses of the ecosystemimpacts of coastal fishingin the Gulf of Californiaexist, we describe changesover time in fishcatches and mean trophic BONY FISHES SHARKS RAYS levelof the coastalfishery in the southernGulf of Table 1. Major fish California.In addition,we attempted to determinethe Serranidae Alopiidae Rhinobatidae familiestargeted by changesin the structureof coastalfish assemblages Lutjanidae Carcharhinidae Mobulidae the artisanalfishery Lamnidae in the southern Gulf associatedwith documentedfishing pressure, and Carangidae Myliobatidae Haemulidae Echinorhinidae Dasyatididae of California. changesin thespatial distribution of theartisanal fleet. Balistidae Squalidae Baja California Sur Fisheries Scaridae Heterodontidae Labridae Ginglymostomatidae We studiedthe coastalartisanal fishery in Baja Mullidae Odontaspidae CaliforniaSur. This fishery operates from a largetown Kyphosidae Scyliorhinidae (La Paz,154,314 inhabitants) and severalsmall fish- Malacanthidae Triakidae Sphyrnidae ing villagesranging from 13 to 177 people(INEGI March 2004 I www.fisheries.org I Fisheries 19 Figure1. Annualfish catch (solid circles) and catch categoryof medium- and small-sizedgroupers (Figure h per uniteffort (CPUE; metric tons/boat) (open "other groupers").The catches of the goliath grouper squares)in the southernGulf of California. (Epinephelusitajara) and snappers(except red snapper)also 5harksinclude: 37 speciesfrom 11 families(Table showed declines in catch after 1980. Because CPUE declined 1)caught in nearshoreand offshore fisheries. over time, the fluctuations and increase of catch in multi- Jacks:green jack (Caranx caballus), speciesgroups may be due to the shift in targetspecies over Pacificcrevalle jack (C caninus), bigeye(•evalle jack (C sexfasciatus), time (see Results).These changeswere associatedwith a rainbowrunner (Elagatis bipinnula•a), strikingincrease in the numberof motoredfishing boats and Padticmoonfish (Selene peruviana), and gillnets in the region since 1980 (Figure 2) (Secretariade gafftopsailpompano (Trachinotus rhodopus) Redsnapper: Lutjanus peru. Marina 1950-1960; Secretaria de Pesca 1970-1980; Othersnappers include: SEMARNAP 1990-2000). This patternis similarto that of yellowsnapper (Lutjanus argentiven•), all Mexican fisheries•in the late 1970snational policies dogsnapper (L novemfasciatus), mulletsnapper (L aratus), induceda significantmigration of unemployedfield workers spottedsnapper (L. guttatus), towardscoastal states, then landingspeaked in 1981, and coloradosnapper (L. colorado), and catchesdeclined afterwards in spite of a huge increasein barredpargo (Hoplopagrus gunther/). fishingeffort (Hernandezand Kempton 2003). Goliathgrouper: Epinephelus itajara Othergroupers include: Methods leopardgrouper (Mycteroperca rosacea), spottedsandbass (Paralabrax maculatofasciatus), Becausethe catchis pooledinto coarsetaxonomic groups Panamagraysby (Epinephelus panamensis), flagcabrilla (E. labriformis), and in the Gulf of California, fisheriesstatistics do not allow cal- Pacificcreolefish (Paranthias colonus). culationof the meantrophic level (Paulyet al. 2000). Catch 5000 8 1000 - 1.5 Sharks Jacks 4000] 800 - 6 - 1.0 600 3000] 4 400 2000i - 0.5 2 200 10000 0 0.0 600 0.5300 [ 0.3 • 400 2001 Downloaded by [The University of British Columbia] at 08:31 09 May 2016 200 100 • 0 0.0 0+ 0.0• 1000 , - 1.5 6000I 2.0 ' Goliathgrouper 800 • 5ooo] groupers - 1.5 I 1.04000 1/ 3000,,2' 6001 /Other 7 1.0 400 ß - 0.5 200 -0.5 800•/ 0•-• 0.0 0 0.0 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 Year Year 20 Fisheries I www.fisheries.org I vol 29 no 3 Figure 2. Temporalchanges in the numberof fishers,fishing boats, and gillnetsin the length of each speciestimes its relativecontribu- southern Gulf of California. tion to the total catch. To assessthe temporalshifts in the spatialdis- tribution of the artisanal fleet we interviewed 4000; F 12000 fishersfrom the fishingcamp of E1 Parditoabout the locationof fishingsites and their useover time. 3000/ Fishers / / / F 10000 For everyfishing site used since 1970 we estimated a numberof fishingdays per year. We then entered 8000 the locationand use of everyfishing site for every time periodinto a geographicinformation system (ESRI Arc View 3.2a). Maps of fishingintensity wereobtained interpolating the dataon a matrixof 4000 72 points(on a 1:150,000scale map). 1000 The firsteffects of fishingare a reductionin the 2000 abundanceand averagesize of target species (Daytonet al. 2002). To determinethe impactsof O• the fisheryon the sizestructure of selectedtarget 1950 1960 1970 1980 1990 2000 specieswe used data obtained during visual censuses conductedfrom 1998 to 2001 in 21 rocky reefs data setsfor