ShrimpBook Abundance Turner
Turner, R. E. (1989) Factors Affecting the Relative Abundance of Shrimp in Ecuador.
A SUSTAINABLE SHRIMP MARICULTURE
INDUSTRY FOR ECUADOR
Edjttd by Stephen Olsen and Luis Arrlaga
Factors Affecting the Relative Abundance of Shrimp in Ecuador
Factores que Afectan la Abundancia Relativa del Camarón en el
Ecuador
R. Eugene Turner
Resumen
La producción de camarones peneidos en Ecuador tiene significación nacional, en términos de
volumen, valor y ocupación de mano de obra. Aunque la producción en piscinas aumento grandemente en
los últimos años, los datos disponibles sugieren que la producción por superficie (Kgha) ha declinado
significativamente. Desde la perspectiva del manejo del recurso, las preguntas claves comprenden: ¿Cuáles
son los impactos de la tala del manglar?; ¿Cuál es la variación natural en el reclutamiento?;¿Se puede
aumentar el suministro de postlarvas naturales?; ¿Cómo influye la captura de postlarvas y juveniles en el
tamaño del "stock?.
Después de presentar informaciones sobre el ciclo biológico del camarón y las relaciones del
reclutamiento en abiente natural, el autor trata sobre los efectos de áreas pantonosas costeras en el
reclutamiento del camarón, sosteniendo que el crecimiento y la supervivencia de las postlarvas en los esteros
constituyen, probablemente, los factores más importantes que afectan a la magnitud de la población adulta.
Se incluyen ejemplos de Malasia, Filipinas y Golfo de México (Luisiana),en los cuales se demuestra que los
rendimientos a largo plazo están relacionados linealmente tanto a la calidad como a la cantidad del habitat
intermareal.
Asunto relevante, además de la riqueza orgánica del ecosistema de manglar, es la protección que
porporcionan las estructuras de la planta a los camaronerosjuveniles, conforme ha sido demostrado en
experimentos sobre la relación predador-presa, que son citados en el trabajo.
Se analiza la influencia del clima sobre las fluctuaciones anuales del "stock" de camarones,
estableciéndose que en el Ecuador hay una baja variación anual (20%)de la "capturapor unidad de esfuerzo"
(CPU), en comparación con la de otros países (hasta un 90%). La presencia o ausencia del fenómeno de El
Niño, es determinante en las variaciones anuales.
En las conclusiones, el autor expresa que la conservación de la "cantidad de habitat" es altamente
significativopara mantener el éxito sostenido en el reclutamiento de los "stocks", puesto que parece que la
extensión del habitat es el factor determinante de las densidades potenciales del "stock natural, que son
modificadas anualmente por influencias climáticas.
En consecuencia, la recomendación del autor es la conservación de las zonas de manglares, si el
Gobierno desea prevenir grandes cambios en los "stocks" de postlarvas, juveniles y adultos. Donde sea
posible, el manglar debe ser restribuído mediante el restablecimiento de la hidrología natural. La zona de
amortiguación del manglar alrededor de las áreas taladas debería ser al menos el doble del área talada.
También, concluye en que la industria del camarón presenta signos del aumento de conflictos entre
usuarios de los recursos, necesitándose datos precisos para lograr el éxito en la interacción entre todas las
partes interesadas.
Finalmente, recomienda divulgar técnicas para aumentar el suministro de postlarvas mediante la
disminución de la mortalidad durante su manipuleo.
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Citation:
Turner, R. E. (1989) Factors Affecting the Relative Abundance of Shrimp in Ecuador.
In Olsen, S. and Arriaga, L., editors. A Sustainable Shrimp Mariculture Industry for Ecuador.
Narragansett, RI: Coastal Resources Center, University of Rhode Island.
Introduction
extensivelythroughouttheEcuadoriancoastalzonefrom boatsandin ponds
Penaeids
areharvested
built within the mangrovelinedestuaries.The harvestis of nationalsignificancein termsof volume,value
questionshavearissnasthe
andemployment(Sutinenet al., this volume), Resourcemanagement
depleting
thepondoperators-of
fishermen
have
accused
trawl
For
example,
mariculiuresystemdeveloped.
(PL) andjuvenilesto supplythe ponds. As manyas90,000to 120,000
stocksof wild shrimppostlar'rrae
peoplemay be involvedin postlarvaecollectioneachyear,andtheeffectson the shrimppopulationis
haveled to seriouseconomicdifficulties,particularlyfor the pond
unlinown. RecentPL shortages
percent
thepondswereidle dueto a shortageof wild-caughtpostlarvae,which
of
in
1985,
50
operalors;
(-iPuma andMeltzoff, 1985). Many of thepondsare
representup to one-halfof pondoperationexpenses
(Cintro1,1981)and
of theestuarineecosystem
itimangtoni zoneswhich areveryproductivecomponents
ponds
dramatically
increased
in
the
Although
catches
including
shrimp.
fauna,
contrib;6gto both flora and
thatthearealrateofproduction(kg/ha)for all pondshasdeclined
in recentyears,the availabledatasuggests
significantly.Thereareseveralreasonsfor this decline:
.
Thebestsitesmay haveakeadybeenchosenleavingonly ttrepoorestsitesfor later
development.
.
or neverused.
For economicreasonspondsmaybe abandoned
. The statisticsarenot accurate'
. Pondoperatorsarenow relying moreon naturalstockingofponds throughtidal action
thanon stockingwith caughtlarvae.
stepswerenot takenbefore
. Pondfertility is depletedafterthreeharvests,
andmanagement
seedingthefourthproductionperiod.
of
.
and,therefore,wersnot countedin earlierestimates
Mostpondswereunauthorized
ProductivitY'
Informal exportsof shrimpthroughPeru,amongothercountries,havealsocontributedto
this skewedappeafince.
concemingtherelative
perspective,
thekey questionsto be addressed
Froma resourcemanagement
stocks
are:
natural
shrimp
of
abundance
. What arethe impactsof clearingmangroves?
. What is thenaturalvariationin recruitment?
.
Canlhe naturalpostlarvaesupplybe increased?
.
How muchdoesthe harvestof postlarvaeandjuvenilesinfluencethe offshorestock size?
.
Life Cycles of Wild Penaeid ShrimP
Shrimpbeginlife in the openseaaseggswhich maturethroughnaplius,protozoealandzoeal
wate6
stages.lfter Oriftirigduringthepelagiclarvalphases,thepostlarvaeenterlower-salinityestuarine
next
the
until
cling
they
which
to
roots,
mangroue
as
such
iubsrates,
nutrient-iich
seek
and
on"floodtides
growing
(bottom-dwelling),
tide takesthemdeeperinto the estwfy. Eventuallyttreshrimpbecomebenthic
retum to the
ttrefood-riin andpredator-r.ifotqOenvironment.Afier severalweeksor months,they
G;ir
postlarvae
as
from
estuaries
shrimp
harvest
(Figure
Fishermen
1).
zones
oc|an-reruining in the rt'uUo*
reasons
For
for stockingpon-ds,or as subadultsandadultsin the nearshoreand openoceanicwaters.
to be estuarinedependent'
penaeidshrimpareassumed
below,most;ommercially-important
discussed
by
is widely acknowledged
major.fisheries
to
suppoit
ateas
Thecapabilityof estuarinemangrove
in
congregate
fisheries
important
commercially
of
many
TheJuveniles
scientists,but nbt weli understood.
for
more
adaptable
species
-3[ti*p,
anOiefugefrom predators.Suc[ behaviormakesthese
shallowzonesfor feeOing
of favorableshallowwaterhabitatsduring
iti'patticuiat,takeadvantage
maricuttureop"rutions.
postlarvaearepresentvirtually all year
shrimp
thai
revealed
have
studies
criricallife cyclestages.Various
in relationto the lunar,diurnalandtidal cycles'
in mangrovewaters,uitttougttnumbersfluctuateseasonally
r22
Shrimp Recruitment Relationships
Penaeidshrimpstockssufferthe greatestmortalitywhenthe organismis smallest.In many
fisheries,variationsin recruitmentof an agegoup into theexploitedstockis drivenby adultspawning
biomasssize. But stockrecruitmentrelationships
for penaeidshrimparenot clearlydemonstrable
(Garcia,
1983)becausetheadultstocksizeis determinedby thechangesin juvenile,evenpostlarvaeabundance,
and
is not primarily relatedto changesin adult spawningbiomass.
However,therearereasonablecausalrelationshipsbetweenlarval andjuvenile abundances
andthe
subsequent
densities(GarciaandLeReste,1981).In turn,the stockrecruitmentsuccess
is clearlydependent
on climaticfactors,predationlevels,food supplyandhabitatquality. Of these,thoughnot preciselydefined
for penaeidshrimp,habitatis considered
theprincipallong-termfactorinfluencingsustainedshrimp
harvests.ShSmpmariculturein Ecuadormay havecontributedto thechangein thedominantspecies,from
Penaeusoccidentalisto P. vannamei.P. vannameiis moreadaptableto coastalpondsenvironments,
and
inefficienttechniquesmay releaseto theestuary1,000poundsof IO-ZOgrampreadultshrimpduringthe
harvestof a single10hectarepond.
Effects of Coastal Wetland Area on Recruitment of Penaeid Shrimp Stocks
Coastal Wetland Area and Shrimp Stock Size
Researchers
agreethatlarvalshrimpmovementandrecruitmentfrom the spawningsitesoffshore
.
into_estuaries
ar9nrobablythemostimportantfactorsaffectingtheharvestable
adulipopulition size(Garcia
andLeReste,1981;Garcia,1983;TumerandBrody, 1983).Alrhoughestuarinesafiriityandtemperarure
changesaffecttheannualpotentialfor postlarvaesurvival,tie long-iermyieldsarelinearlyrelatedto both
thequantityandqualityof intertidalhabitat. Despitethedifficulty in obtainingreliablemeasures
of fishing
effort andlandings,thereareseveralexamplesof ttrehabitat-yieldrelationship?roughout
theworld.
Jothy(1984)providesdatafrom Malaysiarelatingmangroveareaandshrimpyields(Figure2).
Althoughtheauthordoesnot describethetime periodof 6e shrlmphndingsdatanor itreu-iont of fishing
effort, thereis a clearrelationshipbetweenshrimplandingsandmangroveareain eachof the statesalong
Malaysia'scoastline.
PaulyandIngles(1986)compiledsimilarstatisticsfor thePhilippinesandthe samerelationship
holdsbetweenshrimplandingsandmangrovezoneGrgure3). Theresearchers
live in ttrefhilippines and
hadaccessto lon-g-term
dataon bottrtheartisanalandcommercialrawl catches.They etiminatedunder-and
over-reportingof catchdataandthe abuseof mangrovearealestimatesfor economicinterestsconcernedwith
Lhemangrovelumberconcession.
- . Long-termdataandmonitoringfrom theentirenorthernGulf of Mexico arealsoavailable.The
areaof intertidalvegetationis alsowell knownthroughseveralsurveyssince1960,with theareaof
vegetationdirectlyandlinearlyrelatedto the tidal landingsin anyoneyear@igure4). The vegetationin
theseestuariesis not dominatedby mangroves(exceptin isolatei casei;. rirer.-e
is alsono sign'ificant
relationshipbetweenwatersurfaceareaandlandings,exceptfor a possibleinverserelationshi'p.In addition,
the speciesof shrimpcaughtaredirectlyrelatedto itre tdnosof intertidalcoastalvegetationin^eacharea.
The samedirectrelationship
betweencommercialharvestsof penaeidshriilp andintertidal
vegetationis foundworldwide,thoughit changeswith latitude,rising with decreasing
latitudeuntil around
5o N/S whereit declinesSigure 5).
. . The importantcommercialspeciesin Ecuadorarelistedin Table1 anddistributionof harvestby
speciesis shownin Table2.
The relationshipsof wetlandareato penaeidshrimpyields havebeenindirectly testedttrrough
large-scale
changesin wetlandareas.Severalexampleshavebeendocumented
with vaiiousOeg.ees
of
success(Figure6, Table3).
In Louisiana,the coastalwetlandlossrateis 0.8percentper year(Craiget al., 1979;Tumer, 1979,
1982;Turneret al., 1982). Changesinvegetationate accompanied
by changesi-nthe shrimp'catchin direct
relation_lothe lossor gainof wetlandsin eachestuary.Therearealsodemoistratedrelationships
between
the qualityof estuarinewetlandsand shrimpcatch. Due to thelossof wetlandareasoverthepast30 years,
r23
increasein brackishshrimpspecies(Figure
moresalt-lolerantvegetationhasdominated,with accompanying
7).
In Japan,Doi (1983)showedthat the declinein yieldsof P. japonicuswasproportional!o land
shallow
reclamationin theestuaryGigure 8). However,theintertidallandwasmostlyunvegetated,
in
in therecruitmentof P. semisuculatus
mudflats.MorganandGarcia(1982)noteda long-termdecrease
Kuwait andSaudiArabiarelatedto estuarinelandreclamation.In El Salvador,mangroveswereclearedfor
agricultureandthe shrimpfisheriesdeclined,ttroughthe fisheriesanalysisis far from completedueto
difficulty in obtaininggoodestimatesof landingsandeffort (Daugherty,1975).
Finally, in thePeople'sRepublicof Vietnam,the chemicaldefoliationof the southerncoastalzone
lossof mangroves.Thoughtheanalysisis not generallyavailable
duringthelatestwar causedwidespread
review,
for
there
apparentlywasa severedeclinein coastalfisheriesstocks,
community
to the scientific
includingshrimp(Norman,1983).
Causal RelationshipsLeading to the Wetland-Stock Relationships
interactionsin wetlandsshowsimilarpattemsin shrimpyields.,For
Experimentsin predator-prey
numbersof
estuarywith leveesor bulkheadsresultin decreased
from
the
off
*etlands
btocted
example,
adult stnimpat the alteredsites(Mock, 1967;Trentetal.,1976). Althoughthe wetlandedgeis particularly
high in organics,a moreimportantfactormay be theprotectionfrom predatorsthatplant structuresoffer
th6 shrimf. Field andlaboritory predator-preyexperimentswith P. ^ztecusin vegetatedandnon-vegetated
saltmarshhabitatsindicatethat smalljuvenileshideamongplant stemsto escapepredators(Minello and
ZimmermanandMinello, 1984;Zimmermanet al., 1984;MinelloandZimmerman,
Zimmerman,1983a,b;
predatorattackson prey declineswith increasingvegetationcomplexity'
1985). The numberof successful
Thuswetlandhabita6appearto be favoredsitesfor juvenile shrimp,which is consistentwith observations
in thepresenceofpredators(Charnovet al., 1976). These
of organismadaptationio resourcedepression
areafo observedfor freshwaterlakeswith wetlandsfringingtheirborders,coralreefs,seagrasses
tespo-nses
1978;SavinoandStein,1982;Strangeetal., 1982;
1978;Johannes,
und.iu"rr (GroenandSchmulbach,
Hoyer
RobbleeandZieman,1984;
Huston,1984:
Holland
and
Duroucher,1984;HeckandThomas,1984;
1985).
Tumer,
Risotto
and
et al., 1985;
Mangrove
Loss and Postlarvae and Adult
Supply
Doesdeclinein shrimplandingsor postlarualsupplyfollow the lossof mangrovesdueto
mariculturepondconstructionfTo addressthis question,it is worthwhileto determinethe changesin
arbassincesignificantpondconsfuctionbeganin or about1976.
mangrove
The declinein irangroveareain Ecuadorasa directresultof theconstructionof maricultureponds
in tle mangove zoneis estiiratedat 10.6percenrby Alvarez(his yolgme). Valdiviezo(no date)estimated
and89,368ha of brackishwatermariculture
tlratthereiete a total of l75,2Lghectares(ha)of mangroves
River estuary(CLIRqEry,1983)indicates
the
of
Guayas
study
1982.
One
ponar (fuUf" 4) in Ecuadorasof
in mangroves(Tab195). Assumingthat
1982-83
occurred
1966
to
from
pond
the
16'perceniof
ihat
$owth
abouttb percentof thi pres6ntmariculturepondsarein formermangrovezones,thenabout9,000ha of
areno longerfunctioningasa forestedwetlandecosystem..
mangroves
Is this estimited10.6percJntdeclinein mangrovematchedby an equivalentdeclinein shrimp
for
presentlandings.statistics
landingsor postlarvalsupplies?This is a difficult questionto address-with
(Figure
the
years
9),
15
last
Ecuad6r.Alttrougtrthe riwl effort hasremainedsomewhatconstantfor the
-t.t p". unit eff6rt (CPUE)hasfluctuated;but naturalvariationsin a varietyof fisheriesstocks,especially
shrimp,
' fluctuateat least20 percentin any oneyear.
Further,the 10.6peicent declinei in mangrovearecumulative. In 1980declineswereonly around
1.0percent,so the impact'of*angroue lossis relativeto annualenvironmenlalfluctuationsthat affect
stocls. Evenso, the CPLIEin the last severalyearsis lower thanaverage.
Anotherquestionis whetheror not fishingeffort in thelast few yeat!.!T remainedconsunt.
for a changingeffort, as wetl asvesselnumbers,it is difhcult to separateout the
Wittroutcotnpensuting
relativeinfluencesof 6tmate,effort anOmangrovedecline. Certainlythe effort hasnot beencomp-letely
haschangedsince1980(Figure10)'
constantbecausethe sizeof tireboats(measuedin horsepower)
Effects of Climate on Annual Fluctuations of Penaeid Shrimp Stocks
Natural Variations in Stock Size
Adult stockharvestsmay vary asmuchas 100percentfrom yearto year. Table6 showsthe
coefficientof variationfor ttreEcuadorianfawling fleetandseveralotherworid shrimpfisheries.The
Ecuadorfleet hasa very low variationin CPUEof 20 percentcomparedto up to 90 percentelsewhere.
Clewly therehasbeenhigh stabilityin recruitmentovbr the 1xt25 yearsin bcuadoi. However,thereis
still muchvariationfrgm yearto year. Understanding
the factorsleadingto this variationis importantto
the management
of this fishery.
It is now well documented
thattheselargeannualvariationsareassociated
with changesin
estuarineconditions.Variationin estuarinesalinityandtemperature
arethebest-documented
climatic
influencesCtable7), but thefrequencyandintensityoffrontal passages,
river discharges
or subs6ate
conditionsmay alsobe important.Numerousdataon CPUEareauailable(e.g.,Gullind andRothschild,
1984;Kapetsky,1981;KapetskyandLasserre,1984a,b),but rhereis no systdmaticandcomparative
analysisof climaticinfluences.CopelandandBechtel(1974)analyzedttreiatinityandtemperature
preferences
of severalpenaeidspeciesin estuaries
of thenorthernbulf of Mexi.o. rtr"/
demonstrated
the interactiveoptimalpreferences
"i6atiythanlinear
by shrimpfor temperature
andsalinitn rather
relationships
dominatedby one factor.
Cun andMarin (1982)examinedfisheneslandingsdatato determinetheannualchangesin the
c_atch
of P' stylirostrisin thenorthern(zonade Golfo),cenral and southernparts(zonadephlas) of the
Gulf of Guayaquilbetween1965and 1979(Figure11). Theinrerannualvariationiwerehigtrandtherewere
differencesin speciesdominancebetweenareai,thoughthereasonsarenot yet understood.
Dataon theflow of theJubonesRiver,which entersthe Guayaseituary(Table8) wasused
asa
sturogatefor regionalvariationsin rainfall andtemperature,
demonsratingan inverscretaiionitripwittr
riverflow and CPUE(seeatsoFigure 12). SinceEi Nino uiually bringswet and warmweather,
these
eventsseemto indicatettratsucheventsareunfavorablefor shrimpre6ruitment.However,themostrecent
El Nino eventsof the80sresultedin very high valuesof CPIIE, but arenot includedhere
becauseof the
lack of riverflow data.
analysisof effectsof climateon
_Trgmajorpoint or this figure is to encourage
ElugdgrianshrimpCPUE(aswell asottrerspecies).This upprouclihu,prbuenfeasibleelsewhere(e.g.,
Table7).
rmplications for Managementof penaeid shrimp stocks
The optionsavailable_to
penaeidshrimpmanagers
mightbe describedasbeingof threetypes:
economic,or
processing
and
management;
personnel,or slocio-cultural
manageme-nq
anOtrauitat
{9e1
management.Habilatmanagementis
emphasized
here. Theprimarycauseof cha-nges
in thesewetlandsare
manmadeactivitiesandmay,therefore,be manageable.
Without moreatrcnrionto-habitat,thefirst rwo
concernswill becomelessimportantandmoredifficult to implement.As the potentialcrop
of bottr
posflarvaeandaduls decreases
with wetlandlosses,optionsto *anrge whateverremains
becomemuch
morelimited.
Penaeidshrimpmanagersshouldregardhabitatmanagement
astheirprimaryresponsibility.
.
ottrerwise,theywill befacedwith trying to dividefewerandfJ*"t rto.tr amongmore
an6morepeople,
especiallyfishermen,while watchingtheir well-designed
but slaticmanagement
plansfalter with changing
environmentalconditions.
Conclusions and Recommendations
Below aresomeconclusions
andrecommendations
basedon thereviewof penaeidshrimpbiology
andthepresentsituationin theEcuadorianfishery. Thesewill necessarily
be broadiystatedsince
personnel,politics and
implementationmustbe flexible to reflectlocal variationsin economies,
environment.
Conclusion:Penaeidshrimprecruitmentfrom larvaeto adultis srongly influencedby
1.
adultstocksizesis supported
habitatqualityand quantity. The hypothesisthathabitatquantitydetermines
of habitat
Conservation
from
ecosystem.
removal
the
wetland
by limited neld otservationsfollowing
quantity is of high significanceto sustainedstockrecruitmentsuccesssinceit seemsto be the final
diterminantof riaturalpotentialstockdensitieswhich climaticinfluencesmodify annually.
if thegovernmentwantsto avoid
Mangrovezonesmustbe conserved
Recommendations:
is probablyat its naturallimit,
juveniles
harvest
Stock
and
adults.
postlarvae,
of
major changesin stocks
is in order.
stocks,
few
remaining
of
the
further
exploitation
rather
tlan
conse*:ation,
and
of the
shouldbe restoredttrroughreestablishment
Wherepossible,mangroves
naturalhydrologY.
Mangrovebufferzonesaroundclearedzonesshouldbe at leasttwicethelevee
width andincludettrelevee'
.
.
Conclusion:The shrimpindustryin Ecuadoris expansiveandintensive,andshowssigns
Z.
involvedto
of increasinguser-useconflict. Minimizition of cbnflict is possiblebut all partiesmustbe
succeed'
interaction
to
for
this
is
required
optimizeintEractions.Accuratedata
Anlntegratedstudyplanwhich includesall usersandall aspegpof
Recommendations:
conflictsare
since-resource
mustiepresenttheecosystem
theenvironmentshouldbe developed.Oneag-ency
quality;
the
water
and
mangroves
e.g.,
resource,
the
common
prtAffy 6ur"d on individualexploirationof
of
vmiety
for
a
implications
long-lasting
have
use
and
resource
ir*.r itr .omplicated,involve^multiple
social,political andnaturalresources.
.
.
.
.
3.
4.'
Determineif thedeclinein kg/haof pondsis real. If not, determinewherethe
dataareincorrect. Canthis situationbe rectified? If the declineis real, what are
thereasonsbehindit? Are theyecological,economicor political?
Examinethe existingdatato seeif thereareany otherdatawhich could be
for long-termanalysis.
summarized
Develop a completefisheriesstatisticalanalysisandcontinuedatacollection.
effort to formalizea captain'slog book to
Supportthe newly-established
summarizefishing efforfi trips, hours,etc'
changes
Conclusion:The variationsarehigh enoughnow to masktherelativelysmaller
in stocksizedueto presentreductionsin mangrove'
in stocks
Recommendafl;: I; ;alysis of the effectsif climateon the annualvariations
oceanic
of
the
effects
examine
usefullo
especially
be
tt
would
shouldbe.o*pt.i"A.
anomalieson shrimpandon otherstocks'
temperature
withoutexploitingadditionalmangrove
Conclusion:postlarvaesuppliescanbe increased
andbeforeinftoductioninto ponds'
capture
postlarvae
after
tossbt
the
zonesby reducing
to increasethe supplyof postlarvaeby
no.utgaie techniques
Recommendatioti:
the mortalityof thosecaught.
decreasing
126
Table 1
List of Shrimpof CommercialImportance(lrtcPadden,1985)
CommonName
Family
Species
Blanco
Peraidae
Penaewvannamiei
P. stylirostris
P. occidentalis
Cafe
Pernidae
P. californiensis
Rojo
Penaidae
P. brevirostris
Zpbn
Penaidae
Trachypenaeus
byrdi
T. pacift,cus
T.face
Pomada/Titi
Peraidae
Xiphopenaeus
riveti
Protrachypettaeuspr ecip tn
Carapachudo
Solonoceridse
Solonoceraspp.
CamronesdeProfundidad
Pmdalidae
Heterocarpusspp.
Table 2
Distributionof ShrimpSpeciesin Marineandpond Harvests
(fromM. Cobo,mimeoreport)
Species
P. occidentalis
P. styliorstris
P. vannamei
P. califurniensis
Trachypenewbyrdi
T.faoea
T. similispacificus
Xtphopeneus
riveti
Pr otrachypene
pr ecipua
Solenoceraflorea
7oCommercial
Catch
70
15to 20
2to3
J
minor
tl
tl
I
7oPondHarvest
5
95
0
0
0
0
0
0
0
0
Table 3
Summaryof Examplesof PenaeidShrimpStockChangesFollowing
IntertidalWetlandChanges
Source
VegetationChanges
StockChanges
Quantiry,quality
Quantity,quality
Turnerunpub,
Quantity
Quantity
Morganand
Gucia,1982
Japan
None; mudflat
reclamation
Quantrty
Doi et al.,
r973
El Salvador
Quantity
Quantity
Daugherty,
r975
Vietnam
Quantity
Quantity
Norman,1983
Afea.
Louisiana
Kuwait and
SaudiArabia
Table 4
andSalinas
Areaof Mangrove,Camaroneras
(Valdivieso,no date)
in Ecuador,ckca1982-1984
Camaroneras
Province
lvlanglares
Salinas
Guayas
El Oro
Manabi
Esmeraldas
52,912
26,484
8,3't't
1,595
ttg,526
24,456
12,416
30,153
17,340
2,520
TOTAL
89,368
186,551
20,024
'y
Table 5
from
1966to 1982in Mangrove,Salinas
(in
hectares)
Changes
andOtherEstuarineZonesin aPilot StudyArea in El Oro
Province(from CLIRSEN, 1983)
Tnne
1966
r977
1982
Urban
Idangrove
Camaroneas
Rivers
Salinas
HighLand Vegetation
Agriculture
256.7
4,692.9
0.0
r,437.5
466.3
466.3
615.2
434.7
423t.7
834.0
r,514.5
333.8
333.8
130.2
588.5
3,294.r
2,330.6
r,465.7
r39.4
t62.6
634.7
TOTAL
9,556.3
8,548.6
8.555.1
Table 6
Variation in the Catchper Effort of SeveralDevelopedShrimpFisheries
(from GullandandRothschild,1984)
Countr.v
Ausralia
Austalia
Brazil-Guiana
Kuwait
SaudiArabia Balnain
Iran
Indonesia
Senegal
U.S.A.Gulf of Mexico
U.S.A.Gulf of Mexico
Ecuador
Coefficient
of Yaiation (.Vo)
Yean(n)
10
11
19
16
11
t2
9
t4
t2
t2
25
52
19.5
23.8
43.5
39.7
50.4
93.2
31.6
29.8
24.5
20.0
Species
Single
Single
Alt
All
All
All
All
All
Single
Single
All
Source
Pa&
42
43
61
74
74
75
La7
133
I&
l&
Table 7
Examplesof theEffect of Climateon
CoastalPenaeidShrimpStocLrs
Location
Species
Effecton Yield
North Carolina(U.S.A.)
P.drcrarum
Temperature
G)
Hettlerand
Chester(1982)
Louisiana(J.S.A.)
P. setiferus
Saliniryo
P. aztecus
Baneuand
Gillespie(1973)
Riverflow o
P. setiferus
Salinity(-)
Temperature(+)
Salinity (+)
Temperature(+)
Turner(1979)
P. aztecus
Salinity (-)
Temperature(+)
Salinity (+)
Temperature(+)
Copelandand
Bechtel(1974)
Florida(U.S.A.)
P. durarum
Waterlevel (+)
Browder(198Q
LagunaMadre,
Texas(J.S.A.;
hypersaline)
P. fluviatilis
P. aztecus
Rainfall (+)
Gunterand
Edwards(1969)
Ausralia
P. merguiensis
Rainfall (+)
Stapleset al.
(1e84)
Ruello (1973)
Indonesia
P. merguiensis
P. monodon
Riverflow (+)
Turner(L97,
Senegal
P. duorarum
Salinity (+)
Le Reste(1980)
Louisiana
P. aztecus
NorthernGulf of Mexico
(u.s.A.)
P. setiferus
r29
Source
Table 8
DrainageArea andPercentof the Total for the Major Rivers
in the Vicinity of the Guayasestuary(from Stevenson,1981)
River
Guayas
Jubones
Naranjal
Boliche
Arenillas
Area(km2)
Drainage
PercentTotal Area
32,800
4280
3,060
1,300
550
64.00
8.34
6.00
2.50
1.07
TotalVo= 81.91
130
Figure 1. Therelativedensityof penaeidshrimpstocksoff thecoastof Ecuadorby depthcontour(adapted
from datain LoeschandCobo,1972).
RELATIVE
DENSITIES
OF
P E N A E I DS H R I M P
O F FT H E C O A S TO F
ECUADOR
75- 100- 150- 200,|00 t50
200 300
(}I)
DEPTHCT]NTOUR
Figure 2. The relationship between intertidal vegetation and penaeid shrimp yields in Malaysia (adapted
from data in Jothy, 1984).
25000
}lALYAS
IA
20000
p2 =.74
15000
YIELD(T.tT)
r 0000
5000
0
25000
A R E A( H A )
1963Figure?. Thepercentof brown shrimp(P. aztecus)caughtin the inshorewatersof Louisianafrom
1976(NMFS statistics).
100
80
60
5 BRovl{
SHRI},IP
40
!
,/'\-t''/
I
20
U
1960
of intertidal landsin Japan(from
Figure g. The declineof shrimp yields in Japanasrelatedto reclamation
Doi, 1983).
C=| 353 - 6.3 Areo
1000
Annual
Catch(t)
500
50
Area(fm2)
Cumulotive
134
Figure9. The numberof trawlingvesselsin theindusftialshrimpfleet andthe carchper vesselfrom 1954
to 7984.
.0. TRAVLTI{G
.0. },ITIYESSEL
YESSELS
,trl.
50
c
AA
o/ \noo,y1
\
I
zoo
ll t..l \r/:1
,/
/\
;ll
I{BER {
HU
I
/\ Ai--
/ v'
o
o'o.o(
40
{ll
zn
Yw
HT
YESSEL
20
j,
t0
oL
YEAR1955 | 960 r96s t970 t975 t980 | 985
Figure 10.The distributionof horsepowerin theoffshoretrawlingfleet.
140
120
M rgso
f rgs+
100
80
KG/HR
YTELD
60
40
20
uPT0 200-290300-390400-490 )500
I eo
tilGrt{E
HORSIPOWTR
RAl{GE
135
at the
Figure 11.Annualchangesin the percentcatchwhich is P. vannameiwithin the Gulf of Guayaqu_il
nJttfrr* partof theGuli(zona de bofo) andthecentralandsouthernpart(zonade Playas)(from Cunand
Marin, 1982).
.O- ZOHADE GOLFO .O. ZOHADE PLAYAS
25
zv
l
15
PERCEI{T
t0
L
0
I 9 65
1975
1970
I 980
YEAR
hereis therelationship
Figure 12. Anexampleof climaticrelationshipswith shrimplandings. Shown
for Ecuadorfrom
per
vessel
catch
trawitsfreries
anO
fr4aictr)
through
betvreenwinter riverflo* il-u.f
high valuefor
very
in
a
yearresulted
1965to 19?9. The unotficialrec'ordof iatch in thelatestEl Nino
shownin this
riverflow
the
bevond
Curu"risessieeptyto the;ight,
CpUE (not shown),rrg;;;G;;h;itr,"
graph.
x + 40.42
U=-0.058
RZ= 0.52
DPUE
l'tT/ 30
T)
20
100
200
250
300
RIYERFL(}W
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139
140
A SUSTAINABLE SHRIMP MARICULTURE
INDUSTRY FOR ECUADOR
Edjttd by Stephen Olsen and Luis Arrlaga
Factors Affecting the Relative Abundance of Shrimp in Ecuador
Factores que Afectan la Abundancia Relativa del Camarón en el
Ecuador
R. Eugene Turner
Resumen
La producción de camarones peneidos en Ecuador tiene significación nacional, en términos de
volumen, valor y ocupación de mano de obra. Aunque la producción en piscinas aumento grandemente en
los últimos años, los datos disponibles sugieren que la producción por superficie (Kgha) ha declinado
significativamente. Desde la perspectiva del manejo del recurso, las preguntas claves comprenden: ¿Cuáles
son los impactos de la tala del manglar?; ¿Cuál es la variación natural en el reclutamiento?;¿Se puede
aumentar el suministro de postlarvas naturales?; ¿Cómo influye la captura de postlarvas y juveniles en el
tamaño del "stock?.
Después de presentar informaciones sobre el ciclo biológico del camarón y las relaciones del
reclutamiento en abiente natural, el autor trata sobre los efectos de áreas pantonosas costeras en el
reclutamiento del camarón, sosteniendo que el crecimiento y la supervivencia de las postlarvas en los esteros
constituyen, probablemente, los factores más importantes que afectan a la magnitud de la población adulta.
Se incluyen ejemplos de Malasia, Filipinas y Golfo de México (Luisiana),en los cuales se demuestra que los
rendimientos a largo plazo están relacionados linealmente tanto a la calidad como a la cantidad del habitat
intermareal.
Asunto relevante, además de la riqueza orgánica del ecosistema de manglar, es la protección que
porporcionan las estructuras de la planta a los camaronerosjuveniles, conforme ha sido demostrado en
experimentos sobre la relación predador-presa, que son citados en el trabajo.
Se analiza la influencia del clima sobre las fluctuaciones anuales del "stock" de camarones,
estableciéndose que en el Ecuador hay una baja variación anual (20%)de la "capturapor unidad de esfuerzo"
(CPU), en comparación con la de otros países (hasta un 90%). La presencia o ausencia del fenómeno de El
Niño, es determinante en las variaciones anuales.
En las conclusiones, el autor expresa que la conservación de la "cantidad de habitat" es altamente
significativopara mantener el éxito sostenido en el reclutamiento de los "stocks", puesto que parece que la
extensión del habitat es el factor determinante de las densidades potenciales del "stock natural, que son
modificadas anualmente por influencias climáticas.
En consecuencia, la recomendación del autor es la conservación de las zonas de manglares, si el
Gobierno desea prevenir grandes cambios en los "stocks" de postlarvas, juveniles y adultos. Donde sea
posible, el manglar debe ser restribuído mediante el restablecimiento de la hidrología natural. La zona de
amortiguación del manglar alrededor de las áreas taladas debería ser al menos el doble del área talada.
También, concluye en que la industria del camarón presenta signos del aumento de conflictos entre
usuarios de los recursos, necesitándose datos precisos para lograr el éxito en la interacción entre todas las
partes interesadas.
Finalmente, recomienda divulgar técnicas para aumentar el suministro de postlarvas mediante la
disminución de la mortalidad durante su manipuleo.
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September 1, 2006
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Citation:
Turner, R. E. (1989) Factors Affecting the Relative Abundance of Shrimp in Ecuador.
In Olsen, S. and Arriaga, L., editors. A Sustainable Shrimp Mariculture Industry for Ecuador.
Narragansett, RI: Coastal Resources Center, University of Rhode Island.
Introduction
extensivelythroughouttheEcuadoriancoastalzonefrom boatsandin ponds
Penaeids
areharvested
built within the mangrovelinedestuaries.The harvestis of nationalsignificancein termsof volume,value
questionshavearissnasthe
andemployment(Sutinenet al., this volume), Resourcemanagement
depleting
thepondoperators-of
fishermen
have
accused
trawl
For
example,
mariculiuresystemdeveloped.
(PL) andjuvenilesto supplythe ponds. As manyas90,000to 120,000
stocksof wild shrimppostlar'rrae
peoplemay be involvedin postlarvaecollectioneachyear,andtheeffectson the shrimppopulationis
haveled to seriouseconomicdifficulties,particularlyfor the pond
unlinown. RecentPL shortages
percent
thepondswereidle dueto a shortageof wild-caughtpostlarvae,which
of
in
1985,
50
operalors;
(-iPuma andMeltzoff, 1985). Many of thepondsare
representup to one-halfof pondoperationexpenses
(Cintro1,1981)and
of theestuarineecosystem
itimangtoni zoneswhich areveryproductivecomponents
ponds
dramatically
increased
in
the
Although
catches
including
shrimp.
fauna,
contrib;6gto both flora and
thatthearealrateofproduction(kg/ha)for all pondshasdeclined
in recentyears,the availabledatasuggests
significantly.Thereareseveralreasonsfor this decline:
.
Thebestsitesmay haveakeadybeenchosenleavingonly ttrepoorestsitesfor later
development.
.
or neverused.
For economicreasonspondsmaybe abandoned
. The statisticsarenot accurate'
. Pondoperatorsarenow relying moreon naturalstockingofponds throughtidal action
thanon stockingwith caughtlarvae.
stepswerenot takenbefore
. Pondfertility is depletedafterthreeharvests,
andmanagement
seedingthefourthproductionperiod.
of
.
and,therefore,wersnot countedin earlierestimates
Mostpondswereunauthorized
ProductivitY'
Informal exportsof shrimpthroughPeru,amongothercountries,havealsocontributedto
this skewedappeafince.
concemingtherelative
perspective,
thekey questionsto be addressed
Froma resourcemanagement
stocks
are:
natural
shrimp
of
abundance
. What arethe impactsof clearingmangroves?
. What is thenaturalvariationin recruitment?
.
Canlhe naturalpostlarvaesupplybe increased?
.
How muchdoesthe harvestof postlarvaeandjuvenilesinfluencethe offshorestock size?
.
Life Cycles of Wild Penaeid ShrimP
Shrimpbeginlife in the openseaaseggswhich maturethroughnaplius,protozoealandzoeal
wate6
stages.lfter Oriftirigduringthepelagiclarvalphases,thepostlarvaeenterlower-salinityestuarine
next
the
until
cling
they
which
to
roots,
mangroue
as
such
iubsrates,
nutrient-iich
seek
and
on"floodtides
growing
(bottom-dwelling),
tide takesthemdeeperinto the estwfy. Eventuallyttreshrimpbecomebenthic
retum to the
ttrefood-riin andpredator-r.ifotqOenvironment.Afier severalweeksor months,they
G;ir
postlarvae
as
from
estuaries
shrimp
harvest
(Figure
Fishermen
1).
zones
oc|an-reruining in the rt'uUo*
reasons
For
for stockingpon-ds,or as subadultsandadultsin the nearshoreand openoceanicwaters.
to be estuarinedependent'
penaeidshrimpareassumed
below,most;ommercially-important
discussed
by
is widely acknowledged
major.fisheries
to
suppoit
ateas
Thecapabilityof estuarinemangrove
in
congregate
fisheries
important
commercially
of
many
TheJuveniles
scientists,but nbt weli understood.
for
more
adaptable
species
-3[ti*p,
anOiefugefrom predators.Suc[ behaviormakesthese
shallowzonesfor feeOing
of favorableshallowwaterhabitatsduring
iti'patticuiat,takeadvantage
maricuttureop"rutions.
postlarvaearepresentvirtually all year
shrimp
thai
revealed
have
studies
criricallife cyclestages.Various
in relationto the lunar,diurnalandtidal cycles'
in mangrovewaters,uitttougttnumbersfluctuateseasonally
r22
Shrimp Recruitment Relationships
Penaeidshrimpstockssufferthe greatestmortalitywhenthe organismis smallest.In many
fisheries,variationsin recruitmentof an agegoup into theexploitedstockis drivenby adultspawning
biomasssize. But stockrecruitmentrelationships
for penaeidshrimparenot clearlydemonstrable
(Garcia,
1983)becausetheadultstocksizeis determinedby thechangesin juvenile,evenpostlarvaeabundance,
and
is not primarily relatedto changesin adult spawningbiomass.
However,therearereasonablecausalrelationshipsbetweenlarval andjuvenile abundances
andthe
subsequent
densities(GarciaandLeReste,1981).In turn,the stockrecruitmentsuccess
is clearlydependent
on climaticfactors,predationlevels,food supplyandhabitatquality. Of these,thoughnot preciselydefined
for penaeidshrimp,habitatis considered
theprincipallong-termfactorinfluencingsustainedshrimp
harvests.ShSmpmariculturein Ecuadormay havecontributedto thechangein thedominantspecies,from
Penaeusoccidentalisto P. vannamei.P. vannameiis moreadaptableto coastalpondsenvironments,
and
inefficienttechniquesmay releaseto theestuary1,000poundsof IO-ZOgrampreadultshrimpduringthe
harvestof a single10hectarepond.
Effects of Coastal Wetland Area on Recruitment of Penaeid Shrimp Stocks
Coastal Wetland Area and Shrimp Stock Size
Researchers
agreethatlarvalshrimpmovementandrecruitmentfrom the spawningsitesoffshore
.
into_estuaries
ar9nrobablythemostimportantfactorsaffectingtheharvestable
adulipopulition size(Garcia
andLeReste,1981;Garcia,1983;TumerandBrody, 1983).Alrhoughestuarinesafiriityandtemperarure
changesaffecttheannualpotentialfor postlarvaesurvival,tie long-iermyieldsarelinearlyrelatedto both
thequantityandqualityof intertidalhabitat. Despitethedifficulty in obtainingreliablemeasures
of fishing
effort andlandings,thereareseveralexamplesof ttrehabitat-yieldrelationship?roughout
theworld.
Jothy(1984)providesdatafrom Malaysiarelatingmangroveareaandshrimpyields(Figure2).
Althoughtheauthordoesnot describethetime periodof 6e shrlmphndingsdatanor itreu-iont of fishing
effort, thereis a clearrelationshipbetweenshrimplandingsandmangroveareain eachof the statesalong
Malaysia'scoastline.
PaulyandIngles(1986)compiledsimilarstatisticsfor thePhilippinesandthe samerelationship
holdsbetweenshrimplandingsandmangrovezoneGrgure3). Theresearchers
live in ttrefhilippines and
hadaccessto lon-g-term
dataon bottrtheartisanalandcommercialrawl catches.They etiminatedunder-and
over-reportingof catchdataandthe abuseof mangrovearealestimatesfor economicinterestsconcernedwith
Lhemangrovelumberconcession.
- . Long-termdataandmonitoringfrom theentirenorthernGulf of Mexico arealsoavailable.The
areaof intertidalvegetationis alsowell knownthroughseveralsurveyssince1960,with theareaof
vegetationdirectlyandlinearlyrelatedto the tidal landingsin anyoneyear@igure4). The vegetationin
theseestuariesis not dominatedby mangroves(exceptin isolatei casei;. rirer.-e
is alsono sign'ificant
relationshipbetweenwatersurfaceareaandlandings,exceptfor a possibleinverserelationshi'p.In addition,
the speciesof shrimpcaughtaredirectlyrelatedto itre tdnosof intertidalcoastalvegetationin^eacharea.
The samedirectrelationship
betweencommercialharvestsof penaeidshriilp andintertidal
vegetationis foundworldwide,thoughit changeswith latitude,rising with decreasing
latitudeuntil around
5o N/S whereit declinesSigure 5).
. . The importantcommercialspeciesin Ecuadorarelistedin Table1 anddistributionof harvestby
speciesis shownin Table2.
The relationshipsof wetlandareato penaeidshrimpyields havebeenindirectly testedttrrough
large-scale
changesin wetlandareas.Severalexampleshavebeendocumented
with vaiiousOeg.ees
of
success(Figure6, Table3).
In Louisiana,the coastalwetlandlossrateis 0.8percentper year(Craiget al., 1979;Tumer, 1979,
1982;Turneret al., 1982). Changesinvegetationate accompanied
by changesi-nthe shrimp'catchin direct
relation_lothe lossor gainof wetlandsin eachestuary.Therearealsodemoistratedrelationships
between
the qualityof estuarinewetlandsand shrimpcatch. Due to thelossof wetlandareasoverthepast30 years,
r23
increasein brackishshrimpspecies(Figure
moresalt-lolerantvegetationhasdominated,with accompanying
7).
In Japan,Doi (1983)showedthat the declinein yieldsof P. japonicuswasproportional!o land
shallow
reclamationin theestuaryGigure 8). However,theintertidallandwasmostlyunvegetated,
in
in therecruitmentof P. semisuculatus
mudflats.MorganandGarcia(1982)noteda long-termdecrease
Kuwait andSaudiArabiarelatedto estuarinelandreclamation.In El Salvador,mangroveswereclearedfor
agricultureandthe shrimpfisheriesdeclined,ttroughthe fisheriesanalysisis far from completedueto
difficulty in obtaininggoodestimatesof landingsandeffort (Daugherty,1975).
Finally, in thePeople'sRepublicof Vietnam,the chemicaldefoliationof the southerncoastalzone
lossof mangroves.Thoughtheanalysisis not generallyavailable
duringthelatestwar causedwidespread
review,
for
there
apparentlywasa severedeclinein coastalfisheriesstocks,
community
to the scientific
includingshrimp(Norman,1983).
Causal RelationshipsLeading to the Wetland-Stock Relationships
interactionsin wetlandsshowsimilarpattemsin shrimpyields.,For
Experimentsin predator-prey
numbersof
estuarywith leveesor bulkheadsresultin decreased
from
the
off
*etlands
btocted
example,
adult stnimpat the alteredsites(Mock, 1967;Trentetal.,1976). Althoughthe wetlandedgeis particularly
high in organics,a moreimportantfactormay be theprotectionfrom predatorsthatplant structuresoffer
th6 shrimf. Field andlaboritory predator-preyexperimentswith P. ^ztecusin vegetatedandnon-vegetated
saltmarshhabitatsindicatethat smalljuvenileshideamongplant stemsto escapepredators(Minello and
ZimmermanandMinello, 1984;Zimmermanet al., 1984;MinelloandZimmerman,
Zimmerman,1983a,b;
predatorattackson prey declineswith increasingvegetationcomplexity'
1985). The numberof successful
Thuswetlandhabita6appearto be favoredsitesfor juvenile shrimp,which is consistentwith observations
in thepresenceofpredators(Charnovet al., 1976). These
of organismadaptationio resourcedepression
areafo observedfor freshwaterlakeswith wetlandsfringingtheirborders,coralreefs,seagrasses
tespo-nses
1978;SavinoandStein,1982;Strangeetal., 1982;
1978;Johannes,
und.iu"rr (GroenandSchmulbach,
Hoyer
RobbleeandZieman,1984;
Huston,1984:
Holland
and
Duroucher,1984;HeckandThomas,1984;
1985).
Tumer,
Risotto
and
et al., 1985;
Mangrove
Loss and Postlarvae and Adult
Supply
Doesdeclinein shrimplandingsor postlarualsupplyfollow the lossof mangrovesdueto
mariculturepondconstructionfTo addressthis question,it is worthwhileto determinethe changesin
arbassincesignificantpondconsfuctionbeganin or about1976.
mangrove
The declinein irangroveareain Ecuadorasa directresultof theconstructionof maricultureponds
in tle mangove zoneis estiiratedat 10.6percenrby Alvarez(his yolgme). Valdiviezo(no date)estimated
and89,368ha of brackishwatermariculture
tlratthereiete a total of l75,2Lghectares(ha)of mangroves
River estuary(CLIRqEry,1983)indicates
the
of
Guayas
study
1982.
One
ponar (fuUf" 4) in Ecuadorasof
in mangroves(Tab195). Assumingthat
1982-83
occurred
1966
to
from
pond
the
16'perceniof
ihat
$owth
abouttb percentof thi pres6ntmariculturepondsarein formermangrovezones,thenabout9,000ha of
areno longerfunctioningasa forestedwetlandecosystem..
mangroves
Is this estimited10.6percJntdeclinein mangrovematchedby an equivalentdeclinein shrimp
for
presentlandings.statistics
landingsor postlarvalsupplies?This is a difficult questionto address-with
(Figure
the
years
9),
15
last
Ecuad6r.Alttrougtrthe riwl effort hasremainedsomewhatconstantfor the
-t.t p". unit eff6rt (CPUE)hasfluctuated;but naturalvariationsin a varietyof fisheriesstocks,especially
shrimp,
' fluctuateat least20 percentin any oneyear.
Further,the 10.6peicent declinei in mangrovearecumulative. In 1980declineswereonly around
1.0percent,so the impact'of*angroue lossis relativeto annualenvironmenlalfluctuationsthat affect
stocls. Evenso, the CPLIEin the last severalyearsis lower thanaverage.
Anotherquestionis whetheror not fishingeffort in thelast few yeat!.!T remainedconsunt.
for a changingeffort, as wetl asvesselnumbers,it is difhcult to separateout the
Wittroutcotnpensuting
relativeinfluencesof 6tmate,effort anOmangrovedecline. Certainlythe effort hasnot beencomp-letely
haschangedsince1980(Figure10)'
constantbecausethe sizeof tireboats(measuedin horsepower)
Effects of Climate on Annual Fluctuations of Penaeid Shrimp Stocks
Natural Variations in Stock Size
Adult stockharvestsmay vary asmuchas 100percentfrom yearto year. Table6 showsthe
coefficientof variationfor ttreEcuadorianfawling fleetandseveralotherworid shrimpfisheries.The
Ecuadorfleet hasa very low variationin CPUEof 20 percentcomparedto up to 90 percentelsewhere.
Clewly therehasbeenhigh stabilityin recruitmentovbr the 1xt25 yearsin bcuadoi. However,thereis
still muchvariationfrgm yearto year. Understanding
the factorsleadingto this variationis importantto
the management
of this fishery.
It is now well documented
thattheselargeannualvariationsareassociated
with changesin
estuarineconditions.Variationin estuarinesalinityandtemperature
arethebest-documented
climatic
influencesCtable7), but thefrequencyandintensityoffrontal passages,
river discharges
or subs6ate
conditionsmay alsobe important.Numerousdataon CPUEareauailable(e.g.,Gullind andRothschild,
1984;Kapetsky,1981;KapetskyandLasserre,1984a,b),but rhereis no systdmaticandcomparative
analysisof climaticinfluences.CopelandandBechtel(1974)analyzedttreiatinityandtemperature
preferences
of severalpenaeidspeciesin estuaries
of thenorthernbulf of Mexi.o. rtr"/
demonstrated
the interactiveoptimalpreferences
"i6atiythanlinear
by shrimpfor temperature
andsalinitn rather
relationships
dominatedby one factor.
Cun andMarin (1982)examinedfisheneslandingsdatato determinetheannualchangesin the
c_atch
of P' stylirostrisin thenorthern(zonade Golfo),cenral and southernparts(zonadephlas) of the
Gulf of Guayaquilbetween1965and 1979(Figure11). Theinrerannualvariationiwerehigtrandtherewere
differencesin speciesdominancebetweenareai,thoughthereasonsarenot yet understood.
Dataon theflow of theJubonesRiver,which entersthe Guayaseituary(Table8) wasused
asa
sturogatefor regionalvariationsin rainfall andtemperature,
demonsratingan inverscretaiionitripwittr
riverflow and CPUE(seeatsoFigure 12). SinceEi Nino uiually bringswet and warmweather,
these
eventsseemto indicatettratsucheventsareunfavorablefor shrimpre6ruitment.However,themostrecent
El Nino eventsof the80sresultedin very high valuesof CPIIE, but arenot includedhere
becauseof the
lack of riverflow data.
analysisof effectsof climateon
_Trgmajorpoint or this figure is to encourage
ElugdgrianshrimpCPUE(aswell asottrerspecies).This upprouclihu,prbuenfeasibleelsewhere(e.g.,
Table7).
rmplications for Managementof penaeid shrimp stocks
The optionsavailable_to
penaeidshrimpmanagers
mightbe describedasbeingof threetypes:
economic,or
processing
and
management;
personnel,or slocio-cultural
manageme-nq
anOtrauitat
{9e1
management.Habilatmanagementis
emphasized
here. Theprimarycauseof cha-nges
in thesewetlandsare
manmadeactivitiesandmay,therefore,be manageable.
Without moreatrcnrionto-habitat,thefirst rwo
concernswill becomelessimportantandmoredifficult to implement.As the potentialcrop
of bottr
posflarvaeandaduls decreases
with wetlandlosses,optionsto *anrge whateverremains
becomemuch
morelimited.
Penaeidshrimpmanagersshouldregardhabitatmanagement
astheirprimaryresponsibility.
.
ottrerwise,theywill befacedwith trying to dividefewerandfJ*"t rto.tr amongmore
an6morepeople,
especiallyfishermen,while watchingtheir well-designed
but slaticmanagement
plansfalter with changing
environmentalconditions.
Conclusions and Recommendations
Below aresomeconclusions
andrecommendations
basedon thereviewof penaeidshrimpbiology
andthepresentsituationin theEcuadorianfishery. Thesewill necessarily
be broadiystatedsince
personnel,politics and
implementationmustbe flexible to reflectlocal variationsin economies,
environment.
Conclusion:Penaeidshrimprecruitmentfrom larvaeto adultis srongly influencedby
1.
adultstocksizesis supported
habitatqualityand quantity. The hypothesisthathabitatquantitydetermines
of habitat
Conservation
from
ecosystem.
removal
the
wetland
by limited neld otservationsfollowing
quantity is of high significanceto sustainedstockrecruitmentsuccesssinceit seemsto be the final
diterminantof riaturalpotentialstockdensitieswhich climaticinfluencesmodify annually.
if thegovernmentwantsto avoid
Mangrovezonesmustbe conserved
Recommendations:
is probablyat its naturallimit,
juveniles
harvest
Stock
and
adults.
postlarvae,
of
major changesin stocks
is in order.
stocks,
few
remaining
of
the
further
exploitation
rather
tlan
conse*:ation,
and
of the
shouldbe restoredttrroughreestablishment
Wherepossible,mangroves
naturalhydrologY.
Mangrovebufferzonesaroundclearedzonesshouldbe at leasttwicethelevee
width andincludettrelevee'
.
.
Conclusion:The shrimpindustryin Ecuadoris expansiveandintensive,andshowssigns
Z.
involvedto
of increasinguser-useconflict. Minimizition of cbnflict is possiblebut all partiesmustbe
succeed'
interaction
to
for
this
is
required
optimizeintEractions.Accuratedata
Anlntegratedstudyplanwhich includesall usersandall aspegpof
Recommendations:
conflictsare
since-resource
mustiepresenttheecosystem
theenvironmentshouldbe developed.Oneag-ency
quality;
the
water
and
mangroves
e.g.,
resource,
the
common
prtAffy 6ur"d on individualexploirationof
of
vmiety
for
a
implications
long-lasting
have
use
and
resource
ir*.r itr .omplicated,involve^multiple
social,political andnaturalresources.
.
.
.
.
3.
4.'
Determineif thedeclinein kg/haof pondsis real. If not, determinewherethe
dataareincorrect. Canthis situationbe rectified? If the declineis real, what are
thereasonsbehindit? Are theyecological,economicor political?
Examinethe existingdatato seeif thereareany otherdatawhich could be
for long-termanalysis.
summarized
Develop a completefisheriesstatisticalanalysisandcontinuedatacollection.
effort to formalizea captain'slog book to
Supportthe newly-established
summarizefishing efforfi trips, hours,etc'
changes
Conclusion:The variationsarehigh enoughnow to masktherelativelysmaller
in stocksizedueto presentreductionsin mangrove'
in stocks
Recommendafl;: I; ;alysis of the effectsif climateon the annualvariations
oceanic
of
the
effects
examine
usefullo
especially
be
tt
would
shouldbe.o*pt.i"A.
anomalieson shrimpandon otherstocks'
temperature
withoutexploitingadditionalmangrove
Conclusion:postlarvaesuppliescanbe increased
andbeforeinftoductioninto ponds'
capture
postlarvae
after
tossbt
the
zonesby reducing
to increasethe supplyof postlarvaeby
no.utgaie techniques
Recommendatioti:
the mortalityof thosecaught.
decreasing
126
Table 1
List of Shrimpof CommercialImportance(lrtcPadden,1985)
CommonName
Family
Species
Blanco
Peraidae
Penaewvannamiei
P. stylirostris
P. occidentalis
Cafe
Pernidae
P. californiensis
Rojo
Penaidae
P. brevirostris
Zpbn
Penaidae
Trachypenaeus
byrdi
T. pacift,cus
T.face
Pomada/Titi
Peraidae
Xiphopenaeus
riveti
Protrachypettaeuspr ecip tn
Carapachudo
Solonoceridse
Solonoceraspp.
CamronesdeProfundidad
Pmdalidae
Heterocarpusspp.
Table 2
Distributionof ShrimpSpeciesin Marineandpond Harvests
(fromM. Cobo,mimeoreport)
Species
P. occidentalis
P. styliorstris
P. vannamei
P. califurniensis
Trachypenewbyrdi
T.faoea
T. similispacificus
Xtphopeneus
riveti
Pr otrachypene
pr ecipua
Solenoceraflorea
7oCommercial
Catch
70
15to 20
2to3
J
minor
tl
tl
I
7oPondHarvest
5
95
0
0
0
0
0
0
0
0
Table 3
Summaryof Examplesof PenaeidShrimpStockChangesFollowing
IntertidalWetlandChanges
Source
VegetationChanges
StockChanges
Quantiry,quality
Quantity,quality
Turnerunpub,
Quantity
Quantity
Morganand
Gucia,1982
Japan
None; mudflat
reclamation
Quantrty
Doi et al.,
r973
El Salvador
Quantity
Quantity
Daugherty,
r975
Vietnam
Quantity
Quantity
Norman,1983
Afea.
Louisiana
Kuwait and
SaudiArabia
Table 4
andSalinas
Areaof Mangrove,Camaroneras
(Valdivieso,no date)
in Ecuador,ckca1982-1984
Camaroneras
Province
lvlanglares
Salinas
Guayas
El Oro
Manabi
Esmeraldas
52,912
26,484
8,3't't
1,595
ttg,526
24,456
12,416
30,153
17,340
2,520
TOTAL
89,368
186,551
20,024
'y
Table 5
from
1966to 1982in Mangrove,Salinas
(in
hectares)
Changes
andOtherEstuarineZonesin aPilot StudyArea in El Oro
Province(from CLIRSEN, 1983)
Tnne
1966
r977
1982
Urban
Idangrove
Camaroneas
Rivers
Salinas
HighLand Vegetation
Agriculture
256.7
4,692.9
0.0
r,437.5
466.3
466.3
615.2
434.7
423t.7
834.0
r,514.5
333.8
333.8
130.2
588.5
3,294.r
2,330.6
r,465.7
r39.4
t62.6
634.7
TOTAL
9,556.3
8,548.6
8.555.1
Table 6
Variation in the Catchper Effort of SeveralDevelopedShrimpFisheries
(from GullandandRothschild,1984)
Countr.v
Ausralia
Austalia
Brazil-Guiana
Kuwait
SaudiArabia Balnain
Iran
Indonesia
Senegal
U.S.A.Gulf of Mexico
U.S.A.Gulf of Mexico
Ecuador
Coefficient
of Yaiation (.Vo)
Yean(n)
10
11
19
16
11
t2
9
t4
t2
t2
25
52
19.5
23.8
43.5
39.7
50.4
93.2
31.6
29.8
24.5
20.0
Species
Single
Single
Alt
All
All
All
All
All
Single
Single
All
Source
Pa&
42
43
61
74
74
75
La7
133
I&
l&
Table 7
Examplesof theEffect of Climateon
CoastalPenaeidShrimpStocLrs
Location
Species
Effecton Yield
North Carolina(U.S.A.)
P.drcrarum
Temperature
G)
Hettlerand
Chester(1982)
Louisiana(J.S.A.)
P. setiferus
Saliniryo
P. aztecus
Baneuand
Gillespie(1973)
Riverflow o
P. setiferus
Salinity(-)
Temperature(+)
Salinity (+)
Temperature(+)
Turner(1979)
P. aztecus
Salinity (-)
Temperature(+)
Salinity (+)
Temperature(+)
Copelandand
Bechtel(1974)
Florida(U.S.A.)
P. durarum
Waterlevel (+)
Browder(198Q
LagunaMadre,
Texas(J.S.A.;
hypersaline)
P. fluviatilis
P. aztecus
Rainfall (+)
Gunterand
Edwards(1969)
Ausralia
P. merguiensis
Rainfall (+)
Stapleset al.
(1e84)
Ruello (1973)
Indonesia
P. merguiensis
P. monodon
Riverflow (+)
Turner(L97,
Senegal
P. duorarum
Salinity (+)
Le Reste(1980)
Louisiana
P. aztecus
NorthernGulf of Mexico
(u.s.A.)
P. setiferus
r29
Source
Table 8
DrainageArea andPercentof the Total for the Major Rivers
in the Vicinity of the Guayasestuary(from Stevenson,1981)
River
Guayas
Jubones
Naranjal
Boliche
Arenillas
Area(km2)
Drainage
PercentTotal Area
32,800
4280
3,060
1,300
550
64.00
8.34
6.00
2.50
1.07
TotalVo= 81.91
130
Figure 1. Therelativedensityof penaeidshrimpstocksoff thecoastof Ecuadorby depthcontour(adapted
from datain LoeschandCobo,1972).
RELATIVE
DENSITIES
OF
P E N A E I DS H R I M P
O F FT H E C O A S TO F
ECUADOR
75- 100- 150- 200,|00 t50
200 300
(}I)
DEPTHCT]NTOUR
Figure 2. The relationship between intertidal vegetation and penaeid shrimp yields in Malaysia (adapted
from data in Jothy, 1984).
25000
}lALYAS
IA
20000
p2 =.74
15000
YIELD(T.tT)
r 0000
5000
0
25000
A R E A( H A )
1963Figure?. Thepercentof brown shrimp(P. aztecus)caughtin the inshorewatersof Louisianafrom
1976(NMFS statistics).
100
80
60
5 BRovl{
SHRI},IP
40
!
,/'\-t''/
I
20
U
1960
of intertidal landsin Japan(from
Figure g. The declineof shrimp yields in Japanasrelatedto reclamation
Doi, 1983).
C=| 353 - 6.3 Areo
1000
Annual
Catch(t)
500
50
Area(fm2)
Cumulotive
134
Figure9. The numberof trawlingvesselsin theindusftialshrimpfleet andthe carchper vesselfrom 1954
to 7984.
.0. TRAVLTI{G
.0. },ITIYESSEL
YESSELS
,trl.
50
c
AA
o/ \noo,y1
\
I
zoo
ll t..l \r/:1
,/
/\
;ll
I{BER {
HU
I
/\ Ai--
/ v'
o
o'o.o(
40
{ll
zn
Yw
HT
YESSEL
20
j,
t0
oL
YEAR1955 | 960 r96s t970 t975 t980 | 985
Figure 10.The distributionof horsepowerin theoffshoretrawlingfleet.
140
120
M rgso
f rgs+
100
80
KG/HR
YTELD
60
40
20
uPT0 200-290300-390400-490 )500
I eo
tilGrt{E
HORSIPOWTR
RAl{GE
135
at the
Figure 11.Annualchangesin the percentcatchwhich is P. vannameiwithin the Gulf of Guayaqu_il
nJttfrr* partof theGuli(zona de bofo) andthecentralandsouthernpart(zonade Playas)(from Cunand
Marin, 1982).
.O- ZOHADE GOLFO .O. ZOHADE PLAYAS
25
zv
l
15
PERCEI{T
t0
L
0
I 9 65
1975
1970
I 980
YEAR
hereis therelationship
Figure 12. Anexampleof climaticrelationshipswith shrimplandings. Shown
for Ecuadorfrom
per
vessel
catch
trawitsfreries
anO
fr4aictr)
through
betvreenwinter riverflo* il-u.f
high valuefor
very
in
a
yearresulted
1965to 19?9. The unotficialrec'ordof iatch in thelatestEl Nino
shownin this
riverflow
the
bevond
Curu"risessieeptyto the;ight,
CpUE (not shown),rrg;;;G;;h;itr,"
graph.
x + 40.42
U=-0.058
RZ= 0.52
DPUE
l'tT/ 30
T)
20
100
200
250
300
RIYERFL(}W
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