圍網(wǎng)使用人工聚集器對於小型鮪類的開發(fā)及在熱帶東大西(共29張PPT)

Exploitationofsmalltunasbyapurse-seinefisherywithfishaggregatingdevicesandtheirfeedingecologyinaneasterntropicalAtlanticecosystemF.Ménard,A.Fonteneau,D.Gaertner,V.Nordstrom,B.Stéquert,andE.MarchalICESJournalofMarineScience,57:525-530.2000圍網(wǎng)使用人工聚集器對於小型鮪類的開發(fā)及在熱帶東大西洋攝食食性之研究Reporter:謝佳樺第1頁，共29頁。WhatisaFAD？第2頁，共29頁。Forcenturies,menhavenoticedthatfishtendtogatheraroundobjectsfloatingonthesurfaceoftheocean,suchaslogs,debris,etc.Thisnaturalphenomenonhasbeenexploitedbyfishermenforalongtimetohelpthemdetectandcatchfish.Fishermenthenstartedtobuildartificialfloatingobjects(buoys,rafts,etc.).第3頁，共29頁。WCPFCWCPFCWCPFC第4頁，共29頁。(FADIO/IRD-Ifremer/M.Taquet)(FADIO/IRD-Ifremer/D.Itano)(FADIO/IRD-Ifremer/D.Itano)(FADIO/IRD-Ifremer/D.Itano)第5頁，共29頁。WesternandCentralPacificFisheriesCommission

SCG2a)FADsincreasetheefficiencyofpurseseineeffortfortunaincludingskipjack.圍網(wǎng)漁業(yè)使用FAD作業(yè)會提昇鮪類捕獲效率b)Thespeciescompositionofpurseseinesetsonfloatingobjects(includingFADs)isdifferenttothoseonunassociatedtunaschools.InparticulartheproportionofbigeyetunainthecatchismuchhigherforFAD-setsthanunassociatedsets圍網(wǎng)使用FAD補獲之漁獲物，其魚種組成及混獲種類較捕撈浮水群複雜，特別是大目鮪幼魚混獲比率會提高c)Purseseineandotherfishingaroundfloatingobjectsresultsinjuvenilebigeyetunabeingfishedbymultiplegears.大目鮪幼魚隨漂浮物洄游，造成多種漁法可捕獲大目鮪幼魚d)ThedeploymentofFADshascompoundedthedifficultiesofassessingCPUEtrendsforpurseseinefisheriesandhenceundertakingstockassessmentforskipjack,bigeyeandyellowfintuna.FAD的使用導(dǎo)致評估圍網(wǎng)漁業(yè)CPUE變動趨勢的準(zhǔn)確度，並致使無法準(zhǔn)確估計正鰹、大目鮪、及黃鰭鮪的資源e)Purseseinesetsaroundfloatingobjectshavemuchhighercatchesofnon-targetspecies(both

intermsofspeciesdiversityandtotalweight)thanpurseseinesetsonunassociatedtunaschools.圍網(wǎng)使用漂浮物捕撈鮪類，其非目標(biāo)魚的比例增加f)FADsmayalterthemovements,feedingandotherbehavioursoftunaresultinginarangeofeithernegativeimpacts(e.g.tunamaybecome“trapped”inunproductivewaters,onsmalland/orlargespatialandtemporalscales,reducinggrowthandpossiblyincreasingmortality)orpositiveimpacts(e.g.FADsmayprovideadditionalmeetingpointsthatassistinschoolingandspawning).FAD可能會改變鮪類洄游、攝食及其他行為，使在FAD周圍洄游魚群成長減緩及死亡率增加，而對資源產(chǎn)生負(fù)面影響;但FAD的聚集效果使魚群容易成群並增加生殖機會Impactsonfisheries第6頁，共29頁。WhydofishaggregateunderFADs?HypothesesonFADs1.Shelterfrompredator:Theobjectcanbeusedbythepreyasarefuge.2.Concentrationoffoodsupply:Afloatingobjectoraseamountaggregatespreyinitsclosevicinityonwhichlargefishcouldfeed.3.Indicatorlog:Naturalfloatingobjectsareoftenindicatorsofproductiveareas.4.Spatialorientation:Floatingobjects,underwaterstructuresorseamountsprovidespatialreferencesaroundwhichfishcanorientintheotherwiseunstructuredpelagicenvironment.5.Meetingpoint:Tunacanmakeuseoffloatingobjectstoincreasetheencounterratebetweenisolatedindividualsorsmallschoolsandotherschools,toformlargerschools.From:FADIO第7頁，共29頁。OutlineBackgroundObjectivesMaterial&MethodResultDiscussionandConclusions第8頁，共29頁。Background

第9頁，共29頁。1.Therehadbeennosurfacefishingactivityintheareauntil1975.Since1991,fishingoperationsonschoolsoftunaassociatedwithFADshasbecomewidespreadandthisoffshoreareahasdevelopedintoamajorfishingzone.Background第10頁，共29頁。Figure1.Meanannualcatch(t)associatedwithFADsper1squareofyellowfin,skipjack,andbigeye,1991–1996.Background第11頁，共29頁。

Background第12頁，共29頁。Objectives第13頁，共29頁。TogiveanoverviewoftheFADtunapurse-seinefisheryintheSSA.Toestimatetheby-catchusingscientificobserverdatacollectedduring1998.TodescribethefeedingecologyoftunasassociatedwithFADsbasedonstomachcontentdata.

Objectives第14頁，共29頁。Material&Method第15頁，共29頁。1.FisherydatawereobtainedfromlogbooksofpurseseinersoperatingintheEasternAtlanticOceanfrom1991to1997.2.WeuseddataobtainedduringtheEuropeanUnionbigeyeresearchprogrambyFrenchscientificobserverstoestimateby-catchanddiscardsgeneratedbyFADfishingduring1998.3.Thelengthofeachfishsampledwasmeasuredandthestomachwaspreservedinformalinordeep-frozen.Stomachcontentsweresorted,identifiedtothelowestpossibletaxa,counted,andweighed.Material&Method第16頁，共29頁。Results第17頁，共29頁。

1.Purse-seinecatchesinSouthSherbroarea

MeanFADcatchperfishingseasonrepresented27000tofthetotalaveragecatchof40000tintheSSA(1991-1997)Fig2.Monthlymeanpurse-seinecatchesintheSouth

Sherbroarea(bars)andproportionofFAD-associatedcatches

(line).Results第18頁，共29頁。Fig3.Sizedistributionofcatchesofskipjackandofyellowfinandbigeyetunasin76FAD-associatedsets(FL:forklength,in2-cmclasses).Skipjack(71%)wasthemaintargetfollowedbybigeye

(15%)andyellowfin(14%).Results第19頁，共29頁。Meetingpoint:TunacanmakeuseoffloatingobjectstoincreasetheencounterFADsmayprovideadditionalmeetingpointsthatassistinschoolingandspawning).Forcenturies,menhavenoticedthatfishtendtogatheraroundobjectsfloatingonthesurfaceoftheocean,suchaslogs,debris,etc.sets(84%).圍網(wǎng)使用漂浮物捕撈鮪類，其非目標(biāo)魚的比例增加a)FADsincreasetheefficiencyofpurseseineeffortfortunaincludingskipjack.FADsmayprovideadditionalmeetingpointsthatassistinschoolingandspawning).Concentrationoffoodsupply:Afloatingobjectoraseamountaggregatespreyinsharksorturtles),remainsunknown.d)ThedeploymentofFADshascompoundedthedifficultiesofassessingCPUEtrendsforpurseseinefisheriesandhenceundertakingstockassessmentforskipjack,bigeyeandyellowfintuna.ImpactsonfisheriesFADshasbecomewidespreadandthisoffshoreareahasdevelopedandmayformfreeswimminglooseschoolsduringthedayto

2.Discardandby-catchstatus

(a)Thespeciescompositionoftunadiscards(total67t)estimatedfrom18setsshowedthatskipjack,frigate,bigeye,yellowfin,andlittletunarepresented44%,28%,12%,11%,and5%,respectively.Tunadiscardsconsistedmainlyofsmallfish(mode:38cm).

(b)By-catchesofotherpelagicspecies(Table1)wereassociatedwith64FADsets(84%).Results第20頁，共29頁。Results第21頁，共29頁。Fig4.Proportionsofcatchesanddiscardsofmajorandminortunaspeciesandofassociatedfauna.Results第22頁，共29頁。

3.TunasassociatedwithFADsbasedonstomachcontentdataTable2.Numberofstomachsinvestigated(N;e:empty;non-e:non-empty),minimum,maximum,andmeanliveweightofindividualssampled(Wt),andofstomachcontentliveweight(SCW)ofdifferentspeciesoftunaintheSSA.Stomach-contentanalysiswascarriedoutfor572

tunassampled,including87withnon-zerostomach

contentweights

Results第23頁，共29頁。nimbaria,Toestimatetheby-catchusingscientificobserverdatacollectedduring1998.大目鮪幼魚隨漂浮物洄游，造成多種漁法可捕獲大目鮪幼魚TogiveanoverviewoftheFADtunapurse-seinefisheryintheSSA.TunadiscardsconsistedmainlyFADsmayprovideadditionalmeetingpointsthatassistinschoolingandspawning).FADsmayprovideadditionalmeetingpointsthatassistinschoolingandspawning).圍網(wǎng)使用人工聚集器對於小型鮪類的開發(fā)及在熱帶東大西洋攝食食性之研究Reporter:謝佳樺圍網(wǎng)使用漂浮物捕撈鮪類，其非目標(biāo)魚的比例增加FADshasbecomewidespreadandthisoffshoreareahasdevelopedb)Thespeciescompositionofpurseseinesetsonfloatingobjects(includingFADs)isdifferenttothoseonunassociatedtunaschools.Sizedistributionofcatchesofskipjackandofyellowfinandbigeyetunasin76FAD-associatedsets(FL:forklength,in2-cmclasses).TunasassociatedwithFADsbasedonstomachcontentdataSizedistributionofcatchesofskipjackandofyellowfinandbigeyetunasin76FAD-associatedsets(FL:forklength,in2-cmclasses).

Fig5.Preycompositionofstomachcontentsinweightpercentageforskipjack(SKJ),bigeye(BET),yellowfin(YFT;twosizeclasses)sampledfromFADassociatedcatches.Results第24頁，共29頁。DiscussionandConclusions第25頁，共29頁。Fig6.VariationinmeanweightofskipjackinFAD-associatedcatches(for1979–1990,meansaregivenforOctober–JanuaryandFebruary–April;for1991–1997,quarterly