?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Stock+assessment+of+the+Queensland+east+coast+common+coral+trout+(Plectropomus+leopardus)+fishery&rft.creator=Leigh%2C+G.M.&rft.creator=Campbell%2C+A.B.&rft.creator=Lunow%2C+Chad+P.&rft.creator=O'Neill%2C+M.F.&rft.subject=Fishery+research&rft.subject=Fishery+resources&rft.subject=Fishery+for+individual+species&rft.subject=Great+Barrier+Reef&rft.subject=Fishery+management.+Fishery+policy&rft.description=Common+coral+trout+Plectropomus+leopardus+is+an+iconic+fish+of+the+Great+Barrier+Reef+(GBR)+and+is+the+most+important+fish+for+the+commercial+fishery+there.+Most+of+the+catch+is+exported+live+to+Asia.%0D%0AThis+stock+assessment+was+undertaken+in+response+to+falls+in+catch+sizes+and+catch+rates+in+recent+years%2C+in+order+to+gauge+the+status+of+the+stock.+It+is+the+first+stock+assessment+ever+conducted+of+coral+trout+on+the+GBR%2C+and+brings+together+a+multitude+of+different+data+sources+for+the+first+time.%0D%0AThe+GBR+is+very+large+and+was+divided+into+a+regional+structure+based+on+the+Bioregions+defined+by+expert+committees+appointed+by+the+Great+Barrier+Reef+Marine+Park+Authority+(GBRMPA)+as+part+of+the+2004+rezoning+of+the+GBR.+The+regional+structure+consists+of+six+Regions%2C+from+the+Far+Northern+Region+in+the+north+to+the+Swains+and+Capricorn%E2%80%93Bunker+Regions+in+the+south.+Regions+also+closely+follow+the+boundaries+between+Bioregions.+Two+of+the+northern+Regions+are+split+into+Subregions+on+the+basis+of+potential+changes+in+fishing+intensity+between+the+Subregions%3B+there+are+nine+Subregions+altogether%2C+which+include+four+Regions+that+are+not+split.+Bioregions+are+split+into+Subbioregions+along+the+Subregion+boundaries.+Finally%2C+each+Subbioregion+is+split+into+a+%E2%80%9Cblue%E2%80%9D+population+which+is+open+to+fishing+and+a+%E2%80%9Cgreen%E2%80%9D+population+which+is+closed+to+fishing.%0D%0AThe+fishery+is+unusual+in+that+catch+rates+as+an+indicator+of+abundance+of+coral+trout+are+heavily+influenced+by+tropical+cyclones.+After+a+major+cyclone%2C+catch+rates+fall+for+two+to+three+years%2C+and+rebound+after+that.+This+effect+is+well+correlated+with+the+times+of+occurrence+of+cyclones%2C+and+usually+occurs+in+the+same+month+that+the+cyclone+strikes.+However%2C+statistical+analyses+correlating+catch+rates+with+cyclone+wind+energy+did+not+provide+significantly+different+catch+rate+trends.+Alternative+indicators+of+cyclone+strength+may+explain+more+of+the+catch+rate+decline%2C+and+future+work+should+investigate+this.%0D%0AAnother+feature+of+catch+rates+is+the+phenomenon+of+social+learning+in+coral+trout+populations%2C+whereby+when+a+population+of+coral+trout+is+fished%2C+individuals+quickly+learn+not+to+take+bait.+Then+the+catch+rate+falls+sharply+even+when+the+population+size+is+still+high.+The+social+learning+may+take+place+by+fish+directly+observing+their+fellows+being+hooked%2C+or+perhaps+heeding+a+chemo-sensory+cue+emitted+by+fish+that+are+hooked.+As+part+of+the+assessment%2C+analysis+of+data+from+replenishment+closures+of+Boult+Reef+in+the+Capricorn%E2%80%93Bunker+Region+(closed+1983%E2%80%9386)+and+Bramble+Reef+in+the+Townsville+Subregion+(closed+1992%E2%80%9395)+estimated+a+strong+social+learning+effect.%0D%0AA+major+data+source+for+the+stock+assessment+was+the+large+collection+of+underwater+visual+survey+(UVS)+data+collected+by+divers+who+counted+the+coral+trout+that+they+sighted.+This+allowed+estimation+of+the+density+of+coral+trout+in+the+different+Bioregions+(expressed+as+a+number+of+fish+per+hectare).+Combined+with+mapping+data+of+all+the+3000+or+so+reefs+making+up+the+GBR%2C+the+UVS+results+provided+direct+estimates+of+the+population+size+in+each+Subbioregion.%0D%0AA+regional+population+dynamic+model+was+developed+to+account+for+the+intricacies+of+coral+trout+population+dynamics+and+catch+rates.+Because+the+statistical+analysis+of+catch+rates+did+not+attribute+much+of+the+decline+to+tropical+cyclones%2C+(and+thereby+implied+%E2%80%9Creal%E2%80%9D+declines+in+biomass)%2C+and+because+in+contrast+the+UVS+data+indicate+relatively+stable+population+sizes%2C+model+outputs+were+unduly+influenced+by+the+unlikely+hypothesis+that+falling+catch+rates+are+real.+The+alternative+hypothesis+that+UVS+data+are+closer+to+the+mark+and+declining+catch+rates+are+an+artefact+of+spurious+(e.g.%2C+cyclone+impact)+effects+is+much+more+probable.+%0D%0AJudging+by+the+population+size+estimates+provided+by+the+UVS+data%2C+there+is+no+biological+problem+with+the+status+of+coral+trout+stocks.+The+estimate+of+the+total+number+of+Plectropomus+leopardus+on+blue+zones+on+the+GBR+in+the+mid-1980s+(the+time+of+the+major+UVS+series)+was+5.34+million+legal-sized+fish%2C+or+about+8400+t+exploitable+biomass%2C+with+an+2+additional+3350+t+in+green+zones+(using+the+current+zoning+which+was+introduced+on+1+July+2004).+For+the+offshore+regions+favoured+by+commercial+fishers%2C+the+figure+was+about+4.90+million+legal-sized+fish+in+blue+zones%2C+or+about+7700+t+exploitable+biomass.+%0D%0AThere+is%2C+however%2C+an+economic+problem%2C+as+indicated+by+relatively+low+catch+rates+and+anecdotal+information+provided+by+commercial+fishers.+The+costs+of+fishing+the+GBR+by+hook+and+line+(the+only+method+compatible+with+the+GBR%E2%80%99s+high+conservation+status)+are+high%2C+and+commercial+fishers+are+unable+to+operate+profitably+when+catch+rates+are+depressed+(e.g.%2C+from+a+tropical+cyclone).+The+economic+problem+is+compounded+by+the+effect+of+social+learning+in+coral+trout%2C+whereby+catch+rates+fall+rapidly+if+fishers+keep+returning+to+the+same+fishing+locations.+In+response%2C+commercial+fishers+tend+to+spread+out+over+the+GBR%2C+including+the+Far+Northern+and+Swains+Regions+which+are+far+from+port+and+incur+higher+travel+costs.%0D%0AThe+economic+problem+provides+some+logic+to+a+reduction+in+the+TACC.+Such+a+reduction+during+good+times%2C+such+as+when+the+fishery+is+rebounding+after+a+major+tropical+cyclone%2C+could+provide+a+net+benefit+to+the+fishery%2C+as+it+would+provide+a+margin+of+stock+safety+and+make+the+fishery+more+economically+robust+by+providing+higher+catch+rates+during+subsequent+periods+of+depressed+catches.+During+hard+times+when+catch+rates+are+low+(e.g.%2C+shortly+after+a+major+tropical+cyclone)%2C+a+change+to+the+TACC+would+have+little+effect+as+even+a+reduced+TACC+would+not+come+close+to+being+filled.+Quota+adjustments+based+on+catch+rates+should+take+account+of+long-term+trends+in+order+to+mitigate+variability+and+cyclone+effects+in+data.&rft.publisher=Queensland+Department+of+Agriculture%2C+Fisheries+and+Forestry&rft.date=2014&rft.type=Monograph&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.relation=http%3A%2F%2Fera.daf.qld.gov.au%2Fid%2Feprint%2F4547%2F1%2FCoralTroutStockAssessment2014.pdf&rft.identifier=+++Leigh%2C+G.M.%2C+Campbell%2C+A.B.%2C+Lunow%2C+C.+P.+and+O'Neill%2C+M.F.++(2014)+Stock+assessment+of+the+Queensland+east+coast+common+coral+trout+(Plectropomus+leopardus)+fishery.+%3Chttp%3A%2F%2Fera.daf.qld.gov.au%2Fid%2Feprint%2F4547%2F%3E++Technical+Report.+Queensland+Department+of+Agriculture%2C+Fisheries+and+Forestry.++++++&rft.identifier=http%3A%2F%2Fera.daf.qld.gov.au%2Fid%2Feprint%2F4547%2F&rft.relation=http%3A%2F%2Fera.daf.qld.gov.au%2Fid%2Feprint%2F4547%2F