COMMUNICATION EfficacyofaShort-TermCaptiveBroodstockProgramComparedwith Hatchery-OriginSpringChinookSalmonDerivedfromtheSame Population MichaelP.Gallinat,*JosephD.Bumgarner,andLanceA.Ross WashingtonDepartmentofFishandWildlife,600CapitolWayNorth,Olympia,Washington98501,USA Abstract Weexaminedtheefficacyofaone-generation(fivebroodyears: 1997 2001)captivebroodstockprogramforspringChinookSalmon Oncorhynchustshawytscha bycomparingsurvivalratesof captivebroodstockprogeny(CBP;F2)withthatofhatchery-origin fish(HOR)fromaconservationhatcherysupplementationprograminwhichbothgroupswerederivedfromtheTucannonRiver (WashingtonState)populationforthe2000 2006broodyears. Survivalratescomparedwereeggtofry,frytosmolt,eggto smolt,total(ages3 5)andadult(ages4+)smolt-to-adult-return (SAR)survival,andtotal(ages3 5)andadult(ages4+)progenyto-parent(P:P)ratio.TotalescapementandadultP:Pratioswere alsoexaminedtodetermineifobserveddemographicbenefitsto thepopulationcontinuedafterthecaptivebroodstockprogram ended.TheCBPgrouphadlowerwithin-hatcherysurvivalthan theHORgroup,withsignificantdifferencesinsurvivalattheeggto-fryandegg-to-smoltstagesduetopooreggviability.Mean untransformedtotalandadultSARsfortheCBPwerehalfthose oftheHORgroup;however,SARsdidnotdiffersignificantly. TheCBPalsohadsignificantlylowertotalandadultP:Pratios thantheHORgroupandwerebelowreplacementforsixofthe sevenbroodyears.Whilethecaptivebroodstockprovidedadditional fishforreleasethatwouldnothavebeenavailableotherwise, overalltheCBPperformedpoorlyandbelowexpectationscomparedwiththeHORgroup,bothwithinthehatcheryandafter release.Thecaptivebroodstockprogramprovidedashort-term demographicboost,mostnotableinthe2008 2010returnyears, butthebenefitdidnotcarryoveraftertheprogramended. AlongthewestcoastofNorthAmerica,conservationorientedhatcheryprogramsareusedintheattemptto increasepopulationnumbersofthreatenedandendangeredPaci ficsalmon Oncorhynchus spp.andsteelhead O. mykiss (Brannonetal. 2004;Waplesetal. 2007).Thegoal ofthesehatcheryprogramsistoenhancenatural productionwhileminimizingthegeneticandecological impactstowildpopulations(Fischetal. 2015). Conservation-orientedhatcherysupplementationprograms(hereafter “supplementationprograms”)typically spawnbroodstockcollectedfromthenaturalenvironment thatcanbecomprisedofbothnaturalandhatchery-origin fish.Afteraspeci fiedperiodofhatcheryrearing,juveniles arereleasedintothenaturalenvironment.Thesetypesof programsaredesignedtoproduce fishthat,oncereintroducedbackintothewild,becomenaturallyspawning fish (Trushenskietal. 2010).Incontrast,captivebroodstock programsarebeingusedingenerescueprograms,where fisharekeptincaptivitythroughouttheirlife(fromeggto spawningadults)tooffsetmortalitythatoccursinthenaturalenvironmentandrapidlyincreasethenumberof availablegametes.Captivebroodstockprogramsare becomingimportantcomponentsofconservationefforts topreventtheextinctionofendangeredandthreatened species(Fraser 2008;WilliamsandHoffman 2009). Bothsupplementationandcaptivebroodstockprogramsutilizetheprotectionofthehatcheryenvironment toincreasesurvivalandpotentiallyprovideademographic boosttopopulationnumbersuntilfactorscontributingto thepopulationdeclinecanbeaddressed(Frankham 2008). However,theuseofanadromousPaci ficsalmoninboth supplementationandcaptivebroodstockprogramsis regardedasexperimentalinnatureandhashadmixed resultsasaconservationmeasureintherecoveryand restorationoflistedpopulations(Rinneetal. 1986;Flagg andMahnken 1995;Fraser 2008). Areductioninperformance(e.g.,relativereproductive success,survival,spawningbehavior)isoftenreportedfor *Correspondingauthor:michael.gallinat@dfw.wa.gov ReceivedMarch28,2022;acceptedJune16,2022 NorthAmericanJournalofAquaculture © 2022AmericanFisheriesSociety. ISSN:1522-2055print/1548-8454online DOI:10.1002/naaq.10259 1
hatchery-origin fi shrelativetotheirnatural-origincounterparts(LynchandO'Hely 2001;Ford 2002)andisthought tohavebothgenomic(Hindaretal. 1991;Waples 1991; Arakietal. 2007, 2009)andnongenomicorigins(Krueger andMay 1991;Kostow 2009).Aconcernforbothsupplementationandcaptivebroodstockprogramsisthat fishin thehatcheryundergorelaxednaturalandsexualselection pressuresrelativetoindividualsinthewildandselection fortraitsthatcarryhigh fi tnessincaptivity,butlow fitness inthewild,canoccur(Waples 1991;Ford 2002;Arakiet al. 2007;Frankham 2008).Similarly,differingenvironmentalornutritionalsignalsprovidedtodevelopinghatcheryandnatural-origin fishcanresultindifferencesthathave nongenomicorigins.Forexample,GallinatandChang (2013)foundsigni ficantlylowerreproductivepotentialin captivebroodandsupplementation-rearedfemalescomparedwithnatural-originfemalesofthesamestock,with fecunditydecreasingastimespentinthehatcheryenvironmentincreased.Starketal.(2018)alsofoundsigni ficantly lowereggviabilityandegg-to-frysurvivalfromcaptiverearedsalmonidscomparedwithnatural-originsalmonids spawningintheEastForkSalmonRiver.Manyofthe biologicalchangesthatcanoccurastheresultofcaptivity areunknown(Horreoetal. 2017),butreducingthenumberofgenerationsincaptivityisexpectedtoreducethe extentordegreeofdomesticationselection(Frankham 2008;Horreoetal. 2017). Inthemid-1970s,theLowerSnakeRiverCompensationProgramwasenactedundertheWaterResources DevelopmentActof 1976 (Section102)toprovidemitigationfromtheexpectedlossesofPacifi csalmonandsteelheadcausedbythefourlowerSnakeRiverdams (USACE 1975).Asaresult,10hatcheriesand12hatchery satellitefacilitieswereconstructedand/ormodifi edtomitigateforlossesthroughouttheSnakeRiverbasin(Herrig 1990).InthestateofWashington,LyonsFerryHatchery wasconstructedandTucannonFishHatcherywasmodifiedtorearPacificsalmonandsteelheadfortheLower SnakeRiverCompensationProgram.ForTucannonRiver springChinookSalmon Oncorhynchustshawytscha,an annualreleaseof132,000smoltswasexpectedtoreturn 1,152adultsonaverage(USACE 1975). TheTucannonRiverspringChinookSalmonhatchery programbeganin1985bycollectingwild-originadultsfor broodstock,andby1989,bothwildandhatchery-origin fishwerecollectedforbroodstock.Totaladultreturns (wildandhatchery)from1985to1991wereestimated between300and600 fish(Bugertetal. 1992).Whilethe overallreturnswerestable,returnsofhatcheryadultswere fewerthanoriginallyanticipatedusingtheoriginalsurvivalassumptions(age4andolder[age4+]smolt-toadult-return[SAR]survivalrateof0.87%).Monitoring duringthisperiodalsodeterminedthatthenaturalpopulationproducedadultsatlevelsbelowreplacement(~0.8 returns/spawner),whilethesupplementationprogram progeny-to-parent(P:P)ratiowasabout1.9andappeared tobeprovidinganoverallbenefi teventhoughitwasoperatingbeloworiginalsurvivalassumptions.PriortoenactinganysportortribalspringChinookSalmon fi sheriesin theTucannonRiver,theNationalMarineFisheriesServicelistedSnakeRiverspring/summerChinookSalmonas “threatened ” undertheFederalEndangeredSpeciesAct duetodepressedand/ordecliningreturnstotheSnake Riverbasin(NMFS 1992).DuetotheEndangeredSpecies Actlistingandbecausethehatcheryprogramwasoriginallyinitiatedwithwild-origin fish,theTucannonRiver springChinookSalmonhatcheryprogramwastransitionedfromaharvestmitigationprogramtoanintegrated conservationsupplementationprogramtoassistinthe preservationandrebuildingofthenaturalpopulation, designedwithmatingandweirortrapmanagementprotocolsthatallowforgene fl owbetweenthehatchery-origin andnatural-origincomponentsinthehatcheryandonthe spawninggrounds. In1994,totalTucannonRiverspringChinookSalmon returnswereestimatedat140 fishanddeclinedto54 fish in1995(Bumgarneretal. 1996).Theseconsecutiveyears oflowreturnspromptedtheWashingtonDepartmentof FishandWildlife(WDFW)toinitiateacaptivebroodstockprogramwith1994broodyear(BY)juvenileson handatLyonsFerryHatchery.Thiseffortwassuspended followingpredictionsthatreturnsin1996and1997would besimilartopre-1994levels.Theimprovedreturnsprojectedfor1996and1997didnotmaterialize,and floodsin theTucannonRiverbasinduringbothyearseliminated mostofthenaturalproduction.Moreover,an80%lossof the1997BYhatcheryeggtakeoccurredbecauseofamalfunctionofawaterchilleratthehatchery.Duetocontinuedlowreturns,lossestobothnaturalandhatchery production,andthefactthatthenaturalpopulation remainedbelowthereplacementlevel,thecaptivebroodstockprogramwasreinitiatedwithBY1997 fishonhand atLyonsFerryHatchery.However,duetotherisks involved(e.g.,geneticdivergence,domestication,potential catastrophiclossinthehatchery),itwasagreedthatthe captivebroodstockprogramwouldonlybeimplemented foronegeneration(i.e., fiveBYstotal:1997 2001;Gallinatetal. 2009).Theproductiongoalforthecaptive broodstockprogramwas150,000smoltsannually.Atthis levelofsmoltproduction,300adult fish/yearwouldreturn ifananticipatedSARsurvivalrateof0.2%wereachieved. Inaggregate,thereturningadultsfromthecaptivebrood andsupplementationprogramscouldthenbeexpectedto return600 700 fishannuallybetween2005and2010,similartototalpre-1994returns. Performancecharacteristics(fecundity,growthorsize, spawntiming,survival,etc.)ofhatchery fishderivedfrom differenttypesofprograms(e.g.,conservation 2 GALLINATETAL.
supplementationversuscaptivebroodstock)areimportantinevaluatingtheefficacyofdifferentpracticesin meetingtheiroverallobjectives.Successofcaptive broodstockprogramshaslargelybeenmeasuredbythe numberofeggs,fry,andadultsproducedincaptivity, ratherthantheperformanceofthe fishafterrelease (ISRP 2004).Studiesalsoconductedonpopulationsthat haveacommongeneticbackgroundprovideachanceto understandthemechanismsbehindchangescausedby thehatcheryenvironment(GallinatandChang 2013). Fecundity,eggsize,spawningtiming,andlengthatage ofthecaptivebroodstockforthispopulationhavebeen publishedelsewhere(Gallinatetal. 2009;Gallinatand Chang 2013).ProgenyfromthecaptivebroodstockprogramrearedinparallelwiththesupplementationprogramattheLyonsFerryHatcherycomplexofferedthe opportunitytocomparethein-hatcheryandpostrelease performanceofthesetwostrategies.Ourcomparisons (egg-to-fry,fry-to-smolt,andegg-to-smoltsurvival)offer insightintohatcheryperformanceandperformancefollowingrelease(total[ages3 5]andadult[age4+]SAR survivalandP:Pratioandtotalescapementbacktothe TucannonRiver)andallowforcharacterizationofthe contributionsofthesetwostrategiestothedemographic benefi ttothepopulation. METHODS Groupdefinitions. Wede finedthestudygroupsasfollows:(1)hatchery-origin(HOR) fi shusedforthesupplementationprogramweretheproductofarti ficial reproductionofbothnatural-origin(NOR)andHOR fish butwerereleasedintothenaturalenvironmentafter18 monthsofhatcheryrearingasyearlingsmolts(Figure 1), and(2)captivebroodstockprogeny(CBP)aretheprogeny (F2)fromcaptivebroodstockfemales(F1)thatwere crossedwithNOR,HOR,orothercaptivebroodstock males(F1)andtheCBPwerereleasedafter18monthsof hatcheryrearingasyearlingsmolts(Figure 1). Studyarea. TheTucannonRiverisathird-order streaminsoutheasternWashingtonStateand fl owsinto theSnakeRiverbetweenLittleGooseandLowerMonumentaldamsapproximately622kmfromthemouthof theColumbiaRiver(Figure 2).Streamelevationrises from150matthemouthoftheTucannonRiverto1,640 mattheheadwater(Bugertetal. 1991).Thetotalwatershedareaisabout1,295km2 (Gallinatetal. 2009).Mature NORandHORspringChinookSalmonadultsmigrateto theTucannonRiverbasinfromApriltoJuneandspawn fromlateAugustthroughSeptember.SpawningandjuvenilerearingofNOR fi shintheTucannonRivertypically occursupstreamofriverkilometer(rkm)35(measuring fromitscon fluencewiththeSnakeRiver)(Gallinatetal. 2008).ThemajorityofNORsmoltsemigratingoutofthe systemareabout18monthsold,haveameanforklength of105 113mm,andrearintheoceanfor1 3yearsuntil mature(GallinatandChang 2013). Hatcheryfacilities. ThreedifferentWDFWfacilities (LyonsFerryHatchery,TucannonFishHatchery,and CurlLakeAcclimationPond)contributedtotheproductionofHORandCBP fish.TheLyonsFerryHatcheryis locatedontheSnakeRiver(atrkm90,measuringfromit confl uencewiththeColumbiaRiver)atitscon fluencewith thePalouseRiver(Figure 2)andwasusedforbroodstock holdingandspawning,incubation,andearlylifestage rearinguntilproductionmarkingandtagging.TheTucannonFishHatcheryislocatedatrkm59ontheTucannon River(measuringfromitconfl uencewiththeSnakeRiver) andhasanadulttrapforbroodstockcollection(Figure 2). TheTucannonFishHatcherywasusedforintermediate overwinterjuvenilerearingofbothCBPandHOR fish priorto finalacclimationatCurlLakeAcclimationPond intheupperbasin(Figure 2).CurlLakeAcclimationPond isa0.85-hectarenatural-bottomlake(meandepth = 2.7m; FIGURE1.TucannonRiverspringChinookSalmongroupsusedforsurvivalcomparisons.Possiblespawningcrossesareshowninbrackets. Thespawningcrossesfor fishspawnedinthehatcheryarelistedinorderofpriority. COMMUNICATION 3
volume = 22,203m3)adjacenttotheTucannonRiverand locatedabout6kmupstreamofTucannonFishHatchery. Supplementationprogrambroodstock. Thesupplementationprogrambroodstockgoalwastocollectupto100 adultsattheTucannonFishHatcheryadulttrapfrom throughouttherun,comprisedofbothNORandHOR returns(target1:1ratio).TucannonRiverHOR fishused forbroodstockwereveri fiedbycodedwiretag(CWT) extractionatthetimeofspawning.AgesofNORandHOR femalesusedforspawningrangedfrom4to5yearsold, andagesofNORandHORmalesusedforspawningrangedfrom3to5yearsold.Jack(age-3)malespawningcontributionaveraged4.5%overthecourseofthestudy(range = 2.1 6.8%).Duringspawningforthesupplementationprogram,a2 × 2factorialfertilizationstrategywasincorporatedtoincreaseeffectivepopulationsizeandmaintain geneticdiversity(BusackandKnudsen 2007).Atfertilization,eggsfromtworipefemalesandsemenfromtwomales wereselectedbasedontheiroriginandavailabilitywithpriorityforHOR × NORcrosses(Figure 1).Theeggsfrom eachfemaleweresplitintoapproximatelytwoequalhalves, withonemaleaddedtoonehalfofeachfemale'seggsand theothermaletotheotherhalf.Afterabout30s,thehalves wererecombinedintosingleegglotsperfemale.Theeggs producedfromthespawningofthesupplementationbroodstockforthe2000 2006BYsaretheHORgroupusedfor comparisontotheCBPgroup. Originationofthecaptivebroodstock. Thecaptive broodstockpopulationwasselectedfromfryproduced fromthesupplementationprogramfromthe1997to2001 BYs(WDFWetal. 1999).Becausethecaptivebroodstock malesmaturedatanearlieragethanfemales,additional frywerecollectedfromthe2002BYtohaveenoughcaptivemalesavailableattheendofthecaptivebroodstock programtocrosswithcaptivefemales.Wechosetocollect fryfromthesupplementationprogramtolessentheeffects ofremovingmore fishfromthenaturalpopulationand becauseofpotentialdiseaseconcernsfrombringing fishin fromtheriver.Bacterialkidneydiseasescreeningusing enzyme-linkedimmunosorbentassayofkidneytissuefrom allfemaleswasperformed(Munsonetal. 2010),andprogenyfromthelowestopticaldensitycategorieswereused forthecaptivebroodstockasbacterialkidneydiseasehas beenalargesourceofmortalityinothercaptivebroodstockprograms(FlaggandMahnken 1995).Priorityoffry selectionforthecaptivebroodstock(inthefollowing order)wasgiventoNOR × NOR,NOR × HOR,and HOR × HORmatingsfromthesupplementationprogram. FIGURE2.LocationoftheTucannonRiverbasin,atributaryoftheSnakeRiver,andlocationsofLyonsFerryHatchery,TucannonHatchery,and CurlLakeAcclimationPond. 4 GALLINATETAL.
TheproportionofNOR fi shusedforestablishingthecaptivebroodstockaveraged39%overtheprogram'shistory (range = 5.9 53.9%). Thefertilizationstrategyemployedledtoprogenythat werehalf-siblingsfrompairsoffemales.Allmatingsthat weresiredbythesamemaleswereconsideredonefamily unittoavoidwithin-familymatingsinthefuture.Asa result,whileonly15familyunitswerechosenforthecaptivebroodstockprogram,actualcontributionsofmaleand femaleparents(populationsize)tothecaptivebroodprogramonayearlybasiswashigher.Theeffectivepopulationsizesofcaptivebroodstockforthe1997 2002BYs were53,58,42,56,58,and59,respectively,andgenerally exceededthegoalof50 fishsuggestedbyAllendorfand Ryman(1987)andVerspoor(1988)tolimittheloss(<1%) ofgeneticvariabilityinmostsalmonidspecies. Eightyfryfromeachofthe15familyunitswere selected(1,200total fi sh)fromeachBY.Rearingvessels atLyonsFerryHatcheryincluded151.2-m-diameter(0.5m-deep)circulartanksforrearingjuvenilecaptivebroodstockandeight6.1-m-diameter(1.1-m-deep)circulartanks forrearingthecaptivebroodstockadults.Boththe1.2and6.1-mcircularrearingtankswerecoveredwithcamoufl agenettingtoprovideshade,lessenstress,andprevent jumpingoutoftanks.The1.2-mcircular fiberglasstanks heldfamilyunitsindividuallybeforetheywerelarge enoughtomark.Fishweretaggedafter1year,andfamily unitswerereducedto30 fi sh/family(450 fish/BY)byrandomselectionatthistime.Familyunitsforthecaptive broodprogramweredouble-tagged(inbothadipose fin andsnout)withuniquelycodedCWTsandwithaunique alphanumericvisualimplanttaginsertedbehindtheeye. Thesestepsprovidedthenecessarymarkstoverifythat membersofthesamefamilyunitwerenotmatedtogether. AfterCWTandvisualimplanttagging,all fi shfroman individualBYweretransferredtoasingle6.1-mcircular fiberglasstankforrearingtomaturity.Hatcherystaffvisuallyestimatedsizeandgrowthtoprescribefeedingrates tominimizestressorstosamplingandhandlingthatmight jeopardize fi shhealth.Size-at-agegoalsweresetasfollows:age1 = 20 25g,age2 = 150 200g,age3 = 900g, andage4 = 4,000g. DuringlateJunetoearlyJuly,captivebroodstockthat wereage2orolderwereexaminedforsignsofsexual maturation.Maturationwasdeterminedbyadarkeningin bodycolorationasothermorphologicalcharacteristics indicatingsexualmaturationwerenotreadilyapparent. Maturefemalecaptivebroodstockwereinjectedwitherythromycin(Erythro-200;AbbottLaboratories,Abbott Park,Illinois)at20mgperkilogramofbodyweightat sortingtopreventbacterialkidneydisease.Maturecaptive broodstockweretransportedtoholdingraceways(3.1m × 1.8m × 24.4m)atLyonsFerryHatcheryincommonwith, butseparatedbyscreensfrom,thesupplementation broodstock(NORandHOR)collectedfromtheTucannonRiver.Broodstockfrombothprogramsweretreated withaformalin flush(167ppm)everyotherdaytocontrol fungus(Saprolegnia sp.). Duringspawning,captivebroodstockandHORand NORadultswereanesthetizedwithanunbufferedsolution (45 50mg/L)oftricanemethanesulfonate(WesternChemical,Ferndale,Washinton)andexaminedweeklyforripeness(lateAugusttoearlyOctober).Althoughpeakspawn timingwasabout2weekslaterforthecaptivebroodstock thanfor fi shcollectedfromtheriver(Gallinatetal. 2009), wewerestillabletospawnsomecaptivebroodstock femaleswithNORandHORmaleseachyear.Finalcontributionofmalescrossedwithcaptivebroodstockfemales was72%captivebroodstockmales,19%NORmales,and 9%HORmales.Spawningadultsfromthecaptivebroodstockwereyoungerthanthosefromthesupplementation program,withfemalesbeginningtomatureatage3and malesstartingtomatureatage2.Spawningadultsless thanage4(minijacks,jacks,jills)comprised34.1%ofthe spawningadultsonaveragefromthecaptivebroodstock program(range = 0.0 66.7%).Forboththesupplementationandcaptivebroodstockprograms,ripefemaleswere killedandtheeggsexcisedandcollectedintonumbered plasticbucketsandplacedincoolersonaninsulatedlayer ofice.Miltfrommaleswascollectedintonumberedplasticbags,oxygenated,andstoredonaninsulatedlayerof iceuntilusedforfertilization.Fertilizationofthecaptive broodstockfollowedthesame2 × 2factorialmatrix describedearlierforthesupplementationbroodstock.Fertilizedeggswererecombined,onefemaleperbucket,and disinfectedinaniodophorbathatarateof100ppmfor1 h.Theeggsproducedfromthespawningofthecaptive broodstockforthe2000to2006BYsmakeuptheCBP groupusedforcomparisontotheHORgroup. TheCBPandHORgroups. Theeggsfrombothprogramswereincubatedineitherverticalstackedtrayincubatorsorisolationbucketsandtreatedeveryotherday withformalinat1,667ppm(37%formaldehyde)for15 minforfunguscontrol.Fryfrombothgroupswereplaced intoseparateoutsideraceways(3.1m × 30.5m × 1.1m)at LyonsFerryHatcheryinDecemberandfedthesame commercialfeed(Bio-Oregon,Longview,Washington).At LyonsFerryHatchery,theentirefacility(incubation,raceways,circulartanks,andadultholdingponds)issupplied withpathogen-free,constant-temperaturewellwater (11°C)throughouttheyear. TheCBPandHOR fishweretaggedwithunique CWTstoidentifygroupsatLyonsFerryHatcheryinmidSeptember,1yearfollowingspawning.TheHOR fishwere alsotaggedwithavisualimplantelastomer(VIE)tag (NorthwestMarineTechnology,ShawIsland,Washington)behindtherighteye.TheVIEtagallowedforexternalidentifi cationoftheHORgroupaftertheywere COMMUNICATION 5
combinedfor finalacclimationinCurlLakeAcclimation Pond.Moreimportantly,thiswasdonetoexcludeCBP adultsfrombeingcollectedforbroodstockinthefutureto preventfurtherpotentialhatcherydomesticationand potentialcrosseswithsiblings.Followingmarkingand taggingatLyonsFerryHatchery,juvenileswere transferredtoTucannonFishHatcherytorearineither 12.2-m-diametercircularponds(0.6mdeep)or4.6-m × 1.5-m × 35.1-mand3.1-m × 0.9-m × 24.4-mraceways.At TucannonFishHatchery,riverwaterisusedasthemain sourceforrearing,whichallowsforamorenaturalwinter temperatureprofi le.However,wellandspringwateris mixedwithriverwatertokeeptemperaturesabove4.4°C. Asubsampleof fishfromeachgroupwastaggedwithpassiveintegratedtransponder(PIT)tagsinJanuary.InmidFebruary,bothHORandCBPjuvenilesweretransferred toCurlLakeAcclimationPondforaminimumof4weeks ofacclimationbeforerelease.Duringacclimation, fi sh werefedbyatruck-mountedfeedblower.Observedmortalitieswerecollected,counted,andassignedtotheir respectivegroupbasedonpresenceorabsenceoftheVIE tagbyhatcherypersonnel.Predation(primarilyavian)is knowntooccurduringacclimation,butitisassumedthat predationisnotbiasedtowardsonegroupovertheother. WatertemperaturesinCurlLakeAcclimationPondduringacclimationrangedbetween4.4and12.8°C.Individual lengthsandweightswererecordedfromaminimumof 250 fi shfromeachgroupbeforethevolitionalrelease began.The fishcouldvolitionallyemigratefromthelake frommid-MarchtolateApril,afterwhichanyremaining fishwereforcedoutbydrainingthelakeinentirety.The size-at-releasegoalforbothprogramswas30g/fishforthe 2000 2004BYsand50g/fishforthe2005 2006BYs. MostBYsoftheHORandCBPgroupswerehealthy throughouttheirrearingatLyonsFerryHatcheryand TucannonFishHatcheryanduponrelease.Theonly exceptionwasthe2001BYinwhichbacterialkidneydiseasewasdiagnosedinboththeHORandCBPgroups. The fishweretreatedwitherythromycin-medicatedfeed andmortalitydeclinedfollowingtreatment. Dataanalysis. Werecordedthenumberofmalesand femalesthatwereusedduringspawningatthehatcheryto determinethenumberofspawners.Tocalculatefecundity forthecaptivebroodstockandHORindividualfemales, eggswerephysicallyshockedattheeyedeggstage,with thedeadeggscountedandremoved.Waterwasdrained fromtheremainingliveeggs,andarandomsampleof100 eggswascollectedandweighedfromeachfemale.The totalnumberofliveeggsforeachfemalewasestimated bydividingthetotalliveeggweightbytheeggsize(g/ egg).Theliveeggestimatewasthendecreasedby4%to compensateforwateradherencetotheeggs(WDFW SnakeRiverLab,unpublisheddata).Thetotalnumberof liveeggsestimatedanddeadeggscountedwerecombined toestimatetotalfecundity(eggs/female).Thenumberof CBPandHORfrythatwerepondedinDecembertoracewaysatLyonsFerryHatcherywascalculatedbyusing standardgravimetrichatcheryinventorytechniques(Piper etal. 1982). Forsurvivalcomparisons,weusedthenumberof smoltsreleasedfromCurlLakeAcclimationPond.Using thedatadescribedabove,wecalculatedegg-to-fry(numberoffrydividedbyfecundity × 100),fry-to-smolt(numberofsmoltsreleaseddividedbythenumberoffry × 100), andegg-to-smolt(numberofsmoltsreleaseddividedby fecundity × 100)survivalrates. AdultreturnstotheTucannonRiverwerederivedfroma combinationofreddcounts,adulttrapping,spawning groundcarcassrecoveries,sexratios,andprespawnmortalityestimates(Gallinatetal. 2008).DatacollectedfromcarcassesincludedscalesamplesandnotingthepresenceofVIE tagsor finclips,andallsnoutswereremovedfromcarcasses forCWTextractionandorigindetermination.Acetate impressionsweremadefromscalesamplesandagedby experiencedpersonnelattheWDFWScaleAgeLab(Olympia,Washington).Noreturning fishlessthanage3or greaterthanage5wererecoveredfromtheTucannonRiver. EstimatesofSARsurvivalwerederivedbydividingthe numberoftotal(ages3 5)andadult(ages4+)returnsbythe numberofsmoltsreleased,calculatedasapercent,andused tocompareperformancebetweentheHORandCBP groups.WecalculatedBY-speci fictotal(ages3 5)andadult (ages4+)P:Pratiosasanindicatorofpopulationgrowth rate(adultreturnsdividedbythenumberofspawners). Allsurvivalestimateswerearcsinesquareroottransformedsincepercentagesformabinomial,ratherthana normal,distribution(Zar 1996).Aftertransformation, StatgraphicsPlus5.0software(Manugistics,Rockville, Maryland)wasusedforallstatisticalanalyses.Dueto highvarianceamongyears,anonparametricMann Whitney(Wilcoxon)rank-sumtestwasusedtocomparemedians.Thenullhypothesiswasthatbothmedianswere equalversusthealternatehypothesisthatthemedians werenotequal.Allstatisticaltestswereperformedatthe 95%con fidencelevel. RESULTS Thenumberofeggs,fry,andsmoltsandtheirsizeat releasefromCurlLakeAcclimationPondfortheCBP andHORgroupsbyBYisshowninTable 1.Theincrease insizeatreleaseforthe2005and2006BYsreflectsa managementchangeintheattempttoincreasesurvival andreturns.SurvivalestimatesfromtheCBPandHOR fishusedforin-hatcheryandpostreleasecomparativeanalysesareprovidedinTable 2 andshowthatthenumberof returningadultsfromthe2005and2006BYsincreased greatlyforbothgroups. 6 GALLINATETAL.
Forwithin-hatcheryjuvenilelifestagesurvivals(eggto fry,frytosmolt,eggtosmolt),wefounddifferences betweensomeofthecomparisons.Meanuntransformed egg-to-frysurvivalwas44%(SE = 5.5)forCBPand92% (SE = 0.9)fortheHORgroup(Table 2).Aftertransformation,theaveragerankforCBPegg-to-frysurvivalwas4.0 andtheaveragerankforHORegg-to-frysurvivalwas 11.0.The W-statisticwas49.0,andtheHORegg-to-fry survivalmediansweresigni ficantlygreaterthanthoseof theCBPgroup,witha P-valueof0.002(Figure 3). Meanuntransformedfry-to-smoltsurvivalwas86% (SE = 4.4)forCBPand78%(SE = 6.6)fortheHOR group(Table 2).TheaverageranksfortheCBPandHOR groupswere8.1and6.9,respectively,witha W-statisticof 20.0,whichwasnotsignifi cantlydifferent(P = 0.609;Figure 4). Egg-to-smoltcomparisonsalsofounddifferences betweentheCBPandHORgroups.Themeanuntransformedegg-to-smoltsurvivalfortheCBPgroupwas38% (SE = 4.2)andfortheHORgroupitwas72%(SE = 6.4) (Table 2).Aftertransformation,theaveragerankwas4.1 forCBPand10.9fortheHORgroup.The W-statistic was48.0,withasigni fi cant P-valueof0.003(Figure 5). Foradultlifestagesurvivals(SAR,P:P),weobserved differencesbetweensomeofthecomparisons.Mean untransformedtotalSARwas0.15%(SE = 0.09)forCBP and0.30%(SE = 0.13)fortheHOR fi sh(Table 2).However,nosigni ficantdifferences(W-statistic = 33.0, P = 0.304)inthemediantotalSARswerefound(Figure 6). ThemeanuntransformedadultSARwas0.10%(SE = 0.06)forCBPand0.21%(SE = 0.07)fortheHORgroup (Table 2).Nosigni ficantdifference(W-statistic = 38.0, P = 0.096)inthemedianadultSARswereevidentaftertransformation(Figure 6). ThemeanuntransformedtotalP:PratiofortheCBP groupwas0.73(SE = 0.47),anditwas3.79(SE = 1.65) fortheHORgroup(Table 2).TheHORgrouphadsignificantly(W-statistic = 40.5, P = 0.047)highermediantotal P:Pratiosaftertransformation(Figure 7).TheadultP:P ratiosoftheCBPwerebelowreplacementforsixofthe sevenBYs,whiletheHORgroupwasabovereplacement forsixofthesevenBYs(Table 2).ThemeanuntransformedadultP:PsurvivalfortheCBPgroupwas0.53 (SE = 0.36),anditwas2.56(SE = 0.94)fortheHOR group(Table 2).TheHORgrouphadsigni ficantly(W statistic = 44.0, P = 0.015)highermediansforadultP:P ratiosthantheCBPgroup(Figure 7). Aspreviouslystated,theTucannonRiverexperienced lowreturns(1994 1997;mean = 165total fi sh)priortothe startofthecaptivebroodstockprogram(Figure 8).As fish fromthecaptivebroodstockprogramwerebeginningto mature,returnstotheTucannonRiverincreasedin2001 and2002.However,runsdeclinedagainfrom2003to 2007,evenwiththeadditionofCBP fishreturningas adultsduringthelatterpartofthattimeperiod(Figure 8). Thepopulationthenexperiencedalargedemographic boostfromNOR,HOR,andCBPreturnsfrom2008to 2010(mean = 1,858total fi sh)buthasexperiencedaprecipitousdeclineinrecentyears(2016 2021;mean = 385 total fish;Figure 8). TABLE1.Datasummarybylifestage(eggs,fry,smolts)andthemeanweight(g)andmeanlength(FL;mm)withcoefficientofvariation(CV)of thesmoltsreleasedfromtheTucannonRiverspringChinookSalmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation(HOR)programsforthe2000 2006broodyears. Broodyear Total fecundity Number offry Smolts released Meansmolt weight(g) Meansmolt length(mm) Smolt lengthCV CBP 200014,5774,3233,05551163.510.8 2001281,303195,264140,39633135.317.2 2002176,54450,46244,78434135.015.1 2003309,416164,800130,06434135.017.3 2004310,819140,874132,31230132.913.3 2005261,84593,97190,05661166.314.3 2006162,73679,43278,17657158.518.8 HOR 2000128,980123,313102,09929133.113.2 2001184,127174,934146,92235139.416.3 2002169,364151,531123,58639141.715.6 2003140,658126,40071,15436138.816.2 2004140,459128,87767,54234139.510.1 2005161,345151,466149,46657162.013.5 200662,93457,19252,73554157.917.0 COMMUNICATION 7
Sincetheinceptionofthemonitoringprogramin1985, WDFWhasestimatedtheadultP:PratioofNORand HOR fishannually.Toillustratetheimportanceofthe HOR fi shtothepreservationoftheTucannonRiver springChinookpopulation,theNOR fishhaveonlybeen abovereplacementfor10(31%)of32years,whilethe HOR fi shhavebeenabovereplacementfor24(75%)of 32years.ThesurvivalperformanceoftheCBP fi shwas expectedtobesimilartotheHOR fishbutintheendwas onlyabovereplacementin1(14%)ofthe7years(Figure 9),whiletheHORandNOR fishwereabovereplacement in6(86%)and4(57%)ofthesame7years,respectively. TABLE2.Untransformedlifestagesurvivaldataforjuveniles(eggtofry,frytosmolt,eggtosmolt)andtotal(ages3 5)andadult(ages4+)agegroups(smolttoadultreturn[SAR]andprogenytoparent[P:P])fromtheTucannonRiverspringChinookSalmoncaptivebroodstockprogeny (CBP)andhatcherysupplementation(HOR)programsforthe2000 2006broodyears. Broodyear andmean Egg-to-fry survival(%) Fry-to-smolt survival(%) Egg-to-smolt survival(%) TotalSAR% (ages3 5) AdultSAR %(ages4+) TotalP:P (ages3 5) AdultP:P (ages4+) CBP 200029.770.721.00.000.000.000.00 200169.471.949.90.010.010.060.05 200228.688.725.40.000.000.010.01 200353.378.942.00.020.010.060.05 200445.393.942.60.060.060.230.23 200535.995.834.40.400.221.440.80 200648.898.448.00.540.423.312.58 Mean44.485.537.60.150.100.730.53 HOR 200095.682.879.20.150.132.151.79 200195.084.079.80.090.071.221.04 200289.581.673.00.100.091.301.24 200389.956.350.60.100.100.950.92 200491.852.448.10.180.151.361.16 200593.998.792.60.460.277.264.20 200690.992.283.81.030.6312.307.59 Mean92.478.372.40.300.213.792.56 FIGURE3.Notchedbox-and-whiskerplotofarcsinesquare-roottransformedegg-to-frysurvival(%)forTucannonRiverspringChinook Salmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation (HOR) fishfromthe2000to2006broodyears.Thelineinsidethebox representsthemedian,andtheboxextendsfromthelowerquartiletothe upperquartile,coveringthecenterhalfofeachsample.Thewhiskers extendfromtheboxtotheminimumandmaximumvaluesofeachsample.Thenotchdisplaystheconfidenceintervalaroundthemedian.Plots withdifferentlettersabovethemarestatisticallydifferentwith P < 0.05. FIGURE4.Notchedbox-and-whiskerplotofthearcsinesquare-roottransformedfry-to-smoltsurvival(%)forTucannonRiverspringChinookSalmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation(HOR) fishfromthe2000to2006broodyears.Thelineinside theboxrepresentsthemedian,andtheboxextendsfromthelowerquartiletotheupperquartile,coveringthecenterhalfofeachsample.The whiskersextendfromtheboxtotheminimumandmaximumvaluesof eachsample.Thenotchdisplaystheconfidenceintervalaroundthemedian.Plotswiththesameletterabovethemarenotstatisticallydifferent with P > 0.05. 8 GALLINATETAL.
femaleshadconsistentlylowereggsurvival.Initialoverall fertilizationrateofRed fishLakeSockeyeSalmon Oncorhynchusnerka captivebroodstockwasonly30%usingmilt fromanadromousmales,suggestingthatpooreggquality wastoblame(JohnsonandPravecek 1995). Kozfkayetal.(2017)sawimprovementinSalmon River,Idaho,ChinookSalmoncaptivebroodstockegg viabilitywithsaltwaterrearingandtheuseofchilled waterandnotedthatitcouldprovideimprovements FIGURE5.Notchedbox-and-whiskerplotofthearcsinesquare-roottransformedegg-to-smoltsurvival(%)forTucannonRiverspringChinookSalmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation(HOR) fishfromthe2000to2006broodyears.Thelineinside theboxrepresentsthemedian,andtheboxextendsfromthelowerquartiletotheupperquartile,coveringthecenterhalfofeachsample.The whiskersextendfromtheboxtotheminimumandmaximumvaluesof eachsample.Thenotchdisplaystheconfidenceintervalaroundthemedian.Plotswithdifferentlettersabovethemarestatisticallydifferentwith P < 0.05. FIGURE6.Notchedbox-and-whiskerplotsofthearcsinesquare-roottransformedtotal(ages3 5;toppanel)andadult(ages4+;bottompanel) smolt-to-adult-return(SAR)survival(%)forTucannonRiverspringChinookSalmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation(HOR) fishfromthe2000to2006broodyears.Thelineinside theboxrepresentsthemedian,andtheboxextendsfromthelowerquartiletotheupperquartile,coveringthecenterhalfofeachsample.The whiskersextendfromtheboxtotheminimumandmaximumvaluesof eachsample.Thenotchdisplaystheconfidenceintervalaroundthemedian.Plotswiththesameletterabovethemarenotstatisticallydifferent with P > 0.05. COMMUNICATION 9
survivalwasduetomaternalfactorsandthatmalegamete qualitydidnotappeartobeafactor.Gallinat(2006) foundthatspermmotilitywasnotasigni fi cantfactorin thehighereggmortalityoftheTucannonRiverSpring ChinookSalmoncaptivebroodstockprogram.Wealso excludedmalesasafactorinourstudysincewespawned HORandNORmaleswithHOR,NOR,andcaptive broodstockfemalesandonlythecaptivebroodstock
DISCUSSION Whilethecaptivebroodstockprogramwassuccessful inproducingadditionalsmoltsforrelease,theCBPperformedpoorlycomparedwiththeHORgroupfrom releasetoadultreturnsanddidnotmeettheadultreturn goalof300adults/yearuntilthesize-at-releasegoalwas increasedto50g/fishduringthelasttwoBYsoftheprogram.Thepoorperformancewassurprisinggiventhat bothgroupswererearedunderidenticalconditionsfor18 monthsbeforerelease,andjuvenilesappearedidenticalin physicalcharacteristics.Themajordifferencesbetweenthe twogroupswereasfollows:(1)theparents(allthe females,majorityofthemales)thatproducedtheCBP wereraisedentirelyincaptivity,(2)thecaptivebroodstock spawnerswereyoungerandsmallerinsizecomparedwith thesupplementationprogram fi sh,(3)spawntimingofthe captivebroodadultswaslater,althoughtheydidoverlap withHORandNORspawntiming(Gallinatetal. 2009), and(4)eggsurvivalofcaptivebroodstockfemaleswas signifi cantlylowerthanthatofNORandHORfemales (GallinatandChang 2013).Similartoourexperience, othercaptiveprogramsofPacificsalmonhavebeenplaguedwithhighmortalityrates,spawntimingoutsidethat of fishcollectedfromtheirnatalriver(bothHORand NOR),precociousmaturationofmales,loweggviability, andcaptiveadultsthataresmallerthanwild fish(Flagg andMahnken 1995;Schieweetal. 1997). Eggsurvivalhashistoricallybeenlowforcaptive broodstockprograms,typicallyrangingfrom30%to60% comparedwith >80%forwildfemales(FlaggandMahnken 1995).Vendittietal.(2013)suggestedthatpooregg
relativetomaturationsize,fecundity,andreproductive success.Incontrast,eggandfrylossweremuchhigherfor DungenessRiverChinookSalmoncaptivebroodstock rearedinsaltwaterpensversusthoserearedinfreshwater (Freymondetal. 2001).Theyhypothesizedthatthewarm waterconditionsofthenetpensinsummerwhentheova werematuringorthetimingofmovingthematuring fish tothehatcheryjustpriortospawningwastoblamefor thepoor-qualityeggs(Freymondetal. 2001).TheRed fish Lakecaptivebroodstockprogramattemptedseveral strategiestoimproveinitialSockeyeSalmonsurvivaland eggviabilityproblemsearlyintheprogram,including modi ficationofthestandardbrooddiet,incubatingeggs atdifferenttemperatures,andcontrollingmatingcrosses toexpandthegeneticbaseofthefewremaining fish (JohnsonandPravecek 1996).Themodifi cationstothe brooddietincludedreplacing50%ofthestandardprotein of fishmealwithAntarctickrill,increasingselenium(wateratthehatcherywasdeficientinselenium),andincreasinglevelsofvitaminsEandC(JohnsonandPravecek 1996).TheWhiteRiverspringChinookSalmoncaptive broodstockprogramusedhormoneinjectionstoincrease eggviabilityduetotheincompletematurationofovain thatprogram(Hillmanetal. 2021).Furtherexperimental researchwithunlistedChinookSalmoncaptivebroodstockpopulationswouldbebene ficialinidentifyingnutritional,hormonal,orotherfactorsassociatedwithpoor eggqualityandlowearlylifestagesurvival. Themainargumentagainstusingcaptivebroodstock orsupplementationprogramsisthatrearinginthehatcheryleadstodomesticationselection(Hindaretal. 1991; ReisenbichlerandRubin 1999).However,otherresearchersarguethatthesegeneticrisksareoverstatedandthat long-termeffectshavelittletonoempiricalbasis(Brannon FIGURE7.Notchedbox-and-whiskerplotsofthearcsinesquare-roottransformedtotal(ages3 5;toppanel)andadult(ages4+;bottompanel) progeny-to-parent(P:P)ratioforTucannonRiverspringChinookSalmoncaptivebroodstockprogeny(CBP)andhatcherysupplementation (HOR) fishfromthe2000to2006broodyears.Thelineinsidethebox representsthemedian,andtheboxextendsfromthelowerquartiletothe upperquartile,coveringthecenterhalfofeachsample.Thewhiskers extendfromtheboxtotheminimumandmaximumvaluesofeachsample.Thenotchdisplaystheconfidenceintervalaroundthemedian.Plots withdifferentlettersabovethemarestatisticallydifferentat P < 0.05. FIGURE8.TotalspringChinookSalmonescapementbacktotheTucannonRiverforcaptivebroodstockprogeny(CBP),hatcherysupplementation (HOR) fish,andnatural-origin(NOR) fishforthe1985 2021returnyears. 10 GALLINATETAL.
etal. 2004;Fraser 2008).Astudyonsteelheadpopulations supplementedwithhatchery-produced fishfromnative genotypesdetectednochangestoestimatesofeffective populationsize,geneticvariation,ortemporalgenetic structurewithinanypopulationnoralteredgeneticstructure(Gowetal. 2011).GeneticanalysisofTucannon RiverspringChinookSalmonfoundthatgeneticdiversity hadnotsignifi cantlychangedfromthepresupplemented populationasaresultofthehatcherysupplementationor captivebroodprograms(KasslerandDean 2010).Similarly,geneticdiversityfromthreecaptivebroodstockand conventionalsupplementationprogramsintheGrande RondeRiverbasininOregon(CatherineCreek,Lostine River,andupperGrandeRondeRiver)didnotchange fromthepreprogramperiod(Eddyetal. 2018).Nonetheless,itshouldbenotedthatgeneticchangeintheTucannonpopulationcouldhaveoccurredatlocithatwerenot examined,orconversely,itispossiblethatthelackofany changecouldbeduetopoorreproductivesuccessofthe hatchery fish.Anotherpossibleexplanationisthatepigeneticmodification(Luyeretal. 2017)inducedbyhatchery rearing(intheabsenceofgeneticdifferentiation)caused thedifferencesinpostreleaseperformancebetweenthe CBPandHOR fishinourstudy. Brannonetal.(2004)believethatsomeofwhathas beenreferredtoas “domestication” isnotassociatedwith genotypebutratheracquiredphenotypicchangesthat maydisappearwheninthewildorinsubsequentgenerationsofnaturalproduction.Forexample,Gallinatand Chang(2013)foundthatTucannonRiverspringChinook SalmonCBP,releasedassmoltsandrecapturedasreturningage-4adults,hadsizeandfecunditydistributionsthat weresimilartoTucannonRiverHORadultsofthesame sizeandage.Theysuggestedthattheoriginaldifferences observedinfecundity,size,andloweggviabilityofthe captivebroodstockadultfemalescomparedwithHOR femaleswereenvironmentallyinducedratherthangenetic. Likewise,inthispaper,wedidnotobservesigni ficantdifferencesintotalandadultSARsbetweenthetwogroups eventhoughtheproportionofminijacksandjacksusedin spawningwasmuchhigherinthecaptivebroodstock(F1) thanforthesupplementationparentsoftheHORgroup (34.1%versus4.5%,respectively).Thiswaslikelydueto havingthesametargetsizeforsmoltsatreleaseandshows thattheCBPovercamepossiblegeneticshifttoyounger ageatmaturationfromtheirparents. Our findingswouldsuggestthatatleastsomeofthe observeddifferencesbetweentheHORandCBPgroups canbeexplainedbypoorearlygametesurvival(eggto fry,eggtosmolt)oftheCBPratherthanbeingcausedby domesticationeffects.Manysalmonhatcheriesstilllack theknowledgetorearcaptivebroodstockthatproduce gametesthatareequaltobothsupplementationprograms andnaturallyproduced fish.Ithasbeenindicatedinearlierstudiesthatdecreasedbodysizeandeggqualitycould leadtolowersurvivorshipofprogeny(BeachamandMurray 1987).Despitetheirsmallersizeonaverage,age-4 TucannonRiverspringChinookSalmoncaptivebroodstockfemaleshadsigni ficantlylargereggsthanNORand HORage-4femalesderivedfromthesamepopulation, evenafteraccountingfor fi shlengthandfecundity(GallinatandChang 2013).Eggsizehasbeenshowntobe stronglycorrelatedwithinitialoffspringfrysizeinsalmonids,andoffspringsizeisinturncorrelatedwithsurvival insalmonids(Kinnisonetal. 2001).However,largeegg sizeoftheTucannonRiverspringChinookSalmoncaptivebroodstockwasinsuf ficienttocompensateforother deficienciesanddidnotincreasesurvivalinourstudypopulationsincemortalitytoeye-upwas49%forcaptive broodstockeggscomparedwithHORandNOReye-up FIGURE9.Adult(ages4+)progeny-to-parent(P:P)ratioofTucannonRiverspringChinookcaptivebroodstockprogeny(CBP),hatcherysupplementation(HOR) fish,andnatural-origin(NOR) fishforthe1985 2016broodyears.Theblacklinerepresentsthereplacementlevel. COMMUNICATION 11
mortalitiesof4%and3%,respectively(Gallinatand Chang 2013). WhiledifferencesinSARsbetweenthetwogroupswere notstatisticallysignifi cant,theCBPgrouphadconsistentlylowerSARs.Similartoourresults,Feldhausetal. (2020)reportedSARs(ages3 5)that,onaverage,were higherforHOR fishthanforCBPfromtheirCatherine Creek,upperGrandeRondeRiver,andLostineRiver springChinookSalmoncaptivebroodstockprogramsin theGrandeRondeRiverbasin.The fishinourstudysurvivedatahigherrateafterincreasingsizeatrelease, whichwouldsuggestthatatleastsomeenvironmentalfactorspostreleasewerelimitingadultreturnsandsurvival. Likewise,Johnsonetal.(2020)foundthatlarger(average 46g)SockeyeSalmonsmoltshadhigherSARsthansmaller(average16g)smolts(0.54%versus0.23%,respectively).Full-termsmoltproductionalsoproducedthe highestrecruitmentamongothertestedreleasestrategies (e.g.,eyedeggsandpresmolts)forRedfi shLakeSockeye Salmonandhasbecomethefocusofrecoveryefforts involvingjuvenilereleases(Johnsonetal. fishatrelease(HSRG 2002).TheWhiteRivercaptive broodstockprogramfailedduetopoorsmoltqualityand highpostreleasemortality,whichproducedalmostno adults,andtheprogramwasendedwiththe2013BY (Hillmanetal. 2021). Manysalmonidpopulationsintheirnativerangesare experiencingunprecedentedpopulationdeclinesand/or lowlevelsofnaturalrecruitment(Fraser 2008).However, thelong-termsolutionstoenvironmentaldegradationare oftenmoredifficultthanthedecisiontoestablishacaptive broodstockprogram(Snyderetal. 1996).Whiletheuseof captivepopulationsmayhelpfocuspublicinterestonthe plightofanimperiledspecies,itmayalsoprovidefalse hopethataspeciesissafeandallowthedestructionofthe habitattocontinue(Snyderetal. 1996).Thenaturaland humanfactorsthatcausedtheTucannonRiverspring ChinookSalmonpopulationtobelistedinthe firstplace (constructionandoperationoftheFederalColumbiaand SnakeRiverhydropowersystem,habitatdegradation withintheTucannonRiverbasin,globalclimatechange, andvariableoceanconditions)havenotbeenalleviated sincethecaptivebroodstockprogramwasended.While someimprovementshavebeenmadetotheoperationof thehydrosystemtoimprovedownstreammigrationsuccess (CSS 2019)andhabitatrestorationeffortsintheTucannon
bothsupplementationandcaptivebroodstockprogramsis
2020).Theystatedthatthedemographicbene fitrealizedbyrearingto smoltsizeoutweighsthepotentialincreaseindomesticationselectionthatmightoccurwithlongertimespentin captivitybythejuveniles(Johnsonetal. 2020). Othercaptivebroodstockprogramshavealsofailedto meetexpectations.TheDungenessRiverChinookSalmon captivebroodstockprogramwasnotsuccessfulinrebuildingruns,whichmayhavebeenduetothesmallsizeof
goingextinct(KlineandFlagg 2014).IntheTucannon River,NOR fi shformostyearshavebeenbelowreplacementlevels.Assuch,theTucannonRiverspringChinook SalmonHORprogramhasgenerallymaintainedoverall abundanceandmayhavepreventedmoreseriouspopulationbottleneckshadtheprogramnotbeeninplace(Gallinatetal. 2008). Humanshaveyettogenerateacaptivebredorreared fishthat,onaverage,willperformequallytowild fish oncetheyarereleasedintothewild(Fraser 2008).Our resultswerenodifferent.Duetotheirverynature,the majorityofcaptivebroodstockprogramshavenospeci fic endpointandcontinuetooperatewhilethefactorsthat causedthepopulationdeclinesarebeingaddressed. Becauseoftheirunintendedconsequencesonphenotype, populationstructure,andbehaviorandultimatelyonthe viabilityofthepopulation,ithasbeenrecommendedthat captivebreedingshouldbeusedasalastresorttoavoid extinctionandnotusedasalong-termsolution(Snyderet al. 1996;McClureetal. 2008). Inhindsight,thedecisiontostartacaptivebroodstock programfortheTucannonRiverspringChinookSalmon mayhavebeenpremature.Snyderetal.(1996)statedthat demonstratingthataspeciespopulationisdecliningorhas fallenbelowwhatmaybeaminimumviablesizedoesnot constituteenoughanalysistojustifycaptivebreedingasa recoverymeasure.Thetimeperiodofourstudycoincided withrelativelygoodoceanconditionsandhighNORsurvivalrates,andbecauseofthose,thepopulationwasable toreboundfromthepersistentlowreturnsinthemidto late1990s. Notallcaptivebroodstockprogramshaveseenpoor results.TheRedfishLakeSockeyeSalmoncaptive 12 GALLINATETAL.
Riverhavebeenon-goingoverthelastdecade(Foltzand Buelow 2020),otherlimitingfactors(e.g.,globalclimate change,Pacifi cDecadalOscillation)continuetodrivethe statusoftheTucannonRiverspringChinookSalmon population(Lawson 1993;Wellsetal. 2006;Crozieretal. 2021). Tothisday,theuseofanadromousPaci ficsalmonin unprovenasaconservationmeasureintherecoveryand restorationoflistedpopulations.Vendittietal.(2018) examinedsupplementedandnonsupplementedpopulations ofChinookSalmonpopulationspriorto,during,andafter endingsupplementationintwomajordrainagesinIdaho. Theyfoundthatsupplementationincreasedabundanceat somelifestages;however,theeffectsdidnotpersistafter supplementationendedandhadnoinfluenceonproductivity(Vendittietal. 2018).Wealsodidnotseeanypersistenceinabundanceandproductivityintheyearsafterthe captivebroodstockprogramended.Nevertheless,these typesofhatcheryprogramsaretheonlyreasonsome imperiledpopulationshavecontinuedtopersistinsteadof
broodstockprogramhasachievedgreatersuccessthan othersalmonidcaptivebroodstockprogramsandhas,by allaccounts,savedthestockfromextinction(Klineand Flagg 2014).However,evenfortheRedfishLakeSockeye Salmonprogram,whichbeganin1991,substantial increasesinSARratesmustoccurifcompleterecoveryof thatpopulationistooccur(Hebdonetal. 2004).Ourexperiencewillhopefullyserveasacautionarylessontoothers consideringbeginningacaptivebroodstockprogram.Captivebroodstockprogramsbythemselvesarenotapanacea andwillnotbeenoughtoreestablishlistedsalmonids unlessthefactorsthatcontributedtotheirdeclineare resolvedoralleviated(Flaggetal. 1995;Fraser 2008). ACKNOWLEDGMENTS WewouldliketoexpressoursinceregratitudetoformerLyonsFerryHatcheryComplexManagersHarold “Butch” Harty,thelateDonPeterson,MikeLewis,Steve Rodgers,andJonLovrak,fortheircoordinationefforts andoversightofhatcheryoperationsduringthelengthof thecaptivebroodprogram.WethankDougMaxey,Dick Rogers,andBruceWaltersfortheircooperationwith hatcherysamplingandprovidinginformationregarding hatcheryoperationsandrecords.Wearealsoindebtedto JerryDedloff,DebbieMilks,MarkSchuck,MichelleVarney,andotherstaffmembersoftheSnakeRiverLabthat providedhelpfulassistanceduringspawning,PITtagging, spawninggroundsurveys,andsmolttrapping.DaleGombertprovidedthemap.DanBakerandDavidVenditti fromtheIdahoDepartmentofFishandGameprovided helpfulinformationontheRedfishLakeSockeyeSalmon captivebroodstockprogram.AlfHaukenes,AnyaHuff, GaryMarston,andthreeanonymousreviewersprovided constructivecommentsonthemanuscript.Thecaptive broodstockprogram(Project2000-019-00)wasfundedby theBonnevillePowerAdministration,U.S.Departmentof Energy.TheconventionalhatcherysupplementationprogramisfundedbytheU.S.FishandWildlifeService throughtheLowerSnakeRiverCompensationPlan Office.Theuseoftradeorcompanynamesisfordescriptivepurposesanddoesnotimplyendorsementbythe WashingtonDepartmentofFishandWildlife.Thereisno confl ictofinterestdeclaredinthisarticle. 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