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If you build it, will they come? Spawning habitat remediation for sturgeon

Wiley
Journal of Applied Ichthyology
Authors:

Abstract

Habitat loss is a widely recognized contributor to global declines in sturgeon populations yet habitat remediation has been limited for this highly endangered group of fish. In support of future sturgeon restoration efforts, this review examines habitat remediation needs and uncertainties. Consideration of the bio-spatial scale of remediation identified needs ranging from local to the whole river scale. Additionally, the context of remediation ranges from reintroducing sturgeon to habitats where they have been extirpated to conservation of currently functional habitat. While multiple remediation scales and contexts are discussed, the focus on spawning and early rearing habitat and associated biological and physical monitoring reflects the range of current projects and the importance of early rearing habitats. Four case studies are presented that examine four distinct remediation contexts (mitigation, rejuvenation, re-creation, repatriation) and three bio-spatial scales (whole river, spawning reach, spawning location) under which remediation has been attempted. Evaluation of existing remediation works indicates that many show limited long-term success, which is most often a response to substrate infilling in remediated habitats. Material presented in this review will help align sturgeon research and monitoring approaches in support of effective remediation. The limited number of remediation projects to-date attests to the importance of learning from existing projects and cross-species comparisons, to maximize the effectiveness of future restoration efforts.
J Appl Ichthyol. 2017;1–21. wileyonlinelibrary.com/journal/jai  
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© 2017 Blackwell Verlag GmbH
Received:8May2017 
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Accepted:5July2017
DOI:10.1111/jai.13566
STURGEON PAPER
If you build it, will they come? Spawning habitat remediation
for sturgeon
S. O. McAdam1| J. A. Crossman2| C. Williamson3| I. St-Onge4| R. Dion5|
B. A. Manny6| J. Gessner7
1BritishColumbiaMinistryof
Environment,UniversityofBritishColumbia,
Vancouver,BC,Canada
2EnvironmentalRiskManagement,BCHydro,
Castlegar,BC,Canada
3FreshwaterFisheriesSocietyofBritish
Columbia,Vanderhoof,BC,Canada
4Conseillèreenvironnement,Hydro-Québec
Équipement,Montréal,QC,Canada
5Conseillerenvironnement,Hydro-Québec
Production,Montréal,QC,Canada
6USGeologicalSurvey,GreatLakesScience
Center,AnnArbor,MI,USA
7Leibniz-InstituteforFreshwaterEcologyand
InlandFisheries,Berlin,Germany
Correspondence
StevenO.McAdam,BritishColumbia
MinistryofEnvironment,UniversityofBritish
Columbia,Vancouver,BC,Canada.
Email:Steve.McAdam@gov.bc.ca
Summary
Habitatlossisawidelyrecognizedcontributortoglobaldeclinesinsturgeonpopula-
tionsyethabitatremediationhasbeenlimitedforthishighlyendangeredgroupoffish.
Insupportoffuturesturgeonrestorationefforts,thisreviewexamineshabitatreme-
diationneedsanduncertainties.Considerationofthebio-spatialscaleofremediation
identifiedneedsrangingfromlocaltothewholeriverscale.Additionally,thecontext
ofremediationrangesfromreintroducingsturgeontohabitatswheretheyhavebeen
extirpatedtoconservationofcurrentlyfunctionalhabitat.Whilemultipleremediation
scalesandcontextsarediscussed,thefocusonspawningandearlyrearinghabitatand
associatedbiological and physical monitoringreflects the range ofcurrent projects
andtheimportanceofearlyrearinghabitats.Fourcasestudiesarepresentedthatex-
aminefourdistinctremediationcontexts(mitigation,rejuvenation,re-creation,repa-
triation)andthreebio-spatialscales(wholeriver,spawningreach,spawninglocation)
under which remediation has been attempted. Evaluation of existing remediation
worksindicatesthatmanyshowlimitedlong-termsuccess,whichismostoftenare-
sponsetosubstrateinfillinginremediatedhabitats.Materialpresentedinthisreview
willhelpalignsturgeon research and monitoring approachesinsupportofeffective
remediation.Thelimitednumberofremediationprojectsto-dateatteststotheimpor-
tanceof learningfromexistingprojectsandcross-speciescomparisons,tomaximize
theeffectivenessoffuturerestorationefforts.
1 | INTRODUCTION
Overfishingandhabitatlossarethepredominantcausesofsturgeon
declinesworldwide(Rosenthal,Pourkazemi,& Bruch,2006).Within
thebroadcategoryofhabitatloss,awidearrayofanthropogenichab-
itatimpacts have beenidentified,includingriverregulationfor navi-
gation,floodprevention,and power generation,aswellaspollution
from industrial activities (e.g., Gessner &Jarić, 2014; Luk’yanenko
etal., 1999; Secor etal., 2002). River regulation has particularly
strongeffectsonsturgeonin response to impacts including habitat
fragmentation(Jageretal.,2001),blockedmigration,andbothdirect
(e.g.,dailyandseasonalflowmodification)andindirect(e.g.,tempera-
ture, nutrient levels, hydraulicconditions, substrate) effects of flow
regulation(Petts,1984;Pettsetal.,1989;WardandStanford,1989).
Vulnerabilityofthisancientgroupoffishestoriverregulationisfur-
therincreasedbytheirrestrictiontolargeriversinthenorthernhemi-
sphere,most of whichareregulatedor highlymodified(Dynesius&
Nilsson,1994).
Human disruption of natural hydro-geomorphological processes
thatcreate andmaintainriverinehabitats aswellas outrighthabitat
destruction,hasprogressedtothepointthatremediationisessential
tosustain habitat conditions for natural reproductionofmanystur-
geon. Despite widespread loss and alteration of sturgeon habitats
worldwide,habitatrestorationforthishighlyendangeredgroupoffish
hasbeen limited.Todate,threekeyfactors mayunderlie thelimited
remediationandsuccess.First,theultimatecausesofriverinehabitat
alterationsthataffectsturgeon(i.e.,constructionofshippingchannels
orlargedams)areoftenconsideredirreversibleimpacts(Ligonetal.,
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1995; Petts etal., 1989). Second, biological uncertainty continues
to limit the identification of effective remediation measures. Third,
monitoringofpastremediationworksidentifiestheneed forgreater
consideration of geomorphologicaleffects, to ensure the continued
effectivenessoftheremediation(Kinzel,Nelson,Kennedy,&Bennion,
2016;Loganetal.,2011;McDonaldetal.,2010).Thedireconserva-
tionstatusofmanysturgeon(Pikitch,Doukakis,Lauck,Chakrabarty,&
Erickson,2005)emphasizestheneedfortimelyaction.Afewnotable
examplesprovideconfidencethatphysicalhabitatremediationcanbe
successful(e.g.,Dumontetal.,2011),as doessubstantialexperience
withotherfishspecies(e.g.,salmonids;Wheatonetal.,2004).
Understandingcurrenthabitatlimitationsisanimportantrequire-
mentforeffectivehabitat remediation (Rosenfeld & Hatfield, 2006)
and,formost sturgeon, detailedknowledgeoftheir habitat require-
mentslimitsremediation.Generalhabitatusehasbeendescribedfor
manyspecies(Bemis&Kynard,1997;Fox,Hightower,&Parauka,2002;
Hildebrandetal.,2016),however,fewstudieshavespecificallyiden-
tifiedlimitinghabitats(e.g.,McAdam, 2015). Restorationneeds may
varydependingonthecausesofpopulationdeclines.Insome cases,
remediationmayberequiredthroughoutmodifiedrivercorridors.In
othercases site-specificremediationmay besufficient,forexample,
theremediationofspawningandearlyrearinghabitats.Whileabroad
spectrum of remediation needs is discussed (including fish passage
andflow restoration),ourfocusonspawning andearlyrearing habi-
tatreflectsthefocusofcurrentremediationprojects.Ourfocusalso
reflectstheimportanceofearlylifehistorysurvivaltorecruitmentand
theidentifiedlinksbetweenrecruitmentfailureandimpactstospawn-
ing and early rearing habitat(Gessner, Kamerichs, Kloas, & Wuertz,
2009; Hastings etal., 2013; McAdam, 2015; McAdam etal., 2005;
Paragamianetal.,2009).
Conservation fish culture has also been employed to mitigate
immediateextirpationrisksformany populations, and if carried out
withnecessaryprecautioncanprovideinterimcompensationforlow
recruitment (Chebanov, Karnaukhov, Galich, & Chmir,2002; Ireland
etal., 2002; Secor etal., 2002). Genetic considerations associated
with conservation fish culture include the importance of maintain-
ing genetic diversity through practices such as factorial breeding
and equalizing releases among families and years (Boscari, Pujolar,
Dupanloup, Corradin, & Congiu, 2014; Ireland etal., 2002). Dueto
thehighfecundityofsturgeon,failuretoplanandmonitorthegenetic
consequencesofstockingcreatesthepotentialfornegativeeffectson
geneticdiversity.Approachessuchasthecaptureandrearingofwild
progeny(e.g.,feedinglarvae)canhavesignificantbenefitsforgenetic
diversityof releasedfish(Schreierand May, 2012).Additionally,the
potentialforphenotypiceffectsofcaptiverearingshould beconsid-
ered,whichisreflectedinrecentresearchsuchaslife-skillstrainingin
lakesturgeon(Sloychuketal.,2016)andthecarryovereffectsofearly
rearing habitats (Boucher, McAdam, & Shrimpton, 2014; Johnsson,
Brockmark,&Näslund,2014).Despitetheimportanceofconservation
fishculturewithinrecoveryprograms,thisisnotspecificallyaddressed
inthisreviewbecauseofa)thefocusofthereviewisonhabitatreme-
diation,andb)theprincipleofnaturalreproductionmustbetheulti-
mategoalofrecoveryefforts.
Ourinvestigationofsturgeon restorationneeds to identifiedthe
importance of contextual (Text Box 1) and bio-spatial factors that
influencethescaleofremediation(TextBox2).Forexample,repatria-
tiontoformerlyoccupiedrivers,potentiallyincludingtheneedforfish
passage(e.g.,Europeansturgeon(Acipenser sturio)andBalticsturgeon
(Acipenser oxyrinchus))presentsubstantiallygreaterchallengesdueto
theirneedforde novohabitatcreation,plustheneedtoaddressmul-
tiplespatial scalesandlifestages.Formostspecies,the presenceof
continuedbiologicaluncertainty means thata“builditandtheywill
come”approachentailssubstantialrisk.Thelargescale of potential
recoveryprojectsalsomeansthateconomicrisksmaybesubstantial.
Our consideration of multiple species emphasizesthe potential for
knowledgetransferamong species(to-dateoftenlimited) tosupport
moretimelyandeffectiverecoveryprogramsforsturgeon.
1.1 | Spawning habitat remediation
Ouridentificationoffour remediationcontextsandthreebio-spatial
scales (Text Boxes 1 and 2) provides a structured way to examine
remediation needs and their expected complexities (Table1). The
needto address remediationatthewatershed scaleisafunction of
thelargeriver habitats occupiedbysturgeon,and the long distance
migrationsofsomespecies.Theemphasisofcurrentremediationon
spawningandearlyrearinghabitatlikely reflectsan insufficientcon-
siderationofsturgeonmigratoryneedswhendamswereconstructed.
Inmanycases,largerscaleremediationmayberequired;ourfocuson
currentspawningandearlyrearingprojectsshouldnotbeinterpreted
asimplyingalesserimportanceoflargerscalerestoration.Ourdiscus-
sionof thebiologicalrequirements areassociatedwith theneedsof
sturgeonrestorationprogressfromlargertosmallspatialscales.
Manysturgeonundergolarge-scalemigrations(e.g.,1,000kmfor
Chinesesturgeon,Acipenser sinensis(Weietal.,1997),andthelossin
connectivityisawidelyrecognizedimpactofriverregulation.Thehigh
energeticcostoflong-distanceupstreammigrationsimpliesthepres-
enceofsubstantialbiologicalbenefits.Somespeciesandpopulations
are still able to undertake long distance migrations(Bruch, Haxton,
Koenigs,Welsh,&Kerr,2016;DFO,2014;Duongetal.,2011;Phelps
etal.,2016),andmaintainingthecurrentlevelsofriverineconnectiv-
itycanbecriticalforthosepopulations.Whilespawningdownstream
Uncertainty Repatriation Re- creation Remediation Mitigation
Recolonization XX
Habitatuse XX XX
Habitatsuitability XX XX XX X
TABLE1 Categoriesofuncertainty
associatedwithdifferentcontextsfor
sturgeonspawninghabitatremediation
(X=indicatesuncertainty,XX=indicates
highuncertainty)
    
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MCADAM et Al.
of migratory barriers is widely observed, such locations might not
provide the biological benefits associated with upstream spawning
locations(seebelow).Forexample,lostmigratoryaccessconcentrates
spawningintailraceareasofhydroelectricfacilities,whichcancontain
eitherunsuitablehabitats(Cooke& Leach,2004;Terraquatic,2011)
oramuchreducedarea of potential spawning habitat (Chebanov&
Savelyeva, 1999; Khodorevskaya etal., 2009; Zhang etal., 2013).
Maintaining the existing connectivity is thus preferred (see Rupert
Rivercasestudy)intheabsenceofunderstandinghowtofullymitigate
thebenefitsaccruedbymigrating(seeBrownetal.,2013).
Fishpassageoffersapotentialmeanstorestoreconnectivity;how-
ever,fishpassagefacilitiesaremostoftendesignedforotherspecies
(e.g.,salmonids)andshowalimitedeffectivenessforsturgeon.Useof
fishpassagefacilitiesbysturgeonhasbeennotedatfishladders(Parsley
etal.,2007;Bruch,2008;Thiemetal.,2011,2016),boatlocks(Cooke,
Leach, Isely,Van Winkle, &Anders, 2002) and fish lifts (Ducheney,
Murray, Waldrip, & Tomichek, 2006; Warren and Beckman, 1993),
althoughstudiestypicallyreportlowlevelsofpassage.Recentlabora-
torystudieshaveaddressedspecificrequirementsofsturgeonforfish
passage(Cocherelletal.,2011;Kynardetal.,2011a;McDougalletal.,
Box 1
Mitigation: Functional populations are present and the goal is to increase or maintain the availability and quality of sturgeon habitat.
Mitigationimpliesconfidenceintheefficacyofspawninghabitatremediation,butmaybechallengingforspecieswithpersistentbiological
uncertainty.
Rejuvenation:Remediationisrequiredtoimprovethequalityofdegradedhabitatsthatcontinuetobeusedbyspawningwildadults.For
example,recentevidence(McAdametal.2005, Paragamianetal. 2009,McAdam2015)supportstheneedforsubstrateremediationat
spawningsitestoaddressongoingrecruitmentfailuresofwhitesturgeon.Evenwhencontemporaryspawninglocationsareknown,ensur-
ingthesuccess of large scale remediation projectsrequiresdetailedinformationregardingspawning site selection and the biophysical
propertiesthatsupportrecruitment.
Re-creation:Extensivehabitatmodificationanddestructioninsomeriversleadstotheneedtocreatenewspawningsites.Althoughadults
arestillpresentin suchcases, complexityiselevatedbecausesuitablespawninglocations andsubstratesmaybeunknownorassumed.
Habitatre-creationrequiresknowledgeaboutalllifestagesofsturgeontoensure effectiveimplementation andtodiminishuncertainty
regardingtherecolonizationanduseofnewlyconstructedhabitat.
Repatriation:Returningsturgeontoriversfrom whichthey havebeenextirpated(e.g.,Europeansturgeon)representsthemostcomplex
formofremediationandfacessubstantialuncertainty.Evaluationofthehabitatcapacityofrecipientrivers(GessnerandBartel2000,Arndt
etal.2006)ischallengingintheabsenceofsturgeon,particularlywhenhabitatmodificationshavebeenextensive.Forspeciesforwhich
remediationworkisjustbeginning,substantialgainsmaybeachievedbycrossspeciescomparisons.
Box 2
Whole river scale:Longdistancemigrationsarepartofthelifehistoryofmanysturgeons,andthenegativeeffectsofriverimpoundmenton
migrationarewidelyrecognized(Auer1996a,Weietal.1997,Khodorevskayaetal.2009).Largescalecontinuityofriverinehabitatisalso
asuggestedrequirementforlarvaldriftofpallidsturgeon(Braatenetal.2012)andChinesesturgeon(Zhuangetal.2002).Riversalsointe-
gratemultiplewatershed scale processes creating thepotentialneedforuplandhabitat restoration to diminish theirsecondarydown-
streameffects(e.g.,runoffandsedimentbudgeteffectsofdeforestation).
Reach scale:Withinaselectedriverreach,spawninghabitatselectionispredominantlyinfluencedbyhydraulicconditions,withspawning
generallyoccurringinhighervelocityareas(e.g. >1m/sec;ParsleyandBeckman1994,Ban,Du,Liu,&Ling,2011,Bennionand Manny
2014).Detailedevaluationofhydraulicconditions(Zhangetal.2009,Duetal.2011,Muirhead2014)alsosuggeststheimportanceofele-
mentssuchasturbulence,heterogeneousconditionsandlargeroughnesselements.Constantflowmayalsobeimportant,asflowfluctua-
tions(i.e.,peaking)downstreamofdamscannegativelyaffectspawning(Auer1996b).Repeatedspatialpatternsofspawninghabitatuse
inlakesturgeon(Duongetal.2011)alsosuggestthepresenceofadditional(undefined)preferencesatthesub-reachscale.
Spawning sites:Linksbetweenrecruitmentfailureandalteredsubstrateconditionsatspawningsitesdemonstratethecriticalimportanceof
benthicsubstratestotheproperfunctioningofSERhabitat(McAdametal.2005,Paragamianetal.2009,Hastingsetal.2013).Negative
effectsof degradedsubstrateshavebeen identifiedforeggs (Kocketal.2006,Forsythe etal.2013)and yolksaclarvae(Gadomskiand
Parsley2005b,Gessneretal.2009,McAdam2011,Boucheretal.2014).Impactsuponfeedinglarvae(e.g.diminishedfoodsupply)arealso
possible(Howell andMclellan2011).Whilemultipleattributesofspawning habitathavebeen described(e.g.,depth, temperature)sub-
strateistheattributecommonlyaddressedbyremediation.
4 
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   MCADAM et Al.
2014),and the larger size ofsturgeonand their benthic orientation
present important design requirements (Jager etal., 2016; McElroy
etal.,2012;Thiemetal.,2011).Downstreampassagealsopresentsa
criticalchallenge,sincemortalityassociatedwithdownstreampassage
maydiminishthebenefitsofrestoringupstreampassage.Downstream
passagesurvivalratesvary,dependingbothonthepassageroute(e.g.,
turbines,spillway)and the size of the fish (Kynard& Horgan, 2001;
McDougall etal., 2014). Thelarge size of adult sturgeon can mean
thatthetrashrackspreventdownstreammovementviaturbines,and
as a result the fish of intermediatesize may be most vulnerable to
mortalityduringturbinepassage(Jageretal.,2016).Whiletherearea
fewnotableexamplesofsuccessfulupstreamordownstreampassage
(e.g.,Parsleyetal.,2007;Thiemetal.,2011),currentfindingsgenerally
indicatetheneedforfurtherresearchtoidentifymethodsforeffective
passageforsturgeon(seeCookeetal.,2002;Jageretal.,2016).
Identificationofanextensivedriftduringtheyolk-saclarvalstageof
somesturgeon(Braatenetal.,2012;Zhuang,Kynard,Zhang,Zhang,&
Cao,2002)suggeststhatcontiguoussectionsofun-impoundedriverine
habitatare requiredto supportpopulationviability.The identification
ofbothdriftandhidingbehaviourbyyolk-saclarvaehascriticalimpli-
cationsforthespatialscaleofhabitatremediationforthislifestage,and
thereforerepresentsacritical information requirementto plan reme-
diation.Whileinferringnaturalbehavioursfromresponses in altered
environmentsand laboratorystudies requires caution (Gessneretal.,
2009;McAdam2011),arecentstudyofpallidsturgeon(Scaphyrhinchus
albus)providesclearevidenceofearlydriftrequirementsforthatspe-
cies(DeLonayetal.,2015).Forspeciesthatrequirelongdistancelarval
drift, mortality associated with movements into inhospitable reser-
voir environmentsmay lead to recruitment failure (Guyetal., 2015).
Restoration of contiguous riverine habitats represents a substantial
andchallengingundertakingthatmayrequiredamremoval.Ongoing
researchforpallidsturgeonrecoveryprovidesthemostextensiveeval-
uation of the need forlarval drift and potential remediation actions
(Erwin&Jacobson,2015;Jacobsonetal.,2016),however,remediation
actionstoextendlarvaldriftdistanceshavenotyetbeenimplemented.
Flow restorationrepresents another remediation approach based
ontheassociationbetweensturgeonpopulationdeclinesandriverflow
regulation (Gessner& Bartel, 2000; Gessner, Spratte, & Kirschbaum,
2011;Luk’yanenkoetal.,1999;Pettsetal.,1989).Thepositivecorrela-
tionbetweenfreshetflowsandrecruitmentforsomespecies(Dumont
etal.,2011; Kohlhorst,Botsford,Brennan,&Cailliet,1991;Niloetal.,
1997) suggest the importance of the magnitude of freshet flows.
Unfortunately,thelarge-scaleanthropogenicchangesthataffectriver
flow(dams,floodplain abstraction,inland navigation)make full resto-
rationchallenging andpossiblyunfeasible.Intheabsenceof full-scale
restorationoffreshet flows, partial remediationrequires a mechanis-
tic understanding of howflow affects fish abundance. Without such
knowledge it becomes uncertain whether partial solutions (e.g., the
timingbutnotthe full magnitude ofhistoricalfreshetflows)willpro-
videthedesiredoutcomes(Wohletal., 2015). Beneficial effects ofa
conservationbaseflowintheRupertRiver(seecasestudies)providea
recentexampleofpositiveoutcomesofflowmitigationforanewproj-
ect.Potentialbenefitsofflowrestorationforwhitesturgeon(Acipenser
transmontanus)recruitmenthavealsobeensuggested(UCWSRI,2013).
However, experimental flow restoration in the Kootenai River pro-
vidednodetectablerecruitmentresponse(Paragamian,2012).Limited
recruitmentresponsestonaturallyhighflowsinothercases(McAdam,
2015;McAdametal.,2005)suggestthatflowalonemaybeinsufficient
torestorerecruitment.Understandingtherelationshipbetweenriver
flow,sturgeonhabitatandpopulationresponsesisthereforeparamount
tothedesignandimplementationofeffectiveflowremediation.
Damoperationsalsoaffectreachscalehabitatconditions,withthe
potentialforbothpositiveandnegativeeffects.Shorttermflowfluc-
tuations(e.g.,inresponsetoshorttermchangesinelectricitydemand)
havebeenassociatedwithdiminisheduse byspawning adults(Auer,
1996a), egg stranding (Gessner etal., 2011; DFO [Fisheries and
Oceans Canada], 2014), and maystimulate larval drift (Crossman &
Hildebrand,2014).Whiletherestorationofminimumflowsistypically
consideredoneofthefirststepsinaflowrestorationprogram(Auer,
1996b),site-specifichydraulicmodelsmayberequiredtodemonstrate
beneficial effects (Hildebrand etal., 2014). For remediation works
immediatelydownstreamofdams,releasesmightalsobeadjustedto
ensuretheprovisionofsuitablehabitatsconditions(i.e.,maximizethe
areaofspawningandearlyrearinghabitat).
Theneedforreachscalerestorationreflectstheeffectsofhydraulic
conditionsonspawninghabitatselectionandreachscalefluvialgeomor-
phology.Alteredhydraulicconditionsin spawning habitats (Muirhead,
2014;Paragamianetal.,2001;Zhangetal.,2009)shouldbeaddressed
duringplanningstagesofremediationworkstoensuretheutilizationand
maintenanceofremediatedareas(seecasestudies).Thedynamicnature
ofriverchannels(Church,1995)emphasizesthatlong-termpersistence
ofremediationworkswillrequiredetailedanalysisofreachscalefluvial
geomorphologyin order to incorporate long-term channel changes at
theprojectdesignstage.Theseconsiderationsmaybemostimportant
forremediationinnon-tailracelocationswheretheremaybe agreater
riskofunderutilizationifrestoredhabitatsarelocatedinunsuitableareas
(e.g.,Vlasenko,1974).Itisalsoimportanttoconsiderthatmanipulation
ofhydraulicconditionsinspawningreachesmayprovideanopportunity
toconcentratespawningindesiredareas,ortoavoidothers;however,
suchapplicationswill requireanimprovedunderstandingofspawning
habitatselection.Theneedforreachscaleconsiderationsisrecognized
insomerecoveryprograms(KTOI[KootenaiTribeofIdaho],2009;DFO,
2014).Whilewefoundnocurrentexamplesofcompletedworksatthis
scale,reachscalerestorationeffortsforwhitesturgeonareunderwayon
theKootenaiRiver(KTOI,2016).
Selecting the location for site-specific remediation of spawning
and early rearing habitat is a fundamental decisionwith potentially
highuncertainty.Insomecases,consistentspawningatawell-defined
spawningsiteclearlyidentifies potential remediation sites, although
spawning can persist in degraded spawning habitat (e.g., McAdam
etal.,2005).However,spawningsitesmaynotbeknowninallcases,
whichcreatesthepotentialthatremediatedhabitatsmightnotbefully
utilized.Forrepatriationandrecreationcontexts, although historical
sites might be known or inferred,current suitability may be limited
by subsequent habitat alterations (Arndt, Gessner, & Bartel, 2006).
Selectingremediation sitesmustalsoconsider potentialimplications
    
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MCADAM et Al.
ofspawningfidelitytospecificreaches(Folz&Meyers,1985;McAdam
etal.,2005) or sites within a reach (e.g., Forsythe,Crossman,Bello,
Baker,&Scribner,2012).Failuretofullyunderstandfactorsinfluencing
thespawninghabitatselection(e.g.,hydraulicconditions)mayleadto
limiteduseofremediatedhabitats,particularlyifthenumberofreme-
diationsitesislimited. Incases suchastheWolfRiverwhererip-rap
placementcreatedmultiple remediated sites,lakesturgeonselected
thenewly placedrip-rapwhenolder siteshadbecome coveredwith
silt,debrisoralgae(Folz&Meyers,1985).Whilethe constructionof
multiplesites mayallowhabitatselectionbyspawningsturgeonand
may support stronger recruitment responses, the potential impacts
ofdispersingspawnersshouldbe considered(e.g.,ifthe numbersof
spawningadultsislow,asinsomeendangeredpopulations).
Most successful examples of spawning and early rearing habitat
remediationaddresstheuseofdamtailracesbylakesturgeon(Table2).
Such locations increase the potential for success because the stur-
geon undertaking upstream spawning migrations are concentrated
at the barrier createdby the dam. Spawning locations are also fairly
consistentduetothepredictablehydraulicconditionsintailraceareas,
andfine sedimentinputsarelimiteddue tothepresenceofupstream
reservoirs. However, the area of available spawning habitat may be
substantially reduced relative to the extent of inaccessible upstream
habitat (Raspopov etal., 1994; Ruban and Khodorevskaya, 2011).
Remediation at non-tailrace locations often shows limited long-term
success due to factors such as inconsistent use by spawning adults
(Khoroshko&Vlasenko,1970),orthedepositionoffinesubstrateslead-
ingto decreasedeggoryolk-saclarvaesurvival (Table2,casestudies;
Veshchevetal.,2011).Greaterattentiontoreachscalehydrauliccondi-
tionsandtheireffectsonspawninglocationandsubstratewillhopefully
leadtoimprovedsuccessforremediationinnon-tailracehabitats.
Substrateaugmentation is the most common method forremedi-
ating sturgeon spawning and early rearinghabitat. Early remediation
workwasbasedonthereplicationofsubstratesfoundatnaturalspawn-
ingsitesas well asbeingthefortuitousresponse to riprapplacedto
improvebank stability (Folz&Meyers,1985). More recently,support
forsubstraterestorationhasbeenbasedonlinksbetweenrecruitment
failureandthedepositionoffinesubstrates(McAdam2015;McAdam
etal., 2005; McDonald etal., 2010). Interstitial habitats providedby
gravel/cobblesubstrates are important for the retentionand survival
oftheeggandlarvalstages(Crossman&Hildebrand, 2014;Forsythe,
Scribner,Crossman,Ragavendran,&Baker,2013;Johnsonetal.,2006b;
McAdam 2011). The recent identification of strong egg adhesion to
multiplesubstrates(ParsleyandKofoot,2013)suggeststhatsubstrate
type has a limited effect on egg retention. However, Johnson etal.
(2006b)and Forsytheetal. (2013)foundthat thepositionof adhered
eggsisimportantandthatinterstitialeggsshoweddecreasedpredation
mortalityrelativetoexposedeggs. Similarfindingsalsoapply toyolk-
saclarvae(Gessneretal.,2009;Hastingsetal.,2013,McAdam,2011)
for which substrateswith suitable interstitial habitats increase larval
retention(Crossman&Hildebrand,2014)anddecreasebothpredation
andnon-predationmortality(Boucheretal.,2014;Gadomski&Parsley,
2005a; McAdam, 2011). Recentidentification of strong physiological
benefits of enriched substrates (Baker, McAdam, Boucher,Huynh, &
Brauner,2014;Boucheretal.,2014;Gessneretal.,2009)providesfur-
therevidencefortheimportanceofinterstitialrearingofyolk-saclarvae.
Thesizeandarrangementofplacedsturgeonspawningsubstrates
representsacriticaldesigndecision;placedsubstratestypicallyinclude
largediametermaterialstolimitdownstreamdisplacementandsmaller
substratesthatprovidesuitably-sizedhidinghabitat.Previousspawn-
inghabitatrestorationprojectshaveused10-50cmbrokenlimestone
orgranite(Bruch&Binkowski,2002;Rosemanetal., 2011a,2011b),
5-15cmroundedigneouscobble(Mannyetal.,2005)and1-5cmcoal
cinders(Nicholsetal.,2003,Thomas&Haas,2004).Morerecentproj-
ectshaveusedamixtureofsubstratessizes(seecasestudies).Useof
substratesthataretoo large in diameter can limit the suitabilityfor
hidingbyyolk-saclarvae,leadingtodownstreamdisplacementoflar-
vae(McAdam,2011;Terraquatic(TerraquaticResourceManagement),
2011).Zhangetal.(2009)suggestedthata‘poolandriffle’structure
was beneficial and enhances interstitial waterflow, although under
somecircumstancesbottom reliefmaycontributetosedimentdepo-
sitionandinfillingofinterstitialspaces.Thetotalareaofremediation
sites also represents a critical design decision, due to the potential
foreggovercrowding(Dumontetal.,2011;KhoroshkoandVlasenko,
1970). Additionally, in larger rivers, the location of sites belowthe
photiczonemaylimitthenegativeeffectsofaquaticplants(Gendron,
Lafrance,&LaHaye,2002;Johnsonetal.,2006b).
The long-term effectiveness of remediated habitats is also a crit-
icalconsideration.Infillingofplacedsubstratesis the most commonly
observed limitation; however, growth of periphyton (Johnson etal.,
2006b)candiminishlong-termeffectiveness.Forexample,halfofthe18
examplespresentedinTable2arenegativelyaffectedbysedimentinfill-
ing.Addressingthischallengewillrequiregreaterinputfromthefieldof
fluvialgeomorphology.Sedimenttransportmodelsthatpredictfinesed-
imentmovementsatremediationsites canbeusedtoguide theplace-
ment,compositionandconfigurationofhabitatremediationareas(Kinzel
etal.,2016).Additionally,somerecentprojects(e.g.,St.LouisRiver;see
Aadland,2010;RupertRiver:seecasestudies)havegivenmoreattention
togeomorphologicaleffects.Insomecasesthecurrentflowregimesmay
notbecompetenttoprovidethecleaningrequiredmaintainthequality
ofremediated habitat area (e.g.,intheNechakoRiver; see Hildebrand
etal.,2016),leadingtotheneedforeither(i)repeatedphysicalcleaning
or(ii)large-scale engineering to re-sizetheriverchannel for the regu-
latedflowregime.Thelatteroptionentailssubstantialcostandbiological
uncertaintyandwouldrequireextensivesite-specificinformation.
Locatingrestoredhabitatsinexistingorconstructedsidechannels
maycircumventsomeofthechallengesassociatedwithmainstemloca-
tions,duetothepotentialfornaturalorartificiallydiminishedbedload,
butmayincreaselimitationswithregardtospawningsiteselection.In
theextreme,useofoff-channelhabitatsmightentailphysicallymov-
ingspawnerstoenclosedoff-channelraceways,whichmightfunction
similartosalmonidspawning channels.Whileearlyexperienceswith
thisapproachshowedlimitedsuccess(seeChebanov&Galich,2011),
positive results were achieved with shortnose sturgeon (Acipenser
brevirostrum)(Kynardetal.,2011b).Factorssuch asfishsizeandthe
associatedsizeofspawningchannelsaswellascaptivitystress(Genz
etal., 2014) may be important limitations ofthis approach. Further
6 
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   MCADAM et Al.
researchregardingspawningsiteselectionwouldbehighlybeneficial
forevaluatingoff-channelremediationoptions.
1.2 | Monitoring requirements
Monitoringtheeffectivenessofhabitatremediationprojectshelpsto
ensure that desired biological and physical responses are achieved,
and provides the basis for improved design of future projects. The
duration of monitoring programs should reflect the time scale of
expectedbiological(e.g.,juvenileproduction,adultreturns)andgeo-
morphological(e.g.,channelmovement,substrateinfilling)responses.
Ideally,biological monitoring shoulddemonstratethathabitat reme-
diationissupportingalltargetedlifestagesofsturgeon.Weelaborate
onthesesubjectsinfurtherdetailbelow.
1.2.1 | Biological Response
Use by spawning adult sturgeon
Useofrestoredspawninghabitatprovidesastraightforwardmetricof
remediationeffectiveness, with indicatorsofspawning rangingfrom
thepresence,density,anddepositionalpatternofeggs,tothenumber
ofspawnersandtheirsex ratios. For example, recent genetic stud-
iesprovideameanstoestimatethenumberofspawningadultsfrom
collectedwildprogeny(Jay etal., 2014; Manny etal., 2015). Direct
adultcounts(seeRupertRivercasestudy)andDIDSONacousticcam-
era(Bray, Crossman,Martel,& Johnson,2011)havealsobeusedto
detect spawning adults. Evaluation of changes in spawning habitat
useovertime should alsobeconsideredin combination with physi-
calmonitoring discussedbelow.For there-creationand repatriation
TABLE2 Detailsofspawninghabitatrestorationprojectsundertakenforsturgeon(LS=lakesturgeon(Acipenser fulvescens),WS=white
sturgeon,SVS=Sevryuga(Acipenser stellatus),RS=Russiansturgeon(Acipenser gueldenstaedtii))
River Species Area (m^2) Velocity (m/sec) Depth (m) Material
Substrate
depth (m)
Below dam (BD)/mid
reach (MR) Spawning (Y/N) Year built Comments References
DetroitandSt.Clair(see
Table4)
LS 39,000 0.5-0.7 5-10 Various(seeTable4;casestudy) 0.6 MR N(BelleIsle),Y(othersites,
someintermittent)
2004,2008,
2012-16
(Mannyetal.,2005),(Rosemanetal.,
2011b),(ThomasandHaas,2004)
Eastmain LS Na Na Na Na Na BD Na Na Compensationfor890m2habitat
impact
(EnvironnementIllimitéInc.,2009)
Kuban(upper) SVS 1.9ha 0.76-0.84 4-6 5-8cm,coarsesand,quarrystone 0.30 BD(80m) Y 1966 (Khoroshko&Vlasenko,1970)
Kuban(lower) SVS 1.6ha 0.88-0.94 4-5 Gravel,coarsesand,quarrystone Na BD(900m) Y-siltedafter3years 1966 (Vlasenko,1974),(Chebanov,Galich,
&Ananyev,2008),(Kerretal.,2010)
Ottawa LS Na Na Na 15-25cmrock Na BD TBD 2010/2012 RonThreader(pers.comm.)
DesPrairies LS 5,000and
8,000
1.0 1.5-3.0 20-30cm(areaencircledwith30-50cm
rockwithrowsof1mrock)
0.3 BD Y(alsoincreasedeggto
feedinglarvaesurvival)
1985,1996 13 m2/femalepreferred,sitesloped
soeffectiveatvariableflows
(Dumontetal.,2011),(LaHayeetal.,
1992)
Ouareau LS 3050 0.8-1.2(m/sec) 0.5-1.5 Sedimentaryblastrockandriverrock
(20-200mm)
0.30(min) MR(2.5km
down-stream)
N–atrestoredlocation,Y
–atnearbynaturalsite
2007,2008 Landslideaffectedqualityofnatural
spawningsite
(LaHayeandFortin,1990),(MRNF-
CARA,2011)
UpperBlackRiver LS 4locations Na Na Riprap Na BD(<2km) Na 1972 Sedimentationdecreased
effectiveness
(SmithandBaker,2005)
Saint-Maurice LS 2100 Na Na Largeboulderwith3-40cmmaterial
downstream
Na BD Y 1999 Multiplesmallsites (Faucher,1999),(Faucher&Abbott,
2001),(GDGConseilInc.,2001)
St.Lawrence
(Odensberg)
LS 36×36 Na 4.3 4-7cm 0.3 MR Y(initially) 1993 Effectivenessdecreased–siltation,
periphyton,zebramussels
(Johnsonetal.,2006b)
St.Lawrence(Iroquois) LS 2@929m20.6-0.7 10-12 5-10cm,largebouldersd/s 0.30 Aboveandbelow Y 2007 (McGrath,2009)
St.Lawrence
(Beauharnois)
LS 3000 0.46-0.98(also
intermittentlow
flowevents)
2.0-4.5 17-65mmand65mm-255mm,with1mx
5mblocksspacedat8m
0.30(min.) BD N 1998 Ineffectiveduetosiltation,
vegetation,unsuitableflow
(Gendronetal.,2002)
St.Louis LS Na Na Na 10-25cm(24%)
30-90cm(21%)
90-150cm(54%)
Na BD Yspawning,assessment
limitedtodate
2009 Steppedboulderclusters (Aadland,2010),Aadland,pers.
comm.
Volga RS ~11,000 0.5-1.0 3-4 5-10cm MR Rarely 1966 Sitetoofardownstreamofdam (Khoroshko&Vlasenko,1970)
Wolf/Fox LS >50sites Upto5m/sec Na 10-50cm Na MR Y Siltationatsomesites (Folz&Meyers,1985),(Bruch&
Binkowski,2002)
Columbia WS 1,000 Upto3m/sec Variable 2.5-30cm
(seecasestudy)
0.60 BD Unconfirmed 2011 Sitedegradedafter1year (Crossman&Hildebrand,2014)
Nechako WS 4,600 Upto2m/sec 1-3 25%2-4cm
35%4-15cm
40%15-20cm
0.30 MR Y2011 Smallrecruitmentresponse,sand
depositionat1of2sites
Author’spersonaldata,(nhc,2013b)
Rupert LS 2,060 0.2-1.8 0.6-2.1 4-40cm
(seecasestudy)
Na MR Y2010 (EnvironnementIllimitéInc.,2013)
    
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 7
MCADAM et Al.
contexts,thepresenceofspawningsturgeononnewlycreatedhabitat
isaspecialcaseofadultdetectionthatmayrequiresturgeontostray
fromestablishedspawningareas.Thepotentialthatlowstrayingrates
delay the re-establishment of spawning runs emphasizes the long-
termnatureofthismetric.Cross-speciescomparisonsandlong-term
researchincontrolled settings will alsoprovideimportantreference
studiesofbiologicalresponsestoconstructionofsturgeonspawning
habitat(e.g.,Forsytheetal.,2012;Pledgeretal.,2013).
Early life stage survival and production of feeding larvae
Monitoringshouldideallydemonstratesurvivalthroughtheegg,yolk-
sac,andfeedinglarvalstages,althoughthisisrarelydone.Quantifying
stage-based survivalmaynot bepossible,however, systematicmoni-
toringusingstandard techniques such as eggmats,benthicsampling
and drift nets, can be used to estimate egg deposition (Caroffino,
Sutton, Elliott, & Donofrio, 2010; Roseman etal., 2011a), egg loss
(Johnsonetal.,2006b),yolk-saclarvaesurvival(Johnsonetal.,2006b;
McAdam 2012) and larval dispersal (Crossman & Hildebrand, 2014;
Dumontetal.,2011;Rosemanetal.,2011a).Developmentalstagingof
eggsorlarvaeallowstheback-calculationofspawningtime(Jayetal.,
2014).Ontogeneticdriftpatterns(McAdam,2011)andlarvalquality
indicators(Bakeretal.,2014)alsoofferpotentialbiologicalindicators.
Forexample,driftbynewly-hatchedlarvaemaybeindicativeoflimited
larvalhidinginresponsetoremediation(e.g.,Crossman&Hildebrand,
2014; Khoroshko and Vlasenko, 1970; Raspopov etal., 1994).
Ultimately,consistentmonitoring of early life stages followingreme-
diationofspawninghabitat(possiblyusingmultiplemethods)isoneof
themostimportantfactorsindeterminingremediationeffectiveness.
TABLE2 Detailsofspawninghabitatrestorationprojectsundertakenforsturgeon(LS=lakesturgeon(Acipenser fulvescens),WS=white
sturgeon,SVS=Sevryuga(Acipenser stellatus),RS=Russiansturgeon(Acipenser gueldenstaedtii))
River Species Area (m^2) Velocity (m/sec) Depth (m) Material
Substrate
depth (m)
Below dam (BD)/mid
reach (MR) Spawning (Y/N) Year built Comments References
DetroitandSt.Clair(see
Table4)
LS 39,000 0.5-0.7 5-10 Various(seeTable4;casestudy) 0.6 MR N(BelleIsle),Y(othersites,
someintermittent)
2004,2008,
2012-16
(Mannyetal.,2005),(Rosemanetal.,
2011b),(ThomasandHaas,2004)
Eastmain LS Na Na Na Na Na BD Na Na Compensationfor890m2habitat
impact
(EnvironnementIllimitéInc.,2009)
Kuban(upper) SVS 1.9ha 0.76-0.84 4-6 5-8cm,coarsesand,quarrystone 0.30 BD(80m) Y 1966 (Khoroshko&Vlasenko,1970)
Kuban(lower) SVS 1.6ha 0.88-0.94 4-5 Gravel,coarsesand,quarrystone Na BD(900m) Y-siltedafter3years 1966 (Vlasenko,1974),(Chebanov,Galich,
&Ananyev,2008),(Kerretal.,2010)
Ottawa LS Na Na Na 15-25cmrock Na BD TBD 2010/2012 RonThreader(pers.comm.)
DesPrairies LS 5,000and
8,000
1.0 1.5-3.0 20-30cm(areaencircledwith30-50cm
rockwithrowsof1mrock)
0.3 BD Y(alsoincreasedeggto
feedinglarvaesurvival)
1985,1996 13 m2/femalepreferred,sitesloped
soeffectiveatvariableflows
(Dumontetal.,2011),(LaHayeetal.,
1992)
Ouareau LS 3050 0.8-1.2(m/sec) 0.5-1.5 Sedimentaryblastrockandriverrock
(20-200mm)
0.30(min) MR(2.5km
down-stream)
N–atrestoredlocation,Y
–atnearbynaturalsite
2007,2008 Landslideaffectedqualityofnatural
spawningsite
(LaHayeandFortin,1990),(MRNF-
CARA,2011)
UpperBlackRiver LS 4locations Na Na Riprap Na BD(<2km) Na 1972 Sedimentationdecreased
effectiveness
(SmithandBaker,2005)
Saint-Maurice LS 2100 Na Na Largeboulderwith3-40cmmaterial
downstream
Na BD Y 1999 Multiplesmallsites (Faucher,1999),(Faucher&Abbott,
2001),(GDGConseilInc.,2001)
St.Lawrence
(Odensberg)
LS 36×36 Na 4.3 4-7cm 0.3 MR Y(initially) 1993 Effectivenessdecreased–siltation,
periphyton,zebramussels
(Johnsonetal.,2006b)
St.Lawrence(Iroquois) LS 2@929m20.6-0.7 10-12 5-10cm,largebouldersd/s 0.30 Aboveandbelow Y 2007 (McGrath,2009)
St.Lawrence
(Beauharnois)
LS 3000 0.46-0.98(also
intermittentlow
flowevents)
2.0-4.5 17-65mmand65mm-255mm,with1mx
5mblocksspacedat8m
0.30(min.) BD N 1998 Ineffectiveduetosiltation,
vegetation,unsuitableflow
(Gendronetal.,2002)
St.Louis LS Na Na Na 10-25cm(24%)
30-90cm(21%)
90-150cm(54%)
Na BD Yspawning,assessment
limitedtodate
2009 Steppedboulderclusters (Aadland,2010),Aadland,pers.
comm.
Volga RS ~11,000 0.5-1.0 3-4 5-10cm MR Rarely 1966 Sitetoofardownstreamofdam (Khoroshko&Vlasenko,1970)
Wolf/Fox LS >50sites Upto5m/sec Na 10-50cm Na MR Y Siltationatsomesites (Folz&Meyers,1985),(Bruch&
Binkowski,2002)
Columbia WS 1,000 Upto3m/sec Variable 2.5-30cm
(seecasestudy)
0.60 BD Unconfirmed 2011 Sitedegradedafter1year (Crossman&Hildebrand,2014)
Nechako WS 4,600 Upto2m/sec 1-3 25%2-4cm
35%4-15cm
40%15-20cm
0.30 MR Y2011 Smallrecruitmentresponse,sand
depositionat1of2sites
Author’spersonaldata,(nhc,2013b)
Rupert LS 2,060 0.2-1.8 0.6-2.1 4-40cm
(seecasestudy)
Na MR Y2010 (EnvironnementIllimitéInc.,2013)
8 
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   MCADAM et Al.
Juvenile recruitment
Monitoringrecruitmentprovidestheultimatemeasureofremediation
success(seeDumontetal.,2011)andcanbeachievedthroughannual
juvenilemonitoring.Gillnetshavetypicallybeenusedforthisapplica-
tion,althoughthe delayed vulnerabilitytogillnetcapture leads toa
muti-year lag in recruitment detection (Howell and Mclellan, 2011).
Trawlnetshavebeenalsobeenusedtodetectearlyjuveniles(Parsley
andBeckman,1994;Wanneretal.,2007),althoughtheabilitytouse
trawlnetsmaybelimitedinmanyapplications (Steffensen,Wilhelm,
Haas,&Adams,2015).
Use by non- target species
Whilethemaintargetof habitatremediationissturgeon,theeffects
(positiveornegative)onotherspeciesalsowarrantconsideration.For
example,substrateremediationmayalsobenefitfreshwatermussels
(HaagandWilliams,2014), macro invertebrates (McManamay etal.,
2013; Merz and Chan, 2005), salmonids (Jensen etal., 2009) and
otherlithophilic spawning fish (e.g., Jennings etal., 2010; Romanov
etal., 2012). The potential for responses by non-target species to
overwhelmresponsesfromtargetspecies(Pineetal.,2009)mustbe
seriouslyconsidered,and supports the need for broadermonitoring
programs. Sturgeon recovery, and particularly repatriation in highly
alteredhabitats(e.g.,Europeansturgeon;Arndtetal.,2006),isoften
includedwithinabroader suiteofecosystemremediationobjectives
(e.g.,KTOI,2009;Hondorpetal.,2014).Whilelinkingsturgeonreme-
diationtobroaderhabitatremediation can yield important benefits,
broadening recovery goals may also increase the probability of not
achievingsturgeonrestorationgoals.
1.2.2 | Physical Response
Channel structure
River channel responses to flow regulation occur over decades or
centuries (Church, 1995). Understanding long-term fluvial and geo-
morphologicalprocessesshouldbeconsideredduringprojectdesign.
Consideration of the dynamic nature of river channels is important
to ensure that remediation works are effective despite long-term
changesintheriverchannelstructure.
Hydraulic conditions
The importance of hydraulic conditions to spawning habitat selec-
tion(Du etal.,2011;Zhangetal.,2009) underscorestheneedforpre
and post-project monitoring to ensure that hydraulic conditions are
maintained or enhanced. Detailed modelling (Hildebrand etal., 2014;
McDougalletal.,2013;nhc,2008)anddirectmeasurement(e.g.,using
ADCP; Elliott, Jacobson, & DeLonay, 2004; Johnson etal., 2006a,
2006b)haveboth been used to understand hydraulicresponses.This
aspectofphysicalmonitoringisimportanttoimproveourunderstand-
ingofspawninghabitatselectionatboththeprojectdesignandmoni-
toringstages.
Substrate condition
Infillingofrestoredspawningsubstrateswithfinesedimentsisakey
concernforbothshort and long-termeffectiveness.Monitoringthe
effectsofsubstrate(e.g.,silt,sandorgravel)accumulationonremedi-
atedspawninghabitat,andinotherareas(e.g.,downstreamstretches,
bank development, impacts on navigation), is a critical monitoring
requirement.Monitoring techniques used to evaluate restored sub-
stratequalityhaveincluded videoand diverobservationsofsurficial
characteristics(Dumontetal.,2011;Rosemanetal.,2011b;Vaccaro
etal., 2016) and freeze-core sampling of riverbed materials (nhc,
2013a). Ideally, assessments should develop a broad understanding
of riverine sediment dynamics prior to remediation (e.g., sediment
budget,spatialandtemporaldepositionpatterns).
1.3 | Case studies
Sturgeonhabitat remediation studiesarenotwidely reported inthe
scientific literature; four case studies are therefore presented to
provideexamples acrosstherangeofremediation contextsandbio-
spatialscales.Theseprojectsareatvariousstagesofimplementation,
andidentifyingboth successes and limitationsshouldbenefitfuture
projects.
1.3.1 | Lake sturgeon- Rupert River
(context = mitigation, bio- spatial scale = whole
river and spawning site)
Thiscaserepresentsplannedmitigationforlakesturgeonaffectedby
newly-constructeddiversionprojectsontheRupertRiver(constructed
inconjunctionwithtwopowerhouseprojects,theEastmain-1-Aand
Sarcelle powerhouses that are part of the La Grande Hydroelectric
Complex).Changestolakesturgeonhabitatasa resultof thesepro-
jectsinclude:reducedflowinthelowerRupertRiverdownstreamof
thepartialdiversion;the creationof twodiversionbaysupstreamof
thediversionpoint (flooding ofuplandareas);and increased flowin
thediversionzoneuptotheLaGrandeRiverwatershed.
Impacts to lake sturgeon spawning habitat were addressed
throughpre-projectevaluationsofspawninghabitatrequirementsand
TABLE3 Utilizationbysturgeonoftheman-madespawning
groundatsiteKP290,RupertRiver,2011to2014
2011 2012 2014
Spawningperiod
start
30 May 25May 3June
Spawningperiod
end
6June 8June 9June
Temperature(°C): 8.9to11.2 10.7to14.6 10.2to12.3
Samplingeffort
(numberofegg
traps):
37 42 38
Eggscaptured: 6346 2366 2998
Spawners
observed
(maximum/day):
220 270 145
    
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MCADAM et Al.
baselinehabitatconditions,followedbythecompletionofmitigation
andenhancementmeasuresandassociatedeffectivenessmonitoring.
Inparticular,the mitigationandenhancementmeasures included an
in-stream flow regime,weirsand spurto maintainwaterlevels,and
theconstructionoffishpassagechannelsandspawninggrounds(com-
pleteprojectdescriptioninHydro-QuébecProduction,2004).
The in-stream flow regime for the Rupert Riverdownstream of
thediversionweirensuresthatflowsaresufficienttoallowlakestur-
geon to move between availablehabitats and provides appropriate
hydraulicconditionsatspawningsites.A2,060m2spawningground
wasconstructedin2010,downstreamofthediversionweiratsiteKP
290(riverkm290)ofthe RupertRiver(Figure1).Basedona review
of 41 studies throughout the range of lake sturgeon (including six
studiesfromtheprojectarea;EnvironnementIllimitéInc.etal.,2009,
2013a,b),thefinaldesigncriteriaforthesitewere:
• Location:adjacenttothethalweg,ideallyatthefootofamajorset
ofrapids
• Optimumvelocity:0.2to1.0m/s(range0.1to1.6m/s)
• Optimumdepth:0.5to1.0m(range0.2to4.0m)
• Spawningsubstrate:heterogeneousmixof0%-10%largeboulders
(250-400mm),20%-70%boulders (150-250mm), 25%-60% cob-
bles(80-150mm),and0%-20%pebbles(40-80mm)
The constructed spawning ground was a shoal composed of
two plateaus (6m×86m – W x L), connected bya gentle 12m
longslope (8%gradient).Aboutfortyrockislets,eachmadeupof
threeorfourlargeboulderswereplacedindifferentspotsoverthe
spawning ground to provide shelter from the current. Modelled
hydraulic conditions at the spawning ground showedthat under
expectedspringflowconditions(i.e.,theprescribedin-streamflow)
TABLE4 Characteristicsoflakesturgeon(Acipenser fulvescens)spawningsitesintheunobstructedSt.ClairandDetroitrivers(siteslisted
fromupstreamtodownstream)
Site Area (ha)
Depth
(m) Substrate Flow (m/s) Egg densitya
Duration of
use (years)
Number of
spawners
PortHuron 69.0 20-22 Cobble,gravel 2.0 Unknown 100 Thousands
HartsLight 1.54 10-12 Brokenlimestone 0.8 100s 2
Pt.AuChenes 0.61 10-12 Brokenlimestone 0.6 100s 2
MiddleChannel 0.3 7-10 Brokenlimestone 0.5 35 450
Mazlinkas 0.1 7-10 Coalcinders 0.6 50-1700 100 Hundreds
BelleIsle 0.11expandedto
1.6
5-7 Limestone,cobble
stone,coalcinders
0.7 0 0 2
ZugIsland 0.1 9-10 Coalcinders 0.6 21 1 35
FightingIsland 0.3,expandedto
0.72
5-9 Brokenlimestone,
cobble
0.7 0-330 6 35
GrassyIsle 1.62 8-10 Brokenlimestone 0.7 100s 1
aeggs/m2oneggmats.
FIGURE1 Aerialviewoflakesturgeon,
Acipenser fulvescens,developedspawning
groundatsiteKP290ofRupertRiver
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thewatershouldbe0.6to2.1mdeepandwithvelocitiesbetween
0.2and1.8m/s.
Monitoringfrom2011to2014confirmedthatthespringflowpro-
videsexcellenthydraulicconditionsinthespawningground.Hydraulic
conditionsweremeasuredin2011and2012,whenmeanflowvaried
between479and500m3/s,meandepthwasconstantat1.3m, and
meanvelocityremainedbetween0.66and0.76m/sec.Thesecondi-
tionsallmetthedesigncriteria,andtheirconsistencyreflectstheprox-
imityofmonitoringlocationstotheupstreamflowreleasestructure.
Additionally,the spawning groundhasmaintainedaconsistently
high level of physical integrity in terms of substrate cleanliness,
developedareaandstabilitysince itsconstructionin 2010 (Table3).
Utilization of the spawning ground was demonstrated by observa-
tionofadults(aerialcounts)duringthespawningperiod(dailycounts
rangedfrom7 to 220 in 2011, 2 to270in2012,and35to145in
2014).Eggmatsamplingalsoconfirmedtheuseofthesite–especially
thedownstreamportion(Table2).Theareausedbyspawningadults
correspondedtoroughly65% (1,339m2)ofthedevelopedsite area.
Annualvariation intheamountof spawning habitatusedwas antic-
ipated,becausethesitewasdesignedtoprovidesuitablespawning
habitatatarangeofflowratesandwaterlevels.
The effectiveness of the constructed spawning habitat for egg
survivalwas evaluated through drift net capture oflarvae(methods
basedonVerdonetal.,2013).Comparisonsoflarvalcapturesatfour
sites (three downstream and one upstream control) were variable,
however,theoveralltrendsuggestedthatcatcheswereeitherstable
or increased,when comparing pre- and post-project larval captures
(Figure2).Post-projectlarvalcaptureshowedastatisticallysignificant
increaseimmediately belowtheconstructed spawning site (riverkm
287-Studentt-test=3.45,p=.02).
Futuremonitoringtodemonstratejuvenilerecruitmentisplanned,
althoughcurrentlythecollectiveresultsbasedonadult,eggandlarval
monitoringalldemonstratethat thein-streamflowregimeand man-
made spawning grounds at site KP 290 have effectively preserved
available lake sturgeon spawning habitat. Stable flow for 45days
during the spring period may be particularly important due to an
expectedincreaseineggsurvivalrelativetonaturalconditions,when
eggmortalitymayoccurasaresultofdecreasedwaterlevels.
1.3.2 | White Sturgeon- Columbia and Nechako rivers
(context = rejuvenation, bio- spatial scale = spawning
reach, spawning site)
WhitesturgeonpopulationsintheupperColumbiaandtheNechako
rivers are legally listed as endangered, yet persistent recruitment
failure was not recognized for more than 20years in either case
(DFO,2014;Hildebrandetal.,2016).Riverregulationandindustrial
usehaveled to altered flow regimesandhabitatdegradationover
several decades, thus targeted restoration is required to prevent
extirpation.Spawninghas been identified annuallyinbothpopula-
tions over the past decade, although at differing spatial scales. In
the Upper Columbia River, spawning occurs at multiple locations
(HowellandMcLellan,2007;Golder,2008;Terraquatic(Terraquatic
ResourceManagement),2011;AMEC,2014;BCHydro,2015).Most
spawning sites occur within a 75km stretch of river, with several
immediatelydownstreamofhydroelectric facilities.IntheNechako
watershed, only one spawning site has been identified in a 4km
stretch of river (~140km downstream of Kenney Dam), where
decreased riverbed slope led to the historical presence of gravel
bars(nowlargelywithvegetationundertheregulatedflowregime).
Spawning has been detected throughout the reach, with activity
concentratedinfourareasthatshowlocallyelevatedwatervelocity
(McAdametal.,2005;Triton,2009).Althoughthehistoricalspawn-
ing locations are unknown, hydraulic modelling (nhc (Northwest
HydraulicsConsultants),2008)suggeststhat sturgeon spawned at
asinglesiteattheupstreamendofthepresentspawningreach.For
boththeColumbiaRiverandNechakoriverstheannualpresenceof
wildspawners, coupled withtheabilityto implement experimental
FIGURE2 Estimateddriftinglarvae
abundanceatRupertRiversitesKP
212,276,287(downstream)and361
(upstream)inspring2007to2012and
2014(pre-project=2007to2009,post-
project=2010to2014)
    
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MCADAM et Al.
releasesofearlylifestages(e.g., eggsand larvae),makethesesites
idealsettingstotestthefeasibilityofspawninghabitatremediation
anddeterminetheefficacyofdifferenthabitatremediationoptions.
Retrospectiveevaluationslinking recruitmentfailuretosubstrate
changesinwhitesturgeonspawninghabitat(McAdam,2015;McAdam
etal., 2005) provide a strong foundation for pursuing substrate
FIGURE3 MapofRevelstokeReachof
UpperColumbiaRivershowinglocationof
whitesturgeon,Acipenser transmontanus,
spawningandearlyrearinghabitat
restorationin2012.Sitedimensionsfor
controlandmodifiedsitesare10m×100
m.FigurereproducedfromCrossmanand
Hildebrand(2014)
FIGURE4 Numberoflarvalwhite
sturgeonA. transmontanuscollected
downstreamofcontrolandmodifiedsites
(histogram)andhourlymeandischarge
foreachtimeinterval(points,line).Figure
reproducedfromCrossmanandHildebrand
(2014)
12 
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   MCADAM et Al.
restorationasameansofpopulationrecoveryinbothrivers.Although
bottomvelocitiesatknownspawninglocationsarewithinthesuitable
range (>1.0m/s; Parsley etal., 1993), substrate surveys at several
spawningareasshowthathighqualityhabitatislimitedtoasmallpro-
portionofsurveyedsites(e.g.,3%-12%intheUpperColumbiaRiver;
nhc, 2012; Golder, 2013). Field studies in both rivers also demon-
stratethatlarvalcatchisdominatedbyyoungyolk-saclarvae(Golder,
2009;Terraquatic(TerraquaticResourceManagement),2011)atmost
spawningsites,whichisalsoindicativeofadiminishedqualityoflarval
hidinghabitat.Accordingly,habitat requirements of earlylife stages
(particularlyyolk-saclarvae)areusedastheprimarybasisfordesigning
spawninghabitatremediationworksthat areacriticalcomponentof
thefederalrecoverystrategyforbothpopulations(DFO,2014).
Experimentalspawninghabitatremediationhasbeentestedatone
siteintheUpperColumbiaRiver(Figure3).Remediationfocusedona
smallareaofknowneggdeposition(1km2)andthespawningsubstrate
wasmodifiedwithacombinationoflargerbouldersand coursegravel
(90% > 200-300mm diameter, 10% > 25-80mm diameter), both of
whichwereangularinshapetoprovidemoreinterstitialspacewhenset-
tled.Thespawninghabitatwaslocatedbelowtheminimumwaterlevel
to avoid dewatering eggs orlarvae (Golder, 2011). The effectiveness
oftherestoredhabitatwastested bystockingyolk-sac larvae(~1day
posthatch)overbothmodifiedandcontrolsites(inclusionofacontrol
siteis notable, assuitablecontrolsareoftenlimited forsuchstudies).
Monitoring demonstrated that larvae released over substrates with
increasedinterstitialspaceshowedagreatertendencytohide,remained
inthesubstrateregardlessoftheflowconditions,anddisperseddown-
streamvolitionally(Crossman&Hildebrand,2014)(Figure4).Although
habitatconditionswereimproved,themodifiedspawninghabitatdete-
rioratedrapidlywithintwoyears(J.Crossman,BCHydro,unpublished
data).Thehighlyvariableflowregimeinthestudyarearesultedinthe
downstream displacement of restored substrate, demonstrating the
importanceofathoroughevaluationofsite-specifichydraulicsonsub-
strateretentionandmaintenancepriortoconstruction.
Experimental spawning habitat restoration in the Nechako River
consisted of placing 2,100m3 of clean substrate on the riverbedat
twosites(Figure5)priortothe2011spawningseason.Themixture
oflargeandsmallmaterials(seeTable2)wasdesignedtoachieveboth
physicalstabilityandabiologicalfunction(i.e.,interstitialhabitatsuit-
ableforyolk-sac larvae). While larval captures werelimited in 2011,
thedetectionofwildoriginrecruitsfromthe2011year-class (n=24;
fivetimes higherthanotheryear-classesidentifiedin the2013-2016
juvenilesampling)providesevidenceofapositiveresponsetosubstrate
remediation (S. McAdam, unpublished data).The limited recruitment
responsemightbedue totherapid decreasein thehabitatqualityof
enhancedsubstratescausedbyaninflux ofsand overthemajorityof
onegravelbed (lower pad-nhc(NorthwestHydraulics Consultants),
2012).Hydraulicconditions appear to be limiting or delaying further
infillingandmonitoringhasconfirmedthemaintenanceofbiologically-
functional substrate conditions at the upper pad in both 2012 and
2013 (Northwest Hydraulics Consultants, 2013b, nhc (Northwest
HydraulicsConsultants,2013a).Physicalsubstratecleaningwasinves-
tigatedin2016as arapid,althoughtemporary,remediationmeasure.
Whilesubstratecleaningwaseffective,itis tooearlytoevaluatebio-
logicalresponses(nhc,2016).
Experimental approaches in both riversdemonstrate the poten-
tialefficacyofsubstrateremediation.Furtherresearchregardingthe
geomorphology,substrate conditions,andhydraulicproperties ofall
spawningsitesisrequiredtodesignremediationprojectsthatmaintain
theireffectivenessoverthelongterm.
1.3.3 | Lake Sturgeon – Detroit and St. Clair rivers
(context = re- creation, spatial scale = multiple
spawning sites)
The Detroit and St. Clair rivers comprise an unobstructed, 160-
km channel between two very large lakes (Figure6) that has been
highly altered and degraded by urban development (Edsall, Manny,
&Raphael,1988;Manny etal., 1988). Since 1900, the construction
ofmorethan145kmofshippingchannelsledtotheremovalofmore
than 46 million cubic meters of rock-rubble from the Detroit River
(Bennion&Manny,2011)andsimilaramountsfromtheSt.ClairRiver.
Theextentofthehistoricalhabitatdestruction,includingelimination
ofsturgeonspawninghabitat,createduniquechallengesleadingtothe
needtore-createhistoricalhabitats(Mannyetal.,2005).Remediation
ofspawninghabitatfornative fishes,includinglakesturgeon,isnow
aninternationalgoalintheserivers.
By 1925, habitat alteration and over-harvest reduced lake stur-
geoninbothriverstolessthan1%oftheirformerabundance(Caswell,
Peterson,Manny,&Kennedy,2004;MannyandMohr,2011).Recent
estimatesindicatethat45,500lakesturgeonsoccupythesetworivers,
comparedto anestimatedhistorical populationof100,000 (Thomas
FIGURE5 Aerialphotoshowingwhite
sturgeon,A. transmontanus,spawningreach
ofNechakoRiverlocatednearDistrictof
Vanderhoof.Substrateremediationwas
conductedatupper(upstream)andlower
(downstreamnearbridge)padsin2011
500 m
N
Lower Pad
Upper Pad
Flow
    
|
 13
MCADAM et Al.
andHaas, 2002).Historicalreportsandinterviewswithretiredcom-
mercial fishermen (Goodyear, Edsall, Dempsey, Moss, & Polanski,
1982)identifiedninepossiblehistorical lakesturgeonspawningsites
intheDetroitRiver.
The largest and highest quality lake sturgeon spawning site is
locatedat theheadoftheStClairRiver,nearPortHuron,Michigan.
Thisareaischaracterizedbyfastflowandroundedcobbleandcoarse
gravelsubstrates,andwastoodeeptobeaffectedbyshippingchannel
construction(Boase&Hill,2002).Spawningisalsoregularlydetected
attwoadditionalareaswherecoalcinderswerehistoricallydumped;
MazlinkasreefintheSt.ClairRiver(Nicholsetal.,2003)andZugIsland
intheDetroitRiver(Caswelletal.,2004).Itisunclearwhetherthese
twositeswereusedbyspawning lakesturgeonpriortothe coalcin-
derdumping,orwhethertheadditionofthecoalcinderscreatednew
spawningsites.
Following an adaptive strategy, six spawning reefs have been
constructedintheSt.Clair–Detroitriverssince2004(Mannyetal.,
2015;Vaccaroetal.,2016).Forallreefconstructionprojects,theuse
ofgravellessthan5cmindiameterwasavoidedduringreefconstruc-
tion,owingtoitspotentialusebyspawningsealamprey(Petromyzon
marinus) (Wigley, 1959) that are controlled throughout the Great
Lakes.In the DetroitRiverat BelleIsle,an 0.11ha reefwascreated
in2004(DetroitRiver-totalreef size0.11ha;Manny,2006a).This
previouslyunusedsitewaschosenbecauseofitslocationin therel-
ativelyunpollutedheadwatersoftheDetroitRiverandthepresence
ofsuitablewatervelocity[e.g.,0.37-0.80m/sbasedonLaHayeetal.,
(1992)].Siteselectionwasbasedonahydrodynamicgeospatialmodel
usedtolocatedeep,fast-flowingareas(Bennion&Manny,2014).The
selection of substrates was based on the previous identification of
largebrokenlimestone(Bruch& Binkowski,2002),rounded igneous
rock(Mannyetal.,2005),and coalcinders (Thomasand Haas,1999,
2002)assuitablesubstrates(seeTables2and4).
In2008,asecondspawningreefwasconstructedatNortheast
Fighting Island (Detroit River), which was reputedly a historical
spawning ground (Goodyearetal., 1982). Substrates used at this
sitewereamixtureof10-50cmbrokenlimestone,5-10cmbroken
limestone, and 10-20cm rounded igneous rock. The initial 0.3ha
spawningreefwasexpandedin2013toatotalof0.72ha.Thisloca-
tionwas selectedbasedonthe presenceofhighwatervelocity(>
0.5m/s),year-roundaccessibilitybyadultsturgeon,atemperature
of11-16°Cduringthespawningperiod(Bruch&Binkowski,2002),
and a waterdepth of 9-12m (Roseman etal., 2011b).In 2012, a
thirdreefcomplex was constructed in the Middle Channel ofthe
lower St. Clair River, using 10-20cm broken limestone and 10-
15cmrounded,igneousstone.AMiddleChannelreefwasalsocon-
structedacrosstheentirechannel.TworeefswereplacedintheSt.
ClairRiverduring2014atHartsLight(1.54ha)inthemainchannel,
andatPt.AuChenes(0.61ha)intheuppernorthchanneloftheriver
(Figure6).Thesereefswereconstructedofonelargesectionof10-
20cmfracturedlimestoneorientedparalleltothecurrent,alongthe
edgeoftheriverchannelontheMichiganshore.In2015,1.62haof
spawningreefwasplacedinthemainchanneloftheDetroitRiverat
GrassyIsland,usingsimilarstoneandfollowingthesameorientation
atHartsandPt.AuChenesintheStClairRiver.Lastly,intheautumn
of2016,the2004BelleIslereefwasexpandedto0.5haofcontig-
uous10-20cmlimestone,andtwoadditionalreefs(0.4and0.7ha)
wereplacedupstreamofBelleIsleintheDetroitRiver(Figure6).
Assessmentswith various gear types indicate that all sturgeon
age classes are present in the Detroit and St. Clair rivers (Boase
etal.,2014), however,spawning habitat utilizationisnotuniform.
Spawningbylake sturgeon has been confirmedatfiveofsix con-
structedspawningsites(notthe2004BelleIsle;Table4).Additionally,
eggs and larvae werenot collected in all years that sampling was
conducted (Roseman etal., 2011b; Thomas and Haas, 2004). For
FIGURE6 Mapofunobstructed
Huron-Eriecorridor(St.ClairRiver/LakeSt.
Clair/DetroitRiver)showinglocationsof
ninenaturally-occurring,orrestored,lake
sturgeon,A. fulvescens,spawningsites
14 
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   MCADAM et Al.
example,sturgeoneggs werecollectedonly once (in 2001)atZug
Island (Caswell etal., 2004) until samplingwas discontinued after
2008(duetorepeatedgearloss).Sturgeoneggsandlarvaewerecol-
lectedatFightingIslandin2009,2011,2012,2014,2015,and2016
butnotin2010or2013.Nosturgeoneggsorlarvaehavebeencol-
lectedattheBelleIslereefsinceitwasconstructedin2004,despite
repeated annual samplings from 2004 to 2014 (Hondorp etal.,
2014,Manny2006b).Eggswerecollectedonallotherconstructed
reefsforatleasttwoyearsfollowingconstruction.Theseresultssug-
gestlimitedorintermittentusebyspawningsturgeonofconstructed
spawning habitat. Captures oflake sturgeon yolk-sac stage larvae
(Bouckaert,Auer,Roseman,& Boase,2014)alsosuggest that sub-
stratesatsomesitesintheDetroitRivermaynotberetainingearly
larvalstageslongenoughforexogenousfeedingto begin,possibly
duetoexcessivelylargeinterstitialspaces(seeHastingsetal.,2013;
McAdam,2011).
Thephysicalconditions ofconstructedspawning reefs intheSt.
ClairandDetroitrivers(Table4)havebeenassessedusingdiversand
underwatercameras(Manny,2006b;Rosemanetal., 2011b).Within
twoyearspostconstruction,morethanhalfoftheareaofthespawn-
ing reefs at Fighting Island and the entirety of the Middle Channel
reefhavefilledinwithsandandsilt,resultinginembeddedspawning
substrates.Althoughsomeinfillingwasexpected,factorsaffectingthe
magnitudeand location ofinfilling arepoorlyunderstood. Beginning
in 2014, an AcousticDoppler Current Profiler,side-scan sonar, and
sedimenttransport modelshavebeenemployedtoassesscandidate
reefsitespriortoconstruction andavoiddepositionalareas(Fischer,
Bennion,Roseman,&Manny,2015;Kinzeletal.,2016;Vaccaroetal.,
2016). These technologies arealso used to monitor reef conditions
and performance following construction.Continued monitoring and
assessmentisconsideredcriticaltounderstandinglong-termchanges
tophysicalsubstrateconditions.
Theneed fora longterm,comprehensive,monitoring programis
oneof thekeylessonslearnedfromvariouslakesturgeonspawning
habitatremediationprojectsintheDetroitandSt.Clairrivers(Manny
etal.,2015;Vaccaroetal.,2016).Thisneedisbasedonthepotential
forlongerterm,physical changesinthe restoredsturgeonspawning
habitat, and the attendant biological effects.The optimum number,
location,andsizeofrestoredsturgeonspawningsitesarealsoimport-
antconsiderations, particularlywhenpresent and historicalusepro-
videslimitedguidance(Mannyetal.,2015).
1.3.4 | Baltic Sturgeon – Odra River
(context = repatriation; bio- spatial scale = whole river)
Remediationof theBalticsturgeon intheOdraRiverrepresents the
mostcomplicatedremediationcontext,sinceitrequirestherepatria-
tiontohabitatsfromwhichsturgeonhavebeenextirpated.Extensive
habitatchangesinrecipientwatersheds also create numerous chal-
lenges for identifying, and restoring suitable habitats. For example,
proposedspawninghabitatremediationsitesmustbeselectedonthe
basisofexpected,ratherthanconfirmed,spawninghabitats(Gessner,
Arndt,Tiedemann,Bartel,&Kirschbaum,2006).
ReleasesofA. oxyrinchusbeganin2006,and1750000individuals
of all age classes (feedinglarvae to subadults of 1.5m length) have
beenreleasedasof2016.However,basedonmaturationratesofcap-
tivebroodstockandsurvivalrateestimatesfromearlyreleases(Jaric
and Gessner, 2013; McManamay, Orth, & Dolloff, 2013) returning
spawnersarenotexpectedtobeobservedpriorto2020.Verification
of spawning habitat use will therefore not be possible prior to this
date.Despitethislimitation,conceptualplanstoimprovetheavailabil-
ityofadult spawningandstaginghabitatandthequalityofearlylife
phasehabitatsare being developedonthebasisofa ProjectGroup
under the Helsinki Commissionfor the Baltic range states (Gessner
etal.,2011).
In the absence of spawning adults, prospective spawning sites
wereidentified byevaluatinghabitatsinthevicinity ofapparent his-
toric spawning reaches identified from historical catches (Grabda,
1968;Przybyl,1976).Habitatsuitabilityin thevicinityofthese areas
wasevaluatedusingwell-establishedcharacteristicsofspawningsites
(e.g.,depth,velocity,andsubstrate).Substratequalitywasdetermined
bymappinglongitudinalsectionsoftheriverwithtransectsat select
locationstodeterminethedimensions ofsubstrateaggregations,and
by underwatervideo image analysis (Arndt, Gessner, & Raymakers,
2002).
Fourpotentialspawningsitesgreaterthan1000m2were identi-
fiedin the Odra catchment.All sites werein the vicinityofhistoric
aggregationareas, mainly areaswitherosionanddepositionofsub-
strateinareasofpostglacialmorainedeposits.Anthropogenichabitat
alterationsthroughdamming,riverchannel modifications[e.g.,chan-
nel straightening to increase water conveyance and surface water
removal,incombinationwithgroynefields tostabilizethe riverbed,
ledtothelossofapproximately70%ofthehistoricalhabitat(Grabda,
1968)]. Modelling of habitat availability, assuming 25,000eggs/m2
andthat10%ofhistoricalhabitatsremainsuitable,suggestsapresent
eggproductioncapacityof14millioneggs.However,themobilityof
riversubstrates(mostlycomprisingfineand smallgravel0.1–6mm
grainsize)meansthatpotentiallysuitablesubstratesmayshowlimited
functionalityfortheearly rearingofeggsandyolk-saclarvaedue to
fillingwithfinesubstrate(Arndtetal.,2006).
Themainobstaclesforeffectiveremediationofhabitatstillpersist
(i.e.,navigation andfloodcontrol)andlimittheoptions forimprove-
mentstobankerosion,depthheterogeneityandsedimentdeposition.
Currently the increased bank stability resulting from groynes and
riprap leads to increased in-channel erosion and increased bedload
transport.Thishasdecreasedriverbedelevationtothe extentthatit
isbelowthealluvialdepositionlayersforgravelandrock,whichlim-
itsthe capacityforthe naturalregenerationofspawningsites. River
channelization also prevents the establishment ofa stable riverbed
that provides sufficient habitat forbottom fauna, including juvenile
sturgeonduringdownstreammigrations.Thisleadstoextremelyhigh
migration speeds in sections of the riverwith the highest bedload
transport(Fredrich,Kapusta,Ebert,Duda,&Gessner,2008).
Difficultieswithremediationofmainstemsitessuggesttheneedto
consideralternatives,includingremediationofspawningsitesinmajor
tributariesoftheOdraRiver(e.g., Warta,Notec,Prosna, and Drawa
    
|
 15
MCADAM et Al.
rivers)andpossiblythedevelopmentofsmallerscalemainstemreme-
diationareasthatallowlimitedreproductionatanysinglesite.Ifsmaller
habitatpatchesareusedtheywillneedtobealignedwithrivercurrents
andbesufficientlylong(andstable)toallowdriftingyolk-saclarvaeto
findsheltersuccessfully.Approximationsbaseduponbehaviourexper-
iments(Gessneretal.,2009)suggesttheneedfor30mofcontinuous
habitat,assumingamoderatedriftdurationof15secat0.8m/sec.In
caseoflongerdrifts,multiplesiteswouldclearlybebeneficial,which
isinlinewiththecurrenttargetsthatsuggestlowlandriversshouldbe
comprisedofroughlyabout10%ofcoarse sediment (i.e.,graveland
cobble)by area(Dahmetal., 2014). Thehabitatavailabilityforfeed-
inglarvaeislargelyunknown;thepresenceoffeedinglarvaefollowing
releasehasnotbeensuccessfullyproven.However,the presence of
multipleremediationsitesmayprovide habitat that supports rearing
by feeding larvae.It is hypothesized that groyne fields also provide
productivehabitatwithsuitablesubstrateforfeedinglarvae,although
verificationofutilizationiscurrentlylacking.
Theneedto restore alllifestagesof sturgeonintheOdraRiver
(andotherareasoftheirhistoricalrangeinEurope)createssubstantial
challengesduetotheneedtorestoreallelementsofsuitablehabitat
fordifferentlifephases(i.e.,reachselection,localscalehydraulicand
substrateconditions).Monitoring of the initial repatriationsintothe
OdraRiverprovidecriticalguidanceforsubsequentefforts.Asnoted
above,successfulspawningofrestockedfish willonlybe detectable
after 2020. However, monitoring of particular life stages (e.g., lar-
val out-planting experiments and lab-based research) may provide
interim indications of habitat improvements. Conducting additional
trialsin differentriversorriversectionswouldprovidetheopportu-
nitytocompareresponsestodifferenthabitatremediationstructures
designedforvariouslifestageswhiledevelopingsolutionsthatdonot
interferewithnavigationtargets.
2 | CONCLUSIONS
Ourreview ofsturgeonhabitat remediationidentifiedthatmultiple
contextsandbio-spatialscalesmustbeconsideredforeffectivestur-
geonhabitatremediation.Thedireglobalconservationstatusofstur-
geonclearlyindicatespastfailurestorecognizeandlimittheimpacts
ofanthropogenicchangestoriverine habitats that affect sturgeon.
Whileour review identifiedpositiveprogressin the remediationof
spawning and early rearing habitats, most sturgeon habitat reme-
diationisstillnotabletoaddressconservationconcernseffectively.
Current projects addressing lake sturgeon, Acipenser fulvescens,
appeartoshowthemostpromise.Furtherappliedresearchisneeded
toidentify remediationmeasuresthat provideconsistentlong-term
effectiveness.Untilsuchmeasuresareidentified,westresstheneed
tomaintainconnectivityandtheabilityforlong-distancemigration,as
wellasthehabitatmosaicrequiredforsuccessfulrecruitment.Most
remediationprojectstodatehave beenconductedatthesub-reach
scaleand havefocussedonsubstrate remediationtoimprove early
life stage rearing in spawning habitats. The mixed success of past
projectssuggeststhat a ‘build it and they will come’ approach has
notbeen sufficiently successful. We have identified threeareasin
particularwhereinvestigationwillbenefitfuturerestorationefforts:
1) Mechanisticinsightinto factors affecting spawningsiteselection,
including hydraulic conditions and fine-scale habitat specificity
(see Duong etal., 2011).
2) Utilizationofhydro-geomorphologicalprocess(e.g.,reachscale)to
identifyameanstolimit the incursion of fine substrates into re-
storedspawninghabitatsandtocleansubstratesatspawningsites.
Utilizingariver’sownpowerismoredesirablethanrepeatedphysi-
calcleaning(Johnsonetal.,2006b).
3) Therole of habitat effects during earlylife history (e.g., survival,
larvaldrift,firstfeeding)andearlyjuvenilephases.Amorenuanced
understanding of habitat mediated effects would address such
questionsas:(i)domultiplefactorsaffectlarvaldriftdecisions(e.g.,
ontogeny,foodavailability,thepresenceofpredators,thecharac-
teristicsofinterstitialhabitat);and(ii)whataretheshortandlong
term consequences of phenotypic responses to early life stage
habitatconditions(Boucheretal.,2014;Duetal.,2014;Johnsson
etal.,2014;Johnssonetal.,2014).
Bothgeomorphologicalandbiologicalstudieswillnecessarilyrequire
acombinationoflaboratory,modelled,andfieldstudies.Boththeurgent
needforremediationandeconomiccostsoflarge-scaleremediationem-
phasizethevalueofinformationexchangeamongrecoveryprogramsfor
varioussturgeonspecies.
ACKNOWLEDGEMENTS
Thisworkoriginatedfromaworkshopheldduringthe7thInternational
SturgeonSymposium(Nanaimo,BC),andwethank theorganizersof
thateventforprovidingtheopportunitytocollaborateinsupportof
sturgeonconservation.Theauthorswouldliketo thankEdRoseman
forhiscontributionsandthetwoanonymous reviewerswhosecom-
mentsimprovedthemanuscript.
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How to cite this article:McAdamSO,CrossmanJA,
WilliamsonC,etal.Ifyoubuildit,willtheycome?Spawning
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1–21. https://doi.org/10.1111/jai.13566
... Creating artificial spawning sites or expanding existing spawning grounds is a common strategy that has been used for lake sturgeon recovery (Roseman et al., 2011;Thiem et al., 2013;Fischer et al., 2018, McAdam et al., 2018. However, lake sturgeon habitat restoration has proved to be a major challenge with mixed levels of success Roseman et al., 2011;Fischer et al., 2018) and failure (Baril et al., 2019). ...
... Although there is not sufficient information to clearly identify key success and failure factors of restored and newly created spawning sites in the LSLR, a few general observations can be made. The expansion of existing spawning grounds with appropriate substrate (see McAdam et al., 2018) can significantly improve lake sturgeon reproductive success when problems related to egg overcrowding or poorquality substrate are encountered. In fact, after expansion of the Des Prairies River (RDP) spawning ground, a strong increase in larval production was observed, even though high-quality spawning habitats were already available . ...
... Sites to be developed must also exhibit conditions conducive to spawning (i.e., flow velocities and depth conditions; see Baril et al., 2018, andMcAdam et al., 2018), as well as areas in which substrate size and quality can be increased to allow egg and embryo retention Fischer et al., 2018). Prior knowledge of long-term fluvial and geomorphological processes, hydraulic conditions (McAdam et al., 2018), and spawners' movements in relation to water flow is also a definite asset . ...
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Knowledge concerning critical habitats such as spawning sites is crucial to the preservation of vulnerable fish species like sturgeons. For lake sturgeon Acipenser fulvescens populations in the Lower St. Lawrence and Ottawa river systems, knowledge about spawning sites has been documented primarily in the grey literature, unpublished reports, or notes, with very little published in peer-reviewed literature. Here, we reviewed over 100 reports, articles, and unpublished observations in the Lower St. Lawrence and Ottawa river systems to synthesize available information concerning the location of lake sturgeon spawning sites, the level of spawning activity, and the methodologies used for assessments. In this review, 38 lake sturgeon spawning sites were identified. Of these sites, 11 were enhanced or artificially created for lake sturgeon. In the Lower St. Lawrence River, 68% of known spawning sites were located downstream from a dam compared to 47% in the Ottawa River. The use of the two artificially created spawning sites in the Lower St. Lawrence River has not yet been confirmed, while one site established in the Ottawa River has had confirmed spawning activity, although the spawning run size is unknown. In contrast, spawning has been confirmed for the seven natural spawning sites that have been artificially expanded in these systems, and two of these sites have large spawning runs. Information revealed by this review suggests that lake sturgeon populations in these large river systems rely on multiple spawning sites and that expanding natural spawning grounds may be more effective than creating new ones.
... These observations concur with others in that the offshore spawning habitat below De Pere Dam is not used extensively by spawning adults; Lake Sturgeon in the LFR tend to congregate and spawn along or near the eastern shoreline of the river (Elliott & Gunderman, 2008). Locations of egg deposition confirmed during this study were associated with cobble and cobble/boulder substrates, consistent with other regional studies (Bruch & Binkowski, 2002;McAdam et al., 2018;Peterson et al., 2007;Roseman et al., 2011), and located near a visible hydraulic edge along the shore created by the operation of dam tainter gates. ...
... In the LFR in 2019, for example, the majority of females spawned in a localized shoreline section representing only 27% of the nearshore cobble spawning habitat. While this concentrated spawning effort may be beneficial in some ways such as increased egg fertilization or increasing individual mating opportunities, it may also lead to excessive egg overcrowding which has been shown to increase the probability of egg mortality (Khoroshko & Vlasenko, 1970;McAdam et al., 2005;Dumont et al., 2011;White Sturgeon, Crossman & Hildebrand, 2014;Fischer et al., 2018;McAdam et al., 2018;Pallid Sturgeon & Shovelnose Sturgeon, Chojnacki et al., 2020). The narrow swath of spawning habitat along the LFR eastern shoreline (in the upstream/downstream direction) also limits the probability that downstream drifting eggs will settle in areas suitable for incubation (Finley et al., 2018). ...
... Future studies focused on desiccation-related egg mortality in relation to temporal changes in water levels are needed to determine the magnitude of post-spawn mortality, as data from the present study indicate this could be a significant ongoing factor in Lake Sturgeon reproduction in the LFR. Furthermore, egg mortality also may be driven by rapid algae colonization on nearshore substrates (Klump et al., 1997) that suffocate eggs and negatively influence adhesive properties (Folz & Meyers, 1985;Gulf Sturgeon, Sulak & Clugston, 1998;Johnson et al., 2006;McAdam et al., 2018). Lake Sturgeon egg predation is a natural phenomenon (Caroffino et al., 2010;Forsythe et al., 2013; see also Waraniak et al., 2018) and is known to increase with increasing predator density. ...
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The Lower Fox River is a modified tributary of Green Bay, Lake Michigan that hosts a remnant Lake Sturgeon (Acipenser fulvescens) population. Reproduction has been confirmed, although annual spawning events have been described as small and concerns regarding the long‐term viability of the population remain. Contemporary and comprehensive surveys of spawning habitat, spawning stock, and production to the larval stage have not been conducted. The goal of this study was to describe spawning habitat, determine the size and demographic structure of the spawning stock, and quantify larval production (2017–2019) to identify impediments to population growth and recovery. Over 130 adults were present during annual spawning runs and spawning activity was consistently concentrated along the eastern riverbank. Adequate population structure exists to support reproductive success, but larval catch was low, ranging from 0 to 14 larvae captured annually. Evaluation of the riverbed below the De Pere Dam suggests the extent of the substrate available for spawning adult Lake Sturgeon is lower (~70% less) than previously described. Habitat deemed suitable for spawning exists offshore below the dam, but most habitat used for spawning is arranged along the eastern man‐made shoreline. However, nearshore spawning is problematic at this location due to fluctuating discharge from dam operation and periodic seiche events. Possible impediments limiting the success of Lake Sturgeon reproduction include dewatering of eggs, retention of eggs and larvae, algae colonization, and egg predation. We discuss these issues in the context of previous Lake Sturgeon research, future monitoring of spawning adults/larval production, and the likelihood that river habitat improvement will foster increased reproductive success.
... In short, the complexity of restoring the remaining sturgeon habitat in the Ural River to a condition that will sustain natural populations should not be underestimated [103][104][105]. The global climatic changes that are driving up temperatures in the basin and altering flows are enormously difficult to counteract, and steps to prevent pollution from entering the river would be costly. ...
... The overall challenge is compounded in the Ural River, which hosts multiple sturgeon species, each with its own needs and preferences. These factors are crucial for determining the scale of habitat restoration, the steps needed to maintain the habitat, and the monitoring process necessary to evaluate the success of restoration efforts [103,107]. ...
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... In terms of positive density dependence (i.e., overcoming Allee effects or depensation; Courchamp et al., 1999), enhancement efforts must focus on areas that will be utilized by enough individuals for an ecological process to be completed. For example, with regards to lake sturgeon spawning habitats, McAdam et al. (2018) asked the question "If you build it, will they come?" and discovered that spawning had not been documented in nearly half of the restored spawning sites that were assessed (Fischer et al., 2018;McAdam et al., 2018). Additional knowledge of the movement ecology of these fish can be used to inform restoration site selection (Brooks et al., 2017), thereby reframing the question as a management strategy: "they come, so let's build". ...
... In terms of positive density dependence (i.e., overcoming Allee effects or depensation; Courchamp et al., 1999), enhancement efforts must focus on areas that will be utilized by enough individuals for an ecological process to be completed. For example, with regards to lake sturgeon spawning habitats, McAdam et al. (2018) asked the question "If you build it, will they come?" and discovered that spawning had not been documented in nearly half of the restored spawning sites that were assessed (Fischer et al., 2018;McAdam et al., 2018). Additional knowledge of the movement ecology of these fish can be used to inform restoration site selection (Brooks et al., 2017), thereby reframing the question as a management strategy: "they come, so let's build". ...
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Rehabilitation of large Anthropocene rivers requires engagement of diverse stakeholders across a broad range of sociopolitical boundaries. Competing objectives often constrain options for ecological restoration of large rivers whereas fewer competing objectives may exist in a subset of tributaries. Further, tributaries contribute toward building a “portfolio” of river ecosystem assets through physical and biological processes that may present opportunities to enhance the resilience of large river fishes. Our goal is to review roles of tributaries in enhancing mainstem large river fish populations. We present case histories from two greatly altered and distinct large-river tributary systems that highlight how tributaries contribute four portfolio assets to support large-river fish populations: 1) habitat diversity, 2) connectivity, 3) ecological asynchrony, and 4) density-dependent processes. Finally, we identify future research directions to advance our understanding of tributary roles and inform conservation actions. In the Missouri River United States, we focus on conservation efforts for the state endangered lake sturgeon, which inhabits large rivers and tributaries in the Midwest and Eastern United States. In the Colorado River, Grand Canyon United States, we focus on conservation efforts for recovery of the federally threatened humpback chub. In the Missouri River, habitat diversity focused on physical habitats such as substrate for reproduction, and deep-water habitats for refuge, whereas augmenting habitat diversity for Colorado River fishes focused on managing populations in tributaries with minimally impaired thermal and flow regimes. Connectivity enhancements in the Missouri River focused on increasing habitat accessibility that may require removal of physical structures like low-head dams; whereas in the Colorado River, the lack of connectivity may benefit native fishes as the disconnection provides refuge from non-native fish predation. Hydrologic variability among tributaries was present in both systems, likely underscoring ecological asynchrony. These case studies also described density dependent processes that could influence success of restoration actions. Although actions to restore populations varied by river system, these examples show that these four portfolio assets can help guide restoration activities across a diverse range of mainstem rivers and their tributaries. Using these assets as a guide, we suggest these can be transferable to other large river-tributary systems.
... Currently, substrate augmentation via gravel additions is a viable management strategy for salmonid spawning habitat, but such methods have not been investigated for sturgeon in the Sacramento river (Stillwater Sciences 2007). For a range of other sturgeon species, the biggest barrier to effective long-term substrate augmentation is infilling by fine sediments over time, emphasizing the need to collaborate with fluvial geomorphologists to select sites with the appropriate flows and depths for remediation (McAdam et al. 2018). To date, there is a lack of information on egg-to-larva survival, juvenile recruitment, and mortality estimates for all life stages. ...
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Southern Distinct Population Segment (sDPS) green sturgeon spawn solely in one stretch of the Sacramento River in California. Management of this spawning habitat is complicated by cold water temperature requirements for the conservation of winter-run Chinook salmon. This study assessed whether low incubation and rearing temperatures resulted in carryover effects across embryo to early juvenile life stages on scaling relationships in growth and metabolism in northern DPS green sturgeon used as a proxy for sDPS green sturgeon. Fish were incubated and reared at 11 °C and 15 °C, with a subset experiencing a reciprocal temperature transfer post-hatch, to assess recovery from cold incubation or to simulate a cold-water dam release which would chill rearing larvae. Growth and metabolic rate of embryos and larvae were measured to 118 days post hatch. Reciprocal temperature transfers revealed a greater effect of low temperature exposure during larval rearing rather than during egg incubation. While 11 °C eggs hatched at a smaller length, log-transformed length–weight relationships showed that these differences in developmental trajectory dissipated as individuals achieved juvenile morphology. However, considerable size-at-age differences persisted between rearing temperatures, with 15 °C fish requiring 60 days post-hatch to achieve 1 g in mass, whereas 11 °C fish required 120 days to achieve 1 g, resulting in fish of the same age at the completion of the experiment with a ca. 37-fold difference in weight. Consequently, our study suggests that cold rearing temperatures have far more consequential downstream effects than cold embryo incubation temperatures. Growth delays from 11 °C rearing temperatures would greatly increase the period of vulnerability to predation in larval green sturgeon. The scaling relationship between log-transformed whole-body metabolism and mass exhibited a steeper slope and thus an increased oxygen requirement with size in 11 °C reared fish, potentially indicating an energetically unsustainable situation. Understanding how cold temperatures affect green sturgeon ontogeny is necessary to refine our larval recruitment estimations for this threatened species.
... Nechako white sturgeon reach the spawning ground (i.e., the Vanderhoof area) by early May (Sykes, 2009), making that month one of the most critical in the early life stages. However, Nechako white sturgeon spawning has been reported between May and June, thus all summer months are critical for early life stages (Sykes, 2009;McAdam et al., 2018). Although a combination of factors such as sediments, water flow rate, adult population size and age structure, among other variables (Jager et al., 2002) all influence the successful recruitment of white sturgeon, the importance of limited exposure to elevated temperature cannot be overemphasised (Challenger et al., 2021). ...
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... While releases of hatchery-origin fish might help restore a natural age class structure and prevent extirpation, large abundances of hatcheryorigin fish may complicate detecting improvements made to natural recruitment from other recovery actions and may increase interest in restoring fishery resources prior to recovery being fully addressed. Recent recovery actions are focusing on habitat restoration, either to improve spawning habitat (McAdam et al., 2018), ecosystem function (Kootenai Tribe of Idaho, 2009), or connectivity within rivers (Cooke et al., 2020). Determining the success of these actions in stimulating natural recruitment may be confounded by increased abundance of hatchery fish and complicate decisions around when to cease operating a hatchery supplementation program. ...
Chapter
Sturgeon are found circumglobally throughout the northern hemisphere. Longevity, late age to sexual maturation and infrequent spawning are typical life history strategies that have supported their evolution over millennia but at the same time have made them vulnerable to extirpation or extinction when population sizes have been reduced as a result of overharvest, habitat degradation and/or pollution. As a consequence sturgeons are among the most at risk species as listed by the International Union for the Conservation of Nature. Aquaculture has been used as a conservation strategy to arrest declines or maintain current population levels for several sturgeon species. Here we describe the development of this conservation strategy in sturgeons, examining the importance of understanding genotype and environment in development of appropriate rearing strategies toward improved conservation practice for this imperiled group of fishes. Recent research indicates a significant effect of environment on phenotype, with early life history being particularly relevant; evidence suggests that repatriation should be the preferred approach where possible. We suggest that while aquaculture can be a valuable conservation and recovery tool, it is particularly effective when the impacts on phenotypic development during early life history are considered and combined with effective post-release monitoring and implementation of additional restoration efforts.
... Hydraulic structures were constructed in the Rupert River to ensure water levels were maintained downstream of the diversion dam for at least half the length of the river. Spawning areas were created downstream of the weirs (McAdam et al., 2017;D'Amours and Dion, 2019) and by-passes (fishways) were constructed in the weirs to maintain connectivity up to the diversion dams. Two fishways were constructed at rkm 223 and 290 (known as KP 223 and KP 290) to facilitate passage and to accommodate natural constraints at each site prior to the construction of the diversion dam. ...
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Sturgeons throughout their circumpolar range comprise one of the most imperiled group of fishes due to their unique life history characteristics, overharvest and habitat changes and loss. Lake Sturgeon, a potamodromous Acipenseridae species, despite showing recent significant signs of recovery in the US and Canada, continue to be impacted in systems throughout its range in part because of dams on rivers in which critical sturgeon spawning and nursery habitat is not available in sufficient quantity and/or quality to maintain adequate long-term recruitment in the population due to fragmentation. There are a small number of fish passage structures and methodologies specifically designed and implemented for Lake Sturgeon in North America, but there has been no general evaluation of their installation and operation costs nor their relative effectiveness. Data were collected on seven different fish passage systems representing the range of options currently being utilized for Lake Sturgeon passage within the species’ North American range. Costs per meter of head were $206 060 for nature-like by-pass channel fishways, $305 579 for an upstream projecting pool-weir fishway, $1.1 million for a vertical slot fishway, and $1.6 million for a fish elevator. A capture and transfer operation cost an estimated $11 284 to transfer an average of 110 adult Lake Sturgeon annually. Projected costs per sturgeon passed after 40 years of operation were estimated at $12/fish for the upstream projecting pool-weir fishway, $85/fish for the nature-like by-pass channel fishways, $132 for capture and transfer, $1659 for the vertical slot fishway, and $1680 for the fish elevator. Before Lake Sturgeon passage is pursued, it is important to first determine whether passage would be necessary for restoring, maintaining, or sustaining a LS population and its genetic integrity within the system (above and below the dam); followed then, if passage is warranted, by determining what type of passage methodology might be the most effective, and the most effectively and practically funded, operated, and maintained at the dam in question.
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Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross‐ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food‐web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature's contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human–megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna.
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A severe extinction crisis of migratory fish caused by extensive hydropower development and climate change has attracted widespread environmental concern. Conserving and restoring riverine spawning habitat for migratory species is advantageous for population recovery. Depending on the reproductive characteristics of fish with adhesive eggs, functionally heterogeneous spawning habitats are required to support different stages of reproductive activity. However, few aquatic assessment models are available to consider the fine-scale functional connectivity between heterogeneous spawning habitats. This study developed a function-based framework that linked fine-scale functional connectivity modeling to habitat quality evaluations for the population recovery of migratory fish. The function path tree (FPT) model within the framework could identified the spatiotemporal dynamics of fine-scale connectivity patterns by emphasizing the attribute-dependence of patch arrangements. Here, we used the Chinese sturgeon, a well-known endangered anadromous fish producing adhesive eggs in the Yangtze River, as an example to demonstrate the applicability of the framework. Additionally, the ecological effectiveness of river restorations to overcome the detrimental influence of climate change on discharge decrease was also investigated. Compared to prior research, our methodology effectively enhanced the predictive performance of spatiotemporal distributions and quality assessments of spawning habitats. A strong correlation was discovered between the ecological profit indicator (HQI) and the estimated fecundity (R² = 0.941) and field-collected eggs (R² = 0.918). The minimum spawning discharge decreased from 8400 m³/s to 7000 m³/s by substrate restoration, with the optimal HQI growth rate of 52.7 % at Q < 8400 m³/s. This work will optimize long-term conservation for imperiled migratory species and help develop strategies to build resilience to ongoing environmental changes in flow-reduced rivers.
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Lake Sturgeon is a potamodromous, fluvial-dependent species from the family Acipenseridae, and one of the largest freshwater fishes within its North American range extending to the Great lakes, Mississippi River, and Hudson Bay drainages. Like almost all other sturgeon species, Lake Sturgeon populations throughout its range suffered mass declines or extirpation in the late 1800s into the early 1900s, due to extensive overexploitation and habitat loss and alteration. However, Lake Sturgeon are still present in low to high densities throughout their native range due primarily to factors including: the species long life span and resiliency, the remote location of many northern populations, long-term pro-active management programs effectively controlling exploitation, improved habitat and water-quality conditions, and recovery programs that have been in effect since the late 1970s. Recovery programs initiated in the late 1970s are now just beginning to show signs of natural recruitment from populations re-built with stocked fish. Large sustainable recreational Lake Sturgeon fisheries with annual harvests of up to 45 000 kg and a commercial fishery with an annual harvest of up to 80 000 kg still exist and are maintained for Lake Sturgeon due primarily to rigid regulations, harvest controls, enforcement, and user involvement. The prognosis for the species is generally good, although habitat loss and maintaining public interest in the species management and recovery continue to be the greatest threats to local and regional populations. Hydropower development, especially in the northern part of the species’ range, is especially challenging due to the potential negative impact this type of development can have on a long migrating fish like Lake Sturgeon. Advances in understanding Lake Sturgeon life history, habitat requirements, and distribution within and among water systems has strongly indicated that dams and Lake Sturgeon can co-exist, if the correct planning and necessary mitigative techniques are employed at each site on a case-by-case basis.
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Fish migrations through riverine systems can be energetically demanding, and the presence of fishways to facilitate upstream passage can add an additional energetic cost that may directly affect fitness. Successful fishway passage is a function of the ability of fish to select appropriate paths and swimming strategies that do not exceed their swimming capacity. Triaxial accelerometers were used to estimate the energetic expenditure of adult lake sturgeon (Acipenser fulvescens) swimming through a vertical slot fishway, to determine whether individual behaviour or path selection, resulting in differences in cumulative energy use, explain fishway passage success. Most individuals attempted to pass the fishway (n=30/44; 68%), although successful passage only occurred for a subset of those attempting (n=7/30; 23%). High-speed swimming was rarely observed during upstream passage through fishway basins, and was of short duration. Two turning basins delayed passage, subsequently resulting in a higher energetic cost. The rate at which energy was expended did not differ among successful and unsuccessful individuals, although successful sturgeon exhibited higher costs of transport (42.75 versus 25.85 J kg⁻¹ m⁻¹). Energy expenditure metrics were not predictive of successful fishway passage, leading us to conclude that other endogenous or exogenous factors influence passage success. In a practical application of field measurements of energy expenditure, we demonstrate that fishway passage through a structure designed to facilitate migration does result in an energetic loss for lake sturgeon (3249-16,331 J kg⁻¹), equivalent to individuals travelling 5.8-28.2 km in a lentic system.
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Hatchery supplementation of declining fish populations is commonly employed to try to increase year‐class strength. However, the success of such programs is often hampered from low postrelease survival as a result of the failure of hatchery fish to appropriately recognize predation threats. Not surprisingly, there has been considerable effort to train prey to recognize predators prior to release. The objective of our current work was to characterize the antipredator response of hatchery‐reared, predator‐naive young‐of‐the‐year Lake Sturgeon Acipenser fulvescens (an endangered species) to alarm cues from injured conspecifics and test whether these alarm cues could be used to train sturgeon to recognize unknown predators. We found that skin‐derived alarm cues elicited an antipredator response without learning and that learning required cues coming from whole‐body grinds, presumably because they represent a much more reliable indicator of risk. When the experiment was repeated with older sturgeon from Wolf River (Wisconsin), training with cues from whole‐body grinds did not enhance the response. Subjecting the fish to several training sessions (six over 3 d) led to some alteration in behavior. Our results provide insights into how ontogenetic changes (size, scute growth) could explain the different learning outcomes from the larger fish as related to hatcheries and conservation programs. Received June 24, 2015; accepted November 17, 2015
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142 Fisheries | Vol. 41 • No. 3 • March 2016 The majority of large North American rivers are fragmented by dams that interrupt migrations of wide-ranging fishes like sturgeons. Reconnecting habitat is viewed as an important means of protecting sturgeon species in U.S. rivers because these species have lost between 5% and 60% of their historical ranges. Unfortunately, facilities designed to pass other fishes have rarely worked well for sturgeons. The most successful passage facilities were sized appropriately for sturgeons and accommodated bottom-oriented species. For upstream passage, facilities with large entrances, full-depth guidance systems, large lifts, or wide fishways without obstructions or tight turns worked well. However, facilitating upstream migra - tion is only half the battle. Broader recovery for linked sturgeon populations requires safe “round-trip” passage involving multiple dams. The most successful downstream passage facilities included nature-like fishways, large canal bypasses, and bottom-draw sluice gates. We outline an adaptive approach to implementing passage that begins with temporary programs and structures and monitors success both at the scale of individual fish at individual dams and the scale of metapopulations in a river basin. The challenge will be to learn from past efforts and reconnect North American sturgeon populations in a way that promotes range expansion and facilitates population recovery.
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White Sturgeon, Acipenser transmontanus (WS), are distributed throughout three major river basins on the West Coast of North America: the Sacramento-San Joaquin, Columbia, and Fraser River drainages. Considered the largest North American freshwater fish, some WS use estuarine habitat and make limited marine movements between river basins. Some populations are listed by the United States or Canada as threatened or endangered (upper Columbia River above Grand Coulee Dam; Kootenai River; lower, middle and, upper Fraser River and Nechako River), while others do not warrant federal listing at this time (Sacramento-San Joaquin Rivers; Columbia River below Grand Coulee Dam; Snake River). Threats that impact WS throughout the species’ range include fishing effects and habitat alteration and degradation. Several populations suffer from recruitment limitations or collapse due to high early life mortality associated with these threats. Efforts to preserve WS populations include annual monitoring, harvest restrictions, habitat restoration, and conservation aquaculture. This paper provides a review of current knowledge on WS life history, ecology, physiology, behavior, and genetics and presents the status of WS in each drainage. Ongoing management and conservation efforts and additional research needs are identified to address present and future risks to the species.