ContentslistsavailableatSciVerseScienceDirect
Ecological
Engineering
jo u r n al h om ep a g e :w w w . e l s e v i e r . c o m / l o c a t e / e c o l e n g
Use
of
electromyogram
telemetry
to
assess
the
behavior
of
the
Iberian
barbel
(Luciobarbus
bocagei
Steindachner,
1864)
in
a
pool-type
fishway
C.M.
Alexandre
a,b,c,
B.R.
Quintella
a,d,∗,
A.T.
Silva
b,f,
C.S.
Mateus
a,c,e,
F.
Romão
a,
P.
Branco
b,
M.T.
Ferreira
b,
P.R.
Almeida
a,caCentrodeOceanografia,FaculdadedeCiências,UniversidadedeLisboa,CampoGrande,1749-016Lisboa,Portugal bCentrodeEstudosFlorestais,InstitutodeAgronomia,UniversidadeTécnicadeLisboa,Lisboa,Portugal
cDepartamentodeBiologia,EscoladeCiênciaseTecnologia,UniversidadedeÉvora,LargodosColegiais2,7004-516Évora,Portugal dDepartamentodeBiologiaAnimal,FaculdadedeCiências,UniversidadedeLisboa,CampoGrande,1749-016Lisboa,Portugal
eMuseuNacionaldeHistóriaNaturaleDepartamentodeBiologiaAmbiental,UniversidadedeLisboa,RuadaEscolaPolitécnica58,1250-102Lisboa,Portugal fFaculdadedeEngenharia,UniversidadedeManitoba,WinnipegMBR3T5V6,Canada
a
r
t
i
c
l
e
i
n
f
o
Articlehistory: Received9July2012 Receivedinrevisedform 30November2012 Accepted3December2012 Available online 3 January 2013 Keywords: EMGtransmitters Fishpassage Cyprinids Riverconnectivity Potamodromousmigration
a
b
s
t
r
a
c
t
Declineinfishspeciespopulationsduetoriverregulationbydamsandweirspromotedthedevelopment offishways,whicharebecomingoneofthemostcommonmeasuresfortherestorationofconnectivity inrivers.Fishwaysefficiencycanbespeciesspecificandthusmonitoringandevaluation,andsubsequent adjustmentstodesignandhydraulicfeatures,arerequiredtoinformpotentialuserspriortoinstallation. Inthisstudywetestedtheapplicabilityofelectromyogramtelemetrytostudytheswimmingbehavior ofacyprinidpotamodromousspecies,theIberianbarbelLuciobarbusbocageiSteindachner,1864,inan experimentalpool-typefishway.Intotal,24barbelswereusedintheexperiment,12ofwhichweretagged withEMGradiotransmittersequippedwithelectrodesthatregistermuscleactivity,whiletheother12 untaggedfishwereusedascontrol.Fortaggedfish,arelationshipbetweenswimmingspeedandEMG telemetrysignalswasdevelopedinaswimmingtunnel,whichwaslaterusedtoassessbarbelsswimming behaviorwithintheexperimentalfishway.Taggedfishexhibitedhighpassagesuccessandanaerobicburst swimmingwasonlyrequiredtomovethroughthesubmergedorificesofthefishway.Barbelsspent suc-cessivelylesstimewhentransversingthepoolsintheupstreamdirection.Measuredhydraulicvariables thatwererelatedwithbarbels’swimmingspeedwithinthefishwayswerethewatervelocity,turbulent kineticenergy,turbulenceintensityand,especially,thehorizontalcomponentofReynoldsshearstress, highlightingtheimportanceoftheseparameterswhendesigningpool-typefishways.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
Fragmentationandlossofaquatichabitat,originatedwiththe
construction ofartificial barrierssuchas dams,weirs, roadsor
bridges,aretwoofthemostimpactinganthropogenicactionsin
riverineecosystems(DynesiusandNilsson,1994;Jungwirthetal.,
2000;Nilssonetal.,2005).Inthesesystems,fragmentationiseasy
toaccomplishsinceasingledammingeventisenoughtoisolate
adjacentriversegments,contributingforthedramaticdeclinein
therangeandabundanceoffreshwaterfish(CowxandWelcomme,
1998;Jageretal.,2001;LucasandBaras,2001;LucasandFrear,
1997).Migratoryfishthat includeriversystemsin theirroutes,
∗ Correspondingauthorat:CentrodeOceanografia,FaculdadedeCiências, Uni-versidadedeLisboa,CampoGrande,1749-016Lisboa,Portugal.
Tel.:+351217500148;fax:+351217500009. E-mailaddress:[email protected](B.R.Quintella).
namelydiadromousandpotamodromousspecies,areparticularly
affectedbythisproblem(Poulet,2007).
Thecontinuousdeclineofmanyfishspecies’stockspromoted
thedevelopmentoffishways,whichemergedashydraulic
struc-turesbuilttoaidthemovementoffishpastthebarriersandare
becoming one of the most commonmeasures for the
restora-tionoflongitudinalconnectivityinrivers(Alvarez-Vázquezetal.,
2007;Clay,1995;Katopodis,2005;Knaepkensetal.,2007).The
importanceofsuchdeviceswasrecentlyreinforcedwiththe
devel-opmentandapplicationofwatermanagementtools,suchasthe
EuropeanWaterFrameworkDirective(EWFD,2000/60/CE),which
demandsaneffectiveandundisturbedmigrationoffishspeciesas
akeycomponentofwatershedrestoration(EuropeanCommission,
2000).Pool-typefishwaysarethemostcommontypeoffishways
builtatriverbarrierssuchassmallhydropowerplantsandweirs
(Larinier,2002;Santosetal.,2012).Thesestructuresgenerally
con-sistofaseriesofpools,arrangedinasteppedpattern,separated
bycross-walls thatcanbeequippedwithsubmergedorificesat
0925-8574/$–seefrontmatter © 2012 Elsevier B.V. All rights reserved.
thebottomandsurfacenotches,wherebyfishmovefrompoolto
poolbyleapingoverthesurfacenotchesorswimmingthroughthe
bottomorifices.Theirmainpurposeistoensuretheadequate
dis-sipationofwaterenergyandofferrestingareasfor,predominantly
upstream,migratingfishes(Katopodis,2005).
Studiesonfishwayshaveprovidedinformationonhowfishuse
thesefacilitiesduringtheirupstreammigrations.Trappingfishin
fishways atdamshasbeencommonlyusedtoassessthe
num-berandspecies offishthatsuccessfullynegotiatethepass(e.g.
Barasetal.,1994;Prchalováetal.,2006).Nonetheless,thismethod
doesnotprovideinformationontheeffortandbehavior offish
in thevicinityof theobstructionand during ascent(Lucasand
Frear,1997).Furthermore,mostofthestudiesdevelopedtoassess
theeffectivenessofthesestructuresmainlyfocusondiadromous
species,namelysalmonids,duetotheirhigheconomicaland
recre-ationalvalue(e.g.Bunt,1999;Katopodis,2005;Laineetal.,2002;
Naughtonetal.,2007),withalowemphasisgiventocoarse,
pota-modromousspecies,suchascyprinids,oflowcommercialvalue
(Buntetal.,2012;Puertasetal.,2012;Noonanetal.,2012;Roscoe andHinch,2010).Therefore,studiesconcerningthemovements
andbehaviorofthesespeciesarenecessary,consideringtheir
bio-logicalimportanceonthecompositionoffishassemblages.This
challengeisspeciallyhighlightedinIberianrivers,wherecyprinid
fishesarefrequentlythemostdominantandabundantgroupof
species(Cabraletal.,2005;Doadrio,2001).
Fishtelemetrywasreportedforthefirsttimein1956andsince
then ithasbeenusedextensively tomonitortheactivitiesand
movementsofmigratoryandresidentfishesthroughouttheworld
(Cookeetal.,2004).Conventionaltelemetrymethodsonlylocate
individuals,beingusefulindeterminingpositionsandmovements
ofindividualfish.Recently,biotelemetrytechnologyhasdeveloped
intoavarietyofhighlysophisticatedtechniquesthatmeasureand
transferwirelessinformationfromfree-swimmingfishon
phys-iologicalvariablessuchasheartrate,opercularrateandmuscle
activity(Cooke etal.,2004).Aradiotransmitter wasdeveloped
whichdetectsandtransmitstheelectromyograms(EMG)produced
duringaxialmusclerecruitment(Cookeetal.,2004;Thorstadetal.,
2000).EMGarechangesinbioelectricalvoltagestronglycorrelated
withstrengthanddurationofmusclecontractionsand,when
mea-sured,canbeuseddirectlyasindicatorsoftherelativefishactivity.
Thisrelativelyrecenttelemetrytechniqueofferstheopportunity
toobtainquantitativeestimatesofthemetaboliccostsofactivity
byfreerangingfishreleasedinthewildbycalibratingEMGto
tail-beatfrequency,swimmingspeedoroxygenconsumption(Cooke
etal.,2004;Kaselooetal.,1992).UseofEMGcanprovideinsights
intotherelativeswimmingeffortandenergeticcostsofmigration
throughparticulartypesofhabitatandpassagestructuresandit
isapromisingtoolforwatershedrestorationand,inparticular,for
theevaluationoffishwaydesignswheredirectvisualobservations
arefrequentlynotpossible(Hinchetal.,1996).
TheIberianbarbel(LuciobarbusbocageiSteindachner,1864)is
apotamodromouscyprinidendemictotheIberianPeninsulaand
occursinawiderangeofloticandlentichabitatsandinalmostall
theriverbasinsofnorthernandcentralPortugal(Lobón-Cerviáand
Fernández-Delgado,1984;Magalhães,1992;Oliveiraetal.,2002).
Itisconsideredanon-threatenedspeciesintheIberianPeninsula
(Cabral etal., 2005;Doadrio,2001).During spring,this species
migrates upstream tospawnin gravel or sandy riverbed areas
withfastwater flow, thus beingconsidereda reophilicspecies
(BarasandCherry,1990;Barasetal.,1994;Rodríguez-Ruizand Granado-Lorencio,1992).Thisspecies hasreceivedsome
atten-tioninrecentyearsthroughstudiesonitsmigrationecology(e.g.
Santosetal.,2005)andaerobicswimmingcapacity(Mateusetal.,
2008).Morerecently,someworkhasbeendonetoinvestigatethe
species’behaviorwhenmovingthroughanexperimentalpool-type
fishway(Silvaetal.,2009,2011,2012a,b).However,thereisstilla
lackofknowledgeaboutsomespecificaspectsofIberiancyprinids
behaviorwithinsuchdevicesandtheuseofnewlydeveloped
tech-nology,suchasphysiologicaltelemetry,remainsapowerfuland
untestedtooltoassesstheinfluenceoffishwaydesignand
asso-ciatedhydraulicfeaturesonthebehavior,swimmingperformance
andenergeticcostsrelatedwiththefishwaypassageofthesefish.
Themainobjectiveofthisstudywastotesttheapplicabilityofa
biotelemetrytechnique,theEMGtelemetry,asamethodtoassess
thebehaviorofL.bocageiinanexperimentalfishway.Specifically,
thefollowingquestionswereposed:(i)isEMGtelemetryavalid
methodforassessingthebehavioroffishwithinthesestructures?;
(ii)doesthis speciesshow anytype of learningpattern during
thenegotiationoftheobstacle;(iii)isthisfishwayconfiguration
suitableforacost-efficientpassageofthisspeciesand(iv)which
hydraulicparametersaffectthebarbels’swimmingperformance
withinthistype offishway.Weexpectthis studytocontribute
tothevalidationoftheelectromyogramtelemetryasa
monitor-ingmethodforpool-typefishwaysandforimprovedknowledge
andunderstandingof L.bocageibehaviorduringpassageofthis
typeoffishways.Datacollectedwiththisbiotelemetrytechnique
maybeusefulforengineersinvolvedinwatershedrestoration
pro-gramstohelpthedesignofnewfishwaysandtomodifyexisting
onesinorder toimprove attractionand passageefficiency and
guaranteethelongitudinalconnectivityenhancement(Cookeetal.,
2004).
2. Methodology
2.1. Fishcaptureandtaggingprocedure
Between May and July 2009 a total of 24 barbels of
comparable size (mean Lt±S.D.=45.1±34.3cm, mean
Wt±S.D.=798.19±200.40g) were caught in River Sorraia
(38◦59N; 08◦17E), a tributary of River Tagus basin, Portugal,
using an electrofishing gear (Hans Grassl EL 62 generator, DC,
600V, 10A). Twelveof thesefish wereused ascontrols inthe
fishwayexperimentsand12weretaggedwithimplantablecoded
electromyogram radio transmitters (CEMG-R11-25; 12g in air,
12mmindiameterand56mminlength),manufacturedbyLotek
Wireless, Newmarket, Ontario. The transmitters weighted less
than2%ofbarbels’bodyweightintheair(Jepsenetal.,2002).
Elec-tromyogramtransmittersdetectthevoltagedifference(potential)
betweenelectrodes in themuscles of fish(Brown etal., 2007;
Cookeet al., 2004; Enders et al.,2007).The CEMG transmitter
outputwasdetectedandrecordedbyaportablecombinedreceiver
anddatalogger(SRX400fromLotekWireless)throughacoaxial
antenna.Datawereloadedintoacomputerforstorage,processing
andstatistical analysis,through a RS-232serialcommunication
portusingthesoftwareWINHOST.
ThetaggingprocedurewassimilartothatdescribedbyBooth
etal.(1997),Quintellaetal.(2004),Thorstadetal.(2000),among
others.Experimentalfishwereanaesthetizedbyimmersionin
2-phenoxyethanolata concentrationof0.4ml/land measuredfor
totallength(Lt)andtotalbodyweight(Wt).Thefishwereplaced
onaV-shapedsurgicaltable,ventralsideup,andcontinuously
sup-pliedwithanestheticsolutionatalowerconcentration(0.3ml/l)to
maintainsedationandgillsoxygenationduringthetagging
proce-dure.Thetransmitterwasplacedposteriorlyintheintraperitoneal
cavityandthepairofgold-tippedelectrodeswaspositioned,in
par-allel,intotheleftredaxialmusculatureabovethelateralline.The
distanceandlocationoftheelectrodeswasstandardizedinorder
toallowagoodEMGsignalreception,aswellasaccurateand
McKinley,1999;Bunt,1999;Cookeetal.,2004).Thecomplete
sur-gicalproceduretookca.10min.Allfishwerelefttorecoverfor
2days ina 2000lcircularfiberglassholdingtankundera
con-trolledphotoperiod(12hlight:12hdark)andwatertemperature
(18±1◦C).
2.2. CalibrationofCEMGtransmitteroutputwithswimming
speed
Followingthe2-dayrecoveryperiod,anindividualcalibration
procedurewas developed to convert CEMGtransmitter output
fromthetaggedfishintoinstantaneousswimmingspeeds.This
procedurewasconductedin amodifiedBrett-typeswimtunnel
(formoredetailsontheswimapparatusseeMateusetal.,2008).
Inthebeginningofthecalibrationprocedure,fishunderwentan
acclimationperiodof30minintheswimchamberatalowwater
velocityofca.0.1m/s.TransmissionsfromCEMGtransmitterwere
recordedwhilethefishswamat14differentspeeds(0.2–1.5m/sin
0.1m/sincrements).Eachswimmingspeedwasmaintainedfora
maximumperiodof5minandCEMGreadingswererecordedwhile
thefishwasswimmingsteadilyinplace.RestingCEMGvalueswere
recordedwhentheanimalwassubjectedtonullwatervelocity,
remainingcompletelymotionlessfortheentireprescribedinterval.
Thecalibrationproceduretookabout4hperfish,dependinglargely
onfishbehavior.Thecalibrationprocedurewasvideotapedwitha
time-synchronizeddigitalvideocamerarecorder(SonyDCR-PC1E).
Videorecordingswere reviewedafter testingto excludeCEMG
readingsthatoccurredwhenfishwerenotswimmingsteadily.The
remainingCEMGreadingswereexpressedasanaverageforeach
swimmingspeed.Attheendofthecalibrationprocedure,thefish
werereturnedtotheholdingtank.
2.3. Experimentalfishway
The study was conducted in an experimental full-scale
pool-typefishway installedat theHydraulics andEnvironment
Department of the National Laboratory for Civil Engineering
(LNEC),inLisbon(Portugal).Thepool-typefishwayprototypewas
comprisedofaflume(10mlong×1mwide×1.20mhigh)ona
8.5%slopewith6pools(1.90mlong×1.0mwide×1.2mhigh),
dividedbyfivecompactpolypropylenecrosswalls,eachequipped
withasubmergedorifice(23cm×23cm)andsidewallsmadeof
acrylicglasspanels.Thisexperimentalapparatusalsoencompassed
twoconcretetanks,locatedattheupstreamanddownstreamend
oftheflume,with1.5mlong×1.0mwide×1.2mhighand4.0m
long×3.0mwide×4.0mhigh,respectively.Thefirsttankensured
thatsmoothflowenteredtheflume,whilethelatterwasusedas
anacclimationchamber.Foradetailedschemeofthefishwaysee
Silvaetal.(2011)andSantosetal.(2012).
2.4. Hydraulics
Duringtheexperiments,theflowinthefishwaywas65l/s,and
themeanwatervelocityinthesubmergedorificesandpoolswas
1.48m/sand0.27m/s,respectively.Thesubmergedorificeswere
placedinanoffsetarrangement,whichwaspreviouslyfoundto
bemorebeneficialforthepassageoftheIberianbarbelina
sim-ilarstudyconcerningthis species(Silvaet al.,2012b),where it
wasobservedahigherrateofpassagesuccessrelativetoastraight
orificeconfiguration.
Instantaneouswatervelocitymeasurements wereconducted
usinga3DAcousticDopplerVelocimeter(ADV)(NortekAS),placed
verticallydown.Thisdevicewasselectedforthemeasurements
becauseofitsabilitytocorrectlymeasurethethree-dimensional
velocitycomponents(x,y,z)offlowing water(Eadetal.,2004;
Guiny et al.,2003).Flowpattern and headdrop (h)between
poolsweresimilarinallpools(h=0.16m).Consequently,
mea-surements weremadeintheseconddownstreampool(P1) and
consideredrepresentativeofthehydraulicconditionswithinthe
fishway.Themeasurementswereperformedatdistinct
horizon-talplanesparalleltotheflumebottom,at25,50and80%ofthe
poolmeandepth(hm).Apredefinedgridof48measuringpoints
wasusedasreferencetothemeasurementsineachplane.Intotal,
2500instantaneousmeasurementswererecordedforeach
samp-lingpoint.Measurementswererecordedat25Hzforasampling
periodof90sineachpointonthegridtodeterminethewater
veloc-ity(WV),turbulentkineticenergy(TKE),turbulenceintensity(TI)
andReynoldsshearstress(RSS).The90ssamplingperiodwas
con-sideredtoberepresentativeforanappropriatedeterminationof
meanvelocityandturbulencewithinthepool(Silvaetal.,2011).To
understandandcharacterizethemajorhydraulicforcesactingon
thefishandaffectingitsupstreammovementwithinthefishway,
theRSSwasdeterminedforitsthreecomponents:horizontal(XY,
−uv),vertical(XZ,−uw)andtransversal(YZ,−vw),with
beingthewaterdensity(1000kg/m3)andu,
v
andwarethefluc-tuatingvelocitiesintheX,YandZdirections,respectively.Toallow
forcomparisons,allhydraulicparametersmeasuredweremade
dimensionlessbyusingmaximumflowvelocityattheorifice(V0)
(Liuetal.,2006).Amoredetaileddescriptionofmeasurement
pro-cedures,theoreticalassumptionsaboutthesehydraulicvariables
andhydraulicpatternswithinthefishway(Fig.1)areincludedin
Silvaetal.(2011,2012b).
2.5. Fishwayexperiments
Atotalof24barbelsweretestedinthefishwayexperiment,of
which12weretaggedwithCEMGtransmitters.Nosurgerywas
performedoncontrolfish,whichwereheldunderthesame
condi-tionsastheexperimentalfish.Theseindividualswereusedtotest
possibleeffectsofCEMGtransmitterimplantationandsubsequent
manipulationduringthecalibrationprocedure,bycomparingthe
swimmingbehaviorbetweentransmitter-implantedfishand
con-trols.Theuseofuntaggedfishwasalsoimportanttoreducethe
stressofthetaggedfishatthetimeofreleaseintheexperimental
fishwaysincethisspeciesiscommonlyseenschoolingduringthe
spawningmigration.
Fishbehaviorwasmonitoreddirectlythroughtheacrylicglass
side-wallsoftheflumeandthroughaglasswindowlocatedinthe
downstream tankbymeansof directobservation. These
obser-vations weresupplemented by video recording, usingan array
oftwovideocameras.Atthebeginningoftheexperiments,one
taggedbarbelandonecontroluntaggedanimalwereplacedinto
theattractionpool(P0)tofreelyascendthefishway.Additionally,
amoredetailedobservationwasfocusedonthebarbels’behavior
intheseconddownstreampool,whichwasconsideredtobe
rep-resentativeofthehydraulicconditionsintheremainingupstream
pools.Onecamerawasplacednearthesidewallofthispool
(lat-eralview)andanotheronewaspositionedabovethewatersurface,
facingdownwards(topview).Bothcameraswereplacedatafixed
distancefromthepool.Areferencegridofcellswasplacedabove
thepoolandguidinglinesrepresentingthethreehorizontalplanes
(0.25,0.50and0.80),wereplacednearthesidewalltoaidinthe
videomonitoringprocess.Eachtrialwasconductedforamaximum
durationof180min.CEMGreadingsfromthetransmitterssignal
wereusedtodeterminetheswimspeedofL.bocageiinthefishway,
basedonthecalibrationcurveequation.
Videorecordsoftheseconddownstreampoolwereanalyzed
usingtheIVisionLabviewsoftwarefromNationalInstruments
Cor-poration,allowingthecollectionofexactlocationandtimingof
Fig.1. Hydraulicpatternsassociatedwithwatervelocity,turbulentkineticenergy,turbulenceintensityandthethreevectorsofReynoldsshearstress(horizontal– uv, vertical– uw,tranversal– vw),measuredatthethreehorizontalplanes(0.25,0.50and0.80hm)intheseconddownstreampool,inanoffsetarrangementofthesubmerged
orifices.ThesizeofthevectorsintheWVfigurerepresentsthemagnitudeofthisparametervalues.Inthecolorfigures,thewaterflowsfromthebottomrighttothetopleft side.
cell,whenmorethanhalfofitsbodylengthwaswithinacell’s
boundaries.
2.6. Statisticalanalysis
RegressionanalysisbetweenaverageCEMGtransmitteroutput
(dependentvariable)andswimmingspeed(independentvariable)
wasperformedforallfishsuccessfullycalibratedintheexperiment.
Theadoptedmodelwasexponentialbecauseitwasthebest
adjust-menttothedata.Ananalysisofcovariance(ANCOVA)wasused
tocomparethelinearslopesandinterceptsoftherelationships
betweenindividualsandtransmittersoutput(independent
vari-able),usingswimmingspeed ascovariate.Theobjectiveof this
analysiswastotestifindividualCEMGtransmittersproduce
signif-icantlydifferentresultsindifferentfishesandtoassessifasingle
calibrationequationcouldbeusedinfuturestudiestocalculate
swimmingspeedforalltaggedfish.
Toassessifthetaggingprocedureinfluencedthebehaviorof
thetestedbarbels,Mann–WhitneyU-testswereusedtocompare
thebehavioroftaggedandcontrolbarbelsregardingtheirpassage
timeineachoneofthefourpoolsandthetotalamountoftimethey
Swimmingspeedvalues,derivedfromtheEMGsignalrecorded
duringfishwaytrials,weregroupedineightclasses(0–0.2;0.2–0.4;
0.4–0.6;0.6–0.8;0.8–1.0;1.0–1.2;1.2–1.4;>1.4m/s)foranalysisof
swimmingspeedfrequencydistribution.Aone-wayPERMANOVA
analysiswasperformedtocomparebarbelswimmingspeed
fre-quencydistributionbetweeneachoneofthepools(P1–P4)during
theirfirstascentofthefishway.Thisanalysiswasperformedusing
the add-on package PERMANOVA for PRIMER+v6.0 (Anderson
etal.,2008).
Kruskal–Wallistests,withaSimultaneousTestProcedure(STP)
(SiegelandCastellan,1988)formultiplecomparisons,wereusedto
comparetheaverageswimmingspeedandpassagetimeexhibited
bythebarbelsin eachoneofthepools.Thesameanalysiswas
appliedtocomparetheaverageswimmingspeedintheattraction
pool(P0)amongthegroupoffishthatdidnotenterthefishway,
thegroupthatenteredthefishwaybutdidnotsuccessfullyascend
theentirefishwayandthegroupoffishthatsuccessfullyascend
theentirefishway.
AWilcoxonsigned-ranktestwasusedtotestthedifferences
inthetotaltimespenttoascendthefishwayinthefirstand
sec-ondpassagesbythefishthatsuccessfullynegotiatedthefishway
atleasttwotimes.AGoodness-of-Fittest(SokalandRohlf,1981)
wasconductedtocomparetheswimmingspeedfrequencies
dis-tributionbetweenthefirst(expectedvalues)andsecond(observed
values)ascentofthefishwayforeachbarbel.
Correlations between swimming speed values and mean
velocity,turbulentkineticenergy,turbulenceintensityand
three-dimensional Reynolds shear stresses were analyzed using the
Spearmanrankcoefficient.Allstatisticalanalyses,withthe
excep-tionofPERMANOVA,wereconductedwithRpackage(v2.11.1).
3. Results
3.1. CalibrationofCEMGtransmitteroutputwithswimming
speed
Nomortalityoccurredasaresultofthesurgicalprocedureused
toimplantthetransmittersandnoinfectionwasdetectedaround
theincisionarea.Attheendofeachcompleteexperimental
pro-cedure,thebarbelsweresacrificed toconfirmcorrectelectrode
placementand there wasnoevidenceof internaldamage from
theimplantationofthetagandelectrodes.Apparently,electrodes
remainedinplace(7.37mm±1.35averagedistancebetween
elec-trodes),thoughminordisplacementmayhaveoccurredbutdid
notresultinperceptiblechangeintheEMGsignal.Allsuccessfully
calibratedfishexhibitedastrongrelationship(R2rangedbetween
0.744and0.960;P<0.001)betweenCEMGtransmitteroutputand
swimmingspeed(Table1).TheANCOVAanalysisconductedtotest
thepossibilityofusingthesamecalibrationequationforallanimals
tagged withthe CEMG transmitters revealed significant
differ-ences intheintercepts(F11,124=6527.281;P<0.001)and slopes
(F11,113=4.812;P<0.001)ofthelinearregressionsofthetagged
barbels.Therefore,individualcalibrationofCEMGtransmitter
out-putwithswimmingspeedwasperformedforeachtaggedbarbel
usedinthesubsequentanalyses.
3.2. Experimentalfishwaystudy
No behavioral differences were observed between the fish
taggedwiththetransmittersandtheuntaggedfishusedas
con-trol,sinceMann–Whitneytestsrevealednosignificantdifferences
between thetime spentby each group of barbelsin each one
of the four pools (maximum U=42.00; P>0.05) and the total
amount of time they spent to ascend the fishway (U=41.00,
P>0.05).
WithinthetaggedbarbelsreleasedinP0,75%(N=9)managed
toenterthefishwaywithinthetrialperiodwhiletheremaining
25%(N=3)didnotleavetheattractionpool.Fromtheninetagged
barbels that entered the fishway, seven managed to arrive at
theupstreamend ofthefishwaywhiletwo didnotachievethe
upstreamendwithinthetrialperiodandonlyreachedoneofthe
fourintermediatepools(P1–P4).Thesefishpresentedsome
activ-ity inthepools allowingtherecordof suitablebehavioral data
(Table2).Alloftheuntaggedcontrolbarbelsmanagedtoenterthe
fishwayand67%ofthemreachedtheupstreamendofthefishway.
The PERMANOVA analysis conducted to test differences in
swimmingspeedfrequencydistributionsdidnotrevealed
signif-icant differencesbetweenanyofthepools(F=0.449;P=0.734).
Frequencydistributions of swimmingspeeds inP1–P4are
rep-resented in Fig. 2. The Kruskal–Wallis analysis conducted to
test differences in barbels’average swimming speeds, alsodid
notrevealsignificantdifferencesbetweenthepools(2=1.273;
P=0.757). On the contrary,the same analysis revealed
signifi-cantlydifferentpassagetimesbetweenthefourpools(2=16.157;
P<0.001).Thetestformultiplecomparisons(STP)revealedthat
barbelssignificantlyspentmoretimenegotiatingP1thantheother
pools(Fig.3a).Fortheseanalyses,onlythesevenbarbelsthat
com-pletelyascendedthefishwayintotheupstreampool,atleastonce,
wereconsidered.
Theaverageswimmingspeedintheattractionpool(P0)was
significantlydifferentbetweenthethreegroupsofbarbels
clus-tered considering theirperformance in thefishway ascent(i.e.
notentered,enteredorpassed)(Kruskall–Wallistest;2=6.471;
P<0.05).Thesimultaneoustestrevealedaloweraverage
swim-mingspeedinP0forthebarbelsthatdidnotlefttheattraction
poolduringtheentirefishwaytrial,intermediateforthosethatonly
enteredinthefishwayandthehigheractivitylevelswheredetected
amongthebarbelsthatpassedtheentirefishwaystructure(Fig.3b).
Table1
RelationshipsbetweenCEMGtransmitteroutputandswimmingspeed(m/s)forthe12barbelstestedintheswimtunnelduringthecalibrationprocedure.Allregression modelswerehighlysignificant(P-value<0.001).
BarbelID Surgerydate Calibrationdate Fishwaytrialdate Calibrationequation R2
#86 18-05-2009 21-05-2009 22-05-2009 y=2.824e1.084x 0.907 #87 18-05-2009 21-05-2009 22-05-2009 y=2.565e0.732x 0.816 #90 25-05-2009 28-05-2009 29-05-2009 y=2.165e0.749x 0.858 #91 25-05-2009 28-05-2009 29-05-2009 y=2.311e0.804x 0.729 #94 01-06-2009 04-06-2009 05-06-2009 y=5.462e0.671x 0.807 #95 01-06-2009 04-06-2009 05-06-2009 y=3.678e1.213x 0.940 #98 08-06-2009 11-06-2009 12-06-2009 y=5.111e0.708x 0.858 #99 08-06-2009 11-06-2009 12-06-2009 y=3.261e1.155x 0.900 #102 15-06-2009 18-06-2009 19-06-2009 y=5.614e1.139x 0.862 #103 15-06-2009 18-06-2009 19-06-2009 y=3.420e1.484x 0.960 #106 22-06-2009 25-06-2009 26-06-2009 y=9.056e0.565x 0.744 #107 22-06-2009 25-06-2009 26-06-2009 y=4.789e0.823x 0.916
Table2
Dataonindividualbarbelstestedinthefishway.
BarbelID TimeinP0(min) Totaltimeinpools(min) SSinP0(m/s) SSinpools(m/s) %TimeaboveUcrit Ascentofthefishway
#86 72.3 21.0 0.59 0.43 10.7 Passed #87 180.0 0.0 0.34 – 3.4 Notentered #90 145.5 34.5 0.42 1.02 32.9 Entered #91 75.3 15.3 0.62 0.71 17.3 Passed #94 27.1 9.4 0.50 0.30 7.4 Passed #95 109.5 24.1 0.45 0.53 9.9 Passed #98 180.0 0.0 0.29 – 5.7 Notentered #99 142.1 37.8 0.40 0.32 8.8 Entered #102 75.4 9.2 0.49 0.39 3.3 Passed #103 135.5 35.5 0.34 0.40 4.6 Passed #106 180.0 0.0 0.18 – 0.4 Notentered #107 136.7 43.3 0.65 0.71 27.9 Passed
SS:averageswimmingspeed;P0:acronymforattractionpool;Ucrit:criticalswimmingspeed;ascentbehavior:notentered–fishthatdidnotenterthefishway,entered–
fishthatenteredthefishwaybutdidnotsuccessfullyascendtheentirestructure,passed–fishthatsuccessfullyascendedthefishway.
Fig.2.Swimmingspeeds(m/s)recordedwithtaggedbarbelsduringthepassagetimeinpools(Pool1–Pool4)oftheexperimentalfishway.SS:averageswimmingspeed.
Fig.3.Averageswimmingspeed(m/s)andpassagetime(min)inthefourpools (Pool1–Pool4)oftheexperimentalfishway(a)andaverageswimmingspeed exhib-itedintheattractionpool(P0)bythethreegroupsoffishes(b).
Fig.4 presentsa typicalswimmingspeedvs. timegraph for
aselectedbarbel(#103) thatcompletelyascended thefishway.
Anaerobicburstswimming(aboveUcrit)wasonlyrequiredtomove
throughthesubmergedorificesofthefishway,sincethemajority
ofthebarbels’swimmingvelocitiesduringthatperiodwerebelow
thetheoreticalUcritlevelsforabarbelofthatparticularLt.The
pro-portionoftimespentbythetaggedbarbelsbelowthetheoretical
Ucritwasmuchhigherthantheproportionoftimespentabovethis
value.
Fromtheninebarbelsthatenteredthefishwayintoanyofthe
poolsorthatcompletelypassedthroughit,fivemanagetoascendit
atleasttwotimesallowingthecomparisonofswimmingspeed
fre-quenciesbetweenthefirstandthesecondpassage(Fig.5).Mostof
theanalyzedbarbelsdidnotexhibitedsignificantswimmingspeed
differencesbetweenthefirstandsecondfishwayascents,withthe
exceptionof fish#102and #107who presenteda significantly
higherproportion ofthelowerswimming speed classesduring
thesecondfishwayascent(2=190.04;P<0.001and2=85.13;
P<0.001,respectively).Ontheotherhand,thetotalamountoftime
thatbarbelsspenttoascendthefishwayforthesecondtimewas
significantlylower(Wilcoxon’stest;Z=5.031;P<0.05)thanthe
timespentforthefirstpassage.
Eightof the tested barbelsentered the second downstream
Fig.4. Behaviorofthetaggedbarbel#103(recordedasswimmingspeeds,m/s)duringtheascentoftheexperimentalfishway.Thepiechartrepresentstheaveragepercentage oftimespentbyallthebarbelsaboveandbelowthetheoreticalcriticalswimmingspeed(Ucrit).TheoreticalUcritandcalculatedswimmingspeedscorrespondingtoCEMG
transmitteroutputareshownintheY-axis.Passagesfromonepooltotheotherarealsoidentified(Px–Py):P0–fishwayattractionpool;P1–fishwayfirstrestpool;P2– fishwaysecondrestpool;P3–fishwaythirdrestpool;P4–fishwayfourthrestpool;P5–fishwayupstreampool.
Fig.5. Swimmingspeeds(m/s)andtotaltimespentbythebarbelsduringthefirstandsecondascentoftheexperimentalfishway.SS:averageswimmingspeed.n.s.: non-significant;**P-value<0.001.
Table3
SummaryoftheresultsfromSpearmanrankcorrelationsconductedtotesttheeffectsofthehydraulicparametersmeasuredattheseconddownstreampool(P1),namely watervelocity(WV),turbulentkineticenergy(TKE),turbulenceintensity(TI)andReynoldsshearstressatthehorizontal(RSSuv),vertical(RSSuw)andtransversal(RSSvw)
planes,onfishswimmingspeed.
Dependentvariable Independentvariables Spearmanranktest, P-value
Swimmingspeed(m/s) WV(m/s) 0.22 <0.001 TKE(m2/s2) 0.33 <0.001 TI 0.22 <0.001 RSSuv(N/m2) 0.53 <0.001 RSSuw(N/m2) 0.04 0.093 RSSvw(N/m2) −0.02 0.435
Fig.6. Swimspeedofanexamplebarbel(#86)duringpassagetimeinthefirstpool(P1)oftheexperimentalfishway.(a)Watervelocity,turbulentkineticenergy,(b) Reynoldsshearstressatthethreeplanes(uv,uwandvw)and(c)turbulenceintensityarealsopresented.Hydraulicparametersvaryaccordingtofishlocationwithinthe pool.
the collection of suitable data for assessing the effects of the
hydraulicvariables onfishswimmingspeedwithineachone of
thegridcells.Regardingthisanalysis,asignificantpositive
rela-tionbetweenswimmingspeedandmeanWV(=0.22;P<0.001)
wasfoundforthetestedfishes(Table3;Fig.6).Asimilar
rela-tionshipwithfishswimspeedwasalsofoundforTKE(=0.33;
P<0.001)andforTI(=0.22;P<0.001).Liketheprevious
param-eters,thehorizontalvectorofRSSwasfoundtobesignificantly
correlated withswimmingspeed (=0.53;P<0.001).Of allthe
hydraulic variables tested, this wasthe one that exhibited the
highestcorrelationcoefficientwithbarbels’swimspeed.No
sig-nificantcorrelations werefoundbetweenfishswimmingspeed
andtheothertwoRSSvectors,namelytheverticalandtransversal
planes.
4. Discussion
Studiesanalyzingtheswimmingbehavioroffishaccordingto
differentphysiologicalandenvironmentalconditionscanprovide
valuabletoolsforenvironmentalmanagerstoassessthequality
oftheaquaticenvironmentanditseffects ontargetspecies.For
example,amanagerthatwishestoimprovethedesignofa
fish-waytoallowthepassageofatargetfishspeciescanusethesedata
todeterminetheadequatehydraulicarrangementtoincreasethe
efficiencyofthatfacility(Peakeetal.,1997).Knowledgeoffish
bio-logicalresponsewithinfishwayscanalsobeusedtodevelopor
improvecomputermodelsoftenusedbyengineerstoevaluatethe
efficiencyofoldornewfishwaydesigns(Puertasetal.,2012).By
allowingthephysiologicalanalysisoffishswimmingspeed
varia-tionsandenergeticcostsrelatedwithdifferenthydraulicscenarios,
theoutputresulting fromtheuseof thesetransmittersbridges
agapassociatedtofishwaydesignsbasedpurelyonswim
tun-nelperformance,whichinsomecasesdoesnotaccuratelyreflect
realfieldperformances(Peake,2004).Theworkdescribedinthe
presentstudy isparticularlynovelin itsareabecause it
repre-sentsthefirstattempttoanalyzeacyprinidbehaviorwithinan
experimentalpool-typefishway,whereseveralhydraulic
condi-tionsandstructuraldesignscanbesimulated,byusingnotonly
thedirectobservationoffishbutalsomoredetailedand
instan-taneousinformationaboutfishphysiologicalresponsetodifferent
hydraulicconditions,throughtheuseofEMGsensorsthatrecord
Highlysignificantregressionswere obtainedbetweenCEMG
transmitteroutputandswimspeed,whichrevealsthatthis
tech-nologyisagoodindicatorofswimmingactivity,andthusbehavior,
ofthisspeciesinthewild.Also,duringthecalibrationprocedure,
alltaggedbarbelsperformedwellintheswimmingchamberand
didnotseemtobeaffectedbythetransmitters’implantationin
termsofswimmingcapacityandbehaviorwhencomparedwith
theMateusetal.(2008)study.Theseresultsclearlyvalidatethe
useof electromyogram telemetry asa methodto studybarbel
swimmingphysiologyandrevealitspotentialtobeusedinfuture
studiesaboutthisspeciesbehaviorwhilemovingthroughfishways
orotherhydraulicstructures.Moreover,ourfindingscorroborate
othertelemetrystudies,focusingondifferentspecies,which
vali-datetheuseofelectromyogramtelemetryasamethodtostudyfish
swimmingphysiologyandrecommenditsusefortheassessment
offishwayefficiencyfortherespectivetargetedspecies.(Almeida
etal.,2007;Brownetal.,2007;Hinchetal.,1996;Øklandetal., 1997;Thorstadetal.,2000).Despitethestrongpotentialofthis
typeoftransmitters,therearesomeissuesthatmustbetakeninto
accountinfutureapplicationsofthismethodology.EMGoutput
and swimmingspeed relationshipssignificantly differedamong
testedbarbels.Therefore,consideringtheresultsfromthisstudy
andpreviousones(Brownetal.,2007;Cookeetal.,2004;Geistetal.,
2002;Thorstadetal.,2000),allfishimplantedwithEMG
transmit-tersshouldbeindividuallycalibratedpriortoreleasetobeableto
determinetheirspecificinstantaneousswimmingspeedwiththe
electromyogramrecords.Also,duringthecalibrationprocedure,
unsteadyswimmingand,consequently,lesshomogeneousCEMG
recordsathigherspeeds(generallyabove1.0m/s)wereobserved
inmostfish.Accordingtoseveralauthorsthathadthesameresults
withdifferentspecies(Almeidaetal.,2007;Thorstadetal.,2000),
this behavior is probably related to a less uniformswimming
behaviorneartheUcrit.Athighspeedsofburstswimming,which
canbefrequentlyrequiredinpoordesigned orunsuitable
fish-ways,theredmusclerecruitmentdecreaseswhiletheintensity
ofwhitemuscleactivityincreases(JainandLauder,1994).Infact,
insomeofthetaggedbarbelstheCEMGsignalsrecordedatthe
highestspeedsdecreased.Therefore,infuturefishwayevaluations
usingthistelemetrymethod,oneshouldhaveinmindthat the
higherswimmingspeedrecordsmaybeunderestimatedwiththis
samplingtechniqueiftheelectrodesareimplantedintheredaxial
musculature.
Learningtousethefavorableflowpatternstoswimduring
fish-wayascenthasbeensuggestedasanexplanationoffishimproved
movementthroughthesefacilities(Laine,1990).Theoretically,in
thisstudy,duringthesuccessivepassagesoffourpoolswith
sim-ilarflowconditionsorbetweentwocompletefishwayascents,it
wasexpectedthatthebarbelswouldacquiresomeknowledgeof
theflowpatternswithintheexperimentalfacilityand,therefore,
wouldchoosemorestableareasthatrequirelessmusculareffort
tonegotiatetheobstacle.Thisassumptionwasnotdemonstrated
inthisstudy,sincethetaggedbarbelsdidnotexhibitsignificant
differencesinswimmingspeedbetweenanyofthefourpoolsand
onlytwoofthempresentedadistinctswimspeedfrequency
dis-tributionbetweenthefirstandsecondfishwayascent.Regardless
ofthis,significantdifferenceswerefoundbetweenthefourpools
whenthecomparedvariablewasthepassagetime.Also,barbels
spentsignificantlylesstimetoperformthesecondcompleteascent
ofthefishwaywhencomparedtothefirstoneandthetimewas
consistentlyreducedinfollowing passes.The“learning”pattern
foundinthisstudywasmostlyreflectedintheknowledgeofhow
togetinandoutofthepoolsandoftheentirefishwayandit
prob-ablytakesmoretime,andattempts,forthefishestolearnhowto
performalessphysiologicallydemandingpath.Theseresultshave
tobelookedcarefullybecauseoftherelativelylowsamplesizeof
fishthatperformedasecondfishwayascentandmoretests,with
aprolongeddurationthanthisoneandinlargerfishways,should
beconductedusingEMGtransmitterstofurtherclarifythisissue.
InastudydevelopedbyCollinsetal.(1962)withsalmonidsinan
experimentalfishway,ittookalmosttwodaysofpassageattempts
beforethefishesstartedtoshowanincreaseinpassagesuccess
rateandadecreaseintheblood-lactatelevel,usedasanindexof
muscularfatigue,afterthefishwayascent.
In thepresentstudy,barbelswithdifferentactivitylevelsin
theattractionpoolalsoobtaineddistinctsuccessinascendingthe
fishway.Fishesthat completelyascendedthefishwayexhibited
higheraverageswimmingspeed valuesinthefirstdownstream
poolthantheonesthatonlyascendedtothemiddleofthe
struc-tureordidnotleavetheattractionpoolduringtheentiretrial,
somehowmakingitpossibletopredictthefishpassagesuccess
basedontheirlevelofactivityinthefishwayentrance.
Nonethe-less,thehydraulicconditions(flowpatterns,water velocityand
flowdischarges)inthevicinityoftheentranceofafishwayarethe
main factordeterminingits’attraction(Larinier, 2002).Ascited
by Scruton et al. (2007),previous workperformed in fishways
determinedthatAtlanticsalmon(SalmosalarL.)mayspend
sev-eraldaysmillingatthefishwayentranceandmakingattemptsto
enteritbeforeproceedingthroughthefishway.Thiscouldmean
that,inthisstudy,barbelsthatdidnotenterthefishwayduringthe
establishedtrialperiod,eventually,mighthaveenteredlater.More
studiesconcerningtheseaspectsoffishwaydesignandoperation,
usingahighernumberoffishanddifferenthydraulicconditions,
shouldbeconductedinordertoclarifythisquestion.
TheEMGtelemetryappliedrevealedthatbarbelshadtoexceed
their criticalswimming speed (defined byMateus et al., 2008)
onlyduringpassagethroughthesubmergedorifices.Although
fish-wayascentwasnottoomuchenergeticallydemandingforbarbels,
observationsofburstswimmingwhilepassingtheorificessuggest
thatenergyusecouldbehighatthesepoints(Ponetal.,2009).
ThishasbeenalsoreportedbyBoothetal.(1997),whofoundthat,
for Atlanticsalmon,theascentofanexperimentalfishwaymay
involveactivitybeyonditsaerobicscope.Theseauthorsdescribed
arapidincreaseinsalmonmuscularactivitytoaboveUcritvalues,
whichremainedelevatedthroughoutthefishwayascent.Previous
studieshaveshownthatasignificantoxygendebtisacquired
dur-ingfishanaerobicactivity(Woodetal.,1983)andtheenergetic
costsofrecovering fromthismaybegreaterthantheiraerobic
scope(Beamish,1978).Thefishwayconfigurationanalyzedinthis
studythroughtheuseofEMGprovedtobeadequateforthe
suc-cessfulpassageofthetargetspeciesconfirmingpreviousstudies
conductedinthesamehydraulicinfrastructure(Silvaetal.,2009,
2011,2012b).However,evensuccessfulpassagethroughafishway
canhavedeleteriouseffectsonfishthatcouldleadtodelayed
mor-talityandnegativelyaffectfishfitnesstothepointofupsettingthe
posteriorsuccessoftheirspawningmigration andreproduction
(Brownetal.,2006;Gowansetal.,2003).Inastudytoevaluatethe
post-fishwaypassagesurvivalandreproductivesuccessofsockeye
salmon(Oncorhynchusnerka),Roscoeetal.(2011)foundthatthe
fishpassagethroughatailraceandaverticalslotfishway
involv-inganaerobicactivity,hadasignificantimpactonthesuccessofthe
speciesspawningmigrationsinceapproximatelyhalfofthe
migrat-ingadultsthat passedupstreamthroughthesestructuresfailed
onreachingspawninggrounds.HinchandBratty(2000),usingthe
sameEMGtechniquetoevaluatethefishwaypassageofsockeye
salmonsfoundthatfishthatspentlongertimeperiods(>10min)
abovetheirUcritcouldnotcompletetheirupstreammigrationeven
afterfishwaynegotiationinoppositiontofishthatspentreduced
periodsunderUcrit,whichweresuccessfulmigrants.Accordingto
Prchalováetal.(2006),severalfreshwatercyprinids(bleakAlburnus
LeuciscusleuciscusL.)usefishpassesnotonlyduringtheirspawning
migrationsbutalsoduringotherperiodsoftheyear.Smaller
bar-belsthantheonesusedinthepresentstudy,forwhichtheUcrit
values differsignificantly(Mateusetal.,2008), canmoreeasily
exceedtheiraerobicscopeandstayforlongerperiodsaboveit,thus
sufferingfrompost-passageeffects,anissuethatfishwaydesigners
andengineersshouldtakeintoaccountwhenimplementingthis
typeofstructures.However,accordingtoPenázetal.(2002)the
proportionofmobilebarbelsisrelativelylowinsmallerandmiddle
sizeclasses,increasingforthelargerclasses,whichmakesthe
lat-teramoreimportantstudyobjectwhendealingwithconnectivity
problems.
This study showed the existence of a positive relationship
betweenbarbels’swimmingspeedandsomehydraulicvariables,
namelythewatervelocity, turbulentkineticenergy, turbulence
intensityand horizontalReynolds shear stress,highlightingthe
importanceoftheseparameterswhenbuildingfishwaysforthis
species. Theswimming speed exhibitedby Iberian barbelswas
lowerincellswithreducedwatervelocityandturbulence,
imply-ingthatintheseareasthebarbelshadtodolessmusculareffort
tomaintaintheirposition(Endersetal.,2007;Pavlovetal.,2000).
Theseconditionswereprimarilyfoundnearthebottomofthe
fish-way,ontherecirculationzone,wherefisheswerefoundtospend
mostoftheirtimeduringthefishwayascent.Severalstudieshave
shownthatrecirculationareasonpool-typefishwayscanbecome
trapsforfishes,drasticallyincreasingthetransittimeineachpool
andthuscompromisingthepassagethroughthefacility(Tarrade
etal.,2008).Despitethefactthatthis phenomenoncouldhave
affectedsomeofthefishestestedinthisstudy,thehighproportion
ofbarbelsthatsuccessfullynegotiatedthefishwayinarelatively
shortperiod,indicatesthatmostofthefishusedtheseareas
essen-tiallyforrestingbeforemovingtowardhighervelocityandmore
turbulentregionsinthevicinityoftheorifices,whereburst
swim-mingwasrequired.Theseanaerobicswimmingefforts,apparently
recruitingfast-glycolytic(white)muscletoascendtheflume,are
verypowerful,butrestandrecoveryperiodsarenecessarytoclear
muscleH+ andlactatebuild-upsandtorestoreglycogenstores,
asshownforrainbowtrout(MilliganandWood,1986).However,
thisstudywasperformedundercontrolledlaboratorialconditions
andthehighpermanencetimeintheserestingareascouldhave
hadothernegativeimpactsonbarbelsifweweredealingwitha
realfishwayinthefield,sincedelayedfishwaypassagescouldalso
resultinincreasedpredation(HinchandBratty,2000;Peliciceand
Agostinho,2008).
Reynoldsshearstress,inparticularitshorizontalcomponent,
wasfoundtobethehydraulicvariablewiththehighestinfluenceon
fishswimmingspeed,suggestingtheimportanceofthisturbulent
descriptoronbarbels’behaviorandphysiologicalresponsewithin
thistypeoffishway.Themaximumshearstressvaluesobtainedin
thepresentstudy(near0.080N/m2)werefarfromthosereported
tocauseinjuriesormortalitiesonfishes(Cadaetal.,2006).
How-ever,accordingtotheresultspresentedinthisstudy,inareaswith
highershearstress,somedisorientationmayhavehappened,due
totheeffectoflargerturbulencevortexsystemsonthefishbody
surface (Odeh et al.,2002), andthe taggedbarbelshadto
per-format ahigher muscularcost tomaintaintheirpositionuntil
movingforwardorbeingdraggeddownstream.Silvaetal.(2011,
2012a,b),whenstudyingtherelationshipofthesehydraulic
vari-ableswithfishtransittimewithinthefishway,foundthatbarbels
tendtospendlesstimeonareaswithhighvelocity,turbulenceand
shearstress.Theseresultssupporttheonesobtainedinthepresent
study,thusimplyingthatduringthefishwayascentbarbelstendto
spendmoretimeinstablezones,avoidingturbulentareaswhere
theenergyexpenditureandmusculareffortwouldincreaseto
val-uesneartheircriticalswimmingspeedandonlymovingtomore
turbulentareaswhentryingtopasstheorificetotheupstream
pool.Otherauthorspresentedsimilarresultsfordifferentspecies
indicatingthatturbulenceandotherassociatedmeasureslikeshear
stresstendtoinducehigherfishswimmingcosts(Cocherelletal.,
2011;Endersetal.,2007;TriticoandCotel,2010).Ontheother
hand,Lupandin(2005)describesanegativerelationshipbetween
turbulenceandswimmingperformance,mostlyreflectedonaloss
ofbalanceandaconsequentdecreaseinfishswimmingspeedwhen
facinghighturbulence, contradicting ourresults. However,this
authoruseda differentmethodology,implementing flow
incre-mentsuntilaturbulencelevelwasreachedthatwashighenough
forthefishtogiveupswimmingandbecarrieddownstream,
mea-suringthehydraulicvalueatthatpoint.Ourstudyprovidesmore
preciseandalmostinstantaneousinformationaboutthemuscular
effort(2saverage)exhibitedbyfishestomaintaintheirswimming
positionin differenthydraulic conditions,aresultonlypossible
withtheuseofelectromyogramtelemetry.
EMGtelemetrytechnologyhasbeen,andcanbe,usedinseveral
fieldsoffishresearchallowingareliableestimateofmuscleactivity
(orswimspeed)andthusenergyexpenditureinfieldexperiments.
Inthisstudy,thistechnologyofferedvaluableanddetailed
infor-mationaboutfishmovements,behaviorandrelationshipwiththe
hydraulicenvironment,whichcanbeusedtoimprovethedesignof
thesestructures,allowingthemigrationandaccesstonewhabitats
offishspecieswithminimumenergyexpenditure.Newfishways
oradaptationsmadetooldonescanbeplannedandadjustedtofit
thecapacityofthetargetspecies.Biologistsandengineersmaybe
abletouseEMGtelemetrytodeterminewhereandhowtorestore
riverenvironmentsinordertofacilitatefishmigration(Hinchetal.,
1996).ThisstudydemonstratedthatradiotransmittedCEMG
sig-nalscanbeusedtodeterminetheswimspeedandthusthebehavior
ofL.bocageiandtoevaluatefishwaydesigninrelationtotheir
effi-ciencyforthisparticularspecies,openinggoodperspectivesforthe
applicabilityofthistechniquetosimilarcyprinids.
Acknowledgements
TheauthorswishtothanktoSaraPinela,SílviaPedroandVera
Canastreirofortheirassistanceduringfishsamplingcampaigns.
Specialthanks aredue tothe Divisionof WaterResources and
Hydraulics Structuresof theNationalLaboratoryfor Civil
Engi-neeringfortheircollaboration,namelyforthecontributioninthe
designoftheexperimentalfishwayandforalltheassistanceduring
thefishtrials.Licensingtocollectthespecimenswasprovidedby
AutoridadeFlorestalNacional(AFN).Thisworkwasfinancially
sup-portedbytheScienceandTechnologyFoundationthroughgrants
to Carlos Alexandre (SFRH/BD/66081/2009) and Paulo Branco
(SFRH/BD/44938/2008)andthroughitspluriannualfunding
pro-gramtotheCentreofOceanography(PEst-OE/MAR/UI0199/2011).
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