Fish and Fisheries. 2019;20:729–747. wileyonlinelibrary.com/journal/faf  | 729© 2019 John Wiley & Sons Ltd

Received:20October2018  |  Revised:14April2019  |  Accepted:16April2019DOI: 10.1111/faf.12373

O R I G I N A L A R T I C L E

Effective monitoring of freshwater fish

Johannes Radinger1  | J. Robert Britton2 | Stephanie M. Carlson3  | Anne E. Magurran4  | Juan Diego Alcaraz‐Hernández1  | Ana Almodóvar5  | Lluís Benejam6  | Carlos Fernández‐Delgado7  | Graciela G. Nicola8  | Francisco J. Oliva‐Paterna9 | Mar Torralva9 | Emili García‐Berthou1

1GRECO,InstituteofAquaticEcology,UniversityofGirona,Girona,Spain2FacultyofScienceandTechnology,BournemouthUniversity,Poole,Dorset,UK3DepartmentofEnvironmentalScience,Policy,andManagement,UniversityofCalifornia, Berkeley, California4CentreforBiologicalDiversity,SchoolofBiology,UniversityofStAndrews,StAndrews,UK5DepartmentofBiodiversity,EcologyandEvolution,ComplutenseUniversityofMadrid,Madrid,Spain6AquaticEcologyGroup,UniversityofVic–CentralUniversityofCatalonia,Vic,Spain7DepartamentodeZoología,FacultaddeCiencias,UniversidaddeCórdoba,Córdoba,Spain8DepartmentofEnvironmentalSciences,UniversityofCastilla‐LaMancha,Toledo,Spain9DepartamentodeZoologíayAntropologíaFísica,UniversidaddeMurcia,Murcia,Spain

CorrespondenceJohannesRadinger,GRECO,InstituteofAquaticEcology,UniversityofGirona,17003Girona,Spain.Email:johannes.radinger@udg.edu

Funding informationGovernmentofCatalonia,Grant/AwardNumber:2014SGR484and2017SGR548;SpanishMinistryofScience,InnovationandUniversities,Grant/AwardNumber:BiodivERsA3‐2015‐26,CGL2015‐69311‐REDT,CGL2016‐80820‐RandPCIN‐2016‐168

AbstractFreshwater ecosystems constitute only a small fraction of the planet's water re‐sources,yetsupportmuchofitsdiversity,withfreshwaterfishaccountingformorespeciesthanbirds,mammals,amphibiansorreptiles.Freshwatersare,however,par‐ticularlyvulnerabletoanthropogenicimpacts,includinghabitatloss,climateandlandusechange,pollutionandbiologicalinvasions.Thisenvironmentaldegradation,com‐binedwithunprecedented ratesof biodiversity change, highlights the importanceof robust and replicableprogrammes tomonitor freshwater fish. Suchmonitoringprogrammes can have diverse aims, including confirming the presence of a singlespecies(e.g.,earlydetectionofalienspecies),trackingchangesintheabundanceofthreatenedspecies,ordocumentinglong‐termtemporalchangesinentirecommuni‐ties.Irrespectiveoftheirmotivation,monitoringprogrammesareonlyfitforpurposeiftheyhaveclearlyarticulatedaimsandcollectdatathatcanmeetthoseaims.Thisreview,therefore,highlightstheimportanceofidentifyingthekeyaimsinmonitor‐ingprogrammesandoutlinesthedifferentmethodsofsamplingfreshwaterfishthatcanbeusedtomeettheseaims.Weemphasizethatinvestigatorsmustaddressis‐suesaroundsamplingdesign,statisticalpower,species’detectability,taxonomyandethicsintheirmonitoringprogrammes.Additionally,programmesmustensurethathigh‐qualitymonitoringdataareproperlycuratedanddepositedinrepositoriesthatwillendure.Throughfosteringimprovedpracticeinfreshwaterfishmonitoring,thisreviewaimstohelpprogrammesimproveunderstandingoftheprocessesthatshapetheEarth'sfreshwaterecosystemsandhelpprotectthesesystemsinfaceofrapidenvironmental change.

K E Y W O R D S

biodiversitytargets,ecologicalmonitoring,environmentalassessment,environmentalmanagement,riversandlakes,samplingdesign

730  |     RADINGER Et Al.

1  | INTRODUC TION

Human‐driven environmental changes continue to raise sub‐stantial concerns for biodiversity conservation and have led tothe development and implementation of many ecological moni‐toringprogrammesaroundtheworld(Nichols&Williams,2006).Theseprogrammesgenerallyaimtounderstandandmanagetheinteractions of environmental change with biodiversity (Fölster,Johnson,Futter,&Wilander,2014).Giventheincreasingserious‐ness of environmental degradation, the need for effective eco‐logical and biodiversitymonitoring programmes has never beenhigher(Lindenmayer&Likens,2010).Freshwaterecosystemsareparticularly imperilled by anthropogenic activities worldwide.Althoughfreshwaterscover lessthan1%oftheearth'ssurface,they support high levels of biodiversity (Dudgeon et al., 2006;Strayer & Dudgeon, 2010). Extinction rates of freshwater taxaareconsiderablyhigherthanterrestrialspecies(Salaetal.,2000),duetoissuesincludinghabitatloss,climateandlandusechange,pollutionandbiological invasions (Ormerod,Dobson,Hildrew,&Townsend,2010;Stenderaetal.,2012).Atapproximately13,000species, freshwaterfishrepresent40%–45%ofglobalfishdiver‐sity(Lévêque,Oberdorff,Paugy,Stiassny,&Tedesco,2008),withthis highly diverse group including some of themost imperilledanimalsontheplanet(Cooke,Paukert,&Hogan,2012).

Freshwaterfishesalsoprovideecosystemservicesofmajoreco‐nomic,nutritional,scientific,historicalandculturalimportance(IUCNFFSG,2015). For example, freshwater andmarine fisheries jointlyconstitute the largest extractive use of wildlife in the world andcontributetooveralleconomicwell‐beingbymeansofexportcom‐moditytrade,tourismandrecreation(Santhanam,2015).Freshwaterfishprovideamajorsourceofproteinforhumansandsupportthelivelihoodsofmanypeople(Holmlund&Hammer,1999),particularlyintheGlobalSouth.However,thereareseriousthreatstothisvalu‐ableresourcerelatedtoover‐exploitationandotheranthropogenicstressors(Allanetal.,2005;deKerckhove,Minns,&Chu,2015).

Thewiderangeofresponsesoffreshwaterfishestoanthropogenicstressorsmakefishvaluableindicatorsforassessingthebiologicalandecologicalintegrityoffreshwatersandtheircatchments(Fausch,Karr,&Yant,1984;Magurranetal.,2018;Schiemer,2000).Thebreadthoffundamental informationonecologyandtaxonomy,combinedwiththeirhighersocietalimportancecomparedtootherfreshwatertaxa,makesfreshwaterfishapopulartargettaxoninassessmentsofeco‐logicalintegrity(Simon&Evans,2017).Correspondingly,freshwaterfishesarecommonlyusedforevaluatingthefunctioningandstatusoffreshwaterecosystemsandhabitatquality.Theseassessments,how‐ever,areonlyasgoodasthedatathatunderpinthem.Forthisreason,effectiveandmeaningfulmonitoringoffishpopulationsandcommu‐nitiesinfreshwaterhabitatsisessential.

Theneedforeffectivemonitoringinecologicalresearchiswell‐recognized and there are many monitoring programmes that haveprovidedimportantscientificadvancesandcrucialinformationforen‐vironmentalpolicy(Lovettetal.,2007).Forexample,freshwaterfishmonitoringhashighlightedchanges inspeciesdiversityandspecies

status in rivers and lakes (e.g., Counihan et al., 2018; Holmgren,Degerman,Petersson,&Bergquist,2016;Wagner,Deweber,Detar,Kristine,&Sweka,2014),playedacentral role infish‐basedassess‐ment systems (e.g., for the EuropeanWater Framework Directive,Pont,Hugueny,&Rogers,2007),andresultedinguidelinesonstan‐dardizedfishsamplingmethods(e.g.,Bonar,Hubert,&Willis,2009).

There remainsa seriesof issuesandknowledgegapswithhowthese programmes are designed and implemented. In particular,freshwater fishmonitoring that has beenpoorly planned and lacksfocus results in ineffectiveprogrammes that rarelymeet theiraims(Lindenmayer&Likens,2009,2010;Marsh&Trenham,2008;Nichols&Williams,2006).Moreover, there is considerabledisparity acrossdevelopedanddevelopingregionsinhowmonitoringschemesareim‐plemented.Thisisanacuteproblem,asdevelopingregionsareoftencharacterized by high levels of fish diversity but limited resourcesfor research (e.g.,Vörösmartyet al., 2010).Wheremonitoringpro‐grammesareinplace,therearealmostinevitablytrade‐offsintempo‐ralandspatialscalesofmeasurement(Pollocketal.,2002),butthesetrade‐offsareoftenpoorlyquantifiedor justified, resulting in long‐termdatalackingstatisticalpower.Finally,thereareinherentissuesoverprogrammesbeingeitherquestiondrivenormandated,withthelatteroftenlackingrigourindesignresultingintheirprovisionofonlycoarse‐levelsummariesofchange(Lindenmayer&Likens,2010).

Inthisreview,weexaminetheseissuesandknowledgegapsandmake recommendations about how they can be addressedwithinmonitoring programmes. Our aim is to foster improved practices

1 Introduction 730

2Historyoffishmonitoring 731

3Aimsofeffectivemonitoring 731

4Differentquestionsleadtodifferentmonitoringapproaches

731

5Samplingandnetworkdesign,andstatisticalmodels 732

6Approachestofishmonitoring 735

6.1Monitoringquestionsversussamplingmethods 735

6.2Capturetechniquesandapplicationwithinmoni‐toringprogrammes

735

6.3Captureandreleasemethods 735

6.4Non‐capturemonitoringtechniques 737

6.5Anglers’dataanddatamining 737

6.6Complementarityofcaptureandnon‐capturemethods

738

7Majorchallengesinfishmonitoring 738

7.1 Detectability 738

7.2Taxonomy 738

7.3Economiccosts 739

7.4Fishwelfareandethicsinmonitoring 739

8Managementofmonitoringdata 740

9Conclusions 740

Acknowledgments 740

References 741

     |  731RADINGER Et Al.

by:(a)summarizingkeyquestionsthatmonitoringcanaddresswhenaimsareclear,andtheapproach is rigorous (Sections3and4); (b)synthesizingissuesrelatedtosamplingdesignandstatisticalmodels,andindicatinghowtheymightbeovercome(Section5);(c)review‐ing different monitoring and sampling approaches (Section 6); (d)considering challenges related to species’ detectability, taxonomy,economicalcostsandethics(Section7);and(e)discussingtheimpor‐tanceoftheappropriatemanagementofmonitoringdata(Section8).

2  | HISTORY OF FISH MONITORING

Thelonghistoryofmonitoringprogrammesisreflectedinthescien‐tificliterature(FigureS1.1).Early,thoughpresumablylesssystematic,efforts in freshwater fishmonitoring recorded temporal changes infisheries,suchasreportsofAtlanticsalmon(Salmo salar,Salmonidae)declinesinacentralEuropeanriverthatdatebacktothe18thcentury(reviewedbyWolter,2015).The20thcenturymarkedashifttowardssystematicsamplingwiththemajorityoffishmonitoringprogrammesbeingestablishedbefore1979(Mihoubetal.,2017).Despitethisandin contrast toother taxonomicgroups suchasbirds,mammals andmanyplants,freshwaterfisharegenerallyunder‐representedincon‐temporarybiodiversitystudiesandmonitoringprogrammes(Mihoubet al., 2017; Troudet, Grandcolas, Blin, Vignes‐Lebbe, & Legendre,2017).Thisunderrepresentationoffish,despitetheirhighdiversity,mightbeexplainedpartlybythefactthattheyoccurinaquaticen‐vironments.Thus,incontrasttomanyterrestrialbiota,whichcanbemonitored by visual observations and where community scientists(also known as citizen scientists) can be easily recruited (Thomas,1996), fish require more specialized sampling methods. However,onefeaturesharedwithothertaxa isthatthespatialextentoffishmonitoring ishighlybiased,beingconcentratedintheGlobalNorth(Figure1).Freshwaterecosystems(e.g.,lacustrineandfluvialhabitats)are also generally neglected in fish monitoring programmes, com‐paredtothemarineenvironments(Figure1).Afurther issueisthatevenwhenfreshwaterfisharemonitored,theresultingdataareoftennotpublishedorelectronicallyarchived,andthusareofteninaccessi‐bletothebroaderscientificcommunity(Lindenmayer&Likens,2009;Revenga,Campbell,Abell,Villiers,&Bryer,2005).

3  | AIMS OF EFFEC TIVE MONITORING

Asit isnowwidelyrecognized,ecologicalcommunitiesexperiencecontinuoustemporalturnover,thatischangeinspeciescompositionand abundances (e.g., Darwin, 1859;MacArthur &Wilson, 1967).Somedegreeoftemporalturnoverisnecessarytomaintainecosys‐temfunctionsandproperties.However,therateoftemporalturno‐verincontemporaryassemblagesexceedsthebaselinepredictedbyecologicaltheory(Dornelasetal.,2014).Consequently,theoverallgoalineffectivemonitoringoffreshwaterfishshouldnotbelimitedtodocumentingchangeperse,butshouldalsoaddressthedriversoftheobservedchange(therebyidentifyingpotentialremedies).

Thereareanumberofdefinitionsofmonitoringinconservation,ecologicalandaquaticcontexts(TableS1.1).Here,wedefinefresh‐water fish monitoring as repeated, field‐based measurements of fish that are collected in a systematic manner, allowing the poten‐tial detection of important shifts at population or community lev‐els.Therefore,effectivemonitoringrequiresaclearsetofspecificobjectives linkedtotheoverallgoalofdetectingsystemicshifts infishpopulationsorcommunitiesovertimeandspace,andsoshouldutilizemethodologiesandsamplingeffortthatprovidethedataandstatisticalpowersufficienttomeettheseobjectives.

4  | DIFFERENT QUESTIONS LE AD TO DIFFERENT MONITORING APPROACHES

Monitoringprogrammesneedarigorousdesignandprotocolforcol‐lection of data over a sufficiently long period to ensure sufficientstatisticalpowertodetecttrendsorchangesandtoenablethean‐swering of themotivating questions (Lindenmayer & Likens, 2010;Nichols&Williams, 2006). Irrespectiveof themotivatingquestion,freshwaterfishmonitoringshouldgenerallyhelptoadvanceecosys‐temunderstandingandprovide informationneeded to identifypo‐tentialremedies,requiringthedetectionofsignificantchangesatthecommunitylevel(e.g.,quantifyingtrendsinspeciesrichness,temporalα‐andβ‐diversity,functionaldiversity,foodwebstructure),and/oratthepopulation level (e.g., quantifying trends inpopulation size anddynamics,abundanceofkeystone,threatenedornon‐nativespecies,geneticdiversity,speciesranges,fisheriesstocks,sizeandagestruc‐ture,behaviour,phenology,growth,shape,and/orcondition).Anex‐ceptiontothismightbeinmandated‐monitoringprogrammeswherehighlyspecificdata(e.g.,onspeciespresence,abundance,and/oragestructure)arecomparedagainstpredeterminedstandards(Alexander,2008; Hellawell, 1991; Hurford, 2010), such as in the WaterFrameworkDirectiveoftheEuropeanUnion(Birketal.,2012). Inarestorationcontext,monitoringoftenaimsatassessingthesuccessofimplementedmeasures(Kershner,1997).Thereby,monitoringisnotastand‐aloneactivity;itcontributestoconservation‐orientedscienceandisusedtoinformstructureddecision‐makingprocessesinconser‐vationmanagement(Nichols&Williams,2006).

It is the question(s) that determine the design of amonitoringprogramme.Somequestionscanbeaddressedwithspecies‐specificpresence‐onlydata,whileothersmightrequiresamplingofanentirecommunity (Table1).The lattercasemayutilizearangeofcapturemethods(Zale,Parrish,&Sutton,2012)thatcan,inturn,helpassessthespatialbehaviour,trophicecologyandgeneticcharacteristicsofindividuals(Lucas&Baras,2000;Lundqvistetal.,2010).Alternativesampling methods include more recent approaches such as com‐munityscienceand theuseof socialmedia/crowd‐sourcedscience(Section6).Thedataneedsassociatedwithasuiteofkeymonitoringquestionsare summarized inTable1.Westress the importanceofprogrammesclearlyarticulatingtheirquestionsasthisensuresthatthesamplingdesigncangeneratethedatarequiredtoanswerthem.As aminimum, there shouldbe identificationofwhat needs to be

732  |     RADINGER Et Al.

measured(e.g.,fishabundance,fishattributes),thespatialandtempo‐ralscopeoftheprogramme(e.g.,duration,scale;cf.Dixon&Chiswell,1996);thecriteriaforreliability(e.g.,precision,power);andtheprac‐ticalconstraints(e.g.,humanresources,costs,socialconflicts).

5  | SAMPLING AND NET WORK DESIGN, AND STATISTIC AL MODEL S

Samplingdesignrelatestothetemporalfrequencyofsamplingwithinadesignednetworkthatcomprisesaseriesofspatiallysegregatedsites.Assuch,decisionsneedtobemaderegardinghowtoallocatemonitor‐ingeffortwithinandamongstyears,andacrosssites(Larsen,Kincaid,Jacobs,&Urquhart,2001).Twomajorprinciples,theavoidanceofbias

intheselectionprocedureandachievementofhighprecision,shouldunderliethedesign(Crawford,1997).Asamplingdesigncanbebasedon probabilistic or non‐probabilistic methods. Probabilistic designsinclude simple random sampling, systematic sampling and stratifiedrandomsampling,withthelattertwobeingmoreappropriateforhet‐erogeneous, hierarchically structuredaquatic environments, suchasriverdrainages(Lowe,Likens,&Power,2006;Thorp,Thoms,&Delong,2006). However, in fishmonitoring, sample sites are frequently se‐lectednon‐probabilistically,oftenbasedonjudgmentorconvenience(Pope,Lochmann,&Young,2010;Wilde&Fisher,1996).Irrespectiveofthis,decisionsonthedesignoftheprogrammeshouldbebasedonaprioridefinedstatisticalmodelsthatcanreliablyanswerthequestionsmotivatingthemonitoringprogramme,suchasthoserelatedtoquan‐tifyingcommunitystructure,speciesabundanceorotherpopulation

F I G U R E 1  Overviewoffishmonitoringprogrammesacrossglobalregions(a),taxonomicorders(b)andbiotopetypes(c)basedonrecordsofthetaxonomicgroupOsteichthyes(n=543)intheGlobalPopulationDynamicsDatabase(GPDD,version2.0,released2010,www.imperial.ac.uk/cpb/gpdd2,NERCCentreforPopulationBiology,ImperialCollege,2010).Note:Theapparentlackofmonitoringin,forexample,AfricaandAustraliamightreflectalimitationofthedatabaseratherthananactuallackofmonitoring[Colourfigurecanbeviewedat wileyonlinelibrary.com]

Number of �sh monitorings per global region

0 1–5 5–10 10–100 >100Record of �sh monitoring scheme

Aulopiformes

Tetraodontiformes

Zeiformes

Cypriniformes

Lophiiformes

Anguilliformes

Gasterosteiformes

Scorpaeniformes

Pleuronectiformes

Clupeiformes

Perciformes

Gadiformes

Salmoniformes

0 5 10 15 20 25 30 35 %

n = 1

n = 1

n = 2

n = 3

n = 3

n = 5

n = 7

n = 12

n = 56

n = 78

n = 82

n = 102

n = 191

Coastal

Fluvial

Lacustrine

Tidal/Intertidal

Marine

0 15 30 45 60 75 %

n = 3

n = 15

n = 18

n = 98

n = 409

Freshwater (n = 33)

(c)

(b)

(a)

     |  733RADINGER Et Al.

TAB

LE 1

 Overviewofkeyquestionsinfishmonitoringprograms,associateddataneedsandmostapplicablesamplingmethods[Colourtablecanbeviewedatwileyonlinelibrary.com]

Not

e: Samplingmethod:1electrofishing,2netting,3trapping,4telemetry(e.g.,acoustic,radioorpassiveintegratedtranspondertags),5mark–recapture,6environmentalDNA,7hydroacousticassess‐

ment,8anglercatchstatistics,9datamining,10communityscience.‐/orange=no,yellow=maybe,green=yes,na=notapplicable.

734  |     RADINGER Et Al.

parameters(e.g.,agestructure).Thesequestionsrequireconsiderationduringdesignphasesaswellasadditionalresourcesandtime,separatefromthemonitoringprogrammeitself,forcompletion.

Wheretheaimsaretodetectchangesrelatedto(local)manage‐mentactionssuchashabitatrestoration,orto impactassessment,before‐after‐control‐impact (BACI) designs are frequently used(Osenberg,Bolker,White,St.Mary,&Shima,2006;Stewart‐Oaten&Bence,2001;Thiault,Kernaléguen,Osenberg,&Claudet,2017).Here, a prioripoweranalyses(Legg&Nagy,2006;Marsh&Trenham,2008;Maxwell& Jennings, 2005; Peterman, 1990) can guide theestimation of the minimum number of samples needed to detectacertaineffect size (orminimumdetectabledifference)accordingtoadesiredlevelofsignificance(Peterman,1990;Steidl,Hayes,&Schauber,1997).

However, as fish monitoring programmes are typically under‐taken to detect temporal changes in populations over potentiallylargerscales(Cowx,Harvey,Noble,&Nunn,2009),statisticalcon‐trolandreplicationdesignsareoftenunfeasible (Carpenter,Frost,Heisey,&Kratz,1989;Hargrove&Pickering,1992;Schindler,1998;Turner,Gardner,&O'Neill,2001).AdvancedBayesian(hierarchical)models(Hobbs&Hooten,2015)offerusefulalternatives,especiallywhenworkingwithimperfectdatasetsand/oruncertaintyassoci‐atedwithsamplingandobservation,as it isoften thecase in fishmonitoring.Forexample,Wengeret al. (2017) appliedaBayesianapproach to predict the viability of multiple (potentially isolated)populationsofLahontancutthroattrout(Oncorhynchus clarkii hen‐shawi,Salmonidae); thisapproachenabledpredictions tobemadeinminimally sampled or even un‐sampled populations. Other ap‐plications of Bayesianmodels to analysemonitoring data includeestimationsofoccupancyandrichnessoffishwhileaccountingforimperfectdetection(Bayley&Peterson,2001;Coggins,Bacheler,&Gwinn,2014)andforrelatingenvironmentaldriverstostreamfishpopulationdynamics(Letcheretal.,2015;Wheeleretal.,2018).

Thespatial structureofdendriticnetworks,and theirassociatedconnectivityanddirectionality,makesriversystemsparticularlychal‐lengingformonitoring.Theeffectofspatialvariabilitycanbereducedby stratified random sampling, that is the proportional sampling ofstratathatrepresentdifferenthabitatunits(Downesetal.,2002)andiswidelyused inaquaticecosystems (Dukerschein,Bartels, Ickes,&Pearson,2011;Haxton,2011;Wilde&Fisher,1996).Morerecently,SpatialStreamNetwork(SSN)modelshavebeendevelopedtobettercapturethecontinuousnatureofrivers(Fausch,Torgersen,Baxter,&Li,2002)andtoaccountforthespatiallyautocorrelatedrelationshipsbetweenlocationswithinastreamnetwork(Isaaketal.,2014).Forex‐ample, Isaak,VerHoef,Peterson,Horan,andNagel (2017)analyseda large fishdensitydata setusingSSNmodels toobtainpopulationestimatesfortroutspeciesfrom108sitesina735kmrivernetwork.TheSSNmethodology is accessiblevia the statistical tools “STARS”(Peterson&VerHoef,2014)and“SSN”(VerHoef,Peterson,Clifford,&Shah,2014).

Inasystematicsamplingdesign,thefirstsamplesite ischosenrandomlyandallsubsequentsamplesareregularlyplacedinspaceortime(Conroy&Carroll,2009;Quinn&Keough,2002).Asystem‐atic design is useful when investigating effects of environmentalgradients.Arecentdevelopmentinthiscontext istheGeneralizedRandom Tessellation Stratified (GRTS) design (Stevens & Olsen,2003, 2004), available from the statistical package “spsurvey”(Kincaid & Olsen, 2016). GRTS allows design‐based inferences toentire areas based on spatially balanced samples, that is a spatialdistribution of sample locations that balances the advantages ofsimpleorstratifiedrandomsamplesorsystematicsamples(Larsen,Olsen,&Stevens,2008).GRTShasbeenevaluatedasreliableandcost‐effective,forexample,formonitoringNorthAmericansalmo‐nids(Gallagher,Wright,Collins,&Adams,2010).

Theadaptiveapproach(Box1)arguesthatthesamplingdesignshould be re‐evaluated and re‐designed as necessary as data are

Box 1 Adaptive monitoringThereisoftenhighuncertaintyandcomplexityinthedriversoffishcommunitychangethatcanrangefromglobalenvironmentalchange(e.g., climate change;Graham&Harrod, 2009;Radinger et al., 2016) tomore local issues (e.g., altered flow regimes;Harby,Olivier,Merigoux,&Malet,2007).Monitoringprogrammesmustbecapableofprovidingdatasuitableforthecontinuedmanagementoftheresources(Polasky,Carpenter,Folke,&Keeler,2011).Theinformeddecision‐makingprocessofadaptivemonitoring(sensuLindenmayer&Likens,2009)enablesmonitoringprogrammestoevolve inresponsetonewquestions, information,situationsorconditionsorthedevelopmentofnewprotocols(Lindenmayer,Likens,Haywood,&Miezis,2011).Adaptivemonitoringisconsideredalong‐termactivitycloselyrelatedtoscientificresearchandmanagement.Theultimateaimofanyadaptivemonitoringprogrammeistodemonstratethatnewinsightsgainedthroughitsapplicationwillimprovemanagementpractices(Lindenmayeretal.,2011),potentiallyleadingtoincreasesintheeffectivenessofmonitoringforconservation.Anexampleof adaptivemonitoring is outlinedbyFölster et al. (2014) for Swedish freshwaters.At theoutset, theearlynaturalistsmeasuredspecificandlocalizednaturalphenomenasuchastherelationshipbetweenmacrophytesandlakewaterchemistry(Lohammar,1938).However,thescopeofthefreshwatermonitoringprogrammeinSwedenandthenumberofmonitoredsitesincreasedalongwiththeemergenceofnewchallengesrelatedto,forexample,eutrophicationinthe1960s,acidraininthe1970sandtheEUWaterFrameworkDirectivein2000.Today,theprogrammeconsistsofregularlong‐termmonitoringofwaterchemistryandbiodiversity(includingfreshwa‐terfish)in114streamsand110lakes(Fölsteretal.,2014).Thisexamplenotonlyillustratesthevalueofadaptivemonitoringbyprovidinglong‐termdatatounderstandandovercomemanyoftheemergingenvironmentalproblems,butalsoemphasizesitspotentialtoinves‐tigatefuturechallenges,forexamplerelatedtoclimatechange,testingresiliencetheory,orpredictingregimeshiftsandtippingpoints.

     |  735RADINGER Et Al.

gatheredand theirvariabilityanalysed.Ananalysisof thecompo‐nentsofvarianceandtheir influenceontrenddetectioncapabilitycan help in preparing design‐efficient trend monitoring networks(Larsenetal.,2001).Thisensuresthatchangesinthechemical,phys‐icalorbiologicalconditionsareaccountedforinthesamplingdesign(Bucklandetal.,2012;Strobl&Robillard,2008).

6  | APPROACHES TO FISH MONITORING

6.1 | Monitoring questions versus sampling methods

Thenumeroussamplingmethodsthatcanbeutilizedforfishmoni‐toring, including capture andnon‐capture techniqueshavebeenextensivelyreviewed(e.g.,Bonaretal.,2009;Joy,David,&Lake,2013; Zale et al., 2012). Capture methods involve the physicalremoval of fish from thewater to enable species identification,andthecollectionofbiometricdata(e.g.,length,weight)andhardstructures (e.g., scales) for ageing the fish to determine popula‐tion demographics and dynamics. The most common methodsavailableforcapturingfreshwaterfishincludeelectrofishing,net‐tingandtrapping(Bonaretal.,2009).Non‐capturemethods(e.g.,hydroacoustic surveys) canprovidedata complementary to cap‐ture techniques. They can also be usedwhere capturemethodslack sufficient power to provide robust estimates of populationabundances (Hughes, 1998; Lyons, 1998).However, a featureofsomenon‐capturemethods is their taxonomic ambiguity due toeithertheirlackoffishcapture(Boswell,Wilson,&Wilson,2007)(Section 6.4) or through erroneous identification of specimens(Section7.2).

The application of a sampling method in monitoring mightdiffer markedly according to the programme's aims. For exam‐ple, electrofishing can be applied within point abundance sam‐plingdesignsthatcanbeeffectiveformonitoringthedielactivityof (small) fishes (reviewed by Copp, 2010) or the status of rarespecies (e.g., thecriticallyendangeredEuropeaneel,Anguilla an‐guilla,Anguillidae;Laffaille,Briand,Fatin,Lafage,&Lasne,2005).However,capturingfishinlongerriverreachesusingelectrofishingmightbemoresuitablewherethemonitoringaimistoassessbio‐logical/ecologicalintegrity,asbioticindicesrequiredataatmulti‐pleorganizationlevels,fromsizestructuretoassemblagerichness(e.g.,Noble,Cowx,Goffaux,&Kestemont,2007;Pontetal.,2007;Schmutz,Kaufmann,Vogel, Jungwirth,&Muhar,2000),often inconjunctionwithdataonhabitatquality (e.g.,VanLiefferingeetal.,2010;Milner,Wyatt,&Broad,1998).

6.2 | Capture techniques and application within monitoring programmes

Thechallengeofensuringthatcapturemethodsarefitforpurpose,suchasevaluatingthecompositionofanassemblage(detailsinBox2;e.g.,Zaleetal.,2012)hasresultedinaseriesofstandardizedpro‐tocolsbeingmadeavailableforsampling inlandfishpopulations inmanyareasoftheworld,includingEurope,NorthAmericaandNew

Zealand(Bonaretal.,2009;CEN,2003,2006;Joyetal.,2013;TableS4.1).Standardizationnotonlyreferstotheequipmentusedorhowit isused,butalso to thetimingofsampling, thehabitats thataresampled,andeffortapplied(Bonar,Fehmi,&Mercado‐Silva,2011).Standardizing the collection and reportingof fishmonitoringdataoffersmany advantages including an improved ability to comparedata across regions or time, improved communication across po‐liticalboundaries,andthecontrolofbiasassociatedwithdifferentsampling techniques (Cooke et al., 2016). Standardization in fishsamplinghasbeenconsideredanimportantstepforwardinmanag‐inglong‐termdataandassessingefficacyoflargespatialscaleman‐agementstrategies(Bonaretal.,2017).Thisisofparticularrelevanceinmonitoringprogrammeswheremany researchers combinedatasetstojointlyaddressquestionsovertimeandspace.Foracompre‐hensive overviewon standardisation of fish sampling across sam‐plinggearsandaquaticenvironments,seeBonaretal.(2009).

Twofundamentalconceptshaveemergedinrelationtotheap‐plicationofcapturetechniquesandprotocolstofishmonitoring:theimportanceofsamplingdesign (discussedearlier inSection5)andresponsedesign(Stevens&Urquhart,2000).

Responsedesignincorporatesdecisionsabouthowtomeasurethefishcommunityandpopulationmetricswithaccuracyandpre‐cision(Pollocketal.,2002).Forexample,whereassessmentsofagestructure, growth rates and recruitment are required, then deci‐sionsareneededontheageingmethod,suchaswhethertorelyonlength–frequencyanalysesorcollecthardstructures,suchasscales,fromcaptured fishes (e.g.,Hamidan&Britton,2015). If scalesarecollected,thendecisionsareneededregardinghowmanyindividualfishneedtobesampledandoverwhatsizerange(Busst&Britton,2014). In addition,where hard structures are being used for age‐ing, the frequency of annulus formationmight need validating tomaximizeaccuracy(Beamish&McFarlane,1983),requiringregularsamplingthroughouttheyearormark–recapturemethods(Britton,Harper,&Oyugi,2010;Chisnall&Kalish,1993).Scalesamplesforfishageing,andtissuesamplesforgeneticandstableisotopeanal‐yses, can be collected from fish captured by anglers to comple‐menton‐goingmonitoring(GutmannRoberts,Bašić,AmatTrigo,&Britton,2017).

6.3 | Capture and release methods

Itisoftendesirabletoreleasecapturedfish,unharmed,tothesiteofcapture,withoutfurther intervention.However,attachingtrackingdevicesormarkingfish,priortorelease,cansubstantially increasethe amount of information obtained. For example, biotelemetryusingacoustic,radioorpassiveintegratedtranspondertags(Cooke,Woodley, Brad Eppard, Brown, & Nielsen, 2011; Thiem, Taylor,McConnachie,Binder,&Cooke,2011)canrevealindividualvariabil‐ity inmovementsandbehaviourswithinandbetweenpopulations(Lucas&Batley,1996;Radinger&Wolter,2014),elucidatepopula‐tionmixing and gene flow (Huey, Schmidt, Balcombe,Marshall, &Hughes,2011),assesstheeffectsofconnectivityandhabitatfrag‐mentationonriver fishes (Capraetal.,2017;Linetal.,2018),and

736  |     RADINGER Et Al.

Box 2 Sampling effort and biodiversity estimationDecisionsaboutthespatialextentanddurationofsamplinghaveimportantimplications.Ifthegoalistoquantifyanattributeofapopula‐tionofinterest,then,allotherthingsbeingequal,estimatesofabundancewillscalepredictablywitheffort.Therearearangeofstatisticaltechniques,suchasremovalsampling(Southwood&Henderson,2000),thatcanbeusedtoestimatepopulationsizeand/ortoensurethateffortisadequatefortheintendedpurpose.Itisrelativelystraightforward,therefore,tocomputetrendsforsinglepopulations.If,ontheotherhand,theaimistoquantifycompositionalturnover(temporalβ‐diversity),ortocalculateametricofα‐diversity,suchasassemblagerichness,itisessentialthatanytemporalorspatialcomparisonstakeaccountoftheinherentunevennessofecologicalas‐semblages.Althoughthenumberofindividuals(acrossallspecies)willtypicallyincreaselinearlyifanassemblageissampledoveralongertimeperiod,ortheareasampledisincreased,thespeciesaccumulationcurvewillgraduallyflatten(Figure2).Asaresult,anymetricsthateitherexplicitlyorimplicitlydependonrichnesscannotbescaledbysimplemultiplicationordivision.Speciesrichnessisthemetricmostobviouslyinfluencedbythis,butmostbiodiversityindices,including,forexample,theBerger‐Parkerdominancemetric(Magurran,2004,2011;Magurran&McGill,2011)andJaccardsimilarity(Baselga,2010),arealsoaffected.Fortunately,therearestatisticalsolutionstothisproblem.Rarefactionisthetraditionalwayofmakingfaircomparisonsacrossassem‐blagesorofcommunitydiversityoverspaceortime(Gotelli&Colwell,2001,2011).Inessence,thesamples(orassemblages)arerarefiedtothesmallestcommonsamplingeffort.Rarefactioncanbecomputedinrelationtotheminimumnumberofindividualssampledortothesmallestnumberofsamplingunits.Whilemostrarefactionanalysesfocusonspeciesrichness,inprinciplemanydifferentbiodiversitymetricscanberarefied.Inthecaseoftemporalorspatialβ‐diversitycomparisons,theinvestigatorshouldusesample‐basedrarefactionasthisautomaticallyretainstheidentityofthespeciesinvolved.Arecentinnovationistoextrapolatetothelargestsamplesizeratherthanrarefytothesmallestone(Chaoetal.,2014;Hsieh,Ma,&Chao,2016).Rarefactioncanalsobeusedtomakeinformedcomparisonsaboutcommunitystructureandcompositionusingnullmodelapproaches(Cayuela&Gotelli,2014;Cayuela,Gotelli,&Colwell,2015).Insummarythen,anycomputationoftrendsincommunityα‐diversityorβ‐diversityshouldeitherbebasedonsamplingthathasbeenrigor‐ouslystandardizedordatathathavebeenstatisticallystandardized(byrarefactionorsimilar)—seeFigure2foranexample.

F I G U R E 2   Illustrationofthevariationofthenumberofspecies(speciesrichness)andnumericalabundancewithsamplingeffort.ThedataarefortworiversitesinTrinidad(top(a)LowerAripo,bottom(b)Maracas,sampledfourtimesannuallyforfiveyears.ThedataaredescribedinMagurranetal.(2018).Ineachcase,thespecies(andnumericalabundance)accumulationcurvesareconstructedbyrandomlyshufflingthetemporalorderofthesamplesa1,000times.Theopenpointsrepresentthemedianvalueoftherandomisedaccumulationcurves;their95%confidencelimits(0.025and0.975quantiles)arealsoshown(speciesrichness‐leftcolumn;numericalabundance‐rightcolumn)[Colourfigurecanbeviewedatwileyonlinelibrary.com]

20S

peci

es r

ichn

ess

(a)

(b)

- Lower Aripo

Num

eric

al a

bund

ance

05

1015

05

1015

20S

peci

es r

ichn

ess

- Maracas

02,

500

5,00

07,

500

02,

500

5,00

07,

500

Num

eric

al a

bund

ance

5 10 15 5 10 15Number of samples

     |  737RADINGER Et Al.

helpevaluatemanagementunitsforfisheriesorconservation(Funk,McKay,Hohenlohe,&Allendorf,2012).

Mark–recapturestudiescanalsostronglycomplementfishmon‐itoringbyprovidingalternativeestimatesofpopulationsizeandfishages(Hameletal.,2015;Sassetal.,2010).Theycanalsorevealtheextentofmigrationsofindividualfishbetweenhabitatswithinspe‐cificpopulations(Sandlund,Museth,&Øistad,2016).

6.4 | Non‐capture monitoring techniques

Non‐capturemonitoringmethods to complement capturedata in‐clude environmental DNA and hydroacoustic assessments. Thesemethods are often appliedwithinmonitoring programmes to pro‐videdataondifferentcomponentsofthecommunityorpopulationandareespeciallyusefulforlargerwaterbodieswherecapturetech‐niquesareoftendifficulttoapplyorareinefficient.

EnvironmentalDNA(“eDNA”hereafter)isbasedonthepresenceDNAoffishesinwatersamplesoriginatingfrommucusandfaeces,thesloughingoffofcellsfromtheirgutlining,andthedecompositionofdeadindividuals(Davisonetal.,2016;Jerde,Mahon,Chadderton,&Lodge,2011;Turner,Uy,&Everhart,2015).DNAisextractedfromwatersamples,andpolymerasechainreactionusedinconjunctionwith species‐specific genetic markers to amplify DNA fragmentstoindicatethepresenceoftargetspecies(Turneretal.,2015).Themethodisincreasinglybeingappliedtothemonitoringoffreshwa‐terspecies(FigureS1.1),includingthoseofconservationimportance(Takahara,Minamoto,Yamanaka,Doi,&Kawabata,2012;Thomsenetal.,2012).

TherearetwobasicwaysthateDNAcanbeappliedinafishmoni‐toringprogramme.Watersamplescanbeanalysedtodetectthepres‐enceofaspecificspeciesorcanbescreenedforwholecommunitiesoforganismsusing“eDNAmetabarcoding”(Hänflingetal.,2016;LawsonHandley,2015).Recentrefinementshave improvedthereliabilityofspecies’detection(Hänflingetal.,2016),butsomequestionsremain,forexample,onfactorsaffectingtherateofDNAbreakdownintheenvironment(Barnesetal.,2014).However,thenon‐detectionofspe‐cies‐specificDNAfragmentsinasampleofriverwaterdoesnotnec‐essarily implytheabsenceofthetargetspecies,nordoesapositivesignalnecessarilyimplythatthespeciesispresent,aseDNAcouldhavebeentransportedfromupstreamareas(Roussel,Paillisson,Tréguier,&Petit,2015).Nevertheless,asrefinementsinthetechniquecontinue,itshouldincreasinglyprovideastrongcomplementtocapturemethods,especiallyinregionswhereknowledgeonthespecieslikelytobepres‐entisavailable.AlthoughissuesoverthereliabilityofeDNAtoprovideestimatesofabundancearebeingaddressed,theyremainhighlychal‐lenging(Lacoursière‐Roussel,Côté,Leclerc,&Bernatchez,2016).OneimportantconsiderationwillbetheintegrationofdatacollectedusingtraditionalmethodswithinferencesaboutfishcommunitiesobtainedusingeDNA(seeSection6.6below).

Hydroacousticassessmentsinvolvetheapplicationofanacous‐ticbeamfromatransducerthroughthewater.Anyfishwithinthebeamreturnsasignal,withthetargetstrengthofthereturningsignalindicatingtherelativesizeofthefish.Whilethemethodgenerates

dataonfishdensity,thereishightaxonomicambiguityintermsofspeciespresent,withnobiometricdatacollected (other thancon‐versionoftargetstrengthstoapproximatefishlengths;Boswelletal.,2007).Nevertheless,hydroacousticassessmentshavebeenusedextensively for fishmonitoring,especially in lakeswheresamplingstrategieshavebeendeveloped(e.g.,Guillard&Vergès,2007),withtarget strengths related to species‐specific attributes to increaseknowledgeoncommunitycomposition(Frouzova,Kubecka,Balk,&Frouz,2005).Inlowlandrivers,suchastheRiverThamesandRiverTrentinEngland,mobilehydroacoustictechniqueshavebeenappliedtomonitorthespatialandtemporaldistributionsoffishcommunities(Hughes,1998;Lyons,1998).Themethodhasalsobeenappliedtoassessingthestatusofendangeredfishes(Zhangetal.,2009).

6.5 | Anglers’ data and data mining

Statisticsonanglercatchratesandspeciescompositionhavebeenapplied to themonitoringof fish community compositionof largelowlandriverswhereotherfishcapturemethodsareeitherdifficulttoapplyorinefficient(Jones,Robson,Lakkis,&Kressel,1995).Forexample, in theRiverTrent, England, angler catch statisticsmoni‐tored changes in the fish assemblage in relation to improvementsin water quality (Cooper &Wheatley, 1981; Cowx & Broughton,1986).More recently,catchstatistics from individualanglerswereused to assess the population status of mahseer fishes (Tor spp.,Cyprinidae)intheRiverCauvery,India(Pinder,Raghavan,&Britton,2015a,2015b).Anissuewithangler‐baseddataisthattheytendtobebiasedforspecificspeciesandsizeranges(AmatTrigo,GutmannRoberts,&Britton,2017).

Data mining, where spatial and temporal data on species aregathered through information available from online sources, is adifferentnon‐capturetechniqueformonitoringchangesinthedis‐tribution of species. Databases including the Global BiodiversityInformation Facility (GBIF; www.gbif.org/), the Global PopulationDynamics Database (GPDD;www.imperial.ac.uk/cpb/gpdd2/secure/login.aspx),orVertNet.orgenableuserstoaccessglobaldistribu‐tion recordsof species via directed searches that provide recordswith locationcoordinates forusewithinGIS.TheGPDDalsopro‐videsdataonpopulationdynamics,ratherthanjustdistributiondata.TheFishBasedatabase(Froese&Pauly,2018)providesspecies‐levelinformationgatheredfromtheliterature,includingoccurrencesanda wide range of ecological data.

Analternativemethodtousingtheseonlinedatabasesismonitor‐ing thedistributionof fishesvia community science,particularly viasocialmediaplatforms.Indeed,theapplicationofcommunityscienceandcrowdsourcingtothecollectionofbiologicaldatais increasinglyfrequent(e.g.,www.inaturalist.org,FigureS1.1),thankstomanysmart‐phones now having GPS, high‐resolution cameras, and continuousInternet connection (Bik &Goldstein, 2013; DiMinin, Tenkanen, &Toivonen, 2015). For example, for monitoring distributions of non‐nativefish,anumberofsmartphone“apps”areavailable,withthesegenerally enabling the user to send a geo‐referenced image of thespeciestoaspecificorganizationforvalidationandrecording.Current

738  |     RADINGER Et Al.

examplesinclude“That'sInvasive”(http://www.rinse‐europe.eu/resources/smartphone‐apps/) and “AquaInvaders” (http://naturelocator.org/aquainvaders.html).Bothofthese“apps”alsoprovideuserswithinformationandimagesonspecificinvaderstofacilitatetheiridentifi‐cationofspecies.Venturelli,Hyder,andSkov(2017)haverecentlyre‐viewedtheopportunitiesandchallengesassociatedwithangler“apps.”

Datacanalsobesourcedfromuser‐generatedcontentonvar‐ioussocialmediaplatforms(DiMininetal.,2015).Bydatamining,thesenon‐biologicalsources,suchasviasearchesofspecificso‐cialmediasources(e.g.,https://www.youtube.com/),recreationalfisheriesforumsandblogs,andnews‐mediachannels,fishdistri‐butionanddispersaldatacanbegenerated.Forexample,thisap‐proachhasbeenappliedsuccessfullytoassessmentsofnon‐nativefishinvasions,suchasperch(Perca fluviatilis,Percidae)andchan‐nel catfish (Ictalurus punctatus, Ictaluridae) in Portugal (Banha,Ilhéu,&Anastácio,2015;Banha,Veríssimo,Ribeiro,&Anastácio,2017).Increasingly,thesesearchescanbeautomatedthroughuseofcomputercode.Forexample,geo‐referencedimagesandvideoofspecificspecieswithinimageandvideohostingwebsites(e.g.,flickr)canbesearched,withGIS interfacesenablingdistributionmapstobeconstructed(seeFigure3)andthustemporalandspa‐tialdistributionpatternsbetterunderstood(CodingClub,2018).

6.6 | Complementarity of capture and non‐capture methods

Dataacquiredfromcaptureandnon‐capturemethodswithinthesamemonitoringprogrammeneedtobeintegratedeffectively.Forexample,fishmonitoring inWindermere,England, a relatively largeanddeepglaciallake,hasrecentlybeencomplementedbyapplicationofeDNAthatrecordedthepresenceof14of16fishspeciesknowntobepre‐sent,whenconcomitantgillnetsurveysonlycapturedfourfishspecies(Hänflingetal.,2016).Windermerehasalsobeenmonitoredregularlyforover60yearsbyothermethods,includingfishtraps,gillnets,hy‐droacousticsandpiscivorousfishdietcomposition(Langangenetal.,2011;Winfield,Fletcher,&James,2008,2012).Thehighcomplemen‐tarityofthesedatasetshasimprovedunderstandingofenvironmental(e.g.,nutrientenrichment,warming)andotherchanges(e.g., invasive

fishes), and illustrated their potential for monitoring other systems(e.g.,Vindenesetal.,2014;Winfield,Fletcher,&James,2010).

7  | MA JOR CHALLENGES IN FISH MONITORING

7.1 | Detectability

Many evaluations of biodiversity, including those of freshwaterfishes (Magurran, 2004; Southwood&Henderson, 2000), assumethatindividualshavebeensampledrandomlyfromtheassemblage(Buckland,Studeny,Magurran,&Newson,2011;Pielou,1975).Thisisrarelyachievableinnature(Pielou,1975).Inmanycases,theproblemarisesbecauseitisdifficult(orimpossible)toknowifaspeciesthatisabsentfromasiteorsampleistrulyabsentorismissingthroughthe ineffectiveness of the samplingmethod. Thus, it is importanttothoroughlyconsiderobservationerrorandcaptureprobabilitiesandtoaddressissuesofdetectabilityanddetectionbiasalsoinfishmonitoring.Potentialsolutionstoissuesofdetectabilityhavebeenextensivelydiscussedelsewhereand includemodellingoccupancy(Bayley & Peterson, 2001; Iknayan, Tingley, Furnas, & Beissinger,2014;MacKenzieetal.,2002,2006;Royle&Link,2006;Wenger&Freeman,2008),estimatingtheprobabilityofdetectionofspecies(and/orindividuals)throughmark–recapture(Borchers,Buckland,&Zucchini,2002;Borchers,Stevenson,Kidney,Thomas,&Marques,2015;Bucklandetal.,2011)ordistancesampling (Bucklandetal.,2001, 2004; 2011), and/or demonstrating that the data are suffi‐cientlyrobusttoaddressthequestionposedwithoutfurthercorrec‐tion(Bucklandetal.,2011;Magurranetal.,2018).

7.2 | Taxonomy

Taxonomic issues can often emerge in biological monitoring pro‐grammes,withthemostobviousonebeingtaxonomicuncertaintyandtheriskofspeciesmisidentificationinthefieldorthelaboratory.Forexample,Daan(2001)reportedextensivespeciesmisidentifica‐tionsinamarinefishdatabaseandtherearemanyothercasesinthefreshwaterfishliterature(e.g.,Hänfling,Bolton,Harley,&Carvalho,

F I G U R E 3  Thedistributionof(a)Northernpike(Esox lucius,Esocidae)and(b)Zander(Sander lucioperca,Percidae)intheUK,between1986and2016,basedondatafromGBIF(www.gbif.org).TheRcode(RCoreTeam,2017)usedtoconstructthefigurewasadoptedfromtheCodingClub(https://ourcodingclub.github.io/2017/03/20/seecc.html)[Colourfigure can be viewed at wileyonlinelibrary.com]

(a) (b)

     |  739RADINGER Et Al.

2005; Serrao, Steinke, & Hanner, 2014; Vidal, García‐Berthou,Tedesco, & García‐Marín, 2010). Nevertheless, a well‐appreciatedadvantageoffishisthattheirtaxonomyisbetterknownandeasierthaninmostotherfreshwatergroups,suchasinvertebratesoralgae,andthus,fishcanoftenbeidentifiedinthefieldwithoutsacrificingindividuals.However,thisislesslikelytobethecaseinspecies‐richregionssuchasthetropics,wherethetaxonomyislesswell‐known,comparedtoregionswithwell‐characterizedfishfaunas.

The extent of species misidentification in more taxonomicallychallenginggroups, such as stream invertebrates, receives greaterattention than in freshwater fish. For example, Stribling, Pavlik,Holdsworth,andLeppo (2008)compared taxonomic identificationof stream macro‐invertebrates across eight U.S. laboratories andfoundmeans of 21% taxonomic disagreement. These kinds of er‐rorsmightalsooccurinfishmonitoring,especiallyinsampleswithhighspecies richnessor in samples fromregionswhere taxonomyispoorlydescribed.Thesestudiesreinforcethe importanceofad‐equatetrainingandexperience,documentationofstandardproce‐duresandroutinequalitycontrol(Stribling,Moulton,&Lester,2003;Striblingetal.,2008).Speciesmisidentificationisevenmoreimport‐antwhen fishers are interviewed to obtain local knowledge data.Here,thoroughvalidationproceduresareessential(Poizat&Baran,1997;Valbo‐Jørgensen&Poulsen,2000).

A similar problem iswhen taxonomy changes, and it is recog‐nizedthatasinglespeciesinfactcomprisesseveralcrypticspecies.Thisproblemisincreasinglyfrequentgiventheincreasingpowerofmolecular tools (e.g., April,Mayden,Hanner, & Bernatchez, 2011;Laraetal.,2010;Young,McKelvey,Pilgrim,&Schwartz,2013).Forexample,Youngetal.(2013)foundthatthemajorityofspecies‐leveltaxonomicunitsofthegenusCottus(Cottidae)asevaluatedbyDNAbarcodingdidnotassigntopreviouslyrecognizedspeciesinthisre‐gion.Newtaxonomicalignmentshindercomparisonwitholdsam‐plesifnospecimenswerepreserved.Inaddition,thesamespeciesnamesmayhavehaddifferentsynonymsinthepast,meaningthatdatabasesneed tobe carefully revised for inconsistencies ander‐rors.Erroneoussequencesandmisidentificationsarealsofrequentin GenBank and similar sequence databases (Harris, 2003). It hasbeenestimatedthatupto56%ofGermanfreshwaterfishspeciesmay be incorrectly identified to species level in some databases(Knebelsberger, Dunz, Neumann, & Geiger, 2015). Consequently,errors ingeneticsdatabasesmighthavemajoradverse impactsoneDNAasarobusttechnique.It islikelythatthefrequencyofsuchtaxonomicproblemsindataismoreprevalentinmonitoringoffresh‐waterfishthaninresearch(Striblingetal.,2003).Itisthusimportanttofullyreferencethetaxonomicresourcesusedinstudies,notjustasaqualitycheckonmethodology,butalsotorecognizetheimpor‐tanceoftaxonomyandtheworkoftaxonomists(Santos&Branco,2012;Vink,Paquin,&Cruickshank,2012;Wägeleetal.,2011).

7.3 | Economic costs

Foramonitoringprogrammetobeeffective,successfulandsustain‐able over the longer‐term, it must not only be ecologically relevant

andstatisticallycredible,butalsocostefficient,thatistheperceivedbenefitsofecologicalmonitoring(e.g.,informationontrendsorstatuschanges)mustjustifyitscost(Caughlan&Oakley,2001;Charles,Garcia,&Rice,2016;Hinds,1984).Asfinanciallimitationsalwaysapply,sus‐tainedmonitoringrequiresaproperselectionofrelevantvariablesthatneedtobemeasured(Braun&Reynolds,2012).Oftenthetruecostsofmonitoringarenotrecognizedandlikelyunderestimated(Caughlan&Oakley,2001),anditsbenefitsdependonthevaluethatsocietygivestothelong‐termsustainabilityoffreshwaterecosystems.Hence,costsofmonitoringneedtobecontrastedwiththecostsofnotmonitoring.Theseincludeincreaseduncertaintyinevaluatingoutcomesandfutureprojections,andthepossibilitythatmanagersmaynotdetect impor‐tantshiftsuntilitistoolatetoeffectivelyaddressthem.

CaughlanandOakley(2001)providedabreakdownofmonitoringcosts,comprisingofbudgetaryexpensesrelatedto,forexample,datacollection, datamanagement, quality assessment, data analysis, re‐portingandscientificoversight,opportunitycosts(i.e.,otherbenefitsforgonebyallocatingresourcestomonitoring),andexternalcosts(i.e.,costsnotdirectlycoveredbythemonitoringprogrammebudget).Thecostsfordatacollection—whicharefrequentlythelargest—mayvarydependingonthemethodsapplied.Whileestablishedmethodsinfishmonitoring,suchasfield‐basedcapturemethods(e.g.,electrofishing,netting,trapping),arecommonlylabourintensiveinthefieldandthuscostly,thefinancialcostsofemergingmethods,suchasuseofeDNA,theautomatizedcollectionofdata(e.g.,hydroacousticassessments),andtheuseofcommunityscienceanddatamining,areoftenrelatedtopost‐processing,managingandanalysingbigdata(Section6.4).Adetailedreviewofthecostsassociatedwithecologicalmonitoringcanbefoundelsewhere(e.g.,Caughlan&Oakley,2001).

7.4 | Fish welfare and ethics in monitoring

Theimportanceofethicalissuesrelatingtobiologicalfieldworkandtheneedtominimizeharmtospeciesandecosystemshas repeat‐edly been emphasized (e.g., Bennett et al., 2016; Costello et al.,2016; Farnsworth & Rosovsky, 1993); a detailed consideration ofthesematters is beyond the scope of this review.Wenote, how‐ever, that fish welfare issues have received much attention (e.g.,Sloman, Bouyoucos, Brooks, & Sneddon, 2019), often centredaround the question ofwhether fish are sentient and can experi‐encepainandsuffering (e.g.,Arlinghaus,Cooke,Schwab,&Cowx,2007;Braithwaite,2010;Huntingfordetal.,2006,2007;Roseetal.,2014)—achallengingquestionthathasanumberofimplicationsinascientific,ethicalandlegalcontext(Browmanetal.,2019).Browmanet al. (2019) argue for a pragmatic approach using objective indi‐cators of stress, health status and behaviour to inform about fishwell‐being.

Irrespectiveofthescientificdebateonfishwelfare, institutionalrequirements and legal regulations need to be considered duringfreshwater fish monitoring. Fish sampling usually requires specificpermits from responsible authorities, particularly when workingwithprotectedspeciesorinprotectedareas.Dependingontheaimandsamplingmethod,fishmonitoringmightinvolvethecaptureand

740  |     RADINGER Et Al.

treatmentoffishormightevenrequiremethodsofdestructivesam‐pling, that is thekillingof fish (e.g.,Blessing,Marshall,&Balcombe,2010),suchaswhenindividualsrequiretaxonomicidentificationinthelaboratory,includingwherevoucherspecimensarerequired(Bortolus,2008;Rochaetal.,2014;Section7.2).However,alternativemethodsof identification should be used to avoid collection of rare species(Costello et al., 2016;Minteer,Collins, Love,&Puschendorf, 2014).Protocols for fieldwork (e.g.,Barbour,Gerritsen,Snyder,&Stribling,1999;Brenkman&Connolly,2008;CCME,2011;Cowxetal.,2009;Cowx& Fraser, 2003; Joy et al., 2013) typically provide guidelinesonappropriateandleastinvasivetechniques(e.g.,non‐capturetech‐niquessuchashydroacousticsandeDNAwhereapplicable,Section6.4)andaredesignedtominimizestressordamagecausedbycatching,handling andholding.Developmental stage and speciesdifferencesarealsotakenintoaccount.Thesamplingmethodanddesignshouldconsidertrade‐offsofthepotentialharmtofishversusthequalityoftheobtaineddatainrelationtosamplingefficiency.Inparticular,whencapturetechniquesareapplied,potentialcumulativeeffectsshouldbepaidspecificattentionasfishmonitoringinvolvesrepeatedsamplingofspeciesthatcanbelong‐lived(>20years)andisoftentargetedforprotectedorendangeredspecies(Benejametal.,2012).Forexample,an efficient and common capture technique such as electrofishingmightcausesub‐lethal injuriesthatareoftennotexternallyobviousandpossiblyfatal(Snyder,2003).Moreover,ethicalissuesrelatedtofishmonitoringextendbeyondfishwelfareandmustalsoconsiderim‐pactsonnon‐targetspeciesandecosystemsorthepotentialtransmis‐sionofpestsand/orinvasivespecies(Costelloetal.,2016).

8  | MANAGEMENT OF MONITORING DATA

Forthesustainablesuccessofamonitoringprogrammeandtopo‐tentiallyinferfuturechanges,policiesandproceduresthatguaran‐teethequalityofdatacapture,documentationandpreservationforlong‐termuseisrequired(Michener,2015;Michener&Jones,2012;Rüegg et al., 2014; Sutter, Wainscott, Boetsch, Palmer, & Rugg,2015).Forexample,Vinesetal.(2014)foundthattheavailabilityofresearchdatadeclineswitharticleage,withtheprobabilityoffind‐ingthedatasetdecreasingby17%peryear.

Although the importance of integrating datamanagement intolong‐termecological(monitoring)projectshasbeenemphasizedre‐peatedlyinpreviouspapers(Costello&Wieczorek,2014;Sutteretal.,2015),thisisoftenaneglectedareainfreshwaterfishstudies(butseeMoe,Schmidt‐Kloiber,Dudley,&Hering,2013;Petersonetal.,2013forsomeexamples).Thoroughlyconsideringdatamanagementtopreservedataforlong‐termuseandaccessibility(evenbeyondthelifetimeoftheworkthatgeneratedthem)willrequiremoretimeandresourcestofishmonitoringprogrammesandshouldbeconsideredattheearlieststagesandaccountedforinbudgetaryplans.

Datamanagementisnotlimitedto“what”wascollected(i.e.,fishsamplingdata);manyotherdataoftenassociatedwithsampling,suchasgeospatial information,multimediacontent,voucherspecimens,associated environmental variables and other biological data, also

needtobeconsidered(Costello&Wieczorek,2014).Furthermore,toensuretheutilityofadataset,itmustbeaccompaniedbymeta‐data,that is,adetaileddescriptionofwhocreatedthedata,whenandwherethedatawerecollectedandstored,howandwhythedataweregenerated,processedandanalysed(Michener,2006).

Datamanagementisakeyelementinfreshwaterfishmonitoringprogrammes.Adetaileddiscussionofchallengesandopportunitiesof datamanagement, aswell as practicesof how it canor shouldbeimplementedinfishmonitoringisprovidedelsewhere(Costello,Michener,Gahegan,Zhang,&Bourne,2013;Costello&Wieczorek,2014; Michener & Brunt, 2000; Reichman, Jones, & Schildhauer,2011;Sutteretal.,2015).

9  | CONCLUSIONS

Given the rapid environmental degradation of the Earth's fresh‐water ecosystems and associated unprecedented rates of biodi‐versity change, the importanceof robust, replicable andeffectiveprogrammes to monitor freshwater fish has never been higher.Future challenges related tohabitatdegradation, climateand landuse change, and biological invasions necessitate monitoring pro‐grammes that systematically collect quality data allowing the po‐tentialdetectionof systemic shiftsofpopulationsor communitiesandtherebyimproveourunderstandingofecosystemresponsestoenvironmentalchange.Thereisapressingneedforeffectivemoni‐toringtocomprehensiblyquantifybiodiversitychangeandtoinformevidence‐basedenvironmentaldecision‐making.

Ataminimum,whenestablishingamonitoringprogramme,cleararticulationofthemonitoringaim(s)isessentialandshouldaddress:(a)what should bemonitored and how; (b) how to allocate effortwithintimeandacrosssites;(c)establishcriteriafordatareliability;and(d)identifypracticalconstraints.

Monitoringmustalsotakeintoaccountissuesrelatedtothede‐tectability of species, taxonomy and animal welfare. Additionally,monitoringprogrammesmustintegratedatamanagementpracticesthatensurethequalityofdatacapture,documentationandpreser‐vationofinformationforlong‐termuseandre‐use.

Insummary,carefulreflectiononaims(s)andtheextenttowhichthedatacollectedwillmeettheseaimswillgreatlyimprovethequal‐ityandusefulnessofmonitoringdata.Consistentlyhighmonitoringstandardswillimprovedatacomparabilitywithinandamongstcoun‐triesandsystems.Finally,effectivemonitoringoffreshwaterfishwilladvance our overall understanding of freshwater ecosystems andcontributetothepreservationandmanagementoffreshwaterfishdiversitywhilehelpingmitigateanthropogenicimpacts.

ACKNOWLEDG EMENTS

ThispaperisbasedonaworkshopfundedbytheSpanishMinistryof Science, Innovation and Universities (project CGL2015‐69311‐REDT).Additionalfinancialsupportwasprovidedbythesamemin‐istry(projects:ODYSSEUS,BiodivERsA3‐2015‐26,PCIN‐2016‐168;

     |  741RADINGER Et Al.

andCGL2016‐80820‐R)andtheGovernmentofCatalonia(ref.2014SGR484and2017SGR548).

ORCID

Johannes Radinger https://orcid.org/0000‐0002‐2637‐9464

Stephanie M. Carlson https://orcid.org/0000‐0003‐3055‐6483

Anne E. Magurran https://orcid.org/0000‐0002‐0036‐2795

Juan Diego Alcaraz‐Hernández https://orcid.org/0000‐0002‐6885‐6695

Ana Almodóvar https://orcid.org/0000‐0003‐1465‐3857

Lluís Benejam https://orcid.org/0000‐0002‐2741‐4858

Carlos Fernández‐Delgado https://orcid.org/0000‐0002‐1359‐435X

Graciela G. Nicola https://orcid.org/0000‐0002‐6898‐307X

Emili García‐Berthou https://orcid.org/0000‐0001‐8412‐741X

R E FE R E N C E S

Alexander,M. (2008).Management planning for nature conservation ‐ a theoretical basis & practical guide.Dordrecht,Netherlands:Springer.

Allan,J.D.,Abell,R.,Hogan,Z.,Revenga,C.,Taylor,B.W.,Welcomme,R. L., & Winemiller, K. O. (2005). Overfishing of inland waters.BioScience, 55,1041–1051.https://doi.org/10.1641/0006‐3568(2005)055[1041:OOIW]2.0.CO;2

AmatTrigo,F.,GutmannRoberts,C.,&Britton,J.R.(2017).Spatialvari‐ability in the growthof invasiveEuropeanbarbelBarbus barbus in theRiverSevernbasin, revealedusinganglersascitizenscientists.Knowledge & Management of Aquatic Ecosystems, 418(17),1–6.https://doi.org/10.1051/kmae/2017009

April,J.,Mayden,R.L.,Hanner,R.H.,&Bernatchez,L.(2011).Geneticcalibrationof species diversity amongNorthAmerica’s freshwaterfishes.Proceedings of the National Academy of Sciences, 108,10602–10607.https://doi.org/10.1073/pnas.1016437108

Arlinghaus,R.,Cooke,S.J.,Schwab,A.,&Cowx,I.G.(2007).Fishwel‐fare:Achallengetothefeelings‐basedapproach,with implicationsfor recreational fishing. Fish and Fisheries, 8, 57–71. https://doi.org/10.1111/j.1467‐2979.2007.00233.x

Banha,F., Ilhéu,M.,&Anastácio,P.M. (2015).Anglingweb forumsasanadditionaltoolfordetectionofnewfishintroductions:Thefirstrecord of Perca fluviatilis in continental Portugal. Knowledge and Management of Aquatic Ecosystems, 416,03.https://doi.org/10.1051/kmae/2014039

Banha,F.,Veríssimo,A.,Ribeiro,F.,&Anastácio,P.M.(2017).Forensicreconstruction of Ictalurus punctatus invasion routes using on‐linefishermenrecords.Knowledge & Management of Aquatic Ecosystems, 418(56),1–8.https://doi.org/10.1051/kmae/2017045

Barbour,M.T.,Gerritsen,J.,Snyder,B.D.,&Stribling,J.B.(1999).Rapid bioas‐sessment protocols for use in streams and wadeable rivers: Periphyton, ben‐thic macroinvertebrates, and fish.Washington,DC:EPA841‐B‐99‐002,U.S.EnvironmentalProtectionAgency;OfficeofWater.

Barnes,M.A.,Turner,C.R.,Jerde,C.L.,Renshaw,M.A.,Chadderton,W.L.,&Lodge,D.M.(2014).EnvironmentalconditionsinfluenceeDNApersistence inaquaticsystems.Environmental Science & Technology, 48,1819–1827.https://doi.org/10.1021/es404734p

Baselga, A. (2010). Partitioning the turnover and nestedness compo‐nentsofbetadiversity.Global Ecology and Biogeography, 19, 134–143. https://doi.org/10.1111/j.1466‐8238.2009.00490.x

Bayley,P.B.,&Peterson,J.T.(2001).Anapproachtoestimateprobabilityofpresenceandrichnessoffishspecies.Transactions of the American Fisheries Society, 130, 620–633. https://doi.org/10.1577/1548‐8659(2001)130<0620:AATEPO>2.0.CO;2

Beamish, R. J., & McFarlane, G. A. (1983). The forgotten require‐ment for age validation in fisheries biology. Transactions of the American Fisheries Society, 112, 735–743. https://doi.org/10.1577/1548‐8659(1983)112<735:TFRFAV>2.0.CO;2

Benejam, L., Alcaraz, C., Benito, J., Caiola, N., Casals, F., Maceda‐Veiga,A.,…García‐Berthou,E.(2012).Fishcatchabilityandcom‐parison of four electrofishing crews in Mediterranean streams.Fisheries Research, 123–124, 9–15. https://doi.org/10.1016/j.fishres.2011.11.022

Bennett, R. H., Ellender, B. R., Mäkinen, T., Miya, T., Pattrick, P.,Wasserman,R.J.,…Weyl,O.L.F.(2016).Ethicalconsiderationsforfieldresearchonfishes.Koedoe, 58,1–15.https://doi.org/10.4102/koedoe.v58i1.1353

Bik,H.M.,&Goldstein,M.C.(2013).Anintroductiontosocialmediaforscientists.PLoS Biology, 11,e1001535.https://doi.org/10.1371/journal.pbio.1001535

Birk,S.,Bonne,W.,Borja,A.,Brucet,S.,Courrat,A.,Poikane,S.,…Hering,D.(2012).ThreehundredwaystoassessEurope’ssurfacewaters:Analmostcompleteoverviewofbiologicalmethods to implement theWaterFrameworkDirective.Ecological Indicators, 18,31–41.https://doi.org/10.1016/j.ecolind.2011.10.009

Blessing,J.J.,Marshall,J.C.,&Balcombe,S.R.(2010).Humanekillingoffishesforscientificresearch:Acomparisonoftwomethods.Journal of Fish Biology, 76,2571–2577.https://doi.org/10.1111/j.1095‐8649.2010.02633.x

Bonar,S.A.,Fehmi,J.S.,&Mercado‐Silva,N.(2011).Anonverviewofsam‐plingissuesinspeciesdiversityandabundancesurveys.InA.Magurran,&B.McGill(Eds.),Biological diversity: Frontiers in measurement and as‐sessment(pp.11–24).NewYork,NY:OxfordUniversityPress.

Bonar,S.A.,Hubert,W.A.,&Willis,D.W.(2009).Standard methods for sampling North American freshwater fishes.Bethesda,MD:AmericanFisheriesSociety.

Bonar, S.A.,Mercado‐Silva,N.,Hubert,W.A., Beard, T.D.,Dave,G.,Kubečka, J., … Winfield, I. J. (2017). Standard methods for sam‐pling freshwater fishes: Opportunities for international collab‐oration. Fisheries, 42, 150–156. https://doi.org/10.1080/03632415.2017.1276352

Borchers,D.,Buckland,S.,&Zucchini,W.(2002).Estimating animal abun‐dance: Closed populations.London,UK:Springer.

Borchers, D. L., Stevenson, B. C., Kidney, D., Thomas, L., &Marques,T.A. (2015).Aunifyingmodel for capture–recapture anddistancesampling surveys of wildlife populations. Journal of the American Statistical Association, 110,195–204.https://doi.org/10.1080/01621459.2014.893884

Bortolus,A. (2008). Error cascades in thebiological sciences:Theun‐wantedconsequencesofusingbadtaxonomyinecology.Ambio, 37, 114–118. https://doi.org/10.1579/0044‐7447(2008)37[114:ECITBS]2.0.CO;2

Boswell,K.M.,Wilson,M.P.,&Wilson,C.A.(2007).HydroacousticsasatoolforassessingfishbiomassandsizedistributionassociatedwithdiscreteshallowwaterestuarinehabitatsinLouisiana.Estuaries and Coasts, 30,607–617.https://doi.org/10.1007/BF02841958

Braithwaite,V.(2010).Do fish feel pain?Oxford,UK:OxfordUniversityPress.

Braun,D.C.,&Reynolds,J.D.(2012).Cost‐effectivevariableselectioninhabitatsurveys.Methods in Ecology and Evolution, 3,388–396.https://doi.org/10.1111/j.2041‐210X.2011.00154.x

Brenkman,S.J.,NationalParkService,&Connolly,P.J.(2008).Protocol for monitoring fish assemblages in Pacific Northwest National Parks. Virginia,USA:Reston.

Britton, J.R.,Harper,D.M.,&Oyugi,D.O. (2010). Is the fast growthofanequatorialMicropterussalmoidespopulationexplainedbyhigh

742  |     RADINGER Et Al.

watertemperature?Ecology of Freshwater Fish, 19,228–238.https://doi.org/10.1111/j.1600‐0633.2010.00407.x

Browman,H.I.,Cooke,S.J.,Cowx,I.G.,Derbyshire,S.W.G.,Kasumyan,A.,Key,B.,…Arlinghaus,R.(2019).Welfareofaquaticanimals:Wherethings are, where they are going, andwhat it means for research,aquaculture,recreationalangling,andcommercialfishing.ICES Journal of Marine Science, 76,82–92.https://doi.org/10.1093/icesjms/fsy067

Buckland,S.T.,Anderson,D.R.,Burnham,K.P.,Laake,J.L.,Borchers,D.L.,&Thomas,L.(2001).Introduction to distance sampling: Estimating abun‐dance of biological populations.Oxford,UK:OxfordUniversityPress.

Buckland,S.T.,Anderson,D.R.,Burnham,K.P.,Laake,J.L.,Borchers,D.L.,&Thomas,L.(2004).Advanced distance sampling: Estimating abun‐dance of biological populations.Oxford,UK:OxfordUniversityPress.

Buckland,S.T.,Baillie,S.R.,Dick,J.M.P.,Elston,D.A.,Magurran,A.E.,Scott,E.M.,…Watt,A.(2012).Howshouldregionalbiodiversitybemonitored?Environmental and Ecological Statistics, 19,601–626.https://doi.org/10.1007/s10651‐012‐0202‐7

Buckland,S.,Studeny,A.,Magurran,A.,&Newson,S.(2011).Biodiversitymonitoring: The relevance of detectability. In A. Magurran, & B.McGill(Eds.),Biological diversity: Fontiers in measurement and assess‐ment(pp.25–36).Oxford,UK:OxfordUniversityPress.

Busst,G.M.,&Britton,J.R. (2014).Precisionof theage‐length incre‐ments of three cyprinids: Effects of fish number and sub‐sam‐pling strategy. Journal of Fish Biology, 84, 1926–1939. https://doi.org/10.1111/jfb.12409

Capra, H., Plichard, L., Bergé, J., Pella, H., Ovidio, M., McNeil, E., &Lamouroux,N. (2017).Fishhabitat selection ina largehydropeak‐ingriver:Strong individualandtemporalvariations revealedbyte‐lemetry. Science of the Total Environment, 578,109–120.https://doi.org/10.1016/j.scitotenv.2016.10.155

Carpenter,S.R.,Frost,T.M.,Heisey,D.,&Kratz,T.K.(1989).Randomizedinterventionanalysisandtheinterpretationofwhole‐ecoysystemex‐periments.Ecology, 70,1142–1152.https://doi.org/10.2307/1941382

Caughlan,L.,&Oakley,K.L. (2001).Costconsiderationsfor long‐termecological monitoring. Ecological Indicators, 1,123–134.https://doi.org/10.1016/S1470‐160X(01)00015‐2

Cayuela, L., & Gotelli, N. (2014). rareNMtests: Ecological and biogeo‐graphicalnullmodeltestsforcomparingrarefactioncurves.https://cran.r‐project.org/package=rareNMtest.

Cayuela,L.,Gotelli,N.J.,&Colwell,R.K.(2015).Ecologicalandbiogeo‐graphicnullhypothesesforcomparingrarefactioncurves.Ecological Monographs, 85,437–455.https://doi.org/10.1890/14‐1261.1

CCME. (2011). Protocols manual for water quality sampling in Canada. Winnipeg,Canada:CanadianCouncilofMinistersoftheEnvironment.

CEN. ( 2003).EN 14011 water quality ‐ sampling of fish with electricity. Brussels,Belgium:EuropeanCommitteeforStandardization(CEN).

CEN. (2006). EN 14757 water quality ‐ sampling of fish with multi‐mesh gillnets.Brussels,Belgium:EuropeanCommitteeforStandardization(CEN).

Chao, A., Gotelli, N. J., Hsieh, T. C., Sander, E. L.,Ma, K. H., Colwell,R. K., & Ellison, A. M. (2014). Rarefaction and extrapolation withHill numbers:A framework for sampling andestimation in speciesdiversity studies. Ecological Monographs, 84, 45–67. https://doi.org/10.1890/13‐0133.1

Charles,A.,Garcia,S.M.,&Rice,J.(2016).Balancedharvestinginfish‐eries: Economic considerations. ICES Journal of Marine Science, 73, 1679–1689.https://doi.org/10.1093/icesjms/fsv161

Chisnall, B. L., & Kalish, J. M. (1993). Age validation and movementof freshwater eels (Anguilla dieffenbachii and A. australis) in aNew Zealand pastoral stream.New Zealand Journal of Marine and Freshwater Research, 27, 333–338. https://doi.org/10.1080/00288330.1993.9516573

CodingClub.(2018).Manipulationandvisualisationofspatialandpop‐ulation data. https://ourcodingclub.github.io/2018/01/06/occurrence.html.

Coggins,L.G.,Bacheler,N.M.,&Gwinn,D.C.(2014).Occupancymod‐elsformonitoringmarinefish:ABayesianhierarchicalapproachtomodelimperfectdetectionwithanovelgearcombination.PLoS ONE, 9,e108302.https://doi.org/10.1371/journal.pone.0108302

Conroy,M.J.,&Carroll, J.P. (2009).Quantitative conservation of verte‐brates.Chichester,UK:Wiley‐Blackwell.

Cooke,S.J.,Arthington,A.A.,Bonar,S.A.,Bower,S.D.,Bunnell,D.B.,Entsua‐Mensah,R.E.M.,&Cowx,I.G.(2016).Assessmentofinlandfisheries:Avisionforthefuture.InW.W.Taylor,D.M.Bartley,C.I.Goddard,N.J.Leonard,&R.Welcome(Eds.),Freshwater, fish, and the future: Proceedings of the global cross‐sectoral conference (pp. 45–62).Rome,Michigan,Bethesda:FoodandAgricultureOrganizationoftheUnitedNations,MichiganStateUniversity,AmericanFisheriesSociety.

Cooke,S.,Paukert,C.,&Hogan,Z.(2012).Endangeredriverfish:Factorshinderingconservationandrestoration.Endangered Species Research, 17,179–191.https://doi.org/10.3354/esr00426

Cooke,S.J.,Woodley,C.M.,BradEppard,M.,Brown,R.S.,&Nielsen,J. L. (2011). Advancing the surgical implantation of electronictags in fish: A gap analysis and research agenda based on a re‐viewoftrendsinintracoelomictaggingeffectsstudies.Reviews in Fish Biology and Fisheries, 21, 127–151. https://doi.org/10.1007/s11160‐010‐9193‐3

Cooper, M. J., & Wheatley, G. A. (1981). An examination of thefish population in the River Trent, Nottinghamshire using an‐gler catches. Journal of Fish Biology, 19, 539–556. https://doi.org/10.1111/j.1095‐8649.1981.tb03821.x

Copp,G.H.(2010).PatternsofdielactivityandspeciesrichnessinyoungandsmallfishesofEuropeanstreams:Areviewof20yearsofpointabundance sampling by electrofishing.Fish and Fisheries, 11, 439–460.https://doi.org/10.1111/j.1467‐2979.2010.00370.x

Costello,M. J., Beard, K. H., Corlett, R. T., Cumming, G. S., Devictor,V., Loyola,R.,…Primack,R.B. (2016).Fieldworkethics inbiolog‐ical research. Biological Conservation, 203, 268–271. https://doi.org/10.1016/j.biocon.2016.10.008

Costello,M.J.,Michener,W.K.,Gahegan,M.,Zhang,Z.‐Q.,&Bourne,P.E. (2013).Biodiversitydatashouldbepublished,cited,andpeerreviewed. Trends in Ecology & Evolution, 28, 454–461. https://doi.org/10.1016/j.tree.2013.05.002

Costello,M.J.,&Wieczorek,J.(2014).Bestpracticeforbiodiversitydatamanagement and publication. Biological Conservation, 173, 68–73.https://doi.org/10.1016/j.biocon.2013.10.018

Counihan,T.D.,Waite,I.R.,Casper,A.F.,Ward,D.L.,Sauer,J.S.,Irwin,E.R.,…Bayer,J.M.(2018).Candatafromdisparatelong‐termfishmonitoringprogramsbeusedto increaseourunderstandingof re‐gionalandcontinentaltrendsinlargeriverassemblages?PLoS ONE, 13,e0191472.https://doi.org/10.1371/journal.pone.0191472

Cowx, I. G., & Broughton,N.M. (1986). Changes in the species com‐position of anglers’ catches in the River Trent (England) between1969 and 1984. Journal of Fish Biology, 28, 625–636. https://doi.org/10.1111/j.1095‐8649.1986.tb05197.x

Cowx,I.G.,&Fraser,D.(2003).Monitoring the Atlantic Salmon Salmosalar. Conserving Natura 2000 Rivers. Monitoring Series No. 7.Peterborough,UK:EnglishNature.

Cowx,I.G.,Harvey,J.P.,Noble,R.A.,&Nunn,A.D.(2009).Establishingsurveyandmonitoringprotocolsfortheassessmentofconservationstatusof fishpopulations in riverSpecialAreasofConservation intheUK.Aquatic Conservation: Marine and Freshwater Ecosystems, 19, 96–103.https://doi.org/10.1002/aqc.968

Crawford,I.M.(1997).Marketing research and information systems. Rome, Italy:FoodandAgricultureOrganizationoftheUnitedNations.

Daan, N. (2001). The IBTS database: A plea for quality control.International Council for the Exploration of the Sea, 3, 1–5.

Darwin,C.(1859).On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life.London,UK:JohnMurray.

     |  743RADINGER Et Al.

Davison,P.I.,Créach,V.,Liang,W.‐J.,Andreou,D.,Britton,J.R.,&Copp,G.H.(2016).Laboratoryandfieldvalidationofasimplemethodfordetecting four species of non‐native freshwater fish using eDNA.Journal of Fish Biology, 89, 1782–1793. https://doi.org/10.1111/jfb.13086

deKerckhove,D.T.,Minns,C.K.,&Chu,C.(2015).Estimatingfishex‐ploitationandaquatichabitatlossacrossdiffuseinlandrecreationalfisheries. PLoS ONE, 10, e0121895. https://doi.org/10.1371/journal.pone.0121895

DiMinin,E.,Tenkanen,H.,&Toivonen,T.(2015).Prospectsandchal‐lenges for social media data in conservation science. Frontiers in Environmental Science, 3(63), 1–6. https://doi.org/10.3389/fenvs.2015.00063

Dixon, W., & Chiswell, B. (1996). Review of aquatic monitoringprogram design. Water Research, 30, 1935–1948. https://doi.org/10.1016/0043‐1354(96)00087‐5

Dornelas,M.,Gotelli,N.J.,McGill,B.,Shimadzu,H.,Moyes,F.,Sievers,C.,&Magurran,A.E.(2014).Assemblagetimeseriesrevealbiodiver‐sitychangebutnotsystematicloss.Science, 344,296–299.https://doi.org/10.1126/science.1248484

Downes,B.J.,Barmuta,L.A.,Fairweather,P.G.,Faith,D.P.,Keough,J.,&Lake,P.S.(2002).Monitoring ecological impacts: Concepts and practice in flowing waters.NewYork,NY:CambridgeUniversityPress.

Dudgeon, D., Arthington, A. H., Gessner, M. O., Kawabata, Z.‐I.,Knowler,D. J., Lévêque, C.,… Sullivan, C. A. (2006). Freshwaterbiodiversity: Importance, threats, status and conservation chal‐lenges. Biological Reviews, 81, 163–182. https://doi.org/10.1017/S1464793105006950

Dukerschein, J.T.,Bartels,A.D., Ickes,B.S.,&Pearson,M.S. (2011).Are two systemic fish assemblage sampling programmes on theupperMississippiRivertellingusthesamething?River Research and Applications, 29,79–89.https://doi.org/10.1002/rra.1575

Farnsworth, E. J., & Rosovsky, J. (1993). The ethics of ecological fieldexperimentation.Conservation Biology, 7,463–472.https://doi.org/10.1046/j.1523‐1739.1993.07030463.x

Fausch, K.D., Karr, J. R., & Yant, P. R. (1984). Regional application ofan index of biotic integrity based on stream fish communities.Transactions of the American Fisheries Society, 113,39–55.https://doi.org/10.1577/1548‐8659(1984)113<39:RAOAIO>2.0.CO;2

Fausch,K.D.D.,Torgersen,C.E.E.,Baxter,C.V.V.,&Li,H.W.W.(2002).Landscapestoriverscapes:Bridgingthegapbetweenresearchandconservationofstreamfishes.BioScience, 52,483–498.https://doi.org/10.1641/0006‐3568(2002)052[0483:LTRBTG]2.0.CO;2

Fölster, J., Johnson, R. K., Futter, M. N., & Wilander, A. (2014). TheSwedishmonitoringofsurfacewaters:50yearsofadaptivemonitor‐ing. Ambio, 43,3–18.https://doi.org/10.1007/s13280‐014‐0558‐z

Froese,R.,&Pauly,D. (2018).FishBase.Availableathttp://www.fishbase.org.

Frouzova,J.,Kubecka,J.,Balk,H.,&Frouz,J.(2005).TargetstrengthofsomeEuropeanfishspeciesanditsdependenceonfishbodyparam‐eters. Fisheries Research, 75, 86–96. https://doi.org/10.1016/j.fishres.2005.04.011

Funk,W.C.,McKay, J.K.,Hohenlohe,P.A.,&Allendorf,F.W. (2012).Harnessing genomics for delineating conservation units. Trends in Ecology & Evolution, 27, 489–496. https://doi.org/10.1016/j.tree.2012.05.012

Gallagher,S.P.,Wright,D.W.,Collins,B.W.,&Adams,P.B. (2010).Aregionalapproachformonitoringsalmonidstatusandtrends:Resultsfromapilot study inCoastalMendocinoCounty,California.North American Journal of Fisheries Management, 30, 1075–1085. https://doi.org/10.1577/M09‐203.1

Gotelli, N. J., & Colwell, R. K. (2001). Quantifying biodiversity:Procedures and pitfalls in the measurement and comparisonof species richness. Ecology Letters, 4, 379–391. https://doi.org/10.1046/j.1461‐0248.2001.00230.x

Gotelli, N., & Colwell, R. (2011). Estimating species richness. In A.Magurran, & B. McGill (Eds.), Biological diversity: Frontiers in mea‐surement and assessment(pp.39–54).Oxford,UK:OxfordUniversityPress.

Graham,C.T.,&Harrod,C.(2009).ImplicationsofclimatechangeforthefishesoftheBritishIsles.Journal of Fish Biology, 74,1143–1205.https://doi.org/10.1111/j.1095‐8649.2009.02180.x

Guillard,J.,&Vergès,C.(2007).Therepeatabilityoffishbiomassandsizedistributionestimatesobtainedbyhydroacousticsurveysusingvar‐ioussamplingstrategiesandstatisticalanalyses.International Review of Hydrobiology, 92, 605–617. https://doi.org/10.1002/iroh.200710948

GutmannRoberts,C., Bašić, T.,Amat Trigo, F.,&Britton, J. R. (2017).Trophicconsequencesforriverinecyprinidfishesofanglersubsidiesbasedonmarine‐derivednutrients.Freshwater Biology, 62, 894–905. https://doi.org/10.1111/fwb.12910

Hamel,M. J.,Pegg,M.A.,Goforth,R.R.,Phelps,Q.E.,Steffensen,K.D.,Hammen,J.J.,&Rugg,M.L.(2015).Range‐wideageandgrowthcharacteristics of shovelnose sturgeon frommark–recapture data:Implicationsforconservationandmanagement.Canadian Journal of Fisheries and Aquatic Sciences, 72, 71–82. https://doi.org/10.1139/cjfas‐2014‐0238

Hamidan,N.,&Britton,J.R.(2015).AgeandgrowthratesofthecriticallyendangeredfishGarra ghorensiscaninformtheirconservationman‐agement. Aquatic Conservation: Marine and Freshwater Ecosystems, 25, 61–70.https://doi.org/10.1002/aqc.2449

Hänfling, B., Bolton, P., Harley, M., & Carvalho, G. R. (2005). A mo‐lecular approach to detect hybridisation between crucian carp(Carassius carassius)andnon‐indigenouscarpspecies(Carassiusspp.and Cyprinus carpio). Freshwater Biology, 50, 403–417. https://doi.org/10.1111/j.1365‐2427.2004.01330.x

Hänfling,B.,LawsonHandley,L.,Read,D.S.,Hahn,C.,Li,J.,Nichols,P.,…Winfield, I.J. (2016).EnvironmentalDNAmetabarcodingof lakefish communities reflects long‐term data from established surveymethods.Molecular Ecology, 25,3101–3119.https://doi.org/10.1111/mec.13660

Harby,A.,Olivier,J.‐M.,Merigoux,S.,&Malet,E.(2007).Amesohabitatmethodusedtoassessminimumflowchangesand impactsontheinvertebrateandfishfaunaintheRhôneRiver,France.River Research and Applications, 23,525–543.https://doi.org/10.1002/rra.997

Hargrove,W.W.,&Pickering, J. (1992).Pseudoreplication:A sinequanon for regional ecology. Landscape Ecology, 6,251–258.https://doi.org/10.1007/BF001 29703

Harris, D. J. (2003). Can you bank on GenBank? Trends in Ecology & Evolution, 18, 317–319. https://doi.org/10.1016/S0169‐5347(03) 00150‐2

Haxton,T.(2011).Depthselectivityandspatialdistributionofjuvenilelakesturgeoninalarge,fragmentedriver.Journal of Applied Ichthyology, 27,45–52.https://doi.org/10.1111/j.1439‐0426.2011.01872.x

Hellawell,J.M.(1991).Developmentofarationaleformonitoring.InB.Goldsmith (Ed.),Monitoring for conservation and ecology (pp. 1–14).London,UK:Chapman&Hall.

Hinds,W.T. (1984).Towardsmonitoringof long‐termtrends in terres‐trialecosystems.Environmental Conservation, 11,11–18.https://doi.org/10.1017/S0376892900013448

Hobbs,N.T.,&Hooten,M.B.(2015).Bayesian models: a statistical primer for ecologists.Princeton(US)&Woodstock(UK):PrincetonUniversityPress.

Holmgren, K., Degerman, E., Petersson, E., & Bergquist, B. (2016).LongtermtrendsoffishafterlimingofSwedishstreamsandlakes.Atmospheric Environment, 146, 245–251. https://doi.org/10.1016/j.atmosenv.2016.08.033

Holmlund,C.M.,&Hammer,M. (1999).Ecosystemservicesgeneratedby fishpopulations.Ecological Economics, 29, 253–268. https://doi.org/10.1016/S0921‐8009(99)00015‐4

744  |     RADINGER Et Al.

Hsieh, T. C., Ma, K. H., & Chao, A. (2016). iNEXT: An R package forrarefaction and extrapolation of species diversity (Hill num‐bers).Methods in Ecology and Evolution, 7, 1451–1456. https://doi.org/10.1111/2041‐210X.12613

Huey,J.A.,Schmidt,D.J.,Balcombe,S.R.,Marshall,J.C.,&Hughes,J.M. (2011).Highgene flowandmetapopulationdynamicsdetectedfor three species in a dryland river system.Freshwater Biology, 56, 2378–2390.https://doi.org/10.1111/j.1365‐2427.2011.02666.x

Hughes, S. (1998). Amobile horizontal hydroacoustic fisheries surveyoftheRiverThames,UnitedKingdom.Fisheries Research, 35, 91–97. https://doi.org/10.1016/S0165‐7836(98)00063‐0

Huntingford, F. A., Adams, C., Braithwaite, V. A., Kadri, S., Pottinger,T. G., Sandoe, P., & Turnbull, J. F. (2006). Current issues infish welfare. Journal of Fish Biology, 68, 332–372. https://doi.org/10.1111/j.0022‐1112.2006.001046.x

Huntingford,F.,Adams,C.,Braithwaite,V.A.,Kadri,S.,Pottinger,T.G.,Sandoe,P.,&Turnbull,J.F.(2007).Theimplicationsofafeelings‐basedapproachtofishwelfare:areplytoArlinghausetal.Fish and Fisheries, 8,277–280.https://doi.org/10.1111/j.1467‐2679.2007.00254.x

Hurford, C. (2010). Conservation monitoring in freshwater habitats:An introduction. In C. Hurford, M. Schneider, & I. Cowx (Eds.),Conservation monitoring in freshwater habitats(pp.3–13).Dordrecht,Netherlands:Springer.

Iknayan,K. J., Tingley,M.W., Furnas, B. J.,&Beissinger, S. R. (2014).Detectingdiversity:Emergingmethodstoestimatespeciesdiversity.Trends in Ecology & Evolution, 29,97–106.https://doi.org/10.1016/j.tree.2013.10.012

Isaak,D. J.,Peterson,E.E.,VerHoef, J.M.,Wenger,S. J.,Falke, J.A.,Torgersen,C.E.,…Monestiez,P.(2014).Applicationsofspatialsta‐tistical network models to stream data.Wires Water, 1, 277–294. https://doi.org/10.1002/wat2.1023

Isaak,D.J.,VerHoef,J.M.,Peterson,E.E.,Horan,D.L.,&Nagel,D.E.(2017).Scalablepopulationestimatesusingspatial‐stream‐network(SSN)models,fishdensitysurveys,andnationalgeospatialdatabaseframeworks for streams. Canadian Journal of Fisheries and Aquatic Sciences, 74,147–156.https://doi.org/10.1139/cjfas‐2016‐0247

IUCN FFSG. (2015). Importance of freshwater fishes. Available at:http://www.iucnffsg.org/freshwater‐fishes/importance‐of‐freshwa‐ter‐fishes/.

Jerde, C. L.,Mahon,A. R., Chadderton,W. L.,& Lodge,D.M. (2011).“Sight‐unseen” detection of rare aquatic species using envi‐ronmental DNA. Conservation Letters, 4, 150–157. https://doi.org/10.1111/j.1755‐263X.2010.00158.x

Jones,C.M.,Robson,D.S.,Lakkis,H.D.,&Kressel,J.(1995).Propertiesof catch rates used in analysis of angler surveys. Transactions of the American Fisheries Society, 124, 911–928. https://doi.org/10.1577/1548‐8659(1995)124<0911:POCRUI>2.3.CO;2

Joy,M.,David,B.,&Lake,M.(2013).New Zealand freshwater fish sam‐pling protocols ‐ Wadeable rivers and streams. Palmerston North:Massey University, The Ecology Group – Institute of NaturalResources.

Kershner, J. L. (1997).Monitoring and adaptivemanagement. In J. E.Williams,C.A.Wood,&M.P.Dombeck(Eds.),Watershed restoration: Principles and practices (pp. 116–131). Bethesda, MD: AmericanFisheriesSociety.

Kincaid,T.M.,&Olsen,A.R.(2016).spsurvey: Spatial survey design and analysis.https://cran.r‐project.org/package=spsurvey.

Knebelsberger, T., Dunz, A. R., Neumann, D., & Geiger, M. F. (2015).MoleculardiversityofGermany’sfreshwaterfishesandlampreysas‐sessedbyDNAbarcoding.Molecular Ecology Resources, 15,562–572.https://doi.org/10.1111/1755‐0998.12322

Lacoursière‐Roussel, A., Côté,G., Leclerc, V.,&Bernatchez, L. (2016).Quantifying relative fish abundancewith eDNA: A promising toolforfisheriesmanagement.Journal of Applied Ecology, 53, 1148–1157. https://doi.org/10.1111/1365‐2664.12598

Laffaille, P., Briand, C., Fatin, D., Lafage,D., & Lasne, E. (2005). Pointsampling the abundance of European eel (Anguilla anguilla) infreshwater areas.Archiv Für Hydrobiologie, 162, 91–98. https://doi.org/10.1127/0003‐9136/2005/0162‐0091

Langangen,Ø.,Edeline,E.,Ohlberger, J.,Winfield, I. J.,Fletcher, J.M.,James,J.B.,…Vøllestad,L.A.(2011).Sixdecadesofpikeandperchpopulation dynamics inWindermere.Fisheries Research, 109, 131–139.https://doi.org/10.1016/j.fishres.2011.01.029

Lara, A., Ponce de León, J. L., Rodríguez, R., Casane, D., Côté, G.,Bernatchez, L., & García‐Machado, E. (2010). DNA barcoding ofCubanfreshwaterfishes:Evidenceforcrypticspeciesandtaxonomicconflicts. Molecular Ecology Resources, 10, 421–430. https://doi.org/10.1111/j.1755‐0998.2009.02785.x

Larsen, D. P., Kincaid, T. M., Jacobs, S. E., & Urquhart, N. S. (2001).Designsforevaluatinglocalandregionalscaletrends.BioScience, 51, 1069–1078.https://doi.org/10.1641/0006‐3568(2001)051[1069:D‐FELAR]2.0.CO;2

Larsen,D.P.,Olsen,A.R.,&Stevens,D.L.(2008).Usingamastersam‐pletointegratestreammonitoringprograms.Journal of Agricultural, Biological, and Environmental Statistics, 13, 243–254. https://doi.org/10.1198/108571108X336593

LawsonHandley,L.(2015).Howwillthe‘molecularrevolution’contrib‐utetobiologicalrecording?Biological Journal of the Linnean Society, 115,750–766.https://doi.org/10.1111/bij.12516

Legg,C.J.,&Nagy,L.(2006).Whymostconservationmonitoringis,butneednotbe,awasteoftime.Journal of Environmental Management, 78,194–199.https://doi.org/10.1016/j.jenvman.2005.04.016

Letcher,B.H.,Schueller,P.,Bassar,R.D.,Nislow,K.H.,Coombs,J.A.,Sakrejda,K.,…Dubreuil,T.L. (2015).Robustestimatesofenviron‐mentaleffectsonpopulationvital rates:An integratedcapture‐re‐capturemodelofseasonalbrooktroutgrowth,survivalandmove‐ment in a streamnetwork. Journal of Animal Ecology, 84, 337–352. https://doi.org/10.1111/1365‐2656.12308

Lévêque,C.,Oberdorff,T.,Paugy,D.,Stiassny,M.L.J.,&Tedesco,P.A.(2008).Globaldiversityoffish(Pisces)infreshwater.Hydrobiologia, 595,545–567.https://doi.org/10.1007/s10750‐007‐9034‐0

Lin,H.‐Y.,Brown,C.J.,Dwyer,R.G.,Harding,D.J.,Roberts,D.T.,Fuller,R.A.,…Possingham,H.P.(2018).Impactsoffishing,riverflowandconnectivitylossontheconservationofamigratoryfishpopulation.Aquatic Conservation: Marine and Freshwater Ecosystems, 28, 45–54. https://doi.org/10.1002/aqc.2831

Lindenmayer,D.B.,&Likens,G.E.(2009).Adaptivemonitoring:Anewparadigmforlong‐termresearchandmonitoring.Trends in Ecology & Evolution, 24,482–486.https://doi.org/10.1016/j.tree.2009.03.005

Lindenmayer,D.B.,&Likens,G.E.(2010).Thescienceandapplicationofecological monitoring. Biological Conservation, 143,1317–1328.https://doi.org/10.1016/j.biocon.2010.02.013

Lindenmayer, D. B., Likens, G. E., Haywood, A., & Miezis, L. (2011).Adaptive monitoring in the real world: Proof of concept. Trends in Ecology & Evolution, 26, 641–646. https://doi.org/10.1016/j.tree.2011.08.002

Lohammar, G. (1938).Wasserchemie und höhere Vegetation schwed‐ischerSeen.Symbolae Botanicae Upsaliensis, III, 1–252.

Lovett,G.M.,Burns,D.A.,Driscoll,C.T.,Jenkins,J.C.,Mitchell,M.J.,Rustad,L.,…Haeuber,R.(2007).Whoneedsenvironmentalmonitor‐ing?Frontiers in Ecology and the Environment, 5,253–260.https://doi.org/10.1890/1540‐9295(2007)5[253:WNEM]2.0.CO;2

Lowe, W., Likens, G. E., & Power, M. E. (2006). Linking scalesin stream ecology. BioScience, 56, 591–597. https://doi.org/10.1641/0006‐3568(2006)56[591:LSISE]2.0.CO;2

Lucas,M.C.,&Baras,E.(2000).Methodsforstudyingspatialbehaviouroffreshwaterfishesinthenaturalenvironment.Fish and Fisheries, 1, 283–316.https://doi.org/10.1046/j.1467‐2979.2000.00028.x

Lucas,M.C.,&Batley,E.(1996).SeasonalmovementsandbehaviourofadultbarbelBarbusbarbus,ariverinecyprinidfish:Implicationsfor

     |  745RADINGER Et Al.

river management. Journal of Applied Ecology, 33,1345–1358.https://doi.org/10.2307/2404775

Lundqvist, H., Leonardsson, K., Carlsson, U., Larsson, S., Nilsson, J.,Östergren,J.,Karlsson,L.,…Ferguson,J.(2010).MonitoringjuvenileAtlanticsalmonandseatroutintheRiverSävarån,NorthernSweden.InC.Hurford,M.Schneider,&I.G.Cowx(Eds.),Conservation moni‐toring in freshwater habitats (pp. 207–218). Dordrecht, Heidelberg,London,NewYork:SpringerScience&BusinessMedia.

Lyons, J. (1998). A hydroacoustic assessment of fish stocks in theRiver Trent, England. Fisheries Research, 35, 83–90. https://doi.org/10.1016/S0165‐7836(98)00062‐9

MacArthur,R.H.,&Wilson,E.O.(1967).The theory of island biogeogra‐phy.NewJersey:PrincetonUniversityPress.

MacKenzie,D.I.,Nichols,J.D.,Lachman,G.B.,Droege,S.,Royle,A.A.,&Langtimm,C.A.(2002).Estimatingsiteoccupancyrateswhende‐tectionprobabilitiesarelessthanone.Ecology, 83,2248–2255.https://doi.org/10.1890/0012‐9658(2002)083[2248:ESORWD]2.0.CO;2

MacKenzie,D.,Nichols, J., Royle, J., Pollock, K., Bailey, L., &Hines, J.(2006).Occupancy estimation and modeling: Inferring patterns and dy‐namics of species occurrence.SanDiego,CA:AcademicPress.

Magurran, A. E. (2004). Measuring biological diversity. Oxford, UK:BlackwellScienceLtd.

Magurran,A.E.(2011).Measuringbiologicaldiversityintime(andspace).InA.Magurran,&B.McGill(Eds.),Biological diversity: Frontiers in mea‐surement and assessment(pp.85–94).Oxford,UK:OxfordUniversityPress.

Magurran,A.E.,Deacon,A.E.,Moyes,F.,Shimadzu,H.,Dornelas,M.,Phillip, D. A. T., & Ramnarine, I.W. (2018). Divergent biodiversitychange within ecosystems. Proceedings of the National Academy of Sciences, 115, 1843–1847. https://doi.org/10.1073/pnas.1712594115

Magurran, A. E., &McGill, B. J. (2011).Biological diversity: Frontiers in measurement and assessment.Oxford,UK:OxfordUniversityPress.

Marsh,D.M.,&Trenham,P.C.(2008).Currenttrendsinplantandanimalpopulationmonitoring.Conservation Biology, 22, 647–655. https://doi.org/10.1111/j.1523‐1739.2008.00927.x

Maxwell, D., & Jennings, S. (2005). Power of monitoring pro‐grammes to detect decline and recovery of rare and vulner‐able fish. Journal of Applied Ecology, 42, 25–37. https://doi.org/10.1111/j.1365‐2664.2005.01000.x

Michener,W.K.(2006).Meta‐informationconceptsforecologicaldatamanagement. Ecological Informatics, 1,3–7.https://doi.org/10.1016/j.ecoinf.2005.08.004

Michener,W.K.(2015).Tensimplerulesforcreatingagooddataman‐agement plan. PLOS Computational Biology, 11, e1004525. https://doi.org/10.1371/journal.pcbi.1004525

Michener,W.K.,&Brunt,J.W.(2000).Ecological data: Design, manage‐ment, and processing.Oxford,UK:BlackwellScience.

Michener, W. K., & Jones, M. B. (2012). Ecoinformatics: Supportingecologyasadata‐intensivescience.Trends in Ecology & Evolution, 27, 85–93.https://doi.org/10.1016/j.tree.2011.11.016

Mihoub, J.‐B., Henle, K., Titeux, N., Brotons, L., Brummitt, N. A., &Schmeller,D.S. (2017).Settingtemporalbaselinesforbiodiversity:Thelimitsofavailablemonitoringdataforcapturingthefullimpactofanthropogenicpressures.Scientific Reports, 7,41591.https://doi.org/10.1038/srep41591

Milner, N., Wyatt, R., & Broad, K. (1998). HABSCORE ‐ applicationsand future developments of related habitat models. Aquatic Conservation: Marine and Freshwater Ecosystems, 8,633–644.https://doi.org/10.1002/(SICI)1099‐0755(199807/08)8:4<633:AID‐AQC275>3.0.CO;2‐7

Minteer,B.A.,Collins,J.P.,Love,K.E.,&Puschendorf,R.(2014).Avoiding(Re)extinction.Science, 344,260–261.https://doi.org/10.1126/science.1250953

Moe,S. J., Schmidt‐Kloiber,A.,Dudley,B. J.,&Hering,D. (2013).TheWISERwayoforganisingecologicaldatafromEuropeanrivers,lakes,transitional and coastalwaters.Hydrobiologia, 704, 11–28. https://doi.org/10.1007/s10750‐012‐1337‐0

Nichols, J., &Williams, B. (2006).Monitoring for conservation.Trends in Ecology & Evolution, 21, 668–673. https://doi.org/10.1016/j.tree.2006.08.007

Noble, R. A. A., Cowx, I. G., Goffaux, D., & Kestemont, P. (2007).Assessing the health of European rivers using functional eco‐logical guilds of fish communities: Standardising speciesclassification and approaches to metric selection. Fisheries Management and Ecology, 14, 381–392. https://doi.org/10.1111/ j.1365‐2400.2007.00575.x

Ormerod,S. J.,Dobson,M.,Hildrew,A.G.,&Townsend,C.R. (2010).Multiplestressorsinfreshwaterecosystems.Freshwater Biology, 55, 1–4.https://doi.org/10.1111/j.1365‐2427.2009.02395.x

Osenberg, C., Bolker, B., White, J., St. Mary, C., & Shima, J.(2006).Statistical issues and study design in ecological restorations:Lessons learnedfrommarinereserves. InD.A.Falk,M.A.Palmer,&J.B.Zedler(Eds.),Foundations of restoration ecology(pp.280–302).Washington,Covelo,London:IslandPress.

Peterman,R.M.(1990).Statisticalpoweranalysiscanimprovefisheriesresearchandmanagement.Canadian Journal of Fisheries and Aquatic Sciences, 47,2–15.https://doi.org/10.1139/f90‐001

Peterson,E.E.,&VerHoef,J.M.(2014).STARS:AnArcGIStoolsetusedto calculate the spatial informationneeded to fit spatial statisticalmodels to stream network data. Journal of Statistical Software, 56, 1–17.https://doi.org/10.18637/jss.v056.i02

Peterson,M.J.,Mathews,T.J.,Ryon,M.G.,Smith,J.G.,Christensen,S.W.,Greeley,M.S.,…Southworth,G.R.(2013).Y‐12 national security complex biological monitoring and abatement program plan. Oak Ridge, TN:U.S.DepartmentofEnergy.

Pielou,E.(1975).Ecological diversity.NewYork,NY:WileyInterscience.Pinder, A., Raghavan, R., & Britton, J. (2015a). The legendary hump‐

backedmahseerTor sp. of India’s River Cauvery: An endemic fishswimmingtowardsextinction?Endangered Species Research, 28, 11–17.https://doi.org/10.3354/esr00673

Pinder,A.C.,Raghavan,R.,&Britton, J.R. (2015b).Efficacyofanglercatch data as a population and conservation monitoring tool forthe flagship Mahseer fishes (Tor spp.) of Southern India. Aquatic Conservation: Marine and Freshwater Ecosystems, 25,829–838.https://doi.org/10.1002/aqc.2543

Poizat,G.,&Baran,E.(1997).Fishermen’sknowledgeasbackgroundin‐formation in tropical fish ecology:A quantitative comparisonwithfish sampling results.Environmental Biology of Fishes, 50, 435–449. https://doi.org/10.1023/A:1007317423165

Polasky,S.,Carpenter,S.R.,Folke,C.,&Keeler,B.(2011).Decision‐mak‐ing under great uncertainty: Environmental management in an era of global change. Trends in Ecology & Evolution, 26,398–404.https://doi.org/10.1016/j.tree.2011.04.007

Pollock, K. H., Nichols, J. D., Simons, T. R., Farnsworth, G. L., Bailey,L. L.,&Sauer, J.R. (2002). Large scalewildlifemonitoring studies:Statisticalmethodsfordesignandanalysis.Environmetrics, 13, 105–119.https://doi.org/10.1002/env.514

Pont,D.,Hugueny,B.,&Rogers,C.(2007).Developmentofafish‐basedindex for the assessment of river health in Europe: The EuropeanFishIndex.Fisheries Management and Ecology, 14,427–439.https://doi.org/10.1111/j.1365‐2400.2007.00577.x

Pope,K.L.,Lochmann,S.E.,&Young,M.K.(2010).Methodsforassess‐ing fishpopulations. In W.A.Hubert,& M.C.Quist(Eds.), Inland fisheries management in North America (pp.325–351).Bethesda,MD:AmericanFisheriesSociety.

Quinn,G.P.,&Keough,M.J.(2002).Experimental design and data analysis for biologists.Cambridge,UK:CambridgeUniversityPress.

746  |     RADINGER Et Al.

RCoreTeam.(2017).R: A language and environment for statistical comput‐ing.Vienna,Austria:RFoundationforStatisticalComputing.http://www.r‐project.org/.

Radinger,J.,Hölker,F.,Horký,P.,Slavík,O.,Dendoncker,N.,&Wolter,C.(2016).Synergisticandantagonistic interactionsof future landuseandclimatechangeonriverfishassemblages.Global Change Biology, 22,1505–1522.https://doi.org/10.1111/gcb.13183

Radinger,J.,&Wolter,C.(2014).Patternsandpredictorsoffishdisper‐salinrivers.Fish and Fisheries, 15,456–473.https://doi.org/10.1111/faf.12028 .

Reichman,O.J.,Jones,M.B.,&Schildhauer,M.P.(2011).Challengesandopportunitiesofopendatainecology.Science, 331,692–693.https://doi.org/10.1126/science.1197962

Revenga, C., Campbell, I., Abell, R., deVilliers, P., &Bryer,M. (2005).Prospectsformonitoringfreshwaterecosystemstowardsthe2010targets. Philosophical Transactions of the Royal Society B: Biological Sciences, 360,397–413.https://doi.org/10.1098/rstb.2004.1595

Rocha,L.A.,Aleixo,A.,Allen,G.,Almeda,F.,Baldwin,C.C.,Barclay,M.V.L.,…Witt,C.C.(2014).Specimencollection:Anessentialtool.Science, 344,814–815.https://doi.org/10.1126/science.344.6186.814

Rose, J. D., Arlinghaus, R., Cooke, S. J., Diggles, B. K., Sawynok,W.,Stevens,E.D.,&Wynne,C.D.L.(2014).Canfishreallyfeelpain?Fish and Fisheries, 15,97–133.https://doi.org/10.1111/faf.12010

Roussel,J.‐M.,Paillisson,J.‐M.,Tréguier,A.,&Petit,E.(2015).Thedown‐side of eDNA as a survey tool in water bodies. Journal of Applied Ecology, 52,823–826.https://doi.org/10.1111/1365‐2664.12428

Royle, J. A., & Link,W.A. (2006).Generalized site occupancymodelsallowingforfalsepositiveandfalsenegativeerrors.Ecology, 87, 835–841. https://doi.org/10.1890/0012‐9658(2006)87[835:GSOMAF]2.0.CO;2

Rüegg, J., Gries, C., Bond‐Lamberty, B., Bowen, G. J., Felzer, B. S.,McIntyre,N.E.,…Weathers,K.C.(2014).Completingthedatalifecycle:Usinginformationmanagementinmacrosystemsecologyre‐search.Frontiers in Ecology and the Environment, 12,24–30.https://doi.org/10.1890/120375

Sala, O. E., Chapin, F. S. III, Armesto, J. J., Berlow, E., Bloomfield, J.,Dirzo,R.,…Wall,D.H.(2000).Globalbiodiversityscenariosfortheyear 2100. Science, 287, 1770–1775. https://doi.org/10.1126/science.287.5459.1770

Sandlund,O.T.,Museth,J.,&Øistad,S. (2016).Migration,growthpat‐terns,anddietofpike(Esox lucius)inariverreservoiranditsinflowingriver. Fisheries Research, 173,53–60.https://doi.org/10.1016/j.fishres.2015.08.010

Santhanam, R. (2015).Nutritional freshwater life. Boca Raton, FL: CRCPress,Taylor&FrancisGroup.

Santos,A.M.,&Branco,M.(2012).Thequalityofname‐basedspeciesrecords indatabases.Trends in Ecology & Evolution, 27,6–7.https://doi.org/10.1016/j.tree.2011.10.004

Sass,G.G.,Cook,T.R.,Irons,K.S.,McClelland,M.A.,Michaels,N.N.,MatthewO’Hara,T.,&Stroub,M.R.(2010).Amark‐recapturepopu‐lationestimateforinvasivesilvercarp(Hypophthalmichthys molitrix)intheLaGrangeReach, IllinoisRiver.Biological Invasions, 12, 433–436.https://doi.org/10.1007/s10530‐009‐9462‐z

Schiemer,F.(2000).Fishasindicatorsfortheassessmentoftheecolog‐icalintegrityoflargerivers.Hydrobiologia, 422(423),271–278.https://doi.org/10.1023/A:1017086703551

Schindler,D.W.(1998).Whole‐ecosystemexperiments:Replicationver‐susrealism:Theneedforecosystem‐scaleexperiments.Ecosystems, 1,323–334.https://doi.org/10.1007/s100219900026

Schmutz,S.,Kaufmann,M.,Vogel,B.,Jungwirth,M.,&Muhar,S.(2000).Amulti‐levelconceptforfish‐based,river‐type‐specificassessmentof ecological integrity. Hydrobiologia, 422(423),279–289.https://doi.org/10.1023/A:1017038820390

Serrao,N.R.,Steinke,D.,&Hanner,R.H.(2014).Calibratingsnakeheaddiversity with DNA barcodes: Expanding taxonomic coverage to

enable identification of potential and established invasive species.PLoS ONE, 9,e99546.https://doi.org/10.1371/journal.pone.0099546

Simon, T. P., & Evans, N. T. (2017). Environmental quality assessmentusingstreamfishes.InG.A.Lamberti,&F.R.Hauer(Eds.),Methods in stream ecology. Volume 2: Ecosystem function(pp.319–334).London,UK:Elsevier.

Sloman,K.A.,Bouyoucos, I.A.,Brooks,E.J.,&Sneddon,L.U. (2019).Ethical considerations in fish research. Journal of Fish Biology, 94, 556–577.https://doi.org/10.1111/jfb.13946

Snyder,D.E.(2003).Invitedoverview:Conclusionsfromareviewofelec‐trofishinganditsharmfuleffectsonfish.Reviews in Fish Biology and Fisheries, 13,445–453.https://doi.org/10.1007/s11160‐004‐1095‐9

Southwood,T.,&Henderson,P.(2000).Ecological methods.Oxford,UK:BlackwellScience.

Steidl,R.J.,Hayes,J.P.,&Schauber,E.(1997).Statisticalpoweranalysisinwildliferesearch.The Journal of Wildlife Management, 61, 270–279. https://doi.org/10.2307/3802582

Stendera, S., Adrian, R., Bonada, N., Cañedo‐Argüelles, M., Hugueny,B., Januschke, K., … Hering, D. (2012). Drivers and stressors offreshwater biodiversity patterns across different ecosystems andscales:Areview.Hydrobiologia, 696,1–28.https://doi.org/10.1007/s10750‐012‐1183‐0

Stevens,D. L.,&Olsen,A.R. (2003).Varianceestimation for spatiallybalanced samples of environmental resources. Environmetrics, 14, 593–610.https://doi.org/10.1002/env.606

Stevens, D. L., & Olsen, A. R. (2004). Spatially balanced sampling ofnaturalresources.Journal of the American Statistical Association, 99, 262–278.https://doi.org/10.1198/016214504000000250

Stevens,D.L.,&Urquhart,N.S.(2000).Responsedesignsandsupportregions insamplingcontinuousdomains.Environmetrics, 11, 13–41. https://doi.org/10.1002/(SICI)1099‐095X(200001/02)11:1<13:AID‐ENV379>3.0.CO;2‐8

Stewart‐Oaten,A.,&Bence,J.R.(2001).Temporalandspatialvariationin environmental impact assessment. Ecological Monographs, 71, 305–339. https://doi.org/10.1890/0012‐9615(2001)071[0305:T‐ASVIE]2.0.CO;2

Strayer, D. L., & Dudgeon, D. (2010). Freshwater biodiversity con‐servation: Recent progress and future challenges. Journal of the North American Benthological Society, 29, 344–358. https://doi.org/10.1899/08‐171.1

Stribling, J.B.,Moulton, S.R.,& Lester,G. T. (2003).Determining thequalityoftaxonomicdata.Journal of the North American Benthological Society, 22,621–631.https://doi.org/10.2307/1468357

Stribling, J. B., Pavlik, K. L., Holdsworth, S. M., & Leppo, E. W.(2008). Data quality, performance, and uncertainty in taxo‐nomic identification for biological assessments. Journal of the North American Benthological Society, 27, 906–919. https://doi.org/10.1899/07‐175.1

Strobl,R.O.,&Robillard,P.D.(2008).Networkdesignforwaterqualitymonitoringofsurfacefreshwaters:Areview.Journal of Environmental Management, 87, 639–648. https://doi.org/10.1016/j.jenvman.2007.03.001

Sutter,R.D.,Wainscott,S.B.,Boetsch, J.R.,Palmer,C. J.,&Rugg,D.J. (2015). Practical guidance for integratingdatamanagement intolong‐termecologicalmonitoringprojects.Wildlife Society Bulletin, 39, 451–463.https://doi.org/10.1002/wsb.548

Takahara,T.,Minamoto,T.,Yamanaka,H.,Doi,H.,&Kawabata,Z.(2012).EstimationoffishbiomassusingenvironmentalDNA.PLoS ONE, 7, e35868.https://doi.org/10.1371/journal.pone.0035868

Thiault, L., Kernaléguen, L., Osenberg, C. W., & Claudet, J. (2017).Progressive‐ChangeBACIPS:Aflexibleapproachforenvironmentalimpact assessment.Methods in Ecology and Evolution, 8, 288–296.https://doi.org/10.1111/2041‐210X.12655

Thiem,J.D.,Taylor,M.K.,McConnachie,S.H.,Binder,T.R.,&Cooke,S. J. (2011).Trends in the reportingof taggingprocedures for fish

     |  747RADINGER Et Al.

telemetrystudiesthathaveusedsurgical implantationoftransmit‐ters:Acallformorecompletereporting.Reviews in Fish Biology and Fisheries, 21,117–126.https://doi.org/10.1007/s11160‐010‐9194‐2

Thomas, L. (1996).Monitoring long‐term population change:Why arethere so many analysis methods? Ecology, 77, 49–58. https://doi.org/10.2307/2265653

Thomsen,P.F.,Kielgast,J.,Iversen,L.L.,Wiuf,C.,Rasmussen,M.,Gilbert,M.T.P.,…Willerslev,E.(2012).MonitoringendangeredfreshwaterbiodiversityusingenvironmentalDNA.Molecular Ecology, 21,2565–2573.https://doi.org/10.1111/j.1365‐294X.2011.05418.x

Thorp, J.H., Thoms,M.C.,&Delong,M.D. (2006). The riverine eco‐system synthesis: Biocomplexity in river networks across spaceand time. River Research and Applications, 22, 123–147. https://doi.org/10.1002/rra.901

Troudet, J., Grandcolas, P., Blin, A., Vignes‐Lebbe, R., & Legendre,F. (2017). Taxonomic bias in biodiversity data and societal pref‐erences. Scientific Reports, 7, 9132. https://doi.org/10.1038/s41598‐017‐09084‐6

Turner, C. R., Uy, K. L., & Everhart, R. C. (2015). Fish environmentalDNAismoreconcentratedinaquaticsedimentsthansurfacewater.Biological Conservation, 183, 93–102. https://doi.org/10.1016/j.biocon.2014.11.017

Turner,M.G.,Gardner,R.H.,&O’Neill,R.V.(2001).Landscape ecology in theory and practice.NewYork,NY:Springer.

Valbo‐Jørgensen,J.,&Poulsen,A.F.(2000).Usinglocalknowledgeasaresearchtoolinthestudyofriverfishbiology:ExperiencesfromtheMekong.Environment, Developement and Sustainability, 2,253–376.https://doi.org/10.1023/A:1011418225338

VanLiefferinge,C.,Simoens,I.,Vogt,C.,Cox,T.J.S.,Breine,J.,Ercken,D., … Meire, P. (2010). Impact of habitat diversity on the sam‐pling effort required for the assessment of river fish communitiesand IBI. Hydrobiologia, 644, 169–183. https://doi.org/10.1007/s10750‐010‐0110‐5

Venturelli,P.A.,Hyder,K.,&Skov,C.(2017).Anglerappsasasourceofrecreationalfisheriesdata:Opportunities,challengesandproposedstandards.Fish and Fisheries, 18,578–595.https://doi.org/10.1111/faf.12189

VerHoef,J.M.,Peterson,E.E.,Clifford,D.,&Shah,R.(2014).SSN:AnRpackageforspatialstatisticalmodelingonstreamnetworks.Journal of Statistical Software, 56, 1–45. https://doi.org/10.18637/jss.v056.i03

Vidal,O.,García‐Berthou,E.,Tedesco,P.A.,&García‐Marín,J.‐L.(2010).Origin and genetic diversity of mosquitofish (Gambusia holbrooki)introducedtoEurope.Biological Invasions, 12,841–851.https://doi.org/10.1007/s10530‐009‐9505‐5

Vindenes, Y., Edeline, E., Ohlberger, J., Langangen, Ø., Winfield, I. J.,Stenseth,N.C.,&Vøllestad,L.A.(2014).Effectsofclimatechangeontrait‐baseddynamicsofatoppredatorinfreshwaterecosystems.The American Naturalist, 183,243–256.https://doi.org/10.1086/674610

Vines, T. H., Albert, A. Y. K., Andrew, R. L., Débarre, F., Bock, D. G.,Franklin,M.T.,…Rennison,D.J.(2014).Theavailabilityofresearchdata declines rapidly with article age. Current Biology, 24, 94–97. https://doi.org/10.1016/j.cub.2013.11.014

Vink,C.J.,Paquin,P.,&Cruickshank,R.H.(2012).Taxonomyandirre‐producible biological science.BioScience, 62, 451–452. https://doi.org/10.1525/bio.2012.62.5.3

Vörösmarty,C.J.,McIntyre,P.B.,Gessner,M.O.,Dudgeon,D.,Prusevich,A.,Green,P.,…Davies,P.M.(2010).Globalthreatstohumanwatersecurity and river biodiversity. Nature, 467, 555–561. https://doi.org/10.1038/natur e09440

Wägele,H.,Klussmann‐Kolb,A.,Kuhlmann,M.,Haszprunar,G.,Lindberg,D.,Koch,A.,&Wägele,J.W.(2011).Thetaxonomist—anendangeredrace.Apracticalproposalforitssurvival.Frontiers in Zoology, 8, 25. https://doi.org/10.1186/1742‐9994‐8‐25

Wagner,T.,Deweber,J.T.,Detar,J.,Kristine,D.,&Sweka,J.A.(2014).Spatialandtemporaldynamics inbrooktroutdensity: Implicationsfor population monitoring. North American Journal of Fisheries Management, 34, 258–269. https://doi.org/10.1080/02755947.2013.847878

Wenger,S.J.,&Freeman,M.C.(2008).Estimatingspeciesoccurrence,abundance, and detection probability using zero‐inflated distribu‐tions.Ecology, 89,2953–2959.https://doi.org/10.1890/07‐1127.1

Wenger,S.J.,Leasure,D.R.,Dauwalter,D.C.,Peacock,M.M.,Dunham,J.B.,Chelgren,N.D.,&Neville,H.M. (2017).Viabilityanalysisformultiplepopulations.Biological Conservation, 216,69–77.https://doi.org/10.1016/j.biocon.2017.10.006

Wheeler, K., Wenger, S. J., Walsh, S. J., Martin, Z. P., Jelks, H. L., &Freeman, M. C. (2018). Stream fish colonization but not per‐sistence varies regionally across a large North American riverbasin.Biological Conservation, 223, 1–10. https://doi.org/10.1016/j.biocon.2018.04.023

Wilde, G. R., & Fisher,W. L. (1996). Reservoir fisheries sampling andexperimental design. In L. E. Miranda, & D. R. DeVries (Eds.),Multidimensional approaches to reservoir fisheries management, vol. 16 (pp.397–407).Bethesda,MD:AmericanFisheriesSociety.

Winfield, I. J., Fletcher, J.M., & James, J. B. (2008). The Arctic charr(Salvelinus alpinus) populations of Windermere, UK: Populationtrendsassociatedwitheutrophication,climatechangeandincreasedabundanceof roach (Rutilus rutilus).Environmental Biology of Fishes, 83,25–35.https://doi.org/10.1007/s10641‐007‐9235‐4

Winfield, I. J., Fletcher, J. M., & James, J. B. (2010). An over‐view of fish species introductions to the English Lake District,UK, an area of outstanding conservation and fisheries impor‐tance. Journal of Applied Ichthyology, 26, 60–65. https://doi.org/10.1111/j.1439‐0426.2010.01504.x

Winfield,I.J.,Fletcher,J.M.,&James,J.B.(2012).Long‐termchangesinthedietofpike(Esox lucius),thetopaquaticpredatorinachang‐ing Windermere. Freshwater Biology, 57, 373–383. https://doi.org/10.1111/j.1365‐2427.2011.02607.x

Wolter,C. (2015).Historiccatches,abundance,anddeclineofAtlanticsalmonSalmo salar in the River Elbe. Aquatic Sciences, 77,367–380.https://doi.org/10.1007/s00027‐014‐0372‐5

Young,M.K.,McKelvey,K.S.,Pilgrim,K.L.,&Schwartz,M.K. (2013).DNAbarcodingat riverscape scales:Assessingbiodiversity amongfishesof thegenusCottus (Teleostei) innorthernRockyMountainstreams. Molecular Ecology Resources, 13, 583–595. https://doi.org/10.1111/1755‐0998.12091

Zale,A.V.,Parrish,D. L., Sutton,T.M.,&AmericanFisheriesSociety.(2012). Fisheries techniques. Bethesda, MD: American FisheriesSociety.

Zhang,H.,Wei,Q.W.,Du,H.,Shen,L.,Li,Y.H.,&Zhao,Y.(2009).IsthereevidencethattheChinesepaddlefish(Psephurus gladius)stillsurvivesin theupperYangtzeRiver?Concerns inferred fromhydroacousticandcapturesurveys,2006–2008.Journal of Applied Ichthyology, 25, 95–99.https://doi.org/10.1111/j.1439‐0426.2009.01268.x

SUPPORTING INFORMATION

Additional supporting information may be found online in theSupportingInformationsectionattheendofthearticle. 

How to cite this article:RadingerJ,BrittonJR,CarlsonSM,etal.Effectivemonitoringoffreshwaterfish.Fish Fish. 2019;20:729–747. https://doi.org/10.1111/faf.12373