Habitat enhancement and native fish conservation: can enhancement of channel complexity promote the coexistence of native and introduced fishes?

Habitat enhancement and native fish conservation:can enhancement of channel complexity promotethe coexistence of native and introduced fishes?

Eric J. Billman & Joshua D. Kreitzer &

J. Curtis Creighton & Evelyn Habit &Brock McMillan & Mark C. Belk

Received: 11 August 2011 /Accepted: 11 May 2012# Springer Science+Business Media B.V. 2012

Abstract Native fishes worldwide have declined as aconsequence of habitat loss and degradation and in-troduction of non-native species. In response to thesedeclines, river restoration projects have been initiatedto enhance habitat and remove introduced fishes; how-ever, non-native fish removal is not always logisticallyfeasible or socially acceptable. Consequently, manag-ers often seek to enhance degraded habitat in such away that native fishes can coexist with introduced

species. We quantified dynamics of fish communitiesto three newly constructed side channels in the ProvoRiver, Utah, USA, to determine if and how they pro-moted coexistence between native fishes (nine spe-cies) and non-native brown trout (Salmo trutta L.).Native and introduced fishes responded differently ineach side channel as a function of the unique charac-teristics and histories of side channels. Beaver activityin two of the three side channels caused habitat differ-entiation or channel isolation that facilitated the estab-lishment of native species. The third side channel hadgreater connectivity to and similar habitat as the mainchannel of the Provo River, resulting in a similar fishcommunity to main channel habitats (i.e. dominatedby brown trout with only a few native fish species).These results demonstrate the importance of under-standing habitat preferences for each species in a com-munity to guide habitat enhancement projects and theneed to create refuge habitats for native fishes.

Keywords River restoration . Side channel . Streamfish . Habitat heterogeneity . Refuge habitat . Fishconservation . Brown trout

Introduction

Native fish communities worldwide have been dra-matically altered as a consequence of habitat loss anddegradation and introduction of non-native species(Minkley and Deacon 1991; Ogutu-Ohwayo 1993;

Environ Biol FishDOI 10.1007/s10641-012-0041-2

Electronic supplementary material The online version of thisarticle (doi:10.1007/s10641-012-0041-2) containssupplementary material, which is available to authorized users.

E. J. Billman (*) : J. D. Kreitzer :M. C. BelkDepartment of Biology, Brigham Young University,401 WIDB,Provo, UT 84602, USAe-mail: [email protected]

J. C. CreightonDepartment of Biological Sciences,Purdue University Calumet,2200 169th Street,Hammond, IN 46323, USA

E. HabitAquatic Unit System, Environmental ScienceCentre Eula-Chile, University of Concepción,Concepción, Chile

B. McMillanDepartment of Plant and Wildlife Sciences,Brigham Young University,275 WIDB,Provo, UT 84602, USA

Bruton 1995; Townsend 2003; Habit et al. 2010). Overthe last century, in an effort to “develop” water forhuman uses and to control floods, rivers and streamshave been impounded, dewatered, and channelized.These activities directly eliminate waterways or theyreduce habitat complexity by minimizing such naturalstructures as meanders, pool-riffle sequences, back-waters, and side channels (Petersen et al. 1987). Inaddition, land use practices such as livestock grazing,mining, and timber harvest have led to habitat degra-dation and loss of complexity in rivers and streamsand their associated riparian areas (Allan and Flecker1993; Frissell 1993). Equally damaging in some sys-tems has been the introduction of non-native fish andother aquatic species that can adversely affect nativefish communities through competition, predation, andindirect effects (Lodge 1993; Townsend 1996; Mills etal. 2004; Olsen and Belk 2005; McHugh and Budy2006). The cumulative result of habitat degradationand non-native introductions has been a widespreaddecline of native fish communities and homogeniza-tion of resulting freshwater communities (Rahel 2000;Schiemer 2000; Rahel 2002).

In response to degradation of aquatic systems, therehas been great interest and activity over the past fewdecades aimed at repairing flowing water systems tothe extent possible through habitat enhancement(Bernhardt et al. 2005; Hilderbrand et al. 2005). Insome cases it is possible to both remove non-nativespecies and enhance habitat structure. However, inmany systems removal of non-native species is notlogistically possible or socially acceptable, and man-agers must attempt to enhance habitat and preservenative species diversity in a permanently altered sys-tem. In the context of river restoration, it has beensuggested that manipulating habitat to represent natu-ral habitat complexity, to which native species areadapted, may lead to coexistence between vulnerablenative species and introduced predators or competi-tors. Negative effects of introduced fishes may bealleviated if the enhancement of stream habitat eitherprovides necessary nursery and refuge habitat for nativespecies to avoid predation from introduced predators(Power 1984; Rosenberger and Angermeier 2003) orincreases habitat niche separation among native andintroduced competitors (Hasegawa and Maekawa2008; Hasegawa et al. 2010; Korsu et al. 2010b).Thus, enhancement of diverse and complex habitatstructure (both within given habitat types and among

habitat types) may provide a mechanism for recoveryand maintenance of native fish communities even insystems where non-native species cannot be eradicated.

Clearly it is important to understand the response ofthe biotic community to habitat manipulation to deter-mine if these management practices are successful inbolstering native fish populations. However, manyprojects are never monitored after project completion(NRC 1992), or only monitored immediately follow-ing project completion (Zedler 2000; Palmer et al.2005). Because one objective of stream enhancementprojects is persistence and an increase in native fishpopulations, it is the long-term pattern of fish commu-nity response to these efforts that will determine if thehabitat manipulation was successful. In addition, if co-existence is observed, it is not always clear what aspectsof the habitat manipulation contributed to the coexis-tence of native and introduced fishes. Alternatively, ifcoexistence does not result from the habitat enhance-ment, it is not clear what aspects were missing thatwould have otherwise successfully enhanced the de-graded habitat. To effectively assess a habitat enhance-ment project we must not only monitor over extendedperiods, but we must also gather data in such a way thatwe can distinguishmechanisms that promote coexistence.

The Provo River Restoration Project in central UtahUSA provided an opportunity to test the hypothesisthat enhancement of habitat can promote coexistenceof native and non-native fish species. The ProvoRiver, located in the Bonneville Basin in westernNorth America, has a drainage basin of 1761 km2

and a mean annual discharge of 9.9 m3/s (Shiozawaand Rader 2005). The river originates in the Uinta andWasatch mountain ranges and flows west into UtahLake. The middle section of the Provo River is an18 km segment bounded upstream by JordanelleReservoir and downstream by Deer Creek Reservoir.In addition to detrimental effects of dams and irriga-tion, this section of the river was highly channelized,and dominated by the introduced brown trout (Salmotrutta). Brown trout were first introduced into Utaharound 1900, and were likely stocked into the ProvoRiver shortly thereafter as fish were stocked regularlyacross the state in the early 1900s (Sigler and Miller1963). This species now drives a recreational fisheryin the Provo River that is economically important forthe region. Habitat alterations and interactions withbrown trout (competition, McHugh and Budy 2005;predation, Olsen and Belk 2005; Nannini and Belk

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2006) appear to have caused native species to declinein abundance or disappear from the main channel ofthe river. However, some of these species have beenable to persist in off-channel habitats such as sidechannels, backwaters, and cutoff pools in the fewunaltered segments of the river (Ellsworth 2003;Olsen and Belk 2005). In 1999 the Utah ReclamationMitigation and Conservation Commission began theProvo River Restoration Project in this section of theriver. One goal of the project was to facilitate the re-establishment of the native fish community in thepresence of brown trout by increasing habitat diversityby manipulating the river channel and flood plain toprovide more natural habitat (e.g. meanders and sidechannels). In this study, we quantified development offish communities in newly constructed side channels

to determine if they contributed to coexistence ofnative and non-native fishes.

Materials and methods

Side channels

We followed colonization and fish community develop-ment in three side channels that were constructed duringthe Provo River Restoration Project on the middle sec-tion of the Provo River (Fig. 1) for 2–4 years afterconstruction and again after 9–10 years to determinethe initial and long-term responses of fish communities.During the 8 year Restoration Project, approximately 15side channels were constructed; of these side channels

Fig. 1 Three side channelsand main channel reach onthe middle section of theProvo River, Utah, USA,that were sampled to deter-mine fish community re-sponse to habitatconstruction and enhance-ment as part of the ProvoRiver Restoration Project in1999 and 2000. Black linesrepresent the main channelof the Provo River whilegray lines represent sidechannels; dark gray linesrepresent sections of sidechannels that were directlyinfluenced by beaver damactivity in 2009. Inset showsthe location of the restora-tion area in Utah

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the first three side channels completed were selected forthis study. The long side channel, constructed in spring1999, partially follows the path of an old channel scar,and is approximately 1.65 km long, with moderate totight meanders. Width of the channel ranges from 2.5 to6 m, and depth ranges from 0.1 to 1 m, at low water inlate summer. The pond side channel and short sidechannel were both constructed in fall 2000. The pondside channel originates in a groundwater-fed pond andassociated wetland adjacent to the river, and is 0.83 kmin length. Width of the channel ranges from 1 to 3 m,and depth ranges from approximately 0.1 to 0.7 m, atlow water in late summer. The short side channel is0.21 km in length with few, large meanders, a widthranging from 4 to 7 m, and depth ranging 0.1 to 1 m.

The side channels were all constructed followingthe same design. After channels were configured,gravel was deposited at regular intervals to create apool-riffle sequence proportional to the width of thechannel. Therefore, we assume that each of these newside channels increases habitat complexity within theriver reach in a similar manner, and that initial pro-portions of habitats (i.e. pool, riffle, run) were similarin each side channel. We qualitatively documented anychanges in channel structure, and estimated the per-centage of the side channel that deviated from theinitial configuration at the end of the study period.

Fish community composition was determined byconducting snorkeling surveys of the entire length ofthe constructed side channels. Snorkeling surveys con-sisted of a single pass conducted in an upstream di-rection. While conducting a survey, one or twoindividuals (width of short side channel made twosnorkelers necessary) would snorkel while anotherindividual would record the species, number, and ageclass of the fish observed (juvenile or adult; seeTables 1 and 2 for size thresholds) and in whichhabitat the fish was located (pool, riffle, or run).Surveys were conducted mid-day (i.e. 1000–1600 h)during late July and early August each year. The longside channel was sampled in 1999 and 2000, and allside channels were sampled in 2001, 2002, and 2009.

We chose snorkeling as the method of fish samplingbecause it is the best technique for sampling juvenileand small-bodied fishes. However, detection probabil-ities can vary depending on observer, species, lifestage, time of day, flow, temperature, and other factorsaffecting water clarity (Li and Li 2006; Thurow et al.2006). During this study, four different snorkelers

conducted surveys; two snorkelers conducted the sur-veys from 1999 to 2002 and a different pair of snork-elers conducted the 2009 surveys. However, allsnorkelers were experienced in identification of re-gional native fishes and received the same project-specific training, thus minimizing observer bias.Surveys were conducted during the same time of dayand season to minimize the effects of flow, temperature,and other factors affecting water clarity. Thus, by stan-dardizing the survey methodology, we provide fishcommunity data for each side channel that can be usedto generate conclusions that are not biased due to largevariation in detection probabilities among surveys.

For each side channel, we calculated richness, di-versity (Shannon-Wiener index; Magurran 1988), andrelative abundance of each species for each survey. Wecalculated richness as the number of species by age-class combinations observed because in stream fishesage classes of the same species can function as differ-ent “species,” as a consequence of size differences(Werner and Gilliam 1984). Only one rainbow trout(Oncorhynchus mykiss Walbaum) was observed in allsurveys (long side channel 2001) and was not used incomparisons of fish communities. Rainbow trout arecommon in the reservoirs on either end of this sectionbut are not common in the river (Ellsworth 2003). Usingrelative abundance data from 2001, 2002, and 2009 foreach side channel, we tested for significant changes infish communities through time using an analysis ofsimilarity (ANOSIM; Primer v. 6; Clarke and Gorley2006). The fixed effect in the model was year. Prior toanalysis, we generated a similarity matrix based on theBray-Curtis similarity index (pair-wise similarities arehigher if samples are more similar and lower if samplesare dissimilar; Bray and Curtis 1957) comparing fishcommunities for each side channel and year combina-tion. The similarity matrix was used as the responsevariables in the ANOSIM.

We used ordination methods to determine if fishcommunities had converged or diverged over the long-term by visualizing the relationship of fish communi-ties for each habitat by side channel combination in2009. Fish abundances were fourth root transformedto reduce the influence of abundant taxa while stillaccounting for the presence of rarer taxa. We thengenerated a similarity matrix based on the Bray-Curtis similarity index comparing fish communitiesfor each habitat by side channel combination. To vi-sualize the relationship of fish communities among

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Tab

le1

Abu

ndance

ofspecies(#/sidechannel;entireleng

thof

each

side

channelw

assurveyed

each

year),speciesrichness

(S′),and

Shann

ondiversity

(H′)of

thelong

side

channel,

pond

side

channel,andshortsidechannelfor

each

yearside

channelsweresurveyed.S

pecies

richness

determ

ined

bynu

mberof

speciesandageclassesob

served.S

izethreshold(total

leng

th)fordistinctionbetweenjuvenilesandadultsof

each

speciesisindicatedin

parentheses.Dashesindicate

that

noindividu

alswerecollected

Lon

gside

channel

Pon

dside

channel

Sho

rtside

channel

Species

Age

class

1999

2000

2001

2002

2009

2001

2002

2009

2001

2002

2009

Catostomus

ardens

Utahsucker

Juvenile

–43

––

––

1–

––

–

Adu

lt(>

350mm)

1–

–1

3–

1–

––

–

Catostomus

platyrhynchu

sMou

ntainsucker

Juvenile

–28

539

––

69–

125

––

–

Adu

lt(>14

0mm)

24–

2–

–1

–16

––

–

Cottusba

irdi

Mottledsculpin

Juvenile

––

–21

––

7–

–30

–

Adu

lt(>

50mm)

51

––

112

3–

––

2

Lepidom

edaaliciaeSou

thern

leathersidechub

Juvenile

–14

––

––

––

––

–

Adu

lt(>

65mm)

–6

4–

––

––

––

–

Rhinichthys

cataractae

Lon

gnosedace

Juvenile

–86

––

––

––

––

–

Adu

lt(>

65mm)

3–

––

–4

––

––

–

Rhinichthys

osculusSpeckleddace

Juvenile

–19

––

–92

760

52

1–

Adu

lt(>

60mm)

27

––

8311

–69

9–

––

Richa

rdsonius

balteatus

Redside

shiner

Juvenile

––

–41

256

2915

8–

6–

Adu

lt(>

65mm)

––

720

191

5–

334

––

–

Salmotrutta

Browntrou

tJuvenile

194

1,17

71,12

237

210

018

410

7–

769

701

63

Adu

lt(>

300mm)

117

113

8329

91

––

1–

53

S′

710

66

710

76

34

3

H′

0.60

80.98

00.50

11.00

01.39

91.41

20.99

11.45

50.02

80.22

70.76

4

Environ Biol Fish

samples, we used non-metric multidimensional scaling(NMDS; Primer v.6; Clarke and Gorley 2006) to pro-duce two-dimensional plots. The unweighted pair groupmethod with arithmetic mean (UPGMA) was used todefine boundaries of similarity among samples. We thenused the similarity percentage procedure (SIMPER;Primer v.6; Clarke and Gorley 2006) to determine thespecies and age classes that were most important ingenerating the resulting patterns and differences amongsamples. For this comparison, we used the null hypoth-esis that fish communities would respond similarly toeach side channel because side channels were con-structed with a similar pattern of habitats. Therefore,any major groups apparent on NMDS plots were testedwith an ANOSIM to determine if the groups representedsignificant differences among habitats and channels.

Main channel fish community

We collected fish community data from a 200-m reachof the main channel of the Provo River (Fig. 1) to

compare to the fish communities in the side channels.This section of the main channel was also enhancedduring the Provo River Restoration Project in 1999and 2000 by removing or moving levees further awayfrom the river banks and adding meanders to the riverto allow for more natural geomorphic processes tooccur. Therefore, the native fish community couldhave responded to the increased habitat diversity inthe main channel; fish community change in the mainchannel could drive the patterns observed in the sidechannels. In the fall (October or November) of 2000,2004, and 2007, we sampled the reach using two-passdepletion electrofishing. An electric barrier was placedat the upper and lower ends of the reach. We countedall fish collected and recorded lengths for each fish.We were unable to estimate fish densities using deple-tion estimates for the native species captured becausethe fish occurred in such low densities. We thereforereport the total fish captured in the first pass. Speciesrichness and diversity for each year were calculated asdescribed above.

Table 2 Abundance of species (#/200 m; single pass), speciesrichness (S′), and Shannon diversity (H′) of the main channel ofthe Provo River for each year surveyed. Species richness deter-mined by number of species and age classes observed. Size

threshold (total length) for distinction between juveniles andadults of each species is indicated in parentheses. Dashes indi-cate that no individuals were collected

Species Age class 2000 2004 2007

Catostomus ardens Utah sucker Juvenile – – –

Adult (> 350 mm) 1 – –

Catostomus platyrhynchus Mountain sucker Juvenile – – –

Adult (> 140 mm) 1 – –

Cottus bairdi Mottled sculpin Juvenile – 16 1

Adult (> 50 mm) 22 176 31

Lepidomeda aliciae Southern leatherside chub Juvenile – – –

Adult (> 65 mm) – – –

Rhinichthys cataractae Longnose dace Juvenile – – –

Adult (> 65 mm) 2 2 1

Rhinichthys osculus Speckled dace Juvenile – – –

Adult (> 60 mm) – – –

Richardsonius balteatus Redside shiner Juvenile – – –

Adult (> 65 mm) – – –

Salmo trutta Brown trout Juvenile 106 82 18

Adult (> 300 mm) 143 217 85

Prosopium williamsoni Juvenile 12 – 1

Mountain whitefish Adult (> 200 mm) – 7 10

S′ 7 6 7

H′ 1.112 1.218 1.187

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Results

Side channels

Side channels were constructed to have similar habitatfeatures; however, changes across the study periodresulted in distinct differences among side channels(Fig. 2). The short side channel did not show notice-able changes in channel structure from its initial con-struction in 2000 to 2009. However, the long sidechannel was affected by beaver (Castor canadensisKuhl) activity shortly after it was completed. By2009, beaver activity influenced approximately 67 %of the long side channel at the upstream and down-stream ends, leaving the middle 33 % of the sidechannel that maintained its initial configuration. Thepond side channel was similarly affected by beaveractivity, only to a greater extent, resulting in 100 % ofthe side channel being altered by beavers. In 2009, afew large beaver ponds were found at the upstreamand downstream ends of the side channel, and manysmall dams across the remaining section of the sidechannel created a series of runs and pools with verylittle riffle habitat. Additionally, between 2002 and2009, beavers created a dam at the confluence of thepond side channel with the main channel Provo River,further isolating this side channel.

A total of nine species (seven native and two intro-duced species, including rainbow trout) and 17 speciesby age class groups was observed in the three side

channels (Table 1). Species richness and diversitywere highest in the long side channel and pond sidechannel (Table 1). During initial colonization of thelong side channel and pond side channel, speciesrichness for both channels reached a maximum of10. However, both richness and diversity fluctuatedinitially as species responded to the new side channels.In 2009 species richness was lower than initial peaksof richness, but species diversity was highest in 2009as the species present reached more even abundances(Table 1). The short side channel was dominated bybrown trout and had the lowest diversity and abundan-ces of native species (almost exclusively benthic na-tive fish; Table 1).

Patterns in relative abundances of native speciesand brown trout varied among side channels and acrossyears. Juvenile brown trout had the highest relativeabundance of all species in each of the three side chan-nels during initial colonization (Fig. 3). In the long sidechannel, juvenile brown trout remained the most abun-dant species until 2009 when adults of native speciesand brown trout had the highest relative abundances(Fig. 3). The pond side channel initially had high rela-tive abundances of both juvenile brown trout and nativespecies. However, brown trout were not present in thepond side channel in 2009, and juvenile and adult nativespecies had similar relative abundances (Fig. 3). In theshort side channel, juvenile brown trout always had thehighest relative abundance, although abundances of ju-venile and adult brown trout were more even in 2009. In

Fig. 2 Pictures presentinghabitat features in each sidechannel. a) pool and runhabitat in middle portion oflong side channel unaffectedby beaver activity; b) beaverdam on long side channel; c)slow pool habitat in pondside channel; d) riffle andrun habitat in short sidechannel

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the first two years following completion, native speciesand adult brown trout had either low relative abundan-ces or were absent from the short side channel, andrelative abundances of native species remained low in2009 (Fig. 3). While each side channel demonstratedunique patterns in fish community change acrosstime, there was a marginally significant year effectin fish communities across all side channels (R00.276,P00.064)

Non-metric multidimensional scaling of fish abun-dances in the habitats of each side channel in 2009revealed two main groups that represented significantdifferences in fish communities (R01, P00.018;Fig. 4). Pond side channel habitats and the pool habitatfrom the long side channel formed the first group. Theother group included all short side channel habitatsand the long side channel riffle and run habitats, and itwas connected to the previous group at 11 % similar-ity. Mean similarity among pond side channel habitatsand the long side channel pool habitat was 59 %, andwas determined mostly by adult redside shiner(Rhichardsonius balteatus Richardson; 33 %) andspeckled dace (Rhinichthys osculus Girard; adult30 %; juvenile 24 %). Mean similarity among shortside channel habitats and long side channel fast waterhabitats was 67 %, and was determined almost exclu-sively by brown trout (juvenile 64 %; adult 33 %).

Main channel fish community

As previously indicated, the main channel fish com-munity was dominated by brown trout whichaccounted for at least 60 % of the fish captured eachyear (Table 2). Of the native fish species, only benthicspecies were captured in the reach. Mottled sculpinwere second most abundant fish species in the reachfollowed by mountain whitefish and longnose dace(Table 2). Single individuals of both mountain andUtah suckers were captured only in the 2000, andthese species were absent from samples in 2004 and2007 (Table 2). Species richness exhibited little vari-ation among years (S′ range: 6–7 species; H′ range:1.112–1.218; Table 2).

Discussion

Side channel construction on the Provo River in-creased habitat complexity and facilitated the coexis-tence of native fishes with introduced predatory fishes.The fish communities in each side channel respondedto the increased habitat diversity provided by the con-structed side channels in a manner reflecting theunique habitat features and unique histories of eachside channel. In the long side channel, coexistencebetween native species and introduced brown troutoccurred at the local scale (i.e. within the side chan-nel). However, the pond side channel promoted

Fig. 3 Relative abundance of adult and juvenile brown troutand native fishes in three newly constructed side channels on themiddle section of the Provo River. Circles represent brown troutand inverted triangles represent native fishes. Open symbolsrepresent juveniles and filled symbols represent adults

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coexistence only at the reach scale (brown trout absentfrom the side channel). Over the period of this studyfish community dynamics in the long and pond sidechannels did not mirror changes in the main channelcommunity. Instead, the community in the main chan-nel continued to be dominated by brown trout withfew native benthic species (Table 2). Only the shortside channel, which had greater connectivity to themain channel compared to the other side channels,exhibited fish community dynamics that seemed tobe influenced by community dynamics in the mainchannel.

Native species were able to persist in the presenceof brown trout because they were able to find refuge inthe side channels. In a homogenous habitat (e.g. chan-nelized river lacking natural habitat complexity), preda-tor–prey communities exhibit unstable dynamics that donot allow long-term population persistence (Huffaker1958); this pattern was evident in the middle sectionProvo River prior to and after restoration (Table 2;Ellsworth 2003). The few native species that persist inmain channel habitats can do so because 1) they are ableto achieve a size refuge (i.e. Utah sucker [Catostomusardens Jordan and Gilbert] and mountain whitefish[Prosopium williamsoni Girard]) or 2) they are able tofind refuge in the interstitial spaces in the substrate andin fast water habitats where fewer and smaller browntrout occur (i.e. longnose dace [Rhinichthys cataractaeValenciennes] and mottled sculpin [Cottus bairdiiGirard]; Danehy et al. 1998; Naslund et al. 1998;

Ellsworth 2003). Following habitat enhancement, sidechannels provided native species access to refuge habi-tat where predators can not capture them or that repre-sents habitat unsuitable to predators.

The long side channel and the pond side channelprovided refuge habitat for native species throughhabitat differentiation and local isolation, both facili-tated by beaver activity in these side channels. In thelong side channel, beaver ponds provided habitat dif-ferentiation in which generalist species such as speck-led dace and redside shiner could find refuge frombrown trout in slow or stagnant water at the marginsof the ponds, habitat where brown trout were neverobserved during the day when surveys occurred.Impounded pools created by beaver activity, particu-larly the shallow margins, are likely poor foragingareas for brown trout because prey species have amplecover. Instead, brown trout occupied swift water hab-itat that represents optimal invertebrate foraging hab-itat, a niche that reduces predation pressure on nativefish species. Use of refuge habitat to avoid predationhas been documented in other stream fishes (Schlosser1987; Fraser and Gilliam 1992), including native fish-es in the Provo River drainage (Walser et al. 1999;Olsen and Belk 2005). The pond side channel was ableto promote coexistence of native and introduced spe-cies in the Provo River through local isolation. Thebeaver dam at the mouth of the side channel func-tioned similarly to waterfalls or fish passage barriersthat block the upstream spread of introduced species

Fig. 4 Non-metric multidi-mensional scaling diagramshowing the relationship ofhabitats based on fish abun-dances in the long sidechannel (LSC), pond sidechannel (PSC), and shortside channel (SSC) in 2009.Boundaries around samplesrepresent Bray-Curtis simi-larity levels of 50 %. Sym-bols represent habitat types:▲ 0 pool, ● 0 riffle, and ■ 0run

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(Hilderbrand and Kershner 2000; Avenetti et al. 2006;Rahel 2007). However, isolation via beaver activitywould be difficult to maintain because hydrologicaldynamics may provide connectivity during differenttimes of the year (i.e. high water) and because beaverdams (the agent of isolation in this case) are subject toa successional pattern as they are created and aban-doned (Snodgrass and Meffe 1998; Schlosser andKallemeyn 2000). The fish community in the isolatedpond side channel was contrasted by that in the shortside channel which, due to its connectivity to the mainchannel, had a fish community that was similar to themain channel (dominated by brown trout with fewnative species; Ellsworth 2003).

As previously mentioned, several factors can intro-duce bias to fish abundance estimates when usingsnorkel surveys (Li and Li 2006; Thurow et al.2006). Fish species can differ in detection probabilitydue to a combination of size, habitat use, and behavioras well as attributes of physical habitat (O’Neal 2007).In this study, we maintained a consistent methodologyacross all surveys such that it was unnecessary tocalibrate data prior to comparisons (i.e. all surveyssubject to the same bias). However, fish communitydata could be biased towards brown trout (i.e. higherrelative abundance) if native species had diel habitatpreferences due to the presence of brown trout (i.e.fish seek cover during day and are active at night). In2000, a night snorkel survey was conducted in thelong side channel to compare abundance estimatesbetween day and night surveys (SupplementalTable 1). The survey was conducted using similarprocedures previously described except the surveyoccurred at night beginning 1 h after sunset. Theproportion of native fish (juvenile and adult) countedincreased from 28 % in the day survey to 40 % in thenight survey. However, this change was driven not bya large increase in the number of native fish detected,but rather by a large decrease in the number of juvenilebrown trout counted (difference0694 fish; 53 % re-duction). Fish community data could also be biased ifsmall, bottom-dwelling species (e.g. mottled sculpin,longnose dace) are not detected. In 2009, only onemottled sculpin was counted in the long side channel.We conducted spot surveys by back-pack electrofish-ing fast water reaches in long side channel and did notcollect any mottle sculpin or longnose dace in approx-imately 100 m of stream sampled (E. Billman, unpubl.data). Given these evidences, we are confident that

snorkel surveys were reasonably accurate and thatthe conclusions of this study are valid.

Habitat enhancement can facilitate coexistenceamong native species and introduced competitorsthrough habitat niche separation (Hasegawa andMaekawa 2008; Hasegawa et al. 2010; Korsu et al.2010b). Homogeneous habitat, such as the channel-ized Provo River, reduces available niche space andincreases competitive interactions among species withsimilar niches. However, competitive interactions canbe reduced through habitat niche separation if com-peting species are able to differentially utilize avail-able habitat or resources, thus promoting coexistence(Nakano et al. 1999; McHugh and Budy 2005;Hasegawa et al. 2010). In the middle section ProvoRiver, two native species, southern leatherside chub(Lepidomeda aliciae Jouy) and Bonneville cutthroattrout (Oncorhynchus clarkii utah Richardson) havebeen negatively impacted by brown trout throughcompetition and predation, the latter being locallyextirpated, but have been able to coexist with browntrout at greatly reduced densities in other systems(Walser et al. 1999; Wilson and Belk 2001; de laHoz Franco and Budy 2005; McHugh and Budy2005; Billman et al. 2011). Southern leatherside chubwere stocked into the long side channel in 2000 inefforts to establish a population in the side channel(Ellsworth 2003); however, none of the fish wereobserved two years following the introduction andno juvenile fish were observed that would indicatesuccessful recruitment. The failure of the introducedsouthern leatherside chub to establish a populationdemonstrates the importance of accounting for allstressors that have caused population declines or localextirpation (Palmer et al. 2010). Simply increasinghabitat heterogeneity in the absence of non-nativeremoval or isolated habitat may result in limited suc-cess for native species that occupy similar niches asthe non-native species (Korsu et al. 2010a). However,persistence of southern leatherside chub and Bonnevillecutthroat trout in other systems with brown trout dem-onstrates that these species are able to coexist, presum-ably through habitat niche separation. Thus, furtherresearch should examine how southern leatherside chuband Bonneville cutthroat trout are able to coexist withbrown trout to establish criteria to guide habitat en-hancement projects for these two species.

The Provo River Restoration Project demonstratedthe need for an understanding of habitat preferences of

Environ Biol Fish

all native species to guide habitat enhancement effortsand the importance of monitoring to determine thelong-term efficacy of habitat manipulation (Zedler2000; Palmer et al. 2005). The amount of change infish communities in each side channel reflected theamount of habitat change that occurred after initialconstruction due to beaver activity. We expect thehabitat in the side channels to continue to vary spa-tially and temporally as they are influenced by geo-morphic processes and by beaver activity (Schlosserand Kallemeyn 2000). Therefore, the response of na-tive and introduced fishes to side channel constructionand other habitat enhancement efforts will not only bedependent on the initial characteristics of the sidechannel, but also the unique history of each sidechannel. Continued monitoring, particularly of sensi-tive species, will be necessary to determine the long-term efficacy of restoration efforts.

Acknowledgments Funding was provided by the Utah Miti-gation Restoration and Conservation Commission, the UtahDivision of Wildlife Resources (UDWR), and the Departmentsof Biology and Plant and Wildlife Sciences at Brigham YoungUniversity. Data for main channel surveys were provided byUDWR. Activities were conducted under permits obtained fromthe UDWR. Craig Ellsworth and Sage Kelley provided assis-tance during snorkeling surveys.

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