Journal of Great Lakes Research

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1 Journl of Gret Lkes Reserch 43 (217) Contents lists ville t ScienceDirect Journl of Gret Lkes Reserch journl homepge: Performnce of four slmonids species in competition with Atlntic slmon Aimee Lee S. Houde, Chris C. Wilson, Bryn D. Neff, Deprtment of Biology, Western University, London, Ontrio N6A 5B7, Cnd Aqutic Reserch nd Monitoring Section, Ontrio Ministry of Nturl Resources nd Forestry, Trent University, Peterorough, Ontrio K9J 7B8, Cnd rticle info strct Article history: Received 29 My 216 Accepted 28 Octoer 216 Keywords: Ecologicl niche overlp Aggression Stocking Aquculture Survivl Growth Economiclly nd culturlly importnt slmonid species often compete with Atlntic slmon (Slmo slr) relesed from stocking progrms or tht escped during quculture production. Such competitive interctions my lower the individul fitness of these species y reducing survivl nd ody growth. Here, we exposed juvenile rown trout (S. trutt), rinow trout (Oncorhynchus mykiss), Chinook slmon (O. tshwytsch), nd coho slmon (O. kisutch) to juvenile Atlntic slmon in rtificil strems for 1 months. Survivl nd fitness-relted trits of the four species were not negtively impcted y the presence of Atlntic slmon. The results suggest tht rown trout nd rinow trout hve etter competitive ilities thn Atlntic slmon, nd tht Chinook slmon nd coho slmon hve limited competitive interctions with Atlntic slmon. Although we discuss certin environmentl conditions tht cn fvor Atlntic slmon s competitor t the juvenile life stge, Atlntic slmon my hve little impct on the productivity of these four species. 217 Interntionl Assocition for Gret Lkes Reserch. Pulished y Elsevier B.V. All rights reserved. Introduction Slmonids, such s Pcific slmon(oncorhynchus sp.), Atlntic slmon (Slmo slr), rinow trout (O. mykiss), nd rown trout (S. trutt), hve een intentionlly introduced glolly to provide fisheries, contriuting millions of dollrs to locl economies (Crwford nd Muir, 28; Gozln et l., 21). Slmonid quculture hs lso een expnding glolly nd my e source of unintentionl introductions of slmonids into foreign loctions (Nylor et l., 2; Bostock et l., 21). The intentionl nd unintentionl introductions of slmonids hve indvertently creted the potentil for interspecific competition with ntive slmonids (Crwford, 21). On one hnd, this interspecific competition my limit the production of these intentionlly introduced slmonids (Gozln et l., 21). On the other hnd, interspecific competition my negtively impct the production of culturlly or economiclly importnt ntive slmonid popultions (Hern, 1987; Fusch, 1988). A etter understnding of interspecific competition mong slmonids is therefore relevnt for oth supporting locl economies nd conserving ntive iodiversity (Simerloff nd Stiling, 1996; Gozln et l., 21). Interspecific competition is typiclly greter etween species with higher ecologicl niche overlp thn those with lower overlp (Hutchinson, 1957; Mskell et l., 26). Slmonids re territoril t juvenile life stges nd tend to compete for similr resources in nursery strems (Klleerg, 1958; Gison, 1981; Scott et l., 25), ut there re differences in the degree of niche overlp etween species (e.g. Corresponding uthor. E-mil ddress: neff@uwo.c (B.D. Neff). Gison, 1981; Helnd nd Bell, 1997). Competing individuls my reduce niche overlp y utilizing su-optiml hitts (McArthur nd Levins, 1967; Berg et l., 214; Houde et l., 216), which my reduce survivl nd growth (Hern nd Kynrd, 1986). Species tht re more ggressive my e more likely to secure optiml resources thn those tht re less ggressive (Holwy nd Surez, 1999). Overll, the extent of interspecific competition etween slmonid species pirs should covry with oth the degree of niche overlp nd interspecific differences in ggressive ehviour. Concerns hve een expressed tht Atlntic slmon my negtively impct the production of culturlly importnt ntive slmonids on the West Cost of North Americn where escpes from quculture net pens sometimes occur (Nylor et l., 2; Bostock et l., 21). Wild reproduction nd popultion estlishment from quculture escpes hve een identified s potentil thret to ntive popultions of Pcific slmon such s Chinook slmon (O. tshwytsch), coho slmon (O. kisutch), nd rinow trout, mong others (Volpe et l., 21; Piccolo nd Orlikowsk, 212; Fisher et l., 214). As these species support significnt fisheries nd re the focus of conservtion efforts on the West Cost (Willson nd Hlpuk, 1995), potentil ecologicl effects from quculture escpes nd estlishment of Atlntic slmon re significnt concern (Piccolo nd Orlikowsk, 212; Fisher et l., 214). Ech of these species s well s rown trout were historiclly introduced into the Lurentin Gret Lkes nd ecme nturlized (Crwford, 21; Stnfield et l., 26). Ironiclly, rehilittive stocking of Atlntic slmon in Lke Ontrio, where it ws historiclly ntive (Crwford, 21), hs een identified s potentil concern for ffecting the production of these nturlized introduced slmonids tht support economiclly importnt fisheries (Dietrich et l., 28), which hs een / 217 Interntionl Assocition for Gret Lkes Reserch. Pulished y Elsevier B.V. All rights reserved.

2 212 A.L.S. Houde et l. / Journl of Gret Lkes Reserch 43 (217) n issue for resistnce to the restortion of Atlntic slmon (e.g. Johnson nd Chlupnicki, 214). Although ntive species re highly vlued from mngement context, nturlized popultions of introduced slmonids re lso vlued components of fisheries mngement ojectives (OMNRF, 215). With mngement gencies employing risk-sed frmeworks for fisheries mngement, identifying potentil chllenges for sustinility is essentil for proctive policy decisions (OMNRF, 215). Atlntic slmon hs een shown to hve high niche overlp with rown trout nd rinow trout in nursery strems, where ech species tend to utilize riffle microhitts (e.g. Hern nd Kynrd, 1986; Armstrong et l., 23, ut see Johnson nd McKenn, 215). However, rown trout nd rinow trout tend to e more ggressive thn Atlntic slmon (e.g. Gison, 1981; Vehnen, 26; Vn Zwol et l., 212), suggesting tht oth species my e etter competitors thn Atlntic slmon under equl hitt conditions. In contrst, Atlntic slmon tend to hve low niche overlp with Chinook slmon nd coho slmon in nursery strems, s these ltter species generlly prefer pool microhitts (e.g. Helnd nd Bell, 1997; Holecek et l., 29), lthough Johnson nd Chlupnicki (214) showed tht juvenile Atlntic slmon nd Chinook slmon used similr hitt in two Lke Ontrio triutries. All three species lso tend to e eqully ggressive (e.g. Gison, 1981; Scott et l., 25). Further studies re wrrnted to test these expecttions of the outcome of interspecific competition etween Atlntic slmon nd these four other species. Here, we focus on the performnce of four slmonid species, rown trout, rinow trout, Chinook slmon, nd coho slmon, exposed to interspecific competition with Atlntic slmon. The present study is different from our previous studies using the sme rtificil strems, which insted focused on the performnce of Atlntic slmon in the context of restortion (Vn Zwol et l., 212,c; Houde et l., 215,, c). Additionlly, wheres nother study y Vn Zwol et l. (212) focused on interspecific competitive effects of Atlntic slmon on rown trout nd rinow trout during 7 dy trils, the present study exmines for the first time the performnce of ll four nturlized slmonid species in the Gret Lkes, nd over considerly longer time frme of 1 months. Methods Study species nd popultions Fry (ge + prr) of the four species were provided y Ontrio Ministry of Nturl Resources nd Forestry (OMNRF) fish culture sttions nd were trnsported to the OMNRF Codrington Reserch Fcility, Codrington, Ontrio in spring 211. Brown trout nd rinow trout were produced using htchery prents with ncestry to the Gnrsk River, ON. Coho slmon nd Chinook slmon were produced using nturlized prents from the Credit River, ON. Fry from the LHve nd Sego Atlntic slmon popultions were derived from offspring produced in fll 21 tht were rered t Codrington. The LHve popultion hs een red in cptivity in Ontrio since wild egg collections from the LHve River, Nov Scoti, Cnd ended in The Sego popultion ws imported into Ontrio s wild egg collections from Pnther River, Mine ( supplemented triutry of Sego Lke) in 26. Fry (n = 125) were held in species-specific tnks (18 L) nd fed to stition dily until trnsferred to the rtificil strems. Experimentl set-up Artificil strem tnks (width = 25 cm, length = 24 cm) were rrnged in six rows ech contining six tnks t Codrington. The sustrte ws composed of two prts grvel (2 64 mm) nd one prt cole ( mm) nd the tnks contined two types of microhitt: 16 cm riffle section (men ± 1SD nd rnge, velocity = 2 ± 6 nd 3 59 cm/s, depth = 28 ± 3 nd cm) followed y n 8 cm pool section (velocity = 7 ± 3 nd 3 15 cm/s, depth = 68 ± 3 nd cm). There ws no dditionl structure within the tnks. The sustrte composition, wter depth, nd wter velocity prmeters re within the nturl rnges preferred y ll five slmonid species (Johnson nd Kucer, 1985; Morntz et l., 1987; Bisson et l., 1988; Armstrong et l., 23; Holecek et l., 29). Fish were exposed to mient wter from Mrsh Creek (temperture = 8.5 ± 2.5 nd C) tht ws prtilly recirculted throughout the tnks rows with refreshing rte of.7 L/s. Totls of 32 fish were plced into ech rtificil strem tnk using sustitutive design (Fusch, 1998). The three tretments were ech species lone (e.g. 32 rown trout), species with LHve Atlntic slmon in equl numers (e.g. 16 rown trout nd 16 LHve Atlntic slmon), nd species with Sego Atlntic slmon (Electronnic Supplementy Mteril (ESM) Tle S1). Tnks were rndomly ssigned tretment nd there were two replictes per tretment. The species differed in ody size (see Tle 1), ut these differences re similr to those encountered in the nursery strems where the stocked fish experience interspecific competition. Fish remined in the tnks for 1 months (Septemer to July). During this period, the fish were given competition-inducing 3% ody mss rtion per dy (e.g. Grner et l., 28) Septemer to Decemer nd My to July, nd 1% ody mss rtion per dy Jnury to April, coinciding with colder wter tempertures. Rtions were delivered t the upstrem end of the strems once dy or twice dy with the rtion divided in hlf. Greter detils on the study species nd experimentl set-up re descried in Houde et l. (215). Survivl, ody size, nd riffle use The four species were mesured for survivl nd three fitnessrelted trits (ody length, mss, nd condition; Fusch, 1984, 1998). Riffle use ws lso exmined, s it is utilized microhitt of juvenile rown trout nd rinow trout, s well s Atlntic slmon (Hern nd Kynrd, 1986; Armstrong et l., 23). Mesurements were collected on Octoer 28, Novemer 29, nd July 24. On these dtes, ll juveniles were removed from the rtificil strem tnks, lightly nesthetized with MS-222, mesured for length (nerest.1 cm) nd mss (nerest.1 g), nd then llowed to recover efore eing returned to their tnk. Condition ws clculted s 1 mss / length 3 (Fulton, 194). To quntify riffle use, trined oserver took counts of the individuls of ech slmonid species within the riffle section t mid-dy the dy fter ody size mesurements. Riffle use ws lso exmined y tking photogrphs the dy efore collecting ody size mesurements, ut the dt were not collected for ll mesurement dtes. The nlysis ws therefore limited to the oserver dt, lthough the photogrphic dt showed similr riffle use results ptterns (dt not shown). Sttisticl nlysis of trits Survivl, ody length, mss, condition, nd riffle use of the four slmonids were nlyzed using R (ville t Sttisticl significnce ws set t α =.5. Individul vlues were used for ody size mesurements nd tnk vlues were used for survivl (proportion reltive to initil count) nd riffle use (proportion in the riffle section). Binomil models (or qusi-inomil models if there is dispersion) were used for survivl nd riffle use. Liner mixed-effects models using the R lmertest pckge were used to exmine effects for ody length, mss, nd condition. All models contined fixed effects for species, tretment, nd species tretment nd the mixed-effects models contined rndom effect for rtificil strem tnk identity. The trits were exmined t the 3 month mrk (Novemer 29) nd t the 1 month mrk (July 24) ecuse over winter mortlity cused differences in juvenile densities tht my influence these trits (ESM Tles S1 nd S2). Dt from the remining smple times re ville from the uthors.

3 A.L.S. Houde et l. / Journl of Gret Lkes Reserch 43 (217) Tle 1 Summry of the initil ody sizes of fry (ge + prr) for the four focl species (rown trout Slmo trutt, rinow troutoncorhynchus mykiss, Chinook slmon O. tshwytsch, nd coho slmon O. kisutch) nd two popultions of Atlntic slmon S. slr. Presented re mens ± 1SD. Different uppercse letters indicte significnt differences ssessed using Tukey's post-hoc multiple comprisons within species nd popultions for ech row (p.5). Smple sizes were: n = 128 for ech of the four focl species; nd n = 224 for ech Atlntic slmon popultion. Trits Slmonid species Atlntic slmon popultions Brown trout Rinow trout Chinook slmon Coho slmon LHve Sego Length (cm) 6. ±.7 A 6. ±.6 A 8.2 ±.6 B 8.5 ± 1. C 5.8 ±.4 D 5.6 ±.5 E Mss (g) 2.44 ±.92 A 2.2 ±.7 AD 5.92 ± 1.68 B 6.67 ± 2.29 C 2.17 ±.49 D 2.1 ±.52 D Condition (1 g/cm 3 ) 1.5 ±.6 A.99 ±.6 B 1.5 ±.1 A 1.5 ±.6 A 1.9 ±.6 C 1.14 ±.6 D Results Within the four species, there were few significnt differences in the responses to the two Atlntic slmon popultion tretments, i.e. species together with LHve or Sego Atlntic slmon (ESM Tle S3; Fig. S1). We therefore pooled these two popultion tretments together s generl species with Atlntic slmon tretment for the nlysis. Additionlly, in seprte experiment using the sme rtificil strems one yer lter which included nother Atlntic slmon popultion tretment (Lc Sint-Jen from Queec) ut no species lone tretment, we lso found tht within the four species there were few significnt differences in the response to the three Atlntic slmon popultion tretments (ESM Tle S3; Fig. S2). There were no significnt tretment effects for survivl nd riffle use teither3or1months(tle 2; Fig. 1). However, there were significnt tretments y species effects for ody length nd mss t 1 months ut not t 3 months. Brown trout nd rinow trout were longer nd hevier when held with Atlntic slmon thn when rered lone. In contrst, Chinook slmon nd coho slmon ody length nd mss were similr when rered lone or with Atlntic slmon t either time. For ll four species, there were no significnt effects of the presence or sence of Atlntic slmon on ody condition (Tle 2; Fig. 1). Tle 2 Summry of model results for trits of the four focl species (rown trout- Slmo trutt, rinow trout- Oncorhynchus mykiss, Chinook slmon- O. tshwytsch, nd coho slmon- O. kisutch). Displyed re qusi-inomil model results for survivl nd riffle use nd liner mixed-effects results for ody length, mss, nd condition. Species nd tretment were coded s fixed effects in ll models nd mixed-effects models contined rndom effect for rtificil strem tnk identity. The two tretments were ech of the four species lone nd species with Atlntic slmon (LHve nd Sego Atlntic slmon popultion tretments were pooled). Trit 3 months 1 months df F-sttistic p-vlue df F-sttistic p-vlue Survivl Species 3, , Tretment 1, , Species tretment 3, , Length Species 3, , Tretment 1, , Species tretment 3, , Mss Species 3, , Tretment 1, , Species tretment 3, , Condition Species 3, , Tretment 1, , Species tretment 3, , Riffle use Species 3, , Tretment 1, , Species tretment 3, , Discussion We found tht there ws little negtive impct of Atlntic slmon on the survivl nd fitness-relted trits of the four other slmonid species. Atlntic slmon tend to e less ggressive thn rown trout nd rinow trout (e.g. Gison, 1981; Vehnen, 26), ut just s ggressive s Chinook slmon nd coho slmon (e.g. Gison, 1981; Scott et l., 25). Consistent with these other studies, rown trout nd rinow trout hd smller ody sizes when rered lone thn when with Atlntic slmon; tht is, intrspecific competition for oth species ws greter thn interspecific competition with Atlntic slmon (Fusch, 1998). Furthermore, supporting evidence tht Chinook slmon nd coho slmon hve similr competitive ilities s Atlntic slmon, Chinook slmon nd coho slmon hd similr ody sizes whether lone or with the Atlntic slmon. Other studies hve lso oserved no negtive impcts of Atlntic slmon on the performnce of rown trout (e.g. Vehnen, 26; Vn Zwol et l., 212), rinow trout (e.g. Coghln et l., 27; Vn Zwol et l., 212), Chinook slmon (e.g. Scott et l., 25), nd coho slmon (e.g. Helnd nd Bell, 1997). Collectively these studies indicte tht these species re unlikely to e negtively impcted y competition with other species of lower or similr competitive ility. Beyond the degree of sptil niche overlp nd differences in competitive ilities etween species, nother importnt considertion for evluting the extent of interspecific competition is the degree of temporl overlp. Juvenile Atlntic slmon typiclly reside in strems for 2 yers in North Americ efore outmigrting s smolts (Klemetsen et l., 23). Similrly, juvenile rown trout nd rinow trout typiclly reside in strems for 2 yers (rnge 1 3 yers) with some individuls tht remin residents (Fusch nd White, 1986; Klemetsen et l., 23). In contrst, juvenile Chinook slmon nd coho slmon hve shorter residence times of 2 to 3 months nd 1 yer, respectively (Fusch nd White, 1986). Sptilly nd temporlly rown trout nd rinow trout my e exposed to higher interspecific competition with Atlntic slmon reltive to Chinook slmon nd coho slmon. Although we used ge + fish, which covered the residency period of Chinook slmon nd coho slmon, similr results to the present study were oserved for ge 1+ rown trout nd rinow trout using the sme rtificil strems (Vn Zwol et l., 212). Collectively these dt suggest tht Atlntic slmon hve little negtive impct on the survivl nd growth of ll four other species. Comprisons of the results using rtificil strems to nturl systems my hve limittions. The use of rtificil strems hs the dvntges of controlling environmentl vriles, such s wter velocity nd depth, nd incresing repliction which otherwise cn e more difficult to chieve using nturl strems (Fusch, 1988, 1998). On the other hnd, met-nlysis suggests tht rtificil strems cn overestimte the mgnitude (ut not direction) of competitive effects s compred to nturl strems (Korsu et l., 21). In prticulr, lortory studies my produce stronger responses to interspecific competition ecuse of generlly smller sptil scle reltive to nturl systems. Although the fish density in the rtificil strems ws likely higher thn tht experienced in nturl strems, suggesting the potentil for scle effects (e.g. Riley et l., 25), previous study found similrities in oth the direction nd mgnitude of Atlntic slmon responses to competition with

4 214 A.L.S. Houde et l. / Journl of Gret Lkes Reserch 43 (217) survivl (proportion) () 3 months survivl (proportion) () 1 months length (cm) (c) 3 months length (cm) (d) 1 months mss (g) (e) 3 months mss (g) (f) 1 months condition (1 x g/ cm (g) 3 months condition (1 x g/ cm (h) 1 months riffle use (proportion) (i) 3 months riffle use (proportion) (j) 1 months Fig. 1. Trits for the four focl species (rown trout- Slmo trutt,rinowtrout-oncorhynchus mykiss, Chinook slmon- O. tshwytsch, nd coho slmon- O. kisutch)inrtificil strem tnks t 3 nd 1 months. Tretment symols re SP = species lone, AS = species with Atlntic slmon (LHve nd Sego Atlntic slmon popultion tretments were pooled). Displyed re mens nd 1SE for tretments. Dshed lines re the mens for the species cross tretments. Different lowercse letters indicte significnt differences ssessed using Tukey's post-hoc multiple comprisons within species (p.5). rinow trout etween the sme rtificil strems nd nturl strems sites (Houde et l., 216). Regrdless, certin conditions within nturl systems my influence the outcome of interspecific competition (Finstd et l., 211). For exmple, the growth of juvenile rinow trout my e lower if Atlntic slmon re given prior residency (i.e. 3 dys, Volpe et l., 21) or if Atlntic slmon re stocked t high density into nturl strem (Dietrich et l., 28). Strem grdients nd temperture will lso likely influence competitive outcomes nd microhitt use etween rown trout, rinow trout, nd Atlntic slmon (Armstrong et l., 23; Coghln et l., 27; Dietrich et l., 28; Johnson, 216); nd s dults, spwning Atlntic slmon my lso interct with spwning individuls of the four species (Scott et l., 23, 25). It would lso e useful to compre multispecies performnce in nturl s well s experimentl systems (Fusch, 1998), so future studies should exmine competitive interctions of these species in nturl strems nd over their life cycles. Acknowledgements This reserch ws supported y the Nturl Sciences nd Engineering Reserch Council of Cnd through postgrdute student reserch wrd to ASH nd Strtegic Project Grnt to BDN. The reserch ws lso supported y the Ontrio government (Queen Elizeth II Grdute Scholrship to ASH), Ontrio Ministry of Nturl Resources nd Forestry (T. Stewrt, M. Dniels, D. Rosorough, C. Wever, nd P. Mlcolmson), the Ontrio Federtion of Anglers nd Hunters, nd Metro Est Anglers. W. Slon, S. Ferguson, B. Lewis, S. Howilth, nd A. Hunter provided invlule support nd ssistnce t the OMNRF Codrington Reserch Fcility. We thnk H. Dokter, A. Smith, X. He, C. Blck, J. Vn Zwol, S. Grner, T. Hin, N. Muñoz, K. Grdil, M. Lu, S. Shrron, C. Hoppe, M. Kurniwn, S. Currie, W. Yng, M. Browning, I. McKenzie, nd J. Lycock for ssistnce in rtificil strem tnk construction nd dt collection. We re grteful to the nonymous reviewers for their constructive comments on n erlier drft of the mnuscript. Appendix A. Supplementry dt Supplementry dt to this rticle cn e found online t doi.org/1.116/j.jglr References Armstrong, J.D., Kemp, P.S., Kennedy, G.A.J., Ldle, M., Milner, N.J., 23. Hitt requirements of Atlntic slmon nd rown trout in rivers nd strems. Fish. Res. 62, Berg, O.K., Bremset, G., Puffer, M., Hnssen, K., 214. Selective segregtion in intrspecific competition etween juvenile Atlntic slmon (Slmo slr) nd rown trout (Slmo trutt). Ecol. Freshw. Fish 23, Bisson, P.A., Sullivn, K., Nielsen, J.L., Chnnel hydrulics, hitt use, nd ody form of juvenile coho slmon, steelhed, nd cutthrot trout in strems. Trns. Am. Fish. Soc. 117, Bostock, J., McAndrew, B., Richrds, R., Juncey, K., Telfer, T., Lorenzen, K., Little, D., Ross, L., Hndisyde, N., Gtwrd, I., Corner, R., 21. Aquculture: glol sttus nd trends. Philos.Trns.R.Soc.BBiol.Sci.365,

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