Genetic Structure of Anadromous Cutthroat Trout (Salmo Clarki Clarkil

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d1 ;:l t Geneticstructure of Anadromouscutthroat Trout (salmo clarki clarkil Populationsin the pugetSound Area: Evidencefor RestrictedGene Flow '

DonaldE. Camptont Washington Cooperativefrshery Research lJnit,2 Collegeof Fisheries,lJniversity of Washington,jeanle, WA 9) and FredM. Utter Northwest and AlaskaFisheries Center, National Marine Fkh.eqiesService,NationalOceanrc and etmo$heric Administration, 2725 Montlake Boulevardfasr, Seanle,WA ggl 12, IJSA

Campton, D. E', and F. M. Utter. 1987. Cenetic structure of anadromous cutthroat (Sa/rno populations trout clarki clarkil in the PugetSound area: evidence for restricredgene flow. Ci".J riit. Aluat. Sci.44: 573-582. -Cenelicrefationships among anadromous populations of coastalcutthroat trou | (Salmoclarki clarkilin puget Sound (United the area States)were investigated by electrophor"ticret-fr"a-s Oeh^/een successive year ctasses within amongstreams within drainages, i:':3,:t^lfJlations), benveendrainages wirhin each of tr,voregions separated Dyl'uget sound, and between the.two.regions. Average allele frequencies for fishf/om by.approximatelv itt" ttno[iiont iin"rea Q.t0.at severalpolyri'orphic loci,-suggestini-th.lft;"" non{ uet*een-it. tr"o regionsis restricted.Despite this divergence, populatiiis ihe sampled weie all uErysimitir i"iitiiirrv-iNii,s I > 0.92)i commonancestral invasion'foilowing.Pteistocenelticiatton. ihti;i;tG"e diversity(ex- f::gY'fj1"_._,ing-apecteoheterozygosity) wls Q.l0t andwas partitioned as follows: betr,veen regions, 1.24%; dtr"een drainigei, t.\lV:; amongstreams, 2.41%; year.classes,t.17vo; wittrin inJiviUiit6;;h;; addition, Qtween ;;;i;r, 94.2%.tn streameffects were significant in'7 of 12 intralocusiNOve i"rparisons, suggestingthat populations wercstructured geneticallyat thislevel of subdivision.This latter result may U" i"niiifiiir" f,oring instinctof spawningadults. Lesauteurs ont 6tudi6les rela-tions.g€n6tiquesenlre les populations anadromes de truitefardde (Salmo c/arkj clarki)dans.lar€gion de PugetSound-(Etats-Unis) a l'aide d-e rittt'ra* Jr".ii"p'rii-"ilq,iJ.irJii"rintuti6rement, ils ont 6tudi6 lesrelations entre.les. classes d'6ge successives dans un .ortt l;eiu ip"iiiriiii"i, L"trc lescours d'eaud'un bassinversant, entre les bassins versints ae aeux regions Jpireo parle pugetsound et entreles deux r6gionselles-m€mes. Les frdquences moyennes de allclesche;bs poil;;ift;rr-A;"ii"i,.i""["ta,environ plusieurs ,9:10i locuspolymorphes, ce qui port9..icroire sue i'e.ti"i" u"-ge-"J] r€gionsest restreint.Malgrd cet 6cart,les populations 6ihantillonnees itaient tr* irnbta-bt"t s6n6tiq;runi"Xrl'iJ;;; (l de Nei > traduitpeut-6tre une invasion commune aprds la ;, fl6i;]}[;.'ffii"#ite 9:27):(het€rozySotie,.r1.]i sl"iiition totatedes Senes attendue)s'6levait e 0,101,rdpartie comme suit: entre les regioni, i,tt%; versants, o/o; ;t;" bs bassins .1,01 entreles cottrs d'eau, 2,41 %; entreles classes d'Age, l,l7*; et entreles 6chantillons de 7o.De plus,l'incidence :1"-*::f.::l_!'?t"*?!^,r 9u corilJti, iuit-iisnin."rive dans7 dest2comparaisons AloyA, .tt'i porte) croireque. populations6taienatendtiguement structur6es oe5]1T'::yl sous-cllvls'on. ear .ce tes a ce niveau Cedernier r€sultat peut traduire l'instinct de retour au ruisseau natal prdsent cttezies gbniteuri adu|tes'll9E'rrgJL!|rs||9.|

ReceivedOctober 3, l9g5 AcceptedNovernber 10. l9g6 (JA6E) n.."p,!?'rf ::;::y; it8:,

oastalcutthroattrovi(Satno clarki ctarki)arcnative to and consistsof anadromousand.resident populations through- the west coast of North America from northern Cali- out its Jangc. Adults from anadromouspopulations generally fornia to the Prince William Sound arca of Alaska spawnin small coastalstr€ams and lowland tributarieJto major (DeWitt 1954; Scoa and Crossman1973). This sub_ rivers (Hartmanand Gill 1968).Resident populations arc specresinhabitsa variety rybi- of freshwaterand saltwaterhabitats cally foundabove migration barriers and in likes (e.g. NiGsbn andNorthcote l98l; Michael1983). I The hesent:ddress:-Departmentof Fisheriesand Aquaculture,Uni- migration habits of anadrcmouscutthmat trout in salt vcrsity of Florida, 7922 N.W. Tlst Street,Gainesville, FL 326M, waterare not well documentcdin thepublished literature. Field USA. data indicarc that tCooperatorS thesefish do not mi$ate to the open (rcean, _ arethe U.S. Fish and Wildlife Service,Washington but insteadremain near river mouthsind other estuarincarcas SaateDepartment of Fisheries,Washington State Departmeniof (Johnstonand Mercer 1976;Wydoski and Whitney 1979;and Game,and , the Universityof Washingtonl referencestherein). Tagging studies indicate that anadromous Can. J. Fish. Aquat. Sci., Vol.44. t9g7 573 r, .cqtthroattrout migrate along shorelines, but usually travel less thrn | 00 km from theirnatal streams (Giger 19721Jones | 977). ln general,these fish remainin salt wateronly 3-6 mo each year before retuming to freshwaterto either spawn(mature fish) or overwinter(immature fish). As a conseguence,only about507o of the fish constitutingan upstream migration ..run" are approachingsexual maturity (Johnston and Mercer 1976). Thesemigration habits differ from thoseof pacific salmon (Oncorhynchassp.) and steelheadtrout (Sarmogairdneri) which migrate hundreds,perhaps thousands, of kilometres throughoutthe north PacificOcean before rcturning to fresh- wateras matureadults (I*ggett 1977;Burgner t98d; Okazaki 1983a;and referencestherein). The hominginstinct of salmonidfishes (rcviewed in Hasler andScholz 1983; Stabell 1984) provides a behavioral-genetic mechanismfor the evolutionof reproductivelyisolatcd popu- lationsover smallgeographic arcas (e.g. Rymanet at. [gl9). Despitethis homingbehavior, most population genetic studies of anadromoussalmonid fishes have sampled populations over relativ-elylar-ge geographic areas in an attemptto detect ge- neticallydiffercntiated stocks of fish that caniubsequently-be identifiedin mixed-populationfisheries (e.g. Granteial. 1980; Utter et al. 1980; Okazaki 1983b;Fournier et al. 1984; Beachamet al. 1985a,1985b). In contrast,few studieshave intensivelysampled populations within relativelysmall geographic arcas. Such intensivesurveys can potentiallyyield informationregarding levels of geneflow (i.e.itraying) and the extent of population structuring on a microgeographicscale (Altukhov et al. 1975a,1975b; Parkinson 1984). Such infor- qratiol can further provide insightsregarding the evolutionary significanceof the homing instinctof thesefishes. . In this paper,we use electrophoreticmethods to investigate the geneticinfrastructurc of anadromouspopulations of coaital cutthroattnout in two regionsof the PugetSound area (USA). Ftc. | . Geographiclocations of samplcdpopulations (strcams) within Allele frequencieswerc compared at four levelsof population 1!e Puget Sound ana. Strcam names and catalog numbcrs (from subdivision:between successive year classeswithin itreams, Williamset al..1975)arp as follows. SkagitRivir: (l) Carpenter amongstr€ams within eachof four drainages,between drain- Crcek,0179; (2) WalkerCrcek, 0239; (3) WisemanCrcck, 021i0; (4) ageswithin eachof two geographicallyseparated regions, and Alder Crcck,0359. Stillaguamish River: (5) ChurchCrcek, 00lE; (6) bclweenthe two rcgions,respectively. A majorobjective of PortageCreck, CI36; (7) Fish Crcck,0038; (E) unnanrcd,00g0; (9) this study was to determine the relative amountsof genetic HarveyCreck, 0126; (10) Lime Clcck, 0147;(l l) unnamed,0lZ2; (12) Forrcr differentiationat eachlevel of populationsuMivision. Crcck,0330. Southern Hood Canal:(13) StimsonCrcek. 0488;(14) Littlc MissionCreek, 0493; (15) Big MissionCreek, (X95; I (16) Materials and Methods unnamedr.Oa.9Q;(17) Union River, 0504 and 0502 lpooted). NorthernHood Canat (18) Howe Creek,0090; 09) Tarbd Creek. SampledPopulations 0129;(20) unnanpd,0130;(2t ) ThorndykeCreek, 0170. Howe Crcek is a tributaryto drc Littte QuilcencRiver.'Approximatety lfi) frsh Juvenilecutthroat trout werecollected, by electroshocking, reprcsentingtwo agcclasscs (age 0* and age >l*) werecollected from severalsmall strcamsin the PugetSound area during froqr eachstrc1{r: Samplesite locationswithin eachsueam are given Septemberand October 1977 (Fig. l). Thesesrreams are in Campton(1981). locatedin two distinctregions: the northPuget Sound region, rcprcsentedby the Skagir ana Stillffie approximately 40 to 75 mm (FL), while the lengths of the age UooACCId3gion, rcpresentedby four northernstrcams and I + fish werc gencrally gttatcr than 95 mm. The two age clais five southernstieams. The sdmplingdesign was hierarchical, groups thus fonrpd two distinct size distributions, and werc with streamsnested within eachof four drainagearcas and two tneatedas indcperdcnt samplesfrom a single population within drainagesnested within eachrcgion. Most strcamswithin the each strcam. All fish were lessthan 150 mm in length and werc Hood Canalregion are small crceksflowing dircctly into salt believed, at the time of collection, to be prcsmolt juveniles water whereasstr€ams in the north PugetSound rcgion are rcpresentinganadromous populations. Approximatety t OOnsn tributariesto one of the two majorrivers. from eachsamplc site werc retainedfor electrophoreticanal- Samplesof cutthroattrout from eachstrcam were divided ysis. All fish werefrozen in the field usingdry ice. into two ageclasses: young-of-the-year fish (ege0+) andfish Both cutthroatand steelhead trout juveniles w€re prcsent at = greaterthan I yr of age(age | + ). Age determinationswer6 many sample sites, but werc very difficult to distinguish basedon the length-frequencydistributions of individuals morphologicallyundcr field conditions.Consequently, we dis- frorneach sample site and scale readings for subsamplesof fish tinguishedthe trro speciesin the laboratoryusing electro- (Ricker 1975).The lengthsof the age0+ fish rangedfrom phoreticcriteria (Campron and Utter 1985). 574 TABLEf . Enzymesand loci examincdin s. clarki clarki. Buffersystems I, ll, and lll weredescribed by Ridgwayet al. (1970),Markert and Faulhaber(1965), and ctayton and_Tretiak(1972), rcspectively. Buffer sysremlV was deviscdby corpling the gct buffer from clayton and rrctiak ( | 972) with clecuodebuffer t rroni straw ana prasao (1970). TissuesM. L, and E rcfer to muscle,liver, and eye, rcspoctively.Loci in parcntheseshave common allcles of identicalelectrophoretic mobilitics ard areconsid- ercdto be of duplicatedorigin.

Enzyme(8.C. No.) L.oci Tissuc Buffer Alcoholdehydrogenase (1.l. L l) ADH LI Aspartateaminotransferas€ (2.6. | . l) A/tT-(1,2) MI AAT.3 EII Creatinekinue (2.7.3.2) cK-(r,2) MI Dipcpidase(3.4. t3. I l) GLD.I M,E l,ll (substrate:glycyl-leucine) GLD2 EI Glucosephosphabisomcrase (5.3. 1.9) GPI.I,2 M t. GPI.3 M,L .I Glycerol-3-phospharcdchydrogenase ( l. l. 1.8) G3PDH.I,2 Mtv Isocitratedehydrogenase (l . | . 1.42) IDH-1,2' Mlv IDH-(3,4) L||l Lactatedehydrogenasc (1.1.1.27) I.DH.I,2 M1 LDH.3 M,E I,II LDH4 M,L,E I,t,tl LDH.5 Etl Malatcdehydrogenase (1.l. 1.37) MDH-(t,2) L III MDH-(3,4) M1 lv Malicenzyme (1. l. 1.40) ME'(1,2f trf lV ME.3' M, L rV, ill ME4 Ltv Mannoscphosphateircmerase (5.3. 1.8) MPI Eil Phosphoglucomutasc(2.7.5. | ) POM-2b MI Phosphogluconatedehydrogenase (1. |. t.44) PGD M, L lV, Ilt Sorbitol(lditol) dehydrogerrase(1. l. l. 14) SDH.I,2 LI Superoxidedismutase (1. 15. l. l) SOD LI

These loci werp difficult to resolve and werc examinedin only a fcw samplcs. Sour loci arc pr€sentin rainbow tnout.

Althoughall populationswere thought to be anadromousat Statistics thetime sampleswere collected, we laterlearned that an earlier lqdy haddetermined that the Howe Crcek population (No. lg, Average hctcrozygositiesper population wer€ estimated Fig. l) wasnonanadromous (Dr. I-aurcnDonaldson, School of from the allele frcqucnciesat eachlocus (Nei and Roychoud- Fisheries,University of Washinglon,Seanle, pers. comm.). hury 1974). Data for both ycar classeswcrc pooled in these This earlierresult was confirmed by thepresencC in our sample calculations. of a l30-mm-long female with maturinggametes (reveaied The genetibhaerogeneity associated with eachhierarchical during preparationof tissuesfor electrophorcsis).We include level (rcgions,drainaggs, sftafns, and yearclasses) was quan- hereallele frequencies for this nonanadrbmouspopulation be- tified by Nei's (1973)genc divcrsity analysisusing the algo- causethese allele frequenciesdiverged somewhat from those rithm of Chakrabortyet d. (1982).ln addition,variance com- for.the anadromouspopulations, and thus provideadditional ponentsat eachleral of suMivision were estimatedand tested insights regardingthe effects of gene flow on population for statistical significarrccby a ncsted analysisof variance structures. (Sokal and Rohlf t969) using the arcsine-ransformedfre- quency (in degrccs)of thc most commonallele at each poly- Electrophoresis morphic locus. Datafor thc nonanadnomousHowc Creekpop Horizontal starch-gel elecaophoresisfollowed the pro- ulationwere excluded from thcsetno hierarchicalanalyses of 9e{rresof May et al. (1979).Fifteen enzymes rcF€senting 3l populationstructure. loci were examinedelectrophoretically (Table l). t-oci ana The geneticrelationships among all populationswere graph- alleleswere designatedaccording to the nomenclaturepro- ically representedin two dimcnsionsby calculatingNei's posgi by Allendorf and Utter (1979), excepr that atfulic (1972)index of geneidentity bctween all populationpairs and mobilities were measuredrelative to the commonallele in projectingthese multidimensional relationships onto the plane S. gairdneri (Campton and Utter 1985). Several isozyme formedby the fint two principal coordinateaxcs (Gower 1966; systemswere composedof two loci with commonalleles of Everitt 1978).Eigenvector components were scaled such that iderycal electrophorcticmobility, and theseduplicated loci their sumsof squareswere equalto the correspondingeigen- (MT- 1,2, CK- 1,2, IDH -3,4, MDH- t,2, andMDH -3,4) were value.This scalingallowed distances in the transformedspace treatedas two disomicloci with identicalallele frequencies. to reflectthe variancesassociated with eachprincipal axis. Can.J. Fish.Aquat. Sci., Vol.44, 1987 575 Tesle 2. Compositcallcle freguenciesat polymorphicloci for all fish coltectedfrom 91c! of the four drainagearcas and Howecreck. A total of 354, tm6, 402, 433, and E9fish werecollected from the four drainagcareas and Howe creck, rcspectively.toci not listed werc monomorphicfor the sameallcle in all populations.

North PugetSound Hood Canal Hor{c Locus Alleles Skagit Stillaguamish South Creek AAT-1,2 r00 0.870 0.841 0.856 0.849 0.767 E 0.t30 o'jn 0.t33 0.t29 0.233 70 0.0tI 0.021 -r00 ADIT 0.990 0.980 0.990 0.929 t.000 -2n 0.0t0 0.020 0.010 0.071 GLD-I t20 0.033 0.030 0.02t 0.065 I I0 0.925 0.9r5 0.794 0.8t9 0.966 IA 0.043 0.056 0.t84 0.1t7 0.034 GPI-I 154 0.239 0.368 0.234 0.32E 0.052 r00 0.727 0.625 0.639 0.6t6 0.865 E 0.034 0.006 0.t27 0.056 0.073 GPI.2 t90 0.003 0.001 154 0.997 0.3 o.sgr o.gq 0.983 rco 0.007 0.006 0.0t7 I5 0.001 /- G3PDH.I t00 0.003 -t00 t.000 0.97 r"000 to00 l-000 IDH.3,4 124 0.001 0.00r rN 0.092 0.099 0.045 0,(pl 0.003 72' 0.926 0.792 0.938 0.684 0.9n 'U 0.083 0.r09 0.017 0.225 LDH-3 I4I 0.009 0.m4 0.009 100 1.000 o.982 0.996 0.99t l.0m 52 0.009 LDH4 In 1.000 >0.999 0.999 0.987 r.000 74 <0.00t 0.001 0.003 MDH.I,2 132 0.001 rN 0.980 0.%l lJ00 0.95 rs00 4E 0.020 0.038 0.005 MDH.3.4 Irc 0.0t3 <0.00t 0.018 0.005 n0 0.938 0.93s 0.843 0.845 0.579 I Es o.ml <0.001 0.001 78 0.048 0.065 0.t39 0.150 0.421 I rc 0.991 0.993 0.986 0.988 1.000 100 0.009 0.007 0.0t4 0.012 MPI rco 0.936 0.941 0.983 0.982 0.93E 95 0.064 0.059 0.017 0.0t8 0.062 PGD t05 0.017 0.028 IN O.gy 0.952 0.919 0.977 l.om n 0.049 0.020 0.021 0.023 PGM 100 0.963 0.970 0.E92 0.876 0.9% E5 0.037 0.030 0.r08 o.tu 0.006 SDH.I 230 0.001 0.00t 0.010 0.012 r90 0.866 0.933 0.808 0.78s 0.547 100 0.t34 0.067 0.191 0.205 0.u2 SOD 142 0.t86 0.213 0.087 0.071 0.056 r00 0.814 0.787 0.913 0.929 0.9M 'TJne 72 alleleconsists of threeelectromorphs , 6s, n, and80, which aredifficult to distinguishelectrophorctically.

576 Can. J. Fish. Aquat. Sci., Vol.44, 1987 Results populationsor sbeams,similar to percentagesfor other ana- drcmoussalmonid fishes in westernNorth Amcrica (Okazaki Seventeenisozyme systems representing 2l loci werepoty_ l?!1!; Ryman l9E3; Gyltenstent985; Witmot and Burgner morphicin oneor morcpopulatiohs (Tablj2). Averageheter6_ l98s). zygositiesper population ranged from0.0g0 to 0. 129and aver- The north PugetSound and Hood Canalpopulations were aged0.097. Severalloci hadcommon alteleswith composite projectedas two distinct ard nonoverlapping-groupsin the frequenciesless than 0.95. These altelefrequencies arc ploned -- planeof the first two prirrcipalcoordinate-axeJ(Fig. +y. eopu- for^gc.hof the 2t populations(streams) ' inFig. 2 urdr.l lationsfrom the Skagitand-stillaguarirish riven werc not dis- Allele frequencyvariarions within eachof th1 four levetsof $nguishedwithin the north pugJt Soundregion, but popu- populationsubdivision were similar at severalloci (Fig. 2). lations from the rprthern and southemarcaJof Hood bahal Averageallele freguencies for the north.pugetSound and Hood wcreclearly separarcd into two distinctsubgroups. In addition, Laral regions differed by approximately 0. l0 at GLD_I, the nonanadromousHowe Creckpopulatioi wai projectedas a MDH-3,4, SOD, pGM, na Sbnl . Also, manyminor allelei distinct outlier. Theseprojected rclationships iccountcd for wereobserved in only oneregion (Table 2). In Lonrast,allele 56.8%of thc total variationin geneidentiry values (Nei 1972) frequencydifferences betweln drainage arcas within each and clearly reflectcdthc betweeri-populationaverages of thesi regionwere gcneraly small (<0.10), exiept atIDH-3,4where values(Table 5). Tlreprojected reiationships werc ilso consis_ ttre aJelaggfrequency of the 72 allele differed by approxi_ tcnt with the resultsof the genedivercity analysis (Table 4). mately0.25 betweenthe northern andsouthern areas or Hooa Despiq this populationstru;ntring, gene identities c-anal(Table 2). Altere frequencies for the nonanadromous poprlationswerc grcaterthan 0.97 ind were thus"rong similar "il to Howe Creekpopulation (No.- lg) wercdistinctive or inconsis- [gs,e.for local populationsof a wide varietyof species(Avise tent at severalloci. t975\. Allele . frequencydiffercnces between year classeswithin streams..w-eregenerally small (0.0-0.15), exceptat Gpl-l Discussion where differencesbetween year classeswere rclativety large somepoputations{Fig. 3).This I !i9-101tur tauerresritt miy PopulationSructure navebeen caused by the possiblemisassignment of allelesto GPI-I and Gpt-Z, iince Lotn to"i *ir" filyrorphic for the Anadromouspopulations of coastalcutthroat tnout within the commonallele of the other locus(Table 2). However,most Puget ASound arca constitute at least three genetically individuals had at reasttwo copiesof theI3l ailereand were groupsja north puget Soundgroup contaiiing popu- thus interprered $v.erge1t as homozygotisat Gpl-2 (seeTable 2). lations.fro_mth9 andStillaguamish rivirs andtwo-gloups Varilnce components lkagit ._ derivedfrom the analysisof variance frromthe Hood Canal region mnaining poputationsfrom tire rcglol,_ lS drainage, and stream effects werc significant northernand southemdrainage arcas, rcspectively. These ge- (P 0.05) -re- -< at seven, two, and seven loci, resrtctineiy netic rclationships(Fig. 4) arc similar td ttre gcographic 3). (T1bIe The two significantrcsults ior drainag; effects tanonshtpsamong thcse poprlations at the regionand drainage (A?H,. P < 0.05; IDH-3,4.,,_P< 0.001) werc-primarity lcvels of suMivision (Fig. tl ard suggcstI concspondenie reflecting allele frcquency differcncesbetween the northern between gcographic and gcnetic distances(scc Filsenstein ano southern.areas of Hood Canal;differences bctween the 1982). Sfpi!1{ S_ti[lguamish rivers at theserwoioci werc negti_ The consistcntdifferences in altele frequenciesbetween the giblc (Table2: Fig. 2). Thesignificant resuris for strcanreffects north Rrget Soundand Hood Canal populationssuggest are especially that noteu,orthy becausethis heterogeneitywas geneflow is resficted at this level of subdivision.lagging measurcdrelative to the differcnces between ti" t*o ye"r studies in southeastAlaska support this interpretation;-inal classeswithin each str€am. dromouscutthroat hout do not niigrate acrosslarge bodiesof of gene ^_-CjTlo1rnts diversitiesamong subgroups within water (3-8 hm) but insteadfollow shorclines(Jones 1977). population ,tff1,_t"I:t,of subdivision*erc ge-neoitysmall Rrget Sound may thus rcprcsenta migration barrier to ana- but clearlyg{lected the ailetefrcqruency iistribu_ dromouscutthroat tout (socFig. I). hons!,^1,:j), (Fig. Nsvcrthetess,the samplcd 2 and 3). Differencesin ailerefrequeniies at the poprlationswerc all vcry simitargcnerically (/ > rcqiol, 0.97), ios- ^drainage,stream, and yearclass levels accounted for sibly reflecting a commonaneeenal invasion fo[owing'the o1ly 1.2!, 1.01,2.41, andt.i7Eo, respecdv;ly, of the total reheatof glacial lobc appmximatelyl0 000 yi ago genediversity. 1!e_|rect :l=::l However,the distribution of this geni (!ono1 l9E0). Thc genericdivc-ri;cnce bctwecn the northern dlversrtydiffercd among populationswithin eachregion. 6nly and.sou-thernpopulations of Hood Canal was due primarily to 0.36Voof the gene Aiv-eisiiywithin the nortf, nulet Souni differenccsat a single regiol was 1-l:l: -fr"qurncy isozyme sysrem causedby differcncesin allelefrequencies between (lDH-3,4) g! tay thuswarrant the furtheritudy wiih morepop- skagir and Stillaguamishrivers, while Z.99Voof this ulationsand loci. overstty occurredamong strcamswithin drainages.In con- The divergent allele frequenciesfor the nonanadromous trast,the_diversity between _- the northernand southim drainage Howe Creek populationstrongly suggesta correspondencebe- areas.gfHood Canal(l.B}Vo) wasnearly identical to the aver- tween-population structur€ and gcnc flow. In gcneral, one agediversity among streamswithin each area (1.76%). Over would expecta nonanadromouspopulation rcsiding in a small vJYoot the total gene diversitywas observed within individual creek to be charactcrizedby a relatively small effeitivE pobu- rAcomplete lation size cgmparcd with anadromouspopulationr roong setof tabulardata for alletefrequencies for all loci and which geneflow may occur (secSpie*r ieiC for theorctical Campton.tgSt) f:{::^q is avaitabte.at a no-miiaicharge,from the considerations).Such a populationwould be particularly sensi- rr€postroryot Unpublished Data,CISTI, NationalResearch Council ttve to bonleneckeffects and genetic drift, andwould be under of Canada.Otrawa, Ont. KIA 0S2. a separateregime of naturalselection since smoltification and Can.J. Fish.Aquat. Sci., Vol.44. t9g7 577 tt r{ 8,.o rl i \ -i- :' '- I L,ri. I I o I It +{ l?' '{ I' I i1_. - -t-Ir - - t? \ t? .,1i-l', o.8 , ?' . l,i.I | a i { il (1 ll t.o t I l' 't'l \ i -t---- .o tD , lll tr) l. _'J_'_r_lt i-,_r_._t1 \I ,ili s t s ? s ? _{__. : rfil $ r) l 0.6 t \I a a I I t.o fr -t_ _ r I lt-1+ i. a I o lo ?i-;- I s ? -'+.+{ \ (t tt i q. .l tl {

{+'r? * a l'I a ltrr t I T q ll.lj s .t----. s : |--.tJ--It' o lrtl a 1+, o t+ (r) I I \ lrnt: s I (4 t, I t

I rl

2l I 2l STREAM STREAM Ftc. 2.-{llele frequencydistributions at loci wherethe frequencyof rhe mostcomnxrn allele was less all fish pooled(GPl-/ lli:l:15.1:l excluded,see Fig. 3).'Thc it stroams(poputations) g.upra rnto rour drainageareas (Fig. l). The brokcn horizontallines reprcsenrne corirpirsircatteic "* frciucniies for all fish collectcd from each drainagearca (Table 2), excluding the nonrnadromousHowe Creck population(stream l8) from the averagesfor the northernmoa Cairt drainage(strcams l8-21). Thc vcrtical line for each strcam is the differcnce in allete frequencyvalues bet-wecn thc two year class (agcp+ > samples andage I +). The solid circlesrcprcsentihe ailcle fregucncies for both crasses pooled. vj,11'

saltwateradaptation would not be integrallifc history com_ classes,because of (l) gencticdrift within the poputations ponents.Results for the Howe Creekpopulation thus provide themselvesand (2) cnors associatcdwith the ficld samplingof furtherinsights regardingthe relationsiripbetween lifc'history individuals(Smith 1969).tf gcne flow amongstr€ams was patterns population and structur€sof salmonidfishes. extensive,then spatialgcnetic variation amongsfteams would -The significantvariance components associated with stream be approximatelyequal to the temporal variation amongyear effects in 7 of 12intralocus comparisons suggest that gene flow classeswithin strcamsbecause a largc panmicticpopulaiion is also restricted at this level oi subdivisiJi. This pipuhtion would be randomlysuMivided eachgeneration among a large structuring couldbe reflectingthe hominginstinct of sfawning numberof nibutaries,In this situation,variance components adults. general, In onewould expect allele frequen cy istimatel for streameffects should bc closeto zero. On the othel hand, to fluctuate randomlyover time, and amongionsecutive year if anadromouscutthroat trout home to their natalstrcams with 578 TegLE 3. vadancc componcntestimatg derived from hierarchical ANOVA's of thc arcsinc-transformpd@ucrrcies of the most common allele at eachlocus. Lpci with commonallele frequenciesgrealcr han 0.99 for all fish poolcd (Tabtc 2) wcrc excluded from thesc enalyses.At loci wlrcre vrriance cornponcntestimatbs for drainage cffects werc lessthan zcro, vrriance compo{r€ntsfor rcgion, strcam, and year classcffects werc cstimatcdby rcanalyzingthc data without &ainagesin the nrodel.*P < 0.05: *.P < 0.01; ***P < 0.001.

Variancc componcnt€stimates o Loci Rcgions Drainagcs Strcams Year classes o AAT-1,2 -t.t 0.3 -t.2 17.6 ADH -9.7 19.8r m.7* tE.5 I GLD-I 74.Efi* -7.4 ' r2.E 4t.2 q. rl GPI-I 2.r 0.8 22.4 43.4 o IDH.3,4 -50.6 109.4*rt 2.7 27.0 o.6 l1' TIDH.I,2 21"5*r* -2.5 9.7** 6.5 MDH-3,4 47.1.*r -3.2 10.4*r, 6.8 T,TPI 31.2*r -7.0 21.8* r9.3 PGD t7.5* -8.9 28.l** lE.2 PGM 43.7*. -5. I m.4+ r8.2 SDH.I 42.5' 7.2 xi.4* 37.O soD 73.2,** -5.E 6.4 45.E 'Significant at thc 0.0! lerrctwhcn drainace effects are removed o.4 from thc rnod€l(F = tfd0r.

, ?T graphicallyadjacent strcams by makinga few simpleassump- ,TREAM tionsand applying Wright's ( 1943,195 | ) islandmodel of population structure.According population Flc. 3. Frequencydistribution of theGpl-t (IM) allele. Svmbols are to thii model"a is asdescribed in Fig. 2. subdividedinto a large numberof subpopulations,each of effective sizc lV, and gene flow occurs amongthem at some fractional ratem (secalso Wright | 969, p. 29I Allendorf and a high {!gt"r of precision, then variancecomponents for ; streameffects could be significantlygrcater than ztro because Phelpsl98l). ln the absenceof sclection,a balancebetween eachstream would be supportinga iemi-isolatedpopulation, gene flow and gcnctic drift is expcctedto occur such thst the thu-sallowing allele frequencies to divergeas a rcsultoigcnetic amount of gcnaic dlffercntiation anxrng subpopulationsat : drift and/or natural selection.The magnitudeof t[is di- equilibrium can bc approximated(for small m) by Fsr = = vergencewould dependupon the effectivesizes of the indi_ l/(4Nn * l), whereFsr Wright'sfixation index andNm vidual populations,the amountof geneflow amongthem, and the effectivenumber of migrantspef subpopulationeach gener- the particulareffects of naturalselection. ation. ln this context, our estimatedparameter C5p, which rneasurcsthe amountof geneticdifferentiation arnong strcams . Taggingstudies to determinethe precisenessof the homing instinctin anadromouscutthroat trout have,to our knowtedgel within drainages,is equivalenrro Wright's Fs (Nei 1977; neverbeen performed or reportedin the pubtished Takahataand Nci l98a). By substitutingouravcrage value of literature. = However,tagging studies with othersalmonid fishes have gen- Gso 0.0241(Tabba) into Wright's equilibriumexprcssion crally demonstratedhoming rates between (ball forFsr, we obtaina valueof lVrn* 10.In otherwords, a value 90 and l007o = 1955;Cope 1957; Hartman and Rateigh t964; Stabeil 1984). tn of Gscr 0.0241is consietcntwith a strayingrat€ of approxi- this context,the migrationhabits and homing behavior of ana- mately l0 fish per gcncration(2-3 fish per year) if one as- droqou-sDolly Varden(Salvelinus malma) are especially note- sumesthat ganeticdrift is the pimary sourceof this genetic worthy becausethis speciesexhibits a life history(reviewed by hetcrogeneity. Armstrongand Morrow 1980)very similarto ihat of anadro- Restrictedgene flow is expectedto rduce effective popu- mouscutthroat trout. AnadromousDolly Vardenalso migrate lation sizeswhich in hnn shouldcause a decrcasein average alongshorelines in saltwater, and similaitv return to frcshwater heterozygosities(Soule 1976), However, averlge hetero- gaghf{l to eitherspawn (maturc fish) or overwinter(immature zygosities within populations of coastal cutthroat trout (0.080-0.t29) fish). During their saltwatermigrations, Dolly Vardenenter wereamorg the highcstyet rcportedfor any and leave severalnonnatal strcams and may overwinterin a speciesof salmonidfishes (Utter et al. 1980;Ryman 1983; nonnatalstream without ever spawning. Oespite these apparent Gyllensten1985). Thcsc hercrozygosities were also high for randommovements of nonspiwningfish, ermstrong'(197+; vertebratesin general(Nevo 1978),suggesting relatively large foundno indicationof strayingamong spawning adultjin three effective populationsizes. Thesc hetcrozygositiesmay thus adjacentstudy streams over i 2-yr period. appearto be inconsistentwith the suggestionthat gene flow is restrictedat the str€amlevcl of suMivision. TheoreticalConsiderations The resultsobtained here for ansdrcmouscutthnrat trout can bereconciled in termsof thecomputer simulations of Allendorf We can obtain a roughestimate of the averageamount of and Phelps(tgil) and Altukhov et al. (t984). Thesein- gene flow amongpopulations of cutthroattrout inhabitinggeo- vestigatorshave shown that genetic drift amongsubpopulations Can. J. Fish. Aquat. Sci., Vol. 44, 1987 579 TesLe 4. componenrsofgene diversity(Nei 1973)averaged ovcr 3r loci (Tablel) for regions.(R),,drainages(D), strbams(s), yearcrasses(y), ind the torat(T).'Tt; rerarive gene divenity componentsrnfTge thc proponion of the total gcne iivenity (t/7) betweenrcgions within thetotal (Gnr), bet-weindrainages within rclions (Gon),among strpamswithin drainages(oso), betweenyear classes within strcami(Gv.), andwithin year cfasscs(H7/H), respectively.The analysiswas first perfonnebforeactr region scparatelyand then for both rcgionscombined.

Absolute Relative(x 100)

Region Hr Hn G"t Gon Gso Gv" Ht/Ht North Puget Sound 0.095 0.3r 2.99 l. t4 95.56 Hood Canal 0.r09 r.80 t.76 |.23 95.21 Total 0.101 0.r00 t.u t.0l 2.41 t.t1 %.17

No. Hood Conol

* So- Hood q Conol (o

Fl 9 C) o. @ uort Cr.

No. Pugel

,o.12 -o.o6 PCI (40.2%) Ftc. 4. Principal coordinatesanalysis of coastatcutthroat trout populations bascd on Nci's ( t9Z2)indcx of gencticsimitarity' The Howelreek populationis locatcdin itre norrtrernHood Canal spa, but is nonandromous.All otherpopulations arc Uetieveab be anadromous.

Tlt* Ave_ragegencric l: idcntities (Nei 1972)bcrween populations freguencies,urd avcragehetcrozygositics. The net effect is that of coastalcutthroat tnout. Alt fish collcctc{ from a particularstream rcstrictedgene flow can mainuin the samealleles within most wcre considcrcd to bc from a singtc popiliation. Diagonal and off- subpopulations;but may not be sufficient to homogenizeallele diagonal comparisonsreprcsent winiri- ana Uet*eenirainage aver- frequencicsamong subpopulations, ages,rcspectively. Ocnctic variition is thus preservedin a subdividcdpopulation, rplative to a single pan- mictic populationof cqual sizc, becausc goci l. SkagitRiver 0.997 no allele to-fix- ation.in all subpopulationssimultrneously. 2. StillaguamishRiver 0.996 0.996 By samplingcon- secutive year classa 3. SouthernHood Canal 0.995 0.993 0.997 of anadrornousiutthioat frorneach 4. Northern Hood Canal 0.993 0.994 0.991 0.w7 stream,we haveprobably undercstimarcd the fuc rnagnitudcof 5. Howe Creek 0.98t 0.978 0.988 0.981 any temporal variations wirhin populations (i.e. within streams),but may havcdetectcd the gcneticeffccts of restricted t. genc flow amongthem.

Perspectives can yield significantdifferences in allele freguenciesdespite theprcsence of geneflow. AlthoughFsr attainian equilibrium Many studieshave qxaminedgcnetic variation among ana- value when geneflow is rcstricted,ailele frequencieswithin dromouspopulations of salmonidfishcs. However, few siudies eachsubpopulation will neverthelessfluctuate'randomly over of anadromous.populationshave attempt€dto detect genetic time dueto geneticdrift. The magnitudeof thesefluctuations heterogenertyon a miuogeographicalscale. Two notableex- depe$l inverselyupon the effeitive sizes (tV) of the sub- ceptionsare worth mentioning. Altukhov et al. (1975a,l97jb) populationsand the dmountof geneflow amongthem. The and Parkinson(1984) were both able ro detect significanr strucrure Plpulation may thusappear highly dynamicin terms microspatialgenctic heterogcneity among populations of sock- of allele frequencies for individuat su6popuiations,but thi eye salmon (Oncorhyrchusnerlu) and srcelheadtrc)ut, re- overall structure quite is stablein terms-of FsT,m€an g€n€ spectivcly,by repcatcdlysampling the samepopulations in 580 Can.J. Fish.Aquat. Sci., Vol.44, 1967 differcnt years and/or life hisrorystages and comparingthe F. J. Ayah [cd.] Molcculsr evolurion. Sinaud Associsrcs,Inc., sp.fjialvariation . " amongpopulatiohs to the temporaivari'ation Sundcrland.MA. wrrhtnpopulations. Altukhov et al. foundthat the entircpopu_ Bru-, O. P. 1955.Somc aspectc of homiog in rhc cutthroartrout. Prroc.Utah lation structure Acad.Sci. 32: 75-E0.. of sockeyesalmon within a lake-river r|rtfrn p. was relatively BeAcfleu, T. D.. R,. E. Wm[sR, rto A. Gour.o. l9g5a. Biochemical -stable,iespite the apparentrandom genetic genaic stock idcntification of chum szlmort loncorhvnchus keml in lelerogeqettyobserved within and theindiviOuaipopu- southernBrirish Columbia. Can. J. Fish. Aquat. Sci. 42:437-Mg. lations. Similarly, parkinson found"mb'ng a'ltele frcquency in l9E5b. Biochemicalgcnctic stock identificationof pink salmon (Oncorhlnchas gorbusclul in sourhlm ferences over broad geographicareas to be generaily ' British Columbii and fuget non- Sound.Can. significant despite the appirent significant J. Fish.Aquat. Sci. 42:1474-1483. iifferenies rc BURcNER.R. L. l98l!. Sorncfcaturu of occanmigrrrions and timing pacific detectedamong populations'inhabitin! geographically of adjacent llmnrp. 153-164. InW. t. McNeit ard D. C. HimsJonh[ed.] streams.This genetic structuring- was. easiry ittriuuieo io ttre Salmorid ccoaystcmsof dre Ndth hcific. OregonStrtc Universityircss homing instinctof thesefishes. _ and OrcgonStste Univenity ScaOnnt Collegehogram, Conalii, OR. The results Caurron, D. E. 19il . Gcrrcticirructure of sca-rui cutthroartrout populations andinterpretations of Altukhovet at. (1975b)and (Satnm Parkinson(1984) clarki clar*,il qrlrc Pusct Soundarer. M.S. rhesis,Uiriiersity of . utg ,u"rysimilar to ours: Theseitudies'sug_ Washingon,Scarlc, WA. lg0 p. gest that genetic _ the effecs of homingmay be detectabreif tie Crumon, D. 8., ,tro F. M. UrEi..t9g5. N*ural hybridizarionberwecn investigationsare-designed within a [ypo:nesis+estingframe- stcclhcadtio{rt (sarrtrogairdncril andcosstrl cunhroat tro ut (satmoctarki work to specificallyaddress this queition. In c.tglkil iy two Pupt Soud smams. Can. J. Fish. Aquar. Sci. 42: this coitext, a I t0- I t9. comparativestudy amongall salmonidfishes may reveatsome Cxernraonrr, R., M. HA^o, N. Ryuex, erb G. SrAnu 19g2.Hicrarchical interestingand porcntially usefulcorrclations gerc beiweenthe ge_ _diversiryuralysis iod its application to bmwn trout poprlations. netic infrastructuresof thesespecies and thcir rcspectivel'ife Hcrcdirrs9l:. 17-21- history attributes. CLAyroN,J. W., eno D. N. Tlrnrx. lg2. Aminc-citrate buffer for pH confiol in sterch gel etectrophoreris.J. Fish. Rcs. Board Can. i9: lt69-n72. Acknowledgments CoPE,O. P. 1957.Rrces of cunhmarrorn in ycltowsonc l,ake. p.74-&A. J. t"tl Coryriburiom ro rhc srudyof subpoprtationiof fishcs. We ! 9 Ytg thankJames M. Johnstonand Stewart p. Mcrcerof thc Wash_ !p*:*i.Rcp. Fish..t{o. 2$, U.S. Fishana Witdtifc'Servicc. Washing- ington-stateDepartment of camefor theircxtensive assistancc with ton, DC. / coucctrngsamples of cutthroattrout from thc puget DnWrrr, J. W. Jr. 1954,A survcy of the coastalcutthmar bout. Salmo clarki Soundarea. clarti Richardsor. stewartP. Mercerread the scalesand determined-the ages of thc in Crlifomie. Calif. Fish Gamc 40: 3Zg-335. EvEnnr, B. S. l9E. Grapl$crl tcchniques for multivarirtc data. North subsampledfish. Larry J. McCollumassisred with thei"borato; yo*. preparation _ Holland,Ncw fW. ttZ p. of tissuesfor electrophorcsis.The administrativeassis'- FllsilsrttN, tance l. 1982. Ifow cm wi infcr gcography- ' - and history from genc of RichardR. Whitneyfleider), GitberrB. pauley(assistant freqtrcrrcics?f. ftcor. Biol. lcader),and 96: 9-20I JamcsL. C.onglcion of theWashingron Coop"Lri"" nrf,_ FounMsR,D. A., T. D. Bs^crilM, B. E. RrDDEr,rro C. A. Bus^cK. 19t4. ery RescarchUnit, Univenityof Washington,is greattyapprcciatcd. Estinating stoct conpoeitloo in mixcd fishcrics ucing rnorphometric, The scnioraurhor extcnds his specialn-ants to-trc mcnsoc, aflt cbctrophorttic clrrr*cristics. Can. J. Fish. Aquat. Sci. 4l : Noriri*estano ,()0-,+08. AlaskaFisheries Cenrer, National Marine Fisherie, S","d, i;;tt,;; for providinglaboraory facilities and office spacc. Gren. R. D. lnz. Ecolosr rnd mrmgcmcnt of coastrl cttduoat trcut in This work was Orcgon. Fish. proircr supporrcdby the WashingtonState Departmeni of Game. Ra. Rcp. No. 6, F-?2.R, Orcgor Stsrc Gsrc _ Commission,Corvrilir,'On. Ot p. GowER,t. C. tS6. SorF dirtrrc proicnic of grcnt rmt ard vectorrncthods References _ usilg in mulrivrriae rmlyris- Biolrctrika 52: 325-33g. Gnexr, W. S., G. B. Mn rrn,. p. Kresnowsru,er,ro F. M. Unrn. 19g0.Usc of bioctcmicrl AUENDoRF, pHsLps. gcnctic vrriants for idcntificrtion of sockcye salmon F. W., er,roS. R. t9gl. Useof allelic fiquencies ro (oncorhydw describepopurarion rcrka) srocts in Cook Inlct, Ahska. Can.J. Fiih. equat. ^ stnrcures.can. J. Fish.Aquar. sci. 3E: ri07- rs 14. Sci.37: t236-t247. ALLENmnF, F. W., exo F. population M. UrrER. 1979. g.;i";: GYlrcxsnn, U. 1985.Ttrc gmctic p. e7-454. /z W. st|rtctut! of fish: diffcrcncesin th€ inrra- S. Hoar, D. J. Randail.,na l. il. Srcn taO-i Fish specific distibution physiology.Academic press, york, of bioclemird gancdc varirtion bcrwecnmarinc, New Ny. snadromous,and ftreshwaEr ALTUxlov, Yu.p.. V. A, NArDtcH, epocic. l. nch Biol. 26: 69l-699. elo L. A. ZxlvorcvsKn. t9g4. Computer Hnnruer, G. F., eno modelling of inrcracrion C. A. CIJ-. f96t. Disriburion of juvcnilc stcclhcadand bctwccnrandom genetic drift and genc,ig;rio; cutthroattrout (Sarrilogairdncri in a system parrially a$ S. clat*i clarkii withinrreams within of isolarcdpopulatiolns. Ccnerika ZCi'+1, OOS-_OdS. sorthwcstcrn (Transl. from Eritieh Columbir. t. Fidr. Rcs. BoardCan. 25: 33-4E. Russianby Sov. Genct.20:475_4791 Henruen, W. ALTUxHov, yu.p.,-A. L., ANDR. F. Rrr-ercr. 1964.Tdbur.ry homingof sockeye l. irumvrux, E, A. S^rMENxove,ero S. M. salmonat Koxoverov. Brco*s ard Kduk L.alcs,Alaskr. ,. Fish: Rcs. Bord Can. il: 1975a.Stationary distributions of thc frequencies i*nt" 4E5-504. dchydrogenascand phosphogiucomutasegenes in tti "f ,ys.. oiruU He*en, A. D., ANDA. T. Sct{olz. 19t3. Olfactory imprintingand homing in populstions of a local fish srock of Oncoriynchus nerka Walb. tI. Ran. salmon_.Springcr-Verlag, Barlin, Hcidclbcrg, Gsrmany.-lfC p. dom gcneticdrift, migtrtion, andscrection as facron orrt"uility-. . o.nJii. - JoHNsroN,J. M., ^ND S. p. MBc€R. 196. Sii-run cuttLrsatin saltwatcr ll(4):54-62. (Transl.from Russianby Sov. Gerrcr.f l: AS3_rc|) yu.p., pens: broodstockdcvelopncil and cxcrdcd juvcnile uring (with a life ALruKHov, E. A. SeuraEtxove,S. fr{. KoHoverov, nno A. I. history_compendium).Fish. Rca. Rep. Rroovrn. I975b. distributions noiLct efS.SZ-t,-Wadrington -surionary of thc frequcncie, f".t.rc StareGarnc Ocpumrcm. Olyrnpia. We. gZ-p. dehydrogenasea1d "i g[osphogtucomutascgcncs in i system of sub- JoNE:: I 977.A of stithdad -cunhmat populationsof a local fish P. _E: {udy in ttaska. StudyAFS 42-5, srock of Oncoriyncvhus_r&o Walb. I. St"_ Alasla Depannrcnt bility of a stock over gcnerations , ___Y9 .lE. of Fish rnd Ganr, Jupau, AK. 105 p. with simultancousvariabitiiy of tirc LEGcEfi, W. C. 1977. component subpopulations. Thc ccobgy of fish migr*ionr. Annu. Rcv. Ecol. 3yst. Genetika t l(4): 44_53. (Tranjl. from 8: 2E5-308. Russianby Sov.Gener. ll:441_4541 MATKERT,C. L., rm I. FeuutesEn. t965. l.actate ddrydrcgcnaccisozyrnc ARMsrnoNc,R. H. 1924.Migration of anadromous (Salvclinus Dolty Varden pancrnsof fish. J. F-xp.Tnl. lS9: 319-332. nalnm\ in southeasternAlaska. J. Fish.Res. BoardCan. llillS_g. Mrv_,.B., J. E. Wnrcm, eno M. ARMSTRoNG,R. H., mro J. E. Monnow. Slor,rxnro. t9?9. Joint scgrcgationof 19g0.The Dolly Vardenchan, biochemicalloci in salmqridac: ' Salvetinusmalma, p. 99- rcsultsfrom erperirncntswidr salvaldanr t40. In E. K. nafon [ea.]tfrarn, iifr"i"i and rcview of the gcnus thc litennrrc on othcr spcics. J. Fish. Rcs. BoardCan. 36: $hc-s_of Salvclinus.Dr. W. Junk Uv puUtistrers.Tlr; H&;;, 1il4- The Nethcrlands. il28. MICHAEL'J. H. Jn. 19E3.contribution of cutd'oat trout in headwatcrstreams Avrse.J. C. 1975.Genetic differenriation during speciation. p. 106- 122.In to the sea-runpopulation. Celif. FishGamc 69: 6g*76. Can.J. Fish.Aguat. Sci., Vol.44, t9g7 581 F

'. !! tlEl M. 1972. Genericdisrance berween popularions. Am. Nar. 106: SMrH. C. A. B. 1969.Local fluctuationsin genefrequencies. Ann. Hum. 283-292. Genet.32: 251-260. (EnataAnn. Hum. Genet.N:2641 1973.Analysis of genediversity in suMividedpopulations. Proc. SoKAL.R. R.. exo F. J. Rosur. 19(i9.Biomctry. W. H. Freemanand Com- . Natl. Acad.Sci. USA 70:3321-3323. pany,San Francisco. CA.176 p. 1977.F-statisrics and analysis of genediversiry in subdividedpopu- SouE. M. 1976.Allozyrrc variation:its determinantsin spaceand time. lations:Ann. Hum.Genet. 4l:225-233. p. ffi-77.In F. J. Ayala[od.] Molecular evolution. Sinauer Associates. NH, M., rxo A. K. Rovcxououuny.1974. Sampling variances of hetem- Inc.. Sunderland.MA. zygosityand genericdistance. Genetics 76:379-390. Snenr, P. T. 1974, Genc flow and genoic differentiation.Genetics 7E: NEvo, E. 1978.Genetic variarion in naruralpopulations: patrcrns and theory. 96t-%5. Theor.Popul. Biol. 13: l2l-177. Srmru-, O. B. 1984.Homing and olfaction in salmonids:a critical review Nrr-ssor,r,N.-A., ero T. G. NonrHcore. l9El. Rainbow trout (Sa/mo with spccialrcf.rencc to the Atlmtic salmon. Biol. Rev. Cambridge gairdneriland cunhmartrcur (S. c/arti) interactionsin coastalBritish Philos.Soc. 59: 333-3EE. Columbialakes. Can. J. Fish.Aquar. Sci. 38: t228-1246. TrxrHetr. N.. eno M. Net. 1984.Fsr and Csr statisticsin the finire island OKAzAK,,T.l9E3a. Distribution and seasonal abundance of Salmogairdneri model.(lrtter to thc editor.)Genctics 107: 501-504. and Salmo nytr'ss in the north Pacific Ocean.Jpn. I. lchthyol. 30: Tronsor, R. M. 1980.Ict-slrcct glaciation of the Pugetlowlond. Washington, 235-246. duringthe Vashon*ate (latc Pleistocenc).Quar. Rcs. l3l 303-321. t9t3b. Genetic structurcof chum salmonOncorhynchus keta nver Urrrn, F. M.. D, Ceupron, S. Gnerr, G. MLxrn, J. SesB,rNp L. WrsHero. populations.Bull. Jpn.Soc. Sci. Fish.49: 189-196. 1980.Fopulation structures of irdiginors sdmonid spcciesof the Pacific . PARKINSoN,E. A. 1984.Genetic variation in populrtionsof stcclheadtrout Northwest,p. 285-304. la W. J. McNeil and D. C. Himsworth[cd.] (Salmogoirdneri) in British Columbia.Can. J. Fish. Aquat. Sci.4l: Salnrcnidccosystcms of thc North Prcific. OregonStrte Universityhess l4t2-t420. and OregonState Univenity ScaGnnt Collcge hogrrm, Corvallis, OR. RrcKER,W. E. 1975.Computation and inrerprctation of biologicalsratistics of Wlu.trMs, R. W.. R, M. [aR^MrE.AND J, J. AMES.1975. A caralogof fish populations.Bull. Fish. Rcs.Board Can. l9t: 382 p. Washingtonstrrsms and salmonutilization: Vol. l, PugetSound region. Rrocwry, G. J., S. W. Snenrunxe.ero R. D. Lewrs. 1970.Polymorphism WashingtonStatc Dcpanmqt of Fisherics.Olympia, WA. in tlr€estcrascs of Atlantichening. Trans. Am. Fish.Soc. 99: 147- l5l. WrLMor,R. L.. rnp C. V. Bunaen.19E5. Gcneric differcnccs among popu- Rvuer, N. 19E3.Patterns of disrributionof biochemicalgcrrcric variation in lationsof Alaskansockcye Salmon. Trrns. Am. Fish. Soc. l l 4: 236- 243. salmonids:differences betwecn specics. Aquaculturc 33: l-21. Wrrclrr. S. 1943.lsolation by disrancc.Gcnetics 2E: I 14- t3E. Ryuex, N., F. W. ALLENmRF.eno G. SrAru. 1979.Reproductive isolation 1951. The gcncticalstructur€ of populations;Ann. Eugen. 15: with linle genetic divergenccin symparricpopulatiohs of brown trout 323-354. I (Salmo trutul. Genetics92: 247-262. 1969.Evolution 3nd thc grnctics of populations:Vol. 2. The thcory Scsm, W. 8., exo E. J. Cnossurr. 1973.Frcshwater fishes of Canada.Bull. of gene fregucncics. The University of Chicago Prcss, Chicago. lL. Fish. Res.Board Can. 184:966 p. 5l I p. SHlw, C. R.. mro R. Pmslo. 1970.Starch gcl electrophorcsisof enzynr€s- Wvoosrr. R. S.. rro R. R. Wumlry. 1979.Inland fishesof Washineton. a compilationof recipes.Biochem. Gencr. 4: 297-320. Universityof Washingtonkress. Seattle, WA. 220 p,

582 Can.J. Fish.Aquat. Sci., Vol.44,.1987