This article was downloaded by: [Michigan State University]On: 07 February 2014, At: 06:02Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Transactions of the AmericanFisheries SocietyPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/utaf20

Effects of Stocking on Genetics ofWild Brook Trout PopulationsCharles C. Krueger a & Bruce W. Menzel aa Department of Animal Ecology , Iowa State University ,Ames , Iowa , 50011 , USAPublished online: 09 Jan 2011.

To cite this article: Charles C. Krueger & Bruce W. Menzel (1979) Effects of Stocking onGenetics of Wild Brook Trout Populations, Transactions of the American Fisheries Society, 108:3,277-287, DOI: 10.1577/1548-8659(1979)108<277:EOSOGO>2.0.CO;2

To link to this article: http://dx.doi.org/10.1577/1548-8659(1979)108<277:EOSOGO>2.0.CO;2

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoeveras to the accuracy, completeness, or suitability for any purpose of the Content. Anyopinions and views expressed in this publication are the opinions and views of theauthors, and are not the views of or endorsed by Taylor & Francis. The accuracyof the Content should not be relied upon and should be independently verifiedwith primary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connectionwith, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms& Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Trartsox'tio•s of the American Fisheries Society 108:277-287, 1979 Copyright by the American Fisheries Society 1979

Effects of Stocking on Genetics of Wild Brook Trout Populations

CHARLES C. KRUEGER 2 AND BRUCE W. MENZEL

Department of Animal Ecology Iowa State University Ames, Iowa 50011

Abstract

The study was undertaken to evaluate the long-term genetic impact of maintenance stocking upon wild brook trout (Salvelinusfontinalis) populations in Wisconsin. Trout were collected from streams of the Wolf and Fox River drainages and from the Osceola State Trout Hatchery. The stocking histories of the streams ranged from unstocked to heavily stocked for many years. The planted fish consisted primarily of fingerling and catchable brook and brown trout (Salmo trutta). Blood plasma and whole-eye homogenate samples were analyzed electrophoretically for trans- ferrin (Tf) and lactate dehydrogenase (Ldh-B2) systems. Esterase was monomorphic in all sam- ples, but Tf and LDH displayed genetic polymorphism. The occurrence of several Tf A/A phenotypes among wild fish is notable because previous genetic studies considered the combi- nation to be lethal. The hatchery stock was genetically distinct from most wild populations at both loci. Variation of Tf allelic frequencies among wild populations suggested an undisturbed natural geographic pattern. There were significant correlations between Ldh-B2 allelic frequen- cies and stream stocking histories, however, with the wild type allele decreasing in importance as stocking intensity increased. This relationship does not seem to reflect interbreeding between wild and hatchery trout. Rather, it may indicate alteration of selective pressures induced by ecological interactions between the two stocks.

Evaluations of maintenance trout stocking programs have typically focused on survival and harvest of the stocked fish with little atten-

tion directed toward impacts on the native pop- ulations. Several recent studies suggest, how- ever, that wild stream trout populations may be adversely affected by..stocking through in- creased angling pressures (Butler and Borge- son 1965), competitk)n with domesticated fish (Thuemler 1975; Vincent 1975), or by other behavioral interactions between the two stocks

(Butler 1975). Various authors have speculated that native gene pools may be altered through interbreeding of wild and hatchery fish (Smith and Needham 1942; Miller 1957; Calaprice 1969). Although examples of genetic swamping through interspecific hybridization are •vell known among salmonids (Miller 1961), stan- dard morphological analysis has generally

•Journal Paper number J-8947 of the Iowa Agri- culture and Home Economics Experiment Station, Ames, Iowa. Project number 2075.

• Present address: 219 Hodson Hall, 1980 Folwell Avenue, Department of Entomology, Fisheries and Wildlife, University of Minnesota, St. Paul, Minnesota 55108.

proven inadequate to evaluate genetic interac- tions at the intraspecific level. Biochemical evi- dence of possible genetic exchange between •'ild and hatchery stocks has been presented by M•ller (1970) for Atlantic salmon (Salmo salar) and by Eckroat (1971, 1973) for brook trout (Salvelinusfontinalis), but in both situations the data were generated only incidentally and lacked support of stocking information.

In this paper we compare wild and domes- ticated stocks of Wisconsin brook trout at sev-

eral genetic loci as determined by electropho- resis of blood and whole-eye proteins. The study was designed to provide information on (1) levels of genetic variability in the two stocks; (2) spatial relationships of breeding units among wild populations; and (3) genetic im- pact, if any, of stocking upon the native brook trout.

The brook trout is the only indigenous stream salmonid in Wisconsin; however, brown trout (Salmo trutta) and rainbow trout (Salmo gairdneri), as well as brook trout, have been stocked in the state's inland waters since the late

1800's. Until 1919, state hatchery facilities per- mitted the production of only eggs and fry. When hatcheries with rearing facilities were

277

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

278 KRUEGER ^•D MEnZeL

0 20 40 km I I I I I

FiCvR• 1 .•ollecting sites. Little Wolf River drainage: Jackson Creek (J); Spaulding Creek (Sp); Blake Creek (Bl); Trout Creek (T); Sannes Creek (Sa); Stenson Creek (so; Basteen Creek (Ba). Waupaca River drainage: Al- len Creek (A). Fox River drainage: Lawrence Creek (L).

constructed in the 1920's, emphasis shifted to the stocking of fingerlings. Throughout this early period, actual planting of hatchery prod- ucts was performed by sportsmen's groups who requested fish for their local areas. In 1935, the state conservation department assumed re- sponsibility for supervising planting operations, and first efforts were made to stock larger fish. During the 1940's, production of catchable fish was gradually increased, but stocking of finger- lings continued to be emphasized. In 1954, a new state trout management policy was adopt- ed which minimized the role of maintenance

stocking while emphasizing habitat improve- ment and propagation of legal-size fish. The present stocking program primarily involves planting of catchable fish in waters where an- gling pressure is heavy and natural reproduc- tion is insufficient to sustain the fishery. Fin- gerlings continue to be stocked in other lower quality streams that receive less fishing pres- sure. High quality trout waters that produce adequate natural populations have been only infrequently stocked since the mid-1950's.

The domestic strain of brook trout used in

Wisconsin during recent years is derived from the Osceola State Trout Hatchery, Osceola, Wisconsin. Originally a commercial operation, the hatchery with its brood stock was leased by the state in 1925 and later purchased. The or- igin of the strain is unknown, but under state management it has undergone selection for body form and coloration, and rapid growth. It is possible that the strain has also been ge• netically modified by introduction of wild fish from Montana and Canada during the early period of state operation (Wisconsin State Con- servation Commission 1930).

Methods

Three hundred fifty-four brook trout were collected in July 1975 by electrofishing from nine streams of the Fox and Wolf River drain-

ages. Fifty-one specimens were obtained at the Osceola State Trout Hatchery. Eight of the field populations were from the Wolf River sys- tem in Waupaca County; the ninth was from Lawrence Creek, Adams and Marquette Coun- ties (Fig. 1). To assure that the stream trout were not from recent hatchery plantings, only fish below the minimum size stocked were tak-

en. All streams were sampled at a single locality with the exception of Trout Creek, which was sampled at three sites approximately 2 km apart. These collections were made in the lower (Trout I), middle (Trout II), and upper (Trout III) sections of the stream. Selection of streams was based on stocking records provided by the Wisconsin Department of Natural Resources. The available records spanned a 39-year peri- od, from 1937 to 1975. The relative degree of stocking intensity in the streams during this period was expressed by a ranking procedure. Each stream was initially ranked from 1 (lowest) to 9 (highest) for two measures of stocking: fin- gerlings/stream length, and catchables/stream length. Overall stocking ranks were then deter- mined from the sums of the two initial ranks of

each stream (Table 1). After collection, wild fish were transported

alive to a laboratory at Hartman Creek State Park, Waupaca County, for preliminary pro- cessing. The Osceola hatchery fish were pro- cessed directly after collection. Blood samples were obtained from anesthetized fish by direct cardiac pux•cture with heparinized capillary tubes. Immediate centrifugation of the samples separated the cellular constitutents from the

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

GENETIC IMPLICATIONS OF BROOK TROUT STOCKING 279

.--Stocking histories of the study streams.

Numbers of Numbers of

Stream Years of Year last fingerlings catchables Stocking length (km) stocking stocked per km per km rank a

Wolf River drainage Jackson Creek 7.6 13 1954 4,529 b 1,417 b 4 Spaulding Creek 12.3 33 1974 6,390 b 1,931 b 7.5 Blake Creek 8.1 35 1975 4,735 TM 6,238 •'c 9 Trout C reek 7.7 12 1954 3,169 •'c 1,152 c 3 Sannes Creek 3.5 29 1975 1,429 •'c 3,397 •'e 5 Stenson Creek 5.5 6 1951 1,255 b 0 2 Basteen Creek 1.3 8 1951 28,722 •'½ 592 c 6

Waupaca River drainage Allen Creek 1.9 0 0 0 1

Fox River drainage Lawrence Creek 4.4 8 1948 16,669 •'e 1,650 •'e 7.5

Increasing order of stocking intensity. Brook trout.

Predominantly brown trout; limited rainbow trout stocking in some streams.

plasma. Blood samples and whole trout were stored at -20 C until prepared for electropho- resis.

Blood protein constituents were separated by the method of horizontal acrylamide gel elec- trophoresis described by Balsano and Rasch (1974). Details of the technique and staining procedures for plasma esterase and transferrin (Tf) are given by Menzel (1976). Lactate de- hydrogenase (LDH) phenotypes were deter- mined by horizontal starch gel electrophoresis of whole-eye homogenates. Immediately before electrophoresis, partly thawed eyes were placed in 10 x 75-mm glass tubes with 0.5 ml distilled water and homogenized by a motor powered Teflon pestle. Throughout the sample prepa- ration process, the eye homogenates were cooled on crushed ice baths. Starch gels (13%) were prepared as described by Smithies (1955). A tris-boric acid-EDTA (ethylene diaminetetra- cetate) buffer was used for both the gel and electrode chambers (Markert and Faulhaber 1965). Up to 20 samples were applied to each gel with 4 x 6-mm filter paper applicators. Electrophoresis was for 18 hours at 350 volts and 20-25 milliamperes. During protein sepa- ration, the gels were cooled in a refrigerator at 4 C. LDH staining followed the procedures of Morrison and Wright (1966). The nomencla- tural system of Hoffman (1966) is used for phe- notypic and allelic designations at the Tf locus. Various nomenclatural arrangements have been applied to the LDH systems of salmonids.

•'right et al. (1975) suggested a unifying scheme which we follow here. Our literature

citations, therefore, do not necessarily use the original gene and gene product designations but do refer to genetic homologs.

Tests for statistical homogeneity between sets of phenotypic frequencies at the Tf and Ldh- B2 loci utilized chi-square in contingency tables (Snedecor and Cochran 1967:250). For each lo- cus, a EuclidJan distance matrix for all popu- lation samples was calculated from the matrix of chi-square values. Statistically homogeneous population groups were then identified by clus- ter analysis, by the unweighted pair group method of McCannon and Wenniger (1970). Correlation of stocking histories with Ldh-B2 alleles was determined by Spearman's rank cor- relation coefficient (Steel and Torrie 1960:409).

Results

Stocking Histories

The study streams presented a variety of stocking histories (Table 1). Except for un- stocked Allen Creek, all had received plantings of brook trout, the bulk of which were finger- lings stocked in earlier years. The brook trout stocked in Stenson, Basteen, and Trout Creeks

were all fingerlings. Five streams received plantings of fingerling brown trout, rainbow trout, or both. Catchable trout were planted in all streams except Allen and Stenson Creeks. In Basteen, Trout, and Blake Creeks, the catch-

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

280 KRUEGER AND MENZEL

TABLE 2.--Tf and Ldh-B2 allelic frequencies among brook trout with Hardy-Weinberg equilibrium probability values.

Tf Ldh-B2

Allelic frequency Allelic frequency P of a P of a Sample

Sample larger X 2 A B C larger X 2 B2" Bz' B• size

Jackson Creek >0.75 0.12 0.21 0.66 >0.48 0.07 0.23 0.70 40 Spaulding Creek >0.75 0.20 0.21 0.59 >0.80 0.07 0.27 0.66 35 Blake Creek >0.25 0.12 0.37 0.51 >0.07 0.07 0.48 0.46 38 Trout I Creek >0.50 0.12 0.21 0.67 >0.75 0.02 0.21 0.78 29 Trout II Creek >0.90 0.21 0.10 0.69 >0.06 0.05 0.04 0.91 29 Trout III Creek >0.50 0.14 0.18 0.68 >0.45 0.07 0.05 0.87 28 Sannes Creek >0.30 0.23 0.18 0.60 >0.10 0.00 0.16 0.84 31 Stenson Creek >0.40 0.08 0.74 0.18 >0.75 0.25 0.01 0.74 36 Basteen Creek >0.20 0.21 0.46 0.33 >0.02 0.07 0.24 0.69 35 Allen Creek >0.99 0.00 0.00 1.00 >0.99 0.00 0.00 1.00 20 Lawrence Creek >0.05 0.03 0.44 0.53 >0.30 0.06 0.33 0.61 33

Osceola Hatchery >0.44 0.00 0.67 0.33 >0.99 0.00 0.27 0.73 51

able fish were predominantly or exclusively brown trout, while in the remaining streams most or all catchables were brook trout. A more

detailed account of the stocking histories is giv- en by Krueger (1976, Table 1). Our procedure of determining overall stocking rank among these streams considered fingerling and catch- able stocking rates as separate components of equal weight. The procedure did not distin- guish between the several species stocked. Ac- cording to this system, unstocked Allen Creek was assigned the lowest overall rank (1), while Blake Creek was considered the most heavily stocked stream (9). Spaulding and Lawrence Creeks were of equivalent rank, and so were assigned the mean rank of 7.5 (Table 1).

Electrophoretic Patterns

Plasma esterase appeared as a single band in all trout electropherograms examined, a result which is consistent with previous studies by Ny- man (1967, 1972). Transferrin and lactate de- hydrogenase, however, were genetically vari- able.

Six Tf banding patterns, identical to those described for Pennsylvania populations (Hershberger 1970), were observed among Wisconsin trout. Hoffman (1966) demonstrat- ed through breeding experiments that these patterns are controlled by three alleles (A, B, C) at an autosomal locus. In all population sam- ples, there was satisfactory statistical agreement (P > 0.05) of observed Tf alleleic frequencies with Hardy-Weinberg expectations (Table 2).

Lactate dehydrogenase banding patterns representing the B- and C-type isozymes were

produced from eye homogenates. There was no phenotypic variation attributable to the Ldh-C locus, but six distinctive patterns were identified among B-type isozymes. These pat- terns are interpreted as representing the prod- ucts of three alleles at the Ldh-B2 locus, as pre- viously shown for Pennsylvania brook trout by Wright and Atherton (1970). The appropriate allelic designations are B2, Bz', and Bz". Mor- rison (1970) and Wright and Atherton (1970) reported allelic variants at the Ldh-Bx locus but our samples were monomorphic for this gene.

At the 0.05 level of statistical significance, only one Wisconsin population sample (Basteen Creek) deviated from Ldh-Bz allelic frequencies predicted according to Hardy-Weinberg equi- librium (Table 2). This was due to an excess of B•B2' heterozygotes.

Comparison of Hatchery and Field Collections

The Osceola hatchery stock exhibited re- duced genic variability at both loci in compar- ison with most wild populations (Table 2). Among wild and cultured fish alike, the pre- dominant form of Ldh-Bz was the Bz allele.

The Bz" allele was rare or lacking in most wild populations and was absent among hatchery fish. At the Tf locus, Tf c typically predominat- ed among wild trout, but Tf • was most common among Stenson and Basteen Creek fish and among the hatchery stock. Tf A was generally the least common allele among wild fish and was absent among Osceola brook trout. Allelic fixation of LDH-B• and Tf c occurred among the unstocked wild population of Allen Creek.

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

GENETIC IMPLICATIONS OF BROOK TROUT STOCKING 281

T^BLE 3.--Probability levels for chi-square tests of homogeneity at the Tf (above) and LDH (below) loci among brook trout samples from several streams. Double and single asterisks indicate statistically significant differences at the 0.01 and 0.05 probability levels, respectively.

Trout

Sten- Bas- Trout II and Jack- Law- Spaul- Allen son teen ! III son rence ding Sannes Blake

Stenson --

Basteen -- --

Trout I -- --

Trout II and III >0.20 **

Jackson ** **

Spaulding --

Sannes -- --

Blake --

Osceola Hatchery ** **

** >0.60

** >0.75 >0.50

>0.45 >0.30 **

>0.40 >0.10 ** >0.50

* >0.50 >0.70 >0.70 *

>0.10 >0.45 ** >0.75 >0.50

* >0.50 >0.75 >0.50 ** >0.50

** >0.50 * * ** *

* >0.10 * >0.10 >0.25 >0.35

** * ** ** >0.05 *

** >0.40 ** * * * >0.13 **

Within- and Between-Stream

Genetic Variation

The three samples from Trout Creek were statistically similar for Tf phenotypic frequen- cies (X: = 5.8; P = 0.67; df = 8) but were sig- nificantly heterogeneous for Ldh-B: (X a = 15.5; P = 0.08; df = 8). Partitioning of the chi- square value for Ldh-Ba demonstrated that Trout I fish chiefly contributed to this hetero- geneity, while Trout II and Trout III fish formed a statistically homogeneous subset (X: = 3.0; P = 0.41; df = 3). On the basis of this evi- dence, Trout II and Trout III fish were sub-

sequently treated as a subpopulation distinct from those of Trout I.

Chi-square levels of significance for compar- isons of phenotypic frequencies between stream collections are shown in Table 3. Zygotic pro- portions among the Osceola sample were sig- nificantly different (X •, P < 0.05) from all stream samples at both loci, with the exception of the Trout I and Sannes Creek samples for Ldh-Bv Among the 45 possible paired corn-

parisohs of stream collections, there was evi- dence for statistical homogeneity (X 2, P > 0.05) among 14 pairs at the Tf locus and among 12 pairs at the Ldh-Bg locus. Only five combina- tions were statistically homogeneous at both loci: Trout I versus Jackson; Trout I versus Sannes; Trout I versus Spaulding; Jackson ver- sus Spaulding; and Lawrence versus Blake. The Allen and Stenson Creek populations were the most genetically distinctive groups by this anal- ysis, owing to allelic fixation in the former and the unusually high frequencies of Tf B and LDH B2" in the latter.

Genetic Distances Between Populations Cluster analysis of the chi-square values ob-

tained from the paired comparisons just cited provided a useful method of identifying genet- ically similar stream population groups. At the Tf locus, this procedure produced a statistically homogeneous group consisting of the Blake, Jackson, Sannes, Spaulding, Trout I, and Trout II and III populations (P = 0.40, Table 4). The

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

282 KRUEGER AND MENZEL

T^BLE 4.--Stream population groups of brook trout determined by cluster analysis.

Locus Population )•z df P

Primary groups (X •, P > 0.25) Tf Blake, Jackson,

Sannes, Spaulding, Trout I, Trout II and III 26.3

Ldh-B• Basteen, Jackson, Lawrence, Spaulding 7.3

Ldh-B2 Sannes, Trout I 1.2

Ldh-B2 Allen, Trout II and III 4.5

Secondary groups ()•, P > 0.05) Ldh-Bz Basteen, Jackson,

Lawrence, Sannes, Spaulding, Trout I

25 0.40

12 0.82

3 0.75

3 0.22

28.7 20 0.10

addition of any other sample to this group re- duced the level of probability below 0.05.

In contrast to the single genetic subset iden- tified for Tf, three primary population groups were produced by cluster analysis of Ldh-B2 data (Table 4). Basteen, Jackson, Lawrence, and Spaulding Creek brook trout formed the largest homogeneous group. The Trout I and Sannes Creek collections formed another sub-

set. The third group consisted of the Trout II and III and Allen Creek populations. The for- ruer two primary groups also combined to pro- duce a secondary homogeneous cluster. The addition of any other stream population to this secondary group greatly reduced chi-square homogeneity (P •< 0.005).

The patterns of genic variation revealed by cluster analysis are, therefore, not consistent between the two loci examined. On the one

hand, there is a clear geographical basis for the clustering of populations at the Tf locus. All members of the single statistically homoge- neous cluster are populations of the Little Wolf River system which possess the dominant allele, Tf c, at frequencies of approximatley 0.5 to 0.7. Two other populations of that drainage, from the Stenson-Basteen Creek subdrainage, are genetically similar for Tf but differ froin neigh- boring populations by unusually high frequen- cies of Tf B. On the other hand, there are no strong geographical correlations among the three primary population clusters produced for the Ldh-B• locus. Moreover, we cannot attrib- ute Ldh-B• clustering to any simple pattern of environmental variation. Several lines of evi-

dence suggest, however, that a correlation ex-

ists between stocking histories and Ldh-B• vari- ation. The secondary statistically homogeneous cluster, for example, represents streams of sim- ilar stocking histories (ranks 3-7.5 in Table 1). In contrast, the three populations at the ex- tremes of the stocking rankings (Allen, Stenson, and Blake Creeks) are individually distinctive at the Ldh-Bz locus.

In Trout Creek at least two distinct subpop- ulations exist within a 2-kin stream section.

There is no observable barrier to trout move-

ment between these sections. In terms of the

Ldh-Bz allelic balance, the downstream subpop- ulation (Trout I) is similar to populations else- where in the study area which have had histo- ries of moderate to heavy stocking, while the upstream subpopulation (Trout II and III) re- sembles populations of the least stocked streams. There are several road crossings on Trout Creek, each of which may have served as a stocking site in the past. Our stocking in- formation does not reveal which sites were ac-

tually used. It may be speculated, however, that the Trout I locality received the heaviest stock- ing because there the stream is crossed by a paved highway and is within several kin of the nearest community in the region. The up- stream sites are in isolated areas served only by an unimproved road which may become sea- sonally impassable, especially during the early spring, at which time most stocking operations are conducted.

Finally, we have examined the independent patterns of variation of the several Ldh-B• al- leles with reference to stream stocking histories. The dominant allele among Wisconsin trout,

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

GENETIC IMPLICATIONS OF BROOK TROUT STOCKING 283

B2, is presumed to be equivalent to the domi- nant "wild type" allele among stream and hatchery populations of the eastern United States studied by Eckroat (1973), and Wright and Atherton (1970). Among our study popu- lations, this allde tended to occur at highest frequencies among the least stocked popula- tions and at lowest frequencies among those most heavily stocked. This relationship is shown in Table 5, as analyzed by Spearman's rank cor- relation procedure. For purposes of this anal- ysis only, we treated the Trout Creek samples as a single population, using the mean allelic frequency of Trout I and Trout II and III. This was necessary because of our inability to assign separate stocking ranks to the two sec- tions of Trout Creek. The inverse relationship noted between stocking intensity and frequency of the B2 allde was highly significant. Converse- ly, there was a direct and highly significant cor- relation between stocking rank and rank for an alternative allde, B•'. There was no consistent pattern of variation for the third allde, B•", which typically occurred at low frequencies and was common only among Stenson Creek trout.

Discussion

Genetic Variability in Wild and Hatchery Stocks

Allelic balancs at the Tf and Ldh-Bz loci of Wisconsin brook trout are similar to those of

wild and hatchery stocks of the eastern United States. On the basis of its dominance among most wild populations, Wright and Atherton (1970) regarded Tf c as the wild type transfer- rin. This allde tends to predominate among hatchery stocks as well but is less common in the Osceola strain and in the Port Arthur, On- tario, strain studied by Wright and Atherton. In general, native Wisconsin brook trout pos- sess Tf B in higher frequencies than their east- ern congeners. Additionally, Tf ̂ , which exists commonly (frequency > 0.1) in most Wisconsin stream populations, is absent or extremely rare in populations examined by Wright and Ath- erton. It is possible that Tf ̂ of Wisconsin trout is not identical with that of eastern populations, however, because Hoffman (1966) and Hersh- berger (1970) reported that the Tf ̂ /^ genotype is essentially lethal among Pennsylvania hatch- ery strains.

Variability at the Ldh-Bz locus is triallelic among most Wisconsin stream populations, the

TABLE 5.--Rank correlation analysis of stream stocking histories and Ldh-B• allelic variation among brook trout populations. rs = Spearman rank correlation coefficient.

Stream or Stocking statistic rank B• rank B2' rank

Allen Creek 1 (low) 9 (high) 1 (low) Stenson Creek 2 6 2 Trout Creek 3 7.5 3

Jackson Creek 4 5 5 Sannes Creek 5 7.5 4 Basteen Creek 6 4 6

Spaulding Creek 7.5 3 7 Lawrence Creek 7.5 2 8

Blake Creek 9 (high) 1 (low) 9 (high)

r s -0.90 0.98 t 7.53 17.87 df 7 7

P <'0.01 <0.01

B• allele predominating in all but Blake Creek brook trout. A like condition prevails among wild eastern populations, except that B2 is of even greater importance, typically occurring at frequencies of 0.9 and above. In eastern hatch- ry stocks, however, B•' and Bz" are more sig- nificant, especially the former (Wright and Ath- erton 1970).

Among the Wisconsin brook trout, the Allen Creek population is unusual for its condition of allelic fixation at both loci. Allen Creek is a

small unstocked stream that supports only a sparse brook trout population. Reduced genie variability among the population may be due to natural inbreeding and (or) genetic drift. Sim- ilar situations exist in small Appalachian pop- ulations isolated by acid mine drainage (Wright and Atherton 1970; Eckroat 1971, 1973). In each instance, fixation is for the alldes domi; nant among neighboring populations. Aside from such examples, genic variability at these loci seems to be greater among native Wiscon- sin brook trout than among eastern popula- tions. Heterozygote frequency among seven populations studied by Wright and Atherton averaged 24% and 9% at the Tf and Ldh-B2 loci, respectively. Among Wisconsin popula- tions, the corresponding heterozygote propor- tions are two- to four-fold greater at 49% and 38%.

Spatial Relationships of Wild Breeding Units

Most samples of wild populations were ge- netically differentiable at one or both polymor-

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

284 KRUEGER AND MENZEL

phic loci (Table 3). Moreover, the samples from two upstream localities in Trout Creek (II and III) differed significantly from a downstream collection (I) for Ldh-B2 allelic frequencies al- though not for Tf frequencies. This is evidence for existence of at least two subpopulations in Trout Creek. These results are similar to find-

ings by Wright and Atherton (1970) and Eck- roar (1971) for wild brook trout populations in Pennsylvania. In Marsh Creek, Pennsylvania, genetic differences occurred between samples taken approximately 730 m apart but not among samples separated by 274 m or less (Eckroat 1971). The Trout Creek collections were spaced at intervals of approximately 2 kin.

Although brook trout in streams may under- take seasonal migrations, several studies have demonstrated strong year-to-year allegiance to summer residence areas. All overwinter recov-

eries by Shetter (1937) of tagged brook trout in the Au Sable River, Michigan, were within 1.6 km of the site of tagging the previous year. Additionally, most breeding fish recaptured during late autumn had moved only short dis- tances (1.3 km or less) from their summer home ranges. Stefanich (1952) reported that, over a 1-year sampling period, tagged brook trout in a Montana stream were almost invariably re- covered within the same 0.2-km stream section

in which they were marked. Hunt and Brynild- son (1964) and Hunt (1965) reported on move- ments of brook trout over a 9-year period in Lawrence Creek, Wisconsin, one of the study streams in the present research. Among four approximately equal stream sections averaging 1.3 km in length, most recaptures were of brook trout marked in the same section. Move-

ment between sections was primarily down- stream by fingerlings and upstream by adults. On the basis of a 13-year trapping study in an Adirondack stream, Flick and Webster (1975) noted that most brook trout were relatively sed- entary, although a small percentage moved considerable distances (6.6 km).

Results of both tagging and genetic studies thus imply that geographical subpopulations of brook trout exist between and even within

streams owing to limited movement and a strong homing tendency among adults. If hom- ing to natal areas actually occurs at breeding time, within-stream subpopulation segregation may be possible regardless of juvenile dispersal or travel of•aduits at other times. Brook trout

populations may, therefore, be managed on at least a stream to stream basis where desirable

and feasible. Management units may even be extended to sections within streams.

Genetic Impact of Stocking on Wild Populations

It is probable that much of the genic vari- ability observed among native Wisconsin trout is natural. Strongest evidence for this argument exists at the Tf locus which supports a relatively consistent allelic balance among most popula- tions. We have theorized that such a pattern may be expected among geographically associ- ated populations recently derived from a com- mon ancestral stock. Although populations in the Stenson-Basteen Creek subdrainage exhibit Tf allelic balances divergent from those of other Little Wolf River populations, they are similar to each other. It seems likely that this condition reflects founding error during colo- nization of the subdrainage. Further evidence for a natural pattern of high genic variability among Wisconsin trout is the widespread oc- currence of the two least common alleles, Tf A and LDH B2", neither of which is evident in the Osceola sample.

Nevertheless, it is difficult to ascribe all vari-

ability at the Ldh-B= locus to natural circum- stances. In particular, the pattern of variation for the B= and B=' alleles seems to reflect more strongly the stocking histories of the streams than their geographical relationships. Eckroat (1971, 1973) attributed increased genic diver- sity in a stream sample of Pennsylvania brook trout to inclusion of hatchery fish stocked by sportsmen. There is little possibility that our samples were contaminated by recently stocked fish, however. Only two streams, Blake and Sannes Creeks, had received plantings earlier in the sampling year, and all stocked trout were catchables whereas our samples consisted ex- clusively of sublegal fish. Moreover, virtually all samples produced satisfactory agreement on phenotypic frequencies with Hardy-Weinberg expectations.

Several mechanisms may be hypothesized to account for an Ldh-B= allelic shift among Wis- consin populations in response to stocking: in- terbreeding of wild and hatchery trout; or dif- ferential mortality resulting from increased fishing pressure; or ecological interactions be- tween.the two stocks. In this instance we doubt

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

GENETIC IMPLICATIONS OF BROOK TROUT STOCKING 285

that there has been any significant genetic in- termingling of wild and hatchery fish. Stocked brook trout suffer high natural and fishing mortality in comparison to other cultured trout species (Cooper 1952; Onodera 1962). In Wis- consin streams, neither fingerlings nor catch- ables survive in adequate numbers to constitute a breeding stock (Brynildson and Christenson 1961; Mason et al. 1967). If interbreeding has occurred in the study streams, its effect might be expected to be evident at the Tf locus as well. There is, however, no compelling evi- dence for such an effect. Although hybridiza- tion between brook and brown trout has been

reported in Wisconsin streams (Brasch et al. 1973), its occurrence is extremely rare, hybrids are typically sterile, and none of our electro- phoretic patterns suggest genetic introgression.

Thuemler (1975) reported that stocking de- presses the standing crop of native brook trout in Wisconsin streams. Clady (1973) and Vincent (1975) provided similar examples among other native trout populations. In part, this impact may reflect overharvest of the wild fish as a re- suit of increased angling pressure. Butler and Borgeson (1965) suggested that native trout may actually become more susceptible to an- gling in such circumstances, either through be- havioral modification or increased competition for food. Miller (1957) speculated that intensive angling might alter native gene pools by select- ing for characters such as growth or intelli- gence.

In a review, Clady (1973) noted that ecolog- ical interactions between wild and catchable

trout may result in increased natural mortality of wild fish through social stress, fatigue, or depletion of body metabolites. Delayed mortal- ity due to poor body condition may be a latent effect. Establishment of larger exotic species such as brown trout can have a significant neg- ative impact on native trout through predation (Shetter and Alexander 1970). Introduction of parasites and diseases into wild populations via stocking is yet another possible genetic influ- ence.

The present study is inadequate to determine which potential contributors to differential sur- vival of native brook trout might be operative at the Ldh-B2 locus. There is evidence, how- ever, that LDH genetic systems of fishes re- spond to natural and artificial selective pres- sures. Merritt (1972) observed north-south

clinal variation of LDH alleles among Pime- phales promelas populations of the central United States, and demonstrated that catalytic properties of the allozymes are adapted to pre- vailing environmental temperatures. Among Pacific coast rainbow trout stocks, allelic varia- tion at the Ldh-B• locus is related to stream velocities (Northcote et al. 1970; Huzyk and Tsuyuki 1974). Physiochemical analyses further indicate that significant functional differences may exist among the Ldh-B• allozymes (Tsu- yuki and Williscroft 1973; Wydoski et al. 1976; Kao and Farley 1978). The suggestion that the B•' allele may confer superior swimming en- durance was experimentally tested by Tsuyuki and Williscroft (1977) and by Wydoski et al. (1976). Conclusions could not be drawn from the latter study because of the poor health of the test fish, but the former demonstrated sig- nificant swimming stamina differences between phenotypes and between populations.

Although direct information on the possible adaptive significance of brook trout LDH allo- zymes is lacking, it is noteworthy that Wright and Atherton (1970) found greater Ldh-B2 variability among hatchery stocks than among •'ild populations. In particular, among hatch- ery stocks from New Hampshire, New York, Ontario, Washington, and West Virginia, the B• allele was consistently less common than among wild eastern populations while the B•' allele was more frequent. Greatest divergence from the native condition existed among a sec- ond generation synthetic strain produced from survivors of furunculosis disease. Allelic fre-

quencies in the disease-selected stock were B• = 0.22, B•' = 0.50, and B2" = 0.28. In contrast, at the Tf locus, there was good agreement be- tween allelic frequencies of hatchery and wild stocks, Tf c dominating in virtually all popula- tions. Hershberger (1970) found no differences in the iron binding capacities of A, B, and C type transferrin although A type differed struc- turally from the other two forms. The available evidence suggests, therefore, that the Ldh-B= and Tf systems of brook trout may differ both in terms of the functional significance of allelic products and in responsiveness to natural and artificial selection. Information on the physio- chemical properties of Ldh-B= allozymes is needed. Additional research on patterns of al- lelic variation at both loci, as well as for other genetic systems, is also required for determi-

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

286 FARRINGER ET AL.

nation of the impact of stocking upon wild gene pools.

Acknowledgments

This research was performed through a co- operative research agreement with the Wiscon- sin Department of Natural Resources. We are indebted to Robert Hunt, Harrison Sheldon, and Kent Niermeyer of the Coldwater Research Group, and to Lee Haas of the Osceola State Fish Hatchery, for their assistance in fish col- lection. Lyle Christensen, John Klingbiel, and Robert Hunt commented on the manuscript. Statistical consultation was given by David Cox and Paul Hinz of the Iowa State University Sta- tistical Laboratory. Financial support was pro- vided by the Iowa State University Graduate College and the Iowa Agriculture and Home Economics Experiment Station. Portions of this paper are based upon a thesis submitted by the senior author in partial fulfillment of the re- quirements for the degree of Master of Science from Iowa State University.

References

BALSANO, J. S., ANn E. M. RASCH. 1974. Microspec- trophotometric and enzyrnatic analyses of fish plasma proteins electrophoretically separated in thin polyacrylamide gels. Journal of Fish Biology 6:51-59.

BRASCH, J., j. McFAnnEN, ANn S. KMIOTEK. 1973. Brook trout life history, ecology and manage- ment. Wisconsin Department of Natural Re- sources Publication 226.

BRYNILDSON, O. M., AND L. M. CHRISTENSON. 1961. Survival, yield, growth, and coefficient of con- dition of hatchery-reared trout stocked in Wis- consin waters. Wisconsin Conservation Depart- ment Miscellaneous Report (Fisheries) 3.

BUTLER, R. L. 1975. Some thoughts on the effects of stocking hatchery trout on wild trout popu- lations. Pages 83-87 in W. King, editor. Wild trout management. Trout Unlimited, Denver, Colorado, USA.

BUTLER, R. L., AND D. P. BORGESON. 1965. California "catchable" trout fisheries. California Depart- ment of Fish and Game Fish Bulletin 127.

CALAPRICE, J. R. 1969. Production and genetic fac- tors in managed salrnonid populations. Pages 377-388 in T. G. Northcote, editor. Symposium on salmon and trout in streams. H. R. MacMillan

Lectures in Fisheries, University of British Co- lumbia, Vancouver, Canada.

CLADV, M.D. 1973. Catchable trout: a literature sur- vey and recommendations for use. Oregon State Game Commission, Federal Aid in Fish Resto- ration Job F-94-R Final Report, Portland, Ore- gon, USA.

COOPER, E. L. 1952. Returns from plantings of legal- sized brook, brown and rainbow trout in the Pi-

geon River, Otsego County, Michigan. Transac- tions of the American Fisheries Society 82:265- 280.

ECKROAT, L. R. 1971. Lens protein polyrnorphisrns in hatchery and natural populations of brook trout, Salvelinusfontinalis (Mitchill). Transactions of the American Fisheries Society 100:527-536.

ECKROAT, L. R. 1973. Allele frequency analysis of five soluble protein loci in brook trout, Salvelinus

fontinalis (Mitchill). Transactions of the American Fisheries Society 102:335-340.

FLICK, W. A., AND D. A. WEBSTER. 1975. Movement, growth, and survival in a stream population of wild brook trout (Salvelinus fontinalis) during a period of removal of non-trout species. Journal of the Fisheries Research Board of Canada

32:1359-1367.

HERSHBERGER, W. K. 1970. Physical-chemical prop- erties of transferrin types in brook trout. Trans- actions of the American Fisheries Society 99:207-218.

HOFFMAN, A.D. 1966. Determination of transferrin types in brook trout by means of polyacrylamide disc electrophoresis. Master's thesis. Pennsylva- nia State University, University Park, Pennsyl- vania, USA.

HUNT, R. L. 1965. Dispersal of wild brook trout dur- ing their first summer of life. Transactions of the American Fisheries Society 94:186-188.

HUNT, R. L. AND O. M. BRYNILDSON. 1964. A five- year study of a headwaters trout refuge. Trans- actions of the American Fisheries Society 93:194-197.

HUZYK, L., AND H. TSUYUKI. 1974. Distribution of LDH-B" gene in resident and anadromous rain- bow trout (Salmo gairdneri) from streams in British Columbia. Journal of the Fisheries Re- search Board of Canada 31:106-108.

KAO, Y. J., AND m. M. FARLEY. 1978. Purification and properties of allelic lactate dehydrogenase iso- zymes at the B 2 locus in rainbow trout (Salmo gairdneri). Comparative Biochemistry and Phys- iology B Comparative Biochemistry 61:507-512.

KRUEGER, C. C. 1976. Effects of stocking on genetics of wild brook trout populations. Master's thesis. Iowa State University, Ames, Iowa, USA.

MARKERT, C. L., AND I. FAULHABER. 1965. Lactate dehydrogenase isozyrne patterns of fish. Journal of Experimental Zoology 159:319-332.

MASON, J. W., O. M. BRYNILDSON, AND P. E. DE- GURSE. 1967. Comparative survival of wild and domestic strains of brook trout in streams.

Transactions of the American Fisheries Society 96:313-319.

McCANNON, R. B., AND G. WENNIGER. 1970. The dendrograph. Kansas State Geological Survey Computer Contribution 48, Lawrence, Kansas, USA.

MENZEL, n. W. 1976. Biochemical systematics and evolutionary genetics of the common shiner

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4

GENETIC IMPLICATIONS OF BROOK TROUT STOCKING 287

species group. Biochemical Systematics and Ecol- ogy 4:281-293.

MERRITT, R. B. 1972. Geographic distribution and enzymatic properties of lactate dehydrogenase allozymes in the fathead minnow, Pimephales pro- melas. American Naturalist 106:173-184.

MILLER, R. B. 1957. Have the genetic patterns of fishes been altered by introduction or by selective fishing? Journal of the Fisheries Research Board of Canada 14:797-806.

MILLER, R. R. 1961. Man and the changing fish fau- na of the American southwest. Papers of the Michigan Academy of Science, Arts and Letters 46:365-404.

Mg/LLER, D. 1970. Transferrin polymorphism in At- lantic salmon (Salmo salar). Journal of the Fish- eries Research Board of Canada 27:1617-1625.

MORRISON, W.J. 1970. Nonrandom segregation of two lactate dehydrogenase subunit loci in trout. Transactions of the American Fisheries Society 99:193-206.

MORRISON, W. J., AND J. E. WRIGHT. 1966. Genetic analysis of three lactate dehydrogenase isozyme systems in trout: evidence for linkage of genes coding subunits A and B. Journal of Experimen- tal Zoology 163:259-270.

NORTHCOTE, T. G., S. N. WILLISCROFT, AND H. Tsv- ¾v}cI. 1970. Meristic and lactate dehydrogenase genotype differences in stream populations of rainbow trout below and above a waterfall. Jour- nal of the Fisheries Research Board of Canada

27:1987-1995.

NYMAN, O. L. 1967. Protein variations in Salmoni- dae. Institute of Freshwater Research Drott-

ningholm Report 47:5-38. NYMAN, O. L. 1972. A new approach to the taxon-

omy of the "Salvelinus alpinus species complex." Institute of Freshwater Research Drottningholm Report 52:103-131.

ONOOERA, K. 1962. Carrying capacity in a trout stream. Bulletin of the Freshwater Fisheries Re-

search Laboratory (Tokyo) 12:1-41. SHEarER, D. S. 1937. Migration, growth rate, and

population density of brook trout in the North Branch of the Au Sable River, Michigan. Trans- actions of the American Fisheries Society 66:203-210.

SHETTER, D. S., ANO G. R. ALEXANOER. 1970. Results of predator reduction on brook trout and brown trout in 4.2 miles (6.76 km) of the north branch of the Au Sable River. Transactions of the Amer-

ican Fisheries Society 99:312-319. SMITH, O. R., ANO P. R. NEEOHAM. 1942. Problems

arising from the transplantation of trout in Cal- ifornia. California Fish and Game 28:22-27.

SMITHIES, O. 1955. Zone electrophoresis in starch gels: group variation in the serum proteins of normal human adults. Biochemical Journal 61:629-641.

SNEOECOR, G. W., ANO W. G. COCHRAN. 1967. Sta- tistical methods. Iowa State University Press, Ames, Iowa, USA.

STEEL, R. G. D., ANDJ. H. TORRIE. 1960. Principles and procedures of statistics. Mcgraw-Hill, New York, New York, USA.

STEVANICH, F. A. 1952. The population and move- ment of fish in Prickley Pear Creek, Montana. Transactions of the American Fisheries Society 81:260-274.

THVEMLER, T. 1975. Fish the blue ribbon streams. Wisconsin Conservation Bulletin 40:16-17.

TSUYUKI, H., AND S. N. WILLISCROFT. 1973. The pH activity relations of two LDH homotetramers from trout liver and their physiological signifi- cance. Journal of the Fisheries Research Board of Canada 30:1023-1026.

TsvYv}CI, H., ANO S. N. WILLISCROFT. 1977. Swim- ming stamina differences between genotypically distinct forms of rainbow (Salmo gairdneri) and steelhead trout. Journal of the Fisheries Re- search Board of Canada 34:996-1003.

VINCENT, E. R. 1975. Effect of stocking catchable trout on wild trout populations. Pages 88-91 in W. King, editor. Wild trout management. Trout Unlimited, Denver, Colorado, USA.

WISCONSIN STATE CONSERVATION COMMISSION.

1930. Biennial report for the fiscal years ending June 30, 1929 and June 30, 1930. Madison, Wis- consin, USA.

WRIGHT,J. E.,JR., ANn L. M. ATHERTON. 1970. Poly- morphism for LDH and transferrin loci in brook trout populations. Transactions of the American Fisheries Society 99:179-192.

WRIGHT, J. E., JR., J. R. HECKMAN, AND L. M. ATH- ERTON. 1975. Genetic and developmental anal- ysis of LDH isozymes in trout. Pages 375-401 in C. L. Markert, editor. Isozymes III. Develop- mental biology. Academic Press, New York, New York, USA.

WYDOSKI, R. S., G. T. KLAR, T. M. FARLEY, J. C. BRA- MAN, Y-H. J. KAO, ANO C. B. STALNAKER. 1976. Genetic, biochemical, and physiological studies of trout enzymes. Utah Cooperative Fishery Re- search Unit National Marine Fisheries Service

Report, Logan, Utah, USA.

Dow

nloa

ded

by [

Mic

higa

n St

ate

Uni

vers

ity]

at 0

6:02

07

Febr

uary

201

4