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Transactions of the American Fisheries Society Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/utaf20 Growth and Survival of Rainbow , and Their Role as Prey for Stocked Salmonids in Lake Champlain Richard A. Kirn a & George W. Labar a a Wildlife and Fisheries Biology Program, School of Natural Resources, University of Vermont, Burlington, Vermont, 05405, USA Available online: 09 Jan 2011

To cite this article: Richard A. Kirn & George W. Labar (1996): Growth and Survival of Rainbow Smelt, and Their Role as Prey for Stocked Salmonids in Lake Champlain, Transactions of the American Fisheries Society, 125:1, 87-96 To link to this article: http:// dx.doi.org/10.1577/1548-8659(1996)125<0087:GASORS>2.3.CO;2

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Growth and Survival of Rainbow Smelt, and Their Role as Prey for Stocked Salmonids in Lake Champlain RICHARD A. KIRN' AND GEORGE W. LAfiAR2 Wildlife and Fisheries Biology Program, School of Natural Resources University Vermont,of Burlington, Vermont 05405,USA

Abstract.—Estimates of mean length at age and survival of rainbow smelt mordax captured at night during stepped-oblique midwater trawling in Lake Champlain in 1984-1985 were use examino dt conditioe eth populatioe th f no n befor controa e l progra a lamprese r mfo y Pet- romyzon marinus began. Stomach contents of Salvelinus namaycush, Salmo salar, walleyd an e Stizostedion vitreum were analyze asseso dt role sth f rainboe o w smelt as prey. Estimates of mean length at age did not differ among six sampling sites, suggesting there is onlpopulatioe yon f rainbono w studsmele th n yi t area. Mean length-at-age estimate 1984n si - 1985 were simila thoso rt e observe 197n di substantiallt 6bu y smaller than those observe d192n i 9 and 1950. Survival estimates of rainbow smelt in Lake Champlain were similar to those for rainbow smelt in the prior to salmonid stocking programs. Rainbow smelt was the dominant prey identified in the diets of lake trout, Atlantic salmon, and in Lake Champlain. Atlantic salmon preyed more on smaller, immature rainbow smelt than did lake trout or . Slow mortalit w growtlo d han y rate f rainboso w smel Lakn i t e Champlain indicate thapope th t - t severelulationo s nwa y affecte predationy b d .

The rainbow smelt Osmerus mordax is native to achieve optimal yields and prevent a serious de- Lake Champlai referres i earld n i n an o ydt reports cline of prey stocks (Hatch et al. 1981; Kircheis of of the lake (Thompson 1853). Stocking and Stanley 1981; Heist and Swenson 1983; Eck of rainbow smelt was carried out in the early part and Brown 1985; Jude and Teaser 1985). The ob- of this century (Greene 1930), but there are no jective studr ou f yso wer examino et describd ean e known records that evaluate the success of these the age, growth, and survival characteristics of stockings. Historically this species supportea d rainbow smelt fooe s welth a ,d s a lhabit f lako s e popular winter fishery in the lake (Greene 1930; trout, Atlantic salmon, and walleye Stizostedion Plosila and Trost 1977). The states of Vermont and vitreum, in order to define the role of rainbow smelt New York and the U.S. and Wildlife Service as prey for these predators in Lake Champlain. have stocked salmonids in Lake Champlain since 1972 (Plosil Andersod aan n 1985). From 197o 2t Study Area 1993, more than 9.5 million salmonids have been Lake Champlain lies in a north-south glaciated stocked, mostly lake trout Salvelinus namaycush fault betwee Adirondace nth k Mountainw Ne f so (40% Atlantid an ) c salmon Salmo salar (38%)e .Th Greee th Yor d n kan Mountain f Vermontso . Lake principal prey of these fish was expected to be Champlai surfaca s nha e are f 1,14ao 0a kmd an 2 rainbow smelt (LCPTC 1977). In 1990, an 8-year maximum depth of 129 m; it is dimictic, and is experimental progra a lamse r contro-e mfo th f o l thermally stratified from about the middle of June prey Petromyzon marinus initiateds wa cone th -f .I until abou middle th t f Octobereo . Maximum sur- trol program is effective, it will sharply decrease face water temperatures reach about 23°Cd an , a lamprese y abundanc d increasean e survivaf o l summer hypolimnetic temperatures are 4.5-6°C Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 salmonids and other predators of rainbow smelt. (Meyer and Gruendling 1979). The present study An understanding of the population dynamics took place near Burlington, Vermont Maie th n i , of rainbow smel responsn ti changino et g predation Lake (Figure 1), e whicth f o h account% 82 r fo s levels is needed to enable fishery managers t ototae adth lf - o surfac volum% 60 e d aree an f Lakao e just salmonid stockin harvesd gan t rate helo t s p Champlai nmillio5 (Potas9. . 1969)e al th nt f he O . juvenile salmonids stocked in Lake Champlain in 1972-1993, 85% were stocked in this section. 1 Present address: Vermont Fish and Wildlife De- partment, Roxbury, Vermont 05669, USA. Methods 2 Present address: Department of Fish and Wildlife Resources, University of Idaho, Moscow, Idaho 83844, Population characteristics.—We conducted USA. stepped-oblique midwater trawling at night (Kirn 87 88 KIRLABAD NAN R

Canada

Burlington

20km

4km

FIGURE 1.—Lake Champlal stude th yd narean a showing approximate location f trawso l surveys (straight lines) for rainbow smelt.

and LaBar 1991) to sample rainbow smelt. In alcohol (Jerald 1983) and viewed whole with a 1984-1985, two sites were chosen in each of three binocular dissecting microscop t 30-70ea X mag- depth ranges: less than 45 m, 45-75 m, and greater nification. Otoliths were aged twice firse o th tw t f ;i . Trawlintham 5 n7 g began abou afteh 1 t r sunset readings disagreed, they were age dthira d time. when rainbow smelt had completed their vertical l threIal f e readings disagree s dise fisdth wa -h migration (Kir LaBad nan r 1991). Replicate tows carded. Annulus formation and thus recruitment to were made along the same course, in opposite di- the next age-class was assumed to occur in June. rections, at each site. We sampled in August and In , annulus formation in Lake Su- Octobe rApril n i 198 d 4,an June, August- Oc d an , perior rainbow smel reportes twa begio dt Junn i e tober 1985. and be completed by mid-August (Bailey 1964). All age-1 and older rainbow smelt were counted, Mean length and variance for each age-class r catcfis0 hpe 20 ho t weran p du e measured (total were estimated by methods in Cochran (1977) for length, TL) to the nearest millimeter. Although stratified random samples. Extrapolatio f meano - age-0 rainbow smelt were captured, many escaped sured subsample totao st l catch took into account through the net meshes. For this reason, age-0 fish, the numerical proportion of each age-class in each distinguished sizy transparencyd b ean , wert eno 5-mm length intervanumericae th d lan l proportion

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 include date th an di analysis . Each catc f rainho - of each length interval within the total measured bow smel standardizes trawlinf o wa tn mi g5 5 o dt subsample. Withi age-classn na , length intervals effort (one catc r uni f hpe efforto t ; CPUEd an ) containing only one fish (and therefore no vari- used as an estimate of relative abundance (Kirn ance) were assigne pooleda d variance estimate and LaBar 1991). Otoliths were used for age de- (Bhattacharyya and Johnson 1977) calculated from terminations because the trawl-caught fish had other length intervals withi age-classe nth . Mean nearly complete scale loss. The otoliths were ex- length and variance estimates calculated from tracted from a length-stratified sample (Ketchen stratified samples precluded comparison of mean 1950) that fisr eac0 include1 fo h ho t 5-mp du m y standarb e lengtag d t a hparametri c statistical length interval represented in the catch, per site, techniques. For each sampling period, mean length in each sampling period. Otoliths were preserved at age for individual age-classes was compared in a 2:3 clearing solution of glycerin and 70% ethyl among sites containing at least 10 samples. RAINBOW SMELT STOCK IN LAKE CHAMPLAIN 89

TABLE 1.—Mean total lengths at age ± SEs of rainbow smelt captured in stepped-oblique midwater trawls at night in Lake Champlain, 1984-1985. Recruitmen nexo t t t age-class begin Junen si . Sample size showe sar parenthesesn ni .

Total length at age (mm) during: Age-class Aug 1984 Oct 1984 Apr 1985 Jun 1985 Aug 1985 Oct 1985 I 123. 0.58± 1 129.5 ± 0.50 136. 0.54± 5 89.8 ± 0.80 124. 0.47± 2 139.0 ± 0.55 (97) (171) (105) (68) (335) (195) 2 142. 0.57± 5 143. 0.47± 9 149.1 ±0.54 136. 0.55± 4 151.6 ± 0.50 155. 0.62± 6 (82) (171) (114) (192) (226) (128) 3 156.0 ± 0.59 159. 0.66± 5 162. 0.88± 0 149. 0.53± 0 155.5 ± 0.60 160.2 ± 0.59 (42) (108) (76) (180) (165) (149) 4 175.2 ± 1.01 172. 9± 1.0 0 182. 2± 1.6 2 163. 0.78± 5 171.7 ± 1.00 173.0 ± 1.00 (9) (18) (18) (109) (63) (60) 5 185.4 199.0 181.8 ± 1.04 193.1 187.1 ± 1.37 (5) (5) (28) (11) (8) 6 190.5 182 253.5 (2) (1) (2) 7 183.0 (1) 8 197.0 (1)

Estimates of survival were calculated from an- 1986). This index combines prey taxon weight and nual changes in mean CPUE for year-classes rep- frequenc f occurrencyo followine th n ei g formula: resented in the catch in August and October, 1984- 1985 (Ricker 1975). Only catches from sites sam- %FOX T , IRI%W = ' ple botn di h years were use survivan di l estimates. where %WT refers to the percentage of total Predator food habits.—Stomach samples from weight of identifiable prey in all stomachs ex- salmonids and walleyes captured in the study area percentagrefere O th amine o %F st d dan stomf eo - were obtained fro e followinmth g sources: local achs examined that contained identifiable prey in fishing derbies in June 1984 and June 1985, charter a designated prey taxon IRIe Th .' valu r eacefo h captain and angler cooperators in June 1984 prey taxon is presented as a percentage of the total through August 1985, creel surveys at fishing ac stomach-0 6 o IRI't p r montU .spe h were analyzed cess areas in March and April 1985, Vermont Fish fro stude mth y area within each 14-d interval sam- and Wildlife Department gill-net sampling in June pled. Because dietary compositions were similar and July 1984 and 1985, and Vermont Fish and between years combinee w , l sampledal analr sfo - Wildlife Department creel surveys in April-Sep- ysis. tember 1985. Fish with empty stomachs wer- eex cluded from the study. Results Stomachs (esophagus to pyloric sphincter) con- taining food were extracted ,for % place-10 n i d Population Characteristics malin lated an , r transferre ethy% 70 l o alcoholdt . Age-1 and older rainbow smelt constituted 97% Predator fish were measured to the nearest milli catce -th f 22,68f ho o 2stepped-obliqu3 6 fis n i h e meter (TL) and weighed (wet) to the nearest gram. midwater trawls in 1984-1985. Ciscoes contente Th f eacso h stomach were analyzed sep- artedi made up almost 3% of the catch.

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 arately. Prey items were identified to the lowest Of 2,948 rainbow smelt aged, agreement be- taxon possible pred an ,y taxa were weighed (wet) twee seconfirse d nth an tdetermination e dag s swa nearese th o t t 0.0 . Fis1g h stomache founth n i d s 84.5% 99.5d an , %f replicato e ages were within1 were measured to the nearest millimeter standard year. Age-1-3 rainbow smelt constituted about length (SL avoio )t d havin estimato gt lengte eth h totae th lf o catcl samplin al % n hi 90 g periodse .Th of partially digested caudal fins. The relation be- oldest rainbow smelt was an age-8, 197-mm in- tween predator and prey length was examined by dividual capture Augusn di t 1985 (Table 1). regression analysis (Dixon 1983) for each predator Mean length-at-age estimates were similar among species. the six locations in all sampling periods and were A modification of the index of relative impor- therefore combined (Table 1). Mean lengthe ag t sa tance (IRI' f Pinkao ) t ale s . (1971 s useo wa )t d for age-1-3 rainbow smelt generally were within rank dietary importance of prey taxa (Kirn f eeaco t alhm . othem 5 r among sites e maximuth , m 90 KIRLABAD NAN R

TABLE 2.—Annual surviva e l 1980-198th rate f o s 2 year-classe f rainboso w smel Lakn i t e Champlain, 1984- 1985.

CPUEa Sampling Year-class month 1984 1985 Survival5 1982 Aug 210 113 0.54 Oct 225 122 0.54 1981 Aug 83 25 0.30 Oct 106 36 0.34 1980 Aug 10 4 0.40 Oct 17 4 0.24 a Catch per unit of effort in 55 min stepped-oblique mid water trawl fished after dark. b Oct Apr Jun Aug Oct Surviva 198[ = 5l CPUE (age n)]/[ 1984 CPUE (age n- 1)] , after 1984 1985 Ricker(1975). Sampling Date FIGURE 2.—Mean total lengths of 1980-1984 year- classe f rainboso w smelt take stepped-obltquy nb e mid- (Table 3). Perca flavescens were water trawlin Lakn gi e Champlain, 1984-1985. 2.9 ciscoed %an s were tota e 2.6th l%f preo y IRI' for walleye. Rainbow smelt was consistently the most im- difference betweebeinm m g8 n sites e rangTh . e portant prey of lake trout of all sizes throughout of mean lengths of age-4 fish among sites exceeded the sampling period. Other prey taxa (exclusivf eo onlm m y onc5 foun ei r sampling period 1985n si . unidentified fish) accounted for more than 5% of Small sample size age-r solderfo d 4an fis 198n hi 4 IRI onln samplino i ' ytw g period n 1984-198i s 5 and age- olded 5an r fis 198n i h 5 precluded mean- (Figure 3). Cottus cognatus were ingful length comparisons of older age-classes 10% of IRI' in early April 1985, and yellow perch among sites. Greatest growt lengtn hi durins hwa g 11% of IRI' in early May 1985. Rainbow smelt the first year of life (Table 1), and seasonal growth unidentified an d fish were mor f IRIo e tha'% n95 fo l agegreatess al r swa t between Jun Augusd ean t for each 200-mm length interval examined for lake (Figur . Survivae2) l estimate f individuao s l age- trout (Tabl . Regressioe4) n analysis revealeo dn classes in August and October trawl catches av- significant relationship between the lengths of lake eraged 0.4 0.3 generalld d 17an an y decreased with trou ; ranget (meanmm , 4 226-8356 , 7 mm)- At , (Table ag . e2) lantic salmo ; rangn (meanmm e 5 349-6148 , 3 mm) r walleyo , rang; e (meanmm e 8 408-6957 , 0 Predator Food Habits mm) and the length of fish they consumed as prey. Rainbo wpredominane th smel s wa t t prey con- Although few Atlantic salmon were collected (N sume laky db e trout, Atlantic salmon walleyd an , e = 28), they seemed to prey on smaller rainbow (IRI', 47.4-83.1%), and rainbow smelt in combi- smelt thalakd di ne trou r walleyo t e (Figur. e4) nation with unidentified fish (probably mostly f rainboMeao L nS w stomachsmele th - n i t At f so rainbow smelt) accounted for 94.4-99.6% of IRI' lantic salmon was 69 mm (82 mm TL; N = 43),

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 TABLE 3.—Percentages of total prey weight (%WT), frequency of occurrence (%FO), and total index of relative importance (%IRI' pref )o y observe stomachn di f lakso e trout, Atlantic salmon walleyed an , s collecte Lakn di e Cham- plain in 1984-1985; N = number of stomachs.

Lake trou506= N )( t Atlanti) c 28 salmo = N n( ) Walley66 = N e( Prey %WT %FO %IRI' %WT %FO %IRF %WT %FO %1RT Rainbow smelt 63.6 69.0 68.6 79.8 57.1 83.1 41.3 40.9 47.4 1.5 0.4 3.0 3.6 0.2 20.0 4.6 2.6 Yellow perch 4.1 3.8 0.2 13.8 7.6 2.9 Unidentified fish 27.1 73.1 31.0 13.5 64.3 15.8 23.5 71.2 47.0 Miscellaneous prey0 3.7 0.2 3.7 0.9 1.4 0.1 Includes invertebratd fisan h e taxa, plant material inorganid an , c matter that individually accounte r lesdfo s than 0.5l al %f IRIr o fo ' 8 predator species. RAINBOW SMELT STOC LAKN KI E CHAMPLAIN 91

100%

80%

60% ED Rainbow smelt CC •Unidfish 40% Slimy sculpin OIDYellow perch 20% •Other

Jun Jul Jul Jul Aug Aug Apr Apr May May Jun Jun Jul Jul Jul 9 2 4 1 1 6 1 3 9 1 5 1 2 8 5 2 2 1 9 2 4 1 1 16 (34) (54) (59) (24) (5) (13) (23) (31) (13) (48) (41) (44) (22) (43) (51) 1984 1985 FIGURE 3.—Percent IRI' of stomach contents of lake trout from Lake Champlain, 1984-1985. Numbers in parentheses below each date represent the number of lake trout analyzed within the date interval.

wherea rainboe sth w smelt eate laky nb e trout (N Discussion = 734) and walleyes (N = 51) averaged 123 mm rainboe th s A w smelt populatio Lakn ni e Cham- SL (145 mm TL). If Lake Champlain rainbow plai preyes ni d upon more heavily wilt i , l probably smelt do not spawn until their second year, when respond with increased growth rates, shifts in age they are generally 130 mm or longer (110 mm SL), composition, reduced densities, increased fecun- Atlantic salmon preyed much more heavily upon dity, earlier maturation perhapd an , s shift span i s - immature rainbow smelt (77% of prey were small- tial distribution (Stewar t ale t . 1981; Frid an e er than 110 mm SL) than did walleyes or lake trout Spangler 1985). Declines in salmonid growth rates (<16%). Forty-five Atlantic salmon collected in (Negus 1995) or shifts by salmonids and other Lake Champlain outside the study area also se- predator alternativo st e prey could also indicatea lected smaller rainbow r smelo L S t (meanm m 6 9 , rainbow smelt population in decline (Stewart et al. wer% 77 e ; lesTL s 11tham 4m n SL)11m 0m . 1981). These observations were consistent with follow- Mean length-at-age estimates of rainbow smelt up studies of 65 Atlantic salmon from Lake Cham- have shown little change from those reporten i d plain in 1993 analyzed for stomach content. Of the 1976 (Plosil d Trosan a t 1977) durin e earlth g y 2 rainbo43 w smelt observe e die f th theso t n di e stages of the salmonid stocking program (Figure fish, 98% measured less than 110 mm SL (G. W. 5). Rainbow smelt growth was, however, substan-

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 La Bar, unpublished data). tially slower than reported in 1929 (Greene 1930)

TABLE 4.—Percentages of total index of relative importance (%IRI') of prey in stomachs of lake trout of different sizes collecte Lakn di e Champlain, 1984-1985 numbe= N ; f lako r e trout stomachs.

201-400-mm lake trout 401-600-mm lake trout 601-800-mm lake trout 1984 1985 1984 1985 1984 1985 Prey ) 35 (= N (= N13 ) (N) =79 (N = 192) (N = 78) (N = 107) Rainbow smelt 55.2 58.1 63.4 70.5 79.1 67.5 Unidentified fish 41.3 41.9 35.3 29.1 20.6 32.2 Miscellaneous 3.5 0.0 1.3 0.4 0.3 0.3 92 KIRLABAD NAN R

100 140 180 Smelt Standard Length (mm) FIGURE 4.—Length-frequency distributions (standard length f rainboo ) w smelt observe e stomachth n i d f o s Atlantic salmon 43)(N= , walleyes (N 51)= laked an , trout (N734= ) from Lake Champlain, 1984-1985.

and 1950 (Zillio d Youngan x s 1958) wheo tw n pling sites during this study, particularly in April "races" of smelt were suspected to inhabit Lake when spawning behavior would serv separato et e Champlain. Greene (1930) reporte a dlarg d an e stocks, faile indicato dt existence eth f discreteo e small race of rainbow smelt based upon the ex- populations of rainbow smelt in our study area. istenc f bimodaeo l length distribution f individso - This result is supported by an unpublished study ual age-classes e smalTh . l race averaged 60-90 of biochemical genetics of rainbow smelt in Lake mm smaller per age-class and constituted 30% of Champlain that showed little genetic variability the sample from ice-fishing surveys conducted in among samples from several sites throughout the 1929 (Greene 1930). By 1950, the small race ac- lak. DeHayes(D e , Universit f Vermonto y , Bur- ice-fishincountee th f o onlr dfo % y4 g survey sam- lington, personal communication). f rainboo e pl w smelt (Zillio Youngd xan s 1958). Annual survival rate f 37-41so % estimaten di It is not known if the changes in mean length at this study were simila thoso t r f rainboeo w smelt Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 since ag e 1950 represent true decrease growtn si h r changeo Lake th en si Champlai n rainbow smelt in South Bay, Lake HuronLakn i d e an ,Superio r stock. However cleas i t i , r that growt f rainboho w prio o salmonit r d stocking programs (Frid an e smel s presentli t y slow and, despite more thana Spangler 1985). Surviva f rainboo l w smeln i t decad f salmonieo d stocking t showno e s nth ha , South Bay, , changed from 10% during increases characteristi f overexploitatioco n (Frie periods of an intensive dip-net fishery to 33% dur- and Spangler 1985). ing period commerciao n f so lpred w fisherfe -d yan Although difference mean si n lengthave ag et ha ator 15o st % during high predator abundance. Sur- been used to describe discrete stocks in rainbow vival of Lake Superior rainbow smelt decreased smel othed an t r fish species (Ihsse t alne . 1981; laks a e % trou20 o tt biomasfro% m43 s increased. Gulland 1983; Luey and Adelman 1984), uniform Decreases in survival rates of Lake Champlain estimates of mean length at age among six sam- rainbow smelt shoul expectee db lamprea se s da y RAINBOW SMELT STOCK LAKN I E CHAMPLAIN 93

300

FIGURE 5.—Mean total length at age of rainbow smelt in Lake Champlain in 1929 (Greene 1930), 1950 (Zilliox and Youngs 1958), 1976 (Plosila and Trost 1977), and 1985 (this study).

control is effected and predator abundance increas- rainbow smelt (ages 0-2) typically inhabit waters es. abov e thermoclineeth , thus limiting their avail- Lake troud Atlantian t c salmon, which were abilit salmonio yt d predators that prefer lowe- rwa l salmonidal f o nearl % s 80 ystocke n Laki d e r temperatureste . Althoug depte hth h distributions Champlain in 1972-1993, fed almost exclusively of Atlantic salmon and lake trout overlap, Atlantic on rainbow smelt during this study. Walleyes also salmon ten inhabio dt t shallower depths (Warner relied heavily on rainbow smelt. Atlantic salmon and Havey 1985), which probably places them seemed to prey more on smaller, immature rainbow closer to younger rainbow smelt. smelt than did lake trout or walleyes. Warner and Population f rainboo s w smelt undergo extreme Havey (1985) reported landlocked Atlantic salmon fluctuations in abundance, apparently unrelated to t exhibino d tdi size-selective feedin rainbon go w such traditional cause s stoca s k size, predation, smel Mainn i t e lakes. Speirs (1974), however- re , competition, fishing intensity, or disease (Smith ported tha substantiaa t summee l th par f o t r diet 1972; Havey 1973; Kirchei Stanled an s y 1981); landlockef o d Atlantic salmo Maina n i e lake con- such fluctuations limi e reliabilitth t f rainboo y w sisted of young-of-the-year alewives Alosa pseu- smelt as a primary prey (Lackey 1969; Kircheis

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 doharengus, and older alewives were not con- and Stanley 1981). LaBar (1993) reported sub- sumed. stantial fluctuation abundancn si f rainboeo w smelt We believe the differences in the size of rainbow in Lake Champlain s indicatea , y largdb e varia- smelt eaten by lake trout and Atlantic salmon may tions in trawl catches. Variable year-class strength reflect the spatial distribution of both predator and in rainbow smel s beeha t n documente othen i d r prey. Size partitioning among rainbow smelt pop- lake systems (Ferguson 1965; Leac Nepszd han y ulations, with smaller individuals inhabiting shal- 1976; Murawski and Cole 1978; Frie and Spangler lower depths, has been observed horizontally 1985). Because spawning stocks of rainbow smelt along the bottom during the day (MacCallum and are generally dominated by only two year-classes Regier 1970; Argyle 1982; Plosila 1982) and ver- (Baldwin 1950; McKenzie 1958; Bailey 1964; tically in midwater at night (Kirn and LaBar 1991). Murawsk Cold an ie 1978) a singl, e weak year- Lantry and Stewart (1993) suggested that younger clasleavy populatioe sma e th n vulnerabl preo et - 94 KIRN AND LABAR

datio unfavorabld nan e environmental conditions Acknowledgments (Stewart et al. 1981; Frie and Spangler 1985). We than . FurbushkR , captaie researcth f no h Although short-term change n consumptioi s n vessel RVDore, valuablr fo e assistance throughout rates of lake trout may provide a stabilizing effect studye th alse W o. than . NewbroughkK . LawM , - on fluctuating prey populations, this specie- be s si rence. MartiJ d their ,an n fo rlaboratore helth n pi y lieved to provide little potential for responsive and field. B. Johnson critically reviewed the manu- management manipulations (Stewart et al. 1981, . Badge. scriptHayeG D d d san ,an r provide- dad 1983) lone Th .g cycl f predatoreo y effec r thifo ts vice on statistical techniques. The Vermont Fish species, peaking 3-5 years after stocking and last- and Wildlife Department provided its research ves- ing 7-8 years, precludes the use of stocking ad- sel and assisted in the collection of predator stom- justments to offset fluctuations in prey abundance ach samples. The project was partially funded by (Stewar . 1981al t e t, 1983). U.Se th . FisWildlifd han e Service, Anadromous Atlantic salmon, therefore, may provide the only Sport Fish Conservation Program, Project AFS-6- short-term stocking mechanism available for fish- R-2. eries managers to realistically affect a declining rainbow smelt population in Lake Champlain. References Through bioenergetics modeling, Negus (1995- )re ported cumulative prey fish consumptio f "typno - Argyle, R. L. 1982. Alewives and rainbow smelt in Lake Huron: midwater and bottom aggregations and ical" creeled Atlantic salmon (age 4) to be nearly estimates of standing stocks. Transactions of the double tha f lako t e trout (ages 6-9 Lakn )i - eSu American Fisheries Society 111:267-285. perior. These simulations also indicatee d thaag y tb Bailey, M. M. 1964. Age, growth, maturity and sex , cumulativ4 e consumptio pref no y fis Atlantiy hb c compositio Americae th f no n smelt, Osmerus mor- salmon was nearly 10-fold greater than by lake dax (Mitchill), of western Lake Superior. Transac- e Americationth f o s n Fisheries Society 93:382- same trouth f e o tage additionn .I consuminy b , g 395. immature rainbow smelt as observed in this study, Baldwin, N. S. 1950. The American smelt, Osmerus Atlantic salmon have a greater potential to reduce mordax (Mitchill), of South Bay, Manitoulin Island, survival of rainbow smelt to reproductive size than Lake Huron. Transactions of the American Fisheries would lake trout. Society 78:176-180. Bhattacharyya, G. K., and R. A. Johnson. 1977. Sta- During this study the rainbow smelt population tistical concepts and methods. Wiley, New York. in Lake Champlai t adversele seeb no m o t d ndi y Cochran . 1977G . ,W . Sampling techniques. Wileyw ,Ne affected by predation, as indicated by low growth York. rate mortalitd san rainbof yo w smelt excellene ;th t Dixon . J.,W ,editor . 1983. BMDP statistical software. growt f trou ho salmod an t n (Plosil Andersod aan n Universit f Californiyo a Press, Berkeley. 1985) further indicate that food is not a limiting Eck, G. W., and E. H. Brown, Jr. 1985. 's capacit supporo t y t lake trout (Salvelinus namay- factor. However, dramatic increases in abundance cush) othed an r salmonines estimatn a : e basen do and surviva f stockeo l d salmonids relian rainn o t - the status of prey populations in the 1970's. Ca- bow smelt as prey are anticipated following ex- nadian Journal of Fisheries and Aquatic Sciences perimenta a lamprese l y control - (PlosilAn d aan 42:449-454. derson 1985), which could contribute to the insta- Ferguson, R. G. 1965. Bathymetric distribution of American smelt, Osmerus mordax, Lakn i e Erie. bility and decline of the rainbow smelt stock. Po- Proceedings, Conference on Great Lakes Research

Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011 tential declines in lower trophic level production 65:47-60. resulting fro recene mth t establishmen- ze e th f o t . SpanglerR . G Frie d . V..R , an , 1985. Dynamicf o s bra mussel Dreissena polymorpha in Lake Cham- rainbow smelt during and after exploitation in South plain and from mandated reductions in phospho- Bay, Lake Huron. Transactions of the American Fisheries Society 114:713-724. rous inputs, will likel pressurd longe yad th n -eo Greene, C. W. 1930. The smelts of Lake Champlain. term stabilite rainboth f o yw smelt population Pages 105-129 in A biological survey of the Cham- (Jones et al. 1993). An understanding of these im- plain watershed. New York State Conservation De- pending change Lakn si e Champlain wil crite b l - partment, Supplement to the 19th Annual Report, icar fisheriefo l s manager o sustait s n salmonid 1929, Albany. populations and their associated recreational fish- Gulland, J. A. 1983. Fish stock assessment: a manual of basic methods. Wiley-Interscience, New York. eries without impacting the rainbow smelt popu- . BrownH Hatch . . Haak E . . M 1981W. Jr d ,. R , P ,an , . lation which supports them. Estimation of biomass in Lake Michigan, RAINBOW SMELT STOC LAKN KI E CHAMPLAIN 95

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Michigan. Transaction Americae th f so n Fisheries Warner . HaveyA . K , .d K. 1985an , . Life history, ecol- Society 110:751-763. ogy and management of Maine landlocked salmon Stewart, D. J., D. Weininger, D. V. Rottiers, and T. A. (Salmo salar). Maine Department of Inland Fish- Edsall. 1983 energeticn A . s mode r lakfo l e trout, erie Wildlifed san , Augusta. Salvelinus namaycush: application to the . YoungsLakD . eW d . Zillioxan 1958 , G. .. R ,Furthe r studies Michigan population. Canadian Journal of Fisheries e smelth f Lakn o t o e Champlain Yorw Ne k. Fish and Aquatic Sciences 40:681-698. and Game Journal 5:165-174. Thompson . 1853Z , . Natural histor Vermontf yo . E . C . Received Apri , 1998 l 2 Tuttle, Rutland, Vermont. Accepted July 11, 1995 Downloaded by [University of Vermont], [J. Ellen Marsden] at 08:17 14 December 2011