Transactions of the American Fisheries Society, Volume 120, Issue 3 (May 1991) Pp

Home , Bluegill, Threadfin shad

Transactions of the American Fisheries Society, volume 120, issue 3 (May 1991) pp. 368-381. ISSN 0002-8487 DOI: 10.1577/1548-8659(1991)120<0368:STSCFY>2.3.CO;2 http://afs.allenpress.com/perlserv/?request=get-archive http://afs.allenpress.com/archive/1548-8659/120/3/pdf/i1548-8659-120-3-368.pdf © American Fisheries Society Transactions Americane oth f Fisheries Society 120:368-381, 1991

Stocking Threadfin Shad: Consequences for Young-of-Year Fishes DENNIS R. DEVRiES,1 ROY A. STEIN, AND JEFFREY G. MiNER2 Ohio Cooperative Fish and Wildlife Research Unit3 and Department of Zoology The Ohio State University, Columbus, Ohio 43210,USA GARY G. MITTELBACH Kellogg Biological Station, Michigan State University Hickory Corners, Michigan 49060,USA

Abstract.— Threadfin shad Dorosoma petenense commonle ar y introduced into reservoiro t s supplement prey availabl piscivorouo et s fishes determino T . earlw eho y life stage threadfif so n shad and their potential competitors and predators interact, we introduced this species into two Ohio lakes—Clark and Stonelick—and evaluated how its young of year influenced young-of-year bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides. After adults were stocked in April, peak abundance of young-of-year threadfin shad occurred in August in both lakes. Bluegills generally spawned earlier than threadfin shad, which apparently reduced competition between young of these species. In Clark Lake, young-of-year threadfin shad did not reduce zooplankton populations, but in Stonelick Lake, peak abundance of young-of-year threadfin shad was followed by a precipitous decline in zooplankton. Data on cladoceran birth rates indicated this decline was due to increased predation by threadfin shad. Survival of bluegills to a size at which they move int littorae oth l zone also decline Stonelicn di k Lake, perhaps becaus virtuae th f eo l elimination of zooplankton. Limited survival of bluegills in turn contributed to reduced growth of young-of-year largemouth bass dependent on them as prey. Given that zooplankton declined othee th t r lakeno t ,bu interactione inon s among young-of-year annuall o fishet e sdu y introduced threadfin shad will likely vary among system yearsd san . Nonetheless, introduced threadfin shad could, in some systems in some years, negatively affect growth and recruitment of the very species they were meant to enhance.

Manipulation of prey has become a popular described manipulations involving two clupeid technique for increasing production of sport fishes species (gizzard shad Dorosoma cepedianum and (Ney 1981; Noble 1981,1986; Wydoski and Ben- threadfin shad D. petenense) and four target spe- nett 1981; DeVrie Steid san n 1990). Manipula- cies (white crappie Pomoxis annularis, black crap- tions may involve the introduction of prey to in . nigromaculatus,-P e pi largemouth bass Microp- creas fooe eth d remova e basth r eo planktivoref lo s terus salmoides, and bluegill Lepomis macrochirus) reduco t e competition between the spord man t that resulted in positive, neutral, and negative ef- fishes. Numerous taxa have been used in these fects on the target species. Thus, introducing prey manipulations, including member Athere th f so - for predators or removing presumedly undesirable inidae, Catostomidae, Clupeidae, Coregonidae, competitor increast no y esma adult growt tarf ho - Cyprinidae d Percidaan , e (see referencen i s ge resuly t specie ma othern i t d san , unexpected DeVrie Steid san n 1990). These manipulations, consequences. based primarily on predator-prey interactions be- Because angler interestee sar largn di e fishe th , tween introduced prey and adults of the target spe- adult stag sporf eo t bees fishha n most studiedn i cies, sought to enhance the target sport species. relatio preo nt y manipulations. Other life stages However, enhancemen t alwayno s stha beee nth (larvae, juveniles pre f predator)d o yan s have been result. In a recent review, DeVries and Stein (1990) largely ignored (but see Kirk 1984; Kirk and Da- vies 1987). Because fish often change their diets and habitat thes a s y grow (Werne Gilliad an r m 1 Present address: Department of Fisheries and Allied 1984), species that interact as predator and prey Aquacultures, Auburn University, Auburn, Alabama adults a compety sma t earlieea r life stages- Ex . 36849, USA. 2 amples include largemouth bas bluegilld san s (Gil- Present address: Departmen f Zoologyo t , Miami liam 1982 Europead )an n perch Perca fluviatilis University, Oxford, Ohio 45056, USA. 3 The Unit is sponsored jointly by the U.S. Fish and and roach Rutilus rutilus (Persson 1988). Many Wildlife Service, Ohio Departmen f Naturao t - Re l fishes have Limnetic, zooplanktivorous larvae sources, The Ohio State University, and the Wildlife (Werner 1967; Barge Kilambd an r i 1980; Keast Management Institute. 1980; Beard 1982; Mills et al. 1987); where such 368 THREADFIN SHAD EFFECTS ON YOUNG OF YEAR 369

fishe introducee ar s preys da , competthey yma e during both stockings. Poststocking predatory during this life stage with larva f theieo r subse- mortalit largemoute monitores on y; wa d 3 r hdfo quent predators. Because year-class strength is collecte2 bas2 f so Clardn f 10i o 3e k Lakon d ean typicall t earlyse lifn yi e (Gushing 1975; Lasker collecte Stonelicdn i k Lak eated threade eha non - 1975; Ware 1980; Mill Forned san y 1988), inter- fin shad each r additionaFo . l details concerning actions during this critical perio havy dema major collection, transport stockind ,an g procedurese ,se effect sport-fisn so h surviva subsequend lan t har- Buynak et al. (1989) and Austin and Hurley (1989). vest. Thus, interactions at all life stages may de- Sampling methods.— samplee W d during April termine the success of any prey manipulation, the through October in preshad (1987) and shad (1988) overall outcome depending on some combination years. Because threadfin shad cannot overwinter of potential positive and negative effects. in Ohio lakes, any effects they have on resident We quantified how young bluegills responded fish must occur durin growine gth g season after introductioe toth n of threadfi nOhio shatw o dn i stocking. Larval fish (limnetic young-of-year fish demonstratee w lake d san potentiae dth negr fo l - susceptible to the sampling gear) were collected ative effects due to interactions among larvae. Be- offshore once per week in two replicate surface cause young-of-year bluegills are also important tows with a 0.75-m-diameter, 500-/ttm-mesh prer young-of-yeafo y r largemouth bass after ichthyoplankton net towed in the limnetic zone at moving into the littoral zone at a size between 10 1.5 m/s or faster. A flowmeter mounted in the standarm m 5 2 dd lengtan h (Werner 1967; Storck mouth of the net allowed calculation of the total 1978; Werne Hald ran l 1988) alse ,w o determined volume of water filtered. Juveniles were collected hoe offshorwth e interactio f bluegillo n s with biweekl t fouya r (Clark Lake r fivo ) e (Stonelick threadfin shad might indirectly affect growth and Lake) sites in the littoral zone with a 9-m bag seine surviva largemoutf lo h bass. (4-mm mesh) l fisAl h. were preserve- re d dan turnelaboratore th o dt y where they were identi- Methods fied and measured (total length to the nearest mm, Study lakes.— Clar d Stonelican k k lakee ar s up to 50 individuals per species), and their diets shallow, turbid reservoir southwestern si n Ohio. individual0 1 (u o pt r speciespe r datespe ) were Clark Lake Clarn i , k County0 are4 n a f ao s ha , quantified. Diets were quantified from weekly col- shorelinef hectareso m k 5 maximua ,4. , m depth lections of limnetic fish samples and from month- of 2 m, and Secchi depths varying from 25 to 75 ly collections of littoral samples (i.e., from every cm. Stonelick Lake Clermonn i , t Countyn a s ha , other sample date). We identified prey to the low- area of 69 hectares, 16 km of shoreline, a maxi- est taxonomic category possibl were % (>e80 iden- muSecchd an m , ideptm depth4 f ho s o frot 2 m2 tified to genus) and measured them to the nearest . Durin119cm studyr gou , submersed vegetation 0.1 mm. Lengths were converted to biomass by was never abundan eithen i t r lakemergend ean t usf taxon-specifio e c length-dry-weight regres- vegetation occupie shoreline th df abouo f % eo t25 . MittelbachsionG . s(G , unpublished data). Clark Lake (cattails Typha spp.) and 70% of the Integrated zooplankton samples (two tube hauls shorelin Stonelicf eo k Lake (Typha spp wated .an r sampler pe , three replicate sample dater spe ) were willow Justicia americana). Neither lake stratified collected with a 2-m tube sampler (7.30-cm inside thermally, and dissolved oxygen concentrations diameter, 54-/im mesh size; DeVries and Stein fell belo wmg/3 L botto e onlth yf o mwithi m 5 n0. sam1991e th t e)a time larval fish were collected. in Clark Lak Stonelicn beloi d ean m w2 k Lake. Samples were preserved in 5% sucrose formalin Fish communitie botn si h lakes consisted primar- (Haney and Hall 1973) to prevent cladoceran egg illargemoutf yo h bass, white crappies, bluegills, loss. Zooplankton taxa with less than 200 indi- longear sunfish Lepomis megalotis, brown bull- viduals per sample were counted in their entirety; head Ictalurus nebulosus, and common carp Cy- subsamples were take morr nfo e abundant taxa prinus carpio. until at least 200 individuals were counted. At In collaboration with personnel fro Ohie mth o least 20 individuals of each taxon in a sample were and Kentucky Departments of Natural Resources, measured (total body length excluding spines, hel- we stocked adult threadfin shad from Herrington mets caudad an , l rami) wit oculan ha r microme- Lake (Mercer County, Kentucky t densitiea ) f so ter. fish/hectar8 4 Clarn ei kfish/hectar9 5 Lak d ean e To evaluate the degree of resource overlap be- in Stonelick Lake on 14-18 April 1988. Transport tween young-of-year bluegill young-of-yead san r mortality was visually estimated at less than 1% threadfin shad when both were present in the lim- 370 DeVRIES ET AL.

netic zone usee w ,d Schoener's (1970) inde, xa were intereste changen di s withi nlaka e across average baseth n do e proportion that each prey years, sample sites within a lake were treated as taxon contribute totao st l biomas fisn si h diets. replicates. All data were log-transformed. proportioe Th calculates nwa individuar dfo l fish and averaged across fish for particular dates (Wal- Results lace 1981). The formula for this index is Young-of-Year Fish Abundance -0.5(2 Although young-of-year threadfin shad were first \i-i collected offshor Clarn ei Stonelic d kan k laken si r is the proportion of prey taxon / in the diet of mid-May, their densities remaine (<0.w dlo 2 fish/ xi m3) until peaks of 8.8 fish/m3 in Clark Lake and species x, ryi is the proportion of prey taxon i in 3 the diet of species y, and n is the number of prey 2.3 fish/m in Stonelick Lake were reached in Au- categories. This index range value; s1 froo t sm0 gust 1988 (Figure 1). Young of year were collected near zero indicate little overlap, and overlap in- through September 1988 in both lakes (Figure 1). In Clark Lake, young-of-year bluegiils collected creases as values approach 1. Because young-of- 3 year zooplanktod fishan n communities changed offshore peake fish/m6 3. t da n 1987 i , whereas several peaks occurred in 1988; however, 1988 through time, we treated overlap measures cal- 3 culate eacr dfo h sample dat replicatess ea . densities were always less than 0.2 fish/m (Figure evaluato T e prey selection comparee w , d diets 2). Abundance differed between years (F = 130.24; of young-of-year fish with zooplankton samples df = 1, 2; P = 0.008), although the year x time by means of Chesson's alpha (Chesson 1978,1983), interaction term was significant (F = 80.23; df = treating individual fish within a size range as rep- 18,36; P = 0.007) because of protracted spawning licates formule .Th thir afo s indes xi during 1988 wouls A . expectee db d from difference n limnetii s c young-of-year bluegill abun- alpha = dance between years, more juvenile bluegiils were caugh littoran i t l seine hauls during 1987 than i 1988 (Figure 2; F= 50.42; df = 1, 6; P = 0.0004). Pi is the proportion of prey item i in the environ- As with offshore larvae protractee th , d spawning men t proportioe (i.e. th lake)e s rth d ,i , an , f no during 1988 led to a significant year x time in- prey item i in the fish's diet. Calculation of this teraction term for inshore bluegill abundance (F index was based on representation of prey in in- 16.69= =; P d; 0.0001)10f= 60 , e spitn .I th f eo dividual fish guts and in the zooplankton com- overall between-year difference abundancen si o ,n munity. Preferenc variour efo s zooplankton taxa differenc littoran ei l bluegill densitie detects swa - was determined by comparing alpha values (±95% able after August (univariate ANOVA 0.06= F , ; confidence interval taxo,a CIr )fo n wit alphe hth a df= 1,40;P=0.81). value expected if prey had been eaten in propor- In Stonelick Lake, young-of-year bluegiils con- tio theino t r availability (i.e. reciprocae ,th e th f lo tinuously recruited to the open water during May number of prey types in the environment; Ches- through August in both years (Figure 2). Because son 1978, 1983). Alpha values exceedin- re e gth bluegiils spawned at different times in the two ciprocal indicate positive selectio prea r ynfo tax- years, the year x time interaction term was sig- on. Because soft-bodied rotifers were digested nificant (F = 29.02; df = 20,40; P = 0.006); how- quickly and rarely identified in young-of-year fish ever, overall abundanc offshorf eo e young-of-year diets, we only included hard-bodied rotifer genera bluegiil t varno y d betweesdi n years (F =0.01f ;d (Brachionus spp. and Keratella spp.) in thes 0.92)= eP anal ; . 2 Thi, -1 s = continued presencf eo yses. Four taxa (Chydorus sphaericus, Moina spp., young-of-year bluegiil limnetie th n si c zoned an , Simocephalus spp. ostracodsd an , ) were sampled their subsequent littoral migration increaso t d ,le - t werbu e never eaten t considere; no the e yar n di ing littoral catches through summer and fall of the our results. pre-threadfin shad year. In contrast, after thread- To analyze young-of-year fish and zooplankton fin shad were introduced, littoral bluegill abun- abundance data, we used repeated-measures anal- dance peaked in mid-July (Figure 2; year effect: F ysis of variance (ANOVA; SAS Institute 1985). = 7.00; df = 1,8; P = 0.03; year x time interaction With 1 year of pretreatment data and 1 year of term: F = 4.76; df = 10, 80; P = 0.006). Appar- posttreatment data, years witd withouan h t ently, there was low survival from the peak pro- threadfin shad represented treatments. Because ew duction of limnetic larvae in late July. THREADFIN SHAD EFFECTS ON YOUNG OF YEAR 371

D. leuchtenbergianum (Table 1). Among other taxa, calanoid copepod d Ceriodaphniaan s spp. were negatively selecte l size-classesal y db ; Bosmina longirostris, Daphnia parvula, cyclopoid copepods, and rotifers either were eaten in proportion theio t r availabilit r weryo e selected againstn I . 1988, all sizes of young-of-year bluegills selected . leuchtenbergianumD (Tabl . Othee1) r prey taxa either were eaten in proportion to their availabil- itnegativelr yo y selected (Table 1). In Stonelick Lake during 1987, first-feeding bluegills selected copepod nauplii; as they grew, they shifte cyclopoio dt d copepod . leuch-D d san MAY JUN JUL AUG SEP tenbergianum (Tabl . Pre1) e y selection patterns were similar in 1988: copepod nauplii were se- MONTH lecte first-feediny db . leuchtenbergia-gD fishd an , FIGURE 1.—Densities (mean ± SE) of larval threadfin sha Clarn d i Stonelicd kan k lakes, Ohio, after adults num and calanoid copepods were selected by larg- were stocked in April 1988. younr e yeaf go r (Tabl . Othee1) r prey taxa were either eaten in proportion to their availability or negatively selected (Tabl. e1) Diets Young-of-of Year Fish Young-of-year threadfin shad in both lakes fed In both lakes, young-of-year bluegills collected entirel limnetin yo c zooplankton limnetid di s a , c offshore consumed only zooplankton during 1987 young-of-year bluegills Clarn I . k Lake, threadfin and 1988. In Clark Lake during 1987, young-of- shad selected D. leuchtenbergianum and calanoid year bluegills began feedin selecty b t 4-gm a - 7m and cyclopoid copepods, wherea n Stonelici s k ing copepod naupli Diaphanosomad ian leuchten- Lake, first-feeding threadfin shad selected cope- bergianum (Table 1). As bluegills grew, selection naupliid po , the . leuchtenbergianumnD cald an - decreased for copepod nauplii while increasing for anoid copepods (Table 2).

CLARK LAKE STONELICK LAKE

ffl

MAY JUN JUL AUG SEP OCT MAY JUN JUL AUG SEP OCT MONTH FIGURE 2.—Densitie larvaf so ) (mealSE bluegill n± limnetin si c larval tow littorad san l seine sample Clarn si k and Stonelick lakes, Ohio, before (1987, dashed line) and after (1988, solid line) threadfin shad (TS) were introduced. 372 DEVRIES ET AL.

TABLE 1 .—Food selection (estimated by Chesson's alpha; Chesson 1978,1983) by larval bluegills collected offshore in Clark and Stonelick lakes before (1987) and after (1988) threadfin shad introduction. Data are presented as means ± 95% confidence interval (N indicates sample size). Values greater than neutral selection (i.e., between 0.09 and 0.13, the reciprocal of the number of prey taxa in the lake) indicate positive selection; values less than this indicate avoidance. Bluegills 13.0 mm or larger were not collected during 1988 in Clark Lake. Prey selected Diapha- Blucgill nosoma total length Bosmina Ceriodaph- Daphnia leuchten- Calanoid Cyclopoid Copepod (mm) N longirostris nia spp. parvula bergianum copepods copepods nauplii Rotifers Clark Lake before threadfin shad introduction (1987) 4.0-6.9 19 0.00±0.01 0 0.06±0.04 0.36±0.23 0 0.06±0.09 0.49±0.22 0.03±0.05 7.0-9.9 20 0.00±0.01 0.00±0.01 0.01 ±0.01 0.80±0.15 0 0.04±0.03 0.06±0.10 0.08±0.10 10.0-12. 4 1 0.02±0.09 4 0.02±0.02 0.02±0.02 0.58±0,14 0.01±0.01 0.24±0.13 0.01±0.01 0.09±0.06 >13.4 0.06±0.10 1 0.03±0.0 0 10.78±0.2 0 0.00±0.01 0.06±0.0 0 80.07±0.0 8 Clark Lake after threadfin shad introduction (1988) 4.0-6.9 14 0.09±0.21 0.19±0.24 0.14±0.2 0 0.14±0.22 0.43±0.3 0 2 0.02±0.01 3 7.0-9.8 2 0.00±0.0 0 9 10.0 1 ±0.01 0.93±0.0 0 80.04±0.0 0.02±0.0 0 7 3 10.0-12.9 19 0.01 ±0.01 0.00±0.01 0.01 ±0.01 0.94±0.04 0.04±0.04 000 Stonelick Lake before threadfin shad introduction (1987) 4.0-6.9 27 0.01±0.03 0 0 0.12±0.19 0 0.02±0.02 0.84±0.12 0.07±0.08 7.0-9.9 29 0 ,0 0.02±0.02 0.71 ±0.15 0.02±0.02 0.18±0.09 0.18±0.11 0.04±0.05 10.0-12. 0 3 0.01±0.0 90 0.03±0.01 2 0.52±0.16 0.02±0.02 0.36±0.14 0.05±0.03 0.01±0.01 >13.0 16 0 0.03±0.03 0.10±0.05 0.44±0.20 0.04±0.04 0.35±0.19 0.03±0.03 0 Stonelick Lake after threadfin shad introduction (1988) 4.0-6.9 25 0.08±0.11 0.04±0.08 0 0.23±0.22 0.12±0.13 0.07±0.10 0.50±0.20 0.04±0.08 7.0-9.9 38 0.08±0.08 0.02±0.04 0.02±0.04 0.40±0.17 0.39±0.15 0.10±0.08 0.03±0.05 0.05±0.05 10.0-12.9 20 0.24±0.14 0.04±0.06 0.05±0.09 0.36±0.29 0.38±0.18 0.01±0.01 0.03±0.04 0.01±0.01 £13.0 11 0.13±0.20 0.00±0.01 0.03±0.05 0.76±0.24 0.07±0.05 0.02±0.05 0.01±0.03 0.03±0.07

Schoener's overlap index (Schoener 1970), which parisons involvin threadfi6 bluegil8 g7 8 d an l n varies from 0 (no overlap) to 1 (complete overlap), shad stomachs Stonelicn i ) k Lake. Diet overlap indicated diet overlaps between young-of-year values exceeded 0.50 on 2 of 8 dates in Clark Lake threadfin sha bluegilld dan s collected offshorf o e and on 5 of 13 dates in Stonelick Lake. 0.3 0.27± 0 CI comparison(mea% 8 , n= 95 n± s Bluegills collected by seining were feeding pre- involving 65 bluegill and 63 threadfin shad stom- dominantl littoran yo l prey suc chironomis ha d achs) in Clark Lake and 0.43 ± 0.08 (n = 13 com- larva pupaed ean , although some limnetic prey

TABLE 2.—Food selection (estimated by Chesson's alpha; Chesson 1978, 1983) by larval threadfin shad in Clark and Stonelick lakes during 1988. Dat presentee aar confidenc means d% a 95 s± e interval (/Vindicates sample size). Values greater than neutral selection (i.e., the reciprocal of the number of prey taxa in the lake, here between 0.09 and 0.13) indicate positive selection; values less than this indicate avoidance. Threadfin shad smallem r m tha 0 n7. were not present in Clark Lake.

Prey selected Threadfin Diapha- shad total nosoma length Bosmina Ceriodaph- Daphnia leuchten- Calanoid Cyclopoid Copepod (mm) N longirostris nia spp. parvula bergianum copepods copepods nauplii Rotifers Clark Lake 7.0-9.9 8 0.14±0.35 0 0.06±0.15 0.50±0.57 0 0.13±0.30 0.1 3 ±0.29 0.18±0.30 10.0-12.9 22 0 0 0.05±0.09 0.31 ±0.21 0.11±0.13 0.40±0.22 0.05 ±0.09 0.09±0.13 &13.0 91 0.01 ±0.01 0 0.02±0.02 0.42±0.08 0.35 ±0.08 0.19±0.07 0.01 ±0.01 0.02±0.02 Stonelick Lake 4.0-6.9 3 0 0 0 0 0 0 1.00±0.00 0 7.0-9.9 26 0 0 0 0.18±0.20 0.08 ±0.11 0.14±0.12 0.56±0.19 O.ll±0.11 10.0-12.9 38 0.03±0.05 0 0 0.33 ±0.1 6 0.35±0.15 0.11 ±0.09 0.12±0.09 0.11 ±0.10 si 3.0 72 0.02±0.02 0.02±0.03 0.02±0.03 0.24 ±0.11 0.54±0.10 0.09±0.05 0.09±0.06 0.06±0.05 THREADFIN SHAD EFFECTS ON YOUNG OF YEAR 373

CLARK LAKE STONELICK LAKE 100

JUN JUL AUG SEP OCT JUN JUL T AUOC G P SE MONTH FIGURE 3.—Diet f young-of-yeaso r bluegills collecte littorae th n di l zon f Clare o Stonelic d kan k lakes, Ohio, during 1987 and 1988. Prey were divided into limnetic zooplankton, littoral prey, and cyclopoid copepods (which occu eithen i r r habitat; Mittelbach 1981). Results were combined across sampl presentee ear sited san pers da - centages of the total biomass of prey found in all fish guts on that date. Sample sizes were 5-15 fish for each date.

also were consumed Clarn I . k Lake, bluegills col- zone. In dark Lake, the difference in abundance lected in the littoral zone fed on prey from both of young-of-year largemout t quithno bass e swa littoral and limnetic habitats during both preshad significant between years (year effect F = 5.42; df shad an d year datesx (Figursi fivn f n si O eo . e3) = 1, 6; P = 0.06), although the year x time in- fouf o ro datetw 198 d 1988n s7i an , most bluegUl teraction ter significans mwa t ( F9.34 = 11= f ,;d food came fro littorae mth l zone (e.g., chironomid 66; P = 0.006) as a result of peak abundance being larvae and pupae), and the remainder was pri- a month later in 1988 (Figure 4). As a consequence marily cyclopoid copepods. However, limnetic of later spawnin n 1988gi , young-of-year large- zooplankton remained an important diet com- mouth bass were smaller in June-July 1988 than ponent (>20% by dry weight) on two of six dates in 1987, but the difference was made up by the in 1987 and one of four dates in 1988 (Figure 3). beginnin Augusf go t (Figurfald lan size, ed 4) sdi In Stonelick Lake, inshore bluegill diets differed not differ between years (two-way ANOVA, F = dramatically between 198 d 1987an 8 (Figur. e3) 0.84; df = 1, 466; P = 0.36). In contrast to 1987, 1987n I , bluegillClarn i s a k d Lakesfe , consuming when young-of-year largemouth bass in dark Lake primarily littoral datex pre si d foun yo f an s o r littorae th fefisn o dn i h l zone when available, limnetic prey on the other two dates (Figure 3). young-of-year largemouth bass did not feed on In 1988, limnetic prey never mad morp eu e than fish during 1988 (see Figure However. 5) , s2 , bio- 2 bluegil%f o l diets (never - morcy f ei tha% n10 mass in young-of-year largemouth bass stomachs, clopoid copepods were considere exclue b o dt - measure weighy dr s pref d a o gratr y pe fishf m o , sively in open water; Figure 3). Across all date diffet sno rd betweedi n presha shad dan d years (two- during 1988, more than 90% of the bluegill diet way ANOVA, F = 2.06; df = 1, 35; P = 0.16), originate littorae th n di l zone. and growth was similar between years (Figure 4). In Stonelick Lake, young-of-year largemouth Largemouth Bass Abundance, Growth, and Diet bass were abou time0 t2 s more abundan theit ta r During both years in both lakes, young-of-year peak in 1988 than in 1987 (overall year effect, F largemouth bass were collected littorae onlth yn i l = 9.67; df = 1, 8; P = 0.01); however, abundance 374 DeVRIES ET AL.

CLARK LAKE STONELICK LAKE

T OC L Y JUJU P AUMA NSE G T OC P SE G AU L JU N MAJU Y MONTH FIGURE 4.—Densities (mean ± SE) and lengths of young-of-year largemouth bass in Clark and Stonelick lakes, Ohio. Dashed and solid lines represent estimates from before (1987) and after (1988) threadfin shad (TS) introductions, respectively.

was similar between years by late summer (Figure (Figur young-of-yeaf I . e6) r threadfi- n re sha d dha 4)additionn I . , young-of-year largemouth basn si duced zooplankton abundance, the reduction Stonelick Lake grew more slowly in 1988 than in should have been apparent after mid-August (see 1987 (Figur ; two-wae4 y ANOVA, yea timx r e Figur. e1) interaction =F : 9.29 , 380=f 0.00014 = d ; P ; ; In Stonelick Lake, as in Clark Lake, zooplank- year effect: F = 74.07; df = 1, 380; P = 0.0001). densitn to y fluctuated during 198 198d 7an 8 (Fig- Young-of-year largemouth bass primaril lowes fise ywa at h rt durinbu througy ) 6 gMa e ur h July during 1987, but they ate fish only on one date 1987 than during this period in 1988 (year x time during 1988 (Figure 5). Although young-of-year =interactionP ; 0.000176 , 19 29.49;= = :F f ;d threadfin shad were present during e mucth f ho year 0.002)= effect 61.00P = ; s F 4 : A ., ;1 df= summe n 198i r 8 (see Figur , young-of-yea1) e r in Clark Lake, zooplankton species composition largemouth bass never consumed them. In addi- did not appear to differ between years until after tion, biomass of pre largemoutyn i h bass stomachs mid-August, when small forms (copepod nauplii) (quantified as dry weight of prey per gram offish) predominated (Figure 7). During August 1988, was lowe 198n ri 8 tha 198n i 7 (two-way ANO- zooplankton density declined, and all taxa except VA, F = 14.01; df = 1, 35; P = 0.0007). copepod nauplii were essentially eliminated (Fig- ure 7). To determine whether this decline could Zooplankton Abundance be explained in part by decreased zooplankton Total zooplankton abundanc Clarn ei k Lake birth rates (i.e. reducey b , production)g deg s a , fluctuated during 198 d 1987an 8 (Figurt bu ) e6 oppose increasedo t d predation regressee ,w d mean t diffeno rd acrosdi s years (year effect 2.00= F : ; fecundity (the product of the proportion of indi- d0.23f= =P ; 1 4 yea, timx r e interaction= :F viduals carrying eggs and the mean number of eggs 0.004)= P 8.22; 16= . 64 f ,Further d ; , species individuar pe l carrying eggs) ofDaphnia parvula, compositio appeat no d diffeo nrt di r between years Bosmina longirostris, and Ceriodaphnia spp. (the (Figur Densit . declint e7) no d yedi during lat- eAu only abundant cladoceran taxa presen Augustn ti ) gusd earlan t y September 1988 after limnetic on time durin zooplanktoe gth n decline. Mean cla- young-of-year threadfin shad abundance peaked doceran fecundity did not change during the zoo- THREADFIN SHAD EFFECT YOUNN SO YEAF GO R 375

CLARK LAKE STONELICK LAKE

19881

JUNN JU T JUOC L P SE AUG JUL AUG SEP OCT MONTH FIGURE 5.—Diets of young-of-year largemouth bass collected in the littoral zone of Clark and Stonelick lakes, Ohio, during 198 1988d 7an . Prey categories consisted offish, zooplankton (ZP), corixids, surface-dwelling invertebrate suc gerrids ha s (SURFACE) othed an , r littoral invertebrates (INV). Results were combined across sample presentee ar site d san percentages da totae th lf so biomas pref so y presen l fisal h n gutti than so t date. Sample sizes wer (usuall7 e2- fiseac) r y5 h fo h date.

CLARK LAKE STONELICK LAKE

H—————I—————I—————I- L JU N JU L Y Y JUJU MA MA N T OC P SE G AU AUG SEP OCT MONTH FIGURE 6.—Densities (mea nSE± macrozooplankto f )o Clarn i Stonelic d kan k lakes, Ohio, before (1987d )an after (1988) threadfin shad introductions. Arrows indicate the date of peak abundance of limnetic young-of-year threadfin shad (TS). 376 DEVRIES ET AL.

CLARK LAKE STONEUCK LAKE

APR MAY JUN JUL AUG SEP OCT APR MAY JUN JUL AUG SEP OCT

MONTH FIGURE 7.—Representatio macrozooplanktof no n tax darn ai Stonelicd kan k lakes, Ohio, before (1987 afted )an r (1988) threadfin shad introductions. Taxa abbreviations: ca, calanoid copepods cyclopoi, ;cy d copepods; na, copepod nauplii; da, Daphnia parvula , Bosminabo ; longirostris\ , Ceriodaphniace spp. , Diaphanosoma;di leuchtenbergianum.

plankton decline ( 0.1P> 6 fothrel ral e taxa). Sim- be easily explained. Zooplankton densities and ilarly, during the threadfin shad peak in Clark Lake species compositions were simila lakeso rtw fo,e rth (mid-August through mid-September), mean fe- yet peak larval threadfin shad density was almost cundity of Bosmina longirostris Ceriodaphniad an four times higher in Clark Lake than in Stonelick spp. did not change (P > 0.31), and mean fecun- Lake. This differential response most likel- yde dity of Daphnia parvula increased (P = 0.03). rived from other differences betweesyso tw - e nth tems. First, young-of-year bluegill abundance peaked simultaneously with young-of-year Discussion threadfin sha Stonelicn di Clarn i t k kLakno t ebu Zooplankton Responses Lake. However, limnetic young-of-year bluegills We quantified differential responses of zoo- were absent after 9 August, yet zooplankton con- plankto threadfino t n shad introductions into Clark tinue declino dt e through August. Though lim- and Stonelick lakes. In Clark Lake, threadfin shad netic young-of-year bluegill havy ma se contrib- densities peaked in August without a commen- uted to the zooplankton decline in Stonelick Lake, surate decline in zooplankton. Conversely, as mors i t i e likely that young-of-year threadfin shad, young-of-year threadfin shad abundance peaked present through 7 September, were responsible. in August in Stonelick Lake, zooplankton declined Second, turbidit highes ywa Clarn i r k Lake than precipitously onld an ,y cyclopoid copepodd san in Stonelick Lake; Secchi depths during August copepod nauplii remaine densitiet da s greater than Clarn i rangem kc Lak1 fro4 d eo froan mt 7 m2 1.5 organisms/ latLy b e August. Because birth rates 80 to 81 cm in Stonelick Lake. This difference may declint no d edi across cladoceran tax Stonelicn ai k have had an effect on community-wide zooplank- Lake, declining abundance was not due to reduced tivory. Foraging efficienc juvenilf o y aduld ean t zooplankton reproduction (i.e., resources did not planktivores declines with increasing turbidity limit the zooplankton); instead, it was due to in- (Vinyard and O'Brien 1976; Gardner 1981), sug- creased death rates. gesting tha potentiae tth planktivorr lfo y coule db This differential response across systems cannot greater in Stonelick Lake (with relatively low tur- THREADFIN SHAD EFFECTS ON YOUNG OF YEAR 377

bidity) tha Clarn ni k Lake. Although both lakes exampln 198a r 5fo late-summef eo r spawniny gb support large populations of small white crappies threadfin shad). In Clark Lake, young-of-year (Austin and Hurley 1989), which are zooplanktiv- bluegills occurred in the limnetic zone before— orous (Ellison 1984; O'Brien et al. 1984), catc hdurint ono f t after—pear go bu k abundanc youngf eo - adult white crappie unir spe t effort, estimated with of-year threadfin shad, thereby reducing the po- trap nets during October 1988, was about three tentia competitior fo l n between these speciesn I . times higher in Stonelick Lake than in Clark Lake Stonelick Lake, however, bluegills spawned dur- (Austi Hurled nan y 1989). Thus, planktivory yb througy ingMa h Augustpeae th kd abundanc,an e young-of-year threadfin shayoung-of-yead dan r of young-of-year bluegills occurred before and bluegills, coupled with planktivor resideny yb t during the peak abundance of young-of-year adult white crappies sufficiens wa , causo t t e eth threadfin shad. Thus, competition between young- zooplankton decline in Stonelick Lake. of-year threadfin shad and bluegills was likely. The hypothesis that young-of-year threadfin late-summee Th r peak abundanc young-off eo - shad contributed to reduced zooplankton abun- year threadfin shad in Clark and Stonelick lakes danc Stonelicen i k Lak supportees i analogouy db s could have been due to several factors; for ex- studies with gizzard shad. In Kokosing Lake, Ohio, ample, spawning could have been delayey b d zooplankton density during the past 4 years typ- stocking stress, drought (which reduced water lev- ically decreased to near zero within 2 weeks of els during 1988) r late-summeo , r maturatiof no peak young-of-year gizzard shad density (DeVries young-of-year threadfin sha documentes d(a y db 1989). To determine whether young-of-year giz- Heidinge Imboded ran n 1974) abilite .Th preyo t - zard shad were responsibl declinee f th o r e efo ,on dict the time of spawning by threadfin shad after us (DeVries 1989) manipulated fish in 2-m3 en- the introducee yar criticas di determinino lt e gth closures (~ 19 fish/m3) and found that gizzard shad species' valu preys ea spawninf ;i delayedgs i - in , reduced macrozooplankton density from 700 to terspecific competition among young-of-year fish- less than 10 animals/L withi weeksn2 declina , e es can be minimized. Whether this late spawning similar in magnitude to that observed in Stonelick by threadfin shad will be consistent requires ad- Lake. In field studies at other lakes, zooplankton ditional research. declines have also been documented after thread- Because zooplankton remained abundant and gizzarfir no d shad introductions (VonGelderd nan densities were similar across years in Clark Lake, Mitchell 1975; Prophet 1982, 1985, 1988; Ziebell competition with threadfin shad (either larvae or et al. 1986); however, none of those studies mon- adults) probably was not responsible for the re- itored densities of young-of-year fish. Thus, the duced abundanc offshorf eo e young-of-year blue- exten whico t h zooplanktivor young-of-yeay yb r gill during 1988. Further, abundanc young-off eo - fish was related to zooplankton declines cannot be year threadfi t pean no Clarshan k i d ddi k Lake determined previoun I . s work co-occurrence th , e until after bluegill moved littorae sha th do t l zone. of young-of-year gizzar threadfir do e n th sha d dan It is possible that predation by adult threadfin shad midsummer declin zooplanktof eo bees nha n not- reduced young-of-year bluegill densities between (Cramed e Marzold an r f 1970; Johnson 1970; 1987 and 1988. However, even though threadfin Mayhew 1977; Kashuba and Matthews 1984; Kis- shad may be capable of piscivory (Kimsey 1958; sick 1988). These suggestive field data comn i , - alse se o Dendy exampln 194a r 6fo piscivorf eo y bination with our enclosure experiment, support by gizzar dHeidingee shadse t ;bu - rre 198a r 3fo hypothesie th s that predatio young-of-yeay nb r view of difficulties associated with detecting such threadfin shad contributed to reduced zooplank- piscivory), fish were not found in stomachs of ton densities in Stonelick Lake. threadfin shad from either lake during 1988 (N = 41 adult threadfin shad stomachs examined). Al- Threadfin Shad-Bluegill Interactions ternatively, the 1988 drought that lowered Clark Abundance of young-of-year fishes.— Spawning Lak abouy edurinb m 1 tnestin e gth g seasoy nma by threadfin shad peaked during Augus Clarn i t k have disrupted bluegill reproduction (see review and Stonelick lakes. This contrasts with the spring in Ploskey 1986). spawning documente r threadfidfo gizzard nan d Young-of-year threadfin shad, though their shad in other systems (Baglin and Kilambi 1968; abundance peake latn di e summer, co-occurret da Mayhew 1977; Barger and Kilambi 1980; Van Den low densities with limnetic young-of-year bluegills Avyl Wilsod ean n 1980; Downe Toetd yan z 1983; during May through September in Clark Lake. Tisa et al. 1987; Willis 1987; but see Santucci When both species co-occurred in the limnetic 378 DEVRIES ET AL.

zone, the onle yat y limnetic zooplankton; how- pet r limnetifo e c zooplankton. Diet f youno s g ever, diet overlap values were typically <0.50. bluegills and gizzard shad or threadfin shad rarely Once blue gills moved inshore, the potential for have been quantified, and interpretation of pub- competition with threadfin shad declined greatly. lished results remains tenuous. Most investigators Diets of bluegills collected from the littoral zone agree that first-feeding gizzard shad and bluegills did not change between 1987 and 1988 in Clark select copepod nauplii (Mayhew 1977; Mallit ne Lake l pre;al y types (littoral, limnetic cyclod an , - al. 1987; Kissick 1988); consequently, these spe- poid copepods) were eaten. Though collected in- cies could compete if they co-occurred as larvae. shore, bluegills apparently move enougr dfa h off- As young-of-year threadfin shad grew in our lakes, shor consumo et e some limnetic prey thet e ,bu y at they preferred larger prey such as Diaphanosoma enough littoral pre reducyo t e overlap with thread- leuchtenbergianum. This observation conflicts with fin shad, which continue feeo dt d entirel limn yo - published results that, as gizzard and threadfin netic prey. shad grow, they fee progressiveln do y smaller prey In Stonelick Lake, abundance of limnetic young- such as rotifers and Bosmina spp. (Barger and Ki- of-year bluegills befor afted introductioe ean th r n lamb Avyln i 1980Wilsod De ean n ;Va n 1980). of threadfin shad did not differ. Several peaks oc- However, without dat zooplankton ao n availabil- curred during both years. Fish fro protractee mth d itycannoe w , t evaluat pree eth y preferencef o s spawning seaso 198f no 7 continue migrato dt o et shad of either species in these studies. For ex- the littoral zone, as evidenced by their increasing ample, if zooplankton abundance declined, as in inshore abundance through summer 1988n .I , fish Stonelick Lak Augus n edocumentei s a d tan n di from the early-June peak migrated to the littoral other lakes containing gizzard or threadfin shad, zone during July; however, fish from the August both specie f shaso d woul forcee db feeo dt n do peak never appeared inshore. These August fish smaller prey items as they grew. Under these con- were lost to our offshore gear 2 weeks after then- ditions, shad might simpl consumine yb g avail- peak abundanc werd ean e never collectee th n di able zooplankton rather than actively selecting littoral zone, which suggests poor survival of the smaller prey. Several studies, including ours, have limnetic life stage. As suggested earlier, predation documented selectio Diaphanosomaf no sppy .b by adult threadfin shad probabl t responno s y-wa larval fish (Va Avyln Wilsond De ean n 1980; Mal- sible. Reduced densities of all zooplankton in Au- lin et al. 1987), but this is certainly not a universal gust, coupled with moderately high diet overlap finding (Crame Marzold ran f 1970). Consequent- between young-of-year bluegills and threadfin shad ly, although competition between young-of-year (range, 0.45-0.64) havy e,ma reduced bluegill sur- bluegills and young-of-year threadfin shad may vival and recruitment through exploitative com- occur (particularly during August in Stonelick petition with threadfin shad. Similar results were Lake) outcome th , sucf eo h interaction laka n sei obtained in a pond experiment where young-of- ultimately depends on abundance and species year shad (both gizzar threadfid dan n shad- re ) compositio zooplanktoe th f no n communitd yan duced the abundance of young-of-year white crap- relative onth e spawning predatoe timeth f o s r pies (Gues alt te . 1990). fishes. As demonstrated by our results, these fac- Diet overlap.—Diets f bluegillo s collecte- din tors vary among lakes and years, making gener- shor botn ei h lakes included littoral prey; thus alization difficult. overlap with threadfin shad was reduced once bluegills became littoral. In Clark Lake, the pro- Complex Effects on Young-of-Year portio littoraf no limnetid lan c prey consumey db Largemouth Bass bluegills collected in the littoral zone did not differ Because young-of-year largemouth bass re- across years. In Stonelick Lake during 1987, blue- mained in the littoral zone and fed primarily on gills collected in the littoral zone fed on littoral littoral prey in both lakes, their diets did not over- limnetid an c prey, apparently movin enougr gfa h lap with thos threadfif eo n shad. Furthermore- ,ow offshor consumo t e e limnetic prey. Howevern i , ing to this spatial segregation, young-of-year large- 1988 limnetic prey formed an extremely small mout t consumhno bas d di s e young-of-year component of the bluegill diet; reduced zooplank- threadfin shad. Thus apparene ,th t effec youngf o t - ton abundance after August 1 may have contrib- of-year threadfin shad on young-of-year large- uted to this. mouth bass in Stonelick Lake was complex and Few published data indicate whether or not unexpected. In Clark Lake, largemouth bass young-of-year threadfin shad and bluegills com- spawned several weeks late 198n ri 8 tha 1987n i ; THREADFIN SHAD EFFECTS ON YOUNG OF YEAR 379

consequently, when juvenile bluegills move- din always the primary factor regulating community shore, they were too large for largemouth bass to structur Clart a s ek(a Lake). Determinatioe th f no consume. In 1988, however, largemouth bass factors responsible for influencing the relative im- compensated by eating other foods (primarily co- portanc interactionf eo s among larvae represents rixids), so prey biomass in their stomachs did not criticaa l step toward successful managemenf o t differ across years Stonelicn .I k Lake during 1987, inland lakes. small fish (primarily centrarchids) wer emajoa r component of largemouth bass diets, in part be- Acknowledgments continuae causth f eo l recruitmen f young-ofo t - year bluegills inshore 1988n I . , juvenile bluegills This work would not have been possible with- did not recruit to the littoral zone after mid-July; out the cooperation of M. Austin, S. Hurley, and also, young-of-year largemouth bass were ex- D. B. Apgear of the Ohio Department of Natural tremely abundant in early summer. This high den- Resource . BuynaG d otherKend e san k an th f -so sity of young-of-year largemouth bass, coupled tucky Departmen Naturaf to l Resources thane .W k with poor recruitment of juvenile bluegill pres sa y J. Ballinger, P. Crane, D. Gleason, C. Habicht, L. (after mid-August), likely reduced largemouth bass Harper, H. Irvin, M. Knierim, E. Lewis, C. Mal- growth in 1988 compared with 1987. When young- lison, L. Ryan, and J. Zablotny for their help in of-year largemouth bass densities were reduced, the field and laboratory; E. Lewis, in particular, such that they were similar across years (after mid- counted more zooplankton samples and looked at August), growth rates during 1988 continueo dt more fish guts than seems humanly possible. be lower than during 1987. Though young-of-year Helpful comments were provided on a previous largemout hlittoran baso d sfe l invertebrates, they draf thif o t s manuscrip . ChessonL . . P M y . b tJ , could not compensate for the lack of fish in their Dettmers . DrennerW . R ,. Lazzaro . X , M . W , diets as fish did in Clark Lake, perhaps because . WahlMastersH . Mills. Rice. D .L A . d . E , J ,an , abundant young-of-year largemouth bass reduced This work was funded in part by National Science littoral invertebrate density. Without estimatef so Foundation grants NSF BSR-8705518 to R. A. macroinvertebrate densities from Clard kan Stein and NSF BSR-8715730 to G. G. Mittelbach, Stonelick unabl e lakesar e teso e,w t t this hypoth- and by Federal Aid in Fish Restoration Project esis. F-57-R Steiawarde. administereA d . nan R o dt d Thus, interactions between limnetic young-of- throug Ohie hth o Divisio Wildlifef no . year threadfin sha bluegilld dan havy seproma a - nounced negative effect on young-of-year large- References mouth bass growt thehf i y lea reducedo t d survival Adams, S. M., and D. L. DeAngelis. 1987. Indirect of young-of-year bluegills in the limnetic zone and effects of early bass-shad interactions on predator then to reduced recruitment of bluegills to the lit- population structur dynamicsfood b ean d we . Pages toral zone. Additionally, slower growth may re- Kerfoo. 103-11Sih. C A . ,d editorsW an t7n i . Pre- duce overwinter survival of young-of-year large- dation: direct and indirect impacts on aquatic com- mouth bas overwintef si r survival depend bodn so y munities. Universit Englandyw PresNe f so , Han- overHampshirew ,Ne . size and fat reserves (Adams et al. 1982a, 1982b; Adams, S. M., R. B. McLean, and M. M. Huffman. reviewed in Adams and DeAngelis 1987). As a 1982a. Structuring of a predator population through consequence, the very management practice in- temperature-mediated effects on prey availability. tende enhanco dt fishere eth adulr yfo t piscivores Canadian Journal of Fisheries and Aquatic Sciences may reduce surviva e targeth f to l species- Al . 39:1175-1184. though these negative effects are not direct (unlike Adams, S. M., R. B. McLean, and J. A. Parrotta. 1982b. Energy partitionin largemoutn gi h bass under con- positive th e effect increasef o s d prey availability), ditions of seasonally fluctuating prey availability. they could have substantial consequences over Transactions of the American Fisheries Society 111: several year sucf so h management manipulation. 549-558. Indirect effects, mediated through other species . HurleyT Austin . S d . R.. M an , 1989. Evaluatiof no or even through other trophic levels, thus can de- a threadfin shad introduction on crappie growth in termine the ultimate outcome of any manipula- an Ohio lake(s). Ohio Department of Natural Re- tion. Our results support the hypothesis that in- sources, FederaFisn i hd RestorationAi l , Annual Performance Report, Project F-29-R-28, Study 21, teractions involving young-of-year fishe havn sca e Columbus, Ohio. dramatic consequences for sport fishes (as at Baglin . KilambiV . E.. R ,R , Jr.d . an , 1968. Maturity Stonelick Lake) that ,bu t these interaction noe star spawnind an g periodicit gizzare th f yo d shad, Doro- 380 DEVRIES. ETAL

soma cepedianum, (LeSueur) Beaven i , r Reservoir. Heidinger . 1983C . ,R . Life histor gizzarf yo d shad dan Arkansas Academ Sciencf yo e 22:38-43. threadfin shad as it relates to the ecology of small Barger, L. E., and R. V. Kilambi. 1980. Feeding ecol- lakes fisheries. Pages 1-18 in D. Bonneau and G. ogy of larval shad, Dorosoma, in Beaver reservoir, Radonski, editors. Pros and cons of shad. Iowa Arkansas. Pages 136-14. FuimanA . L n 5i , editor. Conservation Commission, Des Moines. Proceedings of the Fourth Annual Larval Fish Con- Heidinger, R., and F. Imboden. 1974. Reproductive ference. U.S. Fis Wildlifd han e Service Arborn ,An , potential of young-of-the-year threadfin shad (Dor- Michigan. osoma petenense) southern i n Illinois lakes. Trans- Beard, T. D. 1982. Population dynamics of young-of- action Illinoie th f so s State Academ Sciencf yo : e67 the year bluegill. Wisconsin Department of Natural 397^*01. Resources Technical Bulletin 127. Johnson . 1970E . ,J . Age, growth populatiod ,an - ndy Buynak, G. L., B. T. Kinman, and R. V. Jackson. 1989. namics of threadfin shad, Dorosoma petenense Purse seining to capture large numbers of adult (Gunther), in central Arizona reservoirs. Transac- threadfin shad. North American Journal of Fish- Americae tionth f so n Fisheries Society 99:739-753. eries Management 9:121-123. Kashuba, S. A., and W. J. Matthews. 1984. Physical Chesson, J. 1978. Measuring preference in selective condition of larval shad during spring-summer in a predation. Ecology 59:211-215. southwestern reservoir. Transactions of the Amer- Chesson . ,J 1983 estimatioe Th . analysid nan preff so - ican Fisheries Society 113:199-204. relationshierencs it d ean foraginpo t g models. Ecol- Keast,A. 1980. Food and feeding relationships of young ogy 64:1297-1304. firse th fis t n weekhi s afte beginnine th r exogef go - Cramer, J. D., and G. R. Marzolf. 1970. Selective pre- nous feedin Lakn gi e Opinicon, Ontario. Environ- dation on zooplankton by gizzard shad. Transac- mental Biolog Fishef yo s 5:305-314. Americae tionth f so n Fisheries Society 99:320-332. Kimsey, J. B. 1958. Possible effects of introducing Gushing, D. H. 1975. Marine ecology and fisheries. threadfin shad (Dorosoma petenense) into the Sac- Cambridge University Press, Cambridge, UK. ramento-San Joaquin Delta. California Depart- Dendy, J. S. 1946. Food of several species of fish, ment of Fish and Game, Inland Fisheries Admin- Norris Reservoir, Tennessee. Journa Tennessef lo e istrative Report 58-16, Sacramento. Academy of Science 21:105-127. Kirk, J. P. 1984. Competitive influences of gizzard DeVries . 1989 R influence . D , Th open-wate.n a f eo r shad introduction balancen so d largemouth bass- planktivore on reservoir communities: the impor- bluegill populations. Doctoral dissertation. Auburn tanc trophic-levef eo l interaction ontogenetid san c University, Auburn, Alabama. niche shifts. Doctoral dissertation. Ohio State Uni- Kirk, J. P., and W. D. Davies. 1987. Competitive in- versity, Columbus. fluence f gizzaro s d sha largemoutn do h basd san . SteinDeVriesA . R . . d R.1990D ,an , . Manipulating bluegill in small impoundments. Proceedings of the sha enhanco dt e sport fisherie Nortn i s h America: Annual Conference Southeastern Association of Fish an assessment. North American Journal of Fisher- and Wildlife Agencies 39(1985):! 16-124. ies Management 10:209-223. Kissick . 1988A . L , . Early life history gizzare ofth d DeVries, D.R., and R. A. Stein. 1991. Comparing three sha Actodn i n Lake, Ohio: feeding ecolog drifd yan t zooplankton samplers: a taxon-specific assessment. of stream-spawned larvae. Master's thesis. Miami Journal of Plankton Research 13:53-59. University, Oxford, Ohio. Downey, P., and D. Toetz. 1983. Distribution of larval Lasker, R. 1975. Field criteria for survival of anchovy gizzard shad (Dorosoma cepedianum) in Lake Carl larvae: the relation between inshore chlorophyll Blackwell, Oklahoma. American Midland Natural- maximum layer successfud san l first feeding. U.S. ist 109:23-33. National Marine Fisheries Service Fishery Bulletin Ellison . 1984G . D , . Trophic dynamic Nebraska f so a 73:453-462. black crappie and white crappie population. North Mallin . Birchfield J . A. . . Warren-HicksM L , W d an , . American Journa Fisherief lo s Management 4:355- 1987. Food habits and diet overlap of larval Le- 364. pomis spp. and gizzard shad in a Piedmont reser- Gardner, M. B. 1981. Effects of turbidity on feeding voir. Proceedings of the Annual Conference South- rate selectivitd san bluegillf yo . Transactione th f so eastern Associatio Fisf Wildlifnd o han e Agencies American Fisheries Society 110:446-450. 39(1985): 146-155. Gilliam . 1982F . J , . Foraging under mortality risn ki Mayhew . 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