Transactions of the American fisheries Society 125:291-299. 1996 #? Copyrigh e Americath y b t n Fisheries Society 1996

Age Structur Yellowstone-Sakakawee th f eo a Paddlefish Stock, 1963-1993, in Relation to Reservoir History DENNI . SCARNECCHIL S A Department Pishof and Wildlife Resources, Universitv Idahoof ' Moscow. Idaho 83844-II'36, USA PHILLI . STEWARPA T Montana Department of Fish, Wildlife and Parks Rural Route I Box 2004, Miles City, Montana 59301,USA GREG J. POWER North Dakota Game and Fish Department 100 North Bismarck Expressway. Bismarck. North Dakota 58501, USA

Abstract.—Current historicad an structure lag e informatio Yellowstone-Sakakawee th n no a stock of paddlcfish Polyodon spathula is reviewed in relation to the completion of Garrison Dam in 1953 ansubsequene dth t fillin f Lako g e Sakakawea a 156,000-h, a impoundmen Missoure th n o t i River. Paddlefish abundance increased greatly afte closure th r f Garrisoeo firsne th Dam t d largan , e group of paddlefish (nearly all males) migrated up the Ycllowstone River to Intake. Montana, in 1962- e mid-1970sth 1963 y B . , afte graduae th r l reservoie fillinth f o g r (1954-1966). both femaled an s males had fully recruited to the Intake fishery, and more females were harvested than males. By the 1980s, older females predominated in the harvest. Based on age determination in 1991-1993, the slock has continued to age, from a mean of 10.3 years in 1964-1965 to 14.8 in 1974. 20.3 in 1985 23.d 1992n an i ,5 . In 1993. however, mean age f paddlefisso t Intakha e decrease year2 y db s for males and 3.3 years for females. In 1991 and 1992, males from Intake were characterized by bimodal age distributions with ages ranging from 7 to 40 (means, 18.4 and 17.8, respectively); females demonstrated unimodal age distribution 2 (means4 o ranged e t fro s0 an ag m ,1 n i 25.d 5 and 26.1). Males commonly matured at age 9, but females almost never matured before age 15. e oldesTh t paddlefish encountere a 14-k s gwa d male caugh n 198 i testimated year5 5an 5 e sb o dt old. Although substantial recruitment has occurred within the past decade (as indicated by re- cruitment of 9-11-year-old males to the fishery in 1991-1993) and reproduction appears to have occurred in 1991 and 1993 (based upon counts of young-of-lhe-year in Lake Sakakawea), the age structure suggests that recruitment may be less in recent years than in the years soon after the reservoi closes wa filledrd dan conservativA . e harves calles i t r unti cleas i dfo t i l r that reproduction adequats i sustaio et e stoc thd nth ean k fishery.

e Yellowstone-SakakaweTh a stoc f paddleo k - Sakakawea. Since 1962 annuae th , l harves f padto - fish Polyodon spathula supports important recre- dlefish at Intake has typically ranged between ational snag fisherie eastern i s n Montan westd aan - 1,00 d 5,00an 0 0 fish. North Dakota's paddlefish Nortn er h Dakota (Scarnecchi t ale a. 1995). Fish fishery bega n 1977i n d occuran , s mainle th t ya of this stock rear in Lake Sakakawea, a main-stem confluence of the Missouri and Yellowstone rivers impoundment on the Missouri River. Mature fish (the Confluence). Harvest has increased substan- become vulnerable to harvest during spawning mi- tially since the 1980s; total harvest in 1993 was gration Missoure th p su i Rivetailwatere th o rt f so more than 2,000 fish. Fort Peck Dam and up the Yellowstone River to During the years of these fisheries, the age struc- Intake, a low-head diversion dam 27 km downriver ture of the stock has been monitored sporadically from Glendive, Montana (Figure 1). through collection and interpretation of dentaries This stock, in contrast with most other paddle- (lower jaw bones), the most commonly used meth- fish slocks throughout the species' range (Carlson od of age determination for this species (Adams and Bonislawsky 1981; Gengerke 1986 s eviha )- 1931, 1942) attempo N . s beetha n mad relato t e e dently increased in numbers in the past 40 years, long-term age structure changes to the changing significanA t e stocfisherth r k fo yfirs t developed habitat feature Lakn si e Sakakawea objectivee Th . s at Intake in 1962 (Robinson 1966), 9 years after of this paper are to review past efforts at age de- closure th f Garriso e195o n i 3m createnDa d Lake termination structure ag , stocrepore e th th f kn eo o t 291 292 SCARNECCHI. AL T AE

MONTANA NORTH DAKOTA

Confluenc Yellowstonf eo Missourd ean i Willlston, Dredge Cut Fort sa t Peck Missouri River

01020 40 80 120 160km

WYOMING FIGURE I.—Lower Yellowstone River and Lake Sakakawea, Montana and North Dakota. over 1991-1993 relatd an , e change e strucag n i -s above sea level, an area of 156,000 ha, and a tur o relevant e t environmental conditione th n i s storage capacit f moro y e tha 0 billio3 n n cubic reservoir. meters. High rates of sediment deposition (an av- erage of 32 million cubic meters per year), mainly Study Site froe Yellowstonmth e River, resul n shallowi t , The lower Yellowstone River extends approx- turbid wateuppee th n i rr portio reservoie th f no r imately 630 km from the mouth of the Bighorn (Powe . 1994)al t e r . n Aftei m r da closur e th f eo River to its confluence with the Missouri River, 1953 reservoie th , r filled gradually from 195o 4t approximatel southwesm k 0 4 y f Willistono t , 1966 t reacheI . d full poo n 196 i ld remaine 7an d North Dakota (Figure 1). Haddix and Estes (1976) full until 1976. From 1977 to 1988 the reservoir and Graha t male . (1979) reviewe physicale dth , level underwent periodic fluctuations; in 1988, it chemical, and biological characteristics of the dropped well below full pooremained an l w lo d lower Yellowstone River. Although the main stem until mid-1993. Heavy precipitation throughout is unregulated, two low-head irrigation diversion e Greath t Plain n 199 i sd retentio 3an f wateo n r dams impede fish migration t Cartersvillsa e (near reservoire inth avoio st d downriver floodin- gre Forsyth) and at Intake (near Glendive). After the sulted in a rapid rise in the reservoir level in mid- Yellowstone River's confluence wit Missoure hth i 1993 (Figure 2). River, the Missouri River flows freely until it empties into Lake Sakakawea, a distance of from Review of Past Studies: 1963-1989 24 to 80 km, depending on Lake Sakakawea's Stock expansion anil reservoir filling in the 1950s level. Lake Sakakawea, the largest of the Mis- and 1960s.—Robinson (1966) sampled paddlefish souri River main-stem reservoirs, is 320 km long for dentaries at Intake during the May-June fishing and has a maximum surface elevation of 565.4 m season f 196s o 1965d 4an , soon afte firse th rt large PADDLBHSH AGE STRUCTURE 293

570

560 -

550 -

540 -

Filling Full Variable Dropping 1954-1966 1967-1976 1977-1988 1989-1993 530 -

520

510 4 9 0 9 6 8 2 8 8 7 4 7 0 7 6 6 2 6 8 5 54 Year19_ FIGURH 2.—Elevation (meters above mea a levelnse f Lako ) e Sakakawea, 1953-1993.

ruf paddlefiso n e Yellowstonth p u h e Riven i r ple of 478 females ranged in age from 15 to 20 1962. More than 90% of these fish were less than years (mean, 18), with age se mos d 118th an 7 t 15 years old (Figure 3a). The three most common common (Figure 3b). Females sample y Rehdb - ages were 9, 10, and 11 years, which corresponded winkel (1978) evidently first recruited to the fish- to brood years 1954-1956, the period immediately ery at age 15 and did not fully recruit until per- afte closure th r f Garrisoeo (Figurm nDa . More2) e haps age 17 or 18. These females were evidently than 97% of the fish harvested were males. Evi- the first female recruits produced from the large dently the males of these strong year-classes ma- postimpoundment year-classe year0 s2 1o 5t s ear- tured earlier than the females and recruited to the lier (1954-1958). Whereas morf o e tha% 90 n fishery at a younger age. The hypothesis that the paddlefish creeled in 1964-1965 had been males, population increased is consistent with paddlefish only 56% of the fish creeled in 1973 were males commercial catch statistics from Lake Sakakawea. (Stewart 1994). By 1974, females harvested at Power et al. (1994) reported that 21 paddlefish Intake bega o outnumbet n re pre malesth -d an , caught wit hreservoie netth n i s 195n i r 4 weighed dominance of females persisted until 1993 (Stew- an average of only 65 grams and that 13 paddlefish art 1994; Figur. e4) caught in 1955 averaged only 87 grams. These fish Predominance large,of older femalesa and would have been young-of-the-year. The first sig- dropping reservoir level in the 1980s.—Sex ratios nificant catche e reservoith n si r occurre n 196di 1 (Figurd weighan ) e4 t distribution f paddlefiso s h when the mean weight of 779 paddlefish caught indicated that large, older females were the pre- was 3.5 kg. dominan x contributinse t e catcth t Intakha o gt e Full recruitment bothof full a sexes res-and throughout the 1980s. Mean weight of female pad- ervoir1970s.—e th n i Rehwinkel (1978) reported dlefis t a Intakh e rose slowl t consistentlbu y y that 503 male paddlefish sampled in 1974 ranged throughou e decad th t1 pad 22 e- e (FigurTh . 5) e in age from 9 to 26 years (mean, 13), with ages dlefish dentaries aged by Stewart (1987) were sub- e mosd 12th 1an 1 t common (Figure 3b) samA . - sequently recut and reaged in 1992 with more ad- 294 SCARNECCHI. AL T AE

0.30- 1964 and 1965

Both sexes (nearly all males) 0.20-

Age(Yr) FIGURE 3.—Age distribution of paddlefish in (a) 1964 and 1965 (N = 343 fish; Robinson 1966), (b) 1974 (N = 503 males, N = 478 females; Rehwinkel 1978), and (c) 1985 (N = 94 males, N = 127 females) for recut and reaged samples originally aged by Stewart (1987). Smoothed curves were generated by the spline method available in PROC PLOT (SAS Institute 1987). vanced dentary sectionin readind gan g equipment. Recent Investigations: 1991-1993 Ninety-four male years9 range 2 froe o st ag m 9 n di Between 1991 and 1993, dentaries were col- (mean, 17; with one fish aged 55); the most com- lected from 4,448 paddlefish, 93% from Intake and mon ages wer , years115 e9 2 , d 21.an , Females fro % e Confluenc7 mth d nearban e y sites. Den- (127 year0 3 ) o ranget se fro 5 (meanag m1 n di , taries were removed with diagonal pliers, and ex- 23; with one fish at 37); the most common ages cess skipeeles nwa d off. Cleanin sectionind gan g were 21 and 22 (Figure 3c). These female-pre- of dentaries followed, with minor changes, pro- dominated catches occurred when reservoir levels cedures outline Reey db d (1989). Dentaries were were generally slightly below ful lmid e pooth n -i l sectioned wit diamond-edgeha d blad Bueha n eo - 1980 considerabld san y below ful llat e pooth e n i l ler Isomet low-speed saw. Two sections 0.635 mm 1980s (Figur. e2) thick were obtaine posteriom m poine 0 th 1 d o tt r PADDLEFISH AGR STRUCTURH 295

3 9 0 9 7 8 4 8 1 8 8 7 5 7 2 7 9 6 6 6 3 6

n 4.—Percentag f femaleo e paddlelis Intakn i h e catch. 1963-1993.

of greatest curvature (Reed 1989: Reed et al. In 1993, for the first time in nearly 20 years, 1992). Sections to be aged were immersed in gly- the harvest at Intake was predominantly males. cerine and interpreted for age by counting annua e structurag l e Th e also differed from thos 199n ei 1 bands with the aid of a Biosonics Optical Pattern and 1992. Males ranged in age from 6 to 35 years, Recognition System (OPRS). Samples were inter- (mean, 15.8). two years younger than in 1992. Fe- preted without knowledge of the si/e or sex of the male 8 year3 s e rangeo frot s ag m9 (mean n i d , fish, except insofar as smaller fish tended to have 22.8), 3.3 years younger than in 1992 (Figure 6c). smaller diameter sections. Annuli were counted Mean weight of aged males was the same in 1992 alon e lonth g e gmesia th axi f o sl arme valiAg . - n 199i s 3a (1 ) (1.I 5kg 1. 5 kg)t meabu , n weights dation was not possible because no paddlefish were of aged females dropped by 0.7 kg in 1993 (26.5 of known age. kg) from 1992 (27.2 kg).

Results North Dakota Intake Although there were fewer samples from North In 1991, male paddlefish ranged in age from 7 Dakota than from Intake, results from their anal- year0 4 o t s (mean, 18.4). Females ranged from 14 ysis wer generan ei l agreement with results from to 42 years (mean, 25.5). Although 205 of the 721 Intake (except for 1993). In 1991, 74 males ranged males in 1991 were between age 7 and age 13, the in age from 9 to 37 years (mean. 21): 54 females youngest female , whics 14 wer e h eag indicate da rangee fro ag m 3 (meann 3 di 1o t 7 , 24) n 1992I . . considerably t maturit a oldee female e th ag r yfo s 19 males ranged in age from 9 to 33 years (mean, (and hence delayed migration pattern and delayed 22) female2 2 : s ranged fro m(mean4 3 1o 9t , 24). vulnerabilit o harvest)t y . Age-frequency distri- In 1993,48 males ranged from 9 to 29 years (mean, butions for the sexes also differed: males had a 18): 72 females ranged from 16 to 35 (mean, 25). bimodal distribution wit a hmino r pea t aboua k t Mean age of both males and females in North Da- highea d an r21e 9 peae ag , whereat ag ka s females 2 yearkot 2. n 199i as s highe3wa r tha t Intaka n e had a unimodal distribution with the peak at age and was similar to the mean ages recorded at Intake (Figur6 2 e 6a). in 199d 1992 an 1s wit e A Intak. th h e samples, e distributionAg n 199i s 2 were simila thoso t r e females did not recruit until 6-10 years after in 1991. Males ranged in age from 7 to 33 years w fisfe malesh d wer d enougan ,ol e o havt h e (mean, 17.8), or 0.6 year younger than in 1991. hatched befor e 195eth 3 closur f Garrisoeo n Dam. Females range year0 4 d o t fros 0 (meanm1 . 26.1). or 0.6 year older than in 1991. Although 79 of the Age Structure in Relation to Stage of 219 males were aged 7-13, only one of the 471 Reservoir females was under age 14. As in 1991, males had femalee th f Nearlo s % capturey60 199n di d 1an a bimoda e distributioag l n wit e highesth h t peak 1992 were hatche yearn di s whe reservoie nth s rwa e 21aag ,t whereas female a unimoda d ha s l peak filling (1954-1966: Figure 2: Table I). In contrast, (Figur7 2 e aag et 6b). in 1993, lower mean ages and mean weights of 296 SCARNECCHI. AL T AE

0.0 <20 22.5 27.5 32.5 37.5 42.5 47.5 52.5 57,5 62.5 67.5 72.5 77.5 82.5 87.0 5>9

FIGURE 5.—Approximated weight distribution f femalso e paddlefish harveste t Intakda 3-yean ei r intervals, 1981- 1992.

females indicated that only about 24% of those dlefish commonly reachin year5 g2 somd san s ea fish were produced during these years. A high per- old as 30. In more southerly and more heavily centage of males caught in 1991-1993 derived exploited populations, maximum age observed is from brood years when the reservoir was full evidently lower. In Lake Ponchartrain, Louisiana, (1967-1976), and by 1993, young males from the Ree t alde . (1992) found paddlefise ag h o onlt p yu year-classes 1977-1988 constituted half of all 14 . above Nonth f eo stocke ag s exhibid ol e th t males aged. Yellowstone-Sakakawee th f o a stock whicn ,i h fish exceedin e abundanar e year5 fisd ag g2 han f t o s Discussion t uncommonexceedinno e ar e oldes0 g3 Th . t fish StructureAge Relative Otherto Localities found thus far, a 14-kg male caught in 1985 and e Yellowstone-SakakaweTh a paddlefish stock estimated to be 55 years old, is, to our knowledge, consiste f oldeo d r (commonly 25-35-year-old), the oldest paddlefish reported anywhere. A few fish later-maturing fish (at least 9 years for males, 15 have exceeded age 40, even in the presence of years for females) than reported in most other lo- considerable annual harvest. cations. Gengerke (1978) reported that onle on y of 787 paddlefish in Iowa's portion of the Missis- Accuracy Determination ofAge sippi River was older than age 20; male fish of I ffisunderestimatedd e ageol ar h f so occurs a , s that stock matured as young as age 4, and females d whitfool r e sturgeon Acipenser transmontanus as young as age 6. In the Osage River, Missouri, (Rien and Beamesderfer 1994) and other fishes Purkett (1963 Russeld an ) l (1986) reported pad- (Beamish and McFarland 1987), 40-year-old pad- PADDLEFIS STRUCTURE HAG E 297

(a) 1991 Female

0.05

0.15 1992 Female

0.10

Age (Yr) FIGURE 6.—Age distribution of (a) 721 male and 975 female paddlefish sampled at Intake in 1991, (b) 219 male and 471 female paddlefis ) 1,14 1992(c n i h 2 femald 4 67 an ,mal d e ean paddlefis 1993n i h . Smoothed curves were generate spline th y edb method availabl PROn ei C PLOT (SAS Institute 1987).

dlefish may be more common than it appears, based on our aging technique. Under-aging of old- TABLE 1.—Percentages of male (M) and female (F) pad- er paddlefish is a distinct possibility because the dlefish caught at Intake, Montana, from 1991 to 1993, ac- outer annuli on fish 20 years and older are com- cording to their year-clas relatiod san reservoio nt r water monly spaced closely together. Althoug e valhag - levels: pre-1954 = before reservoir; 1954-1966 = reser- idation (Beamish and McFarland 1983) is an ob- voir filling; 1967-1976 = reservoir full; 1977-1988 = variable reservoir, full, or slightly below full. vious nee r thidfo s species t wili , l onl possible yb e in the near term through tagging fish of known Year-class group and sex ages, and then only for young recruits. Year Pre-1954 1954-1966 1967-1976 1977-1988 of catch M F M F M F M F Structure,Age Reservoir Level, Stockand Status 1991 <1 <| 18 59 51 40 31

Lake Sakakawea . f paddlefisMeao e nag t Intakha e the early years as they would relate to survival of increases ha d from 10.3 year 1964-196n si 5 (Rob- young-of-the-year paddlefish. During the early to inson 1966) to 14.8 in 1974 (Rehwinkel 1978), mid-1960s (the latter part of the filling period), a 20.3 in 1985, and 23.5 in 1992. Despite years of strong fishery for northern pike Esox lucius de- harvest femald ol , e paddlefish still constitut esiga - velope excellene resula th s da f o t t spawning con- nificant fraction of the harvest. The predominance ditions create y recentlb d y flooded vegetation. of old females hatched in the years of reservoir This fishery remained strong unti earle th l y 1970s. filling (1954-1966) and immediately thereafter in- Afte reservoie th r filledd ha r mora , e stable water dicate that these early years were often successful leved significanan l t shore erosion resultedy b , for paddlefish reproduction e resultinth d - an , gre 1979-1980 n stroni , g year-classe f walleyo s e cruits have supported a fishery for more than 30 Stizostedion vitreum sauged an r Stizostedion can- years. adense. A nationally renowned fishery existed for Although reproduction and recruitment are oc- these specie mid-1980e th n si s (Powe t alre . 1994). curring s evidencea , y young-of-the-yeab d n i r Natural reproductio f walleyno e wane s resera d - Lake Sakakawea in 1991-1993 (Fredericks 1994) voir water levels fell during the mid-1980s, which and by the presence of 7-14-year-old males in the lestockino dt f larggo e number f walleyesso - Al . 1993 harves structure t ag (Figur e th , e eindicate6) s though walleyes and saugers are known predators that recruitmen e les b recenn i sy ma t t years than of paddlefish in Lake Sakakawea (Mero 1992), the just afte reservoie th r s close wa filledd r e dan Th . effect f theso s e change predaton si r abundancn eo positive effect f trophio s c upsurg e yearth n si e paddlefis e unknownar h decadeso e lasth tw t n I . , immediately after reservoir constructio repron no - f Lako e uppemuc th d e f en ro hSakakawe s ha a duction and recruitment of fish stocks are well doc- become filled with silt, producing increasingly umented (Baranov 1966; Ostrofsk d Duthian y e shallow, turbid habitat. More information is need- 1978; Kimmel and Groeger 1986). In Lake Francis ed on factors affecting annual year-class strength Case (South Dakota), another Missouri River res- of paddlefish, and, in particular, on reservoir hab- ervoir, Gasaway (1970) reported that postim- itat condition resultine th d san g abundanc othef eo r poundment growth of 13 species of fish initially species. increased after impoundment but later decreased. The importance of the upper end of Lake Sak- Neel (1967) reported that from 1954-1958, phy- akawea and the Missouri River near the Conflu- toplankton densit Lakn i y e Sakakawea peaken di reproductioe encth o et recruitmend nan f pado t - 1956 secone th , d summer afteclosurem da r d an , dlefis alss hi o uncertain rapie .Th d refillin Lakf go e declined greatl 195n yi 1958d 7r femalan Fo . e pad- Sakakawea which occurre n 199di providy 3ma e dlefish that recruit to the fishery 15-20 years after information on the effects of reservoir aging and birth sucy an ,h upsurge effect- ev s e woulb t no d water level n paddlefiso s h reproductio- re d an n iden r manfo t y years afte e initiath r l strong year- cruitment. Until reservoir productivity and repro- classea decad d r an morso e e aftee effectth r s ductio d recruitmenan n f paddlefiso t e showar h n would have dissipate r shorter-livefo d d fishesn I . to be adequate to sustain the stock and fishery, addition, the gradual, 13-14-year filling of Lake conservative harvest regulations are warranted. Sakakawea may have resulted in more gradual tro- phic change filled sha that di ovef ni mucra h short- Acknowledgments r periode r thiFo .s reason entire th , e filling period We thank A. Whipple, Y. Lim, J. Bailey, J. Fred- (1954-1966 d perhapan ) s some years afterward ericks, and B. Chelgren for their contributions to could be viewed as the upsurge phase of the res- this study, and F. Ryckman, J. Congleton, M. Had- ervoir. Most of the large females that supported . GengerkT dixd an , r reviewinefo g e draftth f o s e paddlefisherth n 1991-199i y y havma 3e been paper. hatched during conditions of upsurge-related pro- ductivity that were not sustainable over the long References term. Also underestimatioy an , f ageno f eitheso r Adams . 1931A . L ,. Determinatio n fishesi e ag . f o n males or females would result in even higher per- Transactions of the Illinois State Academy of Sci- centage f oldeso r male femaled san s being hatched ence 23:219-226. durin earliee gth r year f Lako s e Sakakawea'- sex Adams . 1942A . e determinatioL , .Ag d ratf an no e growt n Polyodoni h spathula. e y meanb th f o s istence. growth rings of the otoliths and dentary bone. Little direct information exists, howevere th n o , American Midlands Naturalist 28:617-630. ecological condition Lakn i s e Sakakawea during Baranov . 1966V . I , . Biohydrochemical classificatiof no PADDLEFISH AGE STRUCTURE 299

the reservoir Europeae th n si n U.S.S.R. Pages 139- Ostrofsky, M. L., and H. C. Duthie. 1978. An approach . TyurinV . P 18 n 3i . editor e storagTh . e e laketh f so o modellint g productivit n reservoirsi y . Interna- U.S.S.R. and their importance for fishery. Bulletin tionale Vereinigung fiir thcoretisch d angeun e - e Statth ef o Scientific Research Institut f Lako e e wandte Limnologie Verhandlungen 20:1562-1567. and River Fisheries, volume 50. Israel Program for Power, G. J.. J. C. Hendrickson. J. D. Lee, and F. Ryck- Scientific Translations, Jerusalem. man. 1994. Missouri River system fishery refer- Beamish, R. J., and G. A. McFarland. 1983. The for- ence and operational management document. North gotten requiremen e validatioag r fo t n fisheriei n s Dakota Gam Fisd ean h Department, Repor , BisK) t- biology. Transactions of the American Fisheries So- marck. ciety 112:735-743. Purketl. C. A.. Jr. 1963. The paddlefish fishery of the Beamish, R. J., and G. A. McFarland. 1987. Current Osage River and the Lake of the Ozarks. Missouri. trenddeterminatioe ag n si n methodology. Pages 15- Transaction Americae th f so n Fisheries Societ: y92 42 I'M R. C. Summerfell and G. H. Hall, editors. Age 239-244. and growth of fish. Iowa State University, Ames. Reed, B. C. 1989. Paddlertsh investigations. Louisiana . BonislawskyS . P d Carlsonan , M. .. 1981D , e padTh .- Department of Wildlife and Fisheries. Project F- dlefish (Polyodon spathula) fisheries of the mid- 60(03). Baton Rouge. western United States. Fisheries 6(2): 17-22, 26-27. Reed, B. C., W. E. Kelso, and D. Alien Rutherford. Fredericks . P 1994 . J , . Distribution, abundanced an , 1992. Growth, fecundity, and mortality of paddle- feeding ecology of young-of-the-year paddlefish in fisn Louisianai h . Transaction f tho s e American upper Lake Sakakawea, North Dakota. Master's the- Fisheries Society 121:378-384. sis. Universit f Idahoyo , Moscow. Rehwinkel, B. J. 1978. The fishery for paddlefish at Gasaway . 1970R . C , . Change e fisth h n populatioi s n Intake, Montana during 1973 and 1974. Transac- in Lake Francis Case in South Dakota in the first tions of the American Fisheries Society 107:263- 16 years of impoundment. U.S. Bureau of Sport 268. Fisherie Wildlifd san e Technical Pape. 56 r . BeamesderferC . RienR . d A.T .an , . 1994. Accuracy Gengerke . 1978W . T , . Paddlefish investigations. Iowa and precision of while sturgeon age estimates from Conservation Commission, National Marine Fish- pectoral fin rays. Transactions of the American Fish- eries Service, Project 2-225-R, Segment 1-3, Final eries Society 123:255-265. Report s MoinesDe , . Robinson. J. W. 1966. Observations on the life history, Gengerke . 1986W . T ,. Distributio abundancd an n f o e movement harvesd paddlefishe an , th f o t , Polyodon paddlefish in the United States. Pages 22-35 in J. spathula, in Montana. Proceedings of the Montana . DillardG . Russell. GrahamR K . . T L . d , an ,editors . Academy of Sciences 26:33-44. The paddlefish: status, management and propaga- Russell. T. R. 1986. Biology and life history of the tion. American Fisheries Society, North Centra- Di l paddlefish—a review. Pages . DillardG 2-2. J n 0i , vision, Special Publication 7, Bethesda, Maryland. . Russell. GrahamR K . . T L d . an ,1986 e pad.Th - Graham . . PenkalF PetermanL . . J.P d R ,, an , . 1979. dlefish: status, managemen propagationd an t . Amer- Aquatic studiee Yellowstonth f o s e River. Report ican Fisheries Society. North Central Division. Spe- (REC-ERC-79-8) to the Bureau of Reclamation, cial Publication 7, Bethesda, Maryland. Upper Missouri Region, Billings, Montana. SAS Institute. 1987. S AS/GRAPH guid r personafo e l Haddix, M. H., and C. C. Estes. 1976. Lower Yellow- computers, versio edition6 n S InstituteSA . , Cary, stone River fishery study. Montana Department of North Carolina. Fish and Game, Final Report, Helena. Scarnecchia, D. L., P. A. Stewart. and G. J. Power. 1995. . GroegerKimmelW . A d . L.. B .an , 1986. Limnological Management plan for the paddlefish stocks in the and ecological changes associated with reservoir Yellowstone River, Upper Missouri River, and Lake agingn . PageVa . J . s M . 103-10 Hald E . an l G n 9i Sakakawea. Montana Departmen f Fisho t , Wildlife Den Avyle, editors. Reservoir fisheries manage- and Parks, Helena, and North Dakota Game and ment: strategies for the 80's. American Fisheries Fish Department, Bismarck. Society. Southern Division, Reservoir Committee, Stewart . 1987A . P , . Yellowstone River paddlefis- in h Bethesda, Maryland. vestigations. Montana Department of Fish. Wildlife, Mero, S. W. 1992. Food habits of walleye, sauger, and and Parks, Fisheries Division, Federal Aid in Sport their hybrids in Lake Sakakawea, North Dakota. Fish Restoration. F-30-R-23, Job Ha. Progress Re- North Dakota Game and Fish Department, Federal port. Helena. Ai Sporn di t Fish Restoration. Project F-2-R-38b ,Jo Stewart, P. A. 1994. Yellowstone River paddlefish in- 6, Final Report, Bismarck. vestigations. Montana Departmen f Fisho t , Wildlife Neel, J. K. 1967. Reservoir eulrophication and dystro- and Parks, Fisheries Division, Federal Aid in Sport phication following impoundment. Pages 322-332 Fish Restoration, Project F-46-R-7. Job IIIc, Prog- Reservoin i r fishery resources symposium. Ameri- ress Report, Helena. can Fisheries Society, Southern Division, Reservoir Received November 18, 1994 Committee, Bethesda, Maryland. Accepted Septembe . 19927 r 5