The Status of Nebraska Fishes in the Missouri River. 1. Paddlefish (Polyodontidae: Polyodon spathula)

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1 University of Nebrsk - Lincoln DigitlCommons@University of Nebrsk - Lincoln Trnsctions of the Nebrsk Acdemy of Sciences nd Affilited Societies Nebrsk Acdemy of Sciences 1993 The Sttus of Nebrsk Fishes in the Missouri River. 1. Pddlefish (Polyodontide: Polyodon spthul) Lrry W. Hesse Nebrsk Gme nd Prks Commission Gerld E. Mestl Nebrsk Gme nd Prks Commission Follow this nd dditionl works t: Prt of the Life Sciences Commons Hesse, Lrry W. nd Mestl, Gerld E., "The Sttus of Nebrsk Fishes in the Missouri River. 1. Pddlefish (Polyodontide: Polyodon spthul)" (1993). Trnsctions of the Nebrsk Acdemy of Sciences nd Affilited Societies This Article is brought to you for free nd open ccess by the Nebrsk Acdemy of Sciences t DigitlCommons@University of Nebrsk - Lincoln. It hs been ccepted for inclusion in Trnsctions of the Nebrsk Acdemy of Sciences nd Affilited Societies by n uthorized dministrtor of DigitlCommons@University of Nebrsk - Lincoln.

2 1993. Trnsctions of the Nebrsk Acdemy of Sciences, XX: THE STATUS OF NEBRASKA FISHES IN THE MISSOURI RIVER. 1. PADDLEFISH (POLYODONTIDAE:POLYODON SPATHULA) Lrry W. Hesse nd Gerld E. Mestl Nebrsk Gme nd Prks Commission P. O. Box 934, Norfolk, Nebrsk Federl Aid in Sport Fish Restortion, Dingell-Johnson Project F-75-R-I0 ABSTRACT The men lrvl pddlefish density ws 60 times higher in the upper unchnnelized section of the Missouri River in Nebrsk compred to the lower unchnnelized section, nd ws three times higher thn the chnnelized section's density. Within the upper unchnnelized section, 96.2% of the lrve were collected in the dischrge of two tributries, which lie in the lower one-third of the rech. Survivl from lrvl to young-of-the-yer stge (June through August) ws highest during 1991 due, in prt, to the recent drought. Reduced fluctution of river stges occurred s result of reduced runoff, which minimized the need to reduce dischrge to prevent flooding in the lower bsin. The men weight of pddlefish cptured during the 1991 sngging seson incresed from 6.89 kg in 1990 to 7.45 kg, while the men length incresed from 739 mm (eye-to-fork length) to 753 mm. The percentge of sngged pddlefish 10 yers old or older decresed from 15.3% in 1990 to 9.5% in When we compred the men length of sngged pddlefish with the men length of gillnet-cptured pddlefish from tilwter nd downriver sites there ws no difference s demonstrted by t-test. There ws significnt difference (Pt < 0.01) between men weights. The sme reltionship regrding length nd weight ws true when fish gillnetted downriver ws compred to fish gillnetted in the tilwter (Pt < ). These dt suggest tht lrger, sexully mture fish re congregted in the tilwter of Gvins Point Dm, which is totl brrier to fish migrtion. The quot of 1,600 fish ws exceeded in 1989 nd 1990 but ws not reched in the 1991 or 1992 sesons, which extended the full 30 dys. In the Gvins Point Dm tilwter re, totl nnul mn-hours of fishing ws up from 5,339 hours in 1990 to 8,563 hours in 1991 nd 9,139 hours in Men ctch rte for 1991 ws 0.1 fish per hour of sngging compred with 0.33 fish per hour in 1990; however, ctch rte declined to 0.05 during A protected slot-length limit ws imposed in 1992 nd ws considered successful becuse there ws no indiction of excessive mortlity ssocited with ctch nd relese. t t t Russell (1986) stted tht "pddlefish were once bundnt in the lrge rivers in the Mississippi River dringe. However, within the lst 100 yers, the peripherl rnge of the species hs shrunk." Declining pddlefish (Polyodon spthul (Wlbum); Fig. 1) popultions were ttributed to hbitt ltertion nd destruction, overexploittion nd pollution ssocited with wter-development projects, sport nd commercil hrvest for recretion nd met, nd the demnd for pddlefish eggs for cvir. The history of pddlefish hrvest from the Missouri River is good exmple of overhrvest ssocited with diminished recruitment. With the construction of seven lrge dms on the Missouri River minstem, pddlefish Figure 1. Pddlefish, Polyodon spthul. 53

3 54 L. W. Hesse nd G. E. Mestl sng fisheries developed in the tilwter of ech. These isolted popultions were overfished nd, before biologists relized wht ws hppening, were nerly extirpted. Sng fishermen hrvested 16,000 pddlefish during the fishing sesons in 1958, 1959, nd 1960 in the tilwter of Fort Rndll Dm, on the minstem Missouri River (Unkenholz, 1982). The hrvest declined bruptly in 1961 nd only very few pddlefish were hrvested between 1973 nd 1987, when mortorium on pddlefishing ws estblished jointly by Nebrsk nd South Dkot for the rech between Fort Rndll Dm nd Gvins Point Dm (the lowermost dm). The only res of the lower Missouri River remining open to pddlefishing lie long 124-km portion of remnnt unchnnelized Missouri River from the tilwter of Gvins Point Dm to the Big Sioux: River ner Sioux City, Iow, nd within the boundries of the stte of Missouri (Fig. 2). An estimted hrvest of 2,831 pddlefish occurred in 1971 in the rech between Fort Rndll Dm nd the next dm upstrem, Big Bend Dm, but by 1978 the hrvest hd declined to 125 fish (Unkenholz, 1982). The ge of 112 pddlefish rndomly selected from the Big Bend Dm tilwter ctch during 1973 rnged from 11 to 20 yers nd nerly 88% were ge 14 or older; the verge weight ws 28 kg. Nturl reproduction ws not reported fter closure of Big Bend Dm in 1964 (Friberg, 1974). Approximtely 8,400 pddlefish were hrvested from the tilwter of Ohe Dm, the next dm upstrem from Big Bend Dm, in , nd only few were tken therefter (Friberg, 1974). Pddlefish popultions hve prospered in Montn, ccording to Stewrt (1987). The fishes of Fort Peck Lke (Fort Peck Dm) nd Lke Skkwe (Grrison Dm), the next dm upstrem from Ohe (Fig. 2), hd ccess to "extensive, intct spwning res" in upper reches ofthe free-flowing Missouri River nd its tributries such s the Yellowstone River. Stewrt (1987) stted tht the ge structure of the Skkwe popultion indicted mture, helthy popultion; 7 percent were younger thn 10 yers, while 42 percent were ge 20 or older. The ge structure of this popultion ws somewht different in 1965; 41 percent were younger thn 10 yers, nd only 2 percent were ge 20 or older (Robinson, 1966). Grrison Dm ws closed in 1953, isolting this popultion of pddlefish. The objective of this pper is to evlute the trend in the density oflrvl nd lte young-of-the-yer (y-o-y) pddlefish, to describe popultion sttistics bsed on gill- nd trmmel-net surveys nd sng fishing hrvest informtion, nd to describe how mngement of pddlefish hrvest in Nebrsk hs chnged. METHODS Study re The Missouri River long Nebrsk's estern border cn be divided into sections bsed on the present morphologicl configurtion (Fig. 2). The rech between the hedwters of Lewis nd Clrk Lke nd the Nebrsk-South Dkot border is 64 km long nd remins unchnnelized nd unimpounded. However, fter Fort Rndll Dm ws closed in 1952 this rech hs not experienced ny nturl high-wter events. We refer to this rech s the upper unchnnelized section. Lewis nd Clrk Lke (42 km) is brcketed by the upper unchnnelized section nd the lower unchnnelized section, which extends 93 km from the tilwter of Gvins Point Dm to Ponc, Nebrsk. This rech hs not flooded since 1952, lthough Gvins Point Dm ws closed in This lower rech hs experienced severe chnnel-bed degrdtion (deepening) due to sedimenttion in Lewis nd Clrk Lke. There is smll (25 km) section of river tht ws stbilized with rock nd wooden piling between Ponc, Nebrsk nd Sioux City, Iow, where complete chnneliztion strts nd then extends 1,183 km to the confluence with the Mississippi River. The chnnelized portion long Nebrsk extends for 394 km nd we hve seprted this rech into n upper chnnelized section (Sioux: City to Omh, Nebrsk) nd lower chnnelized section (Omh to the Nebrsk-Knss border) (Fig. 2). The upper unchnnelized rech hs one mjor tributry (the Niobrr River), extensive bckwter res, nd some rubble substrtes; turbidity hs been eliminted; wter temperture hs been ltered due to deeprelese dms; nd chnnel degrdtion hs occurred in the upper three-fourths of the rech. The nturl hydrogrph hs been eliminted. Fort Rndll Dm releses power-peking dischrges, which result in dily stge fluctutions downstrem tht exceed meter. Since Fort Rndll Dm is the lst lrge dm on the minstem, its reservoir is used to store high spring run-off which would otherwise contribute to high stge redings long the chnnelized sections. This eventulity hs resulted in zero releses t Fort Rndll Dm, which dewters the upper unchnnelized section. The upper chnnelized section hs experienced extreme chnnel-bed degrdtion; old bckwters hve been completely isolted from the chnnel. Turbidity remins somewht higher thn in the lower unchnnelized section due to the inflow of mteril from eleven tributries nd dringe ditches. Lewis nd Clrk Lke is the smllest minstem dm nd the lowermost. It cn store just 9% of the wter stored behind Fort Rndll Dm. Gvins Point

4 Pddlefish in the Missouri River 55 Shrpe (Big Bend Dm) (RK 1,588) Frncis Cse (Fort RndU Dm) (RK 1,416) LeWIS nd Ork (Gvlns Pomt Dm! (RK 1,305) Iow City (RK 1,178) Figure 2. Mp of the Missouri River bsin showing the loction ofthe min-stem dms, unchnnelized reches (between Fort Rndll Dm nd Lewis nd Clrk Lke nd between Gvins Point Dm nd Sioux City) nd the chnnelized section (Sioux City downstrem to the Mississippi River). RK = river kilometer E Vl 5 o <lj 6 f- 4 <lj 0- ~ 3 <lj ;:: Q.)... 2 o ("'..J en en en = co = co co en = en en en = = en en ("'..J Eye to Fork Length in mm Figure 3. Length distribution of pddle fish from the lower Missouri River 1991 sng fishery.

5 56 L. W. Hesse nd G. E. Mestl Dm is used to re-regulte the errtic peking dischrge from upstrem into n even dischrge April November to support nvigtion in the chnnelized sections. The lower unchnnelized section hs severl smll tributries, the Jmes nd Vermillion rivers, nd snd bed with little or no rubble substrtes. Old bckwters hve been eliminted due to severe chnnel-bed degrdtion; nd the hydro grph hs not been nturl since Turbidity is higher thn in upstrem reches, nd wter temperture is more nerly nturl becuse Lewis nd Clrk Lke is shllow nd completely wind-mixed. The lower chnnelized section is fr enough from the dms tht degrdtion no longer occurs, nd in fct res of ggrdtion exist. Old bckwter res hve been completely cut off by rock dikes. Turbidity cn become high from runoff from 20 tributry strems nd dringe ditches which empty into this rech. Field collections During the period 1983 through 1991 the density of drifting ichthyoplnkton (including pddlefish) ws mesured in the upper nd lower unchnnelized sections. Drift-net collections were expnded during 1986 to include the chnnelized sections. Lrvl-fish smples were not cquired during Drift-net collections were mde with one-meter dimeter plnkton nets with 560-micron mesh netting nd flowmeter in the mouth to quntify the volume of wter filtered. Two double-net tows for three to five minutes t the cutting bnk, filling bnk, nd midchnnel constituted typicl smple t ech site. Ctch per unit effort (CPUE) ws reported s the number of lrve per 1,000 m3. South Dkot Gme Fish nd Prks reported (Unkenholz, 1982) lrvl-pddlefish density cquired from collection sites in the upper unchnnelized sections from 1975 through These dt were used with our dt to provide long-term perspective on the density of drifting pddlefish lrve. Young-of-the-yer (y-o-y) pddlefish were collected in July with 7.9-m (hedrope) semi-blloon otter trwl fished in the old river chnnel in Lewis nd Clrk Lke. CPUE ws reported s the number of pddlefish cptured per minute of trwling. Trwl dt from 1965 through 1974 were cquired by the U.S. Fish nd Wildlife Service (Kllemeyn, 1975); dt from 1975 through 1981 were cquired by South Dkot Gme Fish nd Prks (Unkenholz, 1982), nd we obtined trwl dt in 1986, 1989, 1990, 1991, nd Trwl dt from 1987 nd 1988 were collected by J. C. Schmulbch nd S. Wessel ofthe University of South Dkot, Vermillion, with funding nd equipment support from Nebrsk Gme nd Prks Commission. All trwl dt were used to provide long-term perspective on the density of y-o-y pddlefish in Lewis nd Clrk Lke. The density of pddlefish lrve nd y-o-y were correlted with three hydrulic vribles, including guge index (m) derived by subtrcting the monthly minimum dischrge from the monthly mximum nd clculting men of these differences for ech yer between 1956 nd Men guge (MG) ws simple men of dily men dischrge vlues for the yer, nd flushing rte ws men nnul period (in dys) tht the totl volume of Lewis nd Clrk Lke ws replced through outflow t Gvins Point Dm. m represents mesure of nnul wter fluctutions, while MG ccounts for wter yers with different totl volume runoff. Flushing rte reflects the mount of wter held in storge in Lewis nd Clrk Lke nd the mgnitude of dischrge t Gvins Point Dm. We used Spermn correltion (rnked vlues) nd Person correltion to determine reltionships between hydrulic vribles nd biologicl vribles. A prtil creel-survey of sng fishermen ws conducted in 1987; more thorough hrvest surveys were completed in in the Gvins Point Dm tilwter. South Dkot biologists ssisted with these surveys. We cquired hrvest informtion from sng fishermen in 1992 s prt of recretionl use survey tht ws conducted during the entire yer. All pddlefish sngged in the tilwter re were mesured from the eye to the fork of the cudl fin (EF), mny were weighed, nd the lower jw ws removed from subsmple for ge nlysis. Age dt were used to crete yer-clss index (EI-Zrk, 1959), which ws subsequently used to correlte with hydrulic nd other biologicl vribles. Pddlefish hve been collected since 1990 with gillnets nd trmmel nets, nd collected fish were tgged to study exploittion rte nd migrtionl behvior. Pddlefish were successfully cptured with dedset gillnets t the surfce nd t the bottom in the Gvins Point tilwter re. These nets were rised every 20 minutes. Most fish collected from riverine hbitt were collected by floting trmmel or gillnets through likely loctions. The gillnets used in 1990 were 90 m long, 2.4 m deep nd wholly composed of either 51-, 64-, or 76- mm mesh. In 1991 we used gillnets tht were 122 m long, 3.1 m deep, nd of 76-mm mesh, nchored on the bottom nd surfce in the Gvins Point Dm tilwter re. Downstrem from Gvins Point, in the lower unchnnelized section, we floted gillnet t the surfce through likely pddlefish hbitt. In 1992, we used 122-m gillnets nchored on the bottom in the tilwter re, nd we floted hevy-duty (twine size 15) trmmel nets with 76-mm mesh inner pnel, nd

6 Pddlefish in the Missouri River ; 0.. E 0 Vl 0 15 I- ; g 10 C ; u cu... 5 o Weight in kg Figure 4. Weight distribution of pddle fish from the lower Missouri River 1991 sng fishery. ; 0.. E 0 Vl Ci \ 15 I- ; 0' 0 10 C ; u cu... \ Yer-Clss Figure 5. Age distribution of pddlefish from the lower Missouri River 1991 sng fishery.

7 58 L. W. Hesse nd G. E. Mestl Tble I. Pddlefish lrve, volume of wter filtered (x1,000m3) nd CPUE (lrve per 1,000m3) collected from the Missouri River, Nebrsk. Upper Unchnnelized Lower Unchnnelized Chnnelized Yer No. (CPUE) Volume No. (CPUE) Volume No. (CPUE) Volume (0.16) (0.0) (0.0) (0.0) (0.08) (0.02) (0.43) (0.0) (0.15) (0.20) (0.0) (0.0) (0.42) (0.0) (0.14) (1.19) (0.0) (0.00) (0.03) (0.0) (0.19) (0.84) (0.0) (0.0) Totls 53 (0.30) (0.005) (0.10) outside pnels of 457-mm mesh. The nets were 91 m long nd 3.7 m deep nd were tied down to 2.4 m. RESULTS AND DISCUSSION Lrvl pddlefish collections The men density of pddlefish lrve between 1983 nd 1991 ws 0.30 per 1,000 m3 in the upper unchnnelized rech. The men density ws much lower (0.005) in the lower unchnnelized rech. Lrvl-pddlefish density verged 0.10 per 1,000 m3 in the chnnelized rech. Although the CPUE ws quite vrible from yer to yer in the upper unchnnelized rech, t lest one pddlefish lrv ws collected in ll yers except Only one pddlefish lrv hs been collected in the lower unchnnelized section (1985) since 1983 nd severl were collected in 1986, 1988 nd 1990 in the chnnelized section (Tble I). Drift net collections in the upper unchnnelized section were mde t three loctions, including 16, 64 nd 71 km downstrem from Fort Rndll Dm. The first site ws just downstrem from 6-km rubble shoreline; site 2 ws just downstrem from the mouth of Choteu Creek, nd the lowermost site ws 2 km downstrem from the mouth of the Niobrr River. Only 2 (3.8%) lrve were collected in the upstrem site; 15 (28.3%) were collected ner Choteu Creek nd 36 (67.9%) were collected downstrem from the Niobrr River since All lrve from the lower two sites were collected in the turbid dischrge from the two tributry strems, except one from the opposite bnk from Choteu Creek. In the spring of 1991, Secchi-disk trnsprency verged 1.1 m (rnge m) in ll loctions upstrem from Choteu Creek to the tilwter of Fort Rndll Dm, while in the plume of Choteu Creek nd the Niobrr River, Secchi-disk trnsprency verged 0.25 m (rnge m). Unkenholz (1980) reported collecting 45 pddlefish lrve in , 93% of them downstrem from the Niobrr River confluence. Most recently, mture pddlefish hve been collected in My nd June in the 2-km rech between the Niobrr River nd our lowermost drift-net site (personl communiction, Jmes C. Schmulbch, University of South Dkot, Vermillion). We hve observed more pddlefish in this rech recently, s well, which my suggest tht the hrvest mortorium, strted in 1987, hs enhnced survivl. Young-of-the-yer pddlefish collections The highest trwl density for occurred in 1991 (Tble 11). Moreover, 1991 proved to hve the highest ctch rte (1.10) since trwling begn in Unkenholz (1982) reported on y-o-y pddlefish collections completed by the U. S. Fish nd Wildlife Service, North Centrl Reservoir Investigtions ( ) nd on similr trwl effort by South Dkot Gme Fish nd Prks ( ). Ctch rte in rnged from 0.05 to 0.68 per minute of trwling; the men ws 0.22 (8 = 0.18). Ctch rte for rnged from 0.02 to 0.33; the men ws 0.13 (8 = 0.11). Most recently ( ) ctch rte rnged from 0.03 to 1.10; the men ws 0.34 (8 = 0.36); the 1991 ctch rt ws the highest ever recorded. The men for the period of (excluding 1991 dt) ws 0.21 (8 = 0.14) which more closely pproximtes the period. The men of nnul men dily dischrges t Fort Rndll Dm ws 29,000 cubic feet per second (CFS) for the period , 31,360 CFS for the period , nd 22,780 CFS for the period 1981-

8 Pddlefish in the Missouri River 59 Tble II. Number of pddle fish y-o-y collected nnully with bottom trwl from Lewis nd Clrk Lke from 1986 through CPUE equls the number of y-o-y pddlefish per minute of trwl time. Minutes No. of Yer trwled y-o-y CPUE * * * * * * * 1987 nd 1988 dt were provided by Jmes C. Schmulbch nd Scott Wessel, University of South Dkot, Vermillion. Minutes trwled nd numbers collected will be reported in Wessel's thesis Higher men dily dischrge t Fort Rndll Dm shows tht bsin run-off ws higher, which shows tht fluctuting dischrge ws higher due to floodcontrol ction t Fort Rndll Dm. Men GI for the periods ws similr for (14.02) nd (14.51), while the men GI for (11.95) ws quite different. Lower run-off yers under the controlled-relese mngement, in plce since 1954, my be beneficil for young pddlefish becuse there is less need to fluctute dischrge t Fort Rndll Dm to reduce flood crests long the river from Omh downstrem. Popultion sttistics from sngged pddlefish Hrvest surveys hve provided n opportunity to mesure nd weigh 5,075 nd 3,972 pddlefish, respectively. In ddition, jws were removed from 1,714 pddlefish for ging (Tble III). Men EF length for the period ws 727 mm; men weight ws 6.63 kg nd men condition fctor ws The percentge offish 10 yers of ge or older (pproxi- mtely the ge of sexul mturity) vried; the men for the period ws 11.7%. The survey methodolgy used in 1992 provided n opportunity to gther some limited men-length dt (sngged fish) from the upper nd lower ends of the unchnnelized rech open to sngging, in ddition to the tilwter dt. The men length of fish sngged in the tilwter ws 720 mm (8 = 117 mm, N = 144 fish), nd the men length of ll downriver sngged fish ws 689 mm (8 = 88, N = 70). The difference ws significnt when mens were compred in t-test (t = 1.99, p = 0.04). However, when the men length from the upper end of the unchnnelized section (nerest the tilwter re) (682 mm, 8 = 89 mm, N = 62) ws compred with tht for the lower end 84 km downstrem (738 mm, 8 = 72, N = 8), the difference ws significnt (t = 1.69, p = 0.09). Lrger fish hve been shown to ccumulte in the Gvins Point tilwter, but it is possible tht they re ttrcted there from only portion of the unchnnelized rech downstrem from the dm. The upper Missouri River in Montn supports lrge sport fishery for pddlefish. Pddlefish were isolted between Fort Peck Dm in Montn nd Grrison Dm in North Dkot in 1953, rech tht includes the confluence ofthe Yellowstone River. Pddlefish were observed to ccumulte t the Intke diversion dm (pproximtely 80 km upstrem from the confluence) nd sng fishery developed by 1962 (Robinson, 1966). Robinson (1966) found the men weight of sngged pddlefish (2,562) to be 9.9 kg in 1964 nd 1965, nd 59.2% were 10 yers old or older. By men weight incresed to 14.9 nd 16.2 kg, respectively (Rehwinkel, 1978). Stewrt (1991) reported the men weight of 16,981 sngged pddlefish during to be 21.0 kg (8 = 1.1) nd the men length ws 1,078.7 mm (EF, 8 = 10.7). The pddlefish popultion downstrem from Gvins Point Dm ws found to include smll percentge of lrger (Figs. 3 nd 4) nd older fish (Fig. 5). However, Tble III. Popultion sttistics of pddlefish sngged from 1987 through 1992 in the Gvins Point Dm tilwter re Men Number of fish mesured 87 1,321 1,217 1, *5,075 Men eye to fork length (mm) Number offish weighed ,210 1, *3,972 Men weight (kg) Men K-fctor Number offish ged *1,714 % Ten yers or older * Totls for the six yers

9 60 L. W. Hesse nd G. E. Mestl recruitment to the sng fishery hs continued, s demonstrted by the high percentge of fish younger thn six yers (78%) (Fig. 5) tht hve been sngged. The length nd weight distributions (Figs. 3 nd 4) show tht smll fish re recruiting into the fishery, nd they contribute to smll men length nd weight. Dt from 1991 were used to construct these distributions to provide the most current informtion; 1992 dt were not used becuse protected slot length limit ws in effect during Therefore, 1991 ws the lst yer to obtin length, weight nd ge distribution dt from sng fishermen before they were llowed to select the fish they wished to keep. We used the percentge composition between ge clsses to clculte totl nnul mortlity bsed on 296 fish ged in The ctch curve showed tht ge-4 nd older fish were fully recruited to the sng fishery. Annul mortlity ws 6% for five-yer-old fish but incresed to 39% for six-yer olds, 50% for seven-yer olds nd 80% for eight-yer olds. Few fish survived beyond nine yers nd these ge groups were only spordiclly hrvested. Nerly 72% of the pddlefish hrvested downstrem from Gvins Point Dm weighed less thn 6.8 kg (15 pounds); conversely, the upper Missouri River popultion ppers to contin fewer young fish. Stewrt (1991) reported just 1.6% of the sngged mle pddlefish t Intke weighed less thn 15 pounds nd only 0.24% of the sngged femles weighed less thn 25 pounds. Sng-hrvest sttistics The sng-fishing seson in Nebrsk hs become much more restrictive in the pst 35 yers (Stone, 1987). The entire Missouri River long Nebrsk ws open yer-round during the 1960s nd for s long s seven months (October-April) in the erly 1980s. By 1987, concern for dwindling pddlefish density prompted Nebrsk nd South Dkot to close the upper unchnnelized rech; concern for excessive incidentl hrvest of other species wintering in wing-dike holes in the chnnelized section led to closure of the river downstrem from the Big Sioux River confluence t Sioux City to ll sngging for pddlefish nd to shortening of the seson in the remining open re to 30 dys (November). These regultions remined in effect from 1987 until 1989, when 1,600-fish hrvest quot ws instituted for the open re, nd the dily bg limit ws reduced to one. A totl-user survey ws implemented to count sngged fish nd close the seson when 60% of the quot ws reched in the Gvins Point Dm tilwter re. Previous informtion regrding hrvest suggested tht pproximtely 60-87% of hrvest occurred in the tilwter (Friberg, 1973; Hesse, 1980; Stone, 1985, 1987). A complete census of ll sngged pddlefish ws only possible in the tilwter re. A protected slot-length limit ws imposed for the 1992 sngging seson. All fish between 889 nd 1143 mm EF hd to be relesed. All other fish could be kept or relesed. The 1,600-fish quot remined in effect, s well, during the 1992 seson. The sngging seson lsted 30 dys in 1988 nd the dily bg ws two pddlefish per fishermn. Tble IV shows the results for the first four dys of the sesons for 1988 through 1991 nd seson totl. The hrvest of pddlefish in 1988 ws estimted to be 2,691 in the tilwter re t ctch rte of 0.26 per hour; 1986 hrvest ws estimted to hve been nerly double this number (5,488) t rte of 0.27 (Stone, 1987). All fish sngged were included in the bg by regultion during recent yers. However, in 1972 sng fishermen were llowed to ctch nd relese, nd the ctch rte still verged 0.41 fish per hour (Friberg, 1973). These dt suggest decline in bundnce of t lest 37% between 1972 nd 1988, but the ctul sng ctch rte in 1972 ws higher if the first fish hd been kept, therefore the chnge in density ws greter. The number of fishermen incresed by 48% nd mn-hours incresed 29% (Tble IV) during 1989, the first yer of the quot. The hrvest quot ws exceeded on the second dy of the seson but notifiction procedures prevented closure for 48 dditionl hours. Men sng ctch rte (0.25) ws similr to The hrvest quot ws exceeded on the second dy of the 1990 seson nd the four-dy seson llowed time to exceed the pre-set quot by 74%. Ctch rte incresed (0.33) by 32% from The hrvest quot for 1991 remined the sme but certin res within the tilwter were closed to sngging from bot or the bnk. These res were loctions where pddlefish, especilly lrge femles, were most vulnerble. The result of this regultion nd other fctors, including, bnormlly wrm wether erly in the seson nd mjor blizzrd hlf wy through the seson, reduced the ctch rte from 0.33 in 1990 to 0.10 in 1991 (Tble IV). The fishing success ws down nd s result the quot ws not reched nd the seson extended full 30 dys, by which time 898 fish hd been hrvested. We believe the protected res prevented some of the lrger femles from being hrvested nd contributed to the decline in men weight experienced during Since men length ctully incresed, we believe reduced hrvest ssocited with the hrvest quot hs improved survivl. The protected res included cnl tht crried dischrge from the powerhouse turbines. The velocity in this cnl ws similr to min chnnel velocities. If sexully mture fish were to migrte to stging res ner spwning substrtes lte in the fll, this cnl

10 Pddlefish in the Missouri River 61 Tble IV. Gvins Point Dm tilwter pddlefish sngging seson complete census informtion for (numbers of 1992-relesed fish in prentheses). No. of No. of Percent Dy pddlefish Mn-hours Ctch rte fishermen successful ,150 2, , Totl 2,691 10, , , , Totl 1,364 5, , , , , Totl 1,743 5, , , , Totl 898 8, , * 101 (39) 2, * 14 (13) 1, * 8 (6) Totl** 540-9, Totl*** 1,000 21, *Actul **Estimted tilwter ***Estimted totl open re would be the most likely route selected by migrting fish. Observtions during previous sngging sesons hve shown the lrgest sngged pddlefish cme from the bse of the dm in this cnl. fishing re ws surveyed s prt of totl recretionl use survey. The number nd rte of hrvested pddlefish declined drmticlly from previous yers (Tble IV), while mn-hours of fishing time were bout 20% higher thn the previous 4-yer verge. The chnging regul- tions hve mde it difficult to evlute the mening of declining ctch rte. We hve redoubled our effort to 'The first three dys of the 1992 sngging seson in the Gvins Point tilwter ws monitored with complete census s done in previous yers. The reminder of the 30-dy seson nd other portions of the open

11 62 L. W. Hesse nd G. E. Mestl obtin nother index for reltive popultion density, but for now we do not know if reduced ctch rte suggests reduced density of pddlefish. The first-yer evlution ofthe protected slot-length limit ws successful in the sense tht no mortlly wounded fish were reported by ny fishermen t the check sttions or by ptrolling conservtion officers. The opportunity to relese smll fish ws pprecited by fishermen, nd the chnce to fish nd not hrvest t ll ws pprecited by some s well. Tgging nd exploittion With periodic help from South Dkot biologists, we tgged 68 pddlefish in the tilwter of Gvins Point Dm during October, 1990, but prior to the sngging seson. The 1990 sng hrvest ws estimted to hve been 1,927 fish; 16 tgs were returned for n exploittion rte of 24% nd popultion estimte of 8,029 fish. In October of 1991 we tgged 95 pddlefish in the tilwter nd 9 (9% ofthe 1991 tgs) were recovered by sng fishermen from 898 hrvested fish. The reltive popultion estimte ws 9,978 fish. In ddition, we tgged 177 pddlefish 19 km downriver during 1991, but only two were sngged in the tilwter. They were not included in estimtes of exploittion or popultion. No downriver tgs were returned by mil, lthough we know severl were tken by fishermen. We tgged 42 pddlefish during 1992 in the tilwter of Gvins Point Dm nd 204 pddlefish in the riverine, unchnnelized rech. All downriver fish were tgged within 8 km ofthe confluence of the Jmes River. Archery fishermen returned two tgs during the July rchery seson. Both were tgged in the riverine rech nd were mong 108 tgged prior to the rchery seson (0.9%). Four of the remining 202 riverinetgged fish were reported hrvested during the 1992 sngging seson (2.0%). One riverine tg ws hrvested from the riverine rech, two riverine tgs were hrvested from the tilwter re, nd the lst one ws hrvested by commercil fishermn 121 km up the Kskski River in Illinois. One of the 42 tilwtertgged fish (2.0%) ws hrvested in the riverine portion. In ddition, three 1991 tgged pddlefish were hrvested during the 1992 sngging seson; one ws tken by commercil fishermn from the Mississippi River t Hickmn, Kentucky. Three 1990-tgged pddlefish were hrvested during the 1992 seson. Totl exploittion bsed on only 1992-tgged fish reported by fishermen ws bout 5%. Non-reported tgs would increse the rte, but most likely ctul exploittion ws less thn 10%. Stewrt (1991) reported sme-yer tg returns to rnge from 4% to 14.1%. Combs (1982) reported tht n nnul exploittion rte up to 19% ws not detrimentl to pddlefish in Oklhom, but Purkett (1963) nd Gengerke (1978) hve noted declining ctch rte, men size nd ge ssocited with exploittion rtes between 7 nd 22%. The present exploittion rte (9-24%) for the fishery downstrem from Gvins Point Dm ws too high considering the low lrvl density nd y-o-y survivl. The hrvest of 1992 resulted in n exploittion rte tht is most likely pproprite for the short-term; however, dditionl study will be required in order to determine if this level of exploittion cn be sustined for the long-term. Gillnet survey of pddlefish downstrem from Gvins Point Dm Surveying sng fishermen to obtin length nd weight dt is lbor-intensive, nd chnging mngement, such s closed res or size limits cn impct the dt cquired. We hve successfully collected pddlefish in 1991 nd 1992 with gill nets nd trmmel nets. We believe these smpling procedures will provide longterm monitoring cpbility, independent of sng fishermen. Fish collected in this mnner cn be tgged to study exploittion. During 1991 (spring nd utumn), we cptured 83 pddlefish in the Gvins Point Dm tilwter nd 180 fish downstrem in sndbr pools in the lower unchnnelized Missouri River. Besides receiving Monel bndet round the jw, ech fish ws weighed nd mesured. The men length of tilwter fish ws 791 mm (EF) compred with 725 mm downriver, nd men weight ws 9.0 kg vs 5.1 kg. A t-test showed these differences were significnt (Pt < ). However, when men length nd weight for ll pddlefish cptured in 1991 in gillnets nd trmmel nets (tilwter nd downriver) (748 mm, 6.3 kg) were compred in t test with the men length (753 mm) nd weight (7.5 kg) of fish sngged in 1991, there ws no difference in men length; lthough men weight ws different (Pt = 0.007). During 1992, gillnet nd trmmel-net effort resulted in totl collection of 280 pddle fish of which 246 were tgged s reported previously. Totl men length of the netted fish ws 755 mm (8 = 121 mm), compred with men of 748 mm in 1991 (not significnt). There is some evidence of the movement pttern of selected size groups of pddlefish from nlyses of the men length on monthly bsis in the tilwter re versus the upstrem portion of the riverine rech. The men length in the tilwter increses from 701 mm in Mrch to 746 mm in April to 885 mm in August, while in the riverine rech the pttern is reversed. The

12 men in Mrch ws 795 mm, 764 mm in June, 746 mm in July, nd 722 mm in August. One importnt spect of net surveys tht remins to be worked out is n index for ctch per unit effort. This remins high priority. Modeling We creted mtrix of biologicl nd hydrulic vribles for correltion nlysis (Tble V). Yer-clss Tble V. Biologicl nd physicl dt used in correltion modeling including dult pddlefish yer clss indices, y-o-y pddlefish CPUE (number per minute), lrvl pddlefish (only portion of the upper unchnnelized smples were included s defined in the text) CPUE (number per 1,000 m3), GI nd MG for Fort Rndll Dm nd flushing rte for Lewis nd Clrk Lke (dys). Yer clss Yer index y-o-y Lrve GI MG Flush * **0.17 ** * Kllemeyn 1975 ( ). ** Unkenholz 1982 ( ). Pddlefish in the Missouri River 63 index, GI, MG nd Flush dted bck to Trwl surveys dted bck to 1965 nd drift net surveys dted bck to We used only those lrvl fish smples collected from the lowermost portions of the upper unchnnelized section becuse very few lrvl pddlefish were collected upstrem from the Niobrr River confluence. We believe this hs resulted from the dded impct from ltered wter temperture nd turbidity, which might confound identifiction of reltionship between Fort Rndll Dm dischrge nd lrvl density. For this reson, the vlues for lrvl pddlefish density re not uniform between Tble II, which reported ll lrve collected nd ll volume filtered nd Tble V. In ddition, since fish lrve were not collected in 1992, the model does not include ny 1992 dt. There ws strong reltionship between lrvl density nd y-o-y bundnce in the upper unchnnelized rech (r = , p = ). We lso found firly strong reltionships between lrvl density nd GI (r = ,p = ), ndmg(r= ,p = ). We found no reltionship between yer-clss index, which is derived from sngged fish in the lower unchnnelized rech (downstrem from Gvins Point Dm) nd other vribles, including, lrve, y-o-y, GI, or MG. However, we did find strong reltionship in Person correltion between the June-August flushing rte for Lewis nd Clrk Lke nd yer-clss index (r = , P = ). The best reltionship occurred when we selected only June dt (r = , p = ); (June July r = , p = ; July r = , p = ; August r = , p = ). These results suggest tht successful reproduction occurs when fluctuting dischrge is minimized. It lso shows tht yer-clss development downstrem from Gvins Point Dm is dependent on recruitment from upstrem nd occurs s result of the dischrge of young pddlefish during June nd July primrily. Since we do not collect pddlefish lrve in the tilwter, we believe they exit the lke fter they hve mtured beyond the lrvl stge. RECOMMENDATIONS Our dt demonstrte tht, lthough the spwning migrtion hs been blocked by dms, pddlefish could find limited spwning substrtes downstrem from Gvins Point Dm. However, our dt clerly demonstrte tht successful spwning, s mesured by the presence of lrve in the drift, hs not occurred in the lower unchnnelized section of the Missouri River. There re t lest two possible resons, including too few sexully mture femles or the lck of spwning cue (the spring rise in wter elevtion). We hve dem-

13 64 L. W. Hesse nd G. E. Mestl onstrted tht hrvest hs eliminted mny of the older fish tht would be sexully mture. Purkett (1963) suggested tht rising stge during the spring spwning period ws essentil for the onset of spwning in pddlefish. We hve found negtive reltionship between the density of drifting pddlefish lrve nd fluctuting dischrge t Fort Rndll Dm. The hydrogrph t Fort Rndll, Gvins Point nd ll other minstem dms no longer resembles the nturl hydrogrph (Hesse nd Mestl, 1993). Unless semblnce of the nturl hydrogrph is recovered, we will not hve n effective wy to determine the impct of no spring rise. Scrnecchi et l. (1989) discussed the reltive merits of protecting femle spwning-size pddlefish nd concluded tht, for those living in the upper Mississippi River, protection ws importnt. They proposed hrvest slot length limit of cm (EF). We disgree with Scrnecchi's et l. (1989) ssessment of study by Friberg (1974) tht concluded "highgrding" results in high mortlity. The study ws not interpreted properly, nd in relity it concluded tht 86% of the sngged pddlefish held in htchery ponds during the summer survived. We hve observed old sngging wounds nd rostrums entirely removed by outbord motor propellers on 31% of ll pddlefish in the Gvins Point Dm tilwter. Mny of these wounds were heling nd the fish, with very few exceptions, ppered otherwise quite helthy. Our mjor concern regrding hook relted mortlity ws the possibility of hook piercing the interior wll of the body cvity, which could crete severe infection internlly. We reduced the legl hook size to one-hlf inch mesured from point to shnk in n effort to minimize this problem. We selected protected slot of 889-1,143 mm (35-45 inches) (EF). Our regultion, s written, llows fishermen to relese even those fish shorter or longer thn the slot. Bsed on the 1991 hrvest informtion, we would hve eliminted 17% of the fish removed in 1991, ssuming ll fish outside of the slot were kept. Fish in the protected slot will rnge from 9 to 18 kg (20 to 45 pounds). We expected hrvest would be concentrted on fish in the 4- to 9-kg rnge becuse these were the prefered eting size nd were most numerous. Actul hrvest rnged from 0.4 to 10 kg. Mintennce of strict hrvest quot should prevent overhrvest of young fish. We expect lrge numbers of pddle fish to ccumulte in the protected rnge. Mny of these fish will survive beyond the slot; however, the slot includes femles in their erliest yers of mturity, thus enhncing the number of vilble spwning femles. At the sme time we llowed sng fishermen the opportunity to hrvest trophy sized pddlefish, thus enhncing the specil imge ofthis unique niml. Severl dditionl sngging sesons with the slot limit will be required before sttistics on men length cn be used to fully evlute the impct of this regultion on pddlefish. Moreover, s some pddlefish interchnge with other rivers tributry to the Mississippi, it my tke more thn severl sesons. Continued tg studies will be essentil in order to evlute exploittion rtes for pddlefish, especilly on those fish lrger thn the slot. If exploittion of these older fish exceeds 25%, we would recommend n dded restriction of one trophy sized pddlefish per fishermen per yer. In ddition, tgging should be implemented in other loctions within the Mississippi River system in order to more fully understnd the reltionship of one river with nother from the viewpoint of pddlefish. We hve determined tht the use survey, s conducted during 1992, did not do n effective job estimting pddlefish hrvest. We re left with only one rel lterntive to obtin good hrvest nd exploittion dt nd tht is to conduct ner totl census s hs been done during the previous four yers. However, nother possible lterntive is used by the Stte of Wisconsin to mnge lke-sturgeon hrvest. Fishermen re issued one tg per yer. To be kept, the fish must be immeditely tgged upon its ctch. Further, the fish must be reported by telephone to the centrl office by 1800 hours the next dy. In our cse, 1,600 tgs (or whtever number we decide upon) could be mde vilble t the beginning of the yer. Only one tg could be obtined t time, nd it could be used either for rchery or sngging. Once the tg hs been filled nd reported the fishermn could obtin nother tg by mil if ny remin. With such mngement pln, rchery seson could open 1 July nd remin open for one month. Sngging seson could open 1 November nd remin open one month or until 1,600 tgged fish were reported s result of hrvest during both sesons. In this mnner both hrvest methods re covered under one quot. At the end of the seson, unused tgs nd n eye to fork length of hrvested fish should be returned on crd supplied with ech tg issued. Filure to return crds or tgs could be justifiction for nonissunce of future tgs. We propose tht this pproch be dopted for the 1995 seson nd beyond. LITERATURE CITED Combs, D. L Angler exploittion of pddle fish in the Neosho River, Oklhom. North Americn Journl of Fisheries Mngement 2(4): EI-Zrk, Slk EI-Din Fluctutions in the popultion of yellow perch in Sginw By Lke Huron. Fishery Bulletin 151, volume 59. U.S. Government Printing Office, Wshington, Friberg, D. V Investigtion of pddlefish popu-

14 ltions in South Dkot nd development of mngement plns, Dingell-Johnson Project F- 15-R-7, Study IX. South Dkot Deprtment of Gme, Fish nd Prks, Pierre: 32 pp Investigtion of pddle fish popultions in South Dkot nd development of mngement plns, Progress report, D-J project F-15-R. Deprtment of Gme Fish nd Prks, Pierre: 38 pp. Gengerke, T. W Pddlefish investigtions. Finl report, NMFS project R. Conservtion Commission, Des Moines, Iow: 86 pp. Hesse, L. W Creel survey - Missouri River commercil nd sport fishermen. Finl report, D-J Project F-15-R. Nebrsk Gme nd Prks Commission, Norfolk, Nebrsk: 29 p., nd G.E. MestI An lterntive hydrogrph for the Missouri River bsed on the pre control condition. North Americn Journl of Fisheries Mngement 13(2}: in press. Kllemeyn, L. W Investigtion of pddlefish popultions in South Dkot nd development of mngement plns, Progress report D-J project F-15-R. Deprtment of Gme Fish nd Prks, Pierre: 13 pp. Purkett, C. A., Jr The pddlefish fishery ofthe Osge River nd the Lke of the Ozrks, Missouri. Trnsctions of the Americn Fisheries Society 92(3}: Rehwinkel, B. J The fishery for pddlefish t Intke, Montn during 1973 nd Trnsctions of the Americn Fisheries Society 107(2}: Robinson, J. W Observtions on the life history, movement, nd hrvest of the pddlefish in Montn. Proceedings of the Montn Acdemy of Sciences 26: Russell, T. R Biology nd life history of the pddlefish-a review, pp In: J.G. Dillrd, et I., (eds.). The pddlefish: Sttus, mngement nd propgtion. Specil publiction Number 7, North Centrl Division, Americn Fisheries Society. Scrnecchi, D. L., T. W. Gengerke, nd C. T. Moen Rtionle for hrvest slot limit for pddlefish in the upper Mississippi River. North Americn Journl of Fisheries Mngement 9: Stewrt, P. A Pddlefish investigtions. Progress report, D-J project F-30-R. Deprtment of Fish, Wildlife nd Prks, Helen, Montn: 11 pp Yellowstone River pddlefish investigtions. Progress report, D-J project F-46-R. Deprtment of Fish, Wildlife nd Prks, Helen, Montn: 12 pp. Stone, C. C Lewis nd Clrk Lke fishing nd hunting use survey, Wildlife Division Report Number South Dkot Deprtment of Gme, Pddlefish in the Missouri River 65 Fish nd Prks, Pierre, South Dkot Pddlefish hrvest in the Missouri River below Gvins Point Dm. Progress Report D J Project F-21-R, Deprtment of Gme Fish nd Prks, Pierre, South Dkot: 21 pp. Unkenholz, D. G Investigtion of the pddlefish popultion nd recruitment in the Missouri River below Gvins Point Dm. Progress Report D-J Project F-15-R, Deprtment of Gme Fish nd Prks, Pierre: 7 pp Pddlefish spwning movements nd reproductive success in the Missouri River below Fort Rndll Dm, Completion Report No. 82-3, Deprtment of Gme Fish nd Prks, Pierre: 17 pp.,