Ozarkian Fresh water Mussels (Unionoidea) in the Upper 11 Point River, Missouri

7 Pages·1991·2.3 MB·English

by  R E Warren

OZARKIAN FRESH-WATER MUSSELS (UNIONOIDEA)
IN THE UPPER ELEVEN POINT RIVER, MISSOURI
ROBERT WARREN
E.
ILLINOIS STATE MUSEUM
CORNER SPRING AND EDWARDS
SPRINGFIELD, ILLINOIS 62706, U. S. A.
ABSTRACT
Fourteenspeciesoffresh-watermussels(Bivalvia: Unionoidea)werecollectedin 1990fromthe
upperreachesoftheEleven Point RiverinOregonCounty, Missouri.Thecollectionsconstituterange
extensionsforall 14species, includingfivespeciesnewlyrecordedfortheEleven PointRiverinMissouri
andnineupstream recordsforspeciespreviouslydocumentedintheMissourisectionoftheriver.The
collectionsare dominated byfourendemicOzarkian species [Fusconaia ozarkensis (Call), Lampsilis
reevianabrevicula (Call), Venustaconchapleasi(Marsh), and Ptychobranchus occidentalis (Conrad)],
twoofwhicharerare/uncommonin Missouri.Thereissignificantvariation inspeciescompositionalong
the 26 km section of river studied, which could be related to the inflow of numerous springs and a
considerabledownstreamincreaseinstreamdischarge.TheupperElevenPointRivermaybeasuitable
refuge for the conservation of Ozarkian mussel communities.
The Interior Highlands region of southern Missouri, landian musselfaunahasbeen depletedordestroyed in many
northern Arkansas, and eastern Oklahoma is an isolated areasduetotheeffectsof modern development (Bogan and
uplandcomprisedoftworugged physiographicprovinces,the Parmalee, 1983; Isom, 1969; Stansbery, 1970, 1971). The
Ozark Plateau and the Ouachita Mountains. Streams drain- Ozarkianfaunaissusceptibletothesamefate, and amajori-
ing this area are inhabited by many species of aquatic tyof its endemic taxa have alreadyappeared on lists of rare
organisms that live nowhere else. The list of endemic taxa andendangeredspecies(see HarrisandGordon, 1987; Nord-
includes at least 14 species of fish (Pflieger, 1975), seven strom er a/., 1977; Oesch, 1984).
gastropods (Gordon, 1980), and nine species of fresh-water ToexpandonarecentstatementbyHarrisand Gordon
mussels (cf. Gordon, 1980; Johnson, 1980; Oesch, 1984). (1987:54), there is an urgent need to better delineate the
Many mussel species endemic to the Interior High- distribution and biologyoffresh-water musselsthroughoutthe
lands are adapted to the clear, high-gradient streams with Interior Highlands region, especially for endemic Ozarkian
coarsebedmaterialthataretypicaloftheregion'sdrainages taxa with restricted environmental tolerances. This paper
(see Oesch, 1984; Warren, 1991). Because of their rather reportsapreliminarysurveyofUnionaceaintheupperEleven
limited habitat tolerances, these mussels can be highly Point River (White River Basin) in Oregon County, Missouri.
susceptibletotheeffectsofrecentecologicalchangesstem- Previous work in the White River Basin includes incidental
ming from pollution, excess siltation, and the damming of remarksbyCall (1895)and Utterback(1915-1916) intheirstate-
streams. The threat to these species is underscored by the wide synopses of the mussels of Arkansas and Missouri,
factthatthereareclearparallelsbetweentheOzarkianfaunal respectively. Zoogeographic studies include general surveys
province of the Interior Highlands and the Cumberlandian by Utterback(1917), Johnson (1980), and Gordonefal. (1980),
faunal provinceoftheCumberland Plateau region ofeastern which providelistsoftaxaatthescaleofthedrainage basin.
Kentucky and Tennessee (van der Schalie and van der Oesch (1984) mapsspecificdataon species locationsforthe
Schalie, 1950). Several of the endemic Ozarkian mussel central section ofthe Eleven Point River in Missouri, but his
species havecloselyrelatedcounterparts intheCumberland coveragedoesnotextend intotheupperreachesofthe river.
region. These pairs of species share not only a common The main objectives of the present study are to (1)
ancestry [e.g. Fusconaia ozarkansis (Call) and F. barnesiana document extant populations of mussel species in a 26 km
(Lea); see Johnson, 1980; Ortmann, 1917], but also a stretch ofthe upper Eleven Point River, and (2)describe the
preference for clear, energetic streams with coarse bed composition and geographical variation of mussel com-
materials. This parallel is important because the Cumber- munities in this area. The data have important implications
American Malacological Bulletin, Vol. 8(2) (1991):131-137
131
132 AMER. MALAC. BULL. 8(2) (1991)
Paty0/
Spring
CampHouse (19) 36*50-
Spring QgaCh3 QMcCormack
Cooper J Spring
> Spring
Minich
Spring
I/OSpring
sQPosySpring GreerSpring(j
Roaring Graham
Spring Spring
Eleven
Fig. 1. Map of collection areas (Reaches 1-3) along the upper Eleven Point River in Oregon County, Missouri.
for the conservation of rare and potentially endangered elevationdropsfromabout 189.6to 158.2mAMSLinthisarea,
Ozarkian species. and its gradient is relatively steep (1.2 m/km). The stream
channel consistsofaseriesofshallow riffles, raceways, and
MATERIALS AND METHODS deeper pools. Its current velocity varies from slow to swift,
and its substrate consists primarily of cobbles, gravel, and
The Eleven Point River is a clear, spring-fed Ozark some sand.
stream. Its headwaters are in Howell County, Missouri, near Seven majorspringsenterthe river inthestudyarea,
the town of Willow Springs. The river flows southeastward increasing its discharge considerably between Thomasville
acrosstheSalem Plateauforabout241 km beforejoiningthe andthe Highway 19 bridge. GreerSpring, thesecond largest
Spring River, atributaryoftheBlack River(White RiverBasin), spring in Missouri (Vineyard and Feder, 1974), enters the
in Randolph County, Arkansas (see Johnson and Beadles, Eleven Point River 0.6 km upstream from the Highway 19
1977). The Eleven Point River flows through a steeply bridge, where it reportedlytriplesthedischargeofthestream.
dissected karst landscape. Itsflood plain isoften narrow, and The spring had an average discharge of 9.55 m3/sec during
bluffs of Ordovician dolomite and sandstone tower up to its 68-year period of record (1922-1988; data from U. S.
129 m above the valley floor (see Bretz, 1965). Geological Survey, Rolla). Discharge data are not available
The Eleven Point Basin is mainly an agricultural area for the Eleven Point River above Greer Spring, although at
today,with pasturesonthe highplateausand lowflood plains, Bardley, Missouri, 26 km downstream from Greer, its
and oak-hickoryforestontheinterveningslopes. Farmswere dischargeaveraged21.66m3/secduringthe 1922-1988period
established along the river as early as 1819, but population of record (data from U. S. Geological Survey, Rolla).
density remained low until well after the Civil War (Sauer, Thedownstream increase in dischargehasapercep-
1920). Loggingbecamean important industryduringthelast tible effectonthe riverchannel (Fig. 2), andcould in turn be
quarterofthe 19thcentury, reaching itspeakabout 1900and relatedtovariation in mussel habitat. Betweentheupperand
declining thereafter. Deforestation probably increased rates lower ends of the study area, channel width increases from
of hillslope erosion in the area, but its historical impact on about 10to 22 m, channel depth increasesfrom about45to
thewaterqualityandgeomorphologyoftheEleven Point River >93cm, andcurrentvelocityincreasesfrom moderateorswift
is unknown. to very swift. (Channel dimensions were measured at
Thestudyareaisa26.4 kmstretchofthe Eleven Point raceways.) There could also be a downstream change in
Riverthat runsdownstream fromThomasville(State Highway substratum composition, but this has not been measured.
99) to the State Highway 19 bridge northeast of Greer (Fig. All musselsand mussel shellswerecollected byhand
1). Thisareacomprisesthe upperreachesofthe Eleven Point from gravel bars, riffles, and shallow areas along deeper
NationalWildandScenicRiver,whichwasestablished in 1968 raceways and pools (9-10 June 1990). The collection is a
and is maintained bythe MarkTwain National Forest. Stream "grab" samplethatwasnotobtained usingquantitativesampl-
WARREN: OZARKIAN MUSSELS 133
the Thomasville acess to a point below Posy Spring (0-5.6
km belowThomasville). Reach 2 is9.4km longand runsfrom
the Posy Spring localitytotheCane Bluffaccess(5.6-15.0 km
below Thomasville). Reach 3 runs 11.4 km from Cane Bluff
to the Highway 19 bridge (15.0-26.4 km below Thomasville).
Deadshellswereclassified byvalvecondition. 'Fresh
shells' arespecimenswiththe nacreand periostracum intact
and well-preserved. This category includes all paired valves
that were still joined at the dorsal ligament. 'Eroded shells'
have weathered, worn, or poorly preserved nacre and
periostracum. Some broken shells were included in this
category, but all retain the dorsal hinge line and are at least
half complete.
Specimens were identified using a comparative col-
lectionattheIllinoisState Museum, Springfield. Nomenclature
followsTurgeonefa/. (1988). All specimensarebeingcurated
at the Illinois State Museum.
RESULTS
Our collections in the upper Eleven Point River pro-
duced a total of 14 species of Unionacea (Table 1). All are
represented by live or fresh-dead individuals. Nine species
are upstream records for taxa previously documented by
Oesch (1984)at or belowthe Highway 19 bridge in Missouri,
includingElliptiodilatata (Rafinesque), Fusconaiaozarkensis,
Pleurobema coccineum (Conrad), Lampsilis cardium
50
/
40 S
Fig.2.TwoviewsoftheElevenPointRiver,OregonCounty,Missouri, // \.*
showing (a)the relativelysmall channel at the upper end of Reach // • \
1, looking downstream from below the Highway 99 bridge near //
Thomasville, and (b) the largerspring-fed channel atthe lowerend / • Fusconaia N
of Reach 3, lookingdownstreamfrom belowthe Highway 19bridge ozarkensis
near Greer (February, 1991). N Larmepesviilainsabrevicula
Venustaconcha
pleasi
ing techniques (cf. Miller and Payne, 1988). The sample is Plychobranchus
presumably representative of the relative abundance of + OtohcecirdeSnpteacliiess
various species, but it is not appropriate for estimating the
size, density, ordemographiccharacteristicsof local mussel
populations.
Most of the specimens collected were dead. Some
could have been residuesof muskrat predation, but manyap-
pearto havedied when theyweredislodged byflood waters A
and displaced outside of the river channel, where they -i
perished afterthe river returned to its banks. Water levels in Reach 1 Reach2 Reach3
theriverwereabout23-25cm higherthan normalatthetime Sample Areas
ofoursurveybecauseofunusuallyheavyspring rainfall, but
Fig. 3. Variation in the species composition offresh-water mussels
the water levels were receding.
inthreereachesoftheupper Eleven Point River, Missouri.Thefour
Live individuals were collected as one sample and Ozarkian species inthecollection(Fusconaia ozarkensis, Lampsilis
stored on ice. Dead individuals were collected from three reeviana brevicula, Venustaconchapleasi, and Ptychobranchus oc-
separate reachesofthe river(Fig. 1), cleaned, and storeddry. cidentalis)areplotted individually. All 10oftheothertaxain thecol-
Reach 1,thefarthest upstream, is5.6km long and runsfrom lection are Mississippian species.
134 AMER. MALAC. BULL. 8(2) (1991)
Table 1. Fresh-water mussels from the Upper Eleven Point River, Oregon County, Missouri.
Dead mussels
Reach 1 Reach 2 Reach 3
Live Percent
Taxon1 mussels Fresh Eroded Total Fresh Eroded Total Fresh Eroded Total Total Total
Anodonta imbecillis 0 0 0 1 1 0 .6
Say, 1829
Lasmigona costata 1 0 0 2 2 5 5.2
(Rafinesque, 1820)
Strophitus undulatus 1 2 2 0 0 0 1.9
(Say, 1817)
E///pf/o dilatata 0 0 0 0 0 5 3.2
(Rafinesque, 1820)
Fusconaia flava 0 0 0 2 2 0 1.3
(Rafinesque, 1820)
F. ozarkensis 5 8 9 2 3 6 23 14.8
(Call, 1887)
Pleurobema coccineum 1 0 0 0 1 5 7 4.5
(Conrad, 1834)
Lampsilis cardium 0 2 2 5 7 2 11 7.1
(Rafinesque, 1820)
L. reeviana brevicula 4 9 12 19 22 11 49 31.6
(Call, 1887)
L. siliquoidea 0 0 0 1 2 2 4 2.6
(Barnes, 1823)
Venustaconcha pleasi 5 15 16 1 1 0 22 14.2
(Marsh, 1891)
Villosa iris 0 2 3 0 0 1 4 2.6
(Lea, 1829)
V. lienosa 0 2 2 0 0 0 2 1.3
(Conrad, 1834)
Ptychobranchus occidentalis 2 0 1 5 7 4 14 9.0
(Conrad, 1836) 758 979
96
Number of individuals 19 40 7 47 38 10 48 32 9 41 155 9—9.9
Number of taxa 7 10 14
'Nomenclaturefollows Turgeon efal. (1988). Taxonomic ordering is phylogenetic above the genus level (after Davis and Fuller 1981:246).
(Rafinesque), L. reeviana brevicula (Call), Venustaconcha northern Arkansas (Gordon efal., 1984; Oesch, 1984; Utter-
pleasi (Marsh), Villosa iris (Lea), V. lienosa (Conrad), and back, 1917), and itwas not surprising to find them inthe up-
Ptychobranchus occidentalis (Conrad). Johnson (1980:133) per Eleven Point River. Corbicula fluminea (Mu'ller), the in-
lists an additional location for L. r. brevicula (as V. reeviana) trusive Asian clam, was noted in all three reaches but was
at Riverton. Of the live individuals in our collection, two F. not collected.
ozarkensis and three V. pleasi were gravid females. Thereisasignificantcorrelation betweenthespecies
Onlytwospeciesdocumented byOesch (1984) inthe countsofliveanddead individualsinthecollection(Pearson's
Eleven Point River are missing from our collections: r = .73; df = 12;p < .01; see Rock, 1988:168). Thistest in-
Cyclonaias tuberculata (Rafinesque) and Ligumia recta dicatesthatthetwosamplesare proportionatelyrepresenta-
(Lamarck). Oesch found C. tuberculata nearthe Highway 19 tiveofthesame population. Nevertheless, largequantitative
bridge, and recorded both species downstream near the collections from stratified sample areas would undoubtedly
Missouri-Arkansas border at Billmore, Missouri (Oesch provide more reliabledataonthespeciescompositionofex-
1984:117, 197). Theirabsence in ourcollectionscould bedue tant communities.
to sampling error, limited zoogeographic ranges, or both. Judgingfromtherelativefrequenciesofindividualsin
Thefiveremainingtaxaarenew recordsforthe Eleven the collection, the mussel community in the upper Eleven
Point Riverin Missouri. Thesespecies includeAnodontaim- Point River is dominated by four species. All are endemic
becillis Say, Lasmigona costata (Rafinesque), Strophitus un- Ozarkian taxa (Gordon, 1980; Johnson, 1980), and together
dulatus(Say),Fusconaiaflava(Rafinesque),andLampsilissili- they comprise 69.6% of the collection. In decreasing order
quoidea(Barnes). All ofthesespecieshavebeendocumented of abundance, these are Lampsilis r. brevicula (31.6%),
elsewhere inthe Black River Basinofsouthern Missouriand Fusconaia ozarkensis(14.8%), Venustaconchapleasi(14.2%),
WARREN: OZARKIAN MUSSELS 135
Table2. Geographical variation in thespeciescomposition anddiversityoffresh-water mussel com-
munities along the Upper Eleven Point River in Oregon County, Missouri.
Variable Reach 1 Reach 2 Reach 3
Leading dominant Venustaconcha Lampsilis Lampsilis
nidsc/ /trcrWaiId iccVlaiicl
breviculs brGviculs
OO IU Q
Individuals (N) 47 48 41
Percent Ozarkian 50.0 40.0 33.3
species (%sy
Percent Ozarkian 80.9 68.7 51.2
individuals 0/o/V)1
(
Simpson index of species .21 .25 .13
dominance (D)
Shannon index of species 1.69 1.73 2.02
richness {H')
1 Ozarkian species represented in the collection include Fusconaia ozarkensis, Lampsilis reeviana
brevicula, Venustaconchapleasi, andPtychobranchusoccidentalis(cf. Gordon 1980;Johnson 1980).
and Ptychobranchus occidentalis (9.0%). The remaining 1949)—a measureofdominanceconcentrationthatcorrelates
species are members of the Mississippian faunal province inversely with the evenness of species proportions—peaks
and have extensive ranges in the Mississippi River basin in Reach 2and is lowest in Reach 1. This pattern reflectsthe
(Johnson, 1980; Oesch, 1984). unusuallyhigh relativeabundanceofLampsilisr. brevicula in
There is significant geographical variation in the Reach 2andtherelatively uniform proportionsofvarioustaxa
species composition ofdead shells collected from thethree in Reach 3. The Shannon index (H'\ Shannon and Weaver,
sample reaches (Tables 1-2; Fig. 3). The three leading 1949)—ameasureofspeciesrichness(seeMagurran, 1988)—
dominants in Reach 1, the upstream section, are Venusta- increases monotonicallydownstreamfrom Reach 1 to Reach
concha pleasi (34.0%), Lampsilis r. brevicula (25.5%), and 3. Thistrend indicatesthat species diversity is relatively low
Fusconaiaozarkensis(19.1%). In Reach 2thereisasubstan- in upstreamareasdominated byOzarkiantaxa, but increases
tial drop in the abundance of V. pleasi (2.1%). The leading downstream whereMississippiantaxaarerelativelyabundant.
dominant in Reach 2 is L. r. brevicula (45.8%), followed by Itshould becautionedthatthesepatternsarebasedon rather
Ptychobranchusoccidentalis(14.6%)andL. cardium(14.6%). limited data, and additional fieldwork is needed to confirm
L. r. brevicula is also the leading dominant in Reach 3, the their validity.
downstream section, although its relative abundance drops
to only 26.8%. The second leading dominant in Reach 3 is DISCUSSION AND CONCLUSIONS
F. ozarkensis(14.6%), followed byL. costata, Elliptiodilatata,
and P. coccineum at 12.2% each. In a discussion of the prospects of rare and en-
Geographical variation in species composition is ac- dangered fresh-water mussels in Arkansas, Harris and Gor-
companied by substantial downstream decreases in the don (1987) suggest that certain sections of the Eleven Point
relativeabundanceofOzarkianelementsandcorresponding Riverand severalotherstreams mayoffersuitable habitatfor
increasesin Mississippianelements(Table2; Fig.3). Ozarkian sustaining endangered species. However, in an assessment
taxa comprise 50% of the species documented in Reach 1, of the remaining habitat available to Venustaconcha pleasi,
40% in Reach 2, and 33% of the species in Reach 3. There Oesch (1984:153)remarksthat mostofthe Eleven Point River
isaparalleldeclineintherelativeabundanceofOzarkian in- offers only "marginal habitat" because of its manytributary
dividuals, although the curve is even steeper. Ozarkian springs. Oesch (1984:229)suggestselsewherethatwaterfrom
species account for more than 80% of individuals in Reach largesprings istoocold and nutrient-poorforthesurvival of
1, butonlyabout69% in Reach2and51% in Reach3. These most mussel species. In a similarvein, Buchanan (1984:85)
trends could reflect either a downstream decrease in the states that cold springs tend to reduce the abundance and
density of Ozarkian species, an upstream decrease in the species diversity of mussels in the Current River basin, the
density of Mississippian taxa, or both. next drainage east of the Eleven Point Basin.
There also appears to be geographical variation in Despite these suggestions, our collections indicate
speciesdiversity(Table2). Althoughthe numbersofspecies there is a significant community of mussels in the upper
(S) and individuals (AO are fairly constant among reaches, reaches of the Eleven Point River, where spring water ac-
therearediscerniblepatternsinindexesofspeciesdominance countsformuchofthe river'sdischarge. It istruethatthetotal
and species richness. The Simpson index (D; Simpson, numberof known species (14) is low in comparison with the
136 AMER. MALAC. BULL. 8(2) (1991)
Spring River, Black River, andotherlargestreams intheWhite ACKNOWLEDGMENTS
River Basin (see Gordon, 1982; Gordon ef a/., 1984; Utter-
back, 1917). However, the Eleven Point Riverapparentlypro- I thank C. E. Colten, J. A. Ferguson, S. McGuire, R. B.
vides suitable habitat for four endemic Ozarkian species McMillan, S. K. Santure,and K. B.Tankersleyfortheirhelpwithcol-
(Fusconaia ozarkensis, Lampsilis r. brevicula, Venustaconcha lectionsinthefield. IamgratefultoR.D.Oeschforconfirmingseveral
pleasi, Ptychobranchusoccidentalis), whichtogethercomprise species identifications. D. Figg, ofthe Missouri DepartmentofCon-
almost 70% of the individuals collected. Moreover, three of servation, kindly provided information on rare and endangered
thesespecies haveappearedon stateornational listsofrare sinpeRcoilelas,inMiMsissosuoruir,i.foIrthsaunpkplSy.inSgtedrinsecshoafrtgheeaUn.dS.gaGegoel-ohgeiicgahltSduartav.ey
and endangered fresh-water mussels (F. ozarkensis [Nord- wouldalsoliketothankA. E. Bogan,J. A. Ferguson, R. B. McMillan,I
strom ef a/., 1977]; V. pleasi [Nordstrom ef a/., 1977]; P. oc- J. R. Purdue, R. D. Oesch, B. W. Styles, M. D. Wiant, and two
cidentalis [Stansbery, 1971]). None is currently on federal or anonymous reviewers for comments on the manuscript.
state listsofprotectedspecies(FishandWildlifeService, 1989;
Missouri DepartmentofConservation, 1986), but F. ozarken-
sisand V.pleasiare rare/uncommon in Missouri (Dennis Figg, LITERATURE CITED
pers. comm., 1990).
There is significant downstream variation in species Bogan, A. E. and P. W. Parmalee. 1983. Tennessee's Rare Wildlife,
composition in thestudyarea, which could be related to the VolumeII: TheMollusks. TennesseeWildlifeResourcesAgency,
inflow of numerous springs and a considerable increase in Nashville. 123 pp.
stream discharge. The abundance of Venustaconcha Bretz, J. H. 1965. Geomorphic History of the Ozarks of Missouri.
pleasi in the upstream sample area (Reach 1) suggests it is Missouri Geological Survey and Water Resources, Rolla.
primarily a headwater species that could be most common Buchanan,A. C. 1984. NaiadesoftheCurrentRiverBasin, Missouri.
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documented elsewhere, but ourobservations are consistent actions of the Academy of Science ofSt. Louis 7:1-65.
with Gordon's (1982) qualitative study of the White River in Davis, G. M. and S. L. H. Fuller. 1981. Genetic relationshipsamong
Arkansas, where V. pleasi is restricted to the upper reaches recent Unionacea (Bivalvia) of North America. Malacologia
of the stream above Fayetteville. Lampsilis r. brevicula is the 20:217-253.
most abundantspecies inthe middleand lowersampleareas FishandWildlifeService. 1989. Endangeredandthreatenedwildlife
(Reaches 2-3), where most ofthe tributary springsenterthe and plants; animal notice of review. Federal Register
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unusually tolerant of streams below the outlets of major tosystematicsand zoogeography. ProceedingsoftheArkan-
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dance, with peaks in the upper and lower sample areas Missouri. Southwestern Naturalist 27:347-352.
(Reaches 1 &3), while Ptychobranchusoccidentalis parallels Gordon, M. E., P. A. Durkee, H. M. Runke, and H. J. Zimmerman.
thedistributionofL. r. breviculawithapeakinthemiddlesam- 1984. MusselFaunaofthe BlackandSpringRiversin North-
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positional patterns is questionable. Other taxa, all of which Gordon, M. E., L. R. Kraemer, and A. V. Brown. 1980. Unionaceaof
are Mississippian species, tend to increase monotonically Arkansas: historical review, checklist, and observations on
downstream. distributionalpatterns.BulletinoftheAmericanMalacological
There is a downstream increase in species diversity Union 1979:31-37.
in the study area that correlates inversely with downstream Harris,aJn.dL. aennddaMn.geE.reGdordmouns.se19l8s7. (DMisotlrliubsuctai:on aMnadrgasrtiattuisfeorfidraaer,e
decreases in thequalitative and apparent quantitativeabun- Unionidae)inArkansas.ProceedingsoftheArkansasAcademy
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tolerances and reproductive systems in greater detail. The Princeton University Press, Princeton. 179 pp.
section of river discussed here is currently being protected Miller, A. C. and B. S. Payne. 1988.Theneedforquantitativesampl-
in accordancewiththe National Wild and Scenic RiversAct, ingtocharacterizesizedemographyanddensityoffreshwater
and it appearsto provide appropriate habitatforfosteringthe musselcommunities.AmericanMalacologicalBulletin6:49-54.
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WARREN: OZARKIAN MUSSELS 137
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