microhabitatdiversity, andturbidwaters). Thesechanges havealsoreduced thenatural foragebase of thepallidsturgeon, anotherlikely
reason for its decline.Purportedcases ofhybridizationwith theshovelnose sturgeon (incidentally or intentionally occurring) mayalso be
detrimental to the pallid sturgeon populations. Conservation action:This species was listed as endangered by the U.S. Fish and Wildlife
Service on 6September 1990 (FederalRegister1990). Apanel ofscientists hasbeen assembled to serve as an advisorygroup for the
recovery ofthisspecies; they have developed a recovery planthat mapeventually lead todownlisting the pallidsturgeon (Dryer &
Sandvol1993). Themajor elements in the recovery of thespeciesinclude establishingthreewild-caught broodstock populations in
different hatcheries; captive breeding.propagation, andstocking;protection ofwildindividuals; andhabitat restoration indesignated
areas of the Missouri and lower Mississippi rivers. Conservation recommendation:Restoration of natural habitat and migratory patterns
are essential. The historichabitats in theMissouri andlowerMississippi riversmust berestored insections ofthesesystems toprovide
appropriatemicrohabitats forpallidsturgeonforaging, spawning, and migration.Naturalmigratorypatterns may bereestablished for the
pallidsturgeonwith thedevelopment of novel structures associatedwithdams thatassist this speciess andotherswith overcoming these
barriers.Remarks:Considerable interestexists as towhether thepallid andshovelnosesturgeon are diferentspecies.Much of this
concern stemsfrom thegenetic study by Phelps & Allendorf(1983)wherein ‘hybrid’ andparental sturgeonwere examined and no genetic
differences weredetected for thesespecies at 37loci.This study is technically and theoreticallyflawed andshould not beused aseither a
basis for theexistence of hybridization betweenthese sturgeonspecies or for determininggeneticvariation eitherwithin orbetween these
species.Theirstudy employed buffer mediastandard forsalmonidfishes,did not provide anadequateexamination ofdifferingenvi-
ronmentalconditions forelectrophoreticexamination ofproteinvariation, and did notdemonstrate anyempirical evidence for the
existence ofpurportedhybrids between these species.Unfortunately,because of the above study andthat byCarlson et al.(1985),some
biologists andlaypersons have preconceived notionsthathybridizationbetween thepallid andshovelnose sturgeon is common in the
wild.However,there is noempirical evidence tosupportthispremise. To the contrary, in addition to these speciespossessingdifferent
geographic distributions,there are abundantmorphological, behavioral andecologicalattributes that may beused to distinguishthese
species.
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