necks on theirpopulations. However, it islikelythat used(Krueger et al.1981). T h esinglestudy ofgene
the paucity ofgeneticdiversity and shallowgenetic flow in anacipenseridsuggeststhathatchery-based
differentiationamongpopulations of the twofresh- restocking may be necessary to reestablish sturgeon
waterspecies is at leastpartly due to a combination populations in a reasonablelength of time indrain-
of Pleistocene bottlenecks and recent recoloniza- ageswhere theyare extinct.That is, ifgeneflow es-
tion of northern waters, prolonged generation timatesamong populations ofA. o. desotoiare in-
times leading to lowmutation rates, and continued dicative ofgenerallevels ofstraying foracipenser-
geneflowamongpopulationsthatremainlargely rids,thenstrayingrateslessthan 1.0 pergeneration.
linked through theirinhabitation of fewdiscrete combinedwith thelonggenerationtimes of stur-
drainages. Although theanadromoussturgeons of geons,meansthat naturalrestocking mayrequire
North Americawere notexempt fromglacialinflu- decadesbefore it even is initiated,notwithstanding
ences, post-Pleistocene geneticdiversity wasmain- additionaldecadesnecessary for population growth
tained,except in farnortherndrainages recolonized (Boreman 1997 thisvolume). Circumstantial evi-
byA. oxyrinchus. dence forextremelyslowrates of naturalrestocking
Geneticanalyses todate of thefreshwater sca- through straying is provided by theexample of the
phirhynchids showvery limitedgenetic variation, Maryland tributaries of ChesapeakeBay, where
consistentwithP. spathulaandA. fulvescens– spe- there has been noindication of recolonization byA.
ciesthat arelargelysympatricwithS. albusandS. oxyrinchusover manydecades inriversthatonce
platorynchus.Low genetic variationwithinScaphir- supportedlargepopulations(David Secorpersonal
hynchusis in accordancewith pre-existingbiogeo- communication).
graphic theoriessuggestingrecent speciationwith However, a generic problemwith thehatchery
Wisconsinian glacialevents (70 000 to 10 000years production of sturgeons is theneed toacquiresuffi-
before present). However, thetaxonomicbounda- cientbroodstock to prevent inbreeding(Nelson &
ries among thethreeputativescaphirhynchid spe- Soul61987).Commonlyaccepted guidelines forfish
ciesremainunclear. but ofgreat importance totheir production arc for aneffectivepopulationsize of
conservationstatus under the U.S. Endangered 100 ormoreindividuals(Kincaid1983, Kapuscinski
Species Act(ESA).Futuremolecular analyses of & Lannan1986,Allendorf & Ryman 1987).But, giv-
Scaphirhynchusspp. andotherNorth American enthe generallylargesize andscarcity ofsturgeons.
acipenserifomswill notonlyattempt toassess ti-a- annual hatchery reproduction at these effective
ditional taxonomicdivisionssuch asspecies and populationlevels areunrealistic formostrestora-
subspecies, butalsotheirEvolutionarilySignificant tioneffortsaimedtowardsinglestocks. If lower
Units as mandatedunder theEndangeredSpecies thanrecommended numbers of broodstockmust be
Act (Waples1995). used, one way toreduce inbreedingwould be to use
Molecular analyses todatealso arerelevant to genetic screening ofinviduals With the data from
consvervation efforts involving hatchery-based theseanalyses,hatcherycrosses can beoptimized to
stocking (St.Pierre^7 ). Anadromoussturgeonsshow maximizediversity and yetstillmaintain stock-spe-
stock structure, implying that interpopulation cificgene frequencies. We envisionthat apriori
transferswillhave genetic repercussions; to maxi- knowledge of the genetic composition ofbrood-
mize thelikelihoodthat stockedfishwillhavehigh stock canhelp ease the burden ofrigorousdemands
fitness for a particularenvironment,broodstock forlargenumbers ofbroodstock.
from the same environment as wild fish should be Rapidtechnicaladvances in thedevelopment of
molecular biological approaches will allow for their
routineapplication in thefuture to problems of the
conservation ofsturgeons andpaddlefishes. It is
now possible toobtain DNAsequenceinformation
from non-destructively obtainedtissues such as
barbels, finclips, orblood, fromearlylifeintervals
(^7) St. Pierre, R.A. 1996. Breeding and stocking protocol for cultu-
red Atlanticsturgeon.FinalReport fromthe AtlanticSturgeon
aquaculture andStockingCommittee to theAtlantic States Ma-
rineFisheries Commission Atlantic Sturgeon Management
Board. 17 pp.