Figure 2.Gulf of Mexico riversfromwhichspecimens ofAcipenseroxyrinchuswereobtained.served. TheSuwanneeRiverpopulation hasbeen lowrivers, (4)Choctawhatchee River, and (5) Apa-
extensivelystudied over thepastdecade and prob- lachicola,Ochlockonee. andSuwanneerivers.These
ablycontains thelargestpopulation of sturgeon results suggest strong reproductive isolation of A. o.
along the Gulf of Mexico. Miracle & Campton desotoistocks on at least a regionalbasis, andpoint
(1995)examined the extent ofgenetic variation in to theinadvisibility of mixing ofhatchery-reared
sturgeon from the SuwanneeRiver todetermine if progeny ofbroodstockfroindifferentGulfrivers.
its population constituted asinglehomogeneous Also, we used RFLP analysis of mtDNA with five
unit. Sequenceanalysis of 268 basepairs of ahighly diagnostic restriction enzymes tocharacterize the
variablearea of themtDNAcontrolregion did not stockstructure of populations ofA. o. oxyrinchus
reveal significant genetic heterogeneity among along the Atlantic coast, including the St.Lawrence
sturgeonfromdifferent sampling locations. River, Quebec; St. JohnRiver. NewBrunswick;
We used RFLP and sequencing analysis of Hudson River, New York; Edisto River. South Car-
mtDNA to assess the stock structuring of A. o. des- olina; andFourrivers inGeorgia; theAltamaha,
otoipopulations amongeight drainages (Figure 2) Ogeechee,Savannah, andSatilla(Waldman et al.
extendingfrom theMississippiRiver to the Suwan- 1996a, b). Chi-squareanalysisshowed theeight
nee River(Stabile et al.1996).RFLPanalysis using populationscould be grouped as threehighlydiffer-
fourdiagnostic restriction enzymes yieldedeight entiated (p <0.0001)stocks: (1)Canadian(St. Law-
composite haplotypes; genotypicdiversity indices renee and St.Johnrivers): (2)HudsonRiver; and
(Nei &Tajimia1981)rangedbetween0.173 for the (3)southeastern (Edisto, Savannah, Ogeechee, Al-
ChoctawhatcheeRiversample to0.732 for the Yel- tamaha, and Satilla). Composite haplotypes
low Rivercollection.Significantdifferences (p < showed a clearcline ingenotypicdiversity indices
0.05) inhaplotypefrequencesindicated substantial (Nei &Tajima1981)among populationsthatranged
geographic structuring of sturgeonpopulations; re- from complete monomorphism(0.0) of the two
sultsfrom theRFLP (N =164) andsequence (N = Canadian populations toconsiderable polymor-
141)analyseswerelargelycongruent (Figure 3). phismamongsoutheasternpopulations(e.g.,Edis-
Five regional orriver-specificstockswereidenfied toRiver:0.646;Ogeechee River:0.750). Alatitudi-
(fromwest to east): (1)LakePonchartrainandPearl nalcline ingenotypicdiversityalong the Atlantic
River, (2) PascagoulaRiver, (3)Escambia and Yel- coast is consistent with founder effects among