(Waldman et al.1996).Consequently,latejuvenile
Atlantic sturgeon from the HudsonRiver may an-
nually use otherriverine habitats during warm
monthsbeforereturning to the Hudson forspawn-
ing.
first fewyears oflife. Ingeneral,sturgeon are char-
acterized as indiscriminatebottom-reedingcarni-
vores, and specificinformation on dietindicates
they feed ongenerally thesamefooditems in the
HudsonRiver.Bothsturgeon have complex migra-
torypatterns in theHudsonRiverwithdistinct, sea-
sonal. and predictableconcentrationareas.Finally,
Discussion bothsturgeonsprimarily usedeepchannel habitats
for all lifeintervals.
Sturgeon(familyAcipenseridae) are the modern Despitemany similarities inlifehistory.Atlantic
descendants of the original ray-finned fish that and shortnose sturgeons differ in someobvious
achievedgreatest abundance anddiversity 280 to ways.Adultsizes aregreatly different, and thesizes
345 millionyears ago. Atlantic,shortnose, and all andages atmaturitydiverge. The timing andloca-
othersturgeon retainmany ancestralbodycharac- tion ofspawning is sodiffrentthat itappears im-
teristics andways of livingthatdistinguishthem as possiblethat the twospeciesbehaviorallyinteract
relictfishes(seeBemis et al. 1997 thisvolume). duringthis keylifeinterval. Use ofmarine habitats
AmongNorth Americanfishes,sturgeonsexhibit a andlong-distance coastal migrations are restricted
uniquecombination oflifehistoryattributes: ad- to Atlantic sturgeon.Withrespect tomanagement,
vanced age andlargesize atmaturity,eggsthat are onespecies isheavilyexploitedwhile theother is
numerous andsmall inrelation tobodysize, and fullyprotected under the USEndangeredSpecies
spawningthat isepisodic and seasonal (Winemiller Act.
& Rose1992).Beyond being unique,thesecharac- Widespread occurrence ofAtlantic and short-
teristicsmake sturgeonespeciallyvulnerable to nosesturgeons in manyAtlanticCoastrivers of
populationcollapse due to overfishing(Boreman NorthAmericaraisesquestions as to how two spe-
1997 thisvolume).Life historyinformation on the cies can co-existwith somanysharedlifehistory at-
HudsonRiversturgeonsfitsthesegeneralizations tributes. Theprevailingview(e.g., Dadswell et al.^5 ,
and it substantiates the need tocarefullyconserve Dovel et al.1992,Kieffer & Kynard1993) hasbeen
thesespecies. Inaddition,lifehistory detailssuch as that the twospecies are spatiallysegregated in riv-
seasonal areas ofconcentration, migration times ers inassociationwithsalinity;withshortnosestur-
and routes, andspecificspawning locationshigh- geonoriented tofreshwater, and Atlanticsturgeon
light thevulnerability of bothshortnose and Atlan- concentrated inbrackishwaterexcept at spawning
tic sturgeon toeasyexploitation andhabitatdisrup- and veryearlylife.However, areview of themove-
tion. Fortunately, in thecase of theHudsonRiver ments andhabitat use o fbothspecies in theHudson
estuary, key habitats for spawning, rearing, and Riverestuaryconflicts withtheseinterpretations.
overwintering are intact and suitable for the spe- Juvenileshortnosesturgeon andearly juvenile
cies.Also, bothspecies ofsturgeon are managed Atlanticsturgeonhavevirtuallyidentical distribu-
through either endangered species protection tions in theHudsonRiverestuaryduring all sea-
(shortnose sturgeon; US EndangeredSpeciesAct) sons. Duringthisperiod of co-occurrence,both spe-
or fisheryrestrictions (Smith &Clugston 1997this cies are verysimilar insize,grow atabout thesame
volume),eventhough thelatter may not be ade- rate,feed on similarfoods: and sharedeepchannel
quate tosustain thecurrent population(Young et habitats. Furthermore, the distribution of adult
al. 1988, Boreman 1997 thisvolume). shortnosesturgeonoverlapswiththat ofjuvenile
The two sturgeons in the HudsonRivershare Atlanticsturgeon.Interestingly, the period of river
manycommon lifehistoryattributes. Both arelong- emigration of juvenile Atlantic sturgeonclosely
lived andmature atadvanced agecompared to al correspondswith the age(intermediatejuveniles in
most allotherfishes in theHudsonRiver.Both spe- Table 1) whentheyreach asize(ca. 55 cm TL)equal
cieshave rapid andsimilargrowthratesduring the to the minimum adultsize ofshortnosesturgeon.