sturgeonlife history.Sturgeon areuniquelyadapt- variety of prey and switch as prey availability
ed to the large mainstemriver systemsuponwhich changes.Thesefish canalso withstand long periods
all speciesrelyduring all orpart oftheirlife cycle ofstarvationduringperiods oflow foodavailability
(Rochard et al.1990).Rivers includediverse hab- or spawningmigrations (Dadswell1979,Mason &
itatswhich aredistributed in largescalepatterns Clugston1993).Sturgeon generally feed oninver-
corresponding to the surrounding topography. Typ- tebrates in thebenthic foodchain(Held1969, Dad-
icaltransitions includeheadwatersthrough tribu- swell1979,Carlson et al.1985,Sandilands1987,
taries.mainstem, andestuaryinto an ocean, sea, or McCabe et al.1993)wheremostproductionoccurs
large lake. In largebasins, rivers maytraverse many in largeriver systems(Sheehan &Rasmussen 1993).
different regions andclimatic zones. Rivers are also Fish mayalso be animportantdietcomponent of
extremely dynamichabitats featuringlarge season- some sturgeonspecies(Semakula & Larkin1968).
al and annualvariations inphysicalconditions and Large sturgeon can consume largeprey.Pursuit and
resourceavailability(Sheehan &Rasmussen 1993). capture ofactivepreybelie animage ofsturgeon as
Seasonalcycles inweather andrunoffdrive changes sluggishbottomscavengers.
in velocity.morphometry, temperature, substrate, Populations ofsturgeon arebuffered from an-
and turbidity.Conditionsvaryfrom year to year in nualvariation inenvironmentalconditions by de-
unpredictablepatternsbased on regionalweather layedmaturation,longevity, andhighindividual fe-
patterns.Periodic floods anddroughts mayradical- cundity. Delayed maturation (Roussow 1957,
ly alter theriverineenvironment.Distribution and Sunde1961,Dadswell1979,Conte et al.^2 , Chapman
abundance ofmany species of fishes andother orga- 1989,Guenette et al.1992, Keenlyne & Jenkins
nisms vary widely inresponse tospatial andtempo- 1993)speeds growth to largesizes asenergy is de-
ral patterns. Forinstance,anadromousfishes are voted to somaticratherthangonadaldevelopment.
seasonallyabundant asthey move betweenspawn- Largesize helpsreducepredation.loweringnatural
ing and feedingareas inportions of manytemperate mortalityrate andincreasing longevity.A longlife-
rivers andestuaries. span(Pycha 1956.Wilson 1987,Rien &Beamesder-
Sturgeonhaveevolvedlifehistory characteristics fer1994) allows fishnumerous opportunities to
whichallowthem to thrivein these large,diverse. spawn andreducesthe need tospawn inyears when
and dynamicriversystems. Individualsoftenrange conditions are not suitable.Manyspecieshave been
widely totakeadvantage ofscattered and season- observed toresorb eggs underthese conditions
allyabundant resources. Regularmigrations for (Artyukhin et al.1979,Chapman1989).High fecun-
spawning andshort-termmovements for feeding dityassociatedwithlargesizeimproves spawning
havebeenobserved formany species (Chadwick success inyearswhensuitable conditions are en-
1959,Miller1972a,Haynes et al.1978,Haynes & countered.
Gray1981,Smith1985,Wooley &Crateau1985, Manysturgeonspeciesdepend onfree-flowing
Sandilands1987, Kempinger 1988,Odenkirk1989, rivers and seasonal floods to provide suitable
Hall et al.1991,Mosindy &Rusak^1 , O’Herron et al. spawning conditions. Adhesiveeggs are typically
1993).Many species areeuryhaline andmovefreely broadcast overrockysubstrates inturbulent.high-
betweenfreshwater, estuaries, and saltwater (Ro- velocityareas duringhighspringrunoff(Magnin
chard et al.1990) tofurther broadentheir resource 1966,Buckley & Kynard1985,Smith1985, Kemp-
base. Long-distance movements are facilitated by inger1988,Hall et al.1991,Mosindy &Rusak1, La-
theirlargesize,shape, andswimming abilitywhich Haye et al.1992,Parsley et al.1993).Recruitment
allowthem tomovethroughheavycurrent.
Sturgeon areopportunistic predators that eat a 2 ,
Conte,F.S.,S.I.Doroshov &P.B.Lutes.1988. Hatcherymanual
for the whitesturgeonAcipensertransmontanusRichardson
withapplication tootherNorth AmericanAcipenseridae. Uni-
versity ofCaliforniaCooperative ExtensionPublication3322.
104 pp.
(^1) Mosindy, T. & J.Rusak.1991. A nassesment oflake sturgeon
populations in Lake of theWoods and theRainyRiver1987–90
OntarioMinistry ofNaturalResources 66 pp.