51813_Sturgeon biodioversity an.PDF

Figure I .Relationship betweenfishingmortalityrate (F) and Figure 2.Effects of an increase in thecurrentmortalityrate ( Z )
correspondingpercentage of themaximumlifetime egg produc- of age 1 and older females on the correspondingpercentage of
tion of anage 1 femalewhen F = 0 forwhite sturgeon in the Co- the maximum lifetime egg production of an age 1 female for
lumbia River belowBonneville Dam and Atlantic sturgeon in shortnose sturgeon in the lower Connecticut River and paddle-
the HudsonRiver. fish inLakePonchartrain.

apply to potential lifetime egg production per minimumlevel of20%. An estimate of the current
recruit (EPR). fishingmortalityrate forAtlantic sturgeon in the
The fishingmortalityratecorresponding to 20% HudsonRiver isunavailable.
ofEPRmaxfor whitesturgeon in thelower Columbia Mortality due to incidentalcapture inindirect
River and forAtlantic sturgeon inthe Hudson Riv- fisheries isprobablyincorporated in the current es-
er isF= 0.14(Figure 1 ). A 50%level ofEPRmax timates oftotalmortality ( Z )for both theshortnose
would beachieved if thefishingmortality isF= 0.06 sturgeon population in thelower ConnecticutRiver
for whitesturgeon, andF= 0.05 forAtlanticstur- and the paddlefishpopulation inLakePonchar-
geon. At the 1986 - 1990 averagefishingmortality train.Increasing the total mortalityrate on age 1
rate of F = 0.37,lifetime egg production of ageIfe- and older shortnose sturgeonfrom Z = 0.12(cur-
males in the whitesturgeonpopulation is approxi- rent) to Z =0.16 willreduce potentiallifetime egg
mately2% ofEPRmax–farbelow therecommended production of a female recruit to 50% ofEPRmax'

Table I .Femalelifehistory characteristics forwhitesturgeon in thelowerColumbia River, Atlantic sturgeon in theHudsonRiver,

shortnose sturgeon in thelower Connecticut River,paddlefish inLake Ponchartrain,stripedbass in theHudson River,winter flounder in

Cape CodBay, and bluefishalong theAtlanticcoast.

Characteristic White Atlantic Shortnose Paddlefish Stripedbass Winter Bluefish

sturgeon sturgeon sturgeon flounder

Maximum age (years) 104 60 30 20 18 12 8

Length(cm) at oldest age 309 343 91 120 105 45 89

Fecundity at oldest age 1 500000 1 800000 66000 200 000 3100000 2200000 5300000

Naturalmortality (M) 0.09 0.07 0.12 0.30 0.15 0.35 0.25

Age at firstmaturity (years) 16 11 5 9 3 2 2

Age at fullmaturity (years) 35 21 17 10 9 6 3

spawnings 33 3 2 11 1

Age at 50+% EPRmax(years) 37 29 17 11 1 1 6 3

Ages infishery 14 - 25 14+ 2+ 2+

Yearsbetweensuccessive

Fishingmortality (F) 0.37? 0 0 0.39 1.07 0.80

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