•.
Ret: No. [UlACEES]CBL 96-138
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Not
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to he cite{J withoitt prior refe~erice io the aufhol';,
international Councii fcr
the Exploration cf the Sea
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C.M. 19951T: 11
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, Aß:idroD1OuS arid Catadromous Fish Corriri'littee
Ariadromaus :Ü1d Catadromaus Fish Restaratian Progcimmes
.' A Time far Evaluatia'ri (T)
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Jj' c.
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USE OF LARVAL
STOCKING IN RESTORAnON
OF
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PEUGIC-SPAWNING ANADROMOUS FISHES
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by
.~, DaVid H. Secor arid 1:.D. Haude
•. ~. 'The University of~larid SyStem . '
Center far EIiVirOiimeriw and Esniarine Studies
Chesape:tke Biological Laboratory
Post Office Box 38 ' .
Salonions, MD 20688~03 8USA
ABSTRACT
,'. The AiIaritie eciiist p.opui~Hon ofstnped bassMoronesaxatilis collapsed in th~ late 1970s~
PI:?graInS arid release e.~erimeniS Wefe inStituted to eva!uate the potential to resiere Striped
Hatch~J
bäSs iri CheS<ipeake Bay. Because,surVival ofstiipedbass larvae te first feeding (7 days after hateh)
is low, ranging fromO.2% to 5.2%, itmay be feasible to' enhanee surnv3.I througlll1atehery
propagation of eggs and yolk-sa.: larvae, lind to supplement recrWtmerit by, stockirig post-yalk-sac
larvae. During 1991-1993, otoliths 001.7 niillion hatcheiy-produeed striped baSs larvae (5~13 days
after hateh) ,were ch~miically marked and released into tWo trlbuiarles of the Chesapeake Bäy. ~
Ye:l1'S.~fmodernte to paarnaturnI suMval (199~; 1992), Stoc~ed larvae coriiributed substantially (20
to 30%) to overall juvenile abundanee. Iri 1993, a year ofhigh natUral prciduetiori, stocked larvae
contributed oniy 5~ to juvenile abuiidance, although numbers contnbuted were, higher than in
previous years. Usirig field and hatehery estimates oflarval and juvenile groWth and mortalitY, we
eantriiSteci enharicemerit straiegies iri whiCh fish were reIeased a.t thfee different ages: larvae (7 days
after hateh), Phase I juveriiles (55 days after Mic.h), cr, Phase, II juveniles (220 days :ifter hateh).
'Coholt biomass'aceumulation was highest when Phase I juveniles were stocked. Hatchery-reared
juveniles e.,,<penenced substantially higher rätes of grOwth and stirvival thari did wild juveniles of '
similar age. When appraximate costs were ineofporated intc the analysis, the effieacy af larV:ll
stacking to increase cahort biamass waS approximiltely, equivillent ta stocking Phase I juveniles.
During yearS ofpeor recruitment larval stockirig iri esttianne tributarles eould supplement stacks of
striped bass and other anadramous species which e.,,<penence high embryo arid yalk-sac hirVa
martalitY.
.
KeyWords: anadromy, hatchery stocking, larval stocking, otolith, recruitment, striped bass.
D. Secor ~l1d E. Hvrit./.e: Cht!sapeake J3io!ogicaILahoratoo', Solomolls.. lvfD 20688 USA [tel: -lio326-i2:'9. fax.~ -110-326-7318. e-/11ail secoT1l'chl.cee.'i.edll (ehollde~gchl.cees.l!dll) ]
fNTRODUCTION
Strioed Bass Restoration
Large reduCrions iri landings ofstnped hasS Marone saxati/is arid deciines in recruitineIii ·(Fig.
1) prompted a restoration prograin in the Chesapeake Bay (ASMFC 1995). Tagging and genetic
smdies had showri that Chesapeake Bay is the major nursery are:i arid sow-ce cf recruits to cOaStal
fisheries in the mid-Atlaritic region ofNorth Ariienea (Boremanarid Lewis '1987~ Fabrizio 1987~
wtrgin et al. 1993)., High rätes ofexploitation on preIrugratery juve~Ies (2 >2.0 yr.l; Gibson 1993)
throiighout the 1970s and degraded nursery habitats (Hall et al. 1993) were beHeved to have led to
recruitment faiIure iri Chesapeake Bay. One oftWo pnricipal responses by management to restere
striped bass was ci h~ltehery-based stockirig progrnm. Fr0in 1985-1993, 1.4 million ~'Phase 1"
juveniles (35~50 mm., totallen~h [TL]) arid 6.1 rilillion "PhaSe II" juveniles (150 t6 200 mm TL)
were Stocked irito. seveI-al Chesapeake Bäy tn"bUtanes (Fig. 2): The other -response was to unpose
moratoria in Maryland (1985-1989) and Viiginii (1989). arid reSi:rici e..q,loitation in coastal waters
(ASMFC 1995).
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The rationale for hatchery-based r6stciriition was based upon Sriidies that indicated: 1) high
mortality rates of eggs and larvae in nUrSery habitats; arid 2) stiong enVir6nmental effects on striped
bass recruionent (e.g. Ulanowicz arid Polgar 1980). Iri two Chesapeake tributaries, recent estimates
oflarval monali.ty to firSi ,feeding(ca.5 daysafter hciich) rariged from 9.4.8: 99.8%; larval mortal!tY
froin first-feeding to ca. 8 riun staridard length raiiged from 91.6 ~ 94.8% (Secor arid Houde 1995a;
Ke1logg et al.. 1996).· '.,
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Low Strlped bass larval survivorship in degriided nursery habitats w~ proposed by Hall et al. .
(1993) as the "acidification hypothesis." Laboriiiciiy' ärid in siiu srildies in several iribütaries of .
Chesapeake Bay indieated thai acid fain depressed pH in riursery habitats and mobiÜzed taXie metals, .
at concemratioris lethäl to striped bass larvae. Alternatively, ichthyoplankton studies demonstrated
!hat metereological1y driven Varlability iri water cluaIity (temperattire, pR, eonductivitY)
dominant'
infIuences on egg arid larval survival and juveiille production (Uphaff 1989~ Ruihenord ~d HOtide.
1995~ Secor arid Houde 1995a; Kellogg et al. 1996). Thus, if sUrVival of embryos, arid sUrnvaI arid '.
gro\l;th oflarvae, were high in hatcheries~ theri l'eIeased juveniles would have bypassed a ticittleneck
of criticm mortality, whether caused by degriided riursery habitat or flucttiating meteorologicaI
conditions.
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are
. In this paper, we e.,<amme the premise thaiSioi:king stiiped baSs juvenileS is a superior, strategy
to stocking larvae. We Imve conducied larval rilark-re6ipture e.,<penments in three years (1991-1993)
and in two tribütanes, the Patuxent and Nanticoke Rivers (Fig. 3), to examine now vital rates of
larvae are related to mete6rological events and associated \vater qualitY (Secor et al. 1995a, b; 1996).
Our experiments indicated that larvae reJeased under favorable conditions made substantial
ccmributions to juvenile production. T~erefore, stocking larVae as a replenishment tool might be a .
..iable alternative to stockingjuveniles. Here. we first documer1t the contrlbution ofhaichery stocked
striped bass larvae to juvenile populations in the Pituxent and Nanticoke Rivers in 1991-1993. We
then apply estimated larval gro\'.lh and survivai rätes from past studies 'and the literature to compare ,
prcduction rates of striped bass larvae and juveniles in either wild or hatchery ~~vironments. Three
2
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ages at release were examiried: 7-d posthatch, firsi-feedirig "arvae; 55 day posthatch, "Phase f' .
juveniles; and 220 day posthatch, "Phase II" juveniles.. Criieria ccinsidered were rates ofbiomass'
accumulation, cost~ and genetic represemadon (riiiniber of spawnirig feriiales procl.1:ing an :i:mmil .
cohon).
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METHODS
Larval Mark-recapture Experiments
Striped bass eggs, obtairied from iriduced sp~Wnirig in the batchery ofl0 (1991). 8 (1992) arid
12 (1993) wild females captUred in the Patux.ent (1991) or Nariiicoke River (1992-1993). were
proVided to us by Maryland Department ofNatural Resources (Table I). Fenilized eggs were held
.iii-l-2 mJ raceways for mcuhritiori and larVal rmg 3.t the Mamiirig Hatchery. Larvae were munersed
~lutions cf aIi.Zaiiri. complexone (ALC) in 1991 and 1992 and tetrncyclirie hydrochloride (TC) in
1993 to produce fluorescent markS in their otoliths (Secor et al. 1991; Seeor et al.,1995).. Bätches
of embryos or larvae w~re. immersed arid marked at ages rangirig tram 0 to .9 days after hateh.
Bätches oflarvae were Inarked by single or multiple treatments (Table 1). Otolith marks (equivalent
i6 codes) on recapiured mdividtials provided information
releaSe, date, site, arid larVal
'at .
releaSe.
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on
age
Six to 13 day-old larvae were transported frorri the haichery to release sites aild reIeaSed
directlyirito the riveci. Release sites were chosen baSed üpon occurrences ofwiId striped öä5s l~ae ..
iri collections dtiring the week preeeding the initial stockirig date in eai:h' Year. Tests at the
Chesape3ke BiologiC3I Lab6riltorY eCHL) arid at ari on-site laboriitory on tbe Nariticoke River (19921993) showed no increased irionality dtiring a 24-h period associaied with the stoi:king procedtire
(water qUalltY changes) compared to coritrollevds (larVae maintained under hatchery water quality .
conditions). Therefore, in the field experiments. larvae were riot acclimated to river water prior to ..
their release.
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~btained
~~rveys
RecaptUres ofreIeased larvae were
in several one-day ichthyoplankton
from.
läte April to early June. f6Ilowing th6 first release ofmarked larVae. Sarnpling gears were a 60-cm
pla1lkton net and a2_m2 mouth-openirig Tucker trn\vl. Ori e~ch surVeyd~te, colleetions were made
ai8 to 11 stations spanning the knoWnnursery area ofwildSiriped baSs larvae...·Secor etat. (1995;
1996) provide details on methods arid analysis ofichthyoplankton sarnples and water qualiiY dataSets:
Juvenile striped basswere surveyed by Maryland Department ofNatural Resources in 37-m seine
coIlectionS from 13 July tö 15 September in an years. Thr~e surveys were cciriduch~d annüally at six
(Patuxent River) and eight sites (Naniicoke Rivef) thai have been sarnpled histoncaIly to index juvenile abundance (Minkkinen 1993).
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Otoliths of1:irVai and juvenile strlped bass were e."l:amined (Secor et aI. 199 i b). The pr.eserice
ofmarks on oiolith increments was determined under an epifluorescerice microscope. Ideniification
ofspecific otolith marks (Table 1) ailowed release date, larv:il age(s) :ii release, arid sites ofrelease
(1992 experiment only) to be deH:rrnined.
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Grov.1h and mortality rates of marked larvae were deterrriined based upon their
3
le~gths.
known ages and estimated abundances. Growth rates oflarvae were estimated from exponential
regressions oflength on age (Ricker 1975). GrciWth and monality rates from the exponential models. '
were compared statistically among grcitips using a Newman~Keuls test (Zar 1974).
During June, the Marylarid Department ofNaturaI Resources released 105,915; 97,297 and
278,844 coded wire-tilgged (CWT), young-of-the-year (40 - 60 mm SL) striped bass in 1991, 1992,
and 1993, respeetively (Minkkinen 1993). The number ofjuveniles stocked, adjusted for transport
mortality and tag lass, was 97,611; 71,124 and 209,133 in 1991, 1992 and 1993, respeetively. Based
lipon abundances of reeaptured CWT juveniles and seined juveniles originating from our marked.
larval releases, we were able to estimate reeruitment potential of our released larvae. Abundances
ofjuveniles from our marked larval releases (No.J were estiIDated (Ricker 1975; Secor and Houde
1995b) by:
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(1)
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where Ncwr = number ofreleased juveniles with coded Wire.cii adjusted for tag loss and stocking
mortality;
i (1 ...x) = experimental larval release group;
=number ofrecapturedjuvenile~
Ro,(
i
Rc',l,"T
thai had b~ releaSed as'l~aeand ~oded for
release i by the unique chemical mafk on the~ otoliths;
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= number ofcoded wire-tagged juveniles recapnired in t~e juvenile sampling
program.
Applying Equation 1, estimaies ofabundance ofjuveniles were obtained for each e.xperimenial .
larval release. The variarice of abundance estimates orthe oiolith-marked juveniles was calculated .
based upon an assumed Poisson distribution (Ricker 1975). In 1991 and 1992, all iarVal release:
groups were identifiable based upon the unique marks cind mark combinations on their otoliths. In
1993,.only one of the individual release group (second release, larvae 'releaied at 12 d posthatch)
could be confidently distinguished in th'e juvenile recaptures.. Specific identification of other marked
groups in 1993 would be depended upon very ac~rnte (± 3 days) ageing, which was not possible
based upon analysis of the juvenile otoliths in juveniles (Seeor änd De:m 1989). .
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Overall survival rate to the 40-60 mm stage for each release group (SJ was estimated by:
(2)
where Nc~,.L = estimated number .of 40-60 mmjuveniles from experimental releJse i (eq. 1) and;
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= number oflarvae stocked in experimental
i
with the stocking procedure.
reieas~ i adjusied for riioriaiity associated
Cohen Biomass Productien Model
, , The Cheiape3ke Bay strlped bass stocking program häSdepended upon rel~es cit either ca.
. 55 days after hatch (phase IjuvemIes) or ca. 220 days after hatch (phaSe II juveniles). We wished.
io co~pare these striltegieS' with rcle:ising laivae :it first feeding (7 daysafter hateh). Therefore, st:ige,specific growih and mortaIity rates arid wcights were obtain~d fOf the following periods: ' -2.5 to 6
days 3.fter h:itch (embryo). 7 to 55 daysafter hätch (Iarva), and 56 io 220 days mer hätch Guverule).
Hatching was assumed to occur at 2.5 days after spawning (Secor et ä1. 1992). ;Estimates ofvital
rates and wer weights ofwild larväe aiid juveniles were obtained fram fieid studieS Ui the PatUXent
. Rij;[ (Seco.r.an~ Houde i995a;,seeor etäI 199,5~,Minki#nen and ~ten~~.1993) ~d thc: Nantic?ke
~ (MinkinIlen 1993; Kellogg et al. 1996; Secor et äL 1996). Cohort-specific rates 6flarvaI-stage
gro~ arid ni6riality were <iVailable for aI1 years.. Estinlated i~tiaI egg weight (1.0 mg). wasobiained
from Secor et aI. (1992) for South Caroliriä striped bass because esiimates for Chesapeilke Bay
stnped bass were riot available.
, Estimates ofVit~.rates aild weights for hatchery-produced flsh were calculated fr6rii däta '
provided by the Potomac Electric Power Company which pr6duced ~e Phase I and Phase II juveniles '
stocked into the Paruxeni and Nanticoke River (PEPCO 1987-1995). P6rid-speeiiic rates 6fIaiv<il
gr,oV/tb, m6roility. and weight wereävailabie for sever:il p6~ds iri the period'198i-1995. Omy
vaIues ofjuverule SUMvä! arid groWth were reported in PEPCO ßoeuments. Wet weights at 7 d
posthatch ofhätchery-producect larvae Sto6ked into the Nanticoke River were rrie:isured by Kellogg
(1996).
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mean
Coholt, Stage-specific biomass cEs) was estimated as:
, ["11/W
) [l-{ZstGs»]
B'S -- B' Se,
\ n S
S-l
(3)
where Es<, biomass at tbe end ofthe previous stage, Wsand WSet are median weights at the end of
miges Sarid 5-1, arid Gi arid is äre d:iily iristantarieous gröWili-iri-weight and moriaIity rates for
stage S. Ibis method
adapred from Houde's (1996) model ofbiOlnass proliferation lind allowed
cohort bi6mass to be "firie-tuned" to expected stage-specificweights. To reduce the effects of
.;)utliers, median v:ilues' were chosen to represent stage-specific vital rates arid weights. In cases
, ·.",here 3 or fewer data were available, me:m vital rates arid weight values were used to estimate '
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wlOmass.
was
In our corriparison arialysis, we adopted a model scenario which depended upori stockinga
maximum bioniass ofjtiveniIes (phase I Phase II) in a year ofpoor natural reprodticrion.. Bo• the
::-jtial spa\vned biomass, was, specified as 2 106 gfor ri:ihiraJ cohorts (egg prodUction =2 biIlion, ca.' '
1.000 spawning ferriales). Field estimates ofspawnedeggbiemass in the Patuxent and }Iaiuicoke
?Jvers ranged ben.veeri 0.7 and 6. i million grams (Secor and Holide 1995~ Kdlogg et al. 1996). Tlie"
wade!ed scenario represenH::d a year oflow egg production. Initial egg biorriass in the haichery was
sr:~ula[ed at I o~ g (egg production = 10 rriillion, ca. 5 spawning females). Ten million eggs .or ca.
ci
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analyzed (1991 and 1992), the average cohort lost biorriass during the larval stage (Fig. 5). However~
several "weekIy"cohorts (larvae spawnedWithiri the same 4-6 day penod) during these years showed
increases in cohort biomass (Secor and Houde 19 q 5a; KeIIogg et al. 1996~ Houde 1996). For
example, in the P:inixent lUver (1991) Secor and Holide (1995a) .Showed that high survival rates
oc:ciured wheIi weekly cohorts e.'{perienced me:in tempemtilres of 16-20~C dtiring their firSt 25 days
after hateh. In that year, larvae were stocked duririg a period followed by favorable temperätures.
Alternatively, complete loss of release grotips in our experime~ts provides critical insight on when
and where not to stock larval stnped basS. ;rn 1993 (Nanticoke River), a stonn event appareritly
ciwsed in complete loss oflarvae stocked on 24 April; no larvae 01' juveniles were rec()Ven~d with a
Inark correspondirig to this grctip (Secor et al. 1996). SirDilarly, in 1991~ complete loss ofan eritire
group ofstocked larvae occurred becaUse the releaSe was.doWnStream from the maximiun turbidity .
zone which may serve as a retention front, de1imiting the· doWiistre~ boundary of striped bass
riurseries (Secor et aI. 1995; Secor 1996)..· R~tS from three yeax-s ofi~hthyoplCÜlktori surveys and
larval mark-reC3Pttlre e.~perinierits. indicated thai suIvivai cf rel~ased 1~3:e ciften is substaritially
higher than that of average weekly cohorts of wild larVae if larvae
strategiCally released inta
favorableconditionS. These conditions include: 1) penoelS' ofstable aiid rising temperatures between
16 arid 20°C; 2) mea.n nursery alkalinity >15 Irig,tL as CaC03; pH>6.9; arid 3) avoidance of stonns,
es'pecially during dry years (Secor 1996).
are
Meterological fol-ecasting aild surveys ofmirSery water qualiti co~ld. increaSe the.probability
of stocking hiiVae into favorable conditions. However, weather dtiririg April and May is quite
variable arid not easily predieted, arid hätchery-pioduced la.rvae ofappropriate ages may riot always
be available to Stock during favorable coriditionS. oespite
un~ertainties,we beIieve that a lang':
tenn larval stocking prograni could, on average, ii.tgirient mitural Striped bass juvenile abundances
in poor to average years of natural recruitrrient.
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Stocking Strategy: Larvae or Juveniles?
How efficient is larval stockirig in eamp3rison to stockirig hatChery-produced juveniles? We
addressed this question by assembling available data, estirriating stage-specific vital rates arid weights,
and anaIyzing raies ofbiomass accumulation arid hatchery contribtitions under scenarios of releasimz
larvae, Phase Ijuveniles or Phase IIjuverules. LarVa1 mcirtalitY rate estimates were the most variabi;
(wild larvae) or uncertain (hatchery larvae). Therefore, these rates were deIiberately varied· to
evaluate larval versus juvenile stocking strategies.
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WebeIieve that biomass eStimates ofWild Strlped hass at 55 ci posthatch (Fig.5) forthe 19911993 annual cohorts may have beeri uriderestimated. EstiIri:ites (Secor:irid Houde 1995; Kellogg et
al.·1996) ofcohort abundances at 55 d posthatch were 14,930,5,435 arid 28.387 for 1991, 1992, and
1993, respectively. These estimates were one to nearly three orders ofmagnitude less than rrud.iuly
abundance estimates for juveniles at ca. 85 d posthatc.'l (Table 3).. Striped bass are difficult to sampIe
and monaIity rates are difficult to meisure during the laie larval and earIy juvenile period because of
an ontogenedc habitat shift from freshwater pelagic to brackish benthic habitats. Ifmonality rates
were lower during this period than we had estimated. substantially higher biomass gain compared to
those predicted may have been realized. Finer scale resolution 'of ontogenetic changes in mortality
and gro\l.~h rates during the larval stage :vould probably result in higher bioinass estimates at 55 d
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posihät~h b~cause the differerice, G-Z, .wollld be expeeterl to increase wiih size (see Equaiion 3).
Because ofthe unc.ertainties iri estimati~g rriortillit}r rates during the larval stage; a prudent approach
was one that considered several possible inoriaIitY rates in the field (Fig. 6).
The overiiIi scenario for comparlng .~iid and Stocked bioniass ac.cUmlllatioii rates stipulated
alow spaWningyear (egg produc:rlon =2 billion ~) and hatchery prciduetion limited to five females ..
or ca. 2.7 million 7-d pa~thatch Iai-väe. AIthough inany more larvae wen~ acil1aIly stocked iota the
PatiiXent and Naiiticoke Rivefs, this number representiä maximllm number oflarVae which cOllld be .
. initially reared to grow Phase I er phaSe n jUveniles at the. PE?CO .hatchery.IncreäSerl egg
produetiori in the nversor hatchery produeticin cflarvae wouldalter the results cf the stijmlated ..
model. For instance, Stockirig 13
laryae rciiher thim~.7inillion would result in a4.8 fold
increasein biomass ofhatchery larvae andjuveniles andwouId reswtin a 2.4-fold,increase in hatchery
contribution by Stocked larvae to ovefall (stocked +wild) larvci1abundance. AIternaiively, a large
produetion of 7 billion rather th~ 2 billion in the river woiild r~ult in a. 3.5-fold iricrease in
blamass ofwild larvae arid juveniles, and result Ui a1.3%coritribtidon of2. i million stocked larvae.
Changing sceruirios ofinitial prcidtiCrlan
6fwild arid hat'chery laivae wiil meet only
relative
cantribution ofhatchery stocked fish. The rates arid oritogenetic pattern of biomass accümulation
within hatchery arid wild cohorts will not be affecied.
.
million
4tJ
rates
the
Patterns cf biomass acciiiriuIarlon' iricriciitecl that Wider a scenario of low r1<itUriU egg
produ6icin, haichciy releaSes of larvae arid juvenl1es could. rriake >10% contributions to overall
aburidances (Fig. 7). Iflarvae werestock@ illto favorable. conditions (intermediate er lo\V mortaIitjr
rates), then poSitive rates ofbiomass increasewere cqlected (Fig. 6). ,However, under all scenarios,
highest biorriäss ac~rriulation was prediCted for hatchery-pradticed striped bass dtiring the larval .
.Stage .Therefore, from' the perspective of riimmizing Striped bass praduci:ion rates, hatchery
contribtition wöuld be highest ifjuvenile (ph~e I or Phase IT) striped bass were stocked.
Wheri costs were faetored into hatchery contributian rates, stocking Phase I juveniles was
predici:ed to mosteost effeciive siratCgy,if 1) HatcherylarvaI mcirtality ra.te
law (Z = 0.025
arid 2) Wild larval surviväI was poor or. iritennediate (2 ~ 0.12, 0.20 d'I). However, ifhatchery
larval iricirtality rate was high (Z = 0.05 d'I), then Stocking larvae was most cast efficierit ünder all
ScenaHos ofwild laival SllrVivaI... Iri YeaI-s ofhigh earIy survival rates cif~ild laryae, the cast perunit
hatchery cori~buiion waS.2.5 - 3.3 times lower for reIeased l<irVae than for released Phase I or Ph~e '.'
II jtiveniles.' Re:lrlng larvae and juveniles under sUch situations is wasteful becallse hatchery-pend
e.1\;roninents do not increase rates ofbiomass acCumuIation cver that which would occur in ihe wild.
Bec:llisepredictions ofcost-effeetiveness ofstockirig larvae or Phase I fish was sensitive to estimates
.
orhatcherylarval rrioriality rate, ruture efforts should be aimed at refining this estimite.
.a
be
was
was
Evaluation ofgenetic co~ts of stocking larvae or juveniles, indicated that either strategy
equiv~ent; dfective population size was inversei y relaied to hatchery camribution rate. Secor et al.
(1992) reponed that single-brood i-earing ind praetices at South Carolina hatchery resulted in a
sirigle female parerii contribllting 90% ofPhase-I juveniles stockecl into the Santee-Cooper Reservoir·
j::c~ulation in 1990. Stocked larvae routineIy cari be the pooled broods ofnumero~s parents: arid can
i~;:;"e:lSe genetic representation ofstocked fish by lowering ihe probability that duririg pond-rearing
ir::ii\idual broods will be eliminaied either intehtiorially (i.e. culled) 01" through disease 01" other pond-
a
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rearing mishaps (Kerby and Harrell 1990). Larval stocking alsowiIi limit the capäcity ofh,ücnery
production relative to natural prodticticin so that ha.tc~ery contribtitions will not exceed 90%. At
levels greaier than 90% contribution, NE dropped to levels below those recommended for fishery ,
recovery progI-ams (NE ~424; Tave 1986).
Larval stockmg :is a strategy to enhance juvemle producrlon ~d recruitment of striped bass'
has other import~t ädväIiiages over juvenile stocking. ,'Ne believe that stocked larvae '.viII adopt·
behaviors that 1e3.d to successful feeding, growth, aIid survival in the na.tural enVironments inte which
thev are released. Releäsed lcuVae had similar groWth ,a.nd mortality rates and disperSal patterns
co~pared to contemporary wild cohorts (Secor ei 1~95; 1996). 'Larvae reared in ponds arid
siocked asjuvenileS, niay deve10p behaViors thatare favor.wl~ in theCartificial' pond environment but
not in juvenile riurseries. For 'e.Xaniple, AridreaSen (1995) found ihat hatchery.;.origin Phase II '
juveniles suffered high predation mortalitY (Z = 0.16 to 0~36 d"l) dunrig the 001: four days after
stocking in the Patuxent River, appanilitly oecause ther behaVior promoted canmbalism by older Wild
striped bass. By the juvenile stageit is probable that fish stocked as larvae and surviving tothe '
juvenile stage will have been "selected" to behave ,more appropriately in the natural environment, arid '
their SUMval potential will increase. '
"'
at
-
•
..
~
..•
Aoplication of A.pproach to Other Species
Camparisans ofontogenetic, patterris cf coholt biomaSs betWeen hatchery and na.tucil'
environments could provide perspeciive on the efficieney ofStock eiiliancement strategies in'ether
anadromous and coastal fishes. Salvaries et al. (1994) used a si~ar approach which considered the
ratio ZlG aS ari iride.'{ of coholt biomass production toevaluate stocking different age (size) cöd'
juve.'liles into fjordsfrom pond production. These approaches require accilrate estimates ofvitäl rates
in naturä! and artificial environments. Otolitll-based aging 6flarvae and juveniles arid larval-mark
recaptufe experimentS can provide estimates ofvital rates in the field (Tsukarnoto 1989; Secor et äl.
1995c). However, hatchery based estimates of embryo arid larval stäge-specific abundances mäy
require beiter methods than are eurrently erriploYed.
We be1ieve that ccimparing stage-specific rates ofbiomass accumulation may be particuiarly
relevant to Arrierica.n shäd (Alosa sapidissima),which are sirciIartostriped bass. Shad spa\vn pelagic
eggs in tributanes of estwmes aiide.'(hibi~ high early rrioi-tality rates that are largely coritrolled by
e:wironmental factars (Creccoand Savoy 1984). Federal and state hatcheries have been releasintr
millians of Americän shad larvae hita the Susqueh~a River, Chesapeake Bay's largest tributary~
since 1976 (St. Pierre 1994) arid other state an4federaI, agencies are rapidly developing :ind
expanding lal\:aI stocking progniffis elsewhere in the Chesapeake Bay region (Gaririari 1995). Despite
these enhancement programs, little is kI10Wn oflarval and juvenile production rates in the wild (Kahri
and Weinrich 1994), and the efficiency ofhatchery production relative to natural production reinairis '
unevaluated.;
,
LITERATURE CITED
AS~lFC. 1995. StIiped Bass ~esearch Stücly, Report'for 1993. mlF,S, Woods Hole, ~IA.' 3 I pp.
12
•
..
Andreasen, L. L. 1995. Predation on hatchery-reared striped bass, Morone saxatilis,in the Patuxent
River, Maryland. M.S. thesis, University ofMaryland, College Park. 88 pp.
Boreman, 1. and R. R. Lewis. 1987. Atlaniic coastal migrations of striped baSs. Am. Fish. Soc..
Symp. 1:331-339.
Gaiman, G. C.
.
.
1995. Back to the Future? A tale ofshad in Virginia. Virginia WiIdIife. January:2.
Gibsan. M. R. 1993. Historical estimates offishing moruility on the Chesapeake Bay striped bass
stock using separable virtual population analysisapplied to market eatch data. Striped Bass Tecluiical
Committee,. Rhode IsIarid Div. Fish and WiIdIife. 15 pp.
'
Hall, L. \V., S. E. Finger and M. C. Zeigerifuss. 1993. A review ofin situ and on-site striped bass
c:'aminant and wat.er-quality sttidies in Maryland waters ofthe Chesapeake Bay watershed. Am.
Fl~SOC. Symp. 14.3-15.
Houde, E. D. 1996. Evaluating stage-specific survival during the early life offish. pp. 51-66, In:
Watanabe, Y. and Y. Oozeki (eds.). Survival strategies in earIy life stages of marine resöurces.
Balkema, Rotterdam.
Kahn, D. M. and D. R. Weinrich. 1994. Effects ofstocking and natural reproduction on recovery
ofAme:ican shad in the upper Chesapeake Bay. In: J. E. Cooper, R. T. Eades, R. 1. Klauda and J..
G. Loesch (Eds.). Anadromous Alosa Syinposium. Tidewater Chapter, Alnerican Fisheries Socieiy,
Bethesda. MD. pp. 86-96.
Kdlogg. L. L. 1996. Striped bass (At[orOlll? saxatilis) egg prodtiction and environmental factors .
intluencing larval population dynamics in the Nanticoke River~ 1992-1993. M.S. thesis, University
of:\faryland. College Park. 270 pp.
13
Kellogg, L. L., E. D. Houde, D. H. Secor and 1. W. Gooch. 1996. Chapter 1. Egg production and
environmental factors influe:lcing larval population dynamics in the Nanticoke River, 1992 - 1993.
In: Episodic water quality events and striped bass recmitment: Larval mark-recaprure experiments
in the Nanticoke River. Final Report to Maryland Dept. ofNatural Resomees, Cantraet No.
CB93-006-002.
Kerby, 1. H. and R. M. Harreil. 1990. Hybridization, genetic manipulation, and gene pool
conservation ofstriped bass. pp.l59-190. In: R. M. HarrelI, 1. H. Kerby arid R.V. Minton (Eds.)
Culture and Propagation ~f Striped Bass arid its Hybrids.. Anlencan Fisheries Sec: Bethesda, MD.
,
,
' . ,
.,
Minkkinen, S. P. 1993. The use of hatchery produced Striped bass for stock restoration and
validation of stock parameters. In: USFWS and NMFS (EdS.). Striped Bass Srudy Workshop.,
Aimapolis. p.25.
.
PEPCO (potomacEectric Power Company) 1987-1995. 1987...1995 Aquactilture Project Report.
AvaiIable from :Me. Paul M. Willenborg, Waters and. Land Programs Dept., PEPCO, 1900
Pennsylvania Ave. N.W. Washington. D.C.
•
Ricker, W. E. 1975. Computation and interpret~tion ofbiological statistics offish populations.
Canada Fisheries and Oceans, Ottawa, Ontario. 382 pp.
Rutherford, E. S. and E. D. Houde. 1995. The influence oftemperature on cohori-specific growth,
survivaI, and recruitment of stnped bass, .\1orone saxatilis, larvae in Chesapeake Bay.. Fish. BuH.
93:315-332.
Salvanes, A. G. V., 1. Giske and 1. T. Nordeide. 1994. Life-lllStory approach to habitat shifts for
coastaI cod, Gadus morhua L. Aquacult. Fish. Manage. 25:215-228. . .
Secor, D. H. and J. M. De~. 1989. Somatic. growth effects on the otolith-fish size reiationship iri
youngporid-reared striped baSs, l\1orOliesaratilis (V{albaum). Can. 1. Fish. Aquat. Sei. 46:113-121.
Secor, D. H., M. G. White and 1. M. Dean. 1991a. Immersion rnarking of l~'al and juvenile
.
hatchery-produced stripe~ bass with oX)1etracycIine. Trans. Am. Fish. Soc. 120:261-266.
Secor, D. H., 1. M. Dean and E. H. Laban. 1991b. Manual for Otolith Removal and Preparation for
Microstructural Examination. Baruch Institute Publication No. 89-03. Eleetric Power Research
Institute and University of South Carolina. 85 pp.
Secor, D. H., 1. ~f. Dean. T. A. Curtis and F. W. Sessions. 1992. Effect of female size and
propagation methods on larval production at a South Carolina striped bass (J...forone saxatilis)
hatchery. Can. 1. Fish. Aqu:u. Sei. 49: 1ii8-1787.
Seeor. D. H. and E. D. Hcude. 1995a. Temperature effects on the timing of striped bass egg
produetion. larval viability. arid recruitment potential in the Patuxent River (Chesapeake bay).
Estuaries 18:5:'7-:4-+.
14
•••
Secor, D. H. and E. b. Holide. 1995b. Larval mark-release experiments: Potential rar research on
dyriamics arid recruitment in fish stocks.. pp. 423-445, In: Secar, D. H., S. E. Carnpana ancl 1. M.
Dean (eds.). Recent Developments in Fish Otolith Research. Belle W. Baruch Library iri Marine
Sciences Number 19. University ofSouth Carolina Press, C~umbia, S.C. 751 pp.
Secor, D. H., S. E. Campan:i and J. M. Dean. 1995c.. Recerit developments in fish otolith research.
Belle W. Banich Library in Marine Sciences Number 19. University of South Carolina Press,
Columbia, S.C. 751 pp.
.
Secor, D. H., E. D. Houde and D. M. Monteleone. 1995. A mark-release experiment on larVal
striped bass Morone saxatilis in a Chesapeake Bay tribut:iry. ICES J. Maz.. Sei. 52:87-101.
•
Seeor, D. H., E. D. Houde and L. L. Kellogg. 1996. Chapter 3. Vital rates, dispersal, and
recnntment potential ofhatchery-released Striped bass larvae in·the Nanticoke River, 1992 and 1993.
In: Episodic water quality events and striped bass reeiuitment: Larval mark-reeapture e.xperiments
in the Nanticoke River. Firial Report to NIarjlaiid Dept. ofNaturaI Resomees, Contract No.
CB93-006-002.
St. Pierre, R 1994. American shad restoration in the Susquehanna River. pp. 81-85, In:Cooper,
J. E., R T. Eades, R 1. Klauda arid 1. G. Loesch (eds.). Anadromous Alosa Syrriposium. Tidewater
Chapter, American Fisheries Soceity, Bethesda, MD.
Tave, D. 1986. Generics ror Fish Hatchery Managers. AVI Publ. Co. Inc. Westport, CT. 299 pp.
TsUkarI16to, K, H. Kuwada, 1. Hirokawa, M. Oya, S. Sekiya, H. Fujimotoand K. Imaisuriü. 1989.
Size-dependent mortality ofred sea bre~, Pagms major, juveniles released with fluorescent otolith
tags in News Bay, Japan. 1. Fish Bio!. 35:59-69.
•
UlanoWicz, R E. and T. T. Polgar. 1980. Influences of anadromous spawning behavior and optimal
environmental conditions upon striped bass (Morone saxatilis) year-class success. Can. J. Fish.
Aqmit. Sei. 37: i 43-154.
Uphoff, J. H. 1989. Environmental effects on survival of eggs, larvae, and juveniles of striped bass
in the Choptank River, Maryland. Trans. Am. Fish. Soc. 118:251-263.
Wirgin, I.~ L. Maceda, 1. R. Waldman and R. N. Crittenden. 1993. Use cifmitochondrial DNA
polymorphisms to estimate the relative coritributions of the. Hudson River and Chesapeake Bay
striped bass to the mixed fishery on the Atlaniic Caast. Trans. Am. Fish. Soc. 122:669-684.
Zar, 1. H. 1974. Biostatistical Analysis. Prentice-Hall, Inc. Englewood Cliffs, NJ. 620 pp.
Zastrow, C. E., E. D. Houde and E. H.Saunders. 1989.. Quality ofstriped bass (""torone saxati/is)
eggs in relation to river source and female \veight. Rapp. P.-v. Reun. Cons. irit. Explor. Mer.
191 :34-·n.
15
--.
Tuble 1. Striped bass larnl m:u-k-rec:lpturc c:xpcrimeniS, P:ltu.xcnt River (l99l) aridNill1ticoke Rivcr (1992-1993.
R:lc:lsc reccrds for stripcd bass laivrie by yc:u-. Brcxids ure design:ltcd :lCCOrding to Mmyl:1Ild Depurtmcnt of}latur:ll
ResoUrccs Hutehery records. Rcle~e site indic:ltes batchcs of larvae which were rele:lScd at da\',nrivcr and upriver sites .
withiri the su-iped b:1SS riursery. ~'Ages rnarked" indic~te th6 :lges at ~hich larvae WCfe immersed iri 25 ppm alizarin
cornplexone er 400 ppm tetracycline h)'drochloride for 6 hr to mark their otoliths. Nwnbers relcascd ,vere estiniatcd
volwnetrically (Le. nwnber ffi'J) in remng troughs 6 hr before release.
....
,.
'
..
"
.
.'
"'W'
","",'. -'• ."
~_"
'. _'
..
.'
...
..
," "".'C.,,......
..
.
".
.,
Rele:lSe Site
Larval
ReIC:lSe
Date
BroOd(s)
..
.(d)
1991 - Patu.xent River
..
..
P-8
.
...
'
.
26 April
...
Ageat
Rele:l:ie
Do\mriver
.
"
.,
..
Ages
Marked
(d)
.'
....
.""-
..
.,.,,~".
9
MiUions
ReIe:ised
0
..
0.72
,
P~9,
10, 11, 12, 13
Upriver, Downriver ..
26 Apnl . .
.
9
,
'
P-I2,13
P-14, 16,17, 18
Tot:u Rele:lSed
.30 April ...
,lJpriver, Dov.nnver
30 April
Uprivcr, Dci"nnvcir
....
N'.13
~·13
...
..
N.I5, 17,20 .....
N.I4, 16
I
..
. ......
'
24 April
Dov,nr1ver
24. April
Upriver
25 April . .
25 April ..
.'
6
9
,.
..
'.
3.24
.
~-
_,."f
1.44
.
1.14
2
..
.I_..
'
Upriver
..
8
.'
,
. ...
...
..
7
8
'"
N·14, 16
.
...
28 April
N.18,21
1 May
N·19,22
1 May
Tobi Rele:lSed
'
.
..
•
..'
.
0.65
.
5
...
1.13
5
1,3 .
5
1
0.93
1; 3, 6
).72
1,6
2.72
..
1.55
.
-,
. 28April
N.15, 17,20
..
6.54
.
....
. Do,..nriver
.,
'.
.
1992 -:-Nrinticoke Rh'er"
..
,
13
...
."
"
....
8
.'
.
Do\\nrlver
8
. Upriver" ,,,. , . .
8
....
....
.'
•
,
,
.
Do,;'nrlver
10
0,7
Upii'rer ..
10
0,9
.,
.
-,
~,
2.40
..
,
2.12
13.22
...
1993 - Nrinticoke River
N·I, N-3. N-4
21 April
Upriver, Downnver
10
8
2.18
N-5. N-i
25 April
Upriver. Downri"er
12
8
1.07
5
2,48
3.98
'.
N.ll. N-13
~.16, N·1 i.
~-19,
N·18
N-ZO
25 April
Upriver, Downrh"er ..'
9
29 April
Upri\'er, Dowmh'cr
6
J
Upri,·cr. Downn\'er
6
4
3 M:1y
.
.
.
T01:11 Rclc::scd
i ..
,
2.18
11.39
1991 - 1993
: Cl:ll Rclc::sd
31.65
16
.
T:1bce 2. Stripcd b:lSS Im':11 m.u-k-rcc:lpturc e:xpcrimcnts, P:1tuxcnt Rivcr (1991) :uid Nanticoke Rivcr (199i1993, Gro\..th and mort:lIity coefficients :unong hatchery-produccd fe1C:lSC gToups. g";' length-specific grO\..th
coefficicnt; .G = wcight-specific grO\..th coefficient .G coCllicient W:lS b:lScd upon com-ened lengths using :l
weight-Icngth relationship (Houde <Ütd Lubbers 1986). ReIciise site indiC:ltes batcheS of 1:ln':lC which \\"ere
reIe:lSed :lt downriver .md upnver sites withiri the striped b:lSS nursery.
.
.
~
ReIe~e
ReIe:lSc RK
. Age:1t
Rcle:lSc
UD. Do\vn
9
0.037 ± 0.003
0.157.
0.154 == 0.049 "
UD. DO\m
9
0.032 ± 0.001
0.139
0.085 ± 0.039
30 Aorii
UD. Dov.n
13
, 0.036 ± 0.008
0.153
0.188 ± 0.084 .
6.30 Anril
UD. Down.
9-13
0.032 ± 0.001
0.139
D:1te
26 Aoril
.26 Acril
.0'
Z:!: S.E.
",
1992 - N:lnticoke River .
,
.
I . .. Uo
I
.
'I.. ." Uo . .
" 24 Aoril .
o.
24 Aoril
'. .." 25 Aoril.
'. 8
.
I.
I
.0
DO\\n .,
•••. ·
.' 0.007:!: 0.0033
,0.028 ± 0.0028
8..
Uo
28 ADril
..
......
".
,
.
"
"
... 0.028 .....
.
'0'
. 25 ADril .
.
,
,
....
0.159 ± 0.038 . .
.
0.121 .. ,.0.091:: 0.024
5
0.031:!:0.0023
0.133
5
..
8
.' .... 0.025 ± 0.0024
. 0.106
.. 0.075 ± 0.022 .' .
'. 0.061
0.145:0.118
0.028 : 0.0030
... 0.118
0.149: 0.021
0.025 : 0.0038
0.106
0.135: 0.051
0.014:!: 0.0017....
.0
_0.103::0.032
.'
Dci\,n
8
Uo
, 10
0'·
f'
.
1 M:1v .
1
1Mav.
10 ....,
Uo. Do\vn
8
0.026 ± 0.0028
.. 25 Acril
.. 1 ... Uo. Do\vn
5
.: 0.027 ± 0.0020
Uo. DO\vn
8
Uo. Down
1 M:lV
24 Aor - IM:1~'
I
I
I
ud. Down
..
"
0.161: 0.399
_.24 Aoril
28 Aoril
.A,
0.109
. ,'. 0.111 :: 0.025"
0.114 ...
0.082 ± 0.027
0.026:!: 0.0030
0.113
0.162 == 0.025
10
0.024 ± 0.0036
0.105
0.148 ± 0.055
5 - 10
0.026 ± 0.0013
0.111
..
, ,
.,
..
21 Acril
25 April
25 Aoril
29 Aoril
3 ~IJ\'
..
: (ADr -
3 \1:1\'
I
I
I
I
I
I
UD. Down
'
:
i 993 - Nanticoke Rivcr
-
_.
-
0.035 ± 0.0029
0.153
0.066 = 0.017
± 0.0023
O.I~7
O.IOR :: 0.021
10
..
UD. Do\\n"
9
Uö.Down
12
UD. DO\\11'
6
0.030 ± O.OO~~
0.128
0.047:: 0.032
UD. DO\vn
()
0,030 ± 0.00 I
0.130
0.039 = 0.009
L'o.Do\\TI
6 - 12
0032 == 0.0015
0.13(,
-..
0.03~
1;
.
-
-
Table 3. Striped bass l:rrval m:lfk-recapture experiments, Patu:'Cent Rh'er (1991) and Nanticoke River (19921993. Petersen population cStimates for juveniles on 14 July.1992 and 13 July 1993. Total ,'tild popu1&ltio n
cstim&lte from Minkkinen (1993) and Minkkincil (pers. comm.) does not include ruuchery-stockcd juveniles \'ti th
coded wire tügs. N = numbcr of recriptured juveniles that originütcd from rele:lSe ofhatchery-produccd l'lr\"&le.
...
'-,
..
,.
Release Date
.,
Releüse Site
.
.
"-
Up-,Downnver
5
1 Müy
_Up-,Do\'inriver
2
22,184
.'
.
. Tot:ll Wild
9,425: 48,469
-
Rel~ed%
..
23.5%
Contrlbution
-
C
.
"-"'"
..
... '
1992 - Nanticoke
,"
0
Upriver
24 April
Do\mriver
25 April
Upri\'er
25 April
DO\Vnnver
..
--
28 April
Upriver
28 April
DO\'tnriver
1 May
Upriver
I May
DO\mrivcr
All Releases
Up-,DO\'tnriver
.
,
"
c
2,682: 55,428-
8
30,050
. " 9,068 ~85,824
3
11,269
1,660 -47,765
14
52,588
5.,
18,781 .,
4
0
,
Releases
I Up-,Do\\nriver
Total Wild
Rclcascd o~
Contribution
3.23
,
0.65
..
1.93
4,342 - 63,60 I·
0.78
-
0.0
. 88,273 - 178,424
0.97
_.
"
127,714
, 0.97'
,
--
0'
.
Up-,DO\\nrivcr
All
..
0.0
,',"'"
28.8%
25 April
(12 -cl l:lT\' ae)
!
.'
0.0
20,689 - 127,714 .
,c..
315,528
,
,
- ._ .. ,--'
,',
.~
.
1993 - Nanticoke
\
,
15,025
~
,
'C'
4
Rcleased %
Contribution
I
,
0
Total Wild
"
-...
'.
0
0 .. '- -34
048
. '
--
','
.
-".,,-- .......
0
..
'
..
".
0
24 April,
0.78
"
,
,
.110,922
,
"
'.
._'
..0.68
38 7;,.18,849
- -
.".~
31,058
. Up-,Downriver . '._ 7
,"
,
5,385 -39,381
8,874
'
(%)
-
- ,
.
Survival
--
1991 - pätu.xent
,"
. 26 April
." All Releases
95% ConfidCnce Intervals
Petersen
Esiim:ite
N
(RK)
.
,
"
.
'
.
.
.
2
120,809
12.081 - 434.913
11.29
8
483.237
205.3;6 - 95-!.392
4.06
c
I
I 9.132.141
I
-
~Ol
,) • .)/1)
-
18
•
"
,.,
"
=
SoW"Ce
me:m s.e
P:l."(-91
...
N:m-92
.' . . . ,. 0.706
medirin
n
me:m±s.e
.-
1
0.226 ± 0.079
0.348 ....
median
me:m:l:s.e
n
, 0.149
0.191 ± 0.037
....
8
: '.' ...O~012
7
..,.
medi:m
...
..1
:0.005
-
..
1
..
0.125 ±0.018, .~; 0.13E::'~: 8 " ~·~.o:oii
1
~~----. .-.---....-4-.-.----+-..-_-l--0-.0-2-5-±--0-.0-0-3-+-.-0-.-0-17-;.....r...-6-1-+-..-...-._..-0.-0';;"02-'= -?-+-..-.. -.. . ?-.- ....--.1--8Nan-93
..
0.690
1.1
-
SC
0.155:: 0.026
Wild
0.581:: 0.117
I
I
3
0.039::!: 0.009
0.020
0.183±0.031
0.141
12
0.155:: 0.026
23
0.013 ± 0.005
0.025 ::!: 0.003
'..
0.017'
73
0.002
..
..
,
,
0.126::!: 0.005
.
...~
Oji6'·::,:
......
,'",.,
G] (d>l) ,.
:,
PEPCO
I". ,
0.159 ± 0.009
=0.003
0.151 =0.006
0.190
.
.1
.
....
..
0.190::!: 0.003
.,.
Wt, (mg) . ,. .'.
.....
"
7
,
8
Nan-93
8
_'0"
N<in-92
Wild, . .
...
0.159
'..
9
0.188 '.. 162
0
.. , . . . ' "
0.023 ._,
0.025
=0.0001
0.146
24
.0.021
=0.0001
0.188
62
0.025
=0.0001
6
184.58 ± 68.91
102.71
N:m-92
0.725 :: 0.027
0.705
8
787.81 ±
280.18
·350.80
275.26
9
10205.5
.
675.57 ±
249.92
PEPCO
370.67 54.25
332.09
24
24783.30::!:
1917,45
275.26
23
10205.5
332.09
24
2~783.30
'
0.630 = 0.053 ... 1 0.651
9
=
,
0.650 = 0.030
. • 0·
1
•
1
0.025
2~
, 3
0.025
~
0.611
Wild
1
Wtz{mg)
0.582 .= 0.069
O.58§= 0.169
,
: "'':-0.021
P:l.X-91
CBL
.,e
...
".
P:l."(-91
"'<
.
,.
.
Hatch
-
'.
I
...
7~"._
10250..5
7
10205.5
-
..
..
.....
..
23785.90
--., ,
23785.90
--, .
2
0.673
23
560.30 ±
136.76
H:ltch
I
0,586
=0.169
I
.,
370.67:: 54.25
.. .
19
1917,45
::
Table 5. Striped bass stocking biomass model. Estimatcs of changes of variance in family size
(VJ and effective :tumber of spa\'.ners ~) associatcd with vanance in survivallo 7 or 55 days
after hatch undcr the scenario of egg productions of 5 or 10,000 female spawners in the hatchery
and wild, respectively.
Source
Age
VK.
NE
Hatchery
0
0
5.0
7
4.00
3.3
55
6.22
2.8
0
0
10000
7
5.93
5044
55
6.05
4969
Wild
•
20
NIIIlIIcaca A1ver SlIIped Baas
Chesapeal<a Bay, MD
r
25·
In fi
20
I
!!
C
!
ia:
10 .
•
.
I
1\I I
!
:"
'!I
i
!
;\ I
!\ \rL I
~ v\'~ F i 1(vV~
• ,
'I
: I
.
!
•
11
I :
:
: :
\ A! '/
I
1993
i
5
0
1\'
t I·
i
I:
15
t,
f
L
1955
- ' -__.._ _._ ...JI
-I.
1965
1985
1975
-1992
_
1995
"$81'
Figure 1. Striped bass recruitment time series for the Nanticoke River (Chesapeake Bay), 1956-1994.
Recruitment is indexed by young-of-the-year abundance measured as the mean number ofjuveniles collected in
seine surveys ofthe Nanticoke River (Cosden and Barbour 1995).
CJ
rn
•
~
'2
~
~
800
"0
600
Phase I
Um!!,";!!'·1 Phase 11
-:l
<I)
I::;
~
:1."
u
o
Ci)
-
:::::"
1-
rn
"0
rn
~
o
~
I-
:::::
400 r-
o
c:
ca
I;::;
200
~
o ...
:::::"
;t';:
Li
1985
!
~'
~.
~t:
t"ill;'
lliie
~Ji
"':~;
1:':;'
1-:'"
1987
:::;
:H:
1989
1991
II
1993
Year
Figurc 2. Numbers ofPhase I (35 - 50 nun TL) :md Phase II (150 - 200 nun TL) striped bass juveniles stocked
into Maryland. Chcsapeake Bay tributaries :lS P:lrt of the stripcd b:lsS rcstof:ltion progr:lm, 1985-1995.
21
Washington, D. C.
-
•
/
(
/
./ ,~, / Mantfcoke
~ ...... tRiver
"-
."
•
--
Figure 3. Map of Chcsapcakc Bay showing Patuxcnt and Nanticokc Ri\'crs.
22
Patuxent River 1991
Individual Release Groups
0.8 j.
~
GI
•
I
4~
16'
•
0.6j
Nanticoke River 1992
Individual Release Groups
.-.
ii.i
•
3;
~
'2
GI
._ - -
0_:[
0
i
1
2
r
oLL
c::::
CI]
2
1.2 1.6
Larval Stage G/Z
0.4 0.8
•
2~
>
:::
-,
.2
äi
004 1
0
• •
004
0.8
•
•
1.2
1.6
2
Larval Stage G/Z
Pooted Release Groups
+ Nantlcoke R. 1993
•
+ Nanticoke R. 1992
+ Patuxent R. 1991
------2
0.8 1'.2 1.6
0.4
Larval Stage GIZ
Figure 4. Plots of overall survival of released striped bass larvae to the juvenile stage (mid-July) versus larval
stage GIZ ratio for larval releases in the Patuxent River (1991) and Nanticoke River (1992). In the bottom plot,
overall survival was pooled among release groups for each year and plotted against larval G/Z ratio.
•
10000
1000
t
l1
10J
1
~
-
Pax-91
e-
Nan-92
•
Nan-93
l --------.
\
_/
1 0 > ~...
o
40
80
120
~
160
200
240
Aga
Figure 5. Onlogcnctic changes in stripcd bass cohort biomass for \\ild lar...ac and jU\'cnilcs in thc Paluxcnt (1991)
and Nanticokc (1992, 1993) Ri\'crs. Note lhat for thc purpose of comparison. initial cohort biomass was
spccificd at 2000 kg, despite obser\'ed differences in cgg productions among years. Data uscd to dctcnninc
annual cobort biomasses arc prcscnlcd in Tablc 4.
BIomass
.,.
·_.~l·
10000
Halchery Z 2=0.025
10000
~~
Oi
1000
~
--
Lt~.-"_·-"_--~
(J)
~
E
o
äi
......
Cl
100
~
Halchery Z 2 =0.05
1000
'-'
(J)
(J)
cu
E
100
0
äi
10
1
10
1
o
40
80
120 160 200
Age (d posthateh)
240
0
40
80
120 160 200
Age (d posthateh)
240
-. - Hatchery
• Wild, ~=0.12
(J
Wild, ~=0.20 + Wild, ~=0.05
Relative BIomass
N
+-
......
aP
--e:!.(J)
(J)
(J)
ltl
E
0
äi
~
~
Cii
0::
1000
100
10
. ..;,::::::::::
1 ......
'\""'\\~
0.1
0.01
".
0.001
'D
0.0001
.
Hatchery Z2=0.05
I
.
.\.-.::.:::;:::.:.~._ ::~:::.:=:~:.~.:~~::~~~:~::.-_..•
o
40
......,.:.
80
120 160 200
Age (d posthateh)
240
Figure 6. Onlogenetic changes in striped bass cohort biomass for wild and hatchery larvae and juveniles. In the two upper plots, hatchery larval
stage mortalit)' is specified at low (22 = 0.025 doll or high (22 = 0.05 d·l) levels. Within each plot, three levels ofwild larval-stage mortality
Me spccificd. The lower plot shows biomass relative to initial biomass (BsfBo) at the higher hatchery larval mortality rate. A plot of relative
biomass allhe lower halchery morlality rale (not shown) indicatcd the same trends in biomass relative to age.
..
Hatcherye=0.025
a>
~
C
o
0.8
'C lU
0.6
C E
o 0
0.4
>.....a>
0.2
*~ ..-..
::J l/)
.cl/)
U]5
.c
B
lU
I
•
1
o
eHatchery
1
• I
---
0.8
..-+
--- -
0.6
/---
/,/
••
~.&_.••• _ _ •.• I "~
o
40
'
80
0.4
0.2
l..._.
"'_,
120
160
",
,,_ ...
~ •• _
200
o .... __~_.'-.
o
240
Age at Stocklng (d post hatch
40
v,
1500
900
2000
1600 -
'_._-~
.,.
I
80
~._
. . . _.,. . _.
120
L_._....
160
J
......
200
.~.._....•_-_ ... _.. _..
1200
800
ltf ":..:..::.::: .::: .... ";.:': ':":.:"'.':. :...".:'.
300
o
40
80
120
160
200
400
240
0· ....--...
o 40
,
Wild, Zt=0.20
80
120
160
200
240
Age at Stocking (d post hatch
Age at Stocklng (d post hatch
(
_~
•
I
600
240
Hatchery ~ =0.05
.~
1200
.
Age at Stocklng (d post hatch
Hatchery ~=0.025
N
...
~=0.05
•
.-'.
Wild, Z2=0.12
Wild, Z2=0.05
Figure 7. Hatchcry contribution rates (hatchery biomass/(halchery + wild biomass» of slriped bass stocked at 7, 55, or 220 days after hatch.
The lwo lower plots show Ihe cost of conlributing 1% 10 lhe overall biomass (wild + hatchery) of slriped bass stocked at 7, 55, or 220 days
after halch. Scenarios ofwild and halchcry larval mortalily rates are shown.