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Feeding Behavior, Prey Consumption,
and Growth of Juvenile Red Hake
a
J. J. Luczkovich & B. L. Olla
a
a
National Marine Fisheries Service, Northeast Fisheries Center,
Sandy Hook Laboratory, Highlands, New Jersey, 07732, USA
Available online: 09 Jan 2011
To cite this article: J. J. Luczkovich & B. L. Olla (1983): Feeding Behavior, Prey Consumption, and
Growth of Juvenile Red Hake, Transactions of the American Fisheries Society, 112:5, 629-637
To link to this article: http://dx.doi.org/10.1577/1548-8659(1983)112<629:FBPCAG>2.0.CO;2
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Tra.•octio•ts
o] theAmer•cau
Fl•heriesSoviet
3' 112:629 637, 1983
Copyrightby the American FisheriesSociety1983
Feeding Behavior, Prey Consumption,and Growth of
Juvenile Red Hake •
J. j. LUCZKOV1CH
2 ANDB. L. OLLA3
National Marine FisheriesSe•'ice, .VorlheastFisheriesCenter
SandyHookLaboratory,
Highlands,
.VewJersey
07732
Downloaded by [Oregon State University] at 16:51 02 September 2011
Abstract
Juvenilered hake Urophycis
chuss
were collectedwhile they were inhabitingseascallopsPlacopecten
magellanicus,
and the effectsof appetiteand food availabilityon prey consumptionand
growth were examinedunder laboratoryconditions.Fish took increasingamountsof live amphipodsGammarus
annulatuswith increasingperiodsof food deprivationup to 40-50 hours.
The largestportionof a mealwasconsumed
withinthe first3 minutesfollowingprey introduction.
With longerperiodsof fooddeprivation,red hakeincreased
the timetheir chemosensitive
pelvic
fins were extended,indicativeof a rise in feedingmotivation,The averageamountof sand
shrimpCrangonseptemspinosa
consumedby fish was7.4% of bodyweight/day. Under conditions
of high prey abundance,fish grewat ratesequalto field growthrates,but underconditionsof
low prey abundance,growthrate wasinhibited.Prey availabilitycan influencethe growth rate,
which might lead to sizedifferentialswithin a cohort,
ReceivedNovember 1, 1982
AcceptedMay 29, 1983
The growthof fishesdependsin large mea- sick 1969; Wilk and Morse 1979). The larvae
sure on the amount
of food
consumed.
The
amountconsumed,in turn, dependson a variety
of factorsincludingfoodavailability(Ivlev 1961;
Elliott 1970)and appetite(Beukema1968;Brett
hatch in the plankton, spend 1-2 months as
pelagicjuveniles, and, after reachinga sizeof
23-49 mm total length (TL), descendto the
bottomwheretheycommonlylive symbiotically
1971; Elliott 1975). In order to estimate accu- in themantlecavityof theseascallopPlacopecten
rately the potentialamount of food that may magellanicus
(Goode 1884; Musick 1969). This
be consumed, it is essential to understand the
association
persistsfor 2-3 monthsuntil the fish
preciserole that food availabilityand appetite outgrowthe scallops(Steineret al. 1982). The
playin feedingbehavior.Consideringthesetwo sizeof fish found in scallopsrangesfrom 23 to
factorsin thispresentwork, we haveexamined 136 mm TL (Musick 1969; Steiner et al. 1982).
the food consumptionand growth of juvenile Juvenilered hake apparentlygain only shelter
red hake Urophycis
chussfed live natural prey from this relationshipand laboratory studies
itemsunder controlledlaboratQryconditions. haveshownthat the fishwill useother typesof
The red hake is a marine gadid that occurs shelter, such as clam shells,the perimeter of
on the continental
shelf of the northwest Atlive scallops,
and sections
of pipe (Steineret al.
lanticOcean,rangingfrom NovaScotiato North 1982). Laboratory observationsand field colCarolina(Musick1974). The specieshasan ex- lectionsmade throughout the day and night
tendedspawningperiod lastingfrom April until haveshownthatjuvenilered hakeemergemost
October 'Hildebrand and Schroeder 1928; Muoften from shelterat night whenthey are most
active (Steiner et al. 1982).
• Based•n part on a Master'sthesis(J. J. L.) submitted to RutgersUniversity,New Brunswick,New
Jersey.
=Current address:Departmentof BiologicalSciences,Florida State University,Tallahassee,Florida
32306.
• Current address:Schoolof Oceanography,
Oregon State University, Marine ScienceCenter, Newport, Oregon 97365.
629
In this studywe determined,from field collections,the typesof preyconsumed
by red hake
while they were associatedwith sea scallops.
Then, under controlled laboratory conditions
and usinglive prey, we describedthe method
of prey captureand measuredthe amountconsumeddaily. In addition, we examinedthe effectsof food deprivationon the rate of prey
consumedin a mealand the effectof prey abundanceon growth rates.
630
LUCZKOVICH AND OLLA
Downloaded by [Oregon State University] at 16:51 02 September 2011
Methods
contentsidentified to the lowesttaxon possible
under a binoculardissectingmicroscope.The
Animal Collection and Maintenance
results are expressedas percent occurrence
Sea scallops were collected at 40ø13'N, (number of stomachscontaining a particular
73ø48'W with a 1.2*m scallopdredge, then food item divided by the number of stomachs
transported immediately to the Sandy Hook containingfood).
Laboratory in aerated seawaterheld in temFeedb•gDeprivationStudies
perature-insulatedcontainers.Seawaterbottom
Four red hake of similar size (86-100 mm
temperatures,at the time of collection,ranged
from 4.0 to 4.9 C and the depth ranged from TL; 3.3-5.9 g wet weight) were selectedfrom
27 to 35 m. In the transportcontainersand holding aquaria and placed into four 15-liter
subsequently
in laboratoryaquaria,juvenilered glasstestingaquaria (38 cm X 25 cm X 15 cm)
hake graduallyemergedfrom the mantlecav- with 3 cm of clean sandand a sectionof polyitiesof the scallops.Fish and scallopswere held vinylchloridepipe(2 cm diameterX 5 cm long)
together in 800- and 1,000-liter aquariaprovided with running seawater,aeration, and a
that afforded
shelter.
A continuous
flow of sea
water wassuppliedto each tank at an average
sand-gravelbottom. Fish were fed, three times flow rate of 0.8 liter/minute and a mean temeachweek,live amphipodsGammarus
a•nulatus, perature (_+SD)of 10.2 _+0.65 C. Above each
sandshrimpCrangonseptemspi,wsa,
or chopped aquariumwassuspended
a 2,000-ml separatory
surfclamSpisula
solidissima.
Amphipods
andsand funnel containingseawater and 50 live amphishrimp were usedas prey in experimentsbe- pods G. a**nulatus.To initiate a feeding bout,
causestomachanalysisshowedthem to occur the stopcock
of the separatoryfunnelwasopened
naturally in the diet. Temperature (_+SD)and and waterandamphipodswereintroducedover
salinity(_+SD)were held at 10.7 _+0.76 C and a 2-minuteperiod (Fig. 1). Blindswith viewing
23.5 _+ 1.55%o,respectively.Temperature was slits isolatedthe experimenter from the fish,
comparable to field water temperature at the and blindsalsowere placedbetweenaquaria so
scallopcollectionsiteduringthe monthsof peak that fishwerevisuallyisolatedfrom oneanother.
red hake occupation(Steineret al. 1982). The Light intensitywas42 lux during the day and
photoperiodsimulatednaturalseasonal
changes; 1.4 lux during the night, and all feedingswere
timers that controlled fluorescent lights were conductedduring the night whenred hakeare
adjustedweekly.Daytime light intensityaver- normallymostactive.
aged400 lux and night intensity0.5 lux.
Fishwereacclimatedto testaquaria3-12 days
For studiesof feedingdeprivationand daily
food consumption,experimentalfishwere held
and testedunder a light regime in which the
dailylight cyclewasreversed;that is,night light
intensitiesoccurredduring the normaldaylight
period, and vice versa.This changewasmade
approximately5 weeksbefore testing.The fish
adaptedto thisnew cycleasevidencedby their
greateractivityduringthe subjectivenight;red
hake are normally mostactive at night (Steiner
tical but food-free aquarium. The deprivation
intervalbeganat the time of transferand ended
with a subsequentintroduction of 50 amphipods. Again, after 15 minutes, each fish was
transferredto another food-freeaquarium.The
numberof amphipodstaken wasrecordeddur-
et al. 1982).
ing each 15-minutefeeding, as was the time
Stomach
Analysis
One hundred thirty juvenile red hake (2393 mm TL) werecollectedfrom seascallopsfor
stomachanalysisand were immediatelypre-
before they were tested,and fed G. am•ulatus
during this period. An experimentbeganwith
the introductionof 50 amphipods.After 15
minutes, each fish was transferred to an iden-
sinceintroductionfor eachingestion.The num-
ber of amphipodseatenwasmultipliedby the
meanwet weight of an amphipod(either 21 or
45 rag)to obtainthe wet weightof a meal. Each
subsequent
deprivationintervalbeganand end-
served in 5% formalin. All fish were collected
between 1000 and 1400 hours eastern standard
ed in the same manner.
time at approximatelymonthly intervalsfor 1
an event recorder was used to measure, for 180
Immediatelybefore eachprey introduction,
year(November1979to November1980).Sub- seconds,the duration of pelvic fin extensions
sequently,the stomachs
weredissected
and the past a 90ø angle with the fish'sbody (Pearson
FEEDING BEHAVIOR
2000ml
of
AND GRO%'TH OF YOUNG RED HAKE
631
of eachtest.After 82 hours(four night periods
and three day periods),the numberremaining
seawater
was counted.
The
number
eaten was calculated
Downloaded by [Oregon State University] at 16:51 02 September 2011
50 Amphipods
by difference.Testswere first performedwith
10 sandshrimp(combinedweight,4.9-5.9 g),
and then repeatedwith 25 sandshrimp(13.2continuous
seawater
15.5g) per tank. The foodintakewasestimated
addition
asthe numberof sandshrimpeatenmultiplied
by the meanweight of a shrimp,which wasdeterminedseparatelyfor eachgroupof preythat
wasadded.When weightsof shrimpwere unavailable,but lengthswere, wet weightswere
estimatedfrom a regressionof wet weight on
length (Luczkovich1982). The wet-weightestimate of food consumptionwasconvertedto a
percentageof bodyweightfor eachfish,which
was divided by 3.42 (the number of 24-hour
periodsin 82 hours)to gain a daily value.
In order to compareconsumption
whenprey
were continuouslyavailablewith consumption
when prey were available only during nightApparatus used in deprivation study
time, we performed a secondset of 82-hour
F]Ou•tE1.--The aquariumandapparatus
usedtodeliver tests.Sandshrimpwere introducedat the onset
•15
liter
,•
glass
tank
,.•shelter
!
50 liveamphipods
tojuvenileredhakeduringthefood- of darkness and removed and counted at the
deprivation
and satiationstud)'.After each15-minute end of eachnight. These testswere first done
feeding,
fish weretransferred
to an adjacent
food-free with 10 shrimp (4.9-5.9 g) per introduction,
aquarium
for theprescribed
deprivation
period.
then repeatedwith 15 shrimp(7.4-8.7 g). The
difference
between
initial
and final counts was
usedto calculatefood consumptionas a peret al. 1980). The pelvicfinsof thisspecies
have centageof body weight per day, as described
chemoreceptorsand function behaviorallyin above.
foodgathering(Herrick 1904;BardachandCase
Growth
1965).
Daily FoodConsumption
Red hake (93-139 mm TL; 5.7-27.3 g wet
weight)were chosenrandomlyfrom holding
aquariaand placed,one per tank, into eachof
six 116-literfiberglassaquaria(95 cm X 35 cm
X 35 cm)with3 cmof sandcoveringthebottom.
A seascallop(125-135 mm valveheight)was
placed in each tank to serve as shelter. The
tanks were arranged so that the fish were visuallyisolatedfrom one another.Seawater was
kept at a flow rate of 2 liters/minute; mean
temperaturewas10.7 + 0.79 C. Photoperiod
averaged14 hourslight and 10 hoursdark during the testingperiod,andlight intensitieswere
the sameas for holding aquaria. In order to
estimatedailypreyconsumption,
a knownnumber of sandshrimp(meanweightper shrimp=
0.56 g; range0.49-0.62 g) were introducedin
a batch into the test aquariaat the beginning
To determinethe effectsof food availability
on the growth of red hake, growth wasmeasuredunder two differentlevelsof prey abundance,high and low. Similarly-sized
red hake
were placed, two per tank, in six 290-liter fiberglasstanks(120 cm X 45 cm • 53 cm) with
a viewingwindow,sandbottom,and two large
seascallops
(115-147 mmvalveheights)for use
as shelter.The tankswere suppliedwith running seawater from the samesourceand the
temperatureaveraged11.1 _+0.48 C. Ten sand
shrimp (mean= 0.46 g/shrimp) were placed
daily at 1530 hoursinto each of three tanks.
This numberwasequivalentto an averageratio
of 17.8%(9.3-32.1%) of body weightper day.
Because
the amountof preyavailablewasgreater than the amount eaten in our daily-consumptionstudies,thesedensitieswere considered high prey abundance.Into the remaining
three tanks, 10 sand shrimp (mean= 0.49
632
LUCZKOV1CH AND OLLA
g/shrimp)wereplacedeveryfourth dayat 1530 tocheirus
pinguis,Monoculodes
edwardsi,Ericthohours.Thisdensitywasequivalentto anaverage niusrubricornis,
and Phoxocephalus
holbolliand
ratio of 4.3% (1.7-8.2%) of body weightper copepodsCentropages
sp., amphipodsand co-
Downloaded by [Oregon State University] at 16:51 02 September 2011
day.Because
the amountof preyavailablewas pepodsoccurringwithequalfrequency.
Mysids
lessthan the amount eaten in our daily-con- and cumaceans contributed little to the diet.
sumption studies,these densitieswere consid-
Unidentifiable
eredlowpreyabundance.Every8 daysoverthe
24-dayexperiment,the fishwereremovedfrom
the tanks, weighedto the nearest0.01 g, and
curredfrequently,but neverin largequantities.
measured
soluteincreasesin length and weight were the
Typically,before prey were introducedto
aquaria,somefishwereswimmingslowlyover
difference
the substrate while others were inactive, shel-
to the nearest
between
initial
millimeter.
The
ab-
and final values for
noncrustacean
material
oc-
FeedingBehavior
any interval. The specificgrowth rate (G) was tered either within or under scallops,or next
calculatedfor any intervalby
to tankwalls.Whenfishsearched
for food,they
swamjust abovethe substratewith pelvic fins
extended in front and to the side of the head,
lightly touchingthe substrate(Herrick 1904;
X/is the final lengthor weight,Xi is the initial Bardachand Case1965; Pearsonet al. 1980).
lengthor weight,and d is the numberof days
Uponintroductionof livesandshrimpor amin the interval (Ricker 1975). In addition, the
condition factor (K) wascalculated on each mea-
phipods,someof the red hake immediately
chasedand attemptedto captureprey still in
surementday by
the water column.
K = 100W/L"
W is the weightin grams,andL is the lengthin
centimeters(Weatherly1972).
Analysisof covariancewasusedin the dailyconsumptionand growth experimentsin order
to comparetreatment groupscomprisedof fish
Inactive
fish became active
andexhibitedcharacteristic
food-searching
behavior.Fishoften did not appearto detectan
inactivesandshrimpor amphipod,even when
close to or swimmingover one. However, if
contactwere made (usuallywith the extended
pelvicfins)and the prey moved,the red hake
attempteda capture.Some prey were small
of different
initial sizes.
enoughto be ingestedwhole.Others,too large
to beingested
whole,wereheldin the fish'sjaws
Results
and eventuallyswallowedheador tail first, this
StomachAnalysis
takingaslongas 15 minutesto complete.
Attackswerenotalwayssuccessful.
The sand
Juvenilered hakeassociated
with seascallops
shrimp
were
able
to
spring
from
the
substrate
fed predominantlyon crustaceans(Table 1).
Decapods(sand shrimp) were the most fre- into the water columnwith a rapid flexure of
quently occurring crustaceans,followed by the abdomen, then swim to another location
gammarideanamphipodsUnciolairrorata,Lep- and resettle.Amphipodsswamawayrapidly,
changingthe directionof their escapecontinually. Somecapturesoccurredafter little or no
pursuit,but othersfollowedmanyrepeatedes-
T^BI.W1.--Stomachcontents'
ofjuvenileredhakecollected
capesand pursuits.
in association
withseascallops.
Valuesarepercentages
of the83 stomachs
withfood that contained
eachitem.
t•ffectsofFoodDeprivation
Meanfish totallengthwas48 mm(range23-93 ram).
Foodcategory
Total Crustacea
Unidentifiable
Occurrence(cA)
79.6
28.9
Decapoda
Amphipoda
Copepoda
Mysidacea
26.7
! 0.8
10.8
6.0
Cumacea
Unidentifiable
1.2
noncrustacean material
20.5
The meanweightof amphipodsconsumedin
each15-minutefeedingbout increasedwith the
duratim• of food deprivation,and reachedan
apparentasymptoteat 7-9% of body weight
after 40-50 hoursof deprivation(Fig. 2). The
largestpercentageof each 15-minutemeal was
alwaysi•gestedin the first3 minutesregardless
of the lengthof deprivation,althoughthe number of amphipods
eatenduringthisintervalin-
FEEDING BEHAVIOR AND GROWTH OF YOUNG RED HAKE
15
T ^m.E2. Meannumbers
ofamphipods
eatenbyjuvenile
redhakeduring3-minuteintervalsofa 15-minute
bout,
relatedtothetimeo]priorfooddeprivation,
basedonat
leastthreereplicates
ofjburfish.Withinthecolumn
with
a significant
F value(analysisof variance),meanswith
a letterin common
are not significantly
different(least
significant
differences;
P < 0.05).
:I:13
•
12
11
m
9
•
7
,,,
6
633
Hours
of
food
depri- Intervals
inafeeding
bout
(minutes)
vation or
statistic
0-3
9-12
12-15
l.la
0.1
3-6
0.5
6-9
0.2
0.3
2.6b
3.6b
5.2c
0.7
0.9
1.0
0.2
0.2
0.6
0.1
0.3
0.5
0.2
0.3
0.6
2.265
1.311
1.954
2.185
NS
NS
v
6
z
4
18
24
>40
Downloaded by [Oregon State University] at 16:51 02 September 2011
t-, 3
0
2
u.
I
0
F(3,57d 0
P
0
20.897
<0.01
NS
NS
10 20 30 40 50 6'0 70
HOURS
OF
FOOD
DEPRIVATION
Fmt•RE2.--Fifteen-minute
foodintake(% ofbodyweight) or the amountof time the predatorandthe prey
ofjuvenileredhakeversusthehoursofpriorfoodde- were held together.
privation.Pointsare means(+ 1 SE)for fourfish, and
PreyAbundance
and Growth
valuesat 6, 18, 24, and 30 hoursoffooddeprivation
werepooled
from morethan onefeedingaftersimilar
Over 24 days,red hakefed 10 sandshrimp
deprivation
periods.
daily (high prey abundance)grew significantly
creasedwith deprivation(Table 2). In each30minute interval that followed, the mean num-
faster than thosefed 10 sandshrimpevery 4
days(lowpreyabundance)
whetherthemeasure
wasabsoluteor specificdailyincreasein length
or weight (Table 3). Conditionfactors(K), not
ber consumedwasnot significantlyaffectedby
deprivation.
•80
Extensionof pelvicfin raysduringthe 3 minutes before prey introduction,a measureof
feeding
motivation,
was
ofshort
duration
after • •s0
z
6 and 18 hoursof food deprivation(Fig. 3). Fin
extension
became
mostpronounced
after24-
o
• •a0
40 hours, and again after 72 hours of depri-
-
vation,butoccurredfor shorterperiodsof time
o
after 40-50 hoursof deprivation.
•
DailyFood
Consumption
Red hake ate 1-7 sand shrimp during 82
"-
90
• 60
z
hours;
theiraverage
dailyconsumption
was7.4% ou.
30
(1.4-16.3•)of bodyweight.
Thispercentage•
decreased
asthe weightof the fishincreased •.
(Fig.4). Therewereno significant
differences
amongthe meanamountsof shrimpconsumed
0
4'0'
.ou.s
' .;o ' sb '4o' io
ooo
dailyunder any of the four conditionsof prey
red hake exavailability:10 or 25 sandshrimpavailablecon- F1GUR•3.--Mean time(seconds)juvenile
tended
their
modified
peh,ic
fins
in
a
3-mmute
pre-feeding
tinuously;10or 15sandshrimpavailableduring
observation
period,versus
thehoursofpriorfooddeprithenightonly(analysis
ofcovariance,fishweight
vation.Means(_+1 SE)arebased
onfourfish,aadvalues
used as a covariate: F = 1.45; df=
3.18; ? >
0.25). Thus, the mean daily consumptionwas
not affectedby eitherthe shrimpdensities
used
at 6, 18, 24, and 30 hoursoffooddeprivation
were
pooled
from morethan onefeedingaftersimilardeprivationperiods.
634
LUCZKOV1CH AND OLLA
PREY
PER
and off the coast of Maine (Garman 1983)
AQUARIUM:
• 12•continuously
available
showeda diet dominatedby sandshrimp and
A10
• 151
available
only
during
night amphipods.
Chemoreception
playsan importantrole in
food detection and localizationby red hake
(Herrick 1904; Bardach and Case 1965; Pear-
Downloaded by [Oregon State University] at 16:51 02 September 2011
WET WEIGHT OF FISH (grams)
F]CVRE4.--Dail)' consumption
(% offish bod)'weight/
da)')of sandshrimpby individualjuvenilered hake
versus
thewetweightof each
fish underdifferent
conditionsofpreyavailabilit)'.
significantly
differentbetweenthe two groups
on day 1, were greaterfor the groupwith high
prey abundanceby day 24.
Discussion
sonet al. 1980). In our experiments,however,
fishingestedprey in the watercolumn,but were
stimulatedto pursuepreyalongthe bottomonly
when the prey were active, which often occurred after the prey had been contactedby a
fish searchingfor food. This suggeststhat vision, at leastunder certain conditions,playsa
role in mediatingfeedingbehavior.
The amountof food taken by red hake in a
mealincreasedwith the lengthof time theywere
deprivedof food, until an apparentasymptote
was reached. Similar patterns have been observedin other species:
for example,sockeye
salmonOncorh3'ncus
nerka(Brett 1971); brown
trout Salmotrutta(Elliott 1975);sweetlipParapristipoma
trilineatum,
jack Trachurus
japonicus,
puffer Fugu vermicularis
porphyreus,
filefishStephanolepiscirrhifer,and rainbow trout Salmo
The predominance
of crustaceans
in the diet
ofjuvenilered hakegenerallyagreeswithwhat
hasbeenreportedby others.For example,red gairdneri (Ishiwata 1968a). If the maximum
hake collected on the continental shelf between
amountof foodeatenvoluntarilyby a fishin a
Nova Scotiaand North Carolina (Bowman1981) singlemeal is a measureof stomachcapacity
T^BLE3.--Twent).-four-da)
•growthand condition
of redhakeJ•d sandshrimpat tworates.
Absolute
Total length
(mm)
Fish
Day 1 Day 24
24-dayincrease
b
Weight (g)
Day 1
Day 24
Condition(K)•
Day I
Day 24
Length
(mm)
Specificgrowth
rate (%/day)'
Weight
(g)
Length
(mm)
Weight
(g)
High prey availability (10 sandshrimp/day)
I
2
3
4
5
6
92
107
116
125
127
133
I25
143
142
153
152
157
5.79
8.45
9.56
12.18
11.33
15.00
I3.71
22.00
20.67
28.04
26.49
27.02
Mean
0.74
0.69
0.61
0.62
0.55
0.64
0.70
0.76
0.72
0.78
0.75
0.70
33
36
26
28
25
24
7.92
13.64
11.11
15.86
15,16
12.02
1.28
1.21
0.84
0.84
0.75
0.69
3.59
4.00
3.21
3.47
3.54
2.45
0.642
0.735
28.7
12.62
0.935
3.38
4.74
4.15
9.44
7.91
7.71
11.24
0.73
0.64
0.92
0.70
0.44
0.36
2.11
1.78
2.84
2.08
1.17
1.09
7.53
0.632
1.85
Lowprey availability (10 sandshrimpevery4th day)
I
2
3
4
5
6
Mean
104
108
114
121
152
178
124
126
142
143
169
194
7.18
7,76
9.68
12.20
23.72
37.72
11.92
ll.91
19.12
20.11
31.43
48.96
0.64
0.62
0.65
0.69
0.68
0.67
0.63
0,60
0.67
0.69
0.65
0.67
20
18
28
22
17
16
0.658
0.652
20.2
a(K) = 100(weight)/length)L
Day-24meansweresignificantly
differentbetweenfi•edinggroups(Student's
t-test;P < 0.01).
bFeedinggroupsweresignificantly
differentby analysis
of covariance:
length,P < 0.02;weight,P < 0.01.
' Specific
growthrate= 100(1og•X•4
- log•X0/24;X - lengthor weight.Feedinggroupsweresignificantly
differentby
analysis
of covariance:
length,P < 0.05;weight,P < 0.01.
FEEDING BEHAVIOR AND GROWTH OF YOUNG RED HAKE
Downloaded by [Oregon State University] at 16:51 02 September 2011
(Fange and Grove 1979), we would conclude
that stomachcapacityof juvenile red hake averages7-8% of bodyweight.
The tendencyofjuvenile red haketo eat the
bulk of a meal early in a feedingbout alsois
typical of other speciesstudiedin this regard.
Rainbowtrout andjack mackerelate the bulk
of a mealin 10 minutes,and puffersand filefish
in about 2 minutes(Ishiwata 1968b), sockeye
salmon in 8 minutes (Brett 1971), and threespine sticklebacksGasterosteus
aculeatusin 9
minutes (Tugendhat 1960). Threespine sticklebacks, like red hake, increased their food-con-
sumptionrate with increasingperiodsof food
deprivation.
The rapidity with which juvenile red hake
consumea meal leadsus to concludethat they
are time-minimizers(Schoener 1971); that is,
theycaptureasmuchfoodaspossiblein a short
period of time. In addition, their consumption
of food in discretemealswouldclassify'
them as
discontinuous
feeders(Brett 1971; Elliott 1975).
Feedingin this way wouldenablethesefishto
take advantageof resourcesdistributed transientlyin spaceand time, and would be of selective
value
since it would
shorten
the time
635
tensionwith increasedfood deprivation appar-
entlywasassociated
with an increasein feeding
motivation.
The
decrease
in fin extension
be-
tween 50 and 60 hours of food deprivation
probablywasdue to a changein the red hake's
foodsearchingstrategyrather than a decrease
in the feeding motivation,becausefood consumptionremained high over this range. The
resultof thisdecreasein food searchingmaybe
a savingin energyexpenditurein environments
where food maybe scarce.
Differencesin growth rate betweendifferent
yearclasses
in bothyearlingsandolderfishhave
been observedfor red hake by Rikhter (1973),
who speculatedthat suchdifferencescould be
causedby changesin the foodsupply.Although
there wasno evidenceto supportthis, our own
laboratorydata suggestthat the availabilityof
foodcouldplaya rolein modil•Sng
yearlygrowth
rate so that fish of the sameage could be different sizes.When the possibilityof an overlap
existsin the sizesof differentagedfish,the practice of usingan age-length distributionfrom
one year to determineage structurein subsequent yearsmay lead to spuriousconclusions
about the age compositionof the population
(Westrheim and Ricker 1978).
spentforagingawayfrom shelter.
The mean specificgrowth rate in length
The meandailyconsumption
byjuvenile red
hake(7.4% of bodyweightfor 5-22 g fish)falls (0.94% TL/day) for fishin the high-prey-abunwithin a range of valuesobtainedin laboratory dancegroupswasverycloseto valuesgivenfor
studieson other fishesof similarsize:threespine laboratory(1.00% TL/day) and field (0.93%
sticklebacks,12.1cAof wet body weight (Beu- TL/day) growth rates at similar temperatures
kema 1968); black acarasCichlasoma
bimacula- by Steineret al. (1982), whereasfish in the low
turn,14%of dry bodyweight(DavisandWarren prey abundancegrew at a much slower rate
1968);sockeyesalmon,6.9% of dry bodyweight (0.63% TL/day). Steineret al. (1982) found a
(Brett 1971); and Micropogon
opercularis,
3.3- positivecorrelation betweentemperature and
4.6% of wet bodyweight(DeCiechomski1981). specificgrowthin length.However,in the study
Dailyconsumption
for a 5-g red hake(11-12% reported here, temperature was constantfor
of bodyweight)washigherthanthe single-meal fishin both high and low prey abundance,and
consumption(8cAof bodyweight)for a similar- could not have caused the observed differences
sizedred hake, indicatingthat the fish could in growth rates.
Similar studies, conducted on winter flounder
take more than one meal per day.
The amount of sand shrimp consumedin a Pseudopleuronectes
americanus
(Tyler and Dunn
platessa(Jobling
dayrelativeto bodyweightdecreased
asthe size 1976) and plaice Pleuronectes
of a fish increased, similar to what has been
1982) showedthat when food rationswere lim-
shownpreviouslyfor other species(for exam- ited, the growth rate decreased.Our studydifple, Brett 1971). However,becausedensityof fered in that two differentdensitiesof live prey
preywasheldconstant,the rationdecreased
as were offered as food and thus rations for the
the fishsizeincreased.This makesit impossible fishin thesedensitieswere different.Although
to separatethe effect of fish size from ration
the rations were somewhat
size.
attempt to regulate prey densities,our results
do showa decreasein growth rate due to the
The increasein the duration of pelvicfin ex-
variable
due to our
636
LUCZKOVICH AND OLLA
decreased
preydensity.Thus,juvenilered hake GODDE,G. B. 1884. Part 3. Fishes.Pages 163-682
in The fisheries
andfisheryindustryof theUnited
of the sameagecouldbe differentsizesdue to
States.
Section
1.
Natural historyof usefulaquatprey availabilityin the environment.
ic animals. United States Commission of Fish and
Acknowledgments
We thankA. Bejda,F. Farwell,D. McQuillan,
W. Menezes, S. Miller, J. Otis, C. Roe, W. Stei-
Fisheries,
Washington,Districtof Columbia,USA.
HF•RRICK,
C.J. 1904. The organand senseof taste
in fishes. United
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States Fish Commission
Bulletin
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Fishesof Chesapeake
Bay.UnitedStatesFishand
ner, andA. Studholmeof the SandyHook LabWildlife
Service
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Bulletin53:159-160.
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during all phasesof
IStnWA'I'A,
N. 1968a. Ecologicalstudieson the feedthis study.We also extend our thanksto A.
ingof fishes--II I. Degreeof hungerandsatiation
Framefor her aid in identifyingthe amphipods,
amount.Bulletinof theJapaneseSocietyof Sci-
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M. Cox for her illustrations, and E. Waldhauer
entific Fisheries 34:604-607.
for her patienttyping.This work wassupport- ISHIWATA,N. 1968b. Ecologicalstudieson the feeding of fishes--IV. Satiationcurve.Bulletinof the
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