瀬戸内水研報（Bull．Fish．Envion．InlandSea），No．2：131−133（2000）

Short

Communication

Effect ofWater Flow Rate and Washing D皿ation on the
Recovery Rate oflchthyoplankton from a Bongo Net
Naoaki

AbstractThenumberof

ichthyoplankters

114and1281iters／min）over
sarytofully

after2minItwasrecoverwashing

min

in

the

washing

samples

werefroma

Bongo

the

four

flow

rate

conditions

that

theoptimal

now

rate

undercompare（lichthyoplankton

inestimate（ilO

Kononetafter

didnotfour

dif￡erentflow

to（1eteminethea

recoverytow，

differAII

significantly

was1061iters／min。Further，itrates（74，97，procedurewasneces−rates

atand

fromeachotheL

foundthattoostrongaswellastooweakHowratecanreducerecoveryefficiency。Awashingprocedure
optimalflow

ichthyoplanktonofthefromrate

aand

Bongo

lmin

washingisjudgedsufficient

tofully

recover（＞99％）the

net，

Key

words3Bongonet，ichthyoplankton，recovery

rate，washingnets

arewith4and6stations，respectively。Washing

andconical nets fixed to a ring frame（McGowan andBrown1966）． This net is recommended as the bestprocedureswere

netswerewashe（icollectiongeaゴor

fish．eachco（レendavoi（lanceoccurs

owing

Bongo

porosity

fitte（icharacteristics

apairofcylindrical−

eggsandIarvae，astothebri（ile−freeof

thenet（S血thminimumand

and

net
high

Richardson

performed
for

were

secondly，thewashingsamethemamerasfollows：both．

O．5min，andthencollections

separately

and

same

sampling

wasperiod（SampleintheII）；thirdly，alRichardson1977），theichthyoplanktontheassesse（1aswell

as

nets．

usu＆lly

aims

The

takes

manualonly

ato〔ietermine

recoverrequiredinto

precisely

tontimefully

thethethemerelyfewto

cod−en（iotherstates

minutes

perproce（iureichthyoplankton

wash

the

not

been

haskindsof

thisoperation

net

ato

Bongo

from25to100m

inof

the

westemparttheSetobottomInlandonetoupper

fully

repeated

netbydepths）

Sea，Japan，onboar（1the RV Shirafuji−maru （138t）during thedaytime in May1997and June l998。The Bongo net

streamed（iownwasdistance

from

the

hose

the

the

designedsame

awashednozzle，thenway．

The

duration．

fromapproxi−

the

other

procedure

wasTheofshapethenetinpossiblearea．All

were倣edinbuffered10％se＆water

formalin

immediatelyandSample

upto

determined

numberto

gauze

areaofeachis5．3m2．An

2㎞ots

from

thetow

nets
at

rate

meshoblique

bothpartinwithinsamples

has335μm
netof

lower

the hose nozzle was deformed by applying pressure
from the washefs fingers so that washing seawater

diameter，and

gross

side

repeated4times（Samples皿

theapart

was（10ne

usedinthisstudywas3minlength，0。7minmouth
openings．The

partmately2mside

compa血g samples under various washing conditions・Collections of ichthyoplankton were conducted at

19stations（rangingwashing，after
thepaper．This

necessary

fromplank−

wasdoneinI）lto VI）l fimlly a5min washing was done（Sample VII）。
↑his g＆ve a total washing time of10min．During eachthe structure and towing
described in detail（Smith andseries

sampled（Sampleprocedurebeen

washing

sampling

deckl977，Mori1981）．Althoughhave

minfor

on

asof

a

preserved

theprior，R7（∫），inpercentage

ichthyoplankters

Sample

VIIl

R7（）＝

wide

as

toanalysis，Recovery

eachnumbercollection

relative

accumulatedfromtowasIV，theSample

I

at
Σ七，at

each

near−bottomstation．

Thenetwith

down

from

the

outside

hose

under

oneof

tothe

su㎡ace

was

after

each

towwaswashe（1saltwater

a24mm−caliber

fo皿different且ow

114and1281iters／min

flow

2000年1月24日受理（Acceptedrates
onmaderates；i．e。，74，97，

wereadopted

at3，6，×100＝1，・り，VII，1〉

wherex∫isthenumberThenumberof

from523to8，634eggs

ofichthyoplankters

ichthyoplanktersandinSample

collectedlarvae，withthel，varied

mean

January24，2000）

瀬戸内海区水産研究所業績A第13号（Con田bution No．A13from National Research Institute ofFisheries and Environment ofInland Sea）
河野悌昌：瀬戸内海区水産研究所 〒739−0452 広島県佐伯郡大野町丸石2−17−5（N，Kono：National Research Institute of Fisheries andEnvironmentofInlandSea，2−17−5Maruishi，Ohno，Saeki，Hiroshima739−0452，Japan）

Kono

132

100
ま》

据む

90

一◇一74iiters／min

一｛二卜971iters／min

4……

右114iiters／min−Q−1281iters／min

Φ

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3E≧

80

詑

−紹1タ00Fig。1。

2

Changes

ing

of

4

6

Washingtime（min）

recoverytime（min）at

8

rates（％）withfour

different

increasing

flow

0

1070

wash−

in

Flow

rate（liters／min）

washingtime（min）for（＞99．0％）of

bars

for

claritybetterof3，603．

representisthestandard〔1eviationforonegivenJapanese

anchovy，Eng7α読3ノαpon

dant

taxa

thein

recoverysi（leichthyoplankton

samples，Inrate

thevaried

Verticalbars

conditions

of

which

represent侃swerefirst

abun−

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between87．0％（741iters／

withinofthisca．1001iters／min

judge（lfrom

sufficientaBongo

Iwoul（11ikeandafter2min washing di（1not differ significantly fromeach other（Duncan s new multiple range test，p＞0．05）． Fig．2shows the required washing time torecover＞99％ofThe

theichthyoplankton

washing

weretimes

significantly

and1141iters／min（Duncansρ＜0．05）。This

that

now

rate

suggests

canTherelationshiptheflow

re（iucebetween

intheof74andlonger

new

to

thankrate（X，liters／min）cantheir

supportEnvironmentof9ク

multiple

range

test，strongasrecoverywell

astooefficiency．

washingtime（y，min）andbebyexpressedasec−

OndOrdereqUatiOn：comments

minimuminwashingthecasetimeofwascrew

the

field

Researchof

theandRV

toInstituteInlandSea）foron

manuscript．

theShirafuji−

Y．Hanamura

oftheirFisher−support

McGowan，J．A．and D．M．Brown，1966．A new opening−closingzooPlanktonnet．30吻pslnsムOo召αη08孔R㌍r一召nご6，66−23，VII十58pp、

Moh，K．，1981．Volumetricashθ7ごεshεSα6n孟

hε17s言sげ溺βπ∫，（22），29−52．（infor

estimate（1tobeat

lO61iters／min．Therefore，

sampling

review：R6poπげF

pelagicoffish

andichthyoplankton−

R召so麗κεs5h6万8s

lnvε5寛8α加n5わyA86ncy，／αpαn6s6Govθrn一Japanese）

S．L．Richar（1son，1977．

Pαp，，175，100pp．

Consequently，thetheReferences

Smith，P．E．and

y＝1．725×10−3（X−106．1）2＋0．568．

ainof

condi−

those

theis

l281iters／min

than

too

the

four

washingnet．

valuable

atproce（1ureichthyoplanktonandrates

washingminandrecoverystu（1y，theliesAlldeviation．

theforconditions。

standardandH．Zenitani（Nationalallthe

recoverandweak

now

rate

maru

rates

recoverydifferent

fully

recoverednowfullfourflowtomin）and99．1％（1141iters／min）（Fig．1），After2min
washing，985％or more of the ichthyoplankton weretions．

atonly。

Clupeidae，Scorpaenidae，Gobiidae

andin

130

115

100rateS（literS／min）．

VerticalI），the85

ChangeFig。2．

rates（1iters／min）．

value

γ＝1，725x10−3（κ一106．1）2＋0．568．9larvalStandar（1techni〔luesurveys。

E40F

3h．Tεoh、Recovery

rateofIchthyoplankton

ボンゴネット洗浄時における卵仔魚の回収率への流量と洗浄時間の影響
河野悌昌

曳網後のボンゴネットを途中で試料を回収しつつ延べ10分間洗浄し，魚卵と仔魚について洗浄時間に対する回収率の変化を調べた。4つの流量条件下において，洗浄開始から2分後以降の回収率間に有意差は認められなかった。99％を回収するために必要な時間は114，97，128，74〃minの流量区の順に短く，弱い流量と同様，強すぎる流量でも回収効率が低下することが示唆された。最も回収効率のよい流量は106Zと推定された。この流量で1分間の洗浄を行えば、ボンゴネット内の魚卵と仔魚を十分に回収できると考えられた。

133