瀬戸内水研報（Bull．Fish．Envion．InlandSea），No。3：47−51（2001）

Short

S皿faceSwarmandE砂hα〃sYukio

AbstractTheoccurrence

for

both

fertilized

andoroneuphausiids

thebehaviour

allat

Seto

water

maSS．

had

theor

sea

swarm

and

for

first

time

the

fully

consideredmatureha（1fully

branchiae．

nearly

empty

were

abreedingdeveloped

The

sex

assumetransported

that

from

the

thein

low

Sea，Japan．The

in

the

Foregut

feedingwithanalyses

the

l35mm

femalesejaculatory

activity

individuals

ChannelE翠hαμs如from9，0toover60％of

eitherswarming

Bungoof

Inlandlengthasunbiased，

event

Setobo（1ypopulation

wasKatayama＊2

strandingwestemspermatophores

ratio

Euphausiid

Sea，Japan

Sachietheadults，ranging

atheInland

subsequent
fromstomachs，indicating

surface，WeInlan（1Sea

Setosurface

ismalestheof

Kamizono＊2，andof

swarm

appendages

westemaconsistedalmosttheofreportedsexes．The

Stranding

αnαnαin

Hanamura＊1，Masato

nαnαBrinton，1962，iseuphausii（1swarm

Shore

Communication

showedduringofwereducts

thatswarming

E。nαnαinintmsionofathedeeper

Keywords＝ surface swarm，shore stran（1ing，Crustacea，Euphausiacea，E砂h側s彪nαnα，SetoInlandEuphausiid

c川staceans

ecosystem

due

anic
marilybut

inhabitants

someforming

speciesdensetoof

Sea

play

their
theatoce−

Kohno

pri−

great

abundanceinthewatersbathypelagiczones，

Ehime

Pre￡ecture

intheinwaters，and summer．Euphausiid fisheries，based upon shal−
low water aggregations，have occurred under electrickeymeso−andoccasionallyswarmsaroleinabundance。Theyoccurtheseatheareshallow

surface．E叩hαμslαl992，Sawamoto1997）。ThisnαnαBrinton，1962，E．pαcが診oαHansen，1911，andlights

sinceTh）7sαη06∬αn67〃乞themaximum

wellformknown

tos（Krφyer，1846），aresurface

aggregations）seasonally

in

and

the

subsurface

coastalspeciesswarms（orwatersof（Hirotathe1970sandor

close

Bungo

beforelanding

speciestoin

Ehimeand

Seto

Prefecture

tonsandin1988

Endo，1999），

sometimes￡oundthecom．），euphausii〔lsarenotEndo1984，Hanamura窃α」．1989，Hirota＆Kohno

marinetheInland

1992，Kuroda1994，Nicol and Endo1999）．
On30th March2000，a surface swarm by numer−

waters（average（1epth38m）。Indeed，no literature
hitherto reporte（1such a phenomenon，

fishermen

earlyinthemomingin

theinshore

Suo−nada，SetoInlan（1Sea（Fig，1）。

massofstrandingobservedon

athebeachwatersofSubsequently，aeuphausiid，E塑h側51αnαnα，wasof

Nagai−hama，Fukuoka

Pre￡ec−community

This

paper

subsequentInlandtheSea，andparticular

coastal waters of the westem North Pacific，mainly
occurring at depths of200−400m during the daytime

Prefecture，

an〔ieuphausiids

migratingtothe

upper200m

2000年9月18日受理（Acceptedonat

FisheriesandEnvironmentofandareon

theandthosesurfaceofthesw飢mαnαnαinhas

and

the

biologicalinformation
relating

factors

theshallow

The

toaSetoon
this

discusse（1・onwere obtained from eu−
Nagai−hama beach，Fukuoka

afternoon

March2000．There

component
toin

pers・

noof

the（aroundis

doubt

14．00

that

surfacetheswarm

hrs）ofstranded
had

theSeptember18，2000）

瀬戸内海区水産研究所業績A第15号（Contribution＊1花村幸生：瀬戸内海区水産研究所

night（Hirota

30thmajor
Sea（1ue

unusualindividuals

stran（1edaEμphα疏s

includesphenomenonphausiids

anof

population．

Numerous

伽phα麗s砂nαnαisdistributedinthesubtropicalreports

strandingstran（iedture（Fig．2），

Sea（Kohnoαα」．1996，Shibataofofspring

Swarming euphausiids have often been commerciallyexploited，particularly in northem Japan（Komaki1967，

ousplankt・niccrustaceanswasobservedby1・cal

Inlandincoastduringwas5000metricKohno1992，Nicol

occurswest

ChannelAlthough伽phα戚αnαnαisJapan・

theNo．A15from〒739−0452
InlandNatiQnal

Research

InstituteofFisheries

andEllvironment

広島県佐伯郡大野町丸石2−17−5（Y。Hanamura：NationalResearchofInland

Sea）

InstituteofSea，Ohno−cho，Hiroshima739−0452，Japan）＊2神園真人・片山幸恵：福岡県水産海洋技術センター豊前海研究所〒828−0022

福岡県豊前市大字宇島76−30（M．Kamizono

andS．

Katayama：Buzen−kaiLab・rat・ry，Fuku・kaFisheriesandM諭neTechn・1・gyCenter，Un・shima・Buzen−shi・Fuku・ka828−0022」apan）

Surface

swarm

and

strandingof

E叩h側349

αnαnα

100

50
40

80
30
ぷ

20ω

＞

60

0邸

5＝
①＝10−＞

び℃
⊆0』

やo50

Φ』

o40

L89101112｛3141520ρ

40Z

30

E50IV

llIll

20

Gut
10Fig．4。

Furegut

ful1；II，half

0891011て2131415
Body

Fig。3．

fullness

Sizefrequency

colu甲nsmatophore

theironof

E麗phα麗s如ηαnα（N＝indicatefemales

with

aFu

sper−

thelycum。

crustacean

setae．

infrequently

fOun（1．

Ourinduce

full；III，3／4fu11；IV，completelyUnidentified

understanding

surfaceswarmsofofplete．

En〔lo（1984）statedThe

E砂hαμsαραo静ocαin

ratio〇弟ocαinof

theSanrikuwithaslight

thoseonthesurfacecoastalmale

westof翫ph砿swaters且uctuates

α即一

around50％，predominance（En（101984），an（1coast50％males（Kotoriεswarms

ofHokkaido

consistsof30−α」．1995）。Incontrast，surface

spondwithrelated

intrusionthecold

ratherEpibionttocrustaceansex

infestation

ratio

host，including

mobilegreatly

activity

impairwithan（ltheE叩hα麗s如nαnαsample，nocoast

biasedof翫ρhα麗s

analyses

αnαnαhadstomachs（Fig．4）；nowasrevealed

feeding
watersthattheactivity．
haveα耽αandshown

similarly

low

Similarly，

discussedtheformation

E．∫，αo昴cα，giving

more

weightof

tosurfacephysicalindicatedfrom28th

March2000（Kamizono

association

with

that

ofstress。In

parasites

wereapproximately70％
and／omearly

empty

betweensexes

thenotobservations

infeeding

thislaboratory

inthe

coastalthis，theareaofwesterly
nearwindspers．obs。）．In

bottomBuzen−kaiintensifie（lwater

noticeably

temperature
decreased，reaching a minimum on30th March，when the su㎡aceof E塑hα麗3如nαηαoccurred（Fig。5）． There−swarm

Thisfore，it

isunlikely

inInlandSeawithJapaneseKanmonStrait．The
coast

engagethatthewarm

euphausiids

Tsushima

westerlywindinva（ledCurrent

may

drive

offshore，combinedwith

thetheBungo

thewater

E。Pα一

from

surfaceofactivities

duringMoreover，E。nαnαaggregates in the Bungo Channel inthis season（Hirota and Kohno l992）． The observe〔la〔leeperwatertheviainswarming behaviour at the sea surface（En（101984，Hanamura6∫α1．1989，Kotoriαα1．1995）． Suhαα」．

thethatthedaytime

fullnessThysαno召s3αZηα雁5fromswarms，suggesting

Current．

ofsouthward

exchange，inter−extemalgut

thecauseE．ηαnαdi（llowswarms

withacompletely

Previousofcorre−

contrast，Kodama

surfaceOyashioswarmswatersgas

asclear（1ifferenceswarmings皿facecom−

than physiological factors as causes（Komaki
1967，NishikawaααZ。1995，KotoriααZ。1995）。
Daily meteorological data from the Buzen−kai

effects

observed（記2test＝0．07，（lfニ11p＞0．05）．

in〔licatesinhave

which

fromnegative

observe（1．

Stomachofauthors

far

werehassometimes

fere

west

are

In

stronglyfemales（65．2−96．9％females）（HanamuraααZ．1989）。

athebehaviouLareswarmsexhibitoffmaterials

coastaleuphausii（ltowards

Hokkaido

T勿5αno召s5α伽r履s

to1／4

fu1L

mechanisms

thatS＆nrikuthatseveralofthean（11zumi（1994）suggested

ofswarms

breeding

egg−1ike

euphausii（issignificantlydif￡erentげtestニ1。98，df＝llP＞0．05）．
sex

nessE叩hα騰∫αnαnα：1，empty

than half full guts． Stomach contents of E．nαnαmainly consisted of small quantities of detritus andLength（mm）

distribution150）。Filledofmass

fromintrusion

ChanneL（1998）alsoobservedthat重ndividualsofE．ρα即り6αswarming phenomenon，however，can not be explainedby the water movement alone，since similar hydro−

fromgraphic

daytimeswarmsinthesouth−west

SeaofJapanpossesse（l nearly empty stomachs，in contrast toindivi（luals from nighttime swarms which had moreevents

Saito
Eμρhα那3

frequently（1996）
αs∫溺

occur

reportedinthethat1∫3Sars，1883，inarea，shore

strandings

SurugaofBay，central

50Hanamura，Kamizono

andKatayama

11．0

910，5了』
量

おユ10．O

Eo

←

＄

睾9・5

9．0

25

26

27

28

29

30

31

1

March2000
Fig．5。

the

ChangesinMarch

to2Apri12000．Arrow

strεしn（lingJapan，

areHe

found

also

seasonal

accompanied

and

that

E，

asmallbynealApri1

eventsrelatively

3Z配

1ofbottom

E配phα麗sregular5

strandings

of

other

number

water

mysid

and

hyperid

events・＆rethatstrandingsofハケcだphαn6sαμs〃α」

Sars，1883，0ntheTasmaniancoast

nouslywithmatting

evidence

iswithto

E叩h側5如nαnαstranding，

regardshouldnationofthebedonefactors

particular

tobetterunderstandmediatingsuchevents．

ofLaboratory

surface

Furtherfrom

eastemanic

DrResearch

Shimizu，forandofResearch

Inlandare

ourSea，Hiroshima，for

Ms

R．Shibataanunusualinstance

sea

bream

Pαg濯5灘のorcentral

toof

Seto

Inlandthesameof

Dr

of

Oce−

University，of

K

Iseki

Fisheries

and

the

eu−

Y．Izumi，1994．Hydrographic

and

its

importanceas

theNa−ofthemanuscript．

institutehas

infomed

in

June

in

food

ルでon言h〜y，26，228−235．（inKomaki，Y．，1967．On
crustaceans．

thePαo顔どcuponbyusas皿face

Hiuchi−nada，thecoastof

westem

Hokkaido，Japan．

ofof

swarmingof

E叩h側s∫αραo哲oα（Crustacea：Euphausiacea）in

theoJ．，79，269−276，

Hanamura，Y。，M．Kotori，and

ル勉r，Bsurfaceswarmsofthecoastof

Hokkaido，northem

west

SanrikucoastalS．Hamaoka，1989，Daytime

theeuphausiid

T勿sαπ06s5如n8r禰sJapan．

Mαr．β

offoム，

102，369−376．

Hirota，Y．and Y．Kohno，1992． Euphausiid fisheries inUwajima Bay，Ehime Prefecture（southwest Japan）。
Fズ5h，βKα砂oof

euphausiid

E叩hα麗8諭pαcε舜

theinci−

ωoffβμ1」．PJαn㍑on

theSoo・euphausii〔1fisher孟esandJapanese）

Y．Endo，1999．

management

andKrill

ecosystem

oJ，Oc8αno87。So配言hw63義V巳α尼孔／αραπ，8，89−95．

fisheries：development，

implications，Ag己燃

v加8

R召so尻君s．，12，105−120．

Nishikawa，J．，A．Tsuda，T，Ishigaki，andDistribution
warm

waterofeuphausiids

tonguewithinM．Terazaki，1995，

thespecialKuroshioreference

tofront
theandsurface

aggregationof伽ρhα房s如ραo旗α，／，P伽㍑oηRθs，，17，611−629．

0Brien，D．P．，D．A。Ritz，andandmatting

Saito，N．，1996．Note

watersJapan．

fish，Y，Hanamura，1995，Answarming

203−209．（inof

References

northeastem

swarming

surfaceon

R．J．Kirkwoo（1，1986，behaviour（Euphausiidae：Crustacea）．

off

demersalofStrandingsurfaceforJapanese）

dence

Nico1，S．andre（lSea．

Endo，Y．，1984，Daytime

con（1itionsSo∫．，21，433−448．

Kotori，M．，M．Tamura，andEnveironment

readingE．nαnαbeing￡edSea．

S惣θηK鱒oKen蜘一たα置oたoた麗，2，25−30・c・ntributingcatchesoftheeりphausiidE励α配3εαραc伽α

combi−Instituteidentification

extendInstituteof

ofthe

InlandIyo−mda，Seto

fisheriesbiologicalstudiesinJapan。κ碕oM・n助，26，Development，Tokai

confirming

phausii（ls．Thanks

tionalS．Sawamoto

Euphausiidsof（inJapanese）

Ack皿owledgements
thankandY，Hirota，1996．

part

海即n，42，80−84，
Kuroda，K．，1994． Review

We

from25swarmingJapanese）

Ko〔1ama，J．and

behaviourtheBuzen−kai3αon撚αs

Unfortunately，noaboutstudies

this（insynchro−available

thecollected

BrienααZ，（1986）noted

occur

off

occurrence

Kohno，Y．，H．Sakaguchi，andoften

euphausiids，

cmstaceans．0

behaviouL

theαnαnα。

Thysαnopo4α nlonαcαn言hα Ortmann， 1893 andN佛αオ03副 s4塀 o JsHansen，1911，aswellassomedeep−watertemperature

indicates

in

ル歪α孔B

E叩h側s如3〃nstrandedZsand

someotherBay，

crustaceans

middleHonshu．五〇，P，αv加81〉6ws，7，2−6、

andEuphausiacea，In：Chihara，M．

M．Murano（eds）An∫伽3枷

μαη々onn／αPαn。

1204−1226，（inTokaiofsurface

ραα算oαcaught
PowerPlant

in

648卿のoη2副n6

Univers重ty

Press，Tokyo，P・Japanese）

Suh，H．一L，J．一H、Lim，andstructure

Miho

Beach，Sumgasmall

Sawamoto，S．，1997，0rderon

IVyc珈hαn6s侃s枷」ごsoJ．，93，465−473，

theswarms

H，Y．Soh，1998，
of

thePopulation

euphausii（1E叩hαじbydrum

screensofeastcoastof／．κ07εαnOc6侃097，，33，35−40，

Korea．

Uljin

3♂αNuclear
So6．

Surface

swarm

and

strandingof伽1アhα配3如ηαnα

オキアミ類の一種E叩h側s∫αn侃αの海面浮上群と海岸への打ち上げ
花村幸生・神薗真人・片山幸恵
オキァミ類の一種E塑h側5如nαnρの海面浮上群と，それに続く海岸への打ち上げ現象を初めて瀬戸内海で確認した。オキアミ浮上群は9．0〜13．5mmの成熟個体で構成され、雄は十分に発達した精包を持ち，また雌の60％は交尾していたことから，、この群れは産卵群と考えられた。浮上群の性比はほぼ等しかった。オキァミ個体の殆どは空胃であり、海表面で索餌活動を行っていた形跡は認められなかった。環境データの時間変動とそのパターンから，瀬戸内海で確認されたオキアミ浮上群は豊後水道を起源とするものであると考えられた。

51