The malacologicalsocletyof society of Japan 160 VENUS: 25 (3 4) 1967 PacificOcean (Text-fig. 1). The inlet is well sheltered and never gets rough even

The malacological society of Japan

NII-Electronic Library Service

The malacologicalsociety ofJapan

Mass

Production

of

Molluscs

by

Means

of

Rearing

the

Larvae

in

Tanksi

Takeo

IMAi

(Tohoku

Univ.,and Oyster Research Institute, _Sendai,

_Japan)

Sth

tt1

of)

St

7 ,T

tP;

fi

l･C

.ll

5

iiik

tqs

IEb

aZII

0) _Ji<1,:kfk

ti

_V=-) _LN-C

A>

JP

iit

ft

("l][xl

Text-figs. 1-14;

k

Tables 1-3)

'

Recently

the technic of rearing the

larvae

of marine molluscs

has

_developed

rapidly

in

various countries.

This

is

mainly

due

_{to the progress in the} culture of

algal food organisms suitable for rearing the

larvae.

At

Mohne

laboratery

of the

Oyster

Research

Institute near

Kesennuma

city,

Miyagi

_prefecture, we have tried to develop the method to

_produce

the

_juveniles

of various moLluscs

in

comniercial scale

and then to grow them to the full-grown marketable size under captive conditions.

The

result of our experiments so far obtained will

be

_presented

in

thiS _paper.

Text-fig. 1. Aerial view of fleating culture

equipment in Mohne Inlet.

Species

of molluscs so

far

handled

at the laboratory are a scallop, Patinopecten

yessoensis, native species

in

Hokkaido and vicinitie$,

European

and

American

oysters,

Ostrea

edulis and

O.

Iurida

which had

been

introduced

from

Marennes,

France and

State

of

Washington,

U.S.A., several _years ago, and

finally

an abalene, flaliotisdiscus

hannai, native species ef the northern

Japan.

The

characteristic of our method

is

that the

larvae,

_juveniles

and adults are

cultured continuously and thoroughly under the

fioat

in

the sea.

The

floating

culture

equipment

is

set in Mohne

Inlet

con.nected with Karakuwa Bay which is_{open to the}

. .m---...

'

-.-...-ttt

o

This _paper was presented to Divisional Meeting 2,Fisheriesscience, of sectionvll,"Fis-rJEriegl

Marine and Freshwater Science" at the EIeventh Pacific Science Congress, Tokye,

_Japan,

1966.

160 VENUS: 25

(3･4)

1967

Pacific

Ocean

_(Text-fig.

1). The inlet iswell sheltered and never _gets rough even

in

a storm. The inlet water

is

usually very clean and

free

from

any type of _pollution.

The rafts of steel _pipe

(10m

long

and 8rn wide) are supported

by

special concrete

fioats

_(Text-fig.

2).

To

each raft,

15

tanks made of _polyethylene sheet

(2m

long,

tt t r-.whnt'"- scpt.tm.,,, ,

-ten..M{pt;..:t,. . 1 ' t t ..t,/..,,l././/,f,,t,..,,.

ll,-.,

/ttt tt _{ttt tt tt}ttt _t t tttt t t t t.:t.ttt._･'-,･･1･,,/,3.･,/'i,,ti',it;,i-･.･,/', .tt_･. '',:t"/t.:..',,}",;iOi,i,/･,1,;.'l,i･.,"".'

X'ilig#nysu.

ewas･".,---l

s"'',/'. .,...t., ,,/,,t,,,t,,,/t:tt/,t,,, ,t,,..t/t,. //r,gt/,/i,.,., 'it''t''t/L･{,,-. t/t ' t/ttt-t.,,.,,,

-Text-fig. 2. Culture rafts,

25

20 15?

::

ID.:=::5 Spawning in tsnk

IAN. FEB,

MAR.

APR. MAY IUN. IUL AUC, SEP. OCT. NeY. Text-fig.3. Seasonal variation of sea-water temperature in Mehne Inlet

and _period of tank breeding of various mol]uscs.

The malacological society of Japan

NII-Electronic Library Service

The malacologicalsociety of Japan

IMAi: Mass Production ef Molluscs by Rearing Larvae 161

lm wide and O.8m

deep

with a capacity of

1

ton) are

fixed

with a thin _plywood

cover on the top.

In

all, there are 180 _{tanks on}

12

rafts.

The

sea water

is

sand

filtered

and when

it

is

supplied to the tank it is filtered again by cartridge

filter

which will remove _particle$ to a size of 41t.

Compressed

air

is

also supplied _{to each}

tank

for

aeration.

Annual

variation of the sea-temperature and the _period of larval culture

is

shown

in

Text-fig.

3.

The

scallop spawn naturally at 80C

in

early spring. As the

tempera-ture above

120C

is

desirable

for

tank

breeding,

_the rnatured

individuals

are

kept

in

chilled sea water _{of 5eC} until the temperature of inlet sea water reaches 120C

in

May.

Spawning

can

be

induced

by

exposing the matured scallop to temperature fluctuation

between

9

and 15eC.

The

oysters _{spawn naturally} at around 150C

in

late

May

in the

inlet.

Their

spawning and

larval

swarming can

be

delayed

until the

later

_part of

July

_when

sea-temp. exceeds 180C, a favorable _ternp.

for

_tank

breeding,

_{by holding the} oyster

in

deep

water of

low

temp. or

in

cbilled sea-water of 100C.

The

abalone spawns _naturally when the sea-temp.

falls

to 20C'C inlate

September

or

in

early

October.

It isdesirable to start the culture as early as _possible in _order

to obtain larger

juveniles

before

cold weather begins, so the spawning

is

induced

in

early

September

by

exposing the matured abalone to temperature fluctuation

between

18 and 240C.

Controlling

and

induction

of spawning

by

temperature

in

varieus

mol-luscs are summarized

in

Table

1.

. . Table

l..

Control an9.

l'nduction

of spawning by ternperature fiuctuation.

Kind of mo]iuscs

:

.IEf.M,:fr,a,t."ece.,O.f,

i

...T,e,M.,?,e.'.atg,'.e.f.O:... '{lgili{.e,ra.t.Y.fie, fi,B:t.".a,FAO,"

SoCya.ltl.O,P 'I 1:.ecC ' lo5relC2.c

1

9-15eC 1

Abalone

1

2oeC 18-24e C ' tt t ttttt tttt t '

Temperature

fluctuation

required for

inducing

spawning

in

various molluscs can

be

obtained

by

a simple

device,

namely

by

running the water through a

long

poly-ethylene

tube

exposed to air.

Under

the sun the water

is

_warmed

_{up, while at night}

it

is

cooled

down.

As

food

organisms for rearing

bivalve

larvae,

we use a mixture of _pure cultures

of

Mo･nochio,sis

lutherii,

a colored

flagellate,

kindly sent from

Haskins

Lab.

N.Y.

and

Chaetoceros

calcitrans, _a

diatom

received

from

Tohoku

Reg.

Fish.

Lab.

'

In

the culture of abalone,

larvae

do

not require

food

in their swimming stage, therefore we start

feeding

as soon as they metamorphose

into

the crawling _$tage.

For

feeding

_young

juveniles

of abalone,

Platymonas

sp. a colered

fiagellate,

also sent

from

Haskins

Lab.

and

Navicula

sp., a

diatom

isolated

in

our

Iab.

are

found

to

be

satisfactory.

And

as the

_juveniles

_grow

larger,

we

feed

them _gradually with

larger

algae such as

Ulva

sp. and

Laminaria

sp.

(Table

2).

162 VENUS; 25

_(3･-4)1967

Table2, Kind of foodorganism forlarval andjuvenile culture.

Kind efmolluscs ForlarvaeFoodorganlsmFor

juveniles

Scallop Oyster Abalone

{

{

ua)nochrysis Chaetoceros Monochrysis Chaetoceros lutherii catcitrans lutherii caJcitrans:11!I Natural _plankton Natural plankton O,3-1,Omm. Platymonas sp, Navicula sp. 1.0-5 mrn. Navicuta sp. 5mm. & over Navicula.sp. Ulva sp. Laminaria sp.

The malacological society of Japan

NII-Electronic Library Service

The malacologicalsociety of Japan

IMAi: Mass Production of Molluscs by Rearing Larvae 163

Culture

of

food

organisms

is

carried

in

the culture room

kept

at a constant

tem-perature

of 200C. The culture solution

is

MiQuEL's

sea water to which vitamin Bi2 and

P6--Metal

are added. The _{culture solution}

is

_sterilized

by

_autoclaving. For large

sca!e of culture, the solution

is

_prepared

by

a centrifuge of

high

speed

(10,OOO-14,OOO

revolutions _per min,) and

by

exposing to u!traviolet

light

in

order to remove as many

microbes as _possible

(Text-fig.

4).

The

outdoor culture

is

also made

in

the

polyethy-lene

container of

20

liter

capacity

held

on the surface of the sea under sun

light

(Fig.

5).

In

case of culturing

Navicula

sp.

for

abalone

juveniles,

the culture

is

also

made

in

_polyethylene

tank which

is

used

for

rearing

larvae,

with enrichment of

MiQuEL's solution.

Text-fig. 5. Culture of food orgamsms in the sea,

Culture

tank

is

fi11ed

up with

filtered

sea water.

Larvae

hatched

out of

fertilized

eggs are divided intotanks at the rate of 2,OOO-3,OOO

larvae!l,

that

is

200,OOO-300,OOO

larvae

per tank.

The

larvae

are

fed

with approporiate food organisms. The

density

of

food

organism

in

tank

is

from

2,OOO to 15,OOO org.lml according to the _growth of

larvae.

When

the

larvae

reach

full

_grown stage, the collectors are _put in the tank to

catch the

juveniles.

Collectors

for

scallep

juveniles

are made of

_palm

fibers

fixed

on

wire-frame

(Text-fig.

6)

and those

for

oyster seed are string of scallop shells

(Text-fig.7). In case of abalone, _{we use} rough

_polyethylene

_plates

_with

Nam'cula

_grown

164 VENUS: 25

(3･4)

1967

Text-fig.6. Col]ectorforscal]op

juvenile.

Text-fig.7. Collectorfor oyster spat,

Text-fig.8. Abalone

juveniles

on collector.

Young

juveniles

of scallop and abalone on collectors are

kept

in

tanks with

run-ning water until they grow

big

enough to

be

transferecl

in

net to natural water. In

case of oysters,

they

can

be

returned to the sea as soon as they are set.

In

case of scallop,

juveniles

of over lcm.

in

shell

length

are _put

in

the

wire-framed

net

(Text-fig.

9)

and

hung

in

the sea.

When

they _grow to 5cm. and over,

they can

be

connected to rope

by

nylon

fiber

strings through

holes

made

in

the ear

part

of shell

(Text-fig.

10).

The

method

is

prevalent

arnong _growers. Or they can

be

grown also

in

the wire-framed net

(Text-fig.

11).

We

can _grow them to a

marke-table size of 12cm. in shell

length

in

2 _years.

In

case of oyster, collectors are _twisted into tarred straw and

hung

under the

The malacological society of Japan

NII-Electronic Library Service

The malacologicalsocletyof Japan

IbtAI:Mass Production Text･fig. 9. Scallop in wire-framed

juveniles

net, Text-fig. net 11. Scallop

(1

year old>.culture in of wire-framed Molluscs by

'ti/igta:////,///1.1,iii''/',:'･ ''lt/il.:t.'.,/',t,l'', Rearing .- t t..tt

i''

i'""'

Larvae 165 ttt t tt t ttt t. tt//t .t//t ./: t /ttt ttt t tt t,,ttt t/. .. ,.t . tt. . .t tt tt m t.t .ttt._tt .tttt t t /,,/t,t./,

Text-fig. 10. Hanging culture

of scallop by rope,

Text-fig.12.

O. edulisHangingby ropeculture

(1

_yearof

oyster, old>,

166 VENUS: 25

(3.4)

1967

in

two

years with a shell

length

over 10cm.

in

case of

O.

edulis.

They

can

be

_grown

also in wire-framed net

(Text-fig.

13).

When

abalone on collectors reach

5mm.

in

shell

length

they are _put

in

net

bags

or

_plastic

containers and

hung

in the sea

for

further

culture

(Text-fig,

14). Abalone

grows

to

3cm.

in

shell

length

in

15 months after their spawning.

And

they will

be

ready to

be

released

in

the natural

habitat.

If

we continue culture

in

net

bag

or in

container, they

grow

to a marketable size of over 10cm.

in

shell

length

in 4 years

after spawning.

Text-fig.13. Hanging culture Text-fig.14. Abalone culture inplastic

of oyster in net. contalner.

The

results of our cultivation of

larvae

and

juveniles

are summarized in

Table

3.

Though

the number of

juveniles

obtained

is

rather

low

as compared to that of

larvae,

the

_percentage

could

be

increased

considerably

by

technical imprevement

in

future. Table 3. Results of rearing larvaeand

juveniles.

Average number of Average number of

Kind of mollusCS _{larvaein tank}

juveniles

obtained

L

3oo,ooo

(,g

::I

;21

:g:

1':ag

Scallep

Oyster 300,OOO 5mrn. 12,OOO

_(4%)

2oo,ooo

{,g

::I

ig;

:::

(,

2Zl

The malacological society of Japan

NII-Electronic Library Service

The 　malaoologioal sooiety of _Japan

IMA1： Mass　Production　of　Molluscs 　by　Rearing 　Larvae 167

　　

With

　the　present　

facilities

　at　

hand

，　we 　will 　

be

　able 　

to

　produce 　over 　 one 　million

of　scallop 　Qf　3　c皿

in

　shell 　

length

，

2millions

　of　oyster 　seeds 　and 　over 　a　million 　of　abalone

of　3　_cm 　in　shell 　

length

．　

Though

　our 　operation 　

is

　still　

in

　the　exploratory 　stage ，　we 　are

looking

　

forwards

　to　

being

　able 　tQ　make 　 a 　significant 　contribution 　to　the　cultural 　

in

−

dustry

　

in

　

fisheries

　

by

　

improving

　the　technics　

in

　

hatchery

　operation 　and 　also　

in

　the through −culture 　from 　larvae　to　marketable 　size _，　

in

　various 　marine 　molluscs ．

要 約

　近 年 海 産 貝 類 幼 生の 飼 育 技 術が急速に _{進 歩}し た が ， これ は主 と して，幼 生の 適性餌料 生物の分離 ・培 養が 進歩 し た お蔭で ある とい っ て過 言で はある まい 。 我 々 も長い 間，純生 物 学 的 目的 で貝 類 幼 生 飼 育 を 行 っ て き

た が， 6年 前か ら財 団 法 人か き研究 所舞 根実験 室で， 産 業 的 規 模で か き を 始め 各 種 貝 類の タ ソ タ採 苗 と そ の

養 殖を試みてきた。現在 扱っ てい る 主 な 隙類は， ホ タテ ガ イ PatinoPecten 　yessoensis， ヨ ーロ ッ パ ヒ ラ ガ キ

Ostrea　eduiis と亠 ゾ ァ ワ ビ Haliotis　discus　hannai である。 我 々 の ね らい は幼 生を海面 に設け た タソ ク で

飼 育す る一方，得 ら れた腫 苗 を 成 貝ま で継続し て養 成 す るこ とで ある。 　施 設 は気仙 沼湾の 舞 根 入 江に 設 け たが ，こ こ は静 穏で あり， 又 海 水は 極め て 清浄で ある。 タ ン クは容 量 約 1 トソ ，ポ リエ チ レ ソ製で鉄管を組立 て た筏 （10mX8m ）か ら下 げて海 中に _支える ように してある。 12台の 筏で タ ソ ク総 数は 180で ある。海 水は 先 づ 砂濾過 し， 更に カート リッ ヂ濾過 器を通 し て タ ソ ク に給 水 する。 産卵 母貝は低 温 処 埋で産 卵 期 を調 節し， 入 江の海 水 の飼 育 適 温 期に合せ て，温 度 刺 戟を 用 い て産卵 を誘 発 す る。

　幼 生 飼 育の餌 料は 二_枚貝 幼 生 で は Monochrysis　lutheri 及び ChaetocerOS 　calcitrans ，ア ワ ビ で は匍 匐 生

活に 入っ て か ら Platymonas　sp ．及 び Navicuia 　sp ．を テえ， 殻 長 5m 皿 に達 す る と Ulva 　sp．及 び

Laminaria 　sp ．の海 藻を与える。1 タ ン ク当 り幼 生 20− 30万を収 容 し，餌 料 生 物は飼 育 海 水 1cc 当 り 2，000− 15，000 の 密度に な る よ う投与 す る。 　幼 生が付着 変 態 期に達し た時期に付 着 器 を入れて採苗 する が， 付 着器に は ほたて 貝の 場 合に は枠に入 れた 棕 櫚 繊 維，カ キで はホ タ テ ガ イ貝 殻， 又ア ワ ビ で は凹 凸の あるポ リエ チ レ ソ 板で その 表 面 に 予 め Navicuta を植えつ け た もの を用い る。ほ たて 貝 稚 貝は付着 後タ ソ クの中で流水 式で暫く飼育，殻 長 1皿 m の時， 目の 細か い ネッ トに収容， 筏か ら海 中に垂下 養 殖， カ キの場 合に は付着 直 後海 中に移 して飼 育， ア ワ ビ稚 貝はタ ソ ク内で流 水 法で飼 育 5mm に達 し た時 付着器の ま ま ポ リエ _チ レ ソ 容器に 入 れ， 流 水 法 で Ulva を与 え乍 ら 飼育 する。 　 ホ タテガ イ稚貝はその成 長に 伴い ，綱 目の大 きい ネッ ト に 移すが，翌春 5cm に達 し た とこ ろ で， 殻の 耳 の 部 分に 小 孔 を あ けテ グス 糸を通 し， これをロ ープ に結 びつ けて垂 下 す れば，生後 2 ケ年で殻 長 12cm の成 貝が得 られ る。 杵 型の ネッ ト で も 同 様 養 殖が 9_{∫能である} 。 カ キ は付着器の ま ま ロ ープで 垂下 養 殖 し，生後 2年 で 成 貝が 得 ら れる。ア ワビ稚 貝は 約 1cm に 達 し た と こ ろ で，容 器 の ま ま ネッ トに収容し随時 Uiva ， Laminaria を与えつ つ _{垂 下 養殖 す}る_。 生後 3〜4年で 約 10cm の成 貝 が 得 ら れ る。現 在の施 設で，ホ タ テ ガ イ _（殻長 3cm ）100万 個，カ キ種 苗200 万 個，及びア ワ ビ_稚貝 （殻 長 3cm ）100 万 個 生 産の 見透 し がつ い た。 N工 工一Eleotronio _Library