Buoyancy and Vertical Distribution of Mackerel Scomber japonicus Eggs in Korean Waters

(1)

Kor J Fish Aquat Sci 46(6),957-965,2013

한수지 46(6), 957-965, 2013

Original Article

957

서 론

고등어

(Scomber japonicus)

는멸치

,

오징어

,

갈치와함께국 내연근해어업생산량에서차지하는비율이가장높은종일뿐 아니라대중성이커서경제적가치또한높은어종이다

.

^국내

고등어의연간어획량은

1970

년대부터

1980

년대중반까지

10

만톤내외였으나이이후부터증가추세를보여

1996

^년에는^약

42

만톤까지어획되었다

.

하지만

1997

년부터

15

만톤수준으 로다시감소추세에있어

2000

^년부터는

TAC (Total Allowable

Catch)

^{대상어종으로}^지정되어^고등어의^{자원회복에}^대한^관심

이높아져있는상황이다

.

제주도와대마도주변해역은고등어의산란장이며

,

^산란기간 은

3-6

월

,

주산란기는

4-5

월이다

(Cha et al., 2002).

산란을마

친고등어는

7-11

^월^동안^서해와^동해에서^{섭이활동을}^하다가

12

^월부터^다음해

2

^월까지^월동을^위해^제주도를^포함한^남해로

회유한다

(Choi et al., 2003).

고등어는부화후

1

년이면성숙체 장

28.6 cm (NFRDI, 2010)

^에^이를^정도로^{초기성장률이}^매우

빠르므로환경변화에취약한초기생활사시기의생존율은다 음해고등어가입에직접적으로영향을줄수있다

. Kim et al.

(1999)

의연구에따르면

,

먹이생물인동물플랑크톤의현존량은

1-2

^년^이후의^고등어^가입과^양의^{상관관계가}^있는^것으로^나타 났다

.

^지금까지^국내^고등어^{초기생활사}^연구는^난발생과^자치 어의형태발달

(Kim et al., 2008; Park et al., 2008)

과난발생과 자어에미치는수온및염분의영향

(Hwang et al., 2008)

^등이 있다

.

따라서고등어생활사와생태학적특징을바탕으로한가 입량예측을통해효과적으로자원을관리하기위하여초기생 활사연구가절실히요구된다

.

알의수직분포에대한정보는알의산란장에서의분포

,

보육 장으로의운송

,

^{초기생존율}^등과^같은^생태학적^특징을^이해하 는데중요하게쓰인다

.

이러한수직분포를결정짓는생물학적 요인중의하나가알비중

(Sundby, 1991)

^이며

,

^여러^연구에서 알비중과관련된산란전략이나타난다

.

^예를^들면

,

^벵겔라^북 부용승지역에출현하는케이프민대구

(Merluccius capensis)

는산란수심

,

^알^비중

,

^중규모의^와류가^서로^{상호작용을}^하여

Article history;

Received 18 October 2013; Revised 27 November 2013; Accepted 28 November 2013

*Corresponding author: Tel: +82. 51. 720. 2287 Fax: +82. 51 .720. 2337 E-mail address: [email protected]

Kor J Fish Aquat Sci 46(6) 957-965, December 2013 http://dx.doi.org/10.5657/KFAS.2013.0957 pISSN:0374-8111, eISSN:2287-8815

ⓒ The Korean Society of Fishereis and Aquatic Science. All rights reserved

한국 연근해 고등어(Scomber japonicus) 알의 비중과 수직분포

정경미·강수경

^*

·차형기

¹

·최광호·Mari S. Myksvoll

²

국립수산과학원 자원관리과, ¹국립수산과학원 아열대수산연구센터, ²노르웨이 해양연구소

Buoyancy and Vertical Distribution of Mackerel Scomber japonicus Eggs in Korean Waters

Kyung-Mi Jung, Sukyung Kang

^*

, Hyung Kee Cha

¹

, Kwang Ho Choi and Mari S. Myksvoll

²

Fisheries Resources Management Division, National Fisheries Research & Development Institute, Busan 619-705, Korea

1

Subtrophic Fisheries Research Center, National Fisheries Research & Development Institute, Jeju 690-192, Korea

2

Oceanography, Institute of Marine Research, Bergen N-5817, Norway

This study simulated the egg vertical distribution of mackerel Scomber japonicus in Korean waters using general numerical mod- els. All eggs were spawned naturally by raising broodfishes (May-June 2013), and the egg specific gravity was measured by a density-gradient column. CTD surveys provided environmental data (e.g., temperature and salinity) in May near Jeju Island, Korea.

The egg specific gravity during the early stages ranged from 1.0203-1.0211. In general, the fertilized eggs showed a gradual decline in egg specific gravity until full development of the main organs, with a sudden increase just before hatching. Modeled egg vertical distributions were influenced more by wind speed than by egg buoyancy and vertical structure of the sea water. During calm and normal wind speeds, the eggs were distributed from the surface to 25-m depths. Under strong wind conditions (three times higher than the normal speed), the egg concentration on the surface decreased, and the egg distributional depth was deeper (~50 m).

Key words: Mackerel, Egg specific gravity, Vertical distribution, Wind speed, Scomber japonicus

(2)

민대구알이외해로손실되지않고연안으로수송되어먹이생 물이풍부한곳에서부화하도록 적응되어져있다

(Sundby et al., 2001).

^발트해^대구

(Gadus morhua)

알은인접해역의대서 양대구알보다크기가크고비중이낮으므로발트해표층의저 염분과저층의저산소를피하여대구알이중층의염분약층부 근에뜰수있도록하여알의생존율을높인다

(Nissling, 2004).

최근에는개체기반모델

(Individual-based model; IBM)

의발 달로초기생활사의운송

(transport)

^과^정체

(retention),

^가입기 작등

(Parada et al., 2003; Myksvoll et al., 2011, 2013; Ospina- Álvarez et al., 2012)

^을^연구하기^위해^알^비중을^포함한^생물학 적정보에대한관심이증대되어져있다

.

본연구에서는실험을통해얻은고등어알의비중을모델에 반영시켜물리적환경변화에따른알의수직적분포특성을이 해함으로써고등어의자원회복과관련된초기생활사

,

^가입기 작

,

^자원량^추정^등을^밝히는^연구에^{기여하고자}^한다

.

재료 및 방법

고등어 알 채집

본실험은국립수산과학원미래양식연구센터에서

2013

^년

5

월

(22

^일

-26

^일

)

^에

2

^회

(S1, S2)

^와

6

^월

(10

^일

-14

^일

)

^에

5

^회

(S3-S7)

에걸쳐수행되었다

(Table 1).

^자연^산란된^고등어^알을^얻기 위해약

300

개체의고등어를한개의실내수조로옮겨사육하 였다

.

^실험기간^동안^사육조^수온은

17.5-20.1℃,

^염분은

33.0- 34.8 psu

^범위로^{변동하였다}

.

^모든^개체는^{성숙체장인}

28.6 cm

이상이었다

.

^자정^무렵에^산란된^고등어^알은^새벽

6

^시경^수조 의배수관에연결된채집망을통해수거되었다

.

^알은^즉시^실험 실로옮겨져실체현미경

(Zeiss stemi DV4)

을이용하여발생단 계와난질의상태가파악되었다

.

^알의^{발생단계는}^수정^이후^경 과시간

(hours after fertilization, haf)

^으로^{표시되었고}

,

^난경은 gravity was also expressed as equivalent salinity units of egg neutral buoyancy. Age means egg stages shown as hours after fertilization (haf). Values are mean±one standard deviation

Month Sample Type n¹

Eggs at the column temperature of 20°C

Age Specific gravity Equivalent salinity Diameter

(haf) (g cm^-3) (psu) (mm)

May S1 Continuous 20 8 1.0211±0.0002 30.2±0.2 1.20±0.03

May S2 Time-point 32 9 1.0209±0.0003 30.1±0.4 1.17±0.02

June S3 Continuous 46 15 1.0207±0.0008 30.1±1.1 1.16±0.02

June S6 Time-point 43 9 1.0207±0.0007 29.8±1.0 1.17±0.05

June S7 Time-point 48 7 1.0207±0.0005 29.8±0.7 1.16±0.05

Mean 1.0207±0.0002 29.8±0.3 1.16±0.02

1n, number of eggs used in each measurement.

Table 2. Changes in egg specific gravity during development of S1, S4 and S5 continuous measurements. Initial, Min and Hatch indicate the mean egg specific gravity at the time of initial stage of experiments, minimum specific gravity, hatching, respectively

Sample Initial Min Hatch The amount of changes in egg specific gravity

Decrease (Initial-Min) Increase (Hatch-Min)

S1 1.0211 1.0202 1.0212 0.0009 0.0010

S4 1.0203 1.0188 1.0203 0.0015 0.0015

S5 1.0206 1.0191 1.0216 0.0014 0.0025

(3)

고등어 알의 비중과 수직분포

959

만능투영기

(Nikon profile projector V-10)

^를^이용하여

0.001 mm

까지측정되었다

.

고등어 알 비중측정

고등어 알의 비중실험은 연속측정법

(continuous measure- ments; S1, S3-S5)

과 순간측정법

(time-point measurements;

S2, S6-S7)

^의^두^가지^방법으로^{수행되었다}

.

^{연속측정법은}^수정

후약

8

^시간

(

^포배기

, 8 haf)

^부터^부화할^때까지^알의^비중변화 를

2

시간간격으로연속적으로관찰하는방법이며

,

순간측정법 은특정발생단계에서만비중을관찰하는방법이다

.

^초기^발생 단계는

7-9 haf

로일치시켰으나

, S3

의경우는

15 haf

로하였다

.

실험은비중측정기

(density-gradient column)

^를^{이용하였고}

,

모든실험기기의설치

,

^사용

,

^보정은

Coombs (1981)

^의^논문을 참고하였다

.

여과해수

(~34 psu)

와천일염을이용하여저염분

(~20 psu)

^과^고염분

(~48 psu)

^의^용액을^만든^후

,

^기기를^작동시

켜

80 cm

높이의유리관을조밀한염분층으로만들었다

.

유리

관의위쪽은가장염분이낮은약

20 psu

^였고^{아래쪽으로}^내려

가면서점차적으로높아져유리관바닥은약

43 psu

^였다

.

^유리 관의수온은냉각기를이용하여

20℃

로유지하였다

.

비중을알 고있는유리구슬

5

^개를^유리관에^투입하여

1

^시간^이후에^유리 구슬의위치를읽었다

.

처음유리구슬의비중이결정될때의수 온은

23℃

^로^유리관^수온인

20℃

^와^차이가^있어^{유리구슬의}^비 중은열팽창이론에근거하여보정되었다

.

^즉

(

^{유리구슬의}^밀도

)

＋(

수온차이

)×(

유리구슬의밀도

)×0.000028.

비중이서로다

른유리구슬은유리관안에서고유의비중위치에서정지하였 고유리관높이

(

독립변수

)

와유리구슬비중

(

종속변수

)

간의회 귀분석을통하여관계식이만들어졌다

:

^비중

=a×

^높이

+b.

^피펫

을이용하여약

20-50

^개의^알을^유리관에^투입한^후

1

^시간^이후

에알의위치를읽었다

.

^알의^비중은^위에서^구한^{회귀분석식에} 알의정지한높이를대입하여계산되었다

.

해양환경자료

국립수산과학원아열대수산연구센터는

2013

^년^봄에^제주도 인접해역

20

^개^정점에서^총

2

^회의

CTD

^조사를^{수행하였다}

. 1

차조사는

5

월

1

일부터

4

일까지

, 2

차조사는약한달뒤인

5

월

29

^일부터

6

^월

1

^일까지^동일한^정점에서^해수의^수온

,

^염분

,

^밀 도를관측하였다

(Fig. 1).

^바람의^세기는^기상청^{해양기상월보} 에기록된

2013

^년

4-6

^월^동안^지귀도

(

^위도

33° 13´,

^경도

126°

39´)

^의^일일^{평균풍속을}^{이용하였다}

(KMA, 2013).

알의 수직분포

고등어알의수직분포는대표정점

3

^곳

(

^{중국대륙연안수의}^영 향을받는정점

3,

^{대마난류수의}^영향을^받는^정점

15,

^제주연안 수의영향을받는정점

17)

에서

Sundby (1983)

의안정상태분 포이론를바탕으로개발된수치모델

(Ådlandsvik, 2000)

^을^이 용하여예측하였다

.

^모델에^이용된^정보는^본^실험을^통해서^얻

은알의비중과크기

, CTD

^조사에서^관측된^수온과^염분

,

^기상

청에서기록한지귀도의일일평균바람의세기였다

. 통계분석

연구결과의통계적유의성검정은

R version 2.10.0 (2010)

^을 이용하여

Student´s t-test

^와^{공분산분석}

[Analysis of covari- ance (ANCOVA)]

을실시하여 유의수준

5%

이내

(P<0.05)

로 분석하였다

.

y = 6.886x + 170.3 R² = 0.888

34

20

Jeju is.

19 20

2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17

St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

y = 6.886x + 170.3 R² = 0.888

34

20

Jeju is.

19 20

2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17

St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

Fig. 1. Map showing 20 CTD stations (filled dot) and Jigwido (filled star) around Jeju Island, Korea.

Fig. 2. Percent frequency of egg specific gravity at early developmental stages from May (S1-S2) and June (S3-S7) measurements.

(4)

정경미

ㆍ

강수경

ㆍ

차형기

ㆍ

최광호

ㆍ

Mari S. Myksvoll

960

결 과

고등어 알의 비중변화

초기발생단계에서알의특성을채집시기별로비교하였을때

(Table 1),

^월별^평균^비중은

5

^월에

1.0210, 6

^월에

1.0206

^이었 으며

, 5

월의평균비중이다소높았다

(t-test, P <0.001).

알의평 균직경은

5

^월에

1.19 mm, 6

^월에

1.15 mm

^로^{나타나면서}

5

^월에

0.04 mm

^큰^알이^채집된^것을^알^수^있었다

(t-test, P <0.001). 5

월과

6

^월의^전체^조사기간^동안^채집된^고등어^알의^평균^비중 이

1.0207,

^{표준편차가}

0.0002

^인^{정규분포곡선을}^따르는^것으 로나타났다

(Fig. 2).

발생과정동안일어나는알의비중변화를관찰하기위하여수 정후약

8

^시간

(

^포배기

)

^부터^부화

(

^수정^후

48-50

^시간

)

^까지

2

^시 간간격으로비중을연속측정하였다

.

^모든^{연속측정에서}^비중 은일정한패턴으로변하였다

(Fig. 3).

^수정^후

8

^시간부터^비중 은꾸준히감소하다가약

38

시간

(

배체의기관이대부분형성 됨

)

^이^되면^최소로^{낮아졌으며}

,

^부화^직전에^비중은^{갑작스럽게} 증가하였다

.

^비중의^변화량을^비교하면

, S1

^은

8

^시간부터

38

^시 간까지

0.0009

^의^감소량을^보였고

S4

^는

9

^시간부터

39

^시간까지

0.0015, S5

^는

8

^시간부터

38

^시간까지

0.0014

^로

S1

^보다^약

1.6

^배 감소량이많았다

.

최소값에서부화까지의비중증가량은

S1

이

0.0010, S4

^는

0.0015, S5

^는

0.0025

^였으며

,

^{부화단계에서는}^모 두첫포배기에서의비중값을회복하거나높아지는것을관찰 할수있었다

(Table 2).

제주도 주변해역의 물리적 환경특성

제주도인근물리환경의수평분포를살펴보면

, 5

^월^초

1

^차^조

사에서표층수

(1 m)

^의^수온은

14.4-18.4°C,

^염분은

33.7-34.8 psu,

^밀도

(sigma-t)

^는

24.6-25.5

^의^범위로^{분포하였다}

(Fig. 4).

5

^월^말에^실시한

2

^차^{조사에서는}^수온은^상승하여

16.9-20.0°C

의범위였고

,

^염분과^밀도는^모두^낮아져서^각각

32.6-33.7 psu, 23.3-24.4

였다

(Fig. 4). 1, 2

차조사에서동일하게남쪽과동쪽 해역은대마난류수의영향으로북쪽과서쪽해역에비해상대적 으로고온

,

^고염한^특성을^보였다

.

각정점에서대표수심

1 m, 25 m, 50 m

^를^선택해서^수온

,

^염 분

,

^밀도의^수직적^{분포양상을}^{알아보았다}

(Fig. 5).

^{대체적으로} 수온

,

염분

,

밀도의수심별차이는

5

월초보다

5

월말에크게나 타났다

.

^특히

5

^월^말^남쪽과^{동쪽해역에}^위치한^정점에서

1 m

^에

서

50 m

^범위^내^수온과^밀도의^변동폭이^컸다

.

고등어 알의 수직분포

5

^월^초^해수의^수온

,

^염분

,

^밀도는^수층간^변동폭이^크지^않았

지만

5

^월^말에는^표층의^수온이^{상승하면서}^약층이^{형성되었다}

(Fig. 6). 5

^월^말^{수온약층은}^정점

3

^과^정점

15

^에서^수심

15 m

Fig. 3. Ontogenetic changes in egg specific gravity from 8-9 haf

until hatching represented by the continuous measurements of S1 (□), S4 (△), and S5 (●). The continuous measurement of S3 is not shown because the initial stage of the experiment was 15 haf.

Bars refer to the 95% confidence interval for the mean egg specific gravity.

Fig. 4. Horizontal distributions of temperature (°C), salinity (psu) and density (sigma-t) at the 1 m depth in early May (May 1-4) and late May (May 29- June 1).

y = 6.886x + 170.3 R² = 0.888

34

20

Jeju is.

19 20

2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17

St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

Jeju is.

20 2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17

St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

(5)

고등어 알의 비중과 수직분포

961

y = 6.886x + 170.3 R² = 0.888

34

20

Jeju is.

19 20

2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17 St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

부근에서

,

^정점

17

^에서는^수심

35 m

^부근에서^{시작되었고}^정점

15

^의^{수온약층이}^수심

60 m

^까지^가장^깊게^{형성되었다}

.

^염분약 층과밀도약층은

5

^월^말^정점

15

^에서^수심

15-30 m

^사이에^두드 러지게나타난반면

,

^나머지^{정점에서는}^미약하게^{형성되었다}

.

제주도남부해역연안에위치하는지귀도에서

2013

년

4-6

월 동안관측된바람의세기는평균적으로

4

^월에

6.0 m/s, 5

^월에

4.4 m/s, 6

^월에

5.2 m/s

^로^{나타났으며}

, 5

^월은^다른^달에^비하여

3 m/s

^이하의^온화한^바람이^많이^불었다

(Fig. 7). CTD

^조사시 기와일치하는

5

^월의^바람^세기의^조건

(

^평균

4.4 m/s,

^최소

1.4 m/s,

최고

11.5 m/s)

아래에서고등어알이수직적으로어떻게 분포할수있는지살펴보았다

(Fig. 8).

^모든^가정에서^공통적으 로알의개체수는표층으로갈수록더욱많았고

,

^바람의^세기가 같은조건에서는정점간의수직분포패턴이매우유사하였다

(ANCOVA, F<0.01, P>0.99).

^또한

5

^월^말^정점

15

^에서^뚜렷이 나타났던약층은알분포에큰영향을미치지못하는것으로나 타났다

(Fig. 8c).

^바람^세기가^평균^이상인

11.5 m/s

^로^강하게^불 때모든정점에서알의표층개체수밀도가현저하게감소하였

고

(ANCOVA, F>21, P<0.001)

^최고^분포수심^또한^깊어져

50 m

부근까지알이분포할수있었다

.

고 찰

고등어알은분리부성란으로한개의유구를가지고있었으

며수정에서부화까지소요된시간은수온

20°C

^에서^약

48-50

시간이었다

.

난경은

1.14-1.20 mm

로지금까지보고된태평양 산고등어알의난경인

Kramer (1960)

^의

1.06-1.14 mm, Wata- nabe (1970)

^의

0.90-1.10 mm, Kim et al. (2008)

^의

0.98-1.02 mm, Park et al. (2008)

의

0.94-1.02 mm

보다다소컸으나

Ya- mada et al. (2007)

^의

0.90-1.30 mm

^의^범위에는^{포함되었다}

.

부화기간동안알의비중은일정한패턴으로변하였다

.

먼저 초기발생단계의알은시간이지남에따라비중이점차적으로 감소하였고배체의기관이대부분형성된단계부터부화까지 는갑작스럽게증가하는것을관찰할수있었다

.

이러한패턴 은앞서보고된대서양대구

(Gadus morhua)

알

(Anderson and

Fig. 5. Vertical distributions of temperature (°C), salinity (psu) and density (sigma-t) at 20 CTD stations in early May and late May. The distribution was represented by three water-depths of 1 m (thick solid line), 25 m (dotted line) and 50 m (thin solid line).

(6)

정경미

ㆍ

강수경

ㆍ

차형기

ㆍ

최광호

ㆍ

Mari S. Myksvoll

962

34

20

Jeju is.

19 20

2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3

)

Depth (m)

Station Hours after fertilization

June

34

33 Salinity (psu)

Early May (1m) Salinity (psu) Late May (1m)

34

126 21 19 17 15 13

1 m 25 m 50 m

Early May Late May

127 126 127

33 Density (sigma-t)

Early May (1m) Density (sigma-t) Late May (1m)

36 35 34 33 32 27

1 2 3 4 5 6 7 8 9 10

0 13

20 40 60 80 100

15 St.3

St.17 St.15

Early May

17 19 21

11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 26

25 24 23

13 15

Late May

17 19 21

Depth (m)

0 32

20 40 60 80 100

33 Early May

34 35 32 33 34 35

Late May

Depth (m)

0 20

20 40 60 80 100

14 12 10 8 6 4 2

0

25 W = 1.4 m/s Early May Late May

W = 4.4 m/s W = 11.5 m/s

50 1 6 11 16

April 21 26 1 6 11 16

Date May 21 26 31 5 10 June 15 20 25 30

0 21 22

Early May

24 23 25 26 20 21 22 23 24 25 26

Late May

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50

0

25 W = 1.4 m/s W = 4.4 m/s W = 11.5 m/s

50 0 60 120 180 0 60 120 180 0 60 120 180

deYoung, 1994; Jung et al., 2012),

^대서양^멸치

(Engraulis en- crasicolus)

알

(Ospina-Álvarez et al., 2012),

대서양넙치

(Hip- poglossus hippoglossus)

알

(Mangor-Jensen and Waiwood,

1995)

의비중실험결과와유사하였다

.

하지만이와다르게태

평양명태

(Theragra chalcogramma)

알의비중은크게증가하 다가부화직전에감소하였고

(Kendall and Kim, 1989),

^우리나 라 해역에분포하는 앨퉁이

(Maurolicus maurolicus)

알은초 기에서후기발생단계로갈수록비중이증가하였다

(Kim et al.,

2004).

현재까지발생단계별알의비중변화에대한원인은명

확히밝혀져있지않으나

,

^{공통적으로}^{부성란에서}^본^실험결과 와유사한패턴이관찰된것은침성란과구별되는생물학적특 징일것으로생각된다

.

알의부력

(Δρ)

^은^환경수

(ρ

_water

)

^와^알

(ρ

_egg

)

^의^비중^차이로^정

의된다

(

즉

, Δρ= ρ

_water

-ρ

_egg

)(Sundby, 1991).

만약알의비중이 주변환경수의비중보다크면알은자연히하강할것이고

,

^알 의비중이환경수보다낮으면상승할것이다

.

^알과^환경수의^비 중이동일한지점에서는정지하는중성부력을나타낸다

.

고등 어의산란장으로잘알려져있는제주도주변해역

(Choi, 2003)

은

4-6

월에표층수의수온이약

13-21°C,

밀도는

1.023-1.026

이다

(KODC, 2013).

^본^조사에서^고등어^알의^평균^비중은^수

온

20°C

^에서

1.021

^이었기^때문에^알의^비중이^서식지^해수의

비중보다

2-5×10

^-3의 범위에서 낮을 것으로판단된다

.

따라

서고등어알은강한부력으로표층가까이떠오를수있게된 다

.

이와유사하게일본산정어리

(Sardinops melanostictus)

알 은

1-4×10

^-3

(Tanaka and Franks, 2008),

^대서양^대구

(Gadus morhua)

^알은

0-5×10

^-3

(Jung et al., 2012)

^의^범위에서^환경 수보다비중이낮았다

.

대서양고등어

(Scomber scombrus)

의 경우도알의비중이주변환경수보다낮거나비슷하여표층으 로갈수록많은개체수의알이분포하는것으로보고된바있다

(Coombs et al., 2001).

실제해양환경에서알의수직분포는생물학적

(

^알의^부력

,

^알 의크기

),

물리학적

(

해수의밀도

,

해수의점성도

,

난류등

)

요인 들의상호관계에의해결정된다

(Sundby, 1991).

^본^연구의^모 Fig. 6. Vertical profiles of (a) temperature (°C), (b) salinity (psu),

and (c) density (sigma-t) measured at station 3 (solid line), station 15 (dotted line), and station 17 (dashed line) in early May and late May. Arrows indicate mean egg specific gravity of early developmental stages from S1-S7 measurements.

Fig. 7. Daily mean wind speed (m/s) from April to June 2013 measured at the station of Jigwido. The horizontal dotted line indicates average wind speeds in each month.

Jeju is.

20 2 3

4 10

9 8

12 11 18

14 15

17 16

13 5

6 7 33

80 60 40 20

1.023 1.022 1.021 1.020 1.019

34

33 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 1.018

Temperature (˚C)

Early May (1m) Temperature (˚C) Late May (1m)

1.0188 1.0193 1.0198 1.0203 1.0208 1.0213 1.0218 1.0223 1.0228 0

126 127

May

Egg specific gravity

Mean egg specific gravity

Temperature ( ˚C) Salinity ( psu ) Density ( sigma-t ) Depth (m) Depth (m) Depth (m)

Station

(a) Temperature (˚C)

(b) Salinity (psu)

(c) Density (sigma-t)

(a) Station 3

(b) Station 17

(c) Station 15

Egg concentration (number m

^-3