kfas

305

Copyright © 2018 The Korean Society of Fisheries and Aquatic Science pISSN:0374-8111, eISSN:2287-8815

서 론

크릴류

(Euphausiids)

^{는동물플랑크톤의한 종류로고래}

,

^펭 귄

,

바다표범등과같은포유류

,

조류

,

어류의주요먹이생물로 생태학적으로중요한종이며

(Everson, 2000),

이와같은동물 플랑크톤의한종류인난바다곤쟁이류

(Euphausia pacifica)

는 북태평양과한국연근해에걸쳐널리서식하면서해양생태계 에서식물플랑크톤과같은일차생산자와상위포식자를연결

하는중요한역할을하는것으로알려져있다

(Mauchline and

Fisher, 1969; Mauchline, 1980; Kim et al, 2010).

동해안포항구룡포해역에서는

40-50

년전부터전통적으로 어업인들이이러한핵심적인역할을하는난바다곤쟁이가군집 을이루는시기인봄철인

4

^월에서

6

^{월에뜰채로조업을하여왔}

다

.

그러나

, 2006

년도까지자유롭게조업하다가

2007

년에불법 어구로판정되어해양경찰에의해단속되면서난바다곤쟁이자 원에대한이용가능성및일정시기에대량발생하는특정자 원에대한한시적이고합법적인조업승인에대한검토가필요

하였다

(NIFS, 2010).

난바다곤쟁이류와관련된국내연구결과

로는황해에서환경요인과관련된종조성과공간분포

(Yoon et

al., 2000; Yoon et al., 2006),

^{울진원전취수구의대량유입되} 는무리의개체군구조

(Suh et al., 1998),

생물및생태학적연 구

(Suh, 1988; Lee et al., 1994; Yoon and Kim, 2000)

등주로 종조성및동정등으로난바다곤쟁이의자원량분포및밀도추 정에관한연구가미비한실정이다

.

난바다곤쟁이와같은해양생물의자원을관리하기위해시

·

공간분포및밀도를파악하는것이매우중요한데

,

음향기술은

2주파수차 분석 기술을 이용한 난바다곤쟁이류(Euphausia sp.)의 현존량 추정

김병관·한인우 ¹ *·오우석 ¹ ·최영민 ² ·윤석현 ³ ·이형빈 ⁴ ·이경훈 ⁵

국립수산과학원 수산공학과, ¹전남대학교 수산과학과, ²국립수산과학원 고래연구센터, ³국립수산과학원 기후변화연구과,

4서해수산연구소 자원환경과, ⁵전남대학교 해양기술학부

Biomass Estimate of Euphausiids Euphausia sp. Using the Two-frequency Difference Method

Pyungkwan Kim, Inwoo Han

¹

*, Wooseok Oh

¹

, Yong-Min Choi

²

, Seokhyun Yoon

³

, Hyungbeen Lee

⁴

and Kyounghoon Lee

⁵

Fisheries Engineering Division, National Institute of Fisheries Science, Busan 46083, Korea

1Division of Fisheries Science, Chonnam National University, Yeosu 59626, Korea

2Cetacean Research Institute, National Institute of Fisheries Science, Ulsan 44780, Korea

3Ocean Climate & Ecology Division, National Institute of Fisheries Science, Busan 46083, Korea

4West Sea Fisheries Research Institute, National Institute of Fisheries Science, Incheon 22383, Korea

5Department of Marine Technology, Chonnam National University, Yeosu 59626, Korea

This study was carried out to investigate euphausiid abundance in an acoustic survey from March 2010 to July 2010 to suggest reasonable usage and management of the euphausiid Euphausia pacifica in the coastal area of Guryongpo Pohang. The acoustic data were analyzed by the 2-frequency difference method and the distorted wave born ap- proximation acoustical theoretical model, which is used for organisms of weak target strength with small scatter, such as euphausiid scatter, among other marine organisms. The distribution and monthly density of euphausiids were estimated in the survey area. The results show that the volume back scattering strength frequency difference for eu- phausiid was 13.91-7.6 dB, and their monthly averag density was 28.2 g/m ² .

Key words: Biomass estimation, Distorted-wave born approximation, dB-difference method, Euphausiid

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

https://doi.org/10.5657/KFAS.2018.0305 Korean J Fish Aquat Sci 51(3) 305-312, June 2018

Received 30 April 2018; Revised 15 May 2018; Accepted 4 June 2018

*Corresponding author: Tel: +82. 61. 659. 7124 Fax: +82. 61. 659. 7129

E-mail address: [email protected]

김병관

ㆍ

한인우

ㆍ

오우석

ㆍ

최영민

ㆍ

윤석현

ㆍ

이형빈

ㆍ

이경훈

306

짧은시간동안전수층의넓은해역의정보를파악할수있어 많이이용되고있다

(Lawson et al., 2008; Cox et al., 2011; La et al., 2016).

현재음향기술을이용한다양한어종식별방법 이있는데

,

최근음향산란층에존재하는어군과동물플랑크톤

,

작은어류및치어등음향산란층에분포하는여러생물종을구 별하는방법은

2

주파수이상의다중주파수의주파수차에의 한방법을주로사용하고있다

(Miyashita et al., 1997; Kang et al., 2002; Lee et al., 2004).

본연구에서는난바다곤쟁이의밀도추정의정도를높이고종 을식별하기위해

38

^과

120 kHz

^의

2

^{주파수로구성되어있는과} 학어군탐지기를이용하여대상어종에대한서로다른음향산 란특성을이용한주파수차이를이용한방법과음향산란층내 의다양한생물의종식별에서음향산란이론모델을이용한분 석방법으로동해안포항구룡포해역주변에서식하는난바다 곤쟁이의분포추정과밀도를파악하여자원이용성을검토하 고제도화및자원의합리적이용및관리방안을위한기초연구 로서제시하고자한다

.

재료 및 방법

조사 해역 및 조사 기간

조사기간은

2010

년

3

월부터

7

월까지수심별로

50 m

미만 의연안지역

(St. 1, 4, 7

및

10),

수심

100-200 m

사이의중간지 역

(St. 2, 5, 8,

^및

11),

^수심

350 m

^{보다깊은외해지역}

(St. 3, 6, 9

및

12)

의

12

개정점을기준으로총

4

정선을따라정점간연 안측에서선속

7.0-10.0 knot

로수중음향조사를실시하였으 며

(Fig. 1),

조사해역의면적은

155.25 km

²이었다

. 12

개의정

점에서

RN80

네트

(

그물직경

Ø1 m net,

망목

333 μm)

를이용하 여저층까지수직채집과빔네트

(

망구

1 m×1 m net,

망목

500 μm)

^{를이용하여}

10

^{분간경사채집을병행하였다}

.

음향 시스템의 구성

음향조사시스템은다중주파수로구성되어있는과학어군탐 지기

(EK60, Simrad, Norway)

를국립수산과학원시험조사선

(

탐구

12

호

, 70 GT)

의현측에부착하였으며

, 38 kHz

와

120 kHz

의트랜스듀서의타입은각각

ES38B-12, ES120-7G

^로설정하 였다

. 38

과

120 kHz

의펄스폭은

512 ms, ping

간격은

1

초

,

탐

지범위는수심

0-300 m

로설정하여음향자료를수집하였다

.

현장에서획득된음향자료는음향분석소프트웨어

(Echoview V 4.7, Echoview Software Pty Ltd, Australia)

를이용하여후 처리분석을실시하였다

.

주파수 차이를 이용한 에코 추출

난바다곤쟁이의 에코를추출하기 위해서는

38 kHz

와

120

kHz

에대한

2

주파수의특성과차이를파악해야한다

.

주파수

차이를이용하는방법은다중주파수에서평균체적후방산란 강도

(mean volume backscattering strength, ΔMVBS)

^의차이 를나타낸것으로본논문에사용된방법은다른해양생물과혼 합된난바다곤쟁이의종식별을위해주로사용하는방법으로 서흐름도는

Fig. 2

와같다

.

해수면과해저면에의해발생하는잡음을제거하기위해서먼 저주파수

38 kHz

^의

raw data

^에

line bitmap

^{연산자를적용하} Fig. 1. Acoustic survey line and sampling sites for euphausiids.

St.10 St.11 St.12

St.3 St.2

St.1

St.4 St.5 St.6

St.9 St.8

Latitude (°N) St.7

Longitude (°E) Pohang

Yeongil Bay Guryongpo 36.2

36.4 36.3

36.5 129.4 129.5 129.6 129.7 129.8

38 kHz raw data

Line bitmap Region bitmap

Mask (38 kHz) Resample by time

38 kHz

SV difference 120-38 kHz (dB)

120 kHz raw data

Resample by time 120 kHz

Data range bitmap Mask (Euphausiid)

Mask (120 kHz) And

NASC

w = aL

^b

& TS

Length frequency (f) Conversion factor (CF)

Survey area

Biomass

0 5 10 15 20 25

-120 -110 -100 -90 -80 -70

0 5 10 15 20 25 30

Averaged TS (dB)

Body Length (mm)

120kHz 38kHz 120kHz-38kHz

dB difference (dB)

Tilt angle; 30.4°±19.9°

Fig. 2. Flow chart of acoustic data processing using dB difference method at 38 kHz and 120 kHz.

St.10 St.11 St.12

St.3 St.2

St.1

St.4 St.5 St.6

St.9 St.8

Latitude (°N) St.7

Longitude (°E) Pohang

Yeongil Bay Guryongpo 36.2

36.4 36.3

36.5

129.7 129.6

129.5

129.4 129.8

38 kHz raw data

Line bitmap Region bitmap

Mask (38 kHz) Resample by time

38 kHz

SV difference 120-38 kHz (dB)

120 kHz raw data

Resample by time 120 kHz

Data range bitmap Mask (Euphausiid)

Mask (120 kHz) And

NASC

w = aL

^b

& TS

Length frequency (f) Conversion factor (CF)

Survey area

Biomass

0 5 10 15 20 25

-120 -110 -100 -90 -80 -70

0 5 10 15 20 25 30

Averaged TS (dB)

Body Length (mm)

120kHz 38kHz 120kHz-38kHz

dB difference (dB)

Tilt angle; 30.4°±19.9°

여해수면경계선의위구간과아래구간의데이터는모두제 거하고

,

경계면이아닌수중에존재하는노이즈를제거하기위

해

region bitmap

연산자를이용하여수중에존재하는노이즈

를제거하였다

.

이후

And

연산자를사용하여체적산란강도데 이터에

line bitmap

과

region bitmap

필터를동시에적용하여 각각에코그램

mask

^{를만들었다}

.

^{해수면및해저면}

,

^그밖의잡 음을제거한후적분구간을설정하여주파수별행렬로구성하 면새로운에코그램이형성된다

.

이때

,

시간별

resampled

기능 을이용하여에코그램을한눈으로볼수있게압축하였다

.

난바 다곤쟁이의주파수차이가명확하게되면그값에대한범위를 설정하여

data range bitmap

^{을만들어이범위에설정된에코와} 주파수

120 kHz

의셀의크기와매치되는에코그램

mask

를만

들고

,

잡음이제거된

120 kHz

의에코그램과일치되는에코그

램을대상생물의에코그램으로간주하였으며

,

난바다곤쟁이 의밀도를추정하기위한에코그램의적분층의크기는

10 ping

× 3 m

^{로설정하였다}

. 모델을 이용한 밀도 추정

음향을이용하여음향산란층에존재하는난바다곤쟁이의밀 도를추정하기위해서는채집된표본에대한후방산란강도혹 은반사강도

(target strength, TS)

를결정해야한다

.

그러나난 바다곤쟁이류또는동물플랑크톤

,

^{크릴류와같은작은생물을} 포함한부레가형성되지않는치어들은크기가작을뿐만아 니라

,

후방산란특성이매우미약하기때문에현장에서는후방 산란강도를측정한다는것이매우어렵다

.

따라서

,

형태를추 정하기힘든생물의경우음향산란이론모델을이용하여후방 산란강도를 추정하는데

,

^{최근에는 음향산란이론모델인}

dis- torted wave born approximation (DWBA)

와

stochastic dis- torted wave born approximation (SDWBA)

으로추정하고있 다

(Demer and Conti., 2005; Conti and Demer., 2006).

본논문

에서는

DWBA

음향산란이론모델을적용하여난바다곤쟁이

의디지타이저처리한윤곽데이터로부터

3

^{차원물체의음향} 산란특성을변형실린더형태로가정하여이론

TS

값을추정하 였다

. DWBA

모델식은다음식

(1)

에서

(3)

으로표현할수있다

(Stanton et al., 1998; McGehee et al., 1998; Lee et al., 2004).

f

_bs

= r

_pos

k 4k

₁²

a (γ

_{2 k}

-γ

_p

)e ^2ik

²

^r

^pos

J

₁

(2k cos β

₂

acos β

_{tilt tilt}

) |dr

_pos

| ···(1)

σ

_bs

=|f

_bs

|

²

···(2)

TS=10logσ

_bs

··· (3)

여기서

, r

_pos^{는산란체의중심으로부터의위치이고}

, k

^는파수로 서

k=2π/λ

^{로나타낼수있으며}

, λ

는파장이다

. α

는절단원통의 반경

(mm), β

_tilt^{은입사하는음파와원통축사이의각도이며}

, J

₁

은제

1

^{종베셀함수이다}

. r

_k,

r

_ρ ^{는대상생물의음속비}

(h),

^밀도비

(g)

를이용하여다음식

(4)

와

(5)

로나타낼수있다

.

r

_k

= 1 -1 ··· (4) gh

²

r

_p

= 1- 1 ··· (5) g

난바다곤쟁이 밀도 평가

본논문에서는난바다곤쟁이의밀도를추정하기위해과학어 군탐지기로부터

1 n.mile

간격으로추출한체적산란강도값을

NASC (nautical area scattering coefficient)

로변환한값을사 용하였다

.

체적산란강도값을

NASC

로변환하는관계식은식

(6)

에나타내었다

.

NASC= 4π1852

²

r r

₂₁

Sυdr ··· (6)

NASC

값은체적내수중생물의선형적인합으로식

(7)

와같

이어군의밀도를해수체적내평균

NASC

값을난바다곤쟁이

의

TS

를나눔으로계산할수있다

(Hewitt and Demer, 1993).

NASC=ρ·TS ··· (7)

난바다곤쟁이의체장

(L, mm)

에따른

TS

값과후방산란단면 적은각각식

(8), (9)

에나타내었으며

,

난바다곤쟁이

TS

및후방 산란단면적

(σ = 4π10

^(TS/10)

)

는다음과같이표현된다

.

TS=22.2 log(L)+148.6 ···(8) σ=4π10

(-148.6 + 22.2log/10)

···(9)

모델에적용되는난바다곤쟁이의밀도비와음속비는 각각

‘Density bottle’

법과

‘Time of flight’

법

(Greenlaw, 1977)

을이용하여측정한데이터와동일한시점에서채집한밀도비

(1.044)

와음속비

(1.073)

를적용하였다

(Mikami et al., 2000).

또한

,

이론모델에의해추정되는난바다곤쟁이의

TS

피치각특 성에의한평균

TS

^{를구하기위해}

,

^식

(8)

^{에의해산출된}

σ

_bs^의 유영자세각특성을곱하여식

(10)

와같이평균화하였다

.

<σ

_bs

>= ⁺⁹⁰ _-90 σ

_bs

(θ) f(θ) dθ ··· (10)

σ

_bs

(θ)

는 각 유영자세각

θ

에서의후방산란단면적

, f(θ)

^{는 각} 유영자세각의출현빈도를나타낸다

.

본실험에서유영자세각

김병관

ㆍ

한인우

ㆍ

오우석

ㆍ

최영민

ㆍ

윤석현

ㆍ

이형빈

ㆍ

이경훈

308

분포는유영자세각정규분포

30.4±19.9°

^값

(Miyashita et al.,

1996)

을적용하였다

.

난바다곤쟁이의평균체장에대한습중

량

(WW, Wet weight)

을식

(11)

로계산하였다

(Lee at al., 2004).

WW(g) = 9.0 · (krill length, L)

^2.9

· 10

^-6

(11)

평균후방산란단면적은

DWBA

모델에의해각주파수에대 한값을넣어계산하고

,

^{대상생물의후방산란단면적및체장}

-

체중함수식은음향조사에서채집된자료를활용하였다

.

난바 다곤쟁이의밀도

(ρ)

는식

(12)

과같이

1 n.mile

간격의체적내의 평균면적산란계수를하나의어군의후방산란단면적으로나눈 뒤중량를곱하여구하였다

.

ρ=(NASC/σ)·WW= 4π10 α L

^(TS/10)b

·NASC (12)

여기서

,

식

(12)

의우변의

NASC

를제외한나머지부분이음향 자료로밀도를계산하는변환계수

(conversion factor, CF)

^로어 류의체장체중함수식과

TS

함수식을고려한것이다

.

추출된난 바다곤쟁이의밀도를표층으로부터수심

300 m

까지

1 n.mile

의

EDSU

간격으로적분하고

,

추출된면적산란계수값을이용

하여각월별일몰과일출로인한난바다곤쟁이의연직이동특 성을분석하였고

,

^시

·

^{공간분포로연직이동에따른난바다곤쟁} 이의평균분포수심을시간대별로분석하였다

.

결 과

난바다곤쟁이의 채집 분석

2010

년

3

월부터

8

월까지채집된난바다곤쟁이의개체수는월 별단위면적당약

126-9,029

개체

/m

²으로월별차이가많았다

.

채집된데이터를바탕으로난바다곤쟁이의평균체장을

Table.

1

과같이나타내었다

.

월별채집된난바다곤쟁이의평균체장 크기는

11.4-17.8 mm

^{로나타났으며}

, 5

^{월평균체장은}

17.86 mm

로가장큰체장이측정되었으며

, 7

월에는

11.40 mm

으로 다른월에비해상대적으로작은체장이측정되었다

.

이론모델에 의한 TS추정

음향산란모델은특정플랑크톤및후방산란강도측정이어려

운생물에적용하여후방산란강도를추정하는방법이며

,

최근 남극크릴의이론모델로검증한

DWBA

모델은적용하여난바 다곤쟁이를디지타이징처리한윤곽데이터로부터

3

차원의물 체의음향산란강도를변형된실린더형태로가정하여서체적 적분식으로계산하였다

.

^{모델에적용되는 난바다곤쟁이의체} 내밀도비와음속비

(Mikami et al., 2000),

유영자세각정규분 포값

(Miyashita et al., 1996)

을적용하여각주파수별체장

(L)

^에 대한평균

TS

함수식을구하였다

(Fig. 4).

채집된데이터를기준 으로난바다곤쟁이의평균체장은

16 mm

로주파수차이값은

13.9 dB≤ TS

_120-38kHz

≤ 17.6 dB

^{로나타났으며}

,

^{난바다곤쟁이의}

TS

는체장이커짐에따라증가하고

,

저주파인

38 kHz

보다고주

파인

120 kHz

에서높게나타났다

.

조사해역의난바다곤쟁이의

체장분포에대한주파수차로설정하여

2010

년

3

월부터

7

월까 Table. 1 The mean TL (Total length) of euphausiids Euphausia pa-

cifica in each month

Month Mean TL (mm)

March 15.99

April 16.47

May 17.86

June 17.78

July 11.40

Fig. 3. The flow chart for estimation of euphausiid’s biomass.

St.10 St.11 St.12

St.3 St.2

St.1

St.4 St.5 St.6

St.9 St.8

Latitude (°N) St.7

Longitude (°E) Pohang

Yeongil Bay Guryongpo 36.2

36.4 36.3

36.5 129.4 129.5 129.6 129.7 129.8

38 kHz raw data

Line bitmap Region bitmap

Mask (38 kHz) Resample by time

38 kHz

SV difference 120-38 kHz (dB)

120 kHz raw data

Resample by time 120 kHz

Data range bitmap Mask (Euphausiid)

Mask (120 kHz) And

NASC

w = aL

^b

& TS

Length frequency (f) Conversion factor (CF)

Survey area

Biomass

0 5 10 15 20 25

-120 -110 -100 -90 -80 -70

0 5 10 15 20 25 30

Averaged TS (dB)

Body Length (mm)

120kHz 38kHz 120kHz-38kHz

dB difference (dB)

Tilt angle; 30.4°±19.9°

Fig. 4. The averaged target strength and dB difference of euphau- siid Euphausia pacifica according to its body length using DWBA model. TS, target strength.

St.10 St.11 St.12

St.3 St.2

St.1

St.4 St.5 St.6

St.9 St.8

Latitude (°N) St.7

Longitude (°E) Pohang

Yeongil Bay Guryongpo 36.2

36.4 36.3

36.5

129.7 129.6

129.5

129.4 129.8

38 kHz raw data

Line bitmap Region bitmap

Mask (38 kHz) Resample by time

38 kHz

SV difference 120-38 kHz (dB)

120 kHz raw data

Resample by time 120 kHz

Data range bitmap Mask (Euphausiid)

Mask (120 kHz) And

NASC

w = aL

^b

& TS

Length frequency (f) Conversion factor (CF)

Survey area

Biomass

0 5 10 15 20 25

-120 -110 -100 -90 -80 -70

0 5 10 15 20 25 30

Averaged TS (dB)

Body Length (mm)

120kHz 38kHz

120kHz-38kHz dB difference (dB)

Tilt angle; 30.4°±19.9°

지저장된음향자료를처리하여시공간별수층에존재하는음 향산란층의정량채집에의해난바다곤쟁이를확인하였으며동 해안의분포하는대상생물의분포밀도를추정하였다

. 난바다곤쟁이의 시·공간 분포

동해안포항시구룡포연안해역에분포하고있는난바다곤쟁 이는표층으로부터약

150 m

의수심층을기준으로분포하고있 었으며

, 5

월의경우동물플랑크톤이일몰에따라전형적인연직 상향으로이동하는특성을나타내었다

(Fig. 5).

또한

,

난바다곤 쟁이가전해역에걸쳐광범위하게분포하여

3

^월

(3.2 g/m

²

)

^과

4

월

(3.7 g/m

²

)

에비해높은밀도분포

(29.9 g/m

²

)

로추정되었다

.

6

월과

7

월의경우난바다곤쟁이의밀집도가높았던분포수심

은

120-200 m

연안의해역이었으며

,

연안대륙붕해역에근접

하여분포하였다

(Fig. 6).

에코그램상에분포되어체적후방산

Fig. 5. The vertical distribution of euphausiids Euphausia pacifica at (A) daytime and (B) nighttime in May.

(A)

(B) Day

Night

(June)

(July)

(a) March 2010 (b) April 2010 (c) May 2010

(d) June 2010 (e) July 2010

Meandensity, 3.2 (g/m

²

) Meandensity, 3.7 (g/m

²

) Meandensity, 29.9 (g/m

²

)

Meandensity, 75.8 (g/m

²

) Meandensity, 28.0 (g/m

²

)

Depth (m)

Mean NASC (m

²

/n.mile

²

)

30 15 0 15 30

20 60 100 140 180

March 2010

30 15 0 15 30

20 60 100 140 180

April 2010

-30 -15 0 15 30

20 60 100 140 180

May 2010

30 15 0 15 30

20 60 100 140 180

June 2010

30 15 0 15 30

20 60 100 140 180

July 2010 36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

Fig. 6. The echogram samples of euphausiids Euphausia pacifica vertical distribution in June and July.

Night (B)

(June)

(July)

(a) March 2010 (b) April 2010 (c) May 2010

(d) June 2010 (e) July 2010

Meandensity, 3.2 (g/m

²

) Meandensity, 3.7 (g/m

²

) Meandensity, 29.9 (g/m

²

)

Meandensity, 75.8 (g/m

²

) Meandensity, 28.0 (g/m

²

)

Depth (m)

Mean NASC (m

²

/n.mile

²

)

30 15 0 15 30

20 60 100 140 180

March 2010

30 15 0 15 30

20 60 100 140 180

April 2010

-30 -15 0 15 30

20 60 100 140 180

May 2010

30 15 0 15 30

20 60 100 140 180

June 2010

30 15 0 15 30

20 60 100 140 180

July 2010 36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

Table. 2. The density and biomass of euphausiids Euphausia paci- fica in the survey area

Month Mean density (g/m²) Survey area (km²) Biomass (ton)

March 3.2 155.25 493.3

April 3.7 155.25 5,711

May 29.9 155.25 4,645.4

June 75.8 155.25 11,761.5

July 28.0 155.25 4,345.7

Mean 28.2 155.25 5,391.3

란강도가높았던

6

월의밀도분포는

75.8

로가장높았으며

, 7

월 은

5

월과유사한

28.0 g/m

²의밀도분포를나타났다

(Fig. 7).

월 별난바다곤쟁이의공간분포및밀도의결과

3

월과

4

월에비해

김병관

ㆍ

한인우

ㆍ

오우석

ㆍ

최영민

ㆍ

윤석현

ㆍ

이형빈

ㆍ

이경훈

310

Fig. 7. The spatio-temporal distribution and density estimation of euphausiids Euphausia pacifica.

(A)

(B) Day

Night

(June)

(July)

(a) March 2010 (b) April 2010 (c) May 2010

(d) June 2010 (e) July 2010

Meandensity, 3.2 (g/m

²

) Meandensity, 3.7 (g/m

²

) Meandensity, 29.9 (g/m

²

)

Meandensity, 75.8 (g/m

²

) Meandensity, 28.0 (g/m

²

)

Depth (m)

Mean NASC (m

²

/n.mile

²

)

30 15 0 15 30

20 60 100 140 180

March 2010

30 15 0 15 30

20 60 100 140 180

April 2010

-30 -15 0 15 30

20 60 100 140 180

May 2010

30 15 0 15 30

20 60 100 140 180

June 2010

30 15 0 15 30

20 60 100 140 180

July 2010 36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

Fig. 8. The vertical distribution of euphausiids Euphausia pacifica as mean NASC (Nautical area scattering coefficient) values (m2/n.mile2) from March to July.

(A)

(B) Day

Night

(June)

(July)

(a) March 2010 (b) April 2010 (c) May 2010

(d) June 2010 (e) July 2010

Meandensity, 3.2 (g/m

²

) Meandensity, 3.7 (g/m

²

) Meandensity, 29.9 (g/m

²

)

Meandensity, 75.8 (g/m

²

) Meandensity, 28.0 (g/m

²

)

Depth (m)

Mean NASC (m

²

/n.mile

²

)

30 15 0 15 30

20 60 100 140 180

March 2010

30 15 0 15 30

20 60 100 140 180

April 2010

-30 -15 0 15 30

20 60 100 140 180

May 2010

30 15 0 15 30

20 60 100 140 180

June 2010

30 15 0 15 30

20 60 100 140 180

July 2010 36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

36.2°N

35.9°N

129.4°E 129.8°E

5

^월과

7

^월에약

10

^{배가량의높을밀도를나타냈으며}

, 6

^월기간 에는난바다곤쟁이의밀집도가가장높았다

.

월별평균자원밀 도는

28.2 g/m

²이고조사면적

155.2 km

²이었으며

, 3

월의현존 량은

493.3

톤

, 4

월은

571.1

톤이였으며

, 5

월은

4,645.4

톤

, 7

월은

4,345.7

톤으로현존량이유사하게나타났다

. 6

월에는

11,761.5

톤으로가장높게나타났으며

,

^{조사해역의평균현존량은}

5,391

톤으로추정되었다

(Table. 2).

고 찰

DWBA

음향산란이론모델값을본 논문의

S

_V 주파수차값

을비교한결과

Kang et al.(2003)

의음향산란모델에서는

11.9 dB ≤ TS

_120-38kHz

≤ 19.7 dB

로나타났으며

,

본논문의

dB differ- ence

값인

13.9 dB-17.6 dB

값을비교하였다

.

실제채집시기의

100%

^{에코그램의확인한결과}

, dB difference

^{값이큰개체의} 주파수특성이나왔다

.

동해안포항인근해역에분포하는난바 다곤쟁이는서해안및동중국해역에분포하는난바다곤쟁이보 다체장분포가양봉패턴을나타나므로작은개체부터큰개체 까지다양하게분포하고있으므로향후먹이생물자원의평가지 표로활용가능할것으로판단된다

.

남극크릴은분포해역이동일하여도다양한해양환경에따라 큰변동을나타내고

(Hewitt et al., 2003),

약

4-5

년주기로변동 성을나타내는것으로확인되었다

(Fielding et al., 2014).

난바 다곤쟁이의경우에도남극크릴과같이유영능력이미약하여최 적의환경을찾아자발적으로이동하지못하고해수의유동및 해양환경에의해수동적인수송을나타내는것으로알려져있 으며

,

동해안의경우조류의영향이약하고해수의유동은풍속 및풍향

,

해류의흐름이가장큰유동조건이되며

,

이러한조건 들로인해동해안에서연구된곤쟁이류의현존량추정연구에 서는조석간현존량차이는거의나타나지않는것으로알려져 있다

(Lim et al., 2012; Jo et al., 2012).

크릴류의생물들은밤에는먹이사슬의상위군에있는포식자 들을피해상층으로이동하고낮에는하층에서서식하여섭이

활동을하여일주연직이동을하는것으로알려져있다

(Zhou

and Dorland, 2004; Gaten et al., 2008).

^{본조사에서일출과일} 몰시간대로나누어

2010

년

3

월부터

7

월까지주간과야간에연 직이동에따른평균

NASC

값을

Fig. 8

과같이나타내었다

. 3

월 에는낮시간대에수심

150 m, 4

월에는

60 m

부근에주로분포 하였으며

, 5

월에는표층으로부터

150 m

수심층을기준으로분 포하여주간일출에따른전형적인연직하향이동특성이나타 남을확인하였다

. 6

월의경우에는

120-200 m, 7

월의경우주분

포수심이

50-120 m

의연안해역에분포하여다른시기에비해

높은밀집도로보였다

.

난바다곤쟁이류는동물플랑크톤과마 찬가지로전형적인주

·

야간연직이동특성을나타내므로

,

동해 안대보항인근해역에서주간에난바다곤쟁이를뜰채를이용 하여포획할정도로일시적으로연안해역표층에분포하는현 상은용승과같은해

·

조류의영향으로사료되며

,

향후조사시

유속장을규명할필요가있다고생각되며

,

^{난바다곤쟁이의이} 동경로와주

·

야간에따른수심분포변동성을정확히예측하기 위해서차기연구에서는장기적이고지속적인모니터링과추가 조사가필요하다고사료된다

.

또한

,

본조사해역에서취득한음 향자료와동일시기의수층별수온정보등을포함한해양환경자 료의분석을이용하여동해안에분포하는난바다곤쟁이류의시 기별분포특성을파악한결과를토대로생활사에대한심층적 인분석을통한연구를추가적으로수행할예정이다

.

사 사

본연구는국립수산과학원수산시험연구사업

(R2018039)

의 지원에의해수행되었으며

,

본논문을사려깊게검토하여주신 심사위원님들과편집위원님께감사드립니다

.

References

Conti SG and Demer DA. 2006. Improved parameteriza- tion of the SDWBA for estimating krill target strength.

ICES J Mar Sci 63, 928-935. http://doi.org/10.1016/j.ices- jms.2006.02.007.

Cox MJ, Watkins JL, Reid K and Brierley AS. 2011. Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Geor- gia, 1997-1999. ICES J Mar Sci 68, 489-498. https://doi.

org/10.1093/icesjms/fsq202.

Demer DA and Conti SG. 2005. New target-strength model in- dicates more krill in the Southern Ocean. ICES J Mar Sci 62, 25-32. https://doi.org/10.1016/j.icesjms.2004.07.027.

Everson I. 2000. 3.3 The Southern Ocean. In: Krill Biology, Ecology and Fisheries. Everson I, ed. Blackwell Science Oxford, London, UK, 63-79.

Fielding S, Watkins JL, Trathan PN, Enderlein P, Waluda CM, Stowasser G, Tarling GA and Murphy EJ. 2014. Interannual variability in Antarctic krill (Euphausia superba) density at South Georgia, Southern Ocean: 1997-2013. ICES J Mar Sci 71, 2578-2588. https://doi.org/10.1093/icesjms/fsu104.

Gaten E, Tarling G, Dowse H, Kyriacou C and Rosato E. 2008.

Is vertical migration in Antarctic krill (Euphausia superba) influenced by an underlying circadian rhythm?. J Genet 87, 473. https://doi.org/10.1007/s12041-008-0070-y.

Greenlaw CF. 1977. Backscattering spectra of preserved zoo- plankton. J Acoust Soc Am, 62, 44-52. https://doi.org/10.

1121/1.381503.

Hewitt RP and Demer DA. 1993. Dispersion and abundance of Antarctic krill in the vicinity of Elephant Island in the 1992 austral summer. Mar Ecol Prog Ser 99, 29-39.

Hewitt RP, Demer DA and Emery JH. 2003. An 8-year cycle in krill biomass density inferred from acoustic surveys con- ducted in the vicinity of the South Shetland Islands during

김병관

ㆍ

한인우

ㆍ

오우석

ㆍ

최영민

ㆍ

윤석현

ㆍ

이형빈

ㆍ

이경훈

312

the austral summers of 1991-1992 through 2001-2002.

Aqua Living Resour 16, 205-213. https://doi.org/10.1016/

S0990-7440(03)00019-6.

Jo SG, Kim CA and Suh HL. 2012. Diel and Tidal Distribu- tions of the Sand-burrowing Mysids Archaeomysis kokuboi and Acanthomysis nakazatoi on a Sandy Shore Surf Zone of Yongil Bay, Eastern Korea, in Relation to Growth Stag- es. J Kor Soc Ocean 17, 112-119. https://doi.org/10.7850/

jkso.2012.17.2.112.

Kang DH, Hwang DJ, Soh HY, Yoon YH Suh HL, Kim YJ, Shin HC and Iida K. 2003. Density Estimation of euphau- siid (Euphausia pacifica) in the Sound Scattering Layer of the East China Sea. J Kor Fish Soc 36, 749-756. http://doi.

org/10.5657/kfas.2003.36.6.749.

Kang MH, Furusawa M and Miyashita K. 2002. Effective and accurate use of difference in mean volume backscattering strength to identify fish and plankton. ICES J Mar Sci 59, 794–804. https://doi.org/10.1006/jmsc.2002.1229.

Kim HS, Ju SJ and Ko AR. 2010. Comparisons of feeding ecology of Euphausia pacifica from Korean waters using lipid composition. Ocean Polar Res 32, 165-175. http://doi.

org/10.4217/OPR.2010.32.2.165.

La HS, Lee H, Kang D, Lee S and Shin HC. 2016. Volume back- scattering strength of ice krill (Euphausia crystallorophias) in the Amundsen Sea coastal polynya. Deep Sea Res Part 2 Top Stud Oceanogr 123, 86-91. https://doi.org/10.1016/j.

dsr2.2015.05.018.

Lawson GL, Wiebe PH, Stanton TK and Ashjian CJ. 2008. Eu- phausiid distribution along the western Antarctic Peninsula.

A. Development of robust multi-frequency acoustic tech- niques to identify euphausiid aggregations and quantify eu- phausiid size, abundance, and biomass. Deep Sea Res Part 2 Top Stud Oceanogr 55, 412-431. https://doi.org/10.1016/j.

dsr2.2007.11.010.

Lee JU, Kwon JN, Kim TI and Yang WS. 1994. Some Eco- logical Aspects of Antarctic Krill, Euphausia superba in the Antarctic Ocean. Bull Kor Fish Soc 27, 183-192.

Lee, KH, Mukai T, Kang DH and Iida K. 2004. Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estima- tion. Fish sci 70, 1051-1060. https://doi.org/10.1111/j.1444- 2906.2004.00905.x.

Lim WH, Jung DW, Kim DS and Lee CI. 2012. Distribution of

Euphausia pacifica in East/Japan sea by Numerical Model.

J Kor Soc Mar Environ Saf, 166-168.

Mauchline J. 1980. The biology of mysids and euphausiids. Adv Mar Biol 18, 1-677.

Mauchline J and Fisher LR. 1969. The Biology of Euphausiids.

Adv Mar Biol 7,1-454

McGehee DE, O’Driscoll RL and Traykovski LM. 1998. Effects of orientation on acoustic scattering from Antarctic krill at 120 kHz. Deep Sea Res Part 2 Top Stud Oceanogr 45, 1273-

1294. https://doi.org/10.1016/S0967-0645(98)00036-8.

Mikami H, Mukai T and Iida K. 2000. Measurements of den- sity and sound speed contrasts for estimating krill tar- get strength using theoretical scattering models. Nippon Suisan Gakkai Shi 66, 682-689. http://doi.org/10.1109/

OCEANS.2004.1402947.

Miyashita K, Aoki I, Seno K, Taki K and Ogishima T. 1997.

Acoustic identification of isada krill, Euphausia pacifica Hansen, off the Sanriku coast, north-eastern Japan. Fish Oceanogr 6, 266-271. https://doi.org/10.1046/j.1365-2419.

1998.00042.x.

NIFS (National Institute of Fisheries Science). 2010. Resources untilization and institutionalization of euphausiid, Euphau­

sia pacifica in the East Sea, Korea. Report of National Fish-

eries Research and Development Institute, Busan, Korea.

1-31.

Stanton TK, Chu D and Wiebe PH. 1998. Sound scattering by several zooplankton groups. II. Scattering models. J Acoust Soc Am 103, 236-253. http://dx.doi.org/10.1121/1.421110.

Suh HL. 1988. Review on the reproduction, feeding and longev- ity of the Antarctic Krill, Euphausia superba. Bull. Kor Fish Soc 21, 303-310.

Suh HL, Lim JH and Soh HY. 1998. Population structure of sur- face swarms of the euphausiid Euphausia pacifica caught by drum screens of Uljin nuclear power plant in the east coast of Korea. J Kor Soc Ocean 33, 35-40.

Yoon WD and Kim SW. 2000. Observations on the biology of

Euphausia pacifica(Euphausiacea: Crustacea) in the Yellow

Sea. Bull Nat Sci Yong-In Univ 5, 85-99.

Yoon WD, Cho SH, Lim DH, Choi YK and Lee Y. 2000. Spatial distribution of Euphausia pacifica (Euphausiacea: crusta- cea) in the Yellow Sea. J Plankton Res 22, 939-949. https://

doi.org/10.1093/plankt/22.5.939.

Yoon WD, Yang JY, Lim D, Cho SH and Park GS. 2006. Spe- cies composition and spatial distribution of euphausiids of the Yellow Sea and relationships with environmental factors.

Ocean Sci J 41, 11-29. https://doi.org/10.1007/BF03022402.

Zhou M and Dorland RD. 2004. Aggregation and vertical mi- gration behavior of Euphausia superba. Deep Sea Res Part 2 Top Stud Oceanogr 51, 2119-2137. https://doi.org/10.1016/j.

dsr2.2004.07.009.