Target strength estimation of dominant species in marine ranching ground of Jeju coastal water by KRM model

DOI:10.3796/KSFT.2010.46.2.157

* Corresponding author: [email protected], Tel: 82-51-629-5880, Fax: 82-51-629-5885

Target strength estimation of dominant species in marine ranching ground of Jeju coastal water by KRM model

Seung-Jong L EE , Yoo-Won L EE

*, Joo-Il K IM

, Taeg-Yun O H

, Bo-Kyu H WANG

, Byung-Yeob K IM and Kyoung-Hoon L EE

Subtropical Fisheries research center, Southwest Sea Fisheries Research Institute, National Fisheries Research and Development Institute, Jeju 690-192, Korea

1

Division of Marine Production System Management, Pukyong National University, Busan 608-737, Korea

2

Fisheries Resources Management Division, Southeast Sea Fisheries Research Institute, NFRDI, Busan 619-705, Korea

3

Fisheries Resources Management Division, NFRDI, Busan 619-705, Korea

4

Research Center for Ocean Industry Development, Pukyong National University, Busan 608-737, korea

5

Fisheries System Engineering Division, NFRDI, Busan 619-705, Korea

The indirect target strength (TS) estimation method which uses the Kirchhoff ray mode model (KRM model) was discussed to apply for a biomass estimation in the water of mixed species. TS of 25 live scorpion fishes for 120kHz were measured by a tethered method and of others dominant 5 species in the marine ranching ground of Jeju coastal water including a scorpion fish were also estimated by KRM model. The measurement TS of scorpion fish well agreed with the theoretical values and the standard formula of scorpion fish was estimated as TS

20Log (L) 72.9 (r

0.67). TScm values estimated on trial to each sample of dominant 5 species were from 69.3dB to 75.1dB at 120kHz and they were in the general range of swimbladdered fish. It was clarified that TS by KRM model can be used to estimate fish biomass estimation by increasing a sample number and is more effective under the condition that there is rare TS information for inhabiting species in mixed-species area.

Keywords: Target strength, Dominant species, Kirchhoff ray mode model, Marine ranching ground

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(Simmonds and MacLennan, 2005).

(Hwangbo et al., 2009; Lee, 2005; Lee and Shin, 2005; Moon et al., 2006), Oh and Ahn (2001)

, Kang and Hwang (2003) 38, 120, 200kHz

, Kang et al. (2005,

2009) .

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5m 5m 3m

(a) Lateral (b) Ventral

Fig. 1. Example of digitized and reconstructed shape of a fish body and a swim bladder.

0 100 200 300 400 500 0

100 200 300 400

0 200 400 600 800 100 0 200 400 600 800 100

Fig. 2. System configuration to measure target strength of scorpion fish.

Water suface

120KHz Split beam sensor

Target Underwater

camera 1.8m

2.5m

Suspendea line

Suspendea frame

Water tank(5m 5m 3m)

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, 20cm

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, 50cm, 0.8cm

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, (Sebastiscus marmoratus), (Chrysophrys major),

(Choerodon azurio), (Stephanolepis cir- rhifer), (Pseudolabrus japonicus) 5

X , X

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Beam width( 3dB) 7.1

Pulse length 0.256msec

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Transmitted power 50W

Fig. 3. Total length and body weight of individual scorpion fish used in the experiment.

500

400

300

200

100

0

0 10 20 30 40

Total length (cm)

Weight (g)

Scorpion fish Red sea bream Scarbreast tuskfish Threadsail file fish Bambooleaf wrasse (a) Lateral (b) Ventral (c) Reconstructed fish body shape with coordinates (d) TS patterns for 38kHz (solid line) and 120kHz (dotted line) Fig. 4. Estimated target strength patterns of five main species in marine ranching of Jeju coastal water.

Target strength (dB)

Tilt angle (deg)

,

, KRM

.

TS Fig. 5 .

TS 5,

15 .

TS ,

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, 38kHz 120kHz 2dB

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TS 38kHz 66.8dB, 120kHz 74.0dB (Kang and Hwang, 2003).

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, 38kHz

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72.5dB 38kHz 2dB ,

120kHz 2dB .

TS .

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TS 70

35dB , TS

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TS Fig. 6. Normalized averaged target strengths for each samples obtained by KRM model on trial. Orientation distribution is assumed to be ( 5, 15).

-50

-60

-70

-80

0 5 10 15 20 25

L/ λ

Tscm (dB)

Scarbreast tuskfish

Fig. 5. Comparison of normalized target strengths (TScm) obtained by measurement and theoretical model.

Orientation distribution is assumed to be ( 5, 15) in theoretical model.

-40

-50

-60

-70

Target strength (dB)

1 10 100

Total length (cm)

,

90 TS

(Fig. 7).

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,

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.

TS

.

2009

(RP 2010 FR 009) .

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-30

-40

-50

-60

-70

-80

-90

Target strength (dB)

0 5 10 15 20 25

Tilt angle ( θ)

TL 27.4cm

TL 16.4cm

TL 9.7cm

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