1

Passive acoustical counting of odontocetes using towed and stationed platforms

Akamatsu, T.; Wang, D.; Wang, K.; Li, S.; Dong, S.; Kimura, S.

©photo by X. Wang, courtesy of IHB

2aAB7, 157th Meeting ASA, Portland, USA, May 19, 2009

1.Detect target animals

2.Count target animals

©photo by X. Wang, courtesy of IHB

Two steps of PAM for biological studies

Discrimination of each sound source

Detection probability of PAM

2

White-beaked dolphin@IcelandMiller et al. 2007, MMSC@Capetown

Harbor porpoise@DenmarkDeep-Sea Research II, 54,290-297 (2007)

Finless porpoise @ChinaProc. Roy. Soc. B, 272, 797-801 (2005)

Frequent sound production has been confirmed by A-tags on odontocetes.

1.1.DetectDetect target animalstarget animals

87m17m13m

6-12km/h

Passive Acoustical Method

A-tag (ML200-AS2, Marine Micro Technology, Japan)A-tag is a stereo pulse event recorderSPL, IPI, bearing angle of sound sourcebody (21mm x 112mm, 65g) + hydrophonesReceiving bandwidth; 100-160 kHz (-5dB width)Sensitivity of the hydrophone; -201dB/V at 120kHz730,800 JPY/each +options (I/F box, D cell case)

Akamatsu et al. 2008, JASA

3

Yangtze finless porpoiseThe only freshwater population of finless porpoise

China

Yangtze River

Yichiang Shanghai

Study site and target animals

Yichang

1700km

ShanghaiChina

4

800

600

400

200SPL

(Pa)

14:562006/11/21

14:57 14:58 14:59 15:00

dat

-300

-200

-100

0

100

200

300

time di

fferen

ce

2

4

6

10

2

4

6

PI (

ms)

Bea

ring

angl

e

A trace of a sound source

bow

stern

2. Count target animals

800

600

400

200SPL (Pa)

13:242006/11/21

13:26 13:28 13:30

dat

-300

-200

-100

0

100

200

300

time difference

1

2

4

6

10

2

4

6

PI (ms)

Bea

ring

angl

e

2. Count target animals

5

0

100

200

300

400

500

600

0 200 400 600

Distance measured visually (m)

Dis

tanc

e m

easu

red

acou

stic

ally

(m)

Detection range 300m

300mObservable area

12kｍ

N29, 55

29, 50

29, 45

29, 40

29, 35

116, 20116, 15116, 10116, 05E116, 00 116, 25

1km

Ｎ

揚子江

ポーヤン湖

九江湖口

５

３

1

N29, 55

29, 50

29, 45

29, 40

29, 35

116, 20116, 15116, 10116, 05E116, 00 116, 25

1km

Ｎ

揚子江

ポーヤン湖

九江湖口

５

３

1

５

３

1

ポーヤン湖

116, 20116, 15116, 10116, 05 116, 2

1km

Ｎ

揚子江

九江湖口

５

３

1

ポーヤン湖

116, 20116, 15116, 10116, 05 116, 2

1km

Ｎ

揚子江

九江湖口

５

３

1

５

３

1

Acoustical observation Visual observation

Detected number of animals / km

Acoustics vs. visual

6

ObservableUnknown

How many we missed?

Pa= m / Nv = 1/3

Pv= m / Na = 1/3

N= Na x Nv / m = 9

Na=N x Pa

Nv=N x Pv

m=N x Pa x Pv

ObservableUnknown

Pa ; Acoustical detection probability

Pv ; Visual detection probability

N ; The total number in the strip transect within 300 m of the vessel track

How many we missed?

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Num

ber o

f det

ecte

d in

divi

dual

s

Acoustics

Visual

Matched

Matched

Not matched

A time window

How many we missed?

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 300 600 900

time window (seconds)

Dete

cti

on p

roba

bilit

y

Acoustics

Visual

120s

Detection probabilityAppropriate time window similar to the respiration interval of finless porpoises

Pa= 45.8%

Pv= 18.8%

Akamatsu et al. JASA (2008)

8

0

20

40

60

80

100

120

0 5 10 15

group size (animals/120s)

num

ber

of

groups

acousticsvisual

Group size

Number of animals detected within 2 minutes time window

Akamatsu et al. JASA (2008)

Population size of finless porpoises

between Yichang to Shanghai

ObservableCalculated

Pa= 45.8%

N = 445 = 204 / 0.458

Population size = Density x Area

Density = 0.436 porpoises/km2, where L=1700km, w=600m

Area= 1700-3400 km2, where L=1700km, W=1-2km

Independent visual estimation = 1,111 (CV=0.15)

Zhao et al. Biologocal Conservation (2008)

Estimated Population size = 742 – 1,483This study

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Back and forth over 1000 km from Wuhan to Shanghai

Cargo ship based automatic survey

Ongoing observation

10

20km

Poyang Lake

A bottleneck?

20km

our questionAre the populations going to be fragmented?

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Stationary acoustic monitoringStationary acoustic monitoringof Yangtze finless porpoisesof Yangtze finless porpoises

Monitoring at the possible bottleneck

Short term monitoring at St. 1, 2 & 3

Half year monitoringat St. 3

Yangtze River

Bridge

Poyang Lake

Yangtze River

Bridge

Poyang Lake

12

180

150

120

90

60

30

0

1

Lake side (upstream)

River side (downstream)

Group size counting

2006/04/28

11:19 11:20 11:21 11:22 11:23

degr

ee (θ

)

1 2 2(animals/min.)Kimura et al. JASA (2009)

A bottleneck was suggested

Yangtze River

Bridge

Poyang Lake

Yangtze River

Bridge

Poyang Lake

(Kruskal Wallis test, p<0.01) ＊＊ : p<0.01

0

1

2

3

St. 3 St. 2 St. 1

Ave

rage

num

ber /

min

ute

＊＊ ＊＊

＊＊

Poyang lake

Kimura et al. JASA (2009)

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But porpoises still migrate

-5

-3

-1

1

3

5

7

Num

ber /

day

Up (to Poyang Lake)

Down (to Yangtze River)

19th / May 19th / Jun 19th / July 19th / August 19th / September

Yangtze River

Bridge

Poyang Lake

Yangtze River

Bridge

Poyang Lake

©photo by X. Wang, courtesy of IHB

Conclusions

1.Yangtze finless porpoises could be counted acoustically by towing and stationary stereo pulse event recorders.

2.Acoustics was powerful method to observe isolated animal in the low density area.

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©photo by X. Wang, courtesy of IHB

Acknowledgements

The Yangtze Freshwater Dolphin Expedition 2006 was organized cooperatively by the Institute of Hydrobiology of the Chinese Academy of Sciences, the Administrative Committee of Changjang Fisheries Resource of the Ministry of Agriculture of China, and the baiji.orgFoundation. The acoustic research portion of the expedition was supported by the Program for the Promotion of Basic Research Activities for Innovative Biosciences (ProBRAIN), the Research and Development Program for New Bioindustry Initiatives, and the Fisheries Research Agency of Japan. Sponsorship was provided by the SeaWorld–Busch Conservation Fund, Budweiser Wuhan, Anheuser–Busch Inc., SGS, DEZA, BAFU, the Manfred Hermsen Stiftung Foundation, the Hubbs–SeaWorld Research Institute, the Hubbs Society, and the Ocean Park Conservation Foundation of Hong Kong. We thank Samuel T. Turvey, Robert L. Pitman, Barbara L. Taylor, Jay Barlow , Leigh A. Barrett ,Xiujiang Zhao, Randall R. Reeves, Brent S. Stewart, Zhuo Wei, Xianfeng Zhang, L.T. Pusser, Michael Richlen, and John R. Brandon.