SC/63/O2

Cruise Report of the Second Phase of the Japanese Whale
Research Program under Special Permit in the Western
North Pacific (JARPN II) in 2010 (part I) - Offshore
component –YASUNAGA, G. 1), KIWADA, H. 1), MOGOE, T. 1), WADA, A. 1), NAKAI, K. 1), MORI, M. 2), TSUNEKAWA, M. 2), KASAI,
H. 2), OHSHIMA, T. 2), YOSHIMURA, I. 2), SATO, H. 1), SAKAMOTO, N. 1), WATANABE, H. 3), FUJIWARA, G. 3), OGAWA,
T. 2) AND TAMURA, T. 1)
1) Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan,2) Kyodo Senpaku Co. Ltd., 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan,
3) National Research Institute of Far Seas Fisheries, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa 2368648, Japan
Contact e-mail: yasunaga@cetacean.jp

ABSTRACTThe ninth cruise of the full-scale Second Phase of the Japanese Whale Research Program under Special Permit in
the Western North Pacific (JARPN II) -offshore component- was conducted from 9 June to 22 August 2010 in
sub-areas 7, 8 and 9 of the western North Pacific. The objectives of the JARPN II are (a) feeding ecology andecosystem studies, (b) monitoring environmental pollutants in cetaceans and the marine ecosystem and (c)elucidation of stock structure. Target species in the whale component of JARPN II are the common minke whale
Balaenoptera acutorostrata, sei whale B. borealis, Bryde’s whale B. edeni and sperm whale Physeter
macrocephalus. A total of five research vessels was used: one trawl survey vessel equipped with scientific echosounder (TSV), one dedicated sighting vessel (SV), two sighting/sampling vessels (SSVs) and one research basevessel. A total of 3,749 n.miles was surveyed in a period of 75 days by the SSVs. A total of 15 common minke,
333 sei, 136 Bryde’s, 193 sperm, 36 fin and 10 blue whales were sighted by the SSVs and NM. A total of 14
common minke, 100 sei, 50 Bryde’s and three sperm whales was sampled by the SSVs. All whales sampledwere examined on board the research base vessel. Common minke whales fed mainly on Pacific saury(Cololabis saira). Bryde’s whales fed mainly on Japanese anchovy (Engraulis japonicus) and sei whales fed
mainly on copepods and Japanese anchovy. Dominant preys in the stomach of three sperm whales were various
kinds of squids, which inhabit the mid- and deep-waters. These data will be used in the development of
ecosystem modelling.
KEYWORDS: PACIFIC OCEAN; COMMON MINKE WHALE; BRYDE’S WHALE; SEI WHALE; SPERM
WHALE; MONITORING; FOOD/PREY; ECOSYSTEM; SCIENTIFIC PERMITSINTRODUCTION
The JARPN II started as a full-scale research program in 2002. It has the following research objectives: i)
feeding ecology and ecosystem studies, ii) monitoring environmental pollutants in cetaceans and the marine
ecosystem and iii) elucidation of the stock structure (Government of Japan, 2002).
The full-scale JARPN II plan involves two survey components: the ‘offshore’ survey was covered by the Nisshin
Maru research unit and two ‘coastal’ surveys (Sanriku and Kushiro) covered by small type catcher boats. The
coastal component was necessary to cover the temporal and spatial gaps, which could not be covered by the
Nisshin Maru unit (Government of Japan, 2002).
The research area of offshore component was set in sub-areas 7, 8 and 9, and the target species and sample sizes
were set as follows: 100 common minke whales; 100 sei whales, 50 Bryde’s whales and 10 sperm whales.
In this paper, we present an outline of the ninth full-scale survey of the JARPN II -offshore component-, which
was conducted from 9 Jun to 22 August 2010.

1

MATERIALS AND METHODS
Research area
Sub-areas 7, 8 and 9, excluding the EEZ zones of foreign countries, comprised the research area of the SSV
vessels. Sub-areas 9 and 13, excluding the EEZ zones of foreign countries, comprised the research area of the
SV vessels (Figure 1). These sub-areas were further divided as follows:
Sub-area 7:

Five small blocks (7N, 7MI, 7MO, 7SI and 7SO) stratified by taking into account satellite
information on water temperature.

Sub-areas 8 and 9: Four small blocks were divided at 40ºN in each sub area (8N and 8S, 9N and 9S).
Research vessels
Five research vessels were used. The research base vessel Nisshin Maru (NM: 8,044GT) commanded theresearch and was the platform for biological examination of whale samples and processing of by-products. The
Yushin Maru (YS1: 720GT) and Yushin Maru No.2 (YS2: 747GT) were used as the sighting/sampling vessels(SSVs), which conducted sighting activities, sampling of targeted whale species and various experiments andobservations. The Yushin Maru No.3 (YS3: 742GT), was used as dedicated sighting vessel (SV). The Hokko
maru (HK: 1246GT) was used for the investigation of the distribution and abundance of whale prey species withmidwater trawl, MOHT, VMPS, twin NORPAC nets, and quantitative echosounder, and also to examine
distribution of each whale species in relation to oceanographic and prey environments to estimate habitat andprey preference of each whale.
Survey components
The survey was composed of three main components: whale survey, sighting survey and prey species survey.
Whale survey
Vessels: Three research vessels (NM, YS1 and YS2)
Research area: Sub-areas 7, 8 and 9. In addition, a ‘special monitoring survey’ (SMS) was undertaken in someareas where the number of common minke, Bryde’s and sei whales was expected to be abundant.
Research period Between 9 June and 22 August
Dedicated Sighting survey
Vessels: One research vessel (YS3)
Research area: Sub-areas 9 and 13
Research period: Between 9 June and 18 July
* A report of this sighting survey was presented in document SC/63/O6.
Cooperative survey on the prey species and whale sampling
Vessels: Four research vessels (NM, YS1, YS2 and HK)
Research area:
First period (Western block): A part of sub areas 8 and 9 (NM, YS1, YS2 and HK)

Second period (Eastern block): A part of sub area 9 (NM, YS1, YS2 and HK)

Research period:First period (Western block): Between 24 July and 29 July (NM, YS1, YS2 and HK)

Second period (Eastern block): Between 30 July and 4 August (NM, YS1, YS2 and HK)

Methods for setting cruise track line
Whale survey
Track lines and allocation of vessels were made as in previous JARPN and JARPN II surveys (Fujise et al., 1995,
1996, 1997, 2000, 2001, 2002, 2003; Ishikawa et al., 1997; Zenitani et al., 1999; Tamura et al., 2004, 2005,
2006, 2009a, 2009b; Bando et al., 2010; Matuoka et al., 2008). The zigzag-shaped track line was established on
an arbitrary basis in each sub-area. Furthermore, some ‘special monitoring surveys’ (SMS) were conducted inareas where the abundance of common minke whales, Bryde’s and sei whales was expected to be high. Track2

line in the SMS was designed separately from the original track line. Two SSVs were allocated to these tracks
with the allocation being changed every day. The research course for the SSVs consisted of one main track andone parallel track established 7n.miles apart from the main course.
Dedicated Sighting survey
Apart from the sampling activities, an independent track line for dedicated sighting survey was designed in the
research area. See details in SC63/O6.
Sighting surveys
Sighting procedure both for the whale survey and dedicated sighting survey was similar to the previous surveys
of JARPN and JARPN II (Fujise et al., 1995, 1996, 1997, 2000, 2001, 2002, 2003; Ishikawa et al., 1997;
Zenitani et al., 1999; Tamura et al., 2004, 2005, 2006, 2007, 2009a, 2009b; Bando et al., 2010; Matsuoka et al.,2008). In the research area sighting was conducted mainly under closing mode. Furthermore two modalities ofsighting in closing mode were adopted, NSC and NSS modes, by taking into consideration weather and sea
conditions. The NSC and NSS modes were the same as BC and BS modes in the previous JARPN surveys,
respectively. The conditions to conduct surveys under NSC mode were similar to those established in Japanesesighting surveys conducted by the National Research Institute of Far Seas Fisheries (i.e. visibility of 2n.miles ormore and wind force of 4 or below). The NSS mode was used under bad weather conditions such as heavy rain
and fog when the collection of whale samples was still possible. This NSS mode was used only by SSV vessels.
These two mode surveys were recorded separately for future analysis. Also an ASP mode was used (closing
mode survey without sampling activities under normal sighting conditions).
Closing was performed mainly on sightings of common minke, Bryde’s, sei and sperm whales. Furthermore
closing was made on sightings of large whales, such as blue, humpback, right and fin whales. In these cases,
closing was done in order to confirm species and school size and in order to conduct some experiments.
Sampling of common minke, Bryde’s, Sei and sperm whales
The target species and sample sizes in the 2010 JARPN II offshore component were set as follows: 100 common
minke whales; 100 sei whales, 50 Bryde’s whales and 10 sperm whales.
Most of the whales sighted on the track line were approached for sampling. Furthermore sampling effort wasapplied outside the established research hours (Main time: 07:00-19:00 (12 hrs)), if collection of whale samples
was considered possible.
For schools consisting of two or more animals, numbering was made for all the whales in the school; to set
sampling order randomly in accordance with the table of random numbers (Kato et al., 1989). Cow and calf pairs
were not targeted for sampling.
Sampled whales were immediately transported to a research base vessel, where biological measurements andsampling were carried out.
Experiments
The following experiments and observations were conducted by the sighting/sampling vessels (YS1 and YS2):
1. Sighting distance and angle experiments to examine the precision of sighting data.
2. Biopsy sampling on gray, blue, fin, humpback and right whales.
3. Photographic records of natural marks on blue, humpback and right whales.
4. Feeding behaviour patterns of large whale species (blue, fin, sei, Bryde’s, common minke, humpback, rightand sperm whales).
The following experiments and observations were conducted on board the research base vessel (NM):
1. Observations of marine debris in the sea were conducted from the wheelhouse (during transit cruises)
The following experiments were conducted on board the prey survey vessel (HK):
1. Estimate abundance of prey species of sei and other large whale species (see details in Appendix 1).
2. Observation of whale distribution (see details in Appendix 1).
3. Oceanographic observations using CTD and OPCS (see details in Appendix 2).
3

RESULTS AND DISCUSSIONS
Searching distance
Track line set by the two sighting/sampling vessels (SSVs) is shown in Figure 2. The total searching distance for
SSVs was 3,749n.miles.
Sightings of common minke, Bryde’s, sei and sperm whales
Sighting and sampling vessels (SSVs) and NM
A total of 15 schools (15 individuals) of common minke whales was sighted, consisting of 6 schools (6individuals) of primary and 9 schools (9 individuals) of secondary sightings. For sei whale, 188 schools (333individuals) were sighted, consisting of 89 schools (148 individuals) of primary sightings and 99 schools (185individuals) of secondary sightings. For Bryde’s whale, 104 schools (136 individuals) were sighted, consisting of
83 schools (110 individuals) of primary sightings and 21 schools (26 individuals) of secondary sightings. For
sperm whale, 94 schools (193 individuals) were observed, consisting of 56 schools (108 individuals) of primarysightings and 38 schools (85 individuals) of secondary sightings (Table 1).
Figure 3 shows the distribution of common minke, sei, Bryde’s and sperm whales sighted by the SSVs in the
sub-areas 7, 8 and 9. Sei whales and Bryde’s whales were sighted mainly in offshore sub-areas 8 and 9. On theother hand, common minke whales were sighted in sub-area 9 only. Sperm whales were widely distributed in the
research area.
Sightings of other large cetacean species
Sighting and sampling vessels (SSVs) and NM
Table 1 also shows the number of sightings for other large whale species made by the SSVs, including large
baleen whales such as blue (10 schs./10 inds.), fin (30 schs./36 inds.), and humpback whales (5 schs./6 inds.).
Sampling numbers and biological research for common minke, Bryde’s, sei and sperm whales
A total of 14 common minke whales (Male: 12 individuals, Female: 2 individuals), 100 sei whales (Male: 43
individuals, Female: 57 individuals), 50 Bryde’s whales (Male: 25 individuals, Female: 25 individuals) and threefemale sperm whales were sampled. Struck and lost did not occurr in this research. Table 2 summarizes the
biological data and samples collected from whales. A total of 53 research items was collected. These items are
related to the studies conducted under the three main objectives of the JARPN II: study on feeding ecology ofwhales and marine ecosystem, pollution studies and elucidation of stock structure.
Composition of sex and sexual maturity status of common minke, sei and Bryde’s whales are shown in Table 3.
Statistics of body length of common minke, sei, Bryde’s and sei whales is shown in Table 4. Mean body lengthof common minke whales was 7.39m and 6.85m for males and females, respectively. For sei whales, those were
13.16m and 14.22m for males and females, respectively. For Bryde’s whales, those were 12.10m and 12.58m formales and females, respectively. For sperm whales of females, mean body length was 10.21m.
Geographical distribution of common minke, sei, Bryde’s and sperm whale samples are shown in Figure 4 basedon the sighting positions.
Distribution and food habits of whales
During the research period (from June to August), common minke whales fed mainly on Pacific saury (76.9%)
and Japanese anchovy (23.1%) (Table 5). Sei whales were distributed widely in the offshore area. They fed
mainly on copepods (45.2%) and Japanese anchovy (37.1%) (Table 5). Bryde’s whales were distributed in thesouthern part of the research area. In this survey, Bryde’s whales fed mainly on Japanese anchovy (87.9%)(Table 5). Sperm whales were also distributed widely in the research area. They fed mainly on deep sea squids.
In the 2010 summer, the Pacific saury was scarcely represented in the western North Pacific (FAJ 2010:
http://www.jfa.maff.go.jp/j/press/sigen/100803.html). The low number of sightings of minke whales in summer2010 can be explained by the scarcity of Pacific saury.

4Experiments
Biopsy sampling trial
No experiment was conducted by the SSVs.
Natural marks (photo ID) for large whales
No experiment was conducted by the SSVs.
Feeding and excretion behaviour for large baleen whales
The SSVs had planned to conduct recording of the feeding and excretion behaviour of large baleen whales using
photograph records. No case was observed in this research.

ACKNOWLEDGMENTS
The authors are greatly indebted to Joji Morishita and Shigeki Takaya of the Fisheries Agency of Japan,
Hidehiro Kato, Tokyo University of Marine Science and Technology, and Yoshihiro Fujise, Hiroshi Hatanaka,
Seiji Ohsumi, L.A. Pastene, and Shigetoshi Nishiwaki of the Institute of Cetacean Research (ICR) for theirguidance in the design and implementation of the research. We thank all crew of the research vessels (NM, YS1,
YS2, YS3 and HK) and the staff of the ICR, Kyodo-Senpaku Co. Ltd and NRFSF. The present research project(JARPN II) was funded by a subsidy from the Ministry of Agriculture, Forestry and Fisheries, Government ofJapan.

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5

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6

Table 1. List of cetacean species and number of sightings (no. schools/no. individuals)

Sighting/sampling vessels (YS1 and YS2) and NM
Primary
SecondarySpeciesSch. Ind. Sch. Ind.
Common minke whale
6699Like minke whale0022
Sei whale
89 14899 185Bryde's whale
83 11021 26
Sperm whale
56 10838 85
Blue whale
4
4
6
6
Fin whale
16 18
14 18
Humpback whale
5
6
0
0

7

Total
Sch. Ind.
15 152
2
188 333
104 136
94 193
10 10
30 36
5
6

Table 2. Summary of collected biological data and samples.

Common minke

Research items

F
2
2
0
0
2
0
2
0
2
2
2
1
1
0
0
2
0
2
0
0
2
2
1
1
1
1
1
1
0
0
2
0
0
1
2
0
2
2
1
0
0
2
0
0
2
2
0
2
2
0
0
0
2

Body length and sex
External body proportion
Photographic recoed and external character
Diatom film recoedStandaed measurements of blubber thickness (five points)
Detailed measurements of blubber thickness (eleven points)
Body weight
Body weight by parts
Blubber tissues for DNA study
Blubber, muscle, liver and kidney tissues for heavy metal analysis
Blubber, muscle, liver and kidney tissues for organochlorines analysis
Blubber, muscle tissues for ingredient analysis
Tissue for nutritional compornent analysis
Lung tissue for atmospheric analysis
Tissues for lipid analysis
Tissues for various analysis
Tissues for virus test
M ammary gland; lactation status, measurement and histological sample
Collection of spermaceti sample
Collection of maternal milk sample
Uterine horn; measurement and endometrium sample
Collection of ovary
Photographic record of foetus
Foetal sex (identified by visual observation)
Foetal length and weight
External measurements of foetus
Foetal blubber tissuyes for DNA study
Foetal tissues for various analysis
Foetal lens for age determination
Testis and epididymis; weight and histological sample
Collection of plasma sample
Collection of whole blood sample
Whole blood samples from umbilical coed
Plasma samples from umbilical cord
Stomach content, conventional record
Volume and weight of stomach content in each compartment
Stomach contents for feeding study
Record of external parasites
Collection of external parasites
Record of internal parasites
Collection of internal parasites
Earplug for age determination
Tympanic bulla for age determination
M axillally teeth for age determination
Lens for age determination
Largest baleen plate for morphologic study and age determination
Baleen plate measurements (length and breadth)
Length of each baleen plate series
Vertebral epiphyses sample
Number of vertebrae
Number of ribs
Brain weight
Skull measurements (length and breadth)*: Including fetus of sex unknown.

8

M
12
12
0
0
12
1
12
1
12
12
12
3
3
5
0
12
12
0
0
0
0
0
0
0
0
0
0
0
0
12
12
0
0
0
12
0
12
12
0
0
0
12
1
0
12
12
0
12
12
0
0
1
11

T
14
14
0
0
14
1
14
1
14
14
14
4
4
5
0
14
12
2
0
0
2
2
1
1
1
1
1
1
0
12
14
0
0
1
14
0
14
14
1
0
0
14
1
0
14
14
0
14
14
0
0
1
13

Sei whale
F M
T
57 43 100
57 43 100
0 0
0
0 0
0
57 43 1003 2
557 43 1003 2
557 43 100
57 43 100
57 43 100
3 2
5
3 2
5
0 10 100 0
057 43 100
0 43 43
57 0
57
0 0
0
4 0
4
57 0
57
57 0
57
35 0
35
35 0
35
35 0
35
34 0
34
35 0
35
34 0
34
33 0
33
0 43 43
57 43 100
0 0
0
0 0
0
35 0
35
57 43 1000 0
044 28 72
57 43 100
0 1
1
0 0
0
0 0
0
57 43 100
3 2
5
0 0
0
56 42 98
57 43 100
0 0
0
0 0
0
57 43 100
3 2
5
0 0
0
3 2
5
56 42 98

Bryde's whale

Sperm whale

F
25
25
0
0
25
2
25
2
25
25
25
5
2
0
0
25
0
25
0
0
25
25
15
15
15
15
15
15
13
0
25
0
0
13
25
0
25
25
0
0
0
25
2
0
25
25
0
0
25
2
0
2
25

F
3
3
0
0
3
3
3
2
3
3
3
0
0
3
0
3
0
3
0
1
3
3
1
1
1
1
1
1
1
0
3
0
0
1
3
0
3
3
1
0
0
0
0
0
2
0
0
0
3
3
0
2
3

M
25
25
0
0
25
1
25
1
25
25
25
0
3
10
0
25
25
0
0
0
0
0
0
0
0
0
0
0
0
25
25
0
0
0
25
0
25
25
0
0
0
25
1
0
25
25
0
0
25
1
0
1
25

T
50
50
0
0
50
3
50
3
50
50
50
5
5
10
0
50
25
25
0
0
25
25
15
15
15
15
15
15
13
25
50
0
0
13
50
0
50
50
0
0
0
50
3
0
50
50
0
0
50
3
0
3
50

M
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

T
3
3
0
0
3
3
3
2
3
3
3
0
0
3
0
3
0
3
0
1
3
3
1
1
1
1
1
1
1
0
3
0
0
1
3
0
3
3
1
0
0
0
0
0
2
0
0
0
3
3
0
2
3

Table 3. Composition of sex and sexual maturity status of samples collected during 2010 JARPN II.
MaleSpecies

Sub
area
SA7

Common
minke

SA8
SA9
Combined
SA7

Sei

SA8
SA9
Combined
SA7

Bryde's

SA8
SA9
Combined
SA7

Sperm

SA8
SA9
Combined

FemaleMat.

Imm. Mat. Uk Total

Imm.

0
0
2
2
1
3
11
15
0
0
5
5
0
0
0
0

0
0
1
1
1
3
6
10
0
0
4
4
0
1
0
1

0
0
9
9
4
3
21
28
0
0
19
19
0
0
0
0

0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
0

0
0
12
12
5
6
32
43
0
0
25
25
0
0
0
0

Total
Preg.
Total
Ovu. Rest. Preg. Lact.
Lact.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
2
0
0
1
0
0
1
2
0
1
3
0
0
4
5
0
2
4
0
0
6
9
1
4
28
4
0
37
43
1
7
35
4
0
47
57
0
0
1
0
0
1
1
0
0
0
0
0
0
0
1
5
14
0
0
20
24
1
5
15
0
0
21
25
0
0
0
0
0
0
0
0
0
1
1
0
2
3
0
0
0
0
0
0
0
0
0
1
1
0
2
3

Total
0
0
14
14
10
15
75
100
1
0
49
50
0
3
0
3

Table 4. Body length (m) of samples collected during 2010 JARPN II.
SpeciesCommonminke

Sei

Bryde's

Sperm

Male

Female

Sub
area

n

mean

S.D.

min

max

n

mean

S.D.

min

max

SA7

0

-

-

-

-

0

-

-

-

-

SA8

0

-

-

-

-

0

-

-

-

-

SA9

12

7.39

0.75

5.63

8.00

2

6.85

2.76

4.90

8.80

Combined

12

7.39

0.75

5.63

8.00

2

6.85

2.76

4.90

8.80

SA7

5

13.41

0.43

12.66

13.76

5

13.90

0.91

12.90

15.31

SA8

6

13.09

0.70

12.44

14.32

9

13.80

0.81

12.61

15.32

SA9

32

13.13

1.00

10.52

14.23

43

14.35

0.99

11.14

16.14

Combined

43

13.16

0.91

10.52

14.32

57

14.22

0.97

11.14

16.14

SA7

0

-

-

-

-

1

13.92

-

13.92

13.92

SA8

0

-

-

-

-

0

-

-

-

-

SA9

25

12.10

1.02

9.08

13.21

24

12.53

0.85

10.54

13.78

Combined

25

12.10

1.02

9.08

13.21

25

12.58

0.88

10.54

13.92

SA7

0

-

-

-

-

0

-

-

-

-

SA8

0

-

-

-

-

3

10.21

0.98

9.42

11.30

SA9

0

-

-

-

-

0

-

-

-

-

Combined

0

-

-

-

-

3

10.21

0.98

9.42

11.30

9

Table 5. Dominant prey species and stomach contents weight (1st. + 2nd. stomachs) found in each baleen whale
species.

N

Range of weight
(kg)

3
10

0.3
15.0

-

23.4
49.6

2
Neocalanus spp.
28
Japanese anchovy
23
Pacific saury
8
Spotted chub mackere 1

0.9
0.2
0.4
1.0

27.44

17.1
293.9
236.8
80.9

4
29

1.9
0.2

-

107.8
662.2

Dominant prey species
Common minke whale
Fish

Japanese anchovy
Pacific saury

Sei whale
Krill
Copepods
Fish

Bryde's whale
Krill
Fish

Japanese anchovy

10

9N
7N

8N

7MI 7MO
8S
7SI

9S

7SO

Fig 1. Map showing the research area and strata of the JARPN II full-scale program.

Fig. 2. Track-line set of the sighting/sampling vessels (SSVs).

11

Fig. 3. The positions of the sightings of common minke whale (pink circle), sei (orange square), Bryde’s (green
diamond) and sperm (brown triangle) whales by the two sighting/sampling vessels (SSVs)

Fig. 4. The Sighting positions of the sampled common minke whale (pink circle), sei (orange square), Bryde’s(green diamond) and sperm (brown triangle) whales. Two blocks show the cooperative survey areas ofprey species and whale sampling survey.

12Appendix 1

Cruise report of whale sighting and whale prey species
surveys in the offshore region of the western North Pacificin 2010WATANABE, H. 1), FUJIWARA, G. 1), SAWADA, K.. 2), MATSUURA, T. 2), FUKUDA, Y. 3), OKAZAKI, M. 4), INAGAKE,
D. 4), YASUNAGA, G. 5), KIWADA, H. 5), YOSHIDA, H. 1), AND TAMURA, T. 5)
1)

National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 2368648, Japan
2)
National Research Institute of Fisheries Engineering, Fisheries Research Agency,7620-7 Hasaki, Kamisu,
Ibaraki 314-0408, Japan
3)
Graduate School of Fisheries Science, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611,
Japan
4)
National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648,
Japan
5)
Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan*Contact e-mail: hikaru1@affrc.go.jp

ABSTRACT
Whale sighting and whale prey species surveys in the subarctic and transition regions of the western North
Pacific were conducted in July and August 2010 by R/V Hokko Maru of Hokkaido National Research Instituteof Fisheries Science. The objective of these surveys in this year are to examine habitat and prey preference of sei
whale, hence these surveys were cooperated with the sampling survey of the whale by Nisshin Maru and two
sampling vessels under JARPN II program. The distribution, abundance, and size composition of the whale preyspecies were investigated with the midwater trawl, MOHT, twin NORPAC nets, and quantitative echosounders
during the daylight period. Sei whale was densely distributed in the subarctic boundary where euphausiids wereabundantly distributed at 100–200 m, and also in the subarctic frontal zone where was the main habitat ofJapanese anchovy and Japanese sardine. Because relative abundance of euphausiids and/or these two small
epipelagic fish species seemed to be significantly higher in the main distribution area than its adjacent area of thewhale, sei whale seems to select prey rich environment as their main habitat. The information would be useful toestablish the effective method of dedicated sighting survey for the whale and also establish suitable extrapolation
method of whale abundance in the area where sighting survey was not conducted. Prey preference of the whale,
which is important in relation to establish ecosystem models, will be investigated by comparing the data of preyenvironment and stomach content composition of the whale.
KEY WORDS: SEI WHALE, HABITAT SELECTION, PREY PREFERENCE, WHAKE SIGHTINGSURVEY, PREY SPECIES SURVEY, OFFSHORE REGION, WESTERN NORTH PACIFICINTRODUCTION
Sei whale Balaenoptera borealis is the abundant baleen whale in the western North Pacific and migrates intohigh latitudinal area mainly between 40 and 47˚N during spring and summer from the low latitudinal wintering
area (Kasamatsu et al. 2009). Previous studies have indicated that these whales frequently feed on small
epipelagic fish species such as Japanese sardine Saldinops melanostictus, Japanese anchovy Engraulis japonicus,
and/or Pacific saury Cololabis saira in summer, suggesting the competition between whale and fisheries(Nemoto 1962, Kawamura 1973, Tamura et al. 1998, Tamura and Fujise 2002, Konishi et al. 2009). Subarctic
copepods such as Neocalanus cristatus and N. plumchrus, and euphausiids are also sometimes important prey forsei whale (Nemoto 1962, Konishi et al. 2009). However, quantitative data on the distribution patterns andfeeding habits of these whales in relation to oceanographic conditions and prey environment are extremely
limited. Such information is essential to estimate feeding impact of the whale on commercially important small
epipelagic fish species and also to estimate prey preference of the whale, which are important to establish
13

ecosystem models for multi-species management. Furthermore, these knowledge are also important to estimate
abundance of the whale more accurately, which is related to single species management of the whale, because
extrapolation method of whale abundance in the area where sighting survey is not conducted could beestablished based on the data of habitat preference of the whale. In this document, we mainly reported habitat
preference of sei whale in relation to oceanographic and prey environments. Information on prey preference ofsei whales will be obtained by comparing the prey environment data with stomach content data of the whale in
the future.
Previously, our survey had been conducted to obtain the data of only oceanographic conditions and abundanceof prey species in the environment to estimate prey preference of the whale. However, knowledge on habitat
selection of each whale species is extremely restricted due to lack of quantitative data on their distributions.
Therefore, we newly added whale sighting survey in our research program in this year. We also newly started
several surveys or experiments like measurements of sound speed and density contrasts for major zooplankton
preys such as copepods and euphausiids to estimate abundance of each prey species more accurately based on
acoustic data (see below).

MATERIALS AND METHODS
Whale sighting and whale prey species surveys were conducted in the western North Pacific enclosed by latitude
from 41˚N to 45º30’N and longitude from 156ºE and 163ºE excluding Russian EEZ from 21 July to 10 August2010 by the trawler–type research vessel, Hokko Maru (1246 GT, Hokkaido National Research Institute ofFisheries Science, Fig. 1). This vessel equips 200 kHz echo sounder as was shown below, which is essential toestimate abundance of meso–zooplankton like copepods based on acoustic data. The waypoints of predeterminedtrack lines are shown in Table 1. These surveys by Hokko Maru and whale sampling survey by Nisshin Maruand two sampling vessels under the JARPN II program were conducted concurrently at the same area within 15
hours per day. All surveys were conducted during the daylight period from one hour after sunrise to one hour
before sunset (usually from 03:30 to 17:50 in JST).
Whale sighting survey was conducted along with echosounder survey (see below) basically in passing mode
when wind velocity was less than 10 knots and visibility was more than two nautical miles. However, abeamclosing survey was also conducted within two nautical miles perpendicular to track line in case that the speciesof baleen whale could not identified by passing mode. During the survey, two primary observers were allocatedto the upper bridge.
A Conductivity–Temperature–Depth (CTD, Sea–Bird Co., Ltd.) profiler cast was made down to 500 m depth
at each sampling station to determine the position of the subarctic boundary and subarctic front. Distribution andabundance of the prey species were investigated with midwater trawl, Matsuda–Oozeki–Hu–Trawl (MOHT,
Oozeki et al. 2004), Vertical Multiple Plankton Sampler (VMPS, Tsurumi Seiki Co., Ltd), twin North PacificStandard (NORPAC) nets, and quantitative echosounder on the track lines as follows (Fig. 2). In this year, wenewly conducted the towing survey of each deep scattering layer (DSL) to estimate abundance of prey species,
especially copepods and euphausiids, more accurately by acoustic survey. This information is also essential toestimate feeding depth range of the whale, which is badly needed to estimate prey environment of the whale.

Midwater trawl sampling
The midwater trawl adopted in this study had a mouth opening of approximately 30 x 30 m with a 17.5 mm liner
cod end. The sampling depths and the height of the net mouth were monitored by net monitor system (PI32,SIMRAD). In this survey, trawls were made to identify species and size compositions of acoustic backscatters in
the echosounders and also aimed for collecting data on species difficult to detect by the echosounders such as
squids and neustonic organisms like Pacific saury. Trawling station was predetermined at generally every 20 to
30 nautical mile apart on the track lines. At each predetermined station, a trawl net was towed at 0–30 m for 60
minutes (Table 2). Towing speed was 3–4 knots. All samples were identified to the lowest taxonomic levelpossible and wet body weight of each species was measured aboard the ship. For the major species, individual
body length was measured from randomly selected 100 samples. When sample size was less than 100
individuals, body length was measured for all. We also measured the total wet weight of these samples toestimate the total catch number for each sampling.

MOHT sampling
We firstly used MOHT to examine species and size compositions and vertical distribution patterns ofmacro–zooplanktons, especially euphausiids (Table 2). The mouth opening and mesh size of this net were14

5.06 m2 and 2.0 x 2.0 mm, respectively. MOHT was towed at about 2 knots in the target depths for 10 to 40
minutes. We selected target depths using information of DSL in the echograms of 38, 120, and 200 kHz.
Samples were preserved in 5 % formalin–buffered seawater for later analysis in the laboratory.

VMPS samplingThis is the first time to use VMPS in this survey. VMPS sampling was adopted to examine vertical
distribution and abundance of meso–zooplankton, especially copepods. The mouth opening and mesh sizeof the net were 0.25 m2 and 0.01 x 0.01 mm, respectively. VMPS was towed vertically in three target depths
per one cast (Table 3). Target depths were selected by DSL patterns of each sampling position. The volumeof seawater filtered by each net was measured with a flow meter mounted at the net mouth. Samples were
preserved in 5 % formalin–buffered seawater for later analysis in the laboratory.

Twin NORPAC net sampling
We conducted twin NORPAC net samplings in the 0–150 m layer at all stations to collect data for abundance of
micro– and meso–zooplanktons, especially copepods, in the epipelagic zone. The mouth opening of this net was
0.15 m2 and the mesh sizes of the net were 0.11 x 0.11 mm and 0.33 x 0.33 mm. A flow meter was attached toeach net to measure the volume of seawater filtered. Samples were preserved in 5 % formalin–buffered seawater.

Quantitative echosounder survey
We collected acoustic data by quantitative echsounders, SIMRAD ER60 with operating frequency at 38, 70, 120,and 200 kHz and SIMRAD ES60 with 12 kHz, by steaming at 10 knots on the track lines. Calibrations werecarried out in the coastal region off Shiranuka (42˚53’N, 144˚10’E) on 9 to 10 August using a standard spheretechnique. A tungsten carbide sphere (38.1 mm in diameter) was used as the standard sphere. Acoustic data will
be analyzed with an aid of SonarData Echoview (Sonar Data Co., Ltd.) software.

Other surveys
The following surveys were firstly adopted in our research program. Micropro (Salantic) and Chlorotec (JFEadvance) surveys were conducted in the 0–150 m layer to obtain data on vertical distribution of illumination andprimary production, respectively, in each sampling area. The former data will be analysed in relation to vertical
distribution and/or migration of DSL to estimate vertical distribution of each zooplankton prey and also toestimate species composition of each DSL. Japanese Quantitative Echo sounder and Stereo video camera system(J–QUEST, Sawada et al. 2004, 2009) survey was conducted to obtain target strength in relation to tilt angle ofJapanese anchovy and to identify the species of the scattering layer interested in the echograms, which areessential to estimate abundance of these prey species more accurately based on acoustic data. Furthermore, twoliving copepod species, N. cristatus and N. plumchrus, and living euphausiids mainly Euphausia pacifica, were
sorted and sound speed and density contrasts of each species were measured by time of flight method anddensity bottle method, respectively (Mikami et al. 2000). These experiments are important in relation to obtaintheoretical values of target strength of these species, which are essential to estimate abundance of these preys by
acoustic data.

RESULTS AND DISCUSSION
A total of 12 midwater trawl surveys, 10 MOHT surveys, 12 VMPS surveys, 20 NORPAC surveys, and four J–
QUEST surveys were conducted (Tables 3 to 6). Sound speed and density contrasts of zooplanktons were
measured nine times for copepods and three times for euphausiids (Tables 7 and 8). While most of theseanalyses, together with Micropro and Chlorotec analyses are currently underway, the preliminary results are as
follows.
In this study area, two oceanographic fronts, subarctic front between subarctic region and transitional domain,and subarctic boundary between transitional domain and transition zone are distributed (Favorite et al. 1976,
Pearcy 1991). According to Kawai (1972) and Murakami (1994), subarctic front is defined by a watertemperature lower than 5˚C at 100 m. Sub arctic boundary is defined by 34.0 PSU salinity front in the epipelagiczone (Favorite et al. 1976). In the western survey area, subarctic boundary and subarctic front was locatedbetween 41 and 42˚N and 44 and 45˚N, respectively (Fig. 3). In the eastern survey area, salinity in the epipelagiczone was > 34.0 PSU, indicating that this area was located north of subarctic boundary. In this area, water15

temperature at 100 m was less than 5˚C except for the area north of 45˚N. However, water mass warmer than
5˚C was found at 150-200 m layer south of 43˚N and between 44˚30’ and 45˚N, suggesting that these areas werelocated in the transitional domain. Therefore we deemed subarctic front to be located at both between 43 and44˚N and 44 and 45˚N (Fig. 3).
A total of 358 nautical miles was searched. A total of 26 animals of 21 schools (five baleen whale species andsperm whale) were found by primary sighting (Table 9). Of these, sei whale was the most abundant in the baleen
whale community of this study area.
‘‘Hot spot’’ of sei whale was found in the region around subarctic boundary and subarctic front (Fig. 4). The
result of our survey indicated that euphausiids were significantly abundant in the subarctic boundary than in thenormal transition zone and the transitional domain and abundance of Japanese anchovy and Japanese sardine
was significantly higher in the subarctic frontal zone than in the normal transitional domain and the subarctic
region (Figs. 5 and 6). Therefore, sei whale might select prey rich area as their main habitat. This probably
indicates that main distribution of sei whale could be estimated using information of oceanographic features.
When sighting survey was mainly conducted in such areas, abundance of the whale could be estimated moreaccurately and also more effectively.
Sound speed contrasts of copepods and euphausiids were ranged from 1.012 to 1.034 (n = 7) and from 1.026
to 1.035 (n = 3), respectively, and density contrast was 0.993–1.005 (n = 58) for copepods and 1.038–1.055 (n =20) for euphausiids (Tables 7 and 8). Sound speed contrast tended to decrease with increasing temperature forboth copepods and euphausiids, indicating that information of habitat temperature is indispensable to estimate
biomass of these zooplanktons by acoustic data (Table 7).

ACKNOWLEDGEMENT
A special thank is given to Captain S. Toishi and crews of Hokko Maru for their skilful assistance in collecting
data. Drs. Y. Matsuo, D. Kitagawa, and O. Yamamura and Mr A. Kusaka of Hokkaido National ResearchInstitute of Fisheries Science and Dr H. Sugisaki of National Research Institute of Fisheries Science kindly
allowed us to use CTD and sampling gears. Dr. T. Ichii of Japanese Fisheries Agency shared his knowledge ofthe oceanographic condition and primary production in the transitional region.

REFERENCES
Favorite, F., Dodimead, A. J. and Nasu, K. 1976. Oceanography of the subarctic Pacific region, 1960-71. Bull.
International North Pacific Fisheries Commission, 33, 187 pp.
Kasamatsu, F., Miyashita, T. and Yoshioka, M. 2009. Field guide to whales, dolphins, and porpoises in rhewestern North Pacific and adjacent waters (new edition, Ohsumi S. ed). Tokyo: Tokyo University Press (inJapanese).
Kawai, H. 1972. Hydorography of the Kuroshro and the Oyashio. In Physical oceanography II. Fundamental
Lectures of Oceanography (Masuzawa, J. ed), 129-321. Tokyo: Tokai University Press (in Japanese).
Kawamura, A. 1973. Food and feeding of sei whale caught in the waters south of 40˚N in the North Pacific. Sci
Rep Whales Res Inst, Tokyo 32: 155-197.
Konishi, K., Tamura, T., Isoda, T., Okamoto, R., Matsuoka, K. and Hakamada, T. 2009. Feeding strategies andprey consumption of three baleen whale species within the Kuroshio-Current extension. J. Northw. Atl. Fish.
Sci. 42: 27-40.
Mikami, H., Mukai, T. and Iida, K. 2000. Measurement of sound speed and density rates of euphausiids toestimate their target strength by theoretical model. Nippon Suisan Gakkaishi, 66: 682-689. (in Japanese withEnglish abstract).
Murakami, M. 1994. On long-term variations in hydrographic conditions in the Tohoku area. Bull Tohoku NatlFish Res Inst 56: 47-56. (in Japanese with English abstract).
Nemoto, T. 1962. Prey items of baleen whale. Report of Institute of Cetacean Research 4, 136 pp. (in Japanese).
Oozeki, Y., Hu, F., Kubota, H., Sugisaki, H. and Kimura, R. 2004. Newly designed quantitative frame trawl forsampling larval and juvenile pelagic fish. Fish. Sci. 70: 223-232.
Pearcy, W.G. 1991. Biology of the Transition Region. NOAA Tech. Rep. NMFS, 39-55

16

Sawada, K., Takahashi, H., Takao, Y., Watanabe, K., Horne, J. K., McClatchie, S. and Abe, K. 2004.
Development an acoustic-optical system to estimate target-strengths and tilt angles from fish aggregation.
Oceans04/Tech-Ocean04 Proceedings, 395-400.
Sawada, K., Takahashi, H., Abe, K., Ichii, T., Watanabe, K. and Takao, Y. 2009. Target strength, length, tiltangle measurements of Pacific saury (Cololabis saira) and Japanese anchovy (Engraulis japonicus) using an
acoustic-optical system. ICES J. Mar. Sci. 66: 1212-1218.
Tamura, T., Fujise, Y. 2002. Geographical and seasonal changes of the prey species of minke whale in the
Northwestern Pacific. ICES J. Mar. Sci 59: 516-528.
Tamura, T., Fujise, Y. and Shimazaki, K. 1998. Diet of Minke Whales Balaenoptera acutorostrata in the
Northwetern Part of the North Pacific in Summer 1994 and 1995. Fish. Sci 64: 71-76.

17

Fig. 1. Research area and track lines of whale sighting and whale prey species surveys in July-August 2010.

18

1. Whale sighting survey

3. Towing survey: To identify species and size
compositions of acoustic backscatters of:

5. Survey for the progress of acoustic data analysis
Measurement ofsound speed anddensity contrasts for
copepods andeuphausiids.

Copepods:
VMPS
2. Acoustic survey
Euphausiids:

J-QUEST survey

MOHT
Fishes:MidwaterTrawl
4. Oceanographic and NORPAC survey (conducted each sampling stations)
We also conducted
Micropro and Chlorotec
surveys at each station

CTD

Norpac net

Fig. 2. Survey method

19

Measurement of
wet weight for eachprey species

Measurement of size
composition foreach prey species

Fig. 3. Vertical temperature and salinity profiles along with the eastern (left) and western (right) track lines.

20

C
B

A

Fig. 4. Distributions of two oceanographic fronts and sighting positions of sei whale in July-August 2010.
Results of primary sighting indicated that 4 animals of 3 schools, 5 animals of 4 schools, and 4 animals of 3 schools of sei whales were distributed at the areas A, B,
and C, respectively.

21

Euphausiids

Ephausiids

Fig. 5. Typical ecogram in the subarctic boundary where sei whales were densely distributed (left), and in the northern and southern region of subarctic boundary(right). Euphausiids was more abundantly distributed in the former region than in the latter region.

Janaese anchovy and Japanese sardine was frequently distributed

Small epipelagic fish species were rarely distributed

Fig. 6. Typical ecogram in the subarctic frontal zone where sei whales were densely distributed (left), and in the northern and southern region of the front (right).
Small epipelagic fish species such as Japanese anchovy and Japanese sardine was frequently and rarely distributed in the former and the latter regions,
respectively.

22

Table 1. Waypoints of track lines.
WP
501
503
505
507

Latitude (N) Lingitude (E)41-00.0
159-00.042-30.0
156-00.0
44-00.0
159-00.045-40.0
156-40.0

521
522
523

42-30.044-00.045-30.0

163-00.0
166-00.0
163-00.0

Table 2. Sampling data of midwater trawl surveys. 0.0: CPUE < 0.1 kg.
Sampling
CPUE (kg/h)
SST Latitude
Longitude
Sampling depth (m) duration Japanese Japanese Common Pacific Coho
Chum Pacific Other Common
Stn Year Month Day (ūC) Degree Minute N/S Degree Minute E/W Shallowest Deepest (min)anchovy sardine mackerel saury salmon salmon pomfret fishes squid
1 20107
24 17.9
41
11.1
N
158
38.4
E
0
30
60
5 20107
26 16.6
42
37.0
N
156
14.6
E
0
30
60
37.2
12.4
0.9
13.1
3.8
24.4
7 20107
27 15.7
43
27.3
N
157
54.5
E
0
30
60
42.1
9.5
0.4
4.0
2.2
7.3
8 20107
28 15.4
43
49.3
N
158
38.6
E
0
30
60
138.0
5.2
1.5
1.9
1.7
9 20107
28 15.3
44
10.8
N
158
40.2
E
0
30
60
2.6
0.0
0.8
11 20107
29 13.6
44
37.4
N
157
46.0
E
0
30
60
236.4
7.1
50.3
0.1
13
15
16
17
19
20

2010
2010
2010
2010
2010
2010

7
8
8
8
8
8

31
1
2
2
3
4

13.9
13.3
12.7
12.4
13
13.1

42
43
43
44
44
45

59.0
36.0
57.3
21.8
49.9
18.9

N
N
N
N
N
N

163
165
165
165
164
163

57.7
11.5
54.6
12.2
23.3
23.4

E
E
E
E
E
E

0
0
0
0
0
0

30
30
30
30
30
30

23

60
60
60
60
60
60

26.9
2.8

0.0
0.0

348.7

0.0
15.3

10.2
1.0

14.5

161.6
11.7

1.5
234.4
46.6
2.0
3.8

2.3
11.4
10.1

26.9
45.7
13.4

0.0

Table 3. Sampling data of MOHT surveys.

Stn
2
3
4
6
10
10

Year
2010
2010
2010
2010
2010
2010

12
12
14
18

2010
2010
2010
2010

SST Latitude
Longitude
TargetSampling duration at
Month Day (ūC) Degree Minute N/S Degree Minute E/W depth (m) the target depth (min)7
24 17.9
41
25.8
N
158
9.6
E
170
18
7
25 15.2
41
38.6
N
157
43.4
E
200
41
7
26 16.3
42
34.0
N
156
7.4
E
50
30
7
27 15.8
43
9.0
N
157
17.5
E
210
27
7
29 13.0
44
30.9
N
157
58.5
E
220
9
7
29 13.0
44
30.9
N
157
58.5
E
300
25
7
7
8
8

31
31
1
3

14.2
14.1
13.3
13

42
42
43
44

42.0
40.2
22.0
32.4

N
N
N
N

163
163
164
164

23.7
20.4
44.1
55.2

24

E
E
E
E

45
120
275
0 to 300

30
25
15
-

Main
catch
Euphausiids
Euphausiids
Copepods
Euphausiids
Copepods
Euphausiids
Copepods
Copepods
Copepods
Copepods

Remarks

Oblique tow

Table 4. Sampling data of VMPS surveys.

Stn
4

6

8

11

11

12

12

14

14

16

18

20

SST Latitude
Longitude
Sampling depth (m)Flow meter
countYear Month Day (ūC) Degree Minute N/S Degree Minute E/W Shallowest Deepest
20107
26 16.3
42
34.0
N
156
7.4
E
0
250
30
200
250
24
100
200
46
30
100
32
2010
7
27 15.8
43
9.0
N
157
17.5
E
0
270
21
240
270
44
130
240
40
39
130
14
2010
7
28 15.4
43
49.3
N
158
38.6
E
0
240
51
160
240
38
65
160
39
25
65
22
2010
7
29 13.6
42
25.3 N
156
10.7 E
0
330
41
253
330
27
144
253
43
55
144
38
2010
7
29 13.6
44
25.5 N
156
10.8 E
0
70
8
50
70
9
36
50
6
19
36
7
2010
7
31 14.2
42
38.6 N
163
16.7 E
0
280
14
260
280
8
150
260
40
70
150
31
2010
7
31 14.2
42
38.6 N
163
16.7 E
0
70
4
40
70
11
10
40
12
0
10
4
2010
8
1 13.343
22.2 N
164
44.4 E
0
275
9
240
275
16
200
240
13
50
200
68
2010
8
1 13.343
22.2 N
164
44.4 E
0
50
2
24
50
9
10
24
6
0
10
5
2010
8
2 12.744
18.6 N
166
5.2 E
0
85
3
58
85
12
20
58
13
0
20
7
2010
8
3
13
44
32.4
N
164
55.2
E
0
150
15
65
150
31
23
65
16
5
23
7
2010
8
4 13.1
45
18.9
N
163
23.4
E
0
322
28
228
322
52
54
228
95
29
54
15

25

Table 5. Sampling data of NORPAC net surveys.

Stn
1
2
3
4
5
6
7
8
9
10
11

SST Latitude
Longitude
Sampling depth (m) Flow meter countYear Month Day (ūC) Degree Minute N/S Degree Minute E/W Shallowest Deepest XX13 GG54
2010
7
24 17.9
41
11.1
N
158
38.4
E
0
150
1440
1418
2010
7
24 17.9
41
25.8
N
158
9.6
E
0
150
1525
1530
2010
7
25 15.2
41
38.6
N
157
43.4
E
0
150
1583
1560
2010
7
26 16.3
42
34.0
N
156
7.4
E
0
150
1550
1582
2010
7
26 16.6
42
37.0
N
156
14.6
E
0
150
1682
1660
2010
7
27 15.8
43
9.0
N
157
17.5
E
0
150
1463
1560
2010
7
27 15.7
43
27.3
N
157
54.5
E
0
150
1463
1660
2010
7
28 15.4
43
49.3
N
158
38.6
E
0
150
1540
1600
2010
7
28 15.3
44
10.8
N
158
40.2
E
0
150
1440
1525
2010
7
29 13.0
44
30.9
N
157
58.5
E
0
150
1435
1475
2010
7
29 13.6
44
37.4
N
157
46.0
E
0
150
1590
1545

12
13
14
15
16
17
18
19
20

2010
2010
2010
2010
2010
2010
2010
2010
2010

7
7
8
8
8
8
8
8
8

31
31
1
1
2
2
3
3
4

14.2
13.9
13.3
13.3
12.7
12.4
13
13
13.1

42
42
43
43
43
44
44
44
45

42.0
59.0
22.0
36.0
57.3
21.8
32.4
49.9
18.9

N
N
N
N
N
N
N
N
N

163
163
164
165
165
165
164
164
163

23.7
57.7
44.1
11.5
54.6
12.2
55.2
23.3
23.4

E
E
E
E
E
E
E
E
E

0
0
0
0
0
0
0
0
0

150
150
150
150
150
150
150
150
150

1445
1529
1440
1473
1570
1520
1472
1488
1523

1482
1518
1448
1488
1587
1582
1485
1536
1565

Table 6. Survey data of J-QUEST cast.

Stn
2
4
14
21

Year Month Day
2010
7
24
2010
7
26
2010
8
1
2010
8
5 to 6

SST Latitude
Longitude(ūC) Degree Minute N/S Degree Minute E/W Target depth (m)Target animals
17.9
41
25.8
N
158
9.6
E
160 and 349
Copepods, euphausiids
16.3
42
34.0
N
156
7.4
E 5, 10, 20, and 50 Copepods, euphausiids
13.3
43
22.0
N
164
44.1
E 30, 40, and 260
Copepods, euphausiids
17.3
44
18.732 N
159
22.4
E
20
Japanese anchovy

Table 7. Data of sound speed contrasts for each zooplankton species obtained by Hokko Maru cruise in 2010.

Date

SpeciesID

St.

20100725
20100727

Copepods
Euphausiids
Euphausiids
Euphausiids
Copepods
Copepods
Copepods
Copepods
Copepods
Copepods
Copepods
Copepods

Cope001
OKI001
OKI002
OKI003Cope002
Cope003
Cope004
Cope005
Cope006
Cope007
Cope008
Cope009

3
6
6
10
12
12
12
12
14
16
17
18

20100729
20100731

20100801
2010080220100803

Sampling
gyer
MOHT 1st
MOHT 1st
MOHT_1st
MOHT 2nd
MOHT_1st
MOHT 1st
MOHT 1st
MOHT 1st
MOHT 1st
NORPACNORPACNORPAC

Volume fraction of
Euphausiids and Copepods[%]
30
45
48
42
54
31
44
34
36
35
4

26

Temperature[℃]
5.8-11.8
7.6-11.9
7.3-11.8
9.4-11.7
9.0-11.8
6.5-11.7
5.6-12.0
4.5-12.0
1.9-11.8
6.1-11.9
4.5-11.8

Sound speed
contrast
1.0267-1.0342
1.0304-1.0324
1.0255-1.0293
1.0318-1.0351
1.0129-1.0143
1.0122-1.0181
1.0120-1.0185
1.0135-1.0177
1.0141-1.0241
1.0141-1.0213
1.0259-1.0657

Table 8. Data of density contrasts for each zooplankton species obtained by Hokko Maru cruise in 2010.
TL: Total length; PL Prosome length; CL: Carapace length; AB: Length of sixth abdominal segment.
Sampring
date
20100725

20100727

20100729

20100731

St.
3

6

10

12

Sampring
gyer
MOHT

MOHT

MOHT

MOHT_1st

SpeciesID

Copepods

Cope001
Cope022
Cope023
Cope024
Cope025
Cope026
Cope027
Cope052
Cope053
Cope054
OKI001
OKI002
OKI003
OKI004
OKI005
OKI006
OKI017
OKI018
OKI019
OKI020
OKI007
OKI008
OKI009
OKI010
OKI011
OKI012
OKI013
OKI014
OKI015
OKI016
Cope002
Cope003
Cope004
Cope005
Cope006
Cope17
Cope18
Cope19Cope20
Cope21
Copr049
Cope050
Cope051
Cope007
Cope008
Cope009
Cope010
Cope011
Cope012
Cope013
Cope014
Cope015
Cope016
Cope041
Cope042
Cope043
Cope044
Cope045
Cope046
Cope047
Cope048
Cope028
Cope029
Cope030
Cope031
Cope032
Cope033
Cope034
Cope035
Cope036
Cope037
Cope038
Cope039
Cope040
Cope055
Cope056
Cope057
Cope058

Euphausiids

Euphausiids

Copepods

20100801

14

MOHT 1st

Copepods

2010080216

NORPAC

Copepods

2010080217

NORPAC

Copepods

20100803

18

NORPAC

Copepods

TL or PL
[mm]
6.78
6.46
6.5
6.5
6.7
6.7
6.34
6.7
6.74
6.3
10.48
12.56
10.56
12.72
11.36
12.8
10.24
10.4
10.43
12.16
20.08
21.6
20.4
13.6
20.88
20.4
20.16
20.08
21.52
19.36
6.38
6.17
6.46
6.62
6.42
6.3
6.54
6.54
6.78
6.78
6.66
6.02
6.46
6.62
6.98
6.78
6.58
6.86
7.18
6.98
6.94
6.78
6.4
6.36
6.7
6.46
6.82
3.92
3.94
3.72
3.89
6.7
6.98
6.94
6.9
6.7
6.7
6.74
6.7
3.72
3.79
3.77
3.89
3.64
3.82
3.84
3.84
3.77

CL[mm]

3.1
3.64
2.95
3.55
3.18
3.57
3
3.05
3
3.59
5.54
6.54
6.06
3.82
6.2
6.08
6.06
5.98
6.26
5.83

27

AB[mm]

1.48
1.82
1.53
1.75
1.72
1.82
1.58
1.48
1.53
1.77
2.17
3.1
2.98
1.92
3
2.91
2.81
2.91
3.05
2.91

Body height
[mm]
1.92
1.63
1.82
1.75
1.77
1.77
1.77
1.53
1.77
1.58
1.03
1.33
0.96
1.21
0.98
1.23
0.89
0.89
0.94
1.18
1.58
2.24
2.17
1.28
2.12
2.07
1.97
2.04
2.22
2.07
1.85
1.55
1.67
1.75
1.23
1.72
1.77
1.63
1.58
1.82
1.53
1.33
1.48
1.63
1.92
1.9
1.63
1.67
1.97
1.92
1.67
1.87
1.77
1.63
1.72
1.63
1.58
1.08
1.08
1.03
1.03
1.77
1.87
1.87
1.72
1.67
1.77
1.72
1.82
0.94
0.98
1.03
1.18
1.03
0.98
1.08
1.08
0.98

Body width
[mm]
2.07
2.07
1.82
1.97
1.95
1.97
1.92
2.02
1.95
1.87
1.08
1.38
1.08
1.28
1.23
1.33
1.03
1.03
1.03
1.28
1.48
2.31
2.27
1.4
2.12
2.22
2.24
2.02
2.31
2.02
1.85
1.77
1.82
2.02
1.77
1.97
1.97
1.97
1.82
1.95
2.02
1.82
2.02
2.02
1.95
2.02
2.07
1.99
2.04
1.99
2.07
1.92
1.92
1.87
2.02
2.12
2.27
1.28
1.33
1.28
1.43
2.02
1.99
2.02
2.07
1.9
1.97
1.92
2.02
1.18
1.31
1.28
1.26
1.13
1.23
1.28
1.33
1.28

Densitycontrast
0.9991
0.99600.9961
0.9976
0.9986
0.9986
0.99871.00000.99821.00001.05191.0452
1.0452
1.0472
1.0482
1.04901.05291.05011.05511.04601.05111.0403
1.0512
1.04471.0382
1.0426
1.04701.04491.04051.04181.00191.00591.0032
1.00271.00051.00251.00611.00251.00371.00831.00441.00311.00501.00271.00161.00271.00271.00161.00261.00151.00091.00251.00251.00641.00531.00291.00280.99900.99901.00131.00001.00061.0032
1.00251.00151.00161.00631.00411.00281.00031.00130.99991.00191.00081.00191.00081.00360.9995

Measurementdate
20100725
20100807

20100808
20100727

20100730

20100729

20100730

20100731

20100801

20100808
20100801

20100808

20100807
20100808

20100808

Table 9. Results of sighting survey for large cetacean species.

Species
Sei whale
Fin whale
Common minke whale
North Pacific right whale
Humpback whale
Sperm whale
Total

Primary sighting
Schools Animals
10
13
3
5
2
2
2
2
2
2
2
2
21

26

28

Secondly sighting
Schools Animals
1
1
2

2

3

3

Appendix 2
Oceanographic conditions in the survey area of offshore component of
JARPN II in the western North Pacific in July to August 2010INAGAKE, D.1), OKAZAKI, M.1), WATANABE, H.2), YOSHIDA, H.2) AND MIYASHITA, T.2)

1) National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa,236-8648, Japan
2) National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa,236-8648, Japan
Contact e-mail: ina@fra.affrc.go.jp

ABSTRACT
A whale sighting and whale prey species surveys were conducted from July 24 to August 4 in 2010 using
R/V Hokko-Maru along with offshore component of JARPN II. The survey covered transition domain
and subarctic area in the western North Pacific where sei whale was abundantly distributed in the baleen
whale community. During the survey, oceanographic observation with CTD was operated to make clear
the environment in and around the habitat of both cetaceans and its prey species. The survey area wasalmost located in the transition domain, except for two stations in the subarctic domain. The water mass
was characterized by the subarctic water and the mixed water between the subarctic water and theKuroshio water.

INTRODUCTION
Whale sighting and whale prey species surveys were conducted in the offshore area of the western North
Pacific from July 24 to August 4 in 2010 using R/V Hokko-Maru (Fig. 1) in cooperation with the whale
sampling survey by Nisshin-Maru and two sampling vessels. Sei whale Balaenoptera borealis was themost common baleen whales in the survey blocks.
There are a lot of water masses and fronts in the western North Pacific. The Oyashio flows
southwestward along the Kuril Islands and turns eastward from the northern coast of Japan. The Kuroshio
flows northward from the tropical area to Tohoku area east of Japan, and reaches near the Oyashio front.
The Kuroshio turns eastward from the northern coast of Japan, and the strong eastward flow is called theKuroshio Extension. Both major current, the Kuroshio Extension and the Oyashio, form KuroshioOyashio Inter-frontal Zone. Water masses originated in the Kuroshio and the Oyashio are mixed eachother in this zone and form new water masses.
In the high sea of the North Pacific Ocean, there are subarctic front (temperature front defined by 4℃)
and the subarctic boundary (salinity front defined by 34.0psu) with a weak eastward flow. The subarctic
front is south limit of the subarctic water and the subarctic boundary is north limit of the tropical water.
The area between these fronts is called the transition domain (Favorite et al. 1976).
Each water mass in the western North Pacific has its own ecosystem, like a Kuroshio ecosystem, anOyashio ecosystem, warm-core ring ecosystem, etc. So, we must make clear the oceanographic condition
around whale’s prey to build up a marine ecosystem model in this area. In this paper, distributions ofwater masses and fronts in the survey area will be described to make clear the environment of the
distribution area of sei whale.

29

METHODS
Hydrographic observations with a conductivity-temperature-depth profiler (CTD) were carried out in thesurvey area from July 24 to 4 August in 2010 using R/V Hokko-Maru (Table 1 and Fig. 1). Salinity
correction for CTD data was not done using water sampling data.
Locations of oceanic fronts and water masses are usually detected based on subsurface temperaturemap (see Table 2), because they are obscure in sea surface temperature distributions from summer to fall,
and the Oyashio water spreads into the subsurface layer. The oceanographic conditions in July-August2010 are detected by 100m and 200m temperature maps using our observation data by the vessel as well
as NEAR-GOOS (the North-East Asian Regional-Global Ocean Observing System) database. We use
following indices to know the distribution of water mass in the survey area. The Kuroshio Extension isdefined by the 14℃ isotherm at the depth of 200m (Kawai , 1969). The warm water spread from
Kuroshio Extension is defined by temperature more than 10℃ at the depth of 100 m. The subarctic front
and the subarctic boundary is defined by 4℃ temperature front and 34.0 psu salinity front, respectively(Favorite et al. 1976).

RESULTS AND DISCUSSION
Oceanographic conditions in the survey area
Figure 2 shows the Temperature-Salinity diagrams in the survey area. There is no typical Kuroshio water
characterized by high salinity profile around 34.5 psu. The warm water spread from the Kuroshio withwarm (over 10℃) and high salinity (over 34 psu) water was observed at the surface layer in Stn. 1, only
one station. The dominant water in this area was subarctic water characterized by cold profile less than
4℃, which is shown in lower part of Fig. 2. The mixed water in transitional domain is distributed
between subarctic waters and warm water spread from the Kuroshio.
Figure 3 shows a schematic hydrographic map with isotherms of 100 m temperature from July 16 toAugust 15 in 2010. The cold water less than 5℃ at 100 m depth was distributed in a northern part of thesurvey area. The subarctic front, which is defined by 4℃ isotherm and corresponds to 33.4 psu isohaline
in Fig. 5, was observed around 44ﾟN, 158ﾟE in Figs. 3 and 4. In 100 m salinity map (upper panel in Fig.
5), all of salinity value showed less than 34.0 psu, so the survey area was north of the subarctic boundary,which is defined by a salinity front of 34.0 psu. The warmest temperature at the 200 m depth was 6 ,which was observed at southwestern part of this area (lower panel in Fig. 4). The Kuroshio Extension
defined by 14℃ isotherm at 200 m depth meandered along 37ﾟN line, far from our survey area.
Figure 6 shows temperature, salinity and density anomaly sections in the western part of the survey
area. A seasonal thermocline lied at the depth of 50 m, and temperature at the surface mixing layer
shallower than 30 m was warmer than 10℃ in this section. The subarctic water (colder than 4℃) was
observed in deeper layer than 200 m in the southern part and 50 m in the northern part of this section.
The subarctic front observed around 44ﾟ15’N, where the 4℃ isotherm and 33.4 psu isohaline lie
vertically. The salinity front around 34 psu (index of the subarctic boundary) is not appeared in thissection, which indicates that this section was in the north of the subarctic boundary.
In the eastern part of the survey area (Fig. 7), a seasonal thermocline lied at the depth of 25 m that isshallower than western area. Temperature at the surface mixing layer shallower than 10-20 m was warmer
than 10℃ in this section. The subarctic water (colder than 4℃) was observed in almost all of this section,
deeper than 50 m depth. A little warm and high salinity water was observed at surface layer around 45ﾟ
30’N in Fig. 7, because the warmer water spread clockwise into this area (sea Fig. 3). 4℃ isotherm,
which is index of the subarctic front, shows a shape of dome and 33.5psu isohaline looks like a bowl
shape with a little cold low-salinity water around45ﾟ30’N in this section. This cold low-salinity water wasprobably cut off from the subarctic domain and moved clockwise into this area. This water made a pair ofwarmer water around 45ﾟ30’N, and clockwise eddy is revealed around 44ﾟN, 164ﾟE in Fig. 3. The
salinity front around 34 psu was not appeared in this section same as the western section, which indicatesthat this survey area was located in the north of the subarctic boundary.

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These figures show that the survey area was almost located in the transition domain, north of thesubarctic boundary. Only two stations in the northwestern part of our survey area were in the subarctic
domain, north of the subarctic front. The water mass was characterized by the subarctic water and themixed water between the subarctic water and the Kuroshio water.

REFERENCES
Favorite, F., Dodimead, A. J. and Nasu, K. 1976. Oceanography of the subarctic Pacific region, 1960-71.
Bull. International North Pacific Fisheries Commission, 33, 187 pp.
Kawai, H. 1969. Statistical estimation of isotherms indicative of the Kuroshio axis, Deep-Sea Res., Suppl.
to 16: 109-115.

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Table 1. Observation summary.
Ship

Instrument

Date

Number ofstations

Hokko-Maru

CTD: BE 9plus

July 24 to August 4, 201020

Table 2. Extraction method from temperature map to determine the position of each water mass.
Target characteristics
Kuroshio Extension Axis

Extraction method
14℃ isotherm at 200 m

Warm-core ringTemperature front at 200 m

Oyashio front

5 ℃ isotherm at 100 m

Oyashio water

Area with T<5 ℃ at 100 m

Cold water

Area with 5℃<T<10 ℃ at 100 m

Warm water

Area with T>10 ℃ at 100 m and T<14 ℃ at 200 m

Subarctic Boundary

Salinity front defined by 34.0 psu

Subarctic Front

Temperature front defined by 4℃

Subarctic Domain

North of Subarctic Front

Transition Domain

Between Subarctic Front and Subarctic Boundary.

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Fig. 1. Station map observed by R/V Hokko-Maru in 24th July to 4th August 2010.

Fig. 2. Temperature-Salinity diagrams using CTD station data observed by R/V Hokko-Maru. Each thinline in this figure denotes a density line of sigma-t.

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Fig. 3. Schematic hydrographic map in the western North Pacific between July 16 and August 15 in 2010 with station map observed by R/V Hokko-Maru andreported to GTSPP.

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Fig. 4. Temperature at 100 m (upper panel) and 200 m depth (lower panel) observed by R/V Hokko-Maru from July 16
to August 15 in 2010.

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Fig. 5. Salinity at 100 m (upper panel) and 200 m depth (lower panel) observed by R/V Hokko-Maru from July 16 toAugust 15 in 2010.

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Fig. 6. Vertical sections from Stn.1 to Stn.11 of temperature (upper panel), salinity (middle panel) and density anomaly(lower panel) observed by R/V Hokko-Maru in July 24-29, 2010．

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Fig. 7. Vertical sections from Stn.12 to Stn.20 of temperature (upper panel), salinity (middle panel) and density
anomaly (lower panel) observed by R/V Hokko-Maru from July 30 to August 4, 2010.

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