Technical Reports of the Ins�tute of Cetacean Research (2021)

pp. 16–32

Technical Report (not peer reviewed)

Results of the Japanese dedicated cetacean sigh�ng surveys in thewestern North Paciﬁc in 2019 and 2020
Taiki Katsumata* and Koji Matsuoka
Institute of Cetacean Research, 4–5 Toyomi-cho, Chuo-ku, Tokyo 104–0055, Japan*Contact e-mail: katsumata@cetacean.jp

ABSTRACT

Vessel-based sigh�ng surveys were conducted in 2019/2020 by Japan to examine the distribu�on and abundance of large whales in the western North Paciﬁc. The research area, set between 25°N–45°N and 128°E–
150°E, was covered between 10 May 2019 and 18 March 2020 involving four seasons: early summer, latesummer, autumn and winter. Previous surveys in autumn and winter were very scarce. The research vessels
Yushin-Maru, Yushin-Maru No. 2, Yushin-Maru No. 3 and Kaiyo-Maru No. 7 were engaged in the current surveys. A total of 9,415.9 n.miles was searched in the research area. The coverage of the planned track lines
on eﬀort was 94% in the early summer, 86% in the late summer, 75% in the autumn and 70% in the wintersurveys. In total, seven large whale species, including blue (7 schools/8 individuals), ﬁn (50/80), sei (44/66),
Brydeʼs (159/202), common minke (39/45), humpback (80/123) and sperm (168/438) whales were sighted
over the en�re research period. Photo-ID images were collected from blue (8 individuals), humpback (26 individuals), and killer (7 individuals) whales. Biopsy skin samples were collected from blue (n=5), ﬁn (n=7), sei(n=5), common minke (n=1), humpback (n=3), and killer (n=1) whales using a Larsen system. Satellite tags
were a�ached on ﬁn (n=6), sei (n=14) and Brydeʼs (n=1) whales. Data collected during these surveys will be
used in studies on abundance, distribu�on, movement and stock structure of several species. This informa�on
is essen�al for appropriate management and conserva�on of cetacean species in the western North Paciﬁc.

INTRODUCTION
Dedicated cetacean sigh�ng surveys in the western North
Paciﬁc have been conducted in the summer season since1995 as a part of the former Japanese Whale Research
Program under Special Permit in the western North
Paciﬁc (JARPN/JARPNII) and the New Scien�ﬁc Whale
Research Program in the western North Paciﬁc (NEWREPNP). Those surveys were based on the survey guidelines
and procedures of the Interna�onal Whaling Commission/Southern Ocean Whale and Ecosystem Research(IWC/SOWER) (Anon, 2008). Based on the collected data
the distribu�on pa�erns of large whales such as blue,
ﬁn, sei, Brydeʼs, common minke, humpback, North Paciﬁc right and sperm whales, and abundance es�mates ofcommon minke, sei and Brydeʼs whales were inves�gatedand reported to the IWC SC (IWC, 2001; 2010; 2016).
The Na�onal Research Ins�tute of Far Seas Fisheries(NRIFSF) has also conducted dedicated sigh�ng surveys for cetaceans in the North Paciﬁc since the 1980s(Buckland et al., 1992; Miyashita et al., 1995., Kanaji
et al., 2012). In 2019 and a�er comple�ng the JARPN/
16

JARPNII and NEWREP-NP, the Government of Japandecided to con�nue the sigh�ng surveys in the North
Paciﬁc (IWC, 2019) based on the ra�onale that the collec�on of sigh�ng data to es�mate abundance and biopsy/
photo-iden�ﬁca�on data to examine stock structure havecontributed, in the past, to the work on management andconserva�on of large whales by the IWC SC (IWC, 2016).
This paper reports the results of the Japanese dedicated sigh�ng surveys conducted during May 2019 to March
2020 involving four seasons: early summer, late summer,
autumn and winter.

SURVEY DESIGN
Research season and area
In 2019/20, in addi�on to the usual summer season
survey, sigh�ng surveys were also conducted in autumn(October–November) and winter (February–March) seasons. The objec�ve of the extra surveys was to provide
basic informa�on on distribu�on and abundance of large
whales from seasons which have been poorly documented. Therefore, surveys in 2019/20 were conductedin four seasons: early summer, late summer, autumn andResults of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020

Figure 1.

The research area and pre-determined track lines in each season. Upper le�: early summer survey (May–
June 2019). Upper right: late summer survey (August–September 2019). Lower le�: autumn survey(October–November 2019). Lower right: winter survey (February–March 2020).

winter. Figure 1 illustrates the research areas covered ineach season.
In early summer (May to June 2019), the research area
was set up between 33°N–45°N and 128°E–150°E (forconvenience, we name the sub-areas as 6E, 7WR, and 7E
from the west).
In late summer (August to September 2019), the research area was set up between 35°N–45°N and 142°E–
147°E.
In the autumn season (October to November 2019),
the research area was set up between 35°N–45°N and
140°E–150°E. This research area was divided into ʻWestern partʼ and ʻEastern part.ʼ
Finally, in the winter season (February to March 2020),
the research area was set up between 25°N–35°N and

138°E–148°E and the research area was divided intoʻWesternʼ and ʻEasternʼ parts.
Research vessels
The surveys in 2019/20 were conducted by the research
vessels Yushin-Maru (YS1), Yushin-Maru No. 2 (YS2),
Yushin-Maru No. 3 (YS3) and Kaiyo-Maru No. 7 (KY7). The
vessels were equipped with a top barrel pla�orm (TOP),
independent observer barrel pla�orm (IOP) and upper
bridge (Figure 2).
Track line design
The survey blocks and pre-determined track lines areshown in Figure 1. The start point of each track line was
decided randomly using the Distance program ver. 7.0
17

Technical Reports of the Ins�tute of Cetacean Research (2021)

Figure 2.

The dedicated sigh�ng vessel that par�cipated in the 2019/20 surveys: Yushin-Maru (YS1) (upper le�),
Yushin-Maru No. 2 (YS2) (upper right), Yushin-Maru No. 3 (YS3) (lower le�), Kaiyo-Maru No. 7 (KY7) (lower
right).

(Thomas et al., 2010), and the number of the lines (width
in the longitude) was decided by the research schedule,
based on the IWC survey guidelines (IWC, 2012).
Sigh�ng procedure and mode
The sigh�ng survey was conducted using (1) Normal
Passing mode (NSP) and (2) Passing with Independent
Observer mode (IO) in order to es�mate abundance withes�mated g(0) for large cetaceans. Both survey modes
followed the protocol endorsed for the SOWER surveys(e.g. Matsuoka et al., 2003).
For NSP mode, there were two primary observers in
the top barrel (TOP) and the captain and helmsman werein the upper bridge. All primary observers conductedsearching for cetaceans by using angle board and scaled
binoculars (7×).
For IO mode, there were two primary observers on
the TOP and the independent observer pla�orm (IOP),
respec�vely. These observers on TOP and IOP also conducted searching for cetaceans by angle board and scaled
binoculars (7×). There was no open communica�on
between the IOP and the TOP. The observers and researchers on the upper bridge communicated to the TOP(or IOP) independently, with the top-men only clarifying
informa�on and without distrac�ng the top-men fromtheir normal search procedure. These primary observers
reported sigh�ng-informa�on to researchers and otherobservers on the upper bridge for data recording. For
18

small cetaceans, sigh�ngs from the TOP and the upper
bridge were recorded.
The survey eﬀort began 60 minutes a�er sunrise andended 60 minutes before sunset, with a maximum of 12hours per day (maximum 06:00–19:00, including 30 minutes for lunch and supper, when surveying in IO mode)
when the weather condi�ons were acceptable for observa�ons: visibility be�er than 2.0 n.miles and wind speed
less than 17 knots in the early and late summer, 21 knots
in the autumn and winter season. The searching speed
was planned to be 10.5 to 11.5 knots with slight adjustment to avoid vibra�on of the vessel.
Distance and angle experiments were conducted in the
middle of the survey period, using a buoy with a reﬂector
that resembles a blow. The experiment to evaluate measurement error was conducted late in the survey following
the protocol of the IWC/SOWER and IWC-POWER surveys(IWC, 2012). The Es�mated Angle and Distance Training
Exercise were also conducted early in the surveys. During
the exercise, the observers familiarized themselves with
distance es�mates from the TOP and Upper Bridge.
Experiments
For each survey, when large cetaceans such as blueand humpback whales were encountered, photo-ID images were obtained using Canon EOS 7D Mark II (with
100–400 mm lens) from the bow or upper deck. Further,biopsy skin sampling using the Larsen sampling system

Results of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020

(Larsen, 1998) was conducted in early summer, late summer and autumn season survey when blue, ﬁn, sei andhumpback whales were sighted. In the early summer,
autumn and winter season surveys, a satellite tagging experiment using LK-ARTS was also conducted when ﬁn, sei
and common minke whales were sighted. These data collected in diﬀerent seasons will assist the interpreta�on ofstock structure hypotheses and abundance es�ma�ons
for these species.

RESULTS OF THE SURVEY
Narra�ve of the surveys
Early summer 2019
The YS1 and YS3 departed Shimonoseki, Yamaguchi prefecture, Japan on 10 May, and the YS2 departed Shiogama, Miyagi prefecture, Japan, on 11 May. The YS1 started
the survey in sub-area 7WR on 13 May and completed
it on 4 June. The YS2 started the survey in sub-area 6E
on 13 May and completed it on 14 June. The YS3 started
the survey in sub-area 7E on 14 May and completed it
on 2 June. Each vessel surveyed a pre-determined trackline from north to south of each stratum, taking into account the seasonal migra�on of baleen whales to avoid
double coun�ng (Figure 1). The YS1 and YS3 arrived in
Shimonoseki on 8 June, and the YS2 arrived in Shiogama
on 26 June.
Late summer 2019
The KY7 departed Hachinohe, Aomori prefecture, Japan,

on 16 August. The vessel started the survey in sub-area
7WR on 19 August and completed it on 21 September.
The vessel arrived in Misaki, Kanagawa prefecture, Japan,
on 26 September. The vessel surveyed a pre-determinedtrack line from north to south (Figure 1).
Autumn in 2019
The YS3 departed Daiba, Tokyo, Japan, and started thesurvey in the western part of the research area on 8 October. The KY7 departed Misaki on 10 October and started
the survey in the eastern part of the research area on 16
October. The YS3 completed the survey on 10 November
and arrived in Shimonoseki on 15 November. The KY7
completed the survey on 17 November and arrived in
Hachinohe on 20 November. Both vessels surveyed apre-determined track line from south to north in eachstratum (Figure 1).
Winter 2020
The KY7 departed Shimizu, Shizuoka prefecture, Japan,
on 6 February and started the survey in the western partof the research area on 11 February. The YS3 departed
Shimonoseki on 12 February and started the survey in theeastern part of the research area on 16 February. The KY7
and YS3 completed the survey on 13 March and arrived
in Shiogama on 16 March and Shimonoseki on 17 March,
respec�vely. Both vessels surveyed a pre-determinedtrack line from south to north in each stratum (Figure 1).
The Es�mated Angle and Distance Experiments wereTable 1
Summary of the searching eﬀort by each season and area.
Planned Searching Searching Searching Coveragecruise track eﬀort NSP eﬀort IO eﬀort Total of eﬀort(%)(n.miles) (n.miles) (n.miles) (n.miles)

Research
area

VesselResearch period

6E
7WR
7E

YS2
YS1
YS3

2019/5/13–6/14
2019/5/13–6/4
2019/5/14–6/2

2,021.1
1,177.2
871.8

959.4
566.5
397.2

932.4
580.1
408.2

1,891.8
1,146.6
805.4

94
97
92

Sub total—

2019/5/13–6/14

4,070.1

1,923.2

1,920.7

3,843.8

94

Late summer (Aug.–Sep.)

7WR

KY7

2019/8/19–9/21

1,193.0

511.9

518.9

1,030.7

86

Autumn (Oct.–Nov.)

Western
Eastern

YS3
KY7

2019/10/8–11/10
2019/10/16–11/17

1,597.8
1,611.0

635.9
578.1

647.4
557.8

1,283.3
1,135.8

80
71

Sub total—

2019/10/8–11/17

3,208.8

1,213.9

1,205.1

2,419.1

75

Western
Eastern

KY7
YS3

2020/2/11–3/13
2020/2/16–3/13

1,505.1
1,522.9

450.7
663.7

414.3
593.5

865.0
1,257.3

58
83

Sub total—

2020/2/11–3/13

3,028.0

1,114.4

1,007.8

2,122.2

70

—

—

—

11,499.9

4,763.4

4,652.5

9,415.982

Season

Early summer (May–Jun.)

Winter (Feb.–Mar.)
Total

19

Technical Reports of the Ins�tute of Cetacean Research (2021)
Table 2a
Numbers of sigh�ngs of large whales in early summer (May–June), by each sub-area.
Season

Early summer(May–Jun.)

Species

6E

7WR

7E

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Blue whale

0

0

0

0

4

5

4

5

Fin whale

12

21

5

7

6

9

23

37

Sei whale

0

0

1

2

7

11

8

13

Bryde's whale

0

0

16

19

32

42

48

61

Like Bryde's

0

0

0

0

4

4

4

4

Common minke whale

37

43

1

1

0

0

38

44

Like minke

0

0

1

1

0

0

1

1

Humpback whale

1

1

21

29

15

21

37

51

Sperm whale

0

0

66

165

21

63

87

228

Uniden�ﬁed large baleen whale

0

0

1

1

5

5

6

6

Uniden�ﬁed large cetacean

1

1

1

1

0

0

2

2

Table 2b
Numbers of sigh�ngs of small cetaceans in early summer (May–June), by each sub-area.
Season

Early summer(May–Jun.)

Species

6E

7E

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Cuvier's beaked whale

1

4

0

0

0

0

1

4

Uniden�ﬁed Ziphiidae

22

39

6

13

10

20

38

72

Uniden�ﬁed Mesoplodon

2

4

0

0

2

2

4

6

Common dolphin

1

200

3

48

9

435

13

683

Risso's dolphin

5

56

17

143

2

13

24

212

Paciﬁc white-sided dolphin

8

421

2

170

12

316

22

907

Dalli type Dall's porpoise

1

4

2

10

1

5

4

19

Truei type Dall's porpoise

1

1

0

0

2

8

3

9

Unid. type Dall's porpoise

9

30

4

12

5

51

18

93

conducted on 27 May by YS1 and YS3, on 2 June by YS2
and on 5 September by KY7. In winter, the Es�matedAngle and Distance Experiments were conducted again
on 7 March by KY7 and YS3 because there was a changeof observers. The results of this experiment will be usedin the calcula�on of abundance es�mates.
Research eﬀort in each season and research area
A summary of the searching eﬀort and coverage in eachseason and research area is shown in Table 1. A total of
9,415.9 n.miles (17,438.2 km) were searched in the whole
research area and during all seasons. In early summer, thetotal searching eﬀort was 3,843.8 n.miles (7,118.7 km),and the coverage exceeded 90% due to con�nued stable
weather condi�ons. In late summer, the searching eﬀort
was 1,030.7 n.miles (1,908.9 km), and the coverage was20

7WR

86.4%. The percentage dropped slightly in late summer because the survey was interrupted three �mes in September
to avoid typhoons. In the autumn season, the total searching eﬀort was 2,419.1 n.miles (4,480.2 km), and the coverage was rela�vely low (75.4%) because the available survey
hours of the day were only about eight hours due to �mesof the sunrise and sunset, and also because typhoons weres�ll ac�ve around Japan in October. In the winter season,
the total searching eﬀort was 2,122.2 n.miles (3,930.3 km),and the coverage was 70.1%. In the western part, the coverage was low (57.5%) because �me was lost on a number ofoccasions in avoiding stormy weather.
Sigh�ngs
Sigh�ngs were summarized by each season (Tables 2a to5b). The sigh�ng loca�on of each species in each season

Results of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020

Figure 3.

The sigh�ng loca�ons of large and small cetaceans during the early summer (May–June 2019) and informa�on on SST in that season (original data of SST: Ocean color web, from h�ps://oceancolor.gsfc.nasa.gov/).

is shown in Figures 3, 4, 5 and 6, together with sea surface
temperature (SST).

Early summer (May–June)
Blue whale
Four schools (ﬁve individuals including a mother and21

Technical Reports of the Ins�tute of Cetacean Research (2021)

calf pair) were sighted between 38°20ʹN, 149°27ʹE and38°06ʹN, 148°46ʹE in sub-area 7E (Table 2a, Figure 3). One
blue whale formed a mixed school with a ﬁn whale. The
range of SST at the sigh�ng posi�ons was 14.5–15.2°C. All
ﬁve individuals were photographed, and biopsy samples
were collected from four individuals.
Fin whale
Fin whales were sighted in each research area (Table 2a,
Figure 3). In sub-area 6E, 12 schools (21 individuals including 2 mother and calf pairs) were sighted. Observed
mean school size was 1.75. The range of SST in the sighting posi�ons was 10.0–16.3°C. In sub-areas 7WR and 7E,
11 schools (16 individuals) were sighted. Observed meanschool size was 1.45. The range of SST at the sigh�ng posi�ons was 8.4–20.5°C.
Sei whale
Sei whales were sighted in sub-areas 7WR and 7E (Table
2a, Figure 3). A total of eight schools (13 individuals including 2 mother and calf pairs) were sighted. Observed
mean school of size was 1.63. The range of SST at thesigh�ng posi�ons was 14.1–16.4°C.
Brydeʼs whale
A total of 48 schools (61 individuals including 10 motherand calf pairs) were sighted in sub-areas 7WR and 7E (Table
2a, Figure 3). Because the survey was conducted at the beginning of the migra�on season of this species, they were
only sighted in the southern part of sub-areas 7WR and 7E.
The observed mean school size was 1.27. The range of the
SST at the sigh�ng posi�ons was 15.6–24.2°C.
Common minke whale
This species was the most frequently sighted species in
sub-area 6E (37 schools and 43 individuals including 2
mother and calf pairs) (Table 2a, Figure 3). The range of
SST at the sigh�ng posi�ons was 10.1–21.9°C, and theobserved mean school size was 1.16. In sub-area 7WR,
one school (one individual) was sighted. The SST at thesigh�ng posi�on was 16.5°C and the es�mated bodylength was 7.8 m. A picture of a common minke whale isshown in Figure 7.
Humpback whale
Humpback whales were sighted frequently in sub-areas
7WR and 7E (36 schools and 50 individuals) (Table 2a,
Figure 3). No mother and calf pair was sighted. They weremainly sighted in the northern part of sub-areas 7WR and7E. Observed mean school size was 1.38. The range of
SST at the sigh�ng posi�ons was 8.6–18.8°C. In sub-area
6E, one individual was sighted. The SST at the sigh�ng
posi�on was 10.4°C and the es�mated body length was
12.2 m. This individual was photographed and a biopsy
sample was obtained.
22

Sperm whale
A total of 87 schools (228 individuals) of this species
were sighted (Table 2a, Figure 3) in the North Paciﬁc sector. A high-density area of sperm whales was observedin the western part of sub-area 7WR. This high-density
area was formed across the Japan Trench. The observed
mean school size was 2.62. Because the opportunity toapproach the schools was limited, there was li�le informa�on on body length and calves. The range of SST at thesigh�ng posi�ons was 6.8–24.1°C.
Small cetaceans
The species sighted are shown in Table 2b and their distribu�on in Figure 3. In this season, one species was iden�ﬁed in the family Ziphiidae, three species were iden�ﬁedin the family Delphinidae and one species was iden�ﬁedin the family Phocoenidae. The most common species
sighted were Risso's dolphin (24/212), followed by Paciﬁcwhite-sided dolphin (22/907). There were many sigh�ngs
of the family Ziphiidae, but it was diﬃcult to iden�fy the
species because of their elusive behavior.
Late summer (August–September)Blue whale
One individual of es�mated body length of 24.5 m. wassighted at 40°54ʹN, 145°13ʹE (Table 3a, Figure 4). The
SST in the sigh�ng posi�on was 22.8°C This individual
was photographed and a biopsy sample was obtained(Figure 8).
Fin whale
Two schools (two individuals) were sighted north of 40°N
(Table 3a, Figure 4). The es�mated body lengths were
20.8 m and 22.8 m. The range of SST at the sigh�ng posi�ons was 22.5–22.8°C.
Sei whale
This species was not sighted in the research area. However, one individual of 14.2 m in body length was sighted
during the transit survey between Hachinohe and thestar�ng point of the research area. The SST at the sigh�ng
posi�on was 21.5°C.
Brydeʼs whale
A total of 67 schools (92 individuals include 8 mother andcalf pairs) were sighted. In comparison with the distribu�on of Brydeʼs whales in early summer, these were widely distributed except the southern part of the researcharea (Table 3a, Figure 4). In general, Brydeʼs whales were
widely distributed in summer (from July to September)in the western North Paciﬁc, north of 35°N, based on theprevious dedicated sigh�ng surveys (Shimada, 2004, Pastene et al., 2009, Hakamada et al., 2017). The observed
mean school size was 1.37. The range of the SST at theResults of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020
Table 3a
Numbers of sigh�ngs of large whales in late summer (August–
September).
SeasonLate summer(Aug.–Sep.)

Species

7WR
Sch. Ind.

Blue whale

1

1

Fin whale2

2

Sei whale

1

1

Brydeʼs whale

67

92

Like Brydeʼs55Like Sei/Brydeʼs

11

Sperm whale

30

91

Uniden�ﬁed large baleen whale

4

5

Uniden�ﬁed large cetacean

11Table 3b
Numbers of sigh�ngs of small cetaceans in late summer(August–September).
SeasonLate summer(Aug.–Sep.)

Species

7WR
Sch. Ind.

Bairdʼs beaked whale

1

2

Cuvierʼs beaked whale

1

2

Uniden�ﬁed Mesoplodon spp.

2

10

Uniden�ﬁed Ziphiidae

1226Common dolphin

14

961

Northern form short-ﬁnned pilot
whale

1

20

Rissoʼs dolphin

237Melon-headed whale

1

96

Striped dolphin

8278sigh�ng posi�ons was 22.0–27.0°C.
Common minke whale
This species was not sighted in the late summer season.
Humpback whale
Humpback whales were not sighted in the research area.
It was considered that humpback whales had migrated to
the northern area.
Sperm whale
A total of 30 schools (91 individuals) of this species weresighted in the research area (Table 3a, Figure 4). The
observed mean school size was 3.09. The range of thees�mated body length was 9.1–12.2 m. The range of SST
at the sigh�ng posi�ons was 6.8–24.1°C.
Small cetaceans
The species sighted are shown in Table 3b and their distri-bu�on in Figure 4. In this season, two species were iden�ﬁed in the family Ziphiidae and ﬁve species were iden�ﬁed in the family Delphinidae. The most common species
sighted were common dolphins (14/961), followed bystriped dolphins (8/278). In comparison with the resultsof the early summer (May–June), the distribu�on of thecommon, Rissoʼs and striped dolphins extended northof 40°N, and the Paciﬁc white-sided dolphin, which was
distributed around 40°N in the early summer season, was
not sighted in this season. The SST map shows a temperature around 24°C, even near 40°N (Figure 4), sugges�ng
that the distribu�on of these dolphins is shi�ing northward as the water temperature rises.
Autumn (October–November)Blue whale
Two schools (two individuals) with body lengths of 24.3 m
and 25.3 m were sighted in the western part (Table 4a,
Figure 5). The SST at the sigh�ng posi�ons was 16.7°C
and 17.2°C, respec�vely. These two individuals were
photographed.
Fin whale
A total of 22 schools (38 individuals) were sighted in the
research area. In this season, ﬁn whales were mainly
sighted north of 40°N (Table 4a, Figure 5). The observed
mean school size was 1.73. A school of three ﬁn whales
sighted at 42°23ʹN, 145°56ʹE on 13 November was chasedby a solitary adult male killer whale (Figure 9).
Sei whale
A total of 28 schools (38 individuals) were sighted northof 40°N in the research area. Sei whales were concentrated in the northern coastal part of the research area
(Table 4a, Figure 5). The observed mean school size was
1.36. The range of the SST at the sigh�ng posi�ons was
9.1–18.1°C.
Brydeʼs whale
A total of 37 schools (42 individuals including 1 motherand calf pair) were sighted. In this season, Brydeʼs whales
were mainly sighted in the western part of the researcharea (Table 4a, Figure 5). The observed mean school size
was 1.14. Range of the SST in the sigh�ng posi�ons was
16.8–24.3°C.
Common minke whale
One school (one individual) of body length es�mated tobe 7.2 m was sighted in the most northern part of thewestern part of the research area (Table 4a, Figure 5). The
SST at the sigh�ng posi�on was 11.3°C.
Humpback whale
A total of 26 schools (42 individuals) of this species was
sighted. Sigh�ngs were concentrated between 41°N and23

Technical Reports of the Ins�tute of Cetacean Research (2021)

Figure 4.

The sigh�ng loca�ons of large and small cetaceans during the late summer (August–September 2019) andinforma�on on SST in that season (original data of SST: Ocean color web, from h�ps://oceancolor.gsfc.
nasa.gov/).

42°N in the research area (Table 4a, Figure 5). The observed mean school size was 1.62. The range of SST at thesigh�ng posi�on was 8.8–18.8°C. More than half of the24schools (65%) were sighted in waters with SST of 11°C.
Sperm whale
A total of 41 schools (107 individuals) of this species wereResults of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020
Table 4a
Numbers of sigh�ngs of large whales in autumn (October–November) by each area.
Western part

Eastern part

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Blue whale

2

2

0

0

2

2

Fin whale

10

15

12

23

22

38

Like ﬁn

0

0

1

2

1

2

Sei whale

10

11

18

27

28

38

Brydeʼs whale

35

39

2

3

37

42

Common minke whale

0

0

1

1

1

1

Humpback whale

16

27

10

15

26

42

Sperm whale

26

52

15

55

41

107

Uniden�ﬁed large baleen whale

8

8

1

1

9

9

SeasonAutumn(Oct.–Nov.)

Species

Total

Table 4b
Numbers of sigh�ngs of small cetaceans in autumn (October–November), by each area.
Western part

Eastern part

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Bairdʼs beaked whale

3

29

0

0

3

29

Uniden�ﬁed Ziphiidae

9

23

4

8

13

31

Common dolphin

2

70

11

416

13

486

Southern form short-ﬁnned pilot whale

1

4

0

0

1

4

Rissoʼs dolphin

2

4

0

0

2

4

Paciﬁc white-sided dolphin

0

0

1

5

1

5

Killer whale

0

0

3

3

3

3

Spo�ed dolphin

0

0

3

75

3

75

Striped dolphin

1

100

19

537

20

637

Harbour porpoise

1

4

0

0

1

4

Dalli type Dallʼs porpoise

1

15

0

0

1

15

Truei type Dallʼs porpoise

2

12

1

25

3

37

SeasonAutumn(Oct.–Nov.)

Speciessighted (Table 4a, Figure 5). Sigh�ngs were concentrated
south of 38°N in the research area. The observed meanschool size was 2.61. The range of SST at the sigh�ng posi�ons was 11.9–26.7°C.
Small cetaceans
The species sighted are shown in Table 4b and theirdistribu�on in Figure 5. In this season, one species wasiden�ﬁed in the family Ziphiidae, and seven species wereiden�ﬁed in the family Delphinidae and two species wereiden�ﬁed in the family Phocoenidae. The most common
species sighted were striped dolphins (20/637), followedby common dolphins (13/486). Compared with the latesummer (August–September) results, the distribu�on of
the common and striped dolphins shi�ed to the south
and were mainly sighted between 37°N–39°N. The SSTs

Total

are decreasing from the north during this season, sugges�ng that the distribu�on of these dolphins is moving
south as water temperature changes.
Winter (February–March)
Blue whale
This species was not sighted in the winter season.
Fin whale
Three schools (three individuals) were sighted east of
147°E (Table 5a, Figure 6). The range of SST at the sigh�ng
posi�ons was 17.3–23.4°C. All four groups were solitary,
including one group sighted at 27°47ʹN, 138°07ʹE during
the transit survey.
Sei whale
A total of 7 schools (14 individuals including 3 mother and25

Technical Reports of the Ins�tute of Cetacean Research (2021)

Figure 5.

The sigh�ng loca�ons of large and small cetaceans during the autumn (October–November 2019) andinforma�on on SST in that season (original data of SST: Ocean color web, from h�ps://oceancolor.gsfc.
nasa.gov/).

calf pairs) were sighted in the eastern part of the researcharea (Table 5a, Figure 6). The range of SST at the sigh�ng
posi�ons was 17.4–21.9°C. Sigh�ngs occurred only in theeastern part, and the ra�o of mother and calf pairs (3/7)
was higher than in the other seasons. These data would
26

be useful to iden�fy the breeding ground of sei whales in
the North Paciﬁc.
Brydeʼs whale
A total of seven schools (seven individuals) were sighted
in the research area (Table 5a, Figure 6). The range ofResults of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020
Table 5a
Numbers of sigh�ngs of large whales in winter (February–March).
Western part

Eastern part

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Fin whale

0

0

3

3

3

3

Sei whale

0

0

7

14

7

14

Like sei

0

0

1

1

1

1

Bryde's whale

4

4

3

3

7

7

Humpback whale

13

23

4

7

17

30

Sperm whale

2

4

8

8

10

12

Uniden�ﬁed large baleen whale

1

1

0

0

1

1

SeasonWinter
(Feb.–Mar.)Species

Total

Table 5b
Numbers of sigh�ngs of small cetaceans in winter (February–March).
Western part

Eastern part

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Uniden�ﬁed Ziphiidae

6

10

1

3

7

13

Common dolphin

1

40

0

0

1

40

Southern form short-ﬁnned pilot whale

2

106

0

0

2

106

Risso's dolphin

3

20

1

4

4

24

Killer whale

0

0

1

10

1

10

Spo�ed dolphin

1

22

0

0

1

22

Striped dolphin

1

35

3

270

4

305

Rough toothed dolphin

1

4

0

0

1

4

SeasonWinter
(Feb.–Mar.)Species

SST at the sigh�ng posi�ons was 17.2–22.6°C. All eightgroups were solitary. One group was sighted at 26°35ʹN,
144°52ʹE during the transit survey.
Common minke whale
This species was not sighted in the winter season.
Humpback whale
A total of 17 schools (30 individuals, including 3 motherand calf pairs) were sighted (Table 5a, Figure 6). Eight ofall schools (13 individuals) were sighted in the waters
around 27°N, 142°E on 23 February. This area was reported as breeding ground of humpback whales in thewestern North Paciﬁc (Darling and Mori, 1993). The rangeof SST at the sigh�ng posi�ons was 17.4–23.6°C. The observed mean school size was 1.76.
Sperm whale
A total of 10 schools (12 individuals) were sighted (Table
5a, Figure 6). The range of SST at the sigh�ng posi�ons
was 17.9–22.9°C and the observed mean school size was
1.20. The school size was compara�vely smaller than in
the other seasons. When the KY7 entered Suruga Bay
on 27 and 28 February in order to shelter from stormy

Totalweather, the vessel encountered 11 schools (52 individuals) of sperm whales (secondary sigh�ngs). In Suruga Bay,
sperm whales were distributed in waters at the center ofa submarine canyon (Figure 6). The range of SST at thesigh�ng posi�ons in Suruga Bay was 17.0–18.2°C. The
observed mean school size was 4.72.
Small cetaceans
The species sighted are shown in Table 5b and their distribu�on in Figure 6. No species was iden�ﬁed in the family
Ziphiidae because of their elusive behavior. Seven species
were iden�ﬁed in the family Delphinidae. Striped (4/305)
and Rissoʼs (4/24) dolphins were the most commonlysighted dolphin species.
Duplicate sigh�ngs
Duplicate sigh�ng data will be used for analysis of g(0) to
accoun� for percep�on bias. A total of 594 re-sigh�ngs
were recorded during IO mode throughout the wholeseason involving several species.

27Technical Reports of the Ins�tute of Cetacean Research (2021)

Figure 6.

The sigh�ng loca�ons of large and small cetaceans during the winter (February–March 2020) and informa�on on SST in that season (original data of SST: Ocean color web, from h�ps://oceancolor.gsfc.nasa.gov/).
Lower le�: the sigh�ng loca�ons of sperm whales in Suruga Bay (secondary sigh�ngs).

Experiments
Photo-ID
Photo-IDs will be used for inves�ga�on of movement,
28

stock structure and site ﬁdelity of cetaceans, and toes�mate abundance using the mark-recapture method.
Photographs were taken of blue (n=8), humpback (n=26)

Results of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020

Figure 7.

A common minke whale surfacing. The white ﬂipper band can be seen below the sea surface.
Table 6
Number of individuals photographed, by each season and sub-area.

Species

Early summer (May–Jun.)

Late summer(Aug.–Sep.)

Autumn (Oct.–Nov.)

Winter (Feb.–Mar.)

Total

6E

7WR

7E

7WR

Western part Eastern part Western part Eastern part

Blue whale
Humpback whale
Killer whale

0
1
0

0
0
2

5
4
5

1
0
0

2
5
0

0
2
0

0
6
0

0
8
0

8
26
7

Total

1

2

14

1

7

2

6

8

41

sei (n=5), common minke (n=1), humpback (n=3) andkiller (n=1) whales (Table 7). All samples were stored at
the ICR laboratory.
Satellite tagging
Tracking data obtained from satellite tags will contributeto the elucida�on of the movement of whales in eachseason and the �ming of the start of migra�on between
low la�tude breeding areas and high la�tude feedingareas. Satellite tags were successfully a�ached on ﬁn(n=6), sei (n=14) and Brydeʼs (n=1) whales (Table 8).
Figure 8.

Blow and body of a blue whale.

and killer (n=7) whales throughout the whole season(Table 6). Some small cetaceans were also photographed.
All photographs were stored in the Ins�tute of Cetacean
Research (ICR) catalogues.
Biopsy sampling
These samples will be used in gene�c analyses on stock
structure and studies to evaluate the u�lity of non-lethal
techniques for whale biological research. A total of 22
biopsy samples were collected from blue (n=5), ﬁn (n=7),

HIGHLIGHTS OF THE SURVEY
The sigh�ng surveys conducted in 2019/20 were completed successfully. They provided unique data obtained
not only in summer, but also in autumn and winter seasons for which informa�on on cetacean distribu�on andabundance have been very scarce. Some main characteris�cs of the surveys are summarized below.
A large number of common minke and ﬁn whales weresighted in May–June in the southern part of the Sea ofJapan. These data are unique and will be analyzed in combina�on with available sigh�ng data from the northern29Technical Reports of the Ins�tute of Cetacean Research (2021)

Figure 9.

One adult male killer whale chasing a school of three ﬁn whales. Clipped from a video taken from a distance.

Table 7
Number of biopsy samples collected, by each season and research area. The biopsy sampling was conducted in early summer (allareas), late summer (7WR) and autumn (eastern part).
Early summer (May–Jun.)

Species

Late summer (Aug.–Sep.)

Autumn (Oct.–Nov.)

Total

6E

7WR

7E

7WR

Eastern part

Blue whale
Fin whale
Sei whale
Common minke whale
Humpback whale
Killer whale

0
0
0
1
1
0

0
1
0
0
0
1

4
3
2
0
2
0

1
0
0
0
0
0

0
3
3
0
0
0

5
7
5
1
3
1

Total

2

2

11

1

6

22

Table 8
Number of individuals a�ached with satellite tags, by each season and sub-area. The tagging was conducted in early summer (6E and7E), autumn (whole area) and winter (eastern part).
Species

Early summer (May–Jun.)

Autumn (Oct.–Nov.)

Total

6E

7E

Western part

Eastern part

Eastern part

Fin whale
Sei whale
Brydeʼs whale

1
0
0

1
2
0

3
4
0

1
3
0

0
5
1

6
14
1

Total

1

4

7

4

6

22

part of the Sea of Japan obtained in 2018. The purpose
will be to es�mate common minke whale abundance in
the Sea of Japan, an area where recent informa�on onabundance is scarce.
A large number of Bryde's, humpback and sperm
whales were sighted in May–June in the northern part of
the Paciﬁc side of Japan. No common minke whales weresighted during this season in this area which suggests thatmost common minke whales are likely to have already
moved north into the Russian EEZ.
The survey in August–September covered the northern
30

Winter (Feb.–Mar.)part of the Paciﬁc side of Japan, and provided importantsummer sigh�ng data for Brydeʼs whales, which will be
used for the abundance es�ma�on of this species. It wasalso conﬁrmed that blue, ﬁn and sperm whales were also
distributed in this area, though in small numbers.
A large number of sei and ﬁn whales were sighted in
October–November in the coastal area. This area had
never been surveyed in this season. These species weresighted north of la�tude 40°N. A large number of Bryde's
whales and a small number of blue whales were sighted
south of 40°N in this season. In addi�on, it was conﬁrmed

Results of the Japanese dedicated cetacean sighting surveys in the western North Pacific in 2019 and 2020

Figure 10.

Breaching of a Bairdʼs beaked whale. The long,stout beak and the prominent melon-shaped headiden�fy this species.

that sperm whales are s�ll distributed south of 38°N inthis season.
During the February–March survey in the waters
around Ogasawara Islands, several ﬁn and sei whales
were sighted possibly before their migra�on to the north.
Of par�cular value are the satellite tags a�ached onsome of these whales. In addi�on, Bryde's whales andhumpback whales were sighted possibly before theirmigra�on to the north. Several schools of sperm whales
were sighted in the central part of Suruga Bay in watersof 1,000 m depth.
As with the previous surveys, the 2019/20 surveys collected data on small cetaceans in the same way as large
whales. The analyses of these data will provide valuable
informa�on on the distribu�on and abundance of small
cetaceans in diﬀerent seasons.

ACKNOWLEDGEMENTS
The authors acknowledge the Government of Japan for
its assistance in providing the research permits and funding for these cruises. We also thank the captains Hidenori Kasai, Chikamasa Okoshi, Nobuo Abe, Yasuaki Sasaki,
Ryoji Kita and their oﬃcers and crew of the Yushin-Maru,
Yushin-Maru No. 2, Yushin-Maru No. 3 and Kaiyo-Maru
No. 7 for their hard work and dedica�on that led to thesuccessful execu�on of these surveys. We express our
deep gra�tude to Takashi Hakamada and Megumi Takahashi (ICR) for their assistance in the survey design andlogis�cal support. We thank Yoshihiro Fujise and the staﬀ
of the ICR, Kyodo Senpaku Co. Ltd. and Kaiyo Engineering
Co. Ltd., for their assistance and support for these cruises.
We thank Luis A. Pastene (ICR) for his assistance in preparing this report.

REFERENCES

Researchers. h�ps://iwc.int/private/downloads/-m4RVc06JhB
Vw3ymd3oPcw/Guide%20%20for%20Researchers%202008-09.
pdf.
Buckland, S.T., Ca�anach, K.L. and Miyashita, T. 1992. Minke
whale abundance in the northwest Paciﬁc and the Okhotsk
Sea, es�mated from 1989 and 1990 sigh�ng surveys. Rep. int.
Whal. Commn 42: 387–392.
Darling, J.D. and Mori, K. 1993. Recent observa�ons of humpback whales (Megaptera novaeangliae) in Japanese watersoﬀ Ogasawara and Okinawa. Can. J. Zool. 71: 325–333.
Hakamada, T., Takahashi, M., Matsuoka, K. and Miyashita, T.
2017. Abundance es�mate for western North Paciﬁc Brydeʼswhale by sub-areas based on IWC-POWER and JARPNII
sigh�ng surveys. Paper SC/M17/RMP2 presented to theWorkshop on the Implementa�on Review of western North
Paciﬁc Brydeʼs whales, March 2017 (unpublished). 11 pp.
[Available from the IWC Secretariat].
Interna�onal Whaling Commission. 2001. Report of theWorkshop to Review the Japanese Whale Research Program
under special permit for North Paciﬁc minke whales (JARPN).
J. Cetacean Res. Manage. (Suppl.) 3: 377–413.
Interna�onal Whaling Commission. 2010. The Report of theExpert Workshop to review the ongoing JARPNII Programme.
J. Cetacean Res. Manage. (Suppl.) 11: 405–450.
Interna�onal Whaling Commission. 2012. Requirements andguidelines for conduc�ng surveys and analyzing data within
the revised management scheme. J. Cetacean Res. Manage.
(Suppl.) 13: 509–517.
Interna�onal Whaling Commission. 2016. Report of the Expert
Panel of the ﬁnal review on the western North PaciﬁcJapanese Special Permit programme (JARPNII). Paper
SC/66b/REP/06 presented to the IWC Scien�ﬁc Commi�ee,June 2016 (unpublished). 96 pp. [Available from the IWC
Secretariat].
Interna�onal Whaling Commission. 2019. Report of the
Scien�ﬁc Commi�ee, Annex Q. J. Cetacean Res. Manage.
(Suppl.) 20: 394–412.
Kanaji, Y., Iwasaki, T., Kishiro, T. and Miyashita, T. 2012. Cruise
report of the sigh�ng and satellite tagging survey for common minke whales in the sub-area 7 in 2011. Paper SC/64/O9
presented to the IWC Scien�ﬁc Commi�ee, June 2012 (unpublished). 10 pp. [Available from the IWC Secretariat].
Larsen, F. 1998. Development of a biopsy system primarily foruse on large cetaceans. Paper SC/50/O15 presented to the
IWC Scien�ﬁc Commi�ee, May 1998 (unpublished). 8 pp.
[Available from the IWC Secretariat].
Matsuoka, K., Ensor, P., Hakamada, T., Shimada, H., Nishiwaki,S., Kasamatsu, F. and Kato, H. 2003. Overview of minke
whale sigh�ngs surveys conducted on IWC/IDCR and SOWER
Antarc�c cruises from 1978/79 to 2000/01. J. Cetacean Res.
Manage. 5 (2): 173–201.
Miyashita, T., Kato, H. and Kasuya, T. (eds.) 1995. Worldwide
Map of Cetacean Distribution based on Japanese Sighting

Anon. 2008. IWC SOWER Cruise 2008/09, Informa�on for31

Technical Reports of the Ins�tute of Cetacean Research (2021)
Data (Volume 1). Na�onal Research Ins�tute of Far Seas
Fisheries, Shimizu, Shizuoka. 140 pp.
Pastene, L.A., Hatanaka, H., Fujise, Y., Kanda, N., Murase, H.,
Tamura, T., Miyashita, T. and Kato, H. 2009. The Japanese
Whale Research Program under Special Permit in the western North Paciﬁc Phase-II (JARPNII): origin, objec�ves andresearch progress made in the period 2002–2007, including
scien�ﬁc considera�ons for the next research period. Paper
SC/J09/JR1 (Rev 1) presented to the IWC Scien�ﬁc Commi�ee
Expert Workshop to review the JARPNII Programme,
January 2009 (unpublished). 73 pp. [Available from the IWC

32

Secretariat].
Shimada, H. 2004. Abundance es�mate of the western North
Paciﬁc stock of Brydeʼs whales using sigh�ng data from 1998
to 2002. Paper SC/56/PFI6 presented to the IWC Scien�ﬁcCommi�ee, June 2004 (unpublished). 8 pp. [Available fromthe IWC Secretariat].
Thomas, L., Buckland, S.T., Rexstad, E.A., Laake, J.L., Strindberg,S., Hedley, S.L., Bishop, J.R.B., Marques, T.A. and Burnham,
K.P. 2010. Distance so�ware: design and analysis of distancesampling surveys for es�ma�ng popula�on size. J. Appl. Ecol.
47 (1): 5–14.