Technical Reports of the Ins�tute of Cetacean Research (2023)

pp. 34–46

Technical report (not peer reviewed)

Report and highlights of the Japanese dedicated sigh�ng surveys
in the North Paciﬁc in 2022
Yujin Kim*, Taiki Katsumata, Tatsuya Isoda and Koji Matsuoka
Institute of Cetacean Research, 4–5 Toyomi-cho, Chuo-ku, Tokyo 104–0055, Japan*Contact e-mail: kim@cetacean.jp

ABSTRACTThis paper presents the results of vessel-based sigh�ng surveys conducted in 2022 by the Ins�tute of Cetacean
Research in the North Paciﬁc. The research area was set between 35°N–46°N and 140°E–175°W. The surveys
were conducted between 7 April and 10 November involving three seasons: spring, late summer and autumn.
The spring and late summer surveys were conducted to examine the distribu�on and abundance of whales,
and the autumn survey was conducted to inves�gate the migra�on of sei whales using satellite tags. The research vessels Yushin-Maru, Yushin-Maru No. 2 and Kaiyo-Maru No. 7 were engaged in the surveys. A totalof 8,340.9 n.miles was searched in the research area. Coverage of the searching eﬀorts on the planned cruise
track line was 81.1%. In total, eight large whale species, including blue (3 schools/3 individuals), ﬁn (105/165),sei (32/44), Brydeʼs (248/274), common minke (151/172), humpback (52/62), North Paciﬁc right (1/1) andsperm (198/375) whales were sighted during the whole research. Photo-ID images were collected from blue(n=2), humpback (n=7), North Paciﬁc right (n=1) and killer (n=2) whales. Biopsy skin samples using a Larsen
system were collected from ﬁn (n=1), sei (n=16), Brydeʼs (n=6), common minke (n=6) and North Paciﬁc right(n=1) whales. Satellite tags were a�ached on ﬁn (n=1), sei (n=16), Brydeʼs (n=5) and common minke (n=1)
whales. Data collected during these surveys will be used in studies on abundance, distribu�on, movement andstock structure of several whale species.

INTRODUCTION
Dedicated cetacean sigh�ng surveys in the western North
Paciﬁc were conducted in the late summer season since1995 as a part of the Japanese Whale Research Program
under Special Permit in the western North Paciﬁc (JARPN/
JARPNII) and the New Scien�ﬁc Whale Research Programin the western North Paciﬁc (NEWREP-NP) based on thesurvey procedures of the Interna�onal Whaling Commission/Southern Ocean Whale and Ecosystem Research(IWC/SOWER) (IWC, 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�matesof common minke, sei, and Brydeʼs whales were inves�gated and reported to the IWC Scien�ﬁc Commi�ee (SC)(IWC, 2001; 2010; 2016).
The Fisheries Resources Ins�tute (FRI) has also conducted dedicated sigh�ng surveys for cetaceans in the
North Paciﬁc since the 1980s (Buckland et al., 1992;
Miyashita et al., 1995; Miyashita and Kato, 2004; 2005;
Shimada, 2004; Kanaji et al., 2012). In 2019 the Govern34

ment of Japan decided to con�nue the sigh�ng surveys
in the North Paciﬁc (IWC, 2019) under the ra�onal thatthe collec�on of sigh�ng data to es�mate abundanceand biopsy/photo-iden�ﬁca�on data to examine stock
structure have contributed in the past to the work on
management and conserva�on of large whales by the
IWC SC (IWC, 2016).
This paper reports the results of the Japanese dedicated sigh�ng surveys conducted during 7 April and 10
November 2022 involving three seasons: spring, latesummer and autumn.

SURVEY DESIGN
Research period and area
In 2022, the surveys were conducted in three seasons:spring, late summer and autumn. The objec�ve of spring
and late summer surveys was the study of distribu�on
and abundance of large whales from poorly documented
seasons. Autumn survey aimed to study the movement
and southern migra�on of sei whales using satellite tags.
Figure 1 illustrates the research areas covered in eachseason.

Report and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

Figure 1.

Research areas covered by the 2022 dedicated sigh�ng surveys in each season. Upper le�: springsurvey. Kaiyo-Maru No. 7 (KY7) covered the yellow area, Yushin-Maru (YS1) covered the green area, andYushin-Maru No. 2 (YS2) covered the blue area. Upper right: late summer survey. KY7 covered the orange
area, and YS1 covered the pink area. Lower le�: autumn survey. YS2 covered the purple area. The autumn
survey did not have a pre-determined track line.

In spring (April to June), the research area was set up
between 35°N–46°N and 140°E–146°E. In late summer(August to September), the research area was set up
between 35°N–44°N and 140°E–154°E. Finally, in autumn
season (October to November), the research area was set
up between 38°N–46°N and 141°E–175°W.

program ver. 7.3ʼ (Thomas et al., 2010) and the numberof the line (width in the longitude) was decided by the
research schedule based on the IWC survey guidelines(IWC, 2012). The autumn survey did not set track lines
because the objec�ve in this season was not abundancees�mates but satellite tagging of sei whales.

Research vessels
The sigh�ng surveys in 2022 were conducted by the
research vessels Yushin-Maru (YS1), Yushin-Maru No. 2(YS2) and Kaiyo-Maru No. 7 (KY7) (Figure 2). The vessels
were equipped with a top barrel pla�orm (TOP), IO barrelpla�orm (IOP) and upper bridge.

Sigh�ng procedure
The sigh�ng surveys were conducted using (1) Normal
Passing mode (NSP), (2) Normal Closing mode (ASP)
and (3) Passing with Independent Observer mode (IO)
in order to es�mate whale abundance considering es�mated g(0). The survey modes adopted for each survey
are shown in Table 1. Three survey modes followed theprotocol endorsed for the SOWER surveys (e.g. Matsuoka
et al., 2003; IWC, 2008; 2012). As data from late summer survey are used to es�mate the abundance of large
whales, the IO mode was also adopted for this survey, as

Track line design
The pre-determined track lines in spring and late summer surveys are shown in Figure 1. The start points of the
track lines were decided randomly using the ʻDistance35

Technical Reports of the Ins�tute of Cetacean Research (2023)

Figure 2.

Research vessels par�cipa�ng in the 2022 dedicated sigh�ng surveys: Yushin-Maru (YS1) (upper le�),
Yushin-Maru No. 2 (YS2) (upper right) and Kaiyo-Maru No. 7 (KY7) (lower le�).

Table 1
Summary of the survey modes and searching condi�ons by each seasonal survey during the 2022 dedicated sigh�ng surveys.
Searching condi�ons
SeasonVesselSpring

KY7, YS1, YS2

Late summer

KY7, YS1

AutumnYS2

Survey mode
Normal Passing mode
Normal Passing mode
Passing with Independent Observer mode
Normal Closing mode

this survey can provide important data to calculate g(0).
For NSP and ASP mode, there were two primary observers in the top barrel (TOP) and two in the upper
bridge (captain and helmsman). All primary observers
conducted searching for cetaceans by using angle board
and scaled binoculars (7x).
For IO mode, there were two primary observers on
the TOP and two in the independent observer pla�orm(IOP). These observers conducted searching for cetaceans
by using angle board and scaled binoculars (7x). There
was no open communica�on between the IOP and theTOP. The observers and researchers on the upper bridge
communicated to the TOP (or IOP) independently, only toclarify informa�on and did not distract the top-men fromtheir normal searching procedure. These primary observers report sigh�ng-informa�on to researchers and otherobservers on the upper bridge for data recording.
The survey eﬀort began 60 minutes a�er sunrise and36

Visibility(n.miles)Wind speed(kt)

Searchingspeed (kt)

≥2.0

17.0>

10.0≥

≥2.0

17.0>

10.0≥

≥2.0

21.0>

11.5≥

ended 60 minutes before sunset, with a maximum of 12hours per day (maximum 06:00–19:00, including 30 minutes for meal�me for lunch and supper, when surveying
in IO mode) when the weather condi�ons were acceptable for observa�ons. Detailed search condi�ons for eachsurvey are shown in Table 1.
Experiments
Table 2 describes the details of the planned experiments
for each survey. Distance and angle experiments wereconducted in the middle of the survey period. The experiment was conducted to evaluate measurement error
and followed the protocol of the IWC/SOWER and IWCPOWER surveys (IWC, 2012).
When large cetaceans such as blue and humpback
whales were found, photo-id images were obtained using
Canon EOS 7D Mark II (with 100–400 mm lens) from thebow or upper deck. Further, biopsy skin sampling usingReport and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

the Larsen system (Larsen, 1998) was conducted when
blue, ﬁn, sei and humpback whales were sighted. The satellite tagging experiment using the Air Rocket Transmi�er
System (LK-ARTS) was also conducted for ﬁn, sei, Brydeʼsand common minke whales.

RESULTS
Brief narra�ve of the surveys
Spring (April–June)
KY7 departed Hakodate, Hokkaido, Japan on 7 April, andstarted the survey in the research area on 8 April. KY7
paused the survey on 4 May for a scheduled port call, andentered Hakodate, on 6 May for refueling and disembarka�on of researchers. On 11 May, KY7 departed Hakodate, and resumed the survey on 12 May. The survey wascompleted on 7 June. KY7 arrived in Hakodate on 9 June.
YS1 and YS2 departed Shiogama, Miyagi, Japan on 14
April. YS1 and YS2 started the survey in the research areaon 15 April and completed it on 21 May. YS1 and YS2 arrived in Shiogama on 23 May.

Late summer (August–September)
YS1 and KY7 departed Shiogama on 2 August and 3 August, and started the surveys on 3 and 4 August, respec�vely. On 24 August, KY7 suspended the survey and entered Hakodate for refueling. KY7 departed Hakodate andrecommenced the survey on 25 August. KY7 completed
the survey on 16 September and arrived in Shiogama on
17 September. YS1 completed the survey on 22 September and arrived in Shiogama on 30 September.
Autumn (October–November)
The YS2 departed Shiogama on 17 October and began thesurvey on 18 October. The vessel completed the survey
on 9 November and arrived in Shiogama on 10 November.
Searching eﬀort
A summary of searching eﬀort and coverage in each seasonal survey is shown in Table 3. A total of 8,340.9 n.miles(15,447.3 km) were searched in all seasonal surveys.

Table 2
Experiments planned in each seasonal survey during the 2022 dedicated sigh�ng surveys.
SeasonVesselSpringLate summer
AutumnKY7, YS1, YS2
KY7, YS1
YS2

Planned experiments
Photo-ID, biopsy, satellite tagging, distance and angle experiments
Photo-ID, biopsy, satellite tagging, distance and angle experiments
Photo-ID, biopsy, satellite tagging

Table 3
Summary of the survey periods and searching eﬀort by each seasonal survey in the 2022 dedicated sigh�ng surveys.
SeasonResearch period

Plannedcruise track(n.miles)Searchingeﬀort NSP
(n.miles)Searchingeﬀort IO
(n.miles)Searchingeﬀort Total(n.miles)Coverage ofeﬀort (%)

2022/04/08–05/04

1,019.2

781.9

–

781.9

76.7

2022/05/12–06/07

1,019.2

607.9

–

607.9

59.6

YS1

2022/04/15–05/21

1,298.1

1,139.7–

1,139.7

87.8

YS2

2022/04/15–05/21

1,317.4

936.1

–

936.1

71.1

Sub total—

4,653.9

3,465.6–

3,465.6

74.5

2022/08/04–08/24

1,122.3

484.9

463.1

948.0

84.5

2022/08/25–09/16

965.7

439.4

407.9

847.3

87.7

YS1

2022/08/03–09/22

3,060.8

1,351.2

1,339.2

2,690.4

87.9

Sub total—

5,148.8

2,275.5

2,210.2

4,485.7

87.1

YS2

2022/10/18–11/09—

389.6*

—

389.6

—

—

9,802.7

6,130.7

2,210.2

8,340.9

81.1

VesselKY7
SpringLatesummerAutumn

KY7

Total* Searching eﬀort ASP (n.miles).

37

Technical Reports of the Ins�tute of Cetacean Research (2023)

Sigh�ngs
SpringTables 4a and 4b show the total sigh�ngs for large andsmall cetacean species, respec�vely, made in spring
season 2022. The sigh�ng loca�ons of each species areshown in Figure 3 together with sea surface temperature(SST).

4.48 and 8.39, respec�vely while the DIs of YS1 and YS2
were 0.09 and 0.11, respec�vely.
Sei whale
This species was not sighted in the spring season.
Brydeʼs whale
A total of 14 schools (19 individuals including one motherand calf pair) were sighted south of 38°N (Figure 3). The
range of SST at the sigh�ng posi�ons was 8.8°C–21.0°C(mean SST: 18.6°C). Observed mean school size was 1.36.
The DI of YS1 was 0.44.

Blue whale
This species was not sighted in the spring season.
Fin whale
A total of 96 schools (153 individuals including three mother and calf pairs) were sighted north of 40°N (Figure 3).
The range of SST in the sigh�ng posi�ons was 1.8°C–9.2°C(mean SST: 5.2°C), and the mean school size was 1.59.
One biopsy sample was collected from one individual.
The Density Index (DI: schools of primary sighted/100 n.
miles searching distance) of KY7 in April and May were

Common minke whale
This species was the most frequently sighted species
in the spring season (149 schools and 170 individuals)(Figure 3). One mother and calf pair was sighted at posi�on 42°40ʹN, 145°03ʹE. The mean school size was 1.14
and the range of SST at the sigh�ng posi�ons was 1.3°C–

Table 4aTotal number of sigh�ngs of large whales made in spring 2022, by research vessel and species.
KY7 (Apr.)

Species

KY7 (May)

YS1

YS2

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

39
0
59
1
0
0

46
0
67
1
0
0

55
0
84
1
0
2

105
0
96
1
0
4

1
14
2
32
0
30

1
19
2
38
0
59

1
0
4
12
1
3

1
0
5
15
1
3

96
14
149
46
1
35

153
19
170
55
1
66

Fin whale
Brydeʼs whale
Common minke whale
Humpback whale
North Paciﬁc right whale
Sperm whale
Sch.: Schools, Ind.: Individuals.

Table 4b
Total number of sigh�ngs of small cetaceans made in spring 2022, by research vessel and species.
Species
Bairdʼs beaked whale
Common dolphin
Northern form short-ﬁnned pilot whale
Southern form short-ﬁnned pilot whale
Rissoʼs dolphin
Killer whale
True type Dallʼs porpoise
Dalli type Dallʼs porpoise
Uniden�ﬁed type Dallʼs porpoise
Ziphiidae
Mesoplodon spp.
Sch.: Schools, Ind.: Individuals.
38

KY7 (Apr.)

KY7 (May)

YS1

YS2

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

10
0
0
0
0
11
0
0
0
0
0

36
0
0
0
0
89
0
0
0
0
0

9
0
0
0
0
7
0
1
11
0
0

46
0
0
0
0
73
0
7
30
0
0

2
1
6
0
2
7
17
1
18
5
4

11
25
66
0
18
19
114
8
150
9
5

0
0
0
1
0
1
16
0
8
3
0

0
0
0
30
0
3
90
0
32
5
0

21
1
6
1
2
26
33
2
37
8
4

93
25
66
30
18
184
204
15
212
14
5

Report and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

Figure 3.

The loca�ons of large and small cetaceans sighted during the spring season 2022. Rolling 32 days averagesea surface temperature data from 23 April to 23 May 2022 and 9 May to 9 June obtained by MODIS-Aqua(Original data: Ocean color web, from h�ps://oceancolor.gsfc.nasa.gov/ (Accessed 2023-4-20)), are also
shown.

15.9°C (mean SST: 5.2°C). The DIs of KY7 in April and May
were 2.05 and 3.62, respec�vely. The DI of YS2 was 0.21.
Six biopsy samples were collected, and one satellite tag
was a�ached to one individual.
Humpback whale
A total of 46 schools (55 individuals including one motherand calf pair) were sighted (Figure 3). The mother and calf
pair was sighted at 36°48ʹN, 142°02ʹE. Observed meanschool size was 1.20. The range of SST in the sigh�ng posi�ons was 2.9°C–21.0°C (mean SST: 9.1°C). The DI of KY7
in May was 0.33. The DIs of YS1 and YS2 were 2.19 and
0.21, respec�vely. Seven individuals were photographed.
North Paciﬁc right whale
One school (one individual) of es�mated body length of
12.1 m was sighted at 42°16ʹN, 143°57ʹE (Figures 3 and 4).
The SST in the sigh�ng posi�on was 5.3°C. This individual
was photographed and a biopsy sample was obtained.

Figure 4.

A North Paciﬁc right whale sighted in spring 2022 (17May) during the 2022 dedicated sigh�ng surveys.

The DI of YS2 was 0.11.
Sperm whale
A total of 35 schools (66 individuals) were sighted (Figure 3).
The range of SST in the sigh�ng posi�ons was 1.5°C–
39Technical Reports of the Ins�tute of Cetacean Research (2023)

21.1°C (mean SST: 9.6°C). Because the opportunity toapproach the schools was limited, there was li�le informa�on on school size, body length and calves. The meanschool size was 1.89 when the school size was conﬁrmed.
The DIs diﬀered markedly between seasonal surveys,
0.33 for KY7, 2.19 for YS1 and 0.21 for YS2.

Late summer
Tables 5a and 5b show the total sigh�ngs for large andsmall cetacean species, respec�vely, made in late summer season 2022. The sigh�ng loca�ons of each species
are shown in Figure 4 together with SSTs.
Blue whale
This species was not sighted in the late summer season.

Small cetaceans
Five species of the the family Delphinidae, three speciesof the family Phocoenidae and three species of the family
Ziphiidae were sighted (Table 4b). The most common species sighted was the Dallʼs porpoise (72/431), followedby killer whale (26/184). Dallʼs porpoises were sighted
primarily at the 37°N–41°N la�tudinal band in April–May,and north of 44°N in May–June. Killer whales and Bairdʼsbeaked whales were mainly sighted north of 44°N.

Fin whale
Four schools (four individuals) were sighted north of
39°N (Figure 5). Mean school size was 1.00. The SST in thesigh�ng posi�on was 18.9°C–22.2°C (mean SST: 21.2°C).
The DIs were 0.11 and 0.11 by KY7 (August) and YS1,
respec�vely.

Table 5aTotal number of sigh�ngs of large whales made in late summer 2022, by research vessel and species.
KY7 (Aug.)

Species
Fin whale
Brydeʼs whale
Common minke whale
Humpback whale
Sperm whale

KY7 (Sep.)

YS1

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

1
18
2
2
16

1
18
2
3
73

0
23
0
0
10

0
24
0
0
24

3
190
0
0
130

3
210
0
0
203

4
231
2
2
156

4
252
2
3
300

Sch.: Schools, Ind.: Individuals.
Table 5b
Total number of sigh�ngs of small cetaceans made in late summer 2022, by research vessel and species.
Species
Bairdʼs beaked whale
Common dolphin
Northern form short-ﬁnned pilot whale
Southern form short-ﬁnned pilot whale
Rissoʼs dolphin
Paciﬁc white-sided dolphin
Killer whale
Melon-headed whaleSpo�ed dolphin
Striped dolphinBo�lenose dolphin
True type Dallʼs porpoise
Dalli type Dallʼs porpoise
Uniden�ﬁed type Dallʼs porpoise
Ziphiidae
Mesoplodon spp.
Sch.: Schools, Ind.: Individuals.
40

KY7 (Aug.)KY7 (Sep.)

YS1

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

7
0
1
0
1
5
0
0
0
0
1
3
0
4
0
0

35
0
18
0
45
293
0
0
0
0
10
29
0
38
0
0

17
0
1
0
3
0
0
1
0
0
2
0
0
1
7
3

103
0
95
0
70
0
0
15
0
0
20
0
0
3
23
9

3
13
0
2
7
0
1
0
1
22
0
0
0
2
57
2

28
787
0
89
59
0
8
0
45
1,273
0
0
0
22
117
5

27
13
2
2
11
5
1
1
1
22
3
3
0
7
64
5

166
787
113
89
174
293
8
15
45
1,273
30
29
0
63
140
14

Report and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

Figure 5.

The loca�ons of large and small cetaceans sighted during the late summer. Rolling 32 days average sea
surface temperature data from 21 August to 21 September 2022 obtained by MODIS-Aqua (Original data:
Ocean color web, from h�ps://oceancolor.gsfc.nasa.gov/ (Accessed 2023-4-20)), are also shown.

Sei whale
This species was not sighted in the late summer season.
Brydeʼs whale
Brydeʼs whales were the most frequently sighted species in this season (Figure 5). A total of 231 schools (252individuals) were sighted. Mean school size was 1.09. The
range of SST at the sigh�ng posi�ons was 16.2°C–27.4°C(mean SST: 23.0°C). The DIs were 1.90, 2.71 and 6.91 by
KY7 (August), KY7 (September) and YS1, respec�vely.
Common minke whale
Two schools (two individuals) were sighted north of 42°N
(Figure 5). The SSTs in the sigh�ng posi�on were 14.4°C
and 21.7°C. The DI of KY7 (August) was 0.21.
Humpback whale
Two schools (three individuals) were sighted (Figure 5).
Mean school size was 1.50. The SST at the sigh�ng posi�on were 16.4°C and 21.4°C. The DI of KY7 (August) was

0.21.
Sperm whale
A total of 156 schools (300 individuals including one
mother and calf pair) were sighted in this season (Figure 5).
A school consis�ng of 22 sperm whales was sighted at
42°15ʹN, 144°16ʹE. Mean school size was 1.92. The rangeof the SST in the sigh�ng posi�on was 16.0°C–29.6°C(mean SST: 22.2°C). The DIs were 1.69, 1.18 and 4.68 for
KY7 (August), KY7 (September) and YS1, respec�vely.
Small cetaceans
In this season, ten species of the family Delphinidae,
three species of the family Phocoenidae and three species of the family Ziphiidae, were sighted (Table 5b). The
most common sighted species was the striped dolphins(22/1,273), followed by the common dolphins (13/787).
Paciﬁc white-sided dolphins and Dallʼs porpoises weremainly sighted north of 40°N. Common dolphins andstriped dolphins were sighted primarily east of 145°E.
41Technical Reports of the Ins�tute of Cetacean Research (2023)

Bairdʼs beaked whales were sighted mainly west of 143°E.
The species of the family Ziphiidae were sighted east of
143°E.
Duplicate sigh�ngs
A total of 26 and 104 re-sigh�ngs of large cetaceans wererecorded during IO mode throughout this season involving several species.
AutumnTables 6 shows the total sigh�ngs for large and small cetacean species, made in autumn 2022. The sigh�ng loca�onof each species is shown in Figure 6 together with SSTs.
Blue whale
Three schools (three individuals) with body lengths of
17.8 m, 23.8 m and 24.1 m were sighted west of 150°E(Figure 6). The range of SST was 9.7°C–17.2°C (mean SST:
12.5°C). Two individuals were photographed.

Figure 6.

42

Fin whale
Five schools (eight individuals) were sighted (Figure 6).
Mean school size was 1.60, and the range of SST at thesigh�ng posi�ons was 11.7°C–14.8°C (mean SST: 13.6°C).
Table 6
Total number of sigh�ngs of large whales and small cetaceansmade in autumn 2022, by research vessel and species.
SpeciesBlue whale
Fin whale
Sei whale
Brydeʼs whale
Humpback whale
Sperm whale
Northern right whale dolphin
Rissoʼs dolphin

YS2
Sch.

Ind.

3
5
32
3
4
7
1
1

3
8
44
3
4
9
6
8

Sch.: Schools, Ind.: Individuals.

The loca�ons of large and small cetaceans sighted during autumn 2022. Rolling 32-days average sea
surface temperature data from 16 October to 16 November 2022 obtained by MODIS-Aqua (Original data:
Ocean color web, from h�ps://oceancolor.gsfc.nasa.gov/ (Accessed 2023-4-20)), are also shown.

Report and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

Sei whale
A total of 32 schools (44 individuals) were sighted (Figure 6).
The range of SST at the sigh�ng posi�ons was 10.1°C–
17.8°C (mean SST: 13.4°C). Mean school size 1.38. Biopsy
samples were collected from 16 individuals, and satellite
tags were a�ached on 16 individuals.

Small cetaceans
In this season, two species of the family Delphinidae weresighted (Table 6): Rissoʼs dolphin (1/8) and northern rightwhale dolphin (1/6).
Experiments
Sighting distance and angle experiment
In spring, the Es�mated Angle and Distance Experiment
was conducted by KY7 on 26 April and 28 May. It was
conducted on 5 May by YS1 and on 11 May by YS2. Inlate summer, the experiment was conducted on 15 September by KY7 and on 3 September by YS1. The results ofthis experiment will be used for calibra�ng the sigh�ng
distances and angle data used for the calcula�on of abundance es�mates.

Brydeʼs whale
Three schools (three individuals) were sighted (Figure 6)
with es�mated body lengths of 11.3 m, 11.8 m, and 12.8 m.
SST at the sigh�ng posi�on were 14.6°C, 14.9°C and
18.5°C.
Common minke whale
This species was not sighted in the autumn season.
Humpback whale
Four schools (four individuals) were sighted (Figure 6).
The range of SST in the sigh�ng posi�on was 10.4°C–
12.9°C (mean SST: 11.6°C).

Photo-ID
The number of individual photographed is shown in Table 7,
by species. All photographs were stored in the ICR catalogs and will be used for inves�ga�ng the stock structure
and movement of those cetacean species in the future.

Sperm whale
In total, seven schools (nine individuals) were sighted(Figure 6). Mean school size was 1.29. The range of SST
was 10.7°C–15.0°C (mean SST: 13.7°C).

Biopsy sampling
A total of 30 biopsy samples were collected during the2022 dedicated sigh�ng surveys. Table 8 shows the number of biopsies, by seasonal survey, research vessels andTable 7
Numbers of individuals photographed during the 2022 dedicated sigh�ng surveys, by seasonal survey, research vessel and species.
Species

Spring
KY7 (Apr.) KY7 (May)Late summer
YS1

YS2

KY7 (Aug.) KY7 (Sep.)

Autumn
YS1

YS2

Total

Blue whale
Humpback whale
North Paciﬁc right whale
Killer whale

0
1
0
0

0
1
0
2

0
4
0
0

0
1
1
0

0
0
0
0

0
0
0
0

0
0
0
0

2
0
0
0

2
7
1
2

Total

1

3

4

2

0

0

0

2

12

Table 8
Numbers of biopsy samples collected during the 2022 dedicated sigh�ng surveys, by seasonal survey, research vessel and species.
Species

Spring
KY7 (Apr.) KY7 (May)Late summer
YS1

YS2

KY7 (Aug.) KY7 (Sep.)

Autumn
YS1

YS2

Total

Fin whale
Sei whale
Brydeʼs whale
Common minke whale
North Paciﬁc right whale

0
0
0
0
0

0
0
0
3
0

0
0
6
2
0

1
0
0
1
1

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

0
16
0
0
0

1
16
6
6
1

Total

0

3

8

3

0

0

0

16

30
43

Technical Reports of the Ins�tute of Cetacean Research (2023)

species. All samples were stored at the ICR laboratory andwill be used in gene�c analyses for inves�ga�ng the stock
structure of those species in the future.

A large number of ﬁn and common minke whales weresighted in April–June in the Japanese side of the Sea of
Okhotsk. Common minke whales were mainly sighted
east coast of the Shiretoko Peninsula and west coast of
144°E. On the other hand, ﬁn whales were sighted east of
144°E which suggests that these species were separated
in distribu�on at the western coast of the Sea of Okhotsk.
Direct feeding behavior was not observed, but seabirds
were concentrated close to the sigh�ng posi�ons of ﬁnand common minke whales. From this, it is possible thatthese two species were distributed in this area for feeding
during this season.
A large number of humpback whales were sighted
in April–June in the southern part of the Paciﬁc side ofJapan. Most of humpback whales were sighted south of
40°N probably during their northward migratory path.
At the same �me, it was conﬁrmed that Brydeʼs whales
were also distributed south of 37°N, although in small
numbers.
The August-September survey covered the North
Paciﬁc from the coast of Japan to 154°E, providing important late summer sigh�ng data for Brydeʼs and sperm
whales. At the same �me, several sigh�ng data for ﬁn,
common minke and humpback whales were obtained inSatellite tagging
Satellite tag a�achments were a�empted during eachseasonal survey, but a�achments only occurred during
spring and autumn. The number of individuals taggedis shown in Table 9, by seasonal survey, research vessel
and species. A total of 16 sei whales were tagged, all inautumn. These were evenly a�ached among the sigh�ngs(Figure 7). Tracking data obtained from satellite tags willcontribute to the elucida�on of the movement of whales
in each season and the �ming of the start of migra�on
between high la�tude feeding areas and low la�tude
breeding areas.

HIGHLIGHTS OF THE SURVEY
The sigh�ng surveys conducted in 2022 were completed
successfully. They provided unique data obtained not
only in the late summer, but also in the spring and autumn seasons for which informa�on on cetacean distribu�on and abundance have been very scarce. Some main
characteris�cs of the surveys are summarized below.

Table 9Numbers of individuals a�ached with satellite tags, by each season and research vessel in 2022.
SpringSpecies

YS1

YS2

KY7 (Aug.) KY7 (Sep.)

Autumn
YS1

YS2

Total

Fin whale
Sei whale
Brydeʼs whale
Common minke whale

0
0
0
0

0
0
0
0

0
0
5
0

1
0
0
1

0
0
0
0

0
0
0
0

0
0
0
0

0
16
0
0

1
16
5
1

Total

0

0

5

2

0

0

0

16

23

Figure 7.

44

KY7 (Apr.) KY7 (May)Late summer

The loca�ons of tagged sei whales during autumn 2022. Loca�ons were obtained from photographs taken
at the �me of the tagging.

Report and highlights of the Japanese dedicated sighting survey in the North Pacific in 2022

this season. These three species were sighted north of
40°N. Compared to previous surveys conducted during
the same seasons and same research area (Katsumata
et al., 2021), Brydeʼs whales in 2022 were more northernly distributed. The northward exten�on of this species
could have been inﬂuenced by higher monthly mean SSTs
between 41°N–43°N than in 2020 (Figure 8). The monthly
mean SST between 41°N–43°N was higher than in 2020,
which could explain the northward migra�on of this species.
Consistent with previous surveys in 2020 (Katsumata
et al., 2021), no common minke whales were sighted in
the pelagic part. Murase et al. (2023) reported the mean
SST for sigh�ng posi�on of this species over the past four
years (2002, 2004, 2005, 2006) was 15.5°C. In this season,
the monthly mean SST at the research area was higher
than 16°C, and cold water below 16°C formed north of
43°N. From this, it is considered that common minke
whales distribu�on was shi�ed to the north in 2022.
In October–November, a large number of sei whales
were sighted in the northwest side of the Paciﬁc. Sei
whales were distributed in high density near 180°, andthe SST in this area was in the 10°C range. Although justa single feeding behavior was observed, this area could
be a feeding area for this species because seabirds wereconcentrated around the sigh�ng posi�ons. Satellite tags
were successfully a�ached on 16 individuals to study the
movement and southern migra�on of sei whales. The

study of the migra�on will contribute to resource management by assis�ng the interpreta�on of the gene�canalyses on stock structure. Several blue, ﬁn, humpbackand sperm whales were also sighted in this area.
As in the previous surveys, the 2022 surveys collected
data on small cetaceans in the same way as large cetaceans. The analyses of these data will provide valuable
informa�on on the distribu�on and abundance of small
cetaceans in diﬀerent seasons.

ACKNOWLEDGEMENTS
We acknowledge the Government of Japanʼs assistancein providing the research permits and funding for thesecruises. We also thank the Captains Koji Maki, Chikamasa
Okoshi, Hidenori Kasai, Yasuaki Sasaki, and their oﬃcers
and crew of the Yushin-Maru, Yushin-Maru No. 2 andKaiyo-Maru No. 7 for their hard work and dedica�onthat led to the successful execu�on of these surveys. We
express our deep gra�tude to Takashi Hakamada and
Megumi Takahashi of the Ins�tute of Cetacean Research(Tokyo) for expert support in planning survey design. We
thank Yoshihiro Fujise and Tsutomu Tamura and the staﬀ
of the Ins�tute of Cetacean Research (ICR) and Kyodo
Senpaku Co., Ltd. for their assistance in arrangements
and support for the cruise. We also thank Kenji Konishi
of ICR for satellite tagging and Mioko Taguchi of ICR forbiopsy sample management. Finally, we thank Luis A. Pastene for his assistance in preparing this report and to the
Editorial Team of TEREP-ICR for editorial work.

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Sigh�ng posi�on of Brydeʼs whales and monthly
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