DISTRIBUTION AND BEHAVIOR OF BAIRD'S BEAKEDWHALES OFF THE PACIFIC COAST OF JAPANTOSHIO KASUYA*ABSTRACT

Aerial sighting records from the last 25 years and ship board sightingsin 1984 indicate that the Baird's beaked whales which occur off the Pacificcoast of Japan in summer through autumn live in schools of 1 to 30
individuals (average < 10). The schools stay underwater for up to about
one hour, 4 to 5 times longer than the time at surface. Baird's beaked
whales in the area are seasonally distributed on the continental slope at
depth of 1,000 to 3,000 m, and north of 34°N latitude under the influenceof the subsurface cold Oyashio Current. The whales appear off the Boso
Peninsula near the southern limit of their range on the Japanese Pacificcoast in early summer reaching a peak in August, and then move northalong the continental slope, peaking in October-November off the Pacificcoast of Hokkaido. This seasonal movement is discontinuous to that of thisspecies in the Sea of Japan and Okhotsk Sea, suggesting that these threeareas are inhabited by separate populations. However, the northern rangeof the Pacific coast population is still unconfirmed and their distribution in
December to May is unknown.
INTRODUCTION

Omura, Fujino and Kimura (1955) analyzed the catch records of Baird's
beaked whale, Berardius bairdii Duvernoy 1851, by Japanese small-type whaling,
and concluded that they arrived off Boso Peninsula in early summer andmoved to the north presumably to arrive off the east coast of Hokkaido inearly autumn. They also suggested that such individuals might belong to a
population which was different from those using the Sea of Japan or in the
Okhotsk Sea.
Nishiwaki and Oguro ( 1971 )'s analysis of subsequent data from the same
source supported many of Omura et al.'s conclusions. In addition, they
concluded that Baird's beaked whales were distributed off the Pacific coast ofJapan in waters deeper than 1,000 m. Because of the coastal nature of thewhaling, no information was available on the offshore limit of the distributionof this species. (see Study of also Kasuya (1971)).

* Far Seas Fisheries Research Laboratory, 5-7-1, Orido, Shimizu-ski, Shizuoka-ken 424, Japan
Sci. Rep. Whales Res. Inst.,
No. 37, 1986, 61-83

62

KASUYA

Ohsumi ( 1983) analyzed sighting records collected by scouting vessels of
the Japanese factory ship whaling fleets and by research vessels chartered by
the Japan Fisheries Agency, and concluded that the distribution of Baird's
beaked whales off the Pacific coast of Japan extended to offshore waters. His
data were later reanalyzed by Kasuya and Ohsumi (1984) who were unable toreinforce this conclusion because sightings in offshore water were scarce andbecause they observed an area of low density between coastal and offshore
high density areas.
The present study analyzes the distribution and migration of Baird's
beaked whales off the Pacific coast of Ja pan using the results of sighting cruises
conducted in the summer of 1984 plus aerial sighting records accumulated
over 25 years by Fishery Aviation Co. Ltd.
MATERIALS AND METHODS

Aerial sightings
Aerial sightings records of marine mammals were provided by Fishery
Aviation Co. Ltd. The records were accumulated during chartered flights tomake oceanographic observations (e.g. water temperature, marine pollutant,
red tide and floating algae) or to search for fish schools in order to provide
information for purse seiners. The data cover the period from April 1959 to
December 1983. Information from this series collected before April 1970 was
also used by Kasuya (1971).
Observation was conducted at an altitude of 500 m along track lines thatwere arranged by the person who chartered the flight to scan his objective
area. The observers (usually the Fishery Aviation Company personnel) wereallowed to diverge from the predetermined track line or to descend foroccasional observation or for photography of their sightings. In principle thearea was searched using transect of infinite width, but the distribution ofobservers effort probably changed depending on the main objective of each
TABLE l. LIST OF AIRCRAFTS THAT COLLECTED AERIAL SIGHTING RECORDS
OF BAIRD'S BEAKED WHALES FOR THE PRESENT STUDY
Year
1953-'58
1958-'64
1965-'79
1979-'82
1982-'83

Type of Aircraft*

EngineSighting
speed

Cruising
distance

Piper Tripacer PA22
Cessna 175
Cessna 182 Skylane
Cessna 182 Skylane
Aero Commander 680F
Cessna 182 Skylane
Cessna U206G
Aero Commander 680F

135Hp
175Hp
230Hp
230Hp
380Hp x 2
230Hp
300Hp
380Hp x 2

95kt
lOOkt
105kt
105kt
140kt
105kt
120kt
140kt

4.5 hours
7.5 hours
7.5 hours
7.5 hours
7.5 hours
7.5 hours
9.0 hours
8.0 hours* All high wing type.
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

63

BAIRD'S BEAKED WHALES

N

40°

I

I

o•

I

-------~-------.----------------------

_.c?·

5

30°

'
I
I

I'

130°

150°E

Fig. 1. Geographical areas used in the analysis of the aerial sighting data collected
between April 1959 to December 1983.

flight and type of the aircraft used.
There were considerable changes over the years in the size, crmsing
speed, and range of the aircraft used as detailed in Table 1. In 1965 large
engined aircraft was introduced, then in 1979 the company obtained a twinengined aircraft. These changes resulted in the expansion of the survey area
and increased survey effort in offshore waters (Fig. 3).
The number of observers was usually two (pilot and navigator) for
single-engine air-craft, and three (pilot, navigator and engineer) for twinengine aircraft. The view from the front was superior in the latter. Before
1981, both observers in the single-engine aircraft sat in the port seats, causing
an unbalanced search effort. Since 1981, however, an observer was located oneach side of the single-engine aircraft. In the twin-engine aircraft (used since1979), the pilot searched front and port side, the engineer front and starboard
side, and navigator the starboard side only.
These changes in aircraft and sighting technique, and search area affectedsighting efficiency making it impossible to use these sighting records tomonitor changes in the relative density of Baird's beaked whales. However,.
they provide useful information on distribution. The 25 years of aerial sighting
data were stratified by geographical area (Fig. 1) and month. Data collectedby observers in single- and twin-engine aircraft were separated in Table 2, butwere combined in the later analyses.
Sci. Rep. Whales Res. Inst.,

No.37,1986

64

KASUYATABLE 2. AERIAL SIGHTING RECORDS OF BAIRD'S BEAKED WHALES BY MONTH,
DIVISION AND YEAR

Division lJan. Feb. Mar.
1959-'63 (single-engined plane)
NM flown
No. schools
No. whales
1964-'68 (single-engined plane)
NM flown
No. schools
No. whales
1969-'73 (single-engined plane)
NM flown
29
No. schools
No. whales
1974-'78 (single-engined plane)
NM flown
No. schools
No. whales
1979-'83 (single-engined plane)
NM flown
171
No. schools
No. whales
1979-'83 (twin-engined plane)
NM flown
No. schools
No. whales

Apr.

Oct.

Nov.

Dec.

Total

77 1,845 4,808 3,389
3
2
6
10
22
27

598

-

10,81111
59-

13,7814
12

37-

17,824848

112

315 3,202 5,866 3,794 3,159
l
2
40
10

-

16,448350137555 4,786 1,272
2
9

61

7,840
3
17

-

9,470
l
4

May June
94

106

717

63

July

-

Aug.

Sep.

1,083 7,812 4,0003l6
6317 2,720 8,013 6,708
4
l
3
24
4
20

105

25

128 2,223 6,591
l
4

398

858
I
8

Division 2
1959-'63 (single-engined plane)
NM flown
210
651 1,035 2,956 4,610 5,476 4,679 2,738 4,568 8,458 1,040 36,421
17
9
5
l
37
I
4
No. schools
40
20
6
166
12
86
No. whales
2
1964-'68 (single-engined plane)
383 5,256 4,270 3,497 2,532 5,695 7,168 11,569 5,310 49,547
NM flown
1,865 1,615
387
11
10
I
No. schools
I
3
35
l
5
3
l
153
61
No. whales
15
42
16
14
2
2
1969-'73 (single-engined plane)
NM flown
1,367
730 233
308 1,106 8,348 4,025 4,904 6,491 5,713 3,779 2,233 39,237
No. schools
I
I
16
5
4
3
2
No. whales
13
100
53
16
4
9
5
1974-'78 (single-engined plane)
NM flown- 1,560 1,123 1,785 2,298 1,331 2,219 2,156 2,242 4,342 1,679 20,735
No. schools
I
I
No. whales
12
12
1979-'83 (single-engined plane)
NM flown
524
408 1,911
571 5,599 1,066 1,180 957 2,436 4,524 4,825
356 24,357
No. schools
693
No. whales
62
72
10
1979-'83 (twin-engined plane)
101 7,419 6,379 5,140 4,797 4,539
677- 31,253
NM flown- 2,201
No. schools
1173lNo. whales
94
75
16
3
(Continued)

Sci. Rep. Whales Res. Inst.,

No. 37, 1986

65

BAIRD'S BEAKED WHALESTABLE 2. (Continued)
Division 3
1959-'63 (single-engined plane)
185
NM flown
75
No. whales
1964-'68 (single-engined plane)
NM flown
1,460
462
662 1,447
547
No. whales
1969-'73 (single-engined plane)
NM flown
17748
82
718 1,128
No. schools
No. whales
1974-'78 (single-engined plane)158
541 1,109 2,761
NM flown
124
No. schools
No. whales
1979-'83 (single-engined plane)
NM flown
248
140
26 3,000
257
No. schools
No. whales
1979-'83 (twin-engined plane)
660 1,525 3,391
NM flown
232
No. whales
Division 4
1959-'63 (single-engined plane)
NM flown
220
No. whales
1964-'68 (single-engined plane)
NM flown
380
310
721 1,000
300
No. schools
No. whales
1969-'73 (single-engined plane)
NM flown
2,444 4,833 7,134 6,01210,346
No. whales
1974-'78 (single-engined plane)
NM flown
1,319 3,327 7,86112,497 9,799
No. whales
1979-'83 (single-engined plane)
NM flown
1,740
595 3,560 10,933 8,462
No. schools
No. whales
1979-'83 (twin-engined plane)
NM flown- 2,804
663 2,793 2,582
No. whales
Division 5
1959-'83 (single- and twin-engined planes)
NM flown
3,938 14,395 19,963 3,847 2,020
No. whales

Sci. Rep. Whales Res. Inst.,

No. 37, 1986

125

488

699

326

783

399

508 1,497 2,167 10,260

379
3
15

624

77

438

207

32

4,398
3
15

460
2
40

42

292

165

81

395

6,128
2
40

625

532
3
9

-

4,828
3
9

-

6,615

108

98

488 2,200

318

371 1,845 1,771 1,186 10,572

I

I

2

2

574

964 2,937 2,814 3,154 42,926

1,690

782

749 2,142 3,350 3,778 47,294

573

962

645 1,069-

385- 5,147

821

I

15
51

617 33,410
I
15
8,893

48 1,096

384

130 45,821

66

KASUYAN

40°,__......_......__.___.____.~..__......__._......_,:......L.-L---''--'--....._,;;:--_.___.____.___..___.30°

130°

140°

1so E
0

Fig. 2. Track lines of the Baird's beaked whale sighting cruises in 1984 by the
Toshimaru No. 25 (thin solid lines) and Shonanmaru (thick solid lines). Each closed
circle indicates the position of a Baird's beaked whale school. Only track lines cruisedwith mast-top observers (normal sighting effort) are indicated.

Shipboard sightings
Data were obtained in 1984 during two whale sighting cruises in thewestern North Pacific using whale catcher boats Toshimaru No. 25 (750 grosstons) and Shonanmaru (91 7 gross tons) chartered by the Ja pan Fisheries
Agency. The cruises lasted 88 days (9 June to 4 September) and 80 days (9June to 27 August), respectively. The track lines in the study area cruised withsighting effort are shown in Fig. 2. Additional areas west of l 70°E and northof l0°N were also searched during the cruises as detailed by Miyashita (1985a),but no sightings of Baird's beaked whales were recorded.
I was on board the second cruise of the Toshimaru No. 25 whichsurveyed Japanese coastal waters north of 34°30'N from 7 July to 6 August.
This survey was conducted from the northern leg to the southern leg of thesurveyed grid while the range of the distribution of the Baird's beaked whales
was extending from south to north. Each leg was arranged approximately
perpendicular to the coastline, i.e. along the expected density gradient of
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

BAIRD'S BEAKED WHALES

67

Baird's beaked whales. I verified all sightings (303 individuals in 42 schools
including secondary sightings). In addition, one school of four Baird's beaked
whales was sighted on the first leg of the third cruise (from 7 August to 4 September) of the same vessel on 8 August in 34°07'N, 140°00'E. Although I
did not verify this sighting, I have used it in the present study.
Sightings were conducted by both vessels during the entire cruising
period (from port to port) except for night time and unfavorable weather
conditions. Sightings during the second and third cruises of the Toshimaru
No. 25 were conducted using the methodology develqped for the Antarctic
minke whale sighting cruises (Best and Butterworth, 1980) on a predeterminedcourses at a speed of 12 knots (second and third cruises of the Toshimaru
No. 25) or 11.5 knots (other cruises). The length of each leg varied fromabout 300 nautical miles of major legs to about 60 n. miles of subsidiary legs.
The latter were designed to investigate details of the distribution of Baird's
beaked whales in the high density area. Each of the former legs was completed
spending about 3 days, but the latter a half day. Although the geographicallybiased density of sighting effort needs to be taken account in estimating thewhale population (Miyashita, 1985b), such corrections are unnecessary for the
analysis of pattern of distribution of whales in the present study.
All marine mammal schools sighted were approached to confirm specificidentification and school structure. Data were collected on the position of theship at sighting, the direction of the school from the track line, the radial
distance from the position of sighting to the school, species, school size,
estimated size composition (if available), surface water temperature, visibility,
Beaufort scale of wind. Radial distances were estimated visually (for nearsightings) or by summing an estimate based on the time required to approachto near distance and visual estimate of the rest of the distance. Position of thevessel was estimated using loran. Two mast-top observers (eye height ofobservers were 17 m above sea level for the Toshimaru No. 25, 20 m for the
Shonanmaru) and five or six upper wheel-deck observers (Toshimaru No. 25,
10 m above sea level; Shonanmaru, 11 m) were used during the daytime from15 minutes after sunrise to 15 minutes before sunset during periods when
visibility was over 3 n. miles (usual maximum sighting distance of the Baird's
beaked whale) and Beaufort scale less than 5. The mast-top observers rotatedpositions (mast-top, upper-wheel deck, and recess) every two hours. Twomates were alternately in charge of recording sighting data and position of
the vessel. The captain and one to three scientists in charge of sighting spent
the entire working time on the upper-wheel deck.
When wind was 5 or more in Beaufort scale or the visibility was less than
0.5 n. mile, observations ceased and the vessel was allowed to drift as far as
time permitted. When visibility was between 0.5 and 3 n. miles and the windless than Beaufort scale 5, sightings were conducted for Dall's porpoise,
Phocoenoides dalli, using only upper wheel-deck observers. (Sightings of thisspecies usually occur within 0.5 n. mile of the vessel (Bouchet, 1981; Kato,
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

68

KASUYA

1983)). No Baird's beaked whales were sighted in the northern area wherethese poor sighting conditions occurred.
The mast-top observers continuously used 50mm X 7 binoculars. The
upper-wheel deck observers used them occasionally (they tended to searchclose to the boat). Polarized sunglasses were worn by most observers. Throughspeaker system every sighting was relayed between scientists, observers and amate on duty; and this communication was also monitored by engineers. The
mast-top observers commanded the vessel when it was approaching whale
schools.
During the entire Shonanmaru cruise and the first cruise (9 June to 6July) of the Toshimaru No. 25, sightings were mostly done under good conditions.
The school size and body length composition was estimated by the
mast-top observers. Schools of Baird's beaked whales were identified without
difficulty as a group of individuals swimming in a same direction in a close
distance and surfacing almost simultaneously (see photographs in Kasuya,
1971; Kasuya and Ohsumi, 1984; Nishiwaki and Oguro, 1971).
Diving intervals were recorded for 18 schools of Baird's beaked whales
containing from one to 25 individuals (mean = 9.1) while I was on board of
the second cruise of the Toshimaru No. 25. We usually started timing at theinitial sighting of blows continuing until the school composition was confirmed
at a close distance. The number of observed dives ranged from one to six per
school. Since whales dive when scared, schools were approached after themain engine was stopped 0.5 to 1 n. mile from the school. The main engine
was always slowed down step by step prior to stopping. The vessel usuallywaited for the next surfacing after stopping its main engine close to the placeof the dive. Schools which were chased by the vessel or found close to otherschool(s) were excluded from the analysis of diving interval because of thepossibility that their behavior was unnatural or because the difficulty ofidentifying individual schools. The resurfaced individual school was identified
based on the position and the size of the schools.
RESULTS

Range of distribution and seasonal movements
All the aerial and shipboard sightings of Baird's beaked whales were limited
to waters north of 33°N, and most were east of about 140°£. In spite ofconsiderable aerial and shipboard sighting effort few Baird's beaked whales
were sighted west of 140°£, and all these were close to 140°£ (Figs 2, 3 and
4). These data agreed with the range reported by Omura et al. (1955), Kasuya(1971), Nishiwaki and Oguro (1971), Ohsumi (1983) and Kasuya and Ohsumi(1984).
The distribution of Baird's beaked whales was also limited to coastal
waters west of 144°£ despite considerable searching effort further offshore (toSci. Rep. Whales Res. Inst.,

No.37, /986

69

BAIRD'S BEAKED WHALESI

l

8 6 I 1JI

d~ ~ . .

~,!_ ~-·t-:_1-t--t--J t--lrtf\J-1"}

9 9:6 1b [_/1---+---r--+--+--t--i '='"'
6 7 5 I 2 6\-!_9-+-8--7-:4-+--+--+--1(\ii~ 8 ~_,:_3--+---+-+-

ls 5 3 : 1·11't>-/t 'i~ -·1-'---t+----j-+---:,__-_,...t-_-_,i "'""'",__2_,_fi_4-+-~-+-7--r ~_1 2 1

2- '- - - ,_1--+--+---1-1--t--;.

140°~ _: 4 3 1 1

7

5 6:5
1

2 5

5 4

3

1

2

1

1dJs 5 4 : 2 1o35
I:>-,../' ~ 2 2 2+-1--+--1+---+---+--i
L.

I

1

I

d

:_2-+--+----< 1-Hfl,_.,/

~ L/
P'

9 a:3

,,.___,_~__,...___,.__,_~ - ~ _7.! ~ ,_1_3-+-1-+--+--+--t-

2 -~ _1_, 3_,1_1-+-1-+-1-+-_1+---+---+--

2

1

2

4

3

1 2

1

145°

1

140°

1

1

1

1

145°

1

1

1

140°

145°

E

Fig. 3. Distribution of the aerial sighting effort in June to December (1959 to 1983)
when most of the sightings of Baird's beaked whale occurred. The index of effort
is expressed for each one degree squares of latitude and longitude by the numberof times entered by the aircraft while it was conducting sightings (surveyed distanceis not indicated). The scale for the number of times entered is, 1: 1-4, 2: 5-9,
3: 10-19, 4: 20-29, 5: 30-39, 6: 40-59, 7: 60-89, 8: 90-129 and 9: 130-169
times in the 27 years. Seasons are grouped based on change in aircraft types.

~1959-'64 ~ / //..,I 1(1 vv
a .CY'f'/
1

I
I

2

I

-~[7

~~

17

13 tt 1t

--;\

~-'

~o

I

- :\
~

140°

(

~

I--

\

1979-'83,.._!_

:

j

.25J

2

1:7

2

3z ~~,--l;:1"}g;::f'- (1!5)~~ \'12V:-- __:,_
I

,J

]...J

f

I

n!'.I 2} ~~·I

I<>-1 !s

/

\

1---

2

I

35°

I
I

2

_!_:: )-

(

I(
/

_../

145°

140°

145°

Fig. 4. The number of Baird's beaked whales sighted by the flights indicated in Fig.
3 of this study. The thin solid lines indicate 1,000 and 3,000 m contours, and thedotted lines one degree squares within 60 nautical miles from the coast of the majorisland. In addition to the sightings listed here, there were recorded in May fourindividuals in two schools in 36°-37°N, 141°-l42°N and 36°-37°N, 142°-l43°N,
respectively.
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

N

101I

-

s:

k

~

I
I

107 (2:
I

v

); /

40°

3~1/,31

d?f13)6}140°- bJlf>----µ;_))tt 171•/145°/

30 211~-\_3_1)

I/

)

I

I
I--

I

~~J l// __ :

/

·~
3 2L:
(
-,I

~J/

I

I .51 !/I:·-;//l:.\ \361/6,__~l/

131

~

)::

"~ \hi-~-f

i4I 471II

1965-"78I--~ ~ 5~___ : ___
~\ \

~-

- ,iff'- /if"~r~
~

E

70

KASUYA

50

40

Division 1

30
Division 2

~

z
0
0
0

10

(/)

Cl/

111

5

.c.
~

0
Division 3

20
0
3

5

7
Month

9

11

Fig. 5. Seasonal changes in the density of Baird's beaked whales based on aerialsighting records from April 1959 to December 1983. Square: flown for more than
10,000 nautical miles, closed circle: 5,000 to 10,000 nautical miles, open circle: lessthan 5,000 nautical miles.

160°E). The absence of shipboard sightings of Baird's beaked whales north of
39°N was partially due to the small sighting effort the coastal waters of thisregion at depths between 1,000 and 3,000 m where the occurrence is
expected (see below).
Table 3 and Fig. 5 show the seasonal changes in the density of Baird's
beaked whales as observed in the aerial sighting records. The whales arrive inthe southern part of the range (Division 2) in May, and the density reaches
a peak in July and then declines towards October. This pattern agrees withthat suggested by the limited data for Division 3. In northern waters (Division1), the density apparently increases from August to November, although theabsolute density seems to be lower than that in the sourthern waters.
Factors affecting the distribution of Baird's beaked whale
Fig. 2 shows the sighting track line of the Toshimaru No. 25 and the,Shonanmaru, the position of sightings of Baird's beaked whale and theSci. Rep. Whales Res. Inst.,

No. 37, 1986

~ ;£

~[

~

~

~

~~

......

""~.:"'~

Division 3
NM flown
No. schools
No. whales
Whales/l ,000 NM

Division 2
NM flown
No. schools
No. whales
Whales/1,000 NM

Division I
NM flown
No. schools
No. whales
Whales/1,000 NM

Month

0

0

-

0

1,960

0

1,208

0

2,043

-

0

-

6,943

0

-

171

3

2,753

-

2

3,966

0

-

-

29

1

0

-

4,225

0

-

0

-

11,727

24,121
2
4
0.2

0

0

3,521

-

916

5

-

106

4

0

-

1,187

26,971
10
38
1.4

0

-

337

6

1,898
5
55
30.0

20,649
40
256
12.4

837
2
40
47.8

7

1,981
3
9
4.5

20,088
25
150
7.5

/3
14
1.2

11,6288768

24,05518
91
3.8

37,876
13
65
1.7

9
10

I, 111

24,8925
19
0.8

19,5611053
2.7

TABLE 3. SEASONAL CHANGE OF THE DENSITY OF BAIRD'S BEAKED WHALES OFF
THE PACIFIC COAST OF JAPAN ESTIMATED FROM THE AERIAL SIGHTING RECORDS
IN 1959 THROUGH 1983

1,910

32,973
7
25
0.8

4,652
2
18
3.9

11

2,596

10,6182
14
1.30.....:r

\J)

t'1

>
t""'

::c:

:::;;

t)

t'1

::-::

>

t'1

co

r:ii

t)

;;

-

>

co

61

12

72

KASUYA

N

40°

35°

140°

150°E

Fig. 6. The oceanographical environment at the position of Baird's beaked whalesighting (closed circle) during the Toshimaru No. 25 cruise (The track lines areindicated by the thin solid line). The thick solid line indicates the surface watertemperature observed during the cruise in July-August 1984 and the dotted line
the l 5°C isotherm at a depth of 100 m in January and July 1984 (Ja pan
Meteorological Agency, 1984).

topography of the area. The whales were limited to water depths of 1,000 to
3,000 m on the continental slope. The same distribution pattern is seen fromthe aerial sighting records (Figs 3 and 4). The majority of aerial sightings
were recorded in one degree squares (about 60 X 44 to 49 n. miles) which
overlap with the above water depth range. Even in recent years when theaerial sighting effort expanded to waters further offshore, the range ofsightings of Baird's beaked whales remained constant, indicating that thewhales are concentrated in waters between 1,000 and 3,000 m deep at leastfrom June to December. In contrast, Baird's beaked whales are not distributedat these depth off the Pacific coast of southwestern Japan, west of 138°£ (Figs
2 and 4) indicating that distribution is influenced by some additional factors.
Fig. 6 shows the surface water temperatures measured during the cruises
and the l 5°C isotherms at 100 m below the surface in January and] uly 1984
cited from Japan Meteorological Agency (1984). Baird's beaked whales occurred at surface water temperatures of between 23° and 29°C, but the
distribution did not agree with the range of the surface water isotherms.
The southern limit of the sightings coincides with the 15°C isotherm at
a depth of 100 m (Fig. 6). The position of this isotherm changes little between
Sci. Rep. Whales Res. Inst.,

No. 37, 1986

73

BAIRD'S BEAKED WHALESTABLE 4. SCHOOL SIZE FREQUENCIES OF BAIRD'S BEAKED WHALES OFF THE
PACIFIC COAST OF JAPAN (DIVISION l THROUGH 4) BASED ON AERIAL SIGHTINGDATA (1959 TO 1983) AND OBSERVATION ON BOAD OF THE TOSHIMARU NO. 25 IN 1984
School
size

2
3
4
5
6
7
8
9
10
ll
12
13
14
15
17
18
20
25
30
Total
Mean
SE

Year
1959-'63

1964-'68

1969-'73

1974-'78

1979-'83

1959-'83

1984

ll
9
5
4
4
4
l
3
0
2
l
0

9
10
7
3
l
2
3
2
0

0
7
3
2
5

0
0
0
0
0
0
0
0
0
2
0
l
0
0
0
0
0
2
0

0
5

20
31
16
ll
14

2
0
0
l
0
0
0
48
4.7
0.6

0
0
0
0
0
0
0
0

40
4.2
0.8

2
0
3
0
0
0
0
0
0
0
27
6.0
0.9

6
17.0
3.2

0
4
0
l
0
0
5

5
8
0
12
2
2
2
2
6

0
0
0
0

l
3
0
2

3
3
6
8
4
3
2
3
0
2
0
0
0
0
3
0
l
3
l
0

27
7.8
l.O

148
5.9
0.4

42
7.2
0.9

2
4
3
0

lO

seasons, suggesting that it represents a stable southern boundary of the cold
Oyashio Current extending beneath the warm Kuroshio Current, the northernrange of which moves widely between seasons.
In August, the warm Kuroshio Current extends to latitude 40°N
(represented by 25°C surface isotherm). The northward shift of the concentration of Baird's beaked whales from off the Boso coast (35°-36°N) in JulyAugust to off Hokkaido (40°-43°N) in August through November may be an
influence of this summer expansion of the Kuroshio Current. Thus it isprobable that the southern range of Baird's beaked whales off the Pacificcoast of northern Ja pan may be in some degree affected by the warm surface
water of the Kuroshio Current.
School structure
Aerial and shipboard estimates of the size of Baird's beaked whale
schools are listed in Table 4. The shipboard estimates ranged_from 1 to 25
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

74

KASUYA

with a mode at 4 and a mean of 7.4 individuals. The relatively high frequencies
at 10, 15 and 20 represent a rounding effect. These features are not significantly different from the school size frequencies reported by small-typewhaling vessels (Ohsumi, 1983).
In the aerial sightings recorded before 1969 there were more singletons
than in the aerial sightings in recent years, although the upper ranges of theschool size frequencies were not different between the two data sets. Suchapparent change in the school size composition could be produced by (1) areal change in school composition, (2) underestimation of school size inearlier aerial sightings, or (3) missing small schools in recent aerial sightings.
The school size of the shipboard sightings in 1984 tended to be intermediateof the two patterns. During the Toshimaru No. 25 cruise in 1984, I encountered
several schools whose size apparently increased while the vessel was approaching quietly after stopping the main engine. I therefore consider that the lasttwo cases were more probable for aerial survey which cruised faster than vessels
and was done as an supplemental work of the chartered flights. Therefore thehistorical change in the school size composition of Baird's beaked whale is notknown from the present data, school size of the present population is likely
to be represented better in the shipboard sighting data.
data.
The body length estimates were made by mast-top observers (who had
experience of whaling other than Baird's beaked whale). Of the 283 Baird's
beaked whales in 36 schools sighted during the first and second cruises of the
Toshimaru No. 25, 265 were estimated to be 33 feet (9.9 m) or over, and only
15 individuals (5.7 %) 32 feet (9.6 m) or less (1 individual (0.4 %) at 20 feet,
6 (2.3 %) at 30 feet, 8 (3.0 %) at 32 feet). Three individuals (all estimated to
be 30 feet) were accompanying their presumed mothers. According to data
presented by Ohsumi (1983), the proportion of small individuals (:::;9.6 m) in
the catch of whaling in 1977-1981 was 24.7 %, which was higher than thecorresponding figure obtained above (5.7 %). Therefore the cruise data are
not suitable for estimating birth rate, without further assessment of (1) the
accuracy of the body length estimates, (2) the possibility of missing small
calves in the tight school, (3) knowledge of the early postnatal growth of thespecies, and (4) knowledge of the still unconfj.rmed segregation of animals by
growth and reproductive stages.

The pattern of surfacing and diving
While a school was at the surface, blows were usually observed continually,
and this was used as an indication that the school was at the surface. Before
the vessel arrived at the position of initial sighting, the target school often
dived and surfaced several tir:nes. In one particular case of a school of eight
whales, which was not used in the following analysis, the vessel was withinsight of the school recognized by the color of shallow submerged bodies andrings for· eight minutes. During the period the vessel followed the school with
Sci. Rep. Whales Res. Inst.,

No. 37, 1986

75

BAIRD'S BEAKED WHALESTABLE 5. SURFACING INTERVAL OF BAIRD'S BEAKED WHALE SCHOOLSTime in
min.
l

2
3
4
5
6
7
8
9

At surface

Below surface

numberpercent

numberpercent

5
5
7
5

14.7
14.7
20.6
14.7
2.9
5.9

2

6.1
3.0

l

2
1
3
1
2

3.0
6.1
3
6.1
3.0
9.1
3.0
6.1

4
3
3

3.0
3.0
12.1
9.1
9.1

l

2

2
l

2.9

lO

11
12
13
14
15
16-20
21-25
26-30
31-35
36-40
41-45
46-50
51-55
56-60
61-65
66-70
Not measured

6

17.6

Total
Mean (minutes)

34
3.9

100

2.9
2.9

2

6.1
3.0
3.0

3.0

33
18.2

100

engines off by the force of its inertia. The school was observed to change thedirection frequently. However as soon as the vessel slowly started the main
engine, the school dived deeply resurfacing after 20 minutes. This illustrates
the importance of the method of approaching schools to obtain correct dataon diving behaviour of Baird's beaked whales.
The time spent by a school at the surface ranged from about one to 14
minutes, but usually less than five minutes (Table 5) as stated by Matsuura(1942). The longest time at the surface (14 minutes) was for a school of 25
whales. This observation was made while the vessel approached from a distanceof 1.5 n. miles to about 400 m as described above. The length of the preceding
dive was 22 minutes. The mean observed time at the surface (3.9 minutes)
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

76

KASUYA(Table 5) is subject to error. It may be overbiased as a result of our failure torecord short surface times, or underbiased due to our misidentification of
surfacings in which the whales were not spouting continuously, as two separate
surfacings.
Dive times ranged from one to 67 minutes. The longest dive was recorded
for a school of 20 individuals. This record is rather ambiguous. This school
dove 3 n. miles from the vessel just after being sighted at 1440 hour on 27
July 1984. It surfaced for one or two minutes at 1457, 1534 and 1546 hour.
Then at 1653 (67 minutes after the last surfacing which was brief), one small
individual (no body length estimate was available) was seen surfacing about
0.5 n. miles from the vessel. The remaining members of the school were
found about 1.5 nautical miles from the vessel at 1704 hour (78 minutes after
previous sighting) in the direction in which the small individual was travelling).
We were uncertain whether or not the other whales in the school surfaced atth~ same as the small individual, so we have used the smaller more conservative
dive time (67 minutes). I considered that the small individual which surfaced
alone at 1653 hour belonged to the larger school because it would be unnaturalfor the small individual to live alone and it was travelling toward the larger
school. I also considered that the school surfaced at 1704 hour was same withthat dove at 1546, because the schools were so uncommon that confusion was
unlikely (during that day's survey of 7 hours 27 minutes (about 90 n. miles)
this was the only school seen).
There were five major modes in the dive times; 1-2, 5-12, 14-29, 37-49
and over 60 minutes. Dives of 1-2 minutes may not have been true dives as
discussed above. Excluding these, the mean dive time was calculated at 19.8
minutes (n = 30), which does not significantly differ from the figure in Table
TABLE 6. CORRELATION BETWEEN DIVING TIME AND TH.E FOLLOWINGSURFACING TIME IN SCHOOL OF BAIRD'S BEAKED WHALES
Length of the next surfacing (minutes)

Preceeding
di~ing _time

2

mmm.

l- 5
6-10
l l-15

3

4

5

6

2
2

16-20
21-25
26-30
31-35
36-40
41-45
46-50
Total

3

4

6

8

14

Total

4
4
3
2
3

2

2

7

3

2

20
Sci. Rep. Whales Res. Inst.,

No. 37, 1986

BAIRD'S BEAKED WHALES

77

5 (18.2 minutes) based on all recorded dives. The mean dive time was 4.7
times longer than the mean time at the surface. About half of the observed
dives (17 of 33 dives) exceeded 13 minutes.
Although the number of sequential dives observed for each school was
too small (maximum was six) to test the randomness of the sequence of longand short dives, there was an apparent tendency for long dives (over 20
minutes) to be followed by shorter ones below 13 minutes (6 dives by 4
schools). (However, one school of 20 individuals made two successive long
dives of 41 and 67 minutes separated by 8 minutes of the surface.) Of 9 divesbelow 13 minutes, 7 were followed by a dive of over 13 minutes, but only one
in 6 dives exceeding 13 minutes was followed by a dive of over 13 minutes.
The difference was statistically significant (Chi-square test, 0.025 < p < 0.05).
The comparison of length of a dive and that of the next surfacing revealed
that long dives tended to be followed by a long period at the surface (Table
6). Significantly fewer number of short dives(< 15 minutes) were followed bylong time(::'.:: 4 minutes) at the surface (Chi-square test, 0.01 < p < 0.025).
DISCUSSION

Distribution in the western North Pacific
Baird's beaked whales is known in the eastern North Pacific from the
Pribilof Islands to Baja California (Leatherwood, Reeves and Foster, 1983),
and in the western North Pacific from the Bering Sea, Okhotsk Sea, Sea ofJapan and Pacific coast of Japan north of the Tokyo Bay (Tomilin, 1967;
Nishimura, 1970). Nishiwaki's (1967) claims that the northern bottlenose
whale, Hyperoodon ampullatus (Forster, 1770) might exist in the Sea of Japanand that the beaked whales reported by the whalers in the Okhotsk Sea might
represent this species, have not been confirmed (Nishimura, 1970). All 13
beaked whales caught in the Okhotsk Sea that were reported by Japanese
small-type whaling boats between 1978-1982 were identified as Baird's
beaked whales based on the largest pair of teeth collected from each individuals(Kasuya, unpublished). A skull of beaked whale taken off the Okhotsk coastand identified by a vernacular name of the area has been confirmed as Baird's
beaked whale (Dr H. Omura, personal comm. in Oct. 1985). Thus there are
no data to indicate the presence of H. ampullatus in the temperate and subarctic
waters off Japan*.
Baird's beaked whales are known to dive deeply (Ohsumi, 1983) and forlong periods (see above). The analysis of stomach contents recorded bywhalers (Nishiwaki and Oguro, 1971) or those examined by a biologist (W.
Walker, personal comm. in 1985) indicated that they feed mainly on bottom* This does not deny the possible existence in the tropical western North Pacific of hitherto unidentified Hyperoodon-likeodontoceti, which were sighted and photo-recorded during the 1985 sighting cruises (Far Seas Fisheries ResearchLaboratory, unpublished).
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

78

KASUYA

organisms (principally deep sea fish). The common occurrence of bottom
substance such as pebbles in the whales' stomachs and the presence of scars
attributable to hard substances other than teeth of the conspecifics on the tipof the upper jaw and melon region (Kasuya and Brownell, unpublished) alsosuggest bottom feeding. This. information together with the distribution of
Baird's beaked whales obtained by the present study suggest that the whales
feed (at least in early summer to autumn) on organisms living on the ocean
floor of a depth of 1,000 to 3,000 m and affected by a subsurface cold current.
The distribution of the catch of Baird's beaked whales in the Sea of Japan andsouthern Okhotsk Sea reported by Omura et al. (1955) occurred in the
Toyama Bay (Sea of Japan at about 37°N), off the Sea of Japan coast ofsouthern Hokkaido (41°-42°N) and off Abashiri on the southern coast of the
Okhotsk Sea. These grounds are also characterized by the presence of deep
waters (> 1,000 m) near the coast.
However, Fedoseev (1985) reported that the species was abundant inApril and May in the northern Okhotsk Sea north of Sakhalin where water
depth is less than 500 m. This will presumably relate to the availability of foodspecies in shallower waters in higher latitudes.
Seasonal movement of stocks in Japanese coastal waters
Fig. 7 shows the seasonal changes in density of Baird's beaked whales
summarized using catch data of Omura et al. (1955) in 1948-'52 and sighting
data of small-type whaling vessels in 1977-'82 reported by Kasuya andOhsumi (1984). These data agree with the present results as well as those of
Matsuura (1942) and Nishiwaki and Oguro (1971). Omura et al. (1955)
concluded that the Baird's beaked whales which arrive off the Boso Peninsulain May-June move northwards to the waters off Sanriku (38°-40°N) after
one month, peaking off the Pacific coast of Hokkaido (42°-43°N) in Octoberand November. Although they were not sure whether Baird's beaked whale
off the Pacific coast of Hokkaido belong to the same population as those off
Sanriku and Boso Peninsula, the continuity of geographical (Figs 2 and 4) andseasonal (Figs 5 and 7) distribution suggest one population.
In the Okhotsk Sea, the catch of Baird's beaked whales has two peaks,
one in May-June and the other in September-October. This bimodal
distribution of the catch is unlikely to be caused solely by minke whales being
the preferred target as claimed by Kasuya and Ohsumi (1984), because it isalso reflected in the number of sightings per 100 operation hours of smalltype whaling vessels (Fig. 7). Baird's beaked whales are present in the northern
Okhotsk Sea in April-May (Fedoseev, 1985), slightly before their abundancein the southern Okhotsk Sea starts to decline.
The limited catch in the sea of Japan occurred on the two grounds (atabout 37°N and 41°N) off Japan, from June to August. This is same as theseasonality of the catch off the Pacific coast in similar latitudes (off Boso
Peninsula and Sanriku region).
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

79

BAIRD'S BEAKED WHALES

25

S. Japan, 41° N

0
25

•

S. Japan, 37°N

0200
Okhotsk,

150

'

44°N

'
''
''

100
l/l

Cl.I

0

~

50

-

_,,,1J

50

Ill

..c.

0
0 200
z
100
0

''

,,-

JJ'

-----~

Pacific, Hokkaido, 43°N

,,

,l

..d,
t-'--.....__.___..__~__._-e.,....-e;::~-.::::::::..__...::::::--1

Pacific, Sanriku,
37°- 40°N~o,,0 f--L--'---'--o--- o--- ---oPacific, Boso. 35°N

300

' .. o..... o,

o"'"

'\
\
\

200

\

h.

100
0

J

FMAM

JASOND

Month
Fig. 7. Seasonal change in density of Baird's beaked whales in the Japanese coastal
whaling ground (Sea of Japan, Okhotsk Sea and Pacific coast). The closed circle andsolid line indicate the number of whales captured between 1948-1952 (Omura etal., 1955), and the open circle and dotted line number of whales sighted per 100
hours of operation of small-type whaling vessels in 1977-1982 seasons (Kasuya andOhsumi, 1984). Densities of whales based on less than 200 operation hours havenot been indicated.

The seasonal changes in density summarized above could be explainedby assuming three populations of Baird's beaked whale; in the Okhotsk Sea,
the Sea of Japan, and off the Pacific coast of Japan as proposed by Omura etal. (1955), and assuming a seasonal north-south migration within the range ofeach population. La Perouse and Tatarskiy Straits (between the Sea of Japanand Okhotsk Sea) and Tsugaru Strait (between the eastern Sea of Japan andPacific Ocean) presumably block migration between the three regions. Thesestraits are less than 200 m deep (the maximum depths of these seas exceed
3,000 m). As Baird's beaked whale is found off the Pacific coast of Japan in
the latitude of 33° to 44°N only in the waters between 1,000 and 3,000 m (seeabove), it is reasonable to assume that these straits will act as barriers between
populations.
Sci. Rep. Whales Res. Inst.,
No. 37, 1986

80

KASUYA

However, this does not necessarily mean that the Baird's beaked whalesin the Okhotsk Sea do not pass through the Kuril Islands, where there is astrait (at about 4 7°N) exceeding 1,000 m in depth. Sleptsov ( 1955) reported
the occurrence of Baird's beaked whales on the both coast of the Kuril Islands
and on the east coast of the Kamchatka Peninsula. Although there are no dataon the identity of the stocks in these areas, the likely incomplete isolation or
the shorter geological history of isolation between the Okhotsk Sea and theJapanese Pacific coast populations may explain the lack of body length
differentiation between the two stocks. According to Omura et al. (1955), thewhales caught in the Sea of Japan were considerably smaller than those fromother areas (modal length 30-32 feet in the Sea of Japan against 34-36 feetin the Okhotsk and Pacific coasts).
Behavior of Japanese Pacific coast ''population"
The available data indicate that the Japanese Pacific coast "population"of the Baird's beaked whale is limited to the waters of the continental slope
between the southern tip of Boso Peninsula (about 35°N) and the east coastof Hokkaido at 43°N. This distribution is similar to that of local stocks of the"true-type" population of Dall's porpoise, Phocoenoides dalli (True, 1885) inthis region (Kasuya, 1978; Kasuya and Shiraga, 1985; Miyazaki, Jones andBeach, 1984), and the short-finned pilot whale, Globicephala macrorhynchus
Gray, 1846, (Miyazaki, 1983; Kasuya and Marsh, 1984; Kasuya, unpublished).
Presumably, some marine mammals in this relatively cold triangular-shaped
area of coastal waters were isolated from the major subarctic North Pacificarea by the island of Japan and by the offshore warm Kuroshio Current.
A seasonal northward movement of the Baird's beaked whale concentration along the continental slope is apparent from both catch statistics andsighting records. This phenomenon can be explained without assuming any
significant northward movement of individual whales, by assuming offshoreinshore movements of whales which progress from south to north during
July-November season. This assumption requires Baird's beaked whales to be
distributed in the offshore waters of latitudes where they are known to beabsent from the continental slope. This study showed that the whales werevery scarce in the offshore area in summer through autumn. Therefore, this
explanation seems impossible, and I consider that they migrate from earlysummer through autumn along the continental slope off the Pacific coast ofJapan. However, this does not deny possibility of offshore dispersion of someindividuals in autumn to winter season (see below).
Since the surface water temperature starts to decline in September off
the Pacific coast of Japan, it is unlikely that the Baird's beaked whales which
arrive off the Pacific coast of Hokkaido (presently identified northern limit ofthis "population") in September continue their northbound migration.
Although the available data are insufficient, due to scarcity of sighting
effort and absence of whaling operation in winter to spring seasons, to suggest
Sci. Rep. Whales Res. Inst.,

No. 37, 1986

BAIRD'S BEAKED WHALES

81

where the whales winter after the disappearance from Hokkaido coast in
November and till the reappearance off the Boso Peninsula in May. It seems
likely that they migrate south and perhaps disperse in offshore waters. The
offshore dispersion of the Baird's beaked whales in autumn is suggested by
the rapid density decline during the northward migration in August throughNovember (Figs 5 and 7). The magnitude of the density change seems to be
too large to be explained on the basis of increased dispersion in the slightly
wider 1,000-3,000 m deep continental slope in the northern area (Fig. 2).
Omura et al. (1955) showed that males predominated in the catch of
Baird's beaked whales by Japanese small-type whaling in all of the fishinggrounds mentioned above. Using catch statistics off Boso Peninsula, Ohsumi( 1983) showed that males exceeded females in all of the 21 fishing seasons
from 194 7 to 1967, and that this changed since 1968 toward the dominanceof females which lasted only for several seasons. Ohsumi's statistics showedalso that the dominance of males in the catch resumed in 1977 as before
1968. Kasuya (1984), using statistics from 1947 through 1983, showed thatthe fishing seasons of Baird's beaked whale~ off Boso Peninsula in late l 950's
to early l 970's (especially those for 1959 through 1972 seasons) apparently
started earlier (in May) and ended later (in December) than the other seasons,and included months when the distribution of the species in the ground wasvery scarce. I suspect that the sex ratio may not have changed but that there
were serious error in the catch statistics for seasons between presumably due
in some degree to inclusion of other species such as sperm whales.
However, the dominance of males in the catch was also found in datacollected by biologists. Among 29 Baird's beaked whales caught off the Boso
Peninsula (near the southern limit of the population) in 1976 and 1977
seasons, 20 were males (Dr Y. Naito, personal communication), and of the 36
whales caught in the same area in 1985 season 24 were males (Kasuya,
Brownell, Mead, Walker and Wada, unpublished). This overall sex ratio (44males against 19 females) is significantly different from parity (Chi-square
test, 0.01 < p < 0.025). This imbalance of the sex ratio in the catch can occur
for two reasons (1) geographical segregation by sex as suggested by Ohsumi( 1983) or (2) higher catchability of males than females in the same school due
to possible difference of ship-avoidance behavior or of position relative toother members of the school. If the first explanation is correct, then the rangeof the population off the Pacific coast of Japan must extend outside the area
confirmed by the present study suggesting that the population is larger than
the 4,220 (cv = 0.295) individuals estimated by Miyashita (1985b). However,a dominance of males was reported for samples from three "populations"discussed above and those captured at various parts of the range of theirdistribution, making the first explanation less likely than the latter (behavioural)
explanation.

Sci. Rep. Whales Res. Inst.,

No. 37, 1986

82

KASUYAACKNOWLEDGEMENTS

Fisheries Aviation Co. Ltd (Tokyo) allowed me to analyze their cetaceansighting records. Dr P. Hammond of the Sea Mammal Research Unit (UK)helped me in planning the cruise track line of the Toshimaru No. 25 in 1984.
Dr H. Marsh of the James Cook University of North Queensland (Australia)
criticized the manuscript and corrected the English. Captain S. Suzuki of the
Toshimaru No. 25 and his crew cooperated in the present study during thecruise. Mrs Y. Yamamoto and K. Yano assisted in data analysis and drawing.
REFERENCES
BoucHET, G.C., 1981. Estimation of abundance of DaU's porpoise (Phocoenoides dalli) in the North Pacific
Ocean and Bering Sea. NWAFC Processed Rep., 81-1, 25pp.
BEST, P.B. and D.C. BUTTERWORTH, 1980. Report of the southern hemisphere minke whale assessment
cruise. 1978179. Rep. int. Whal. Commn, 30: 257-283.
FEDOSEEV, G.A., 1985. Records of whales in ice conditions of the Okhotsk Sea. IWC/SC/O 4, 8pp.
Japan Meteorological Agency, 1984. The ten-days marine report, nos 1346 and 1364.
KASUYA, T., 1971. Consideration of distribution and migration of toothed whales off the Pacific coast ofJapan based upon aerial sighting record. Sci. Rep. Whales Res. Inst., 23: 37-60.
KASUYA, T., 1978. The life history of Dall's porpoise with special reference to the stock off the Pacific coastof Japan. Sci. Rep. Whales Res. Inst., 30: 1-63.
KASUYA, T., 1984. Catch and effort data of the Japanese Baird's beaked whale fishery off the Boso Peninsula.
IWC/SC/SM 14, 18pp.
KASUYA, T. and H. MARSH, 1984. Life history and reproductive biology of the short-finned pilot whale,
Globicephala macrorhynchus, off the Pacific coast of Japan. Rep. int. Whal. Commn, (Special Issue 6):259-310.
KASUYA, T. and S. SH!RAGA, 1985. Growth of Dall's porpoise in the western North Pacific and suggested
geographical growth differentiation. Sci. Rep. Whales Res. Inst., 36: 139-152.
KAsUYA, T. and S. 0HSUMI, 1984. Further analysis of the Baird's beaked whale stock in the western North
Pacific. Rep. int. Whal. Commn, 34: 587-595.
KATO, M., 1983. Abundance survey of Dall's porpoise by Japanese salmon research vessels in the North
Pacific Ocean in 1982. Doc. Submitted to the meeting of the Sci. Sub-comm. of the Ad Hoe Comm. of Marine
Mammals, INPFC, Tokyo, 20-25, Feb. 1983. 44pp.
LEATHERWOOD, S., R.R. REEVES and L. FosTER, 1983. The Sierra Club handbook of whales and dolphins. Sierra
Club Books, San Francisco. 302pp.
MATSUURA, Y., 1942. On the northern porpoise whale, Berardius bairdii Stejneger, in the adjacent waters of"Bosyu". ]. Zool. (Tokyo), 54 (12): 466-473. (in Japanese with English summary).
MIYASHITA, T., 1985a. Bryde's whale stock in the western North Pacific estimated using sighting data.
IWC/SC/Ba 1, lOpp.
MIYASHITA, T., 1985b. Abundance of Baird's beaked whales off the Pacific coast of Japan and possible biasof estimate. IWC/SC/SM 13, 11 pp.
MIYAZAKI, N., 1983. Pilot whale off Kinkazan Island. Abst. Autumn Meeting jap. Soc. Sci. Fish., p. 55 (inJapanese).
MIYAZAKI, N., L. L. JONES, and J. R. BEACH, 1984. Some observations on the schools of dalli- and truei-type
Dall's porpoises in the northwestern Pacific. Sci. Rep. Whales Res. Inst., 35: 93-105.
NISHIMURA, S., 1970. Recent records of Baird's beaked whale in the Japan Sea. Puhl. Seto Mar. Biol. Lab.,18 (1): 61-68.

Sci. Rep. Whales Res. Inst.,
No. 37, 1986

BAIRD'S BEAKED WHALES83

NISHIWAKI, M., 1967. Distribution and migration of marine mammals in the North Pacific area. Bull. Ocean
Res. Inst., Univ. Tokyo, 1: 1-64.
NISHIWAKI, M. and N. 0GURO, 1971. Baird's beaked whales caught on the coast of Japan in recent 10 years.
Sci. Rep. Whales Res. Inst., 23: 111-122.
0HSUMI, S., 1983. Population assessment of Baird's beaked whales in the waters adjacent to Japan. Rep. int.
Whal. Commn, 33: 633-641.
OMURA, H., K. FUJINO, and S. KIMURA, 1955. Beaked whale Berardius bairdi of Japan, with notes on Ziphiuscavirostris. Sci. Rep. Whales Res. Inst., 10: 89-132.
SLEPTSOV, M. M., 1955. Biology of whales and whaling in the Far East. Pitzepromizdat, Moscow. Qapanesetranslation published by the Whales Res. Inst., Tokyo, 1955, 51 pp.).
ToMILIN, A.G., 1967. Cetacea. Israel Prog. Sci. Translations, Jerusalem. 717pp.

Sci. Rep. Whales Res. Inst.,
No. 37, I986