Biological Investigation on the Whales Caught by theJapanese Antarctic Whaling Fleets Season 1949-50

BY
KAZUHIRO MIZUETADASHI MURATACONTENTS

Page
Introduction ..•........•.....••....•.••..••••••..........•...•....•.•...... 73
Catch ..•................•...•••.••..••••..•.•.....................•••....•• 76
Body Colour. . . . . . . . . . . . . . . • . . . . • . . • • . . • . • • . • . . • . . . . . . . . . . . . . . . . . . . . • . . . . . . . 84
Whitish Scars •...•. ·. . • • • . . . . . . . . . • . • . . • . • . . . . . . . . • • . • . . . . . . . . . . . . . • • • . . . . • . 88
External Parasites . . . . . . . . . • • • . . . . . • . . . . . . . . • . . . . . . . . . . . . . • . . . • • • • • • • . . . . . . 90
Thickness of Blubber .....•..•...............•........•.•....•••.••••••••.. 94
Stomach Contents .••......•.......•••.••.•.•..••••••••••••.•....•........•. 101
Thickness and Colour of Mammary Glands ...••••••.••••••.•..••........••. 102
Foetuses ................................................................... 106
Ovaries ...................•.••....•••.......•...............•.•.••••••••••. 109
Testes .•.............•.••.•..••••..•••......•.........••.••••..•...•....••. 123
Vertebrae ................•.........•..••....•......•••.•..•.••••••••.•.•... 128
References ..•.•.....•.••••...•.••...........•.•••.•...•.••.•.•............. 130

Introduction

As in the preceding post-war seasons, Japan participated in the
Antarctic whaling expedition in 1949-50 with two whaling fleets,
namely the Hashidata Maru fleet and the Nisshin Maru fleet. Eachfleet consisted of one floating factory, seven catcher boats and one
reconnaissance vessel, and was accompanied by one tanker and several
cargo vessels.
The floating; factory Hashidate Maru, accompanied by the attachedcatcher boats, sailed from Yokohama on November 10, 1949 and arrived
on the Antarctic whaling grounds on December 19, 1949. The Nisshin
Maru and her catcher boats sailed from Yokosuka on November 1, 1949
and arrived on the whaling grounds as early as November 25, 1949.
This fleet was engaged in the sperm whaling for the following 25days until the baleen whaling season was opened. The production
from this operation is summarized in Table 1.
The grounds for sperm whales are located to the west of thosefor baleen whales, or between latitudes 61-64 °8 and longitudes 1161560E (Fig. 2).
The baleen whaling of this season, which was. commenced just at

K. MIZUE & T. MURATA

74

Table 1. Catch and processing of sperm whales
by Nisshin Maru fleet, 1949
Whales caught

172

Processed products a/
Sperm oil
Liver oil
·Frozen red meat
Gelatine material
Leather material
FlukesTotal(metric tons)
1,651.0
1.821
660.0
86.4
79.4
34.7
2,513.321

a/ The amounts of processed products shown are theestimates in the field.
0: 00 a.m. on December 22, 1949 by both fleets and closed on March 3
and 5, 1950 respectively by the Hashidate Maru and the Nisshin Maru
fleet, have yielded a total production as shown in Table 2. The figures
Table 2. Catch and processing of baleen whales by the two
Japanese fleets in the 1949-50 season
j Hashidate Maru j

Total

I

Whales processed :Blue
Fin
Humpback
Total ·

384
459
49
888

Blue whale units

631.5

Processed products a/:
Whale oil
Red meat, frozen
Other frozen products
Red meat, salted
Ventral grooves, salted
Other salted products
BaleenBone meal
Liver oilBlood powder and glue
Total

Nisshin MaruI

(metric tons)
12,200.0
10,118.7344.8
3,795.3
2,924.1
431.6
113.2
102.5
21.6016.443
30,058.244

817
1,056
. 67
1,940

433
597
22
1,052
740.3
(metric tons)
14,810.0
13,259.0529.0
3,281.4
3,143.0
314.0
100.2
None
21.24
None
35,457.84

I1,371.3(metric tons)
27,010.0
23,377.7
873.8
7,076.7
6,067.l
745.6
213.5
102.5
42.841
6.443
65,516.684

a/ The amounts of processed products shown are the estimates ih the field.

75

Biological investigation on the Whales Caught

Table 3. Catch and processing of baleen whales by Japanese
fleets in the post-war seasons
SeasonWhales processed :Blue
Fin
Humpback
Total
Blue whale units
Processed products a/:
Whale oil
Frozen and c?ld-stored products
Salted products
Others bf
Total

I 1946-47 II

1947-48

1948-49

1949-50

690
474

710
608

631
1,012

I 1,164

1,318

1,643

817
1,056
67
1,940

1,014.0

I 1,137,0

I

I

927.0
12,260.0
1,832.9
20,385.4
10.8
34,489.1(metric tons)
20,350.0
17,830.0
18,205.3 I 17,620.1
16,535.0
9,048.1
522.7
301.3
55.027.8
45,384.7

1,371.8
27,010.0
24,351.5
13,889.4
365.2
65,516.1

a/ The amounts of processed products shown are the estimates in the field.
bf Includes liver oil, bone meal, blood powder, baleen, etc.

of this table are summarized and shown in Table 3 in comparison
with the production in other post-war seasons. Throughout the period
covered, the catch, and consequently the production of whale oil aswell as the total amount of products have increased year after year,
as the equipments of the floating factories and other various conditionsof operation have been improved. The output of the salted products
has dropped annually, while that of the frozen products risen sharply.
Catch of humpback whales was permitted in the 1949-50 season
on condition that the total catch should not exceed 1,250 whales in
the whole Antarctic grounds. But it was only for the first fortnightof the season that this permission was really effective, for the ban
was again placed on this operation at the beginning of the third week.
Japanese fleets caught 67 humpbacks during the two weeks.
In the 1949-50 season the .Japanese fleets operated in the waters
between parallels 61°S and 69°8 from 116°E longitude eastward to
162°W longitude, which is an area much elongated east and west.
Both fleets passed a large part of the season in the part east of 180°
longitude.
Being assigned to either of the factory vessels in two groups ofthree, the writers investigated, throughout the season, every whale

76

K. MIZUE & T. MURATA

carcass when it was hauled up on to the dismembering deck. The
main items investigated follow :Species, sex and length of whale ; date and time of capture ;date and time of processing.
Body colour.
Scars.
External parasites.
Thickness of blubber.
Kind, amount and degree of digestion of food.
Thickness and colour of mammary glands.
Sex and length of foetuses.
Ovaries (Weight; functional corpora lutea; old corpora lutea;
Graafian follicles).
Testes (Weight and volume).
Vertebrae.
Teeth (in the case of sperm whales).
The result of the investigation has been compiled by these items
and is presented in this report. In every section of this report, that
deals with each of these items, the result is discussed for each speciesof whales. It should be mentioned here that a satisfactory result has
not been reached with humpback whales, because the number caught
was so small and their body lengths were limitted to such a small
range on account of the short period of operation.
The writers would like to acknowledge most gratefully the matchless cooperations of the Japan Marine Products Co., Ltd. and the Taiyo
Fishing Co., Ltd. in the present investigation as well as in the preparation of this report. Hearty thanks are due to Dr. Hideo Omura,
who has kindly helped and guided the writers all through the courseof this study. They are also much grateful to Miss Hisako Jimbo forher assistance in the compilation of the data. A particular mention
should be made of the exertions of Mr. Hiroshi Ando and Mr. Atae
Ihara, who cooperated as the assistants in the laborious measurementof whale carcasses on board the factory vessels.
Catch

In Fig. 2 are shown the localities where the stated number ofwhales were caught by the Japanese fleets during the 1949-50 season.
This chart indicates that far more whales were taken in the eastern
half of the waters where these fleets operated than in the western

77

Biological Investigation on the Whales Caught

half, and that such a large catch as 674 blue and 877 fin whales weremade in a period of 51 days from January 12-March 4, 1950 in that
relatively small area of the eastern waters bounded by 65°8 and 68°
30'8 latitudes and by 162°W and 172°W longitudes. This catch accounts
for 82.5 % and 83.0% of the total catch of the respective species in
the present season, and corresponds to an average catch of 1.04 blue
whale units per catcher day. In comparison, the same average forother grounds was 0.45 blue whale units in this expedition. Furthermore, a higher average would have been recorded for this particularar.ea, unless the catching operation had been curtailed, in order tomeet the processing capacity of the factory ships, so frequently as
was in this season. Though this area was found to be a good whaling ground by the Japanese fleets during the previous expedition, thecatch was not so great in that season as in the present season, because the operations were confined to the part east of l 70°W andnot continued for so many days.
The length frequency of the catch in this season is graphed in
Figs. 3-8 for each species of whales, in comparison with the catch inthe preceding three post-war seasons. The two sexes of blue andfin whales are shown in separate figures.
In the length frequency of either sex of the blue whale, themode for this season has slightly shifted towards large from thosefor the other seasons. But the length frequencies have remained

80o······•···O-·-·-070

0----01949-1950
1948-1949
1947-1948
1946-1947

60

60

40

30
20

10
~

.!

e

;z;"

60

70

65

75

80

JlodY length

Fi~.

3a,

Bh1e whaJe.

MalE:J,

B6

90

K. MIZUE & T. MURATA'/8-

1949-1960f.,

0 -···········0 1948-1949{ \-o-----·-0 1947-1948

; !'

"

1946-1947

r1
!i
,.l

1?
I·.'

,:

I \ iii \ I:

I Vf

i
i

10

i

i

.!

Ii
I

I

i

i

i

i
I

~'.

'•\

'"60

65

70

75

80

90

Biological Investigation on the Whales Caught

10-

1949-195(1

5

.A.

65
Body length .

70

80

75

Fig. 4b. Blue whale. Female.

-110

1949-1950
1948-1949
1947-1948
1946-1947o ........... o1000-·-·-·.00----0

90

80

70

60

60

40

so
20

5G

60

65

'lO

~r1•nithfi$'· 5a.~lFin whale, Mah:,79

K. MrzuE & T. MURATA80

1949-1960
1948-1949
1947-194(,
1946-1947
15

:
)0

'

r

\

\
6

60

70

Fig. 5b. Fin whale. Male.

almost unchanged in both sexes of the fin whale throughout the four
seasons.
As for the humpback whale, the number caught was so small thatany conclusion may not be justified before more data are added throughfuture investigations.
As is obvious from Summary No. 1 through No. 4 (see Appeedixes),in the blue and fin whales the length frequencies of monthly catches
show the approximately same tendencies as those in Figs. 3-6. The
average lengths of the catch of this season are listed below by species
by sexes.

Biological Investigation on the Whales Caught

81

70
1949-1950•·······-·-.. 1948-1949
l>--·-·-0 1947 -1948......-- 1946 -1947

60
60

40

20

10
....o .....

55

60

65

80

75

70

BOdy length in feetFig. 6a. Fin whale. Female.
o - - - o 1949-1950

1948-1949
1947-1948
0 - - - 0 1946-1947
0-----·--·0f\~o----o

15

i \
i i

I
!

I

;

'I

\

i

\
i
i

·,

\
I

i
i

i

·,

/'

\¥·I
.
I
i

.... ft· ....

55
60
)3od;r length in ft.

Fi~. 6b.

70

Fin whale, Female.

75

.80

82

K. MIZUE & T. MURATA
0--·-0~........... Sf-...-- 1'o

-~

J 10

~

•.&...

_,.

~~:~·::::.h...
/,_.;;;>'·-·o..._o..:·· ..··' •40

35

Body length In feetFig. 7. Humpback whale.

0--0

80

......... o

1949-50
1947-48

~--·~

'W

]" 10

s
~

z
40

45

GO

55

Body length in feetFig. 8. Sperm whale.

Species

Male

FemaleBlue whale
Fin whale
Humpback whale
Sperni whale

78.4 ft.
66.2 ft.
42.2 ft.
49.9 ft.

81.2 ft.
69.8 ft.
43.3 ft.
(No data)

And the average lengths of the monthly catches hardly differ
from these (see Summary No. 1 in the Appendix).
These figures for the blue and fin whales are plotted in Figs. 9
and 10 respectively, in comparison with the corresponding averages
in other post-war seasons.
Fig. 9 indicates that in either sex of the blue whale the average
length has been gradually increasing throughout the period in question.
On the contrary, the same of the fin whale seems to have been decreasing gradually in both sexes (Fig. 10).
As for the humpback whale, of either sex, the average length ofthe catch by the Japanese fleets in this season is far above the averages
for the seasons prior to World War II, which were computed for thecatch from the entire Antarctic grounds (Table 4).
·

Biological Investigation on the Whales Caught----- .!j1.~

.,

"
.5
..,

~80

1
g>.

...

..

,.------ -----·,,.,,'--,,_ ______ _----· .!j1.

"

~ 70

83

~

,l'

.5

-:""'-....

I

~

I

/

I

/---

tu..__~~~~~-..-~--.,--~
>
1946
1947
1948.
1949
<
-47
-48
-49
-&O

1946
-47

Fig. 9. Blue wliale.

1947
-48

1948
-49

1949
-50

Fig. 10. Fin whale.

Table 4. Average length of humpback whales taken by
the floating factory whaling i~ the Antarctic,
1934-35 through 1938-39
Average length in feet
SeasonMales
1934-35
1935-36
1936-37
1937-38
1938-39

39.43
40.20
39.77
39.61
37.69

Females(900)(1,256)(2,204)
(781)
(266)

42.06
42.26
41.39
41.97
40.47

(1,027)(1,862)(2,256)(1,289)(617)

Note. Numbers of whales are shown in parentheses.
Source : International Whaling Statistics.

Figs. 11 and 12 show the percentage of male whales in the blueand fin whale catches in the post-war seasons. In the both species,and especially in blue whales, the percentage of males is higher inthe 1949-50 season than in any other post-war seasons.
80.
60

" 40

~"'

~,,. 20

"'
1946
-47

1947
-48

1948
-49

1949
-50

Fig. 11. Percentage of Bh1e
whale male,

1946

1947

-47

-4ll

1948
-49

1949
-VO

Fig. 12. Percentage of Fin. - -- wh~le male,
·
'·

,,

..

K. MIZUE & T. MURATA84

The sex ratio in the monthly catches of blue and fin whales aregraphed in Figs. 13 and 14 for the post-war seasons. In blue whales(Fig. 13), the percentage of males increase as a season advances. This

80
60

~
~:.:.:.:··

r
"

BO

.. .....
_

60

····'

40

j

·~ 20

1949-1950
1948-1949
1947-1948
1946-1947

~ 20

"

p..

DEC.

JAN.

FEB.

40

:;

p..

- - 1949 -1950-·-·-· 1948-1949------ 1947-1948············· 1946-1947
DEC. J.\N.

MAR.

Fig. 13. Percentage of Blue
whale male.

JllAR,

JllAR.

Fig. 14. Percentage of Fin
whale male.

tendency is most conspicuous in 1949-50, and 84. 7 % was reached in
March, 1950. Since the Japanese fleets moved toward east with theadvance of the season in 1948-49 as well as in 1949-50, this tendency
may be regarded as indicating a predominance of males among theblue whales distributed in the eastern grounds. A similar tendency
is also observable to some extent in the fin whales caught in thisseason. In the catch of the humpback whales of this season females
exceeded males in number, as was usual in other previous seasons,with the ratio of 64.2% (females) against 35.8% (males). Whether
this predominance of females in the catch of humpback whales iscaused by chance or is rooted in a preponderance of females in thestock itself, as have been suggested by various authors, is to be
decided through the studies in future.
Body Colour

Body colour of the blue whales has been investigated with regard
to the following three points :Abundance and distinctness of the pale spots.
Abundance of the white flecks.
Distinctness of the white striations.
The data have been analyzed to study the correlations of thesecharacteristics with length of the whale, with sex and with whaling
grounds. In the last case the grounds have been subdivided into twoparts along the 180° longitude, But any of these correlations hiwe

.Biological Investigation on the Whales Caught

been found. This suggests that these characteristics of the bodycolour of blue whales vary from individual to individual, independent
from the factors listed above.
The result of observations is summarized in Tables 5-8. Theseobservations are, in their nature, subject to a certain size of personalerrors of the observers.
Table 5. Abundance of pale spots on blue whales, 1949-50--~-----Class and description

Number of whales

Percentage to total

1 (Very few)
2 (FewJ
3 (Normal)
4 (Many)
5 (Very many)

17
245
394
145
13

2.1
30.l
48.4
17.8
1.6

Total

814

100.0

Table 6. Distinctness of pale spots on blue whales, 1949-50
Class and description

Number of whales

Percentage to total

I (Not distinct)
II (Distinct)
III (Very distinct)

68
507
239

8.3
62.3
29.4

Total

814

100.0

Table 7.

Abundance of white flecks on blue whales, 1949-50

Class and description

Number of whales ---1P~~~-~~tot~-

0 (None)l (Very few)
2 (Few)
3 (Normal)
4 (Many)
5 (Very many)

5
99
273
317
100
22

Total

816

1

0.6
12.2
33.5
38.7
12.3
2.7
100.0

k. MIZUE & T. MURATA

86

Table 8. Distinctness of white flecks on blue whales, 1949-50
Class and description

Number of whales

Percentage to total

0 (None)I (Not distinct)
II (Distinct)
III (Very distinct)

8
390
372
76

1.0
44.1
45.6
9.3

Total

816

100.0

Body colour of the fin whales has been investigated with regard
to the following five points ;Shade of the dorsal colour.
Which side, right or left, of the lower jaw is black ?
Distribution of the dorsal colour over the thoracic body surface.
Presence of the coloured part protruding toward annus.
Unification of the dorsal colour at the base of flukes.
The first item, viz. the shade of the dorsal colour, has been subject to such large personal errors of measurers that the result of themeasurements is not presented here.
The second item was studied in the present investigation, though
it had been well established in fin whales that the left side of theirlower jaw is black and the right side white, because a photograph ina plate of the Discovery Report Vol. I, Plate XXXIV, Fig. 1 hadseemed showing a specimen whose lower jaw is black on the rightside. Since none of the 1,056 fin whales (619 males and 437 females)
examined in this investigation has possessed a white left side of lower
jaw, it is most likely that the aforementioned plate shows the negative print of the photograph.
.
The results of the investigations into the other three items havebeen analyzed, as in the case of blue whales, respecting. their correlations with body length, sex and the whaling grounds as subdivided
into two parts along the 180° longitude. Any of these correlations,
Consequently, the variation in thesehowever, were not found.
characteristics of the body colour of fin whales seems to be nothing
more than the individual variation. The results of the observation
are summarized in Tables 9-11.
Body colour of humpback whales has been recorded according to
Lillie's classification, and the result is summarized in Table 12.

Biological Investigation on the Whales Caught

87

Table 9. Distribution of dorsal colour on the thoracic
body surface in fin whales, 1949-50

I Number ofType of distribution

I
j

Percentage
to total

whales- - - - - - - - - - - - - - - - - - - - - --------- - - - - -L. (Dorsal colour reaching lower than normal)
N (Normal)
U (Dorsal colour confined to regions upper thanin normal cases)- - - - - - - - - ----

344
392

32.6
37.1

320
--~----·-----

Total

30.3
------

1,056

100.0

a/ The "normal" type of distribution is defined as such that the dorsal colour
reaches down to the llth to 13th ventral grooves from the umbilicus.
Table 10. Presence or absence of the protrusion of dorsal
colour towards the annus in fin whales, 1949-50
Presence or absence of protrusion+ (Present)- (Absent)
Total

Number of whales

Percentage to total

819
237

77.6
22.4

1,056

100.0

Table 11. Unification of dorsal colour at the baseof flukes in fin whales, 1949-50
Presence or absence of unification

Number of whales

Percentage to total+ (Present)611- (Absent)

445

57.9
42.1

1,056

100.0

Total

None of the humpback whales dealt with in this investigation
belongs to Class 4 (black all over the body), though many individualsof this Class have been reported among the catch from the waters ofSouth Africa and South Georgia. The result of the present investigation almost agrees with the findings made by Matsuura as well as
Omura, in their investigations of Area V, for the approximately samewaters covered by the present study. Such Agreement seem::! quite
natural, even allowing for the considerably large personal errors which
are necessarily connected with the measurements by different investigators.

88

K. MIZUE & T. MURATA
Table 12. Percentage frequency of body colour classes
in humpback whales, 1949-50
Body colour class a/

Males

Females

Total

1Intermediate between 1 and 2
2
Intermediate between 2 and 3
3
Intermediate between 3 and 4
4

12.5
12.5
16.7
54.2
4.1

11.6
16.3
2.3
44.2
11.6
14.0

11.9
14.9
7.5
47.8
8.95
8.95

o.o

o.o

Whales examined

24

43

67

o.o
o.o

a/ According to Lillie's classification. Descriptions of classes follow : "1"dorsal colour not protruding onto lateral body sides; "2"-dorsal colour protruding onto lateral body sides (The protrusions of dorsal colour generally occur
between base of flipper and posterior end of ventral grooves, on the lateralsides opposite the posterior end of dorsal fin, and at the base of flukes ; "3"paired (right and left) protrusions of dorsal colour uniting on the ventral
body side; "4"-black all over the body.

On the other hand, the present result is also analogous to Matthews' observations in the New Zealand waters. This fact implies
the humpback whales in the latter waters belong to the stock thathave been exploited by the Japanese whalers in the Antarctic, and at
the same time confirms the northsouth migration of this species whichhave been established by marking experiments. Body colour of thewhale generally have little bearings on the taxonomy of whales.
Nevertheless, the body colour of humpback whales seem worth thefurther investigation, because it may possibly be utilized as a key
characteristic in discriminating the races, if any at all, of this species.
Analysis of the data of the present investigation does not showthat there is any correlation between the body length and body colourof the humpback whales, but indicates that the intermediates between
Class 2 and Class 3 are prevalent in all length classes of both sexes.
Whitish Scars

Whitish scars have been investigated respecting their abundance
and their old or new. The result obtained implies nothing but thewell established tendency that more scars are found on larger whales
than on smaller ones. It is advisable to examine the method now inBiological Investigation on the Whales Caught

89

use critically before resuming the investigation on this characteristic
in next season.
Table 13 shows the abundance of white scars in the heigher andTable 13

Number of blue and fin whales in each abundanceclass of whitish scars, 1949-50
a. Blue whales, males.
Abundance class a/

Length of whale
78 feet or under
79 feet or over
Total

0

I

II

III

IV

Total

0
0

42
14

139

96
153

4

105

3

281
275

0

56

244

249

7

556

b. Blue whales, females.
Abundance class a/
Length of whale
81 feet or under
82 feet or overTotal-------- -

0

I

II

III

IV

Total

0

17
4

21
81

1
8

121

0

82
46

21

128

102

9

260

0
_ c _ __ _ _~139_ _ _c___ _ _c__._ _ _c___ _ _o __ _ __c. Fin whales, males.
Abundance class a/
Length of whale
66 feet or under
67 feet or over

0

I

II

III

IV

Total

0

30
5

163
110

140
149

8
14

341
278

0

-------------1--------,-----

Total

0

273

35

289

22

619

d. Fin whales, females.
Abundance class a/
Length of whaleI

I

70 feet or under
71 feet or over
Total

I
!

I

I

II

III

IV

I Total

0
0

29
5

149
83

55
103

4
8

237
199

0

39

232

158

0

I

I

I

12

a/ The abundance classes of whitish scars are defined as follows :"I" very few; "Il"-few; "lII"-many ;. "lV"-very many.

I

I

436

"0"-none ;K. MIZUE & T. MURATA

90

lower length classes of the two sexes of blue and fin whales.
Not so many white scars were found in humpback whales as inblue or fin whales, and they were mostly round in shape, unlike thosefound on the latter two species.
External Parasites

In Table 14 are shown, by species of whales, the number andpercentage of the whales which have been recorded in the present
Table 14. Infection with Pennella spp., 1949-50
InfectedSpecies of whaleBlue
Fin
Humpback
Sperm

Whales examined

817
1,056
67
172

Number of whales

Percent

5
6
0

0.6
0.6

o.o

3

1.7

investigation as being infected by the copepod, Pennella balaenopterae.
The percentage infection in the blue and fin whales has been verysmall, being slightly exceeded by that of the sperm whales. Percentage
infection has been zero in the humpback whales. But the figures inthis table are probably somewhat lower than the true figures, for theparasites as small as this species may have been overlooked at night.
The shoulder and the back are the major body parts infected by thisspecies. Head was infected in one individual.
A lower percentage infection has been recorded for the blue
whales in this season than in Omura's survey over Area V. For thefin whales, however, the percentages are almost same in the two
investigations. Pennella is commonly found on the whales captured in
the temperate waters, but it gradually falls off the host in the Antarctic. Now that this parasite occurs in the Antarctic waters on theschooling sperm whales more frequently than on the old lone bulls aswell as on the blue and fin whales, we may conclude that theseschooling sperm whales are migrating over a considerable range ofwaters.
Only one individual infected by this parasite has been reportedby Matthews, out of 38 sperm whales which he studied at Durban.
Table 15 shows the number and percentage of the whales infectedby the cirripeds, Coronula spp. and Conchoderma spp. In the hump-

91

Biological Investigation on the Whales Caught

Table 15. Infection with cirripeds, 1949-50-------·-·-------:[

Species of whale l Whales examined

I

[
I

Blue
Fin
Humpback
Sperm

I

I
I

I

I

Infected withCoronula spp,\

Conchoderma spp.

I Number \ Percent \ Number
817
1,056
67
172

I of whales
I
i

I

I
I
I

3
15
67
0

of whales

0.1
0.4
100.0
2.3

1
4
67
4

0.4
1.4
100.0

o.o

I

I Percentback whales, the percentage infection has been 100% for either ofthe genera. The percentages are much lower in the blue and fin
whales, and the blue whales show a little smaller percentages than
the fin whales. In sperm whales, the percentage infected by Coronula
has been zero, while the same by Conchoderma 2.3%.
Both of Coronula diadema and C. reginae have been found on
C. regniae on blue and fin whales.
Table 16 shows the percentage of the whales infected by the
Table 16. Infection with Cyamus spp., 1949-50
InfectedSpecies of whale

Whales examined
Number of whales

Percent

20
52
56
47

2.4
4.9
83.6
27.4

----------

Blue
Fin
Humpback
Serm

817
1,056
67
172

amphipods, Cyamus spp. Though the table gives 38.6% as the percentage infection of humpback whales, it seems most probable that
all the humpbacks handled in this study have been infected, for Cyamus
are very easily overlooked.
For the same reason, it is also very likely that ~the percentages of infection of blue and fin whales are underestimated in Table 16.
In the blue and fin whaJes, Cyamus are hidden so deep in the posterior
parts of the ventral grooves that they may be easily left unnoticed,
unless these parts are examined closely.
The percentage infection has been 27.4% in the sperm whales.
Various types of Cyamus, probably involving a considerable number

K. M1ztrE & T. MURATA

92

of new species, have been collected in this investigation. A detailed
report will follow on this subject.
Diatoms, as external parasites upon whales, differ from the foregoing animals particularly in that their attachment properly occurs
in the Antarctic waters. The diatoms; once attached on the whale,
rapidly multiply to form a yellow-brown "skin film" over the bodysurface of the host, as long as the host remains in those waters.
But "skin film" falls off the whale in the waters of low latitudes. It
has been estimated that a period of about one month elapses between
the arrival of whales within the Antarctic Zone and the formation ofvisible diatom film upon them.
Karcher has already reported that the percentage infection with
diatoms differs from one area of the Antarctic Ocean to another.
The percentage infection for the waters presently covered by theJapanese fleets has been lower than Karcher's figure for Area II, buthigher than the same for Area III ; and it resembles the former figurein the general trend. Karcher's data indicate the percentage infection
is higher in the adult whales than in the immature. His result also
shows, in agreement with the present investigation, that the fin whales
are more liable to infection with diatom film than the blue whales.
We may conclude from these evidences that male whales arrivein the Antarctic Zone earlier than females, and the mature whales
earlier than the immature.
The very low percentage infection in the humpback whales isprobably due to the fact that this species was fished for only in theearlier part of the season. It is noteworthy, however, that an infection as high as 75.5% has been recorded for the sperm whales, inspite that the operations for this species was confined within the periodprior to the baleen whaling season, viz. from November 25-December
19, 1949.
Table 17, Infection with the diatom film, 1949-50
Speciesofwhale'~-~In_f_ec_t_ed_ _ l,If'

Whale ,examined NumberofwhalesI

I Percent_;_;_:e----i--1-,~-~-:-I'--:-~~- :~:~
Humpback
Sperm

67
172

I

1
129

1.5
75.5

['1

I

Males

Fem.alesWhales I Percent I Whales ,' Percent

i examined, infected examined: infectediii:~~ I .::::!:: I ~~::

24
172

-

1

1

0.0
75.5

43

I

2.3

J

-

Biological Investigation on the Whales Caught

93

Now, assume the blue and fin whales caught in December andsperm whales caught in November showing thick diatom film on theirbodies to have remained in the Antarctic all the previous winter.
Table 18 gives, by species of whales, the number and percentage ofsuch whales in the catch of this season.
Table 18. Occurrence of the whales which have spent
the 1949's southern winter in the Antarctic a/in the catch in December b/, 1949
Species of whale

Whales examined

Whales spending 1949's winterin the Antarctic
NumberBlue
Fin
Humpback
Sperm bf

66
101
57

5
0

22

2

I

Percent
3.0
5.0

2

o.o
9.1

a/ The definition appears in. the text.
bf In the case of sperm whales, the catch in November. 1949 was examinedin stead of that in December, 1949.

70- - t>"·-·······- Sf-

70

-t>"
••••••••• £j2.

----- To

60
50

40

-GO

30

30

20

20

10.

DEC. JAN. FEB. MAR.

Fig. 15. Monthly infection rate
gf Diatom 9n Blue whales

DEC. JAN. FEB. llf.A:R.

Fig. 16. Monthly infection rate
9f Diatom on Fin wha.lesK. MIZUE & T. MURATA

94

/
70
60

,/
·----- Sperm whale mate

- - Humpback whale female
50
40
30

..

.,

~

20

ii
lil
p. 10

'

The figures in this table are smaller
than Karcher's figures for Area II, butlarger than his figures for Area III.
Much interesting resl'l.lts will be obtainedby investigating the diatomaceous infection on the whales in the Ross Sea,
provided that the entrance to that sea
is so open as to permit the operationsof the whaling fleets therein •Thickness of Blubber

The thickness of blubber has beenmeasured at the following two parts ofFig. 17. Monthly infection ratethebody of every whale caught, viz. :of [Diatom on Humpback andPoint
1 ; the point on the mid-lateral
Serm whales.
line, where it intersects the vertical line
passing posterior end of dorsal fin.
Point 2 .; the point on the dorsal line, where it intersects thatcross-section of the body passing ears and perpendicular to the bodyaxis.
Since Point 1 can be located in each whale pretty accurately, andthe thickness of the blubber around this point is uniform, the measurements at this point are well comparable among the whales. On thecontrary, a slight deviation from Point 2 will result in a fairly large
error of the measurement; this is especially true in the sperm whales.
Once the whale carcass is laid upon its back on the dismembering deck,
it is hardly possible to measure the thickness of blubber at Point 2
accurately. So that, it seems advisable to discontinue the measurement at this point.
In Figs. 18-21 are shown, by species, the average thicknesses ofthe blubber at Point 1 and 2 of male whales of stated body lengths.
In blue and fin whales, the thickness of blubber at Point 1 is larger
than the same at Point 2, and both are increasing gradually withbody length (Figs. 18 and 19). Data on the humpback whales havenot been many enough to justify any conclusions (Fig. 20). The increase in thickness of blubber, which is associated with the increasein length of the whale, is not so conspicuous in the sperm whales asin the foregoing species (Fig. 21). In Fig. 21 the measurements at
Point 1 show an increase, though slight, with increasing body length,
DI!::C . .JAN. FEB. MAR.

Biological Investigation on the Whales Caught

95

Point 1
. 12

!i
"
~

·: 11

:a 10

7
6

60
1

Body length

Number of whales

Fig. 18. Average blubber thickness in Blue male whales.

~

Point 1

.5

Point 2

.

]

..o..
,,, ....IY"'"'.,'O",.

,.._ .. _....... .Q\•'r:/f,';;;/p---d'

'S

~

"

:a

~

'.lr' .1/
4.I-----~-~..-..,.-~~-.-~~-~..-...-...--.--.-~,..-,,..-,~

Body length in feet
Number of whales

l

60
65
70
3S131G396695J,06B987G224 9

6

1

1

Fig. 19. Average blubber thickness in Fin male whales .

-

• 12

5

"
~

·- 11

z

Point 1

D--·-· Point 2

10

'S

~ 9
'\'.i
;,;! 8 L...--.-~~-..-..-...--.--'40~

Body length In fe.et
Number of whale

Fi~.

5

1

45

2

4

6

4

2

l

20. Average blubbsr thickness in male Humpback Whales,K. MIZUE & T. MURATA

96/'"· \

Point l22

Point 2

: \

21

''

,'~
18

i

,'

I

:

\

;

t

.,

'

/A\,

'b,.

\

\

I

/ \
\/

\

/

A.,

I

''ff

'

I

i

;~,'Q.
19

''

'

,A._
y<"'

:
'"

''
'

''

'I

'I ''
' ',

l

\:

:i

Body length
Number of whale

Fig. 21.

~

3 6

W

3 D ll W D 00 00 IB W g

M
4

.
1

2

Average blubber thickness in Sperm whales.

but the values at Point 2 appear to decrease toward larger bodylengths, though the result regarding Point 2 are not always reliable
on account of the large errors of the measurements. In general, thethickness of the blubber in the Antarctic male sperm whales does notincrease with the length of the whale so conspicuously as in the baleen
whales.
In contrast with blue and fin whales, the sperm whales show
larger thickness of blubber at Point 2 than at Point 1 ; and the
humpbacks, too, show the same tendency.
The thickness of the blubber of female whales differs considerablyaccording to whether the whale is pregnant or not. In Figs. 22-24
are shown the average thicknesses of the blubber of female blue, fin,and humpback whales of stated body lengths, and distinction is madebetween pregnant and not pregnant females.
These figures clearly indicate that the blubber of female whales,
like that. of males, adds in thickness as the length of the whale increases.
Humpback whales of the two sexes are well matched with blue
whales of the corresponding sexes in the thickness of blubber. In
the females of blue and fin whales, like in their males, the blubber isthicker at Point 1 than at Point 2.

Biological Investigation on the Whales Caught

97jp.,,','d,."A','V,

13

'

}2

r. J

'

....Q •

i.O-····~ .. ~···..•••o--··...o.· .....v./.../·f

Total
Pregnant whaJes
Not p1·e~~nant wh!l!es
A = Body length in feet

B = Number of pregnant whalen
C =Number.of not pregnant whales

Fig. 22 a.

Point 1.

Average blubber thickness at Point 1,
Blue female whales.

14

13
12

•

11

10

8

Fig. 22 b. Point 2.
10........_\

E
<>
.E
~

" 8
""""
;;;
~

-

~

0

"'m

.........

"" 6

Total

whales·~--· Pregnant
Not pregnant whales

]

..c

E-<

A

60

B

c

Fig. 23 a.

2

6

65
2

8

6·

4

11

70
10 18 22 30 38 42 36
9 18 11 18 20 15 .19

so 26
9

7

76
4

5

2
2

l
2

l

Average blubber thickness at Point 1, Fin female whales.

K. MIZUE & T. MURATA

98

9
8

7
6
Ii 5~9-=6~0-=6~1-:6,...2-63..--6....
4 -6y-5_,66,.........6....
7 -6..-8-.6.--9-70.,._,7,....1-7...
2 ...,7,....3-7....
4 -75.--.76~.-77~7..--

Fig. 23 b.

Point 2.

14

13

13

12

12

s 11

. 11

s

"

·=... 10 /
.g"
.t:>

:0
~

'r. . . .

\

"'

l

·."o'...

9

"'~ 8
=

9

/

- - Total•---o Pregnant whales

-'tl

... 7

"
=
10

-~

•···-<> Not pregnant whales

.Q

A

B

c

40

45

6 2 1 8 7 4 4
1 2 1

4

1

Fig. 24 a. Average blubber thickness
at Point 1, Humpback female whales.

Fig. 24 b. Average blubber thickness
at Point 2, Humpback female whales.

In Fig. 25 is shown the change in the relative thickness of blubber
during the season, for different species of whales. The relative thickness of blubber has been calculated for each week by species, and isdefined as the ratio, (average thickness of blubber for the weekly
catch)/(average body length for the same catch), expressed in percentage. The first week as shown in this figure corresponds to theperiod from December 22-24, 1949.
Every curve in Fig. 25, though not smooth on account of thesmall samples, generally tends upwards as the season advances.
Most of the curves in the figure show a decline in January, andtend upwards thereafter. The same tendency has been pointed out
in the preceding investigations, though the cause of the decline in
January has not been explained.

Biological Investigation on the Whales Caught

0.60
Blue male.,... ___ o99

Point 1
Point .2

0.45

JI#-----.. --.. . ...er- ..... -~0--- . .

-0.. ...........

.... ---.....----+-- ......... - ___ ,.. ____ .,,./,,,,

0.40

Week 1

2

0.50

II

4

>f<

DEC.

5

6

8

r;

9

>f<

JAN.

10

FEB.

11

~

12

MAR.

Blue female

0.45..............

0.40

2

Week 1

3

4

5

6

7

8

9

12

10

Fin male
0.86,°'"------0--.. - .......... ---- -0------Q,., .........

0.80...,.,,,,,''........

Weak

1

s

2

4

5

8

7

6

9

Fin female

0.40
0.35

...-----. --------------------..,_ ____ ..,.

'•,...... ,,._........

0.80
Week 12------..
,
1011_____ __----..

_,,....

3

4

5

6

7

8

9

10

11

0.85
Humpback male
0.80

Week 1
0.90
0.85

1

2

S

~-~

~
s

Week 1

Fig. 25.

Humpback female

2

Weekly fluctuation of blubber thickness (in % of body length).

Fig. 25 also indicates that, in every species, the blubber is thicker
in females than in males.
Thickness of blubber, as expressed in the percentage to the lengthof whale, is larger in blue whales than in fin whales.
Humpback whales have thick blubbers for their body lengths.

-

112
92

179

293
72

lst half, January

2nd half, January

lst half, February

2nd half, February

lst half, March

rr
R

2.7

37.5

8.3 18.1 11.1 ~5.0

28.3 12.3 19.4 17.1 22.9

33.0 18.4 25.1 11.2 12.3

32.9 21.7 19.6 15.2 10.9

58.9 16.1 11.6 10.7

36.8 13.2 20.6 19.1 10.3

- - - -- - - -

r

rrr

816

35.5 15.0 19.6 14.3 15.9

1,056

15

82

284

5.3

R

-

- -

-

-

-

-

o.c

8.5

13.6115.2 31.8 21.2 18.2-

20.ol 10.o 50.0 20.0

12.5 16.1 28.6 21.4 21.4

- - - - ---- - 66

rrr··-----~--rr- - --- - - - -

r,

---·-

6.0

-

10

56

Whales[ex0
a minedHumpback whales- -- - - -57.6 16.3 11.6--

13.3 13.3 20.0 26.7 26.7

20.7 12.2 19.5 20.7 26.9

66.2 14.4 10.6

3.5

8.0

8.7

390

4.1

1.1

8.4

55.5 20.9 14.1

191
62.6 16.7

4.2

54.3 14.9 13.8 12.8

R

94

rrr

------

0rr

Whalesexaminedr

Fin whales

Note. Except for the columns "Whales examined", the figure in this table represents the percentage of whales showing the indicated feeding condition to the indicated semi-monthly or total catch. The feeding condition (i. e., empty or
filled of the stomach) is classified as follows: R.:. stomach being fuII to the utmost (about 75-100.% filled) ; rrr - stomach
containing large quantity of food, i. e., about 60-75.% fiiled ; rr - stomach containing moderate quantity of food, i. e.,25-50.% filled; r-stomach containing smaII quantity of food, i.e., less than 25.% fiIIed; 0-stomach being empty.

Total

68

2nd half, December

0Blue whales- - - · - - ---- - - - - - -Whalesexamined

Semi-monthly
period----·----·----- - ----

Table 19. Feeding condition of the captured whales by semi-monthly periods, 1949-500......

s:

>

>
>-3

i'l

L1

is:

~

~

f;j

N

~

Q

1oi

Bio1ogica1 Investigation on the Whaies Caught

Stomach Contents

In the Antarctic Ocean the baleen whales are feeding almost exclusively upon Euphausia superba, and are not polyphagous as they
are in the Japanese waters. Fish were found in the stomachs ofsome baleen whales handled in this investigation, but such were veryrare cases. In Table 19 is summarized the feeding conditions of thewhales which were caught by Japanese fleets during this season.
This table refers only to the conditions of the first stomach.
Though this table lists a considerable number of whales which showed
empty first stomach, many of these whales had food in their secondand or further posterior stomachs. And the intestine was filled withfaeces in every whale.
Table 19 also shows that the feeding condition of whales improved
as the season advanced.
Notes were made on the size of E. superba found in the firststomach, and the data are summarized in Table 20. It is seen from
Table 20. Size of Euphausia superba containedin whale stomachs, 1949-50
Size class of Euphausia superba a/
Species of whale

Whales examined
L

Blue
Fin
Humback

I
I

524
441
56

2.5
5.0
5.3

I

M

s

x

88.9
73.2
66.1

6.5
18.1
26.8

2.1
3.6
1.8

Note. Figures in the last four columns represent the percentages of thosewhales to the whales examined, whose stomachs have contained E. superba ofstated size classes. a/ L=over 5cm.; M=4~5cm.; S=under 4cm.; X~all ofL, M and S mixed.

this table that in most of the cases E. superba in the first stomach
belonged to Size Class M (4 to 5 cm. in length). Further analysis of
the data shows that relative occurrences of various size classes of E.
superba were not correlated with the advance of the season.
From late December through January most of the larger femalesof E. superba were seen carrying eggs.
Spermatophores had gone from the thelyca of females by earlyFebruary.
As was mentioned before, fish were contained in whale stomachs
in rare occasions, besides E. superba.

K. MrzuE & T. MURATA

102

In the stomachs of 11 blue and 8 fin whales were found the fish
which Japanese whalers call "Mizu-tengu", which means the "waterylong-nose" in Japanese. This species, which is slender in shape andless than one feet in length, has not been described in the Discovery
Reports.
Six blue and 7 fin whales had Myctophum sp. in their stomachs,
besides Euphausia.
Fishes of Family Nototheniidae were found, together the Euphausia,
in the stomachs of 3 blue whales.
The fish called "Kori-tengu" (which means the "icy long-nose")by our whalers was found in the stomachs of one blue and one fin
whale. This species hardly exceeds 2 feet in length, and the Japanesewhalers have learned nothing of its scientific name.
Apart from the fishes, Paratemisto gaudichaudi was found in one
occasion.
These food animals other than Euphausia, are usually less than
10 in number per whale, if they happen to be present in the whale
stomach. Therefore, their bearing on the nutrition of whales is almost
negligible.
However, their occurrence may have been underestimated in theforegoing descriptions, for a considerable number of them has probably passed unnoticed when they came out of the dissected whale
stomach mingled in a mass of Euphausia.
Thickness and Colour of Mammary Glands

In the female whales mammary glands were examined respecting
their thickness and colour. The thickness was measured at the thickest
part of the organ. Colour of the mammary glands was determinedby assigning it to one of the colour ranks lii:ited in Tables 21-23, ·in
Table 21. Colour of mammary glands in sexually
immature whales, 1949-50
Number of whales
Colour of mammary glands
Blue
Light pink
Greyish ye11ow a/
Reddish yellow
Brownish ye11ow

Fin

Humpback

50

34

1

9
4
2

10
3

0

2

0

0

a/ The commonest colour in the mammary glands of sexually mature whales.

Biological Investigation on the Whales Caught

103

the investigator's judgement. As this method of determining the colour
was considerably subjective, the result may have been biassed to aconsiderable extent. Consequently, the observations by different investigators do not seem readily comparable with one another, though
they are all combined and presented in this section.
Mammary glands are very thin in the sexually immature females.
65 female blue and 49 female fin whales before sexual maturity
were examined. The thicknesses of their mammary glands haveaveraged 2.8 cm. and 2.4 cm. respectively. Maxima· of the thickness
were 5.5 cm. and 3.5 cm., and minima were 1.5 cm. and 1.0 cm., respectively. There was no sign that the thickness of the mammary
glands increases with body length in these sexually immature females.
As for colour, the mammary glands of these females were mostly
light pink (Table 21). Only
one of the female humpbacks caught was sexually
immature, whose mammary
glands measured 3.0 cm. inthickness.
Sexually mature f e. males were divided into
two groups, the pregnant
females and those being
not pregnant.
In theBody length9070
1 No. of whales:.l 3 5 4~8141413~147 6 2 2
pregnant fem ales of theblue and fin whales, there Fig. 26.a. Average thickness of mammary glandof pregnant whales in Blue whale.
was observed a definite increase of the thickness ofmammary glands with increasing body length (Fig.
26). But such correlations
were not studied in thesexually immature femalesof the humpback whales,
since the data had been
scarce for this group.
66
70
76
Body length
The averge thickness
No. of wh:ilea
4 10 13 22 30 38 42 36 30 25 4 2 l Iof mammary gland in the
pregnant females of each Fig. 26 b. Average thickness of mammary glandof pregnant whales in Fin whale.
species was as follows :K. MIZUE & T. MURATA

104
Species of Whale

Average Thickness of
Mammary Glands

Number of Individuals
Examined

Blue whale
Fin whale
Humpback whale

6.2cm.
4.lcm.
5.1 cm.

112
258
87

It is noteworthy that the average thickness for pregnant humpbacks was larger than that for pregnant fin whales. Maximum thickness was 12.0 cm. in these blue whales, 9.5 cm. in these fin whales,
and 9.0 cm. in these humpback whales. Minimum was 1.5 cm., 1.5 cm.
and 1.0 cm. respectively. The result of observations on the colour ofthe mammary glands of these pregnant females is given in Table 22.
Table 22. Colour of mammary glands in pregnant whales, 1949-50
Number of whales
Colour of mammary glands
Blue
Light pink
Greyish yellow a/
Reddish yellow
Brownish yellow
Brown
Red

6
52
41
5
7
1

I

Fin

Humpback

32
123
74
12
17
0

3
30
4
0
0
0

a/ The commest colour in the mammary glands of sexually mature whales.

The table shows that greyish yellow and reddish yellow were themost prevalent among the colours. Pink was almost exclusively associated with the female whales in their first pregnancy.
The data were analized to determine the correlations of the thickness and colour of the mammary glands of pregnant female whales
with the size of their foetuses, i. e., with the time of pregnancy, butsuch correlations have not been established.
Sexually mature but not pregnant female whales have comprised
two physiologically different groups, namely the resting females andthe females having weaned recently. On account of this heterogeneouscomposition, possible correlations of the thickness and colour of mammary glands with body length and the time of pregnancy have notbeen adequately represented for these not pregnant females.
Average thicknesses of mammary glands in these not pregnant
females are listed below by species. These figures are larger thanthose for the pregnant females.

105

Biological Investigation on the Whales Caught

Species of Whale

Average Thickness of
Mammary glands

Number of Individuals
Examined

Blue whale
Fin whale
Humback whale

8.1 cm.
5.1 cm.
7.4 cm.

83
127
4

In these not pregnant females, the maximum thickness of mammary
glands was 25.0 cm. (measured on a lactating female) for blue, 13.0 cm.
for fin and 15.0 cm. (measured on a lactating female) for humpback
whales. The minima were 2.0 cm., 1.5 cm. and 3.5 cm. for the respective species.
The observations on the colour of mammary glands of the r;ot
pregnant females are summarized in Table 23. The tendency illustrated
Table 23. Colour of mammary glands in not p:i:egnant
a/ whales, 1949-50
Number of whales
Colour of mammary glands
Light pink
Greyish yellow bf
Reddish yellow
Brownish yellow
Brown

Blue

Fin

Humpback

6

17
56
39
7
8

0
3
1

43
21

5
8

o'
0

a/ Not includes immature whales.
bf The commonest colour in the mammary glands of sexually mature whales.

by this table ia very similar to the one shown by Table 22 for pregnant females.
It seems that there is some general relationship between colour
and thickness in the mammary glands of whales. Light pink is generally associated with thicknesses less than 4 cm. in the blue whales
and with those less than 3 cm. in the fin and humpback whales. The
mammary glands of this colour and with these thicknesses are foundonly in such female whales which have not paired, or are in theirfirst pregnancy, or have ovulated but not have conceived.
Greyish yellow and reddish yellow are usually associated withmoderate thickness of mammary glands, namely 5-8 cm. in the blue,
4-6 cm. in the fin, and 5-7 cm. in the humpback whale. Mammary
glands showing these characteristic colours and thicknesses are foundin the major part of pregnant females as well as in the resting females. A considerable portion of the mammary glands which were

106

K. MIZUE & T. MURATA

reddish yellow in colour showed thicknesses larger than what was
stipulated above. These are considered to have ref erred to those females which had weaned relatively long before their capture.
Such colours as yellowish brown, brown and red generally occurredin the mammary glands of large thickness, sometimes as large as 25
cm. These mammary glands may be regarded as from suckling f emales or those females which had weaned very recently.
FoetusesIn this section are dealt with the results of observations on the
foetuses and on the pregnant female whales.
In Table 24 are shown the frequencies that the foetuses were
found in the right and the left cornu uteri.
Table 24. Occurrence of foetuses in the right andthe left cornu uteri, 1949-50
Species of whale

I

Number of cases
examinedBlue
Fin
Humpback

---

I

Left
Right
cornu uteri percent · cornu uteri percent

40.2
52.0
43.8

59.8
48.0
56.2

107
250
32

The frequencies that the heads of foetuses were directed toward
the vagina and to the reverse direction are given in Table 25.
Table 25. Position of foetuses in cornu uteri, 1949-50
Number of cases
examined

Species of whales
Blue
Fin
HumpbackOccurrence of foetal positions in percent
Foetal head towards
vaginaFoetal tail towards
vagina

96.6
91.7
85.0

3.4
8.3
15.0

87
205
20

Table 26 gives the foetal sex ratio for each species of whales.
Table 26.
Species of
whale
Blue
Fin
Humpback

Foetal sex ratio, 1949-50
Sex not
determinable(Number)Males
Number50
136
19

Females
I
Percent
I Number I Percent

44.6
52.9
52.8

62
121
17

55.4
47.1
47.2

I
II

(i

1
1

Total
(Number)

112
258
37

Biological Investigation on the Whales Caught

The lengths of foetuses are plotted against
the date of captureof mother whales in
Figs. 27-29, espectively
for the blue, fin andhumpback whales. Average foetus lengths forten days and monthly
periods are also shownin these figures with themarks o anp. @ respectively. The tendencies
appearing in these figures
are similar to those foundby Mackintosh andWheeler.
Maximum foetus
length was 19'0" for theblue, 16'1" for the fin,and 3'0" for the humpback whales. The minimum was 2'2" in blueand 0'31/z'' in humpback
whales. The smallest fin
whale foetus was at thestage immediately after
the conception.
Table 27 gives, bybody length classes, theproportions of the pregnant and the not pregnant females to thetotal female catch. Pregnant females have accounted for 43.1%, 59.0%
and 86.0% of the female
catches of blue, fin andhumpback whales respectively.

107

19

18

•'

17

. ....

16

'

•

I

'
'
'

.

•

•1

15

14

13

'

:

:·

•' .

'

:"t..:
I.• ..:.a

12

·:'

0

I

'/

I

it
/

I

I

10

1
•

''

..
0

I

8 : ••
I

.,,.
/

•

;

: •c;(.
7 :

• •

1 /

~/

:..

9 :·

I

:

:

•r•

;:

:• .11 :
1 /

.~(

•:

•

.:·

4

I

I

•

I

!
t

·:

'
''

I

0

:

/'

I

•

•:

.•

: • ·•
J

lo•

0
•

:I

..

/
I•

I

: -;·

I• • ;. .
11 '

,,,

.,

:•.

.,'

. .. : .

6 :••

'
'
'

'

'

.'

5 '

'

''·

4 :
.

3

''

:
'
'

ttl
0

"';'"'
"

~
;:r

2
I

'

1

''

'

Er

?
- DEC. >-I--- JAN. --->---FEB.-·.,. "'MAR.

Fig. 27. Growth curve of foetus of Blue whales.

K. MIZUE & T. MURATA

108

16

14 •

.

'

I

18

.. ...· ..

'

12

I

'

,'

e

I

, ••
11

e

·: .:··
I:.

: r• tlI• . . -·.:: ! ..: Ii>e•',:.:·.. :··: ......o:.,.: . . .
........

•• ,'• . A'

G•;/>,..>::.: · " .;;'I;: .. · /
/
I

/.,

'

••. •

e

:·

I

e

:

.i.

e

•• e

~· ·~·

...

I

I

:

.

'

...
''

•

.·: ;:
. .:
.. ..
:·

..

0

'

. . .r .. ~ •.

7 '

:

•

:./ ~ ..:. :· . ':• I''• •• a: •.
.. :.. .:·'
;o"i

.•

6

e

+i-~-+-~_,.;...'-·~~'~--.!l·~·~~µ:~o-.-.;~-1-~-:­
I

6

I

.•:·:

T• •:: ' • 0

8.

i••:-D·.i

.

10

.

:

'
'

,.''

I

•:

'

I •

4

.•

..

..

3 '

•

I

....

•

;

~

..

'
'

'

. ..

o

'

I

I

•:

.

'
I

'
'.

DEC.~~ JAN.

_ _,,,___ FEB. --->"'"

MAR.

Fig. 28. Growth curve of foetus of Fin whales.

The proportion of
the pregnant and thenot pregnant females
to the catch of the sexually mature fem ales areshown in Table 28. The
females showing one ormore corpora lutea in
their ovaries were con~sidered as being sexuallymature.
Pregnant females have .amounted to57.7%, 66.8% and 88.1%of the captured sexuallymature females of theblue, fin and humpback
whales, respectively.
These percentages ofpregnant females, whichhave been derived fromthe analyses of the catch,
are probably overestimating the percentage of thepregnant females in thestock of whales in thesea to a considerable extent, because the motherwhales which are accompanied by calves and are
seemingly suckling arenever hunted, thus preventing the not pregnant
females from being represented in the catch
as fully as the pregnant
individuals.
In both of Tables 27
and 28 the females ofblue whales give a higher
pregnancy
percentage

Biological Investigation on the Whales Caught

than those of fin whales. And the percentage pregnancy is very high in humpba9k whales, implying that this species
propagates more rapidly than the otherspecies.
Table 28, which refers to the sexuallymature females, gives a relatively constant percentage pregnancy throughout
the body length classes of each species.
Hence, there are found no such lengthclasses in which the female whales are
more liable to pregnancy than in others.

109

6

<'.,

•

3

..

•

..:..a•:·"" .•,/:)......~::;'l:°O".
I

t?

1

I

I
I
I

&
<.q

I
I
I

;'

Ovaries

::I

t;\

..
O

I•
0

•

-oEc.-~JAN.-;:r

The measurements made on theovaries of every female have included
the weights of the right and left ovary,
the number of corpora lutea, and the

:;·
.....

!""

Fig. 29. Growth curve offoetus of Humpbackwhales.

Table 27. Pregnant and not pregnant whales in the catchof females a/, by length groups, 1949-50
a. Blue whales.
Length in
feet
71
72
73
74
75
76
77
78
79
80
81
82
83

S4

Not pregnant

Pregnant
I
Percent
I Number

I

I
I

I

0
0
0
1
0
2
3
5
4
8
8
14
14
13

o.o
o.o
o.o

12.5

o.o
16.7
33.3
29.4
28.6
53.3
44.4
50.0
53.8
61.9

i

Number

Percent

4
8
7
7
9
10
6
12
10
7
10
14
12
8

100.0
100.0
100.0
87.5
100.0
83.3
66.7
70.6
71.4
46.7
55.6
50.0
46.2
38.1

Total
number
4
8
7
8
9
12
9
17
14
16
18
28
26

Zl

K. MIZUE & T. MURATA

110

Length infeet

Not pregnant

Pregnant
NumberI

Percent

Number

8
14
7
6
2
2
0
1

I

86
87
88
89
90
91
92

50.0
73.7
58.3
100.0
40.0
50.0
100.0

8
5
5
0
3
2
1
0

Total

112

43.1

148

85

o.o

Percent

50.0
26.3
41.7

Total
number

16
19

12
6
5
4
1

o.o
60.0
50.0
100.0

o.o
56.9

I

260
.

a/ Includes sexually immature whales.
b. Fin whales.
Length in
feet

59
60
61
62
63
64

Not pregnant

Pregnant
Percent

Number

Percent

0
0
0
0
0
0
4
10

o.o
o.o
o.o
.o.o
o.o
o.o

2
6
2
8
6
9
11
9
18
11
18
20
15
9
7
5
2
2
0

100.0
100.0
100.0
lOG.O
100.0
100.0
73.3
47.4
58.1
33.3
37.5
34.5
26.3
34.5
23.1
21.9
55.6
50.0
66.7
0.0

31
33
48
58
57
55
39
32
9
4
3
1

179

41.0

437

78

22
30
38
42
36
30
25
4
2
1
1

26.7
52.6
41.9
66.7
62.5
65.5
73.7
65.5
76.9
78.1
44.4
50.0
33.8
100.0

Total

258

59.0

65
66
67
68
69
70
71
72
73
74
75
76
77

Total
numberNumber

13

19

2
6
2
8
6
9
15
19

Biological Investigation on the Whales Caught

111

c. Humpback whales.
Length in
feet

37
38
39
40
41
42
43
44
45
46
47
48
Total

I
I
I

I
t

I
!
i

!
!

I

Pregnant
NumberI

Not pregnant

Percent

Number

Percento.oTotal
number

0
0
0
6
2
2
8
7
4
4
0
4

0.0
0.0
85.7
50.0
66.7
100.0
100.0
100.0
80.0
0.0
100.0

1
0
0
1
2
1
0
0
0
1
0
0

100.0
0.0
0.0
14.3
50.0
33.3
0.0
0.0
0.0
20.0
0.0
0.0

0
0
7
4
3
8
7
4
5
0
4

37

86.0

6

14.0

43

1

Table 28. Pregnant and not pregnant whales on the catch ofsexually mature females, by length groups, 1949-50
a. Blue whales.
Pregnant

Length in
feet

Number

'74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92

1
0
2
3
5
4
8
8
14
14
13
8
14
7
6
2
2
0
1

Total

112

I

I

Not pregnant

Percent

Number

Percent

Total
number

100.0
0.0
66.7
'75 .0
45.0
40.0
61.5
50.0
51.9
53.8
65.0
50.0
73.7
58.3
100.0
40.0
50.0
0.0
100.0

0
0
1
1
6
6
5
8

0
3
2
1
0

0.0
0.0
33.3
25.0
54.5
60.0
38.5
50.0
48.1
46.2
35.0
50.0
26.3
41.7
0.0
60.0
50.0
100.0
0.0

1
0
3
4
11
10
13
16
27
26
20
16
19
12
6
5
4
1
1

83

42.6

195

57.4

13

12
7
8
5
b

I,

K. MIZUE & T. MURATA

112

b. Fin whales.
Length infeet

PregnantI

Not pregnant

Number

Percent

Number

Percent

0
4
10

1
4
4
15
9
17

72
73
74
75
76
77
78

22
39
38
42
36
30
25
4
2
1
1

0.0
50.0
71.4
46.4
71.0
63.8
66.7
73.7
65.5
76.9
78.1
44.4
50.0
33.3
100.0

100.0
50.0
28.6
53.6
29.0
36.2
33.4
26.3
34.5
23.1
21.9
55.6
50.0
66.7

Total

258

66.8

128

64
65
66
67
68
69
70
71

13

19

15
19
9
7
5
2
2
0

Total
number

o.o

1
8
14
28
31
47
57
57
55
39
32
9
4
3
1

33.2

386

c. Humpback whales.
'Length infeet

Pregnant

Not pregnant

Percent

Number

Percent

Total
number

85.7
50.0
66.7
100.0
100.0
100.0
80.0
0.0.
100.0

1
2
1

46
47
48

6
2
2
8
7
4
4
0
4

0
0
1
0
0

14.3
50,0
33.3
0.0
0.0
0.0
20.0
0.0
0.0

7
4
3
8
7
4
5
0
4

Total

37

88.1

5

11.9

42

40
41
42
43
44

45

NumberI

0

I

diameters of the largest Graafian follicle and corpus luteum.
The females which showed any corpora lutea on their ovaries
were regarded as sexually mature, and those showing no corpus luteum
as immature. Figs. 30 to 32 show the percentage of the sexually

113

Biological Investigation on the Whales Caught

00

1-----,1---.---------

Body length in ft.

Fig. 30.

Maturity of Blue female whales.

100------------50.l-----+-----~~~~

60t-------f-----------~

:
:
I

I
I
I

I

I
I

%
60

65

70

75

Body length in ft.

Thiclmosa hlubber in cm.

Fig. 31. Maturity of Fin female whales.

Fig. 32.

Maturity of Humback
female whales.

mature females to the female catch in each length class, respectively
for the blue, fin and humpback whales.
Sexually immature females have accounted for the following per·centages of the female catch :Species of Whale

Percentage of Sexually
Immature Females

Total Females Caught

Blue whale
Fin whale
Humpback whale

25.0;Yo
11.7;?6
2.4;?6260
437
42

Table 29. Total number -0f corpora lutea for all the whales
examined, by ovaries, 1949-50
Right ovary
Number ofwhalesTotalnumber/
Percent
examinedof c. lutea

Species of
whale
Blue
Fin
Humpback

I

137
282
26

750
1,744
97

I

Left ovary/Total numberof c. lutea

Percent

701
1,776
95

48.3
50.5
49.5

51.7
49.5
50.5
-

K. MlZUE & T. MURATA114

In Table 29 are shown the total :numbers of the corpora lutea
which were found on the right and left ovaries of all the female
whales examined. Since the totals for the right and the left ovaries
are approximately equal in every•species, we may well consider thatshows existence of functional corpora luteaoshows absence of
11
11
1- ·average weight of total whales ovaries- - - - average weight of ovaries of other whales
than whales with functional corpora lutea.•....... average weight of ovaries of whales withfunctional corpora lutea

971-----------!
.. ..

5'

I

I

.-·
./v

4

···.......

I

1-----~-,--''-;...--,'<-~.-----'--·_. .__-:_~..__•_____·),-H--:i•.'a···~~·

0:~:~oo-;~•

I0•. z-· . '-l.,,

8 r-------·'"".~'_ _._..._f_•______:~---0

!

if

00

0

• 0 '\......._ __,____
0

•

•
0

0

~!
0

00

•

0

00

,'

'"

\

\~

· · · - - ·o o ......
o . ,, ,I
I
o

-

o

/:

. 0

oo

-

•

; :...... \

0

lo

\I

:/ :

\I

{ •r--------:-kt--~f,.---~--~~~,,-,==~~~;._~:\,-i-,~!r;:_;:...~-~~--0:•:-:.:.:c:~ 1 r--::------~-·1--:w-..f-'....;._ __:•:....;~·___:·:__~"-..':·------~~--...
A
5".:.~~'e;,-::•~-pr~- /• • °::" °':9 ~ O!O m oo
-y.--..0 ...... 00.
-

••

-'

-.

I

.
---

75
Body length in feet

30

85

90

_F'ig'. 33. Relationbetween weight of ovary and body length of J;Jhi,e whale~,Biological Investigation o:r:i the Whales Caught

115•
shows existence of functional corpora lutea
o shows absence offl1111-.. average weight of total whales ovaries~ -.- - averaie weight of ovaries of other whales
than whales with functiohal corpora lutea......... average weight of ovari~.s of whales withfunctional corpora lu~ea

'

/":

/\

60
.Body length in ft.

65

70

'Iii

Fig. 34. Relation between weight of ovary and body length of Fin whales.

corpora lutea develop equally on
both ovaries, though it does notnecessary follow that the rightand left ovaries ovulate in exact
turns.
In Figs. 33-35 are illustrated
the correlation between the weightof the single ovary and the bodylength in the female blue, fin andhumpback whales, respectively.
On these figures the weights of
the right and left ovary wereplotted individually, and the discrimination was made between

shows existence of filnctional corpota lutl!.a·.; shows absence of1'•;- - aversge weight of total whales ovariea- - - - aversge weight of ovaries of other whales
than whalea with functional corpora tut~......... average weight of ovaries of whal~ wi~l>functional corpora lutea
3+-~~~~~~~~~~~~~

/

z

:a

•

"

ilij"

,,

,,- ClllC'

i:

...

'

•..

..l··' ..

- ........ _. ,.., ',..

g,

"<
'<
s·

!"··....... , .....······:..

0/''\..
...

;?;

o..,,.

......

0

..,-o
0

0,

\

Of

ril' ... -0,

o

_,,"-

CD
•

•

40

Body length in ft.

Fig. 35. Relation between weight of ovary;;-and~body- length of llumpback whales.

K. MIZUE & T; MURATA116

the ovaries showing the functional corpus lutetim (black dots) andthose not showing them (white dots). Though the correlation considered has been obscured in these figures by the occurrences of functional corpus luteum in some ovaries, we can still see the generaltendency that the weight of ovary increases with the body length.
In Figs. 36-38 are shown the numbers of corpora lutea in theovaries of the female whales of stated lengths.
Minimum length in the sexually mature females measured 74 ft.
in blue, 64 ft. in fin and 40 ft. in humpback whales. (Measurements
were not made so many on the sexually mature female humpbacks.)_ _ _ Average number •of corpora lutea

40

35

..
30

25

...
. .. ... ..
.. . .
•.. ..
. ....

20

15

.
..
.. .. . ..
.
...........

10

76

85

90

Body length in ft.

Fig. 36. Relation between body length and number of corpora lute~in Bh1e whales.

Biologicai Investigation on the Whales Caught

111

Maximum lengths in the sexually immature females were 84 ft.
for the blue, 70 ft. for the fin, and 37 ft. for the humpback whales.
(There caught only one immature female humpback whale.)Figs. 36-38 show that there is a general increase in numbers ofcorpora lutea with increasing body length, and Figs. 33-35 evidence

Average numberof corpora lut~a

40

35

...
..... . ........~.
. - ....... .
:: ~:. Y.'.:. .. .
...
"•

u.

.

.

"

.. ..• f." - •. ••. -·---!-··......
-/=-~.: :. ·:·

. ,i. -· ;:. .. ..

. •.. •U.:H::-:: :: 0:an ••• """· ••/:.. . .......

. :. ;::~'!':·-·- .........
60

65

=

n;· : :. :: ••= - ••~!!!

.. -IC-"-Utt-=-trf.'IC.,

-

70

75

Body length in ft.

Fig. 37. Relation between body length and number of corpora Iutea
in Fin whales.

the increase in the weights of ovary with increasing body length.
Consequently, we may say that the weights of ovary increases with
the numbers of corpora lutea.

K. MIZUE & T. MURATA

118

In Figs. 39-41 are plotted the .
diameters of the largest Graafian
Average ri.umber
pf corpora lutea
follicle and the functional corpora
lutea of the pregnant females
20
against the lengths their f oetuse_s.
Since the length of foetus gives
15
an accurate estimate of the timeof the last ovulation, we can also•.
10
study in these graphs the correlations of these diameters with
.
:.-:
the
time that has elapsed since...
the last ovulation.
These figures illustrate that0
the diameters of the largest
45
Graafian follicles as well as ofBody length In ft.
the functional corpora lutea reFig. 38. Relation between body length
main fairly constant throughout
and number of corpora lutea in Humpthe foetal lengths, that is, irreback whales.
spective of the time from thelast ovulation. In these analyses, the foetal lengths have ranged between ·2-19 ft. in blue whales, corresponding to 8 1 / 2 -9 1/ 2 months after
ovulation, and from less than 1 ft. to 16 ft. in fin whales, representing
the period from immediately after ovulation to 10 months later.
25

.

. .
.~
. . ......

. .
2&:

•
•

DLunetv of funetlonal eorpofa lutea,.,

Dia.mew of the l&!"geOt araatl&o foUeJ•""...... "

:

\

.

,

'.

""'

10

' ... - ...

00

.. ·.

Body length In fL;Fig. 39.

I5

Relation between body length of foetus and diameters of the largest
Graafian foIIicles and functional corpora lutea in Blue whales. ·119

Biological Investigation on the Whales Caught
JJii&rnt'l!'JQf r.. 1..-ti<>n11lrorrora Jut.ea

JJi•un .. wr uf o,.. larl{eGt gnafian fo!ide

...

.

,

100

I l

f

£

/· "
i

~

Body len!{th in ft.

Fig. 40. Relation between body length of foetus and diameters of the largest
Graafian follicle and of functional corpora lutea in Fin whales.
oDiameter Of functional corpora tutoa
Diameter of the largft61; graaftan folicle

200

16

. .......

150

·-. .
0

090 • •

100

10

3 ti

....i

~;
~
"

0

i:
..<>a "o.!

-

~

6

....
... ...

60.·...:y; :- .

Body length in ft.

Fig. 41. Relation between body length of foetus and diametersof the largest Graafian follicle and of functional corpora
lutea in Humpback whales.

It is likely from the above analyses that the functional corpora
lutea and the largest Graafian follicles of the pregnant fin and blue•

K. M1ZUE & T. MURATA

120

females remain at constant sizes throughout the period of pregnancy,neither swelling nor shrinking. (The conditions in the pregnant humpback whales have not been confirmed, because the observations were
not enough many.)
The diameters of the largest Graafian follicles and the functional
corpora lutea of pregnant females have averaged as follows:

Species of WhaleI

Average Diameter

I

Functional Corpora \ Largest Graafian
Lutea
Follicles

Number of Illdividuals Examined~~~~~~~--~~~~~~~-!-~~~~~~~-~~~~~~~

Blue whale
Fin whale
Humpback whale

17.9cm.
12.9cm.
12.6cm.

45.8mm.
28.4mm.
25.0mm.

112
258

37

The data for the largest Graafian follicles of the not pregnant
whales were analyzed in a similar way, and have led to the almost
same conclusion as was reached concerning the pregnant whales. There
was found no correlation in the sexually immature females between
the diameter of the largest Graafian follicles and the time of capture ;in other words, there was no sign that the largest Graafian follicles
in these whales had shown smaller diameters in the earlier part ofthe season than they did in the later part of it. The diameters of
the largest Graafian follicles of sexually immature whales have averaged as follows :Species of Whale

Average Diameter ofLargest Graafian
Follicles

Number of Immature
Females Examined

Blue whale
Fin whale
Humpback whale

I6.8mm.
5.0mm.
8.0mm.

29
26
1

In the sexually mature females which were not pregnant, thediameters of the largest old corpora lutea were measured. The data
were analyzed to determine the possible correlation of these diameterswith the time of the season. · But the result shows that there is nosuch correlation, and that the sizes of the largest old corpora lutea
remain fairly constant throughout the season without any sign ofshrinkage in the later part of the season. As for the largest Graafianfollicles of these whales, their sizes have not changed appreciably all
through the season, -just as was the case in the same organ in thesexually .immature females.

121

Biological Investigation on the Whales Caught

The diameters of the largest Graafian follicTes of the sexuallymature, not pregnant females have averaged as follows:
Species of Whale

Ayerage Diameter ofLargest Graafian
Follicles

Number of Not Pregnant, Mature
Females ExamindBlue whale
Fin whale
Humpback whale

25.0 mm.
17.0 mm.
22.0mm.

37
63
2

It should be mentioned here that any analyses of the data thatare made in this study with reference to time have much limitations
to their scope, because the data used have only covered a single season,or a period of two and a half months. And the conclusions drawn on
basis of such analyses are mostly tentative ones; this holds true particularly in the discussions in this section.
One of the pregnant fin whales examined showed two functional
corpora lutea in spite of being with a single foetus. Data pertinent
to this case follow :Length of Mother72 ft.

II
I

Location Captured

Date & Time
CapturedSex & Lengthof Foetus

162°44'W66°11'S

February 2, 1950.
5: 00 a.m.

Male ; 12'1" ; foundin the left cornu
uteri.

Number of Old
Corpora Lutea

Weight of Ovary

8

2.4 kg.

6

1.3 kg.

Functional Corpora Lutea
Number

Diameter(Left)

11.0 cm., 10.5 cm.

2····················· ..................... ..................... ......................
(Right) 0

The correlation between the numbers of corpora lutea and theossification of vertebrae was also investigated, with a result as illustrated in Fig. 42. Exactly median vertebrae of the thoracic and lumbar
series were examined. The determination of the degrees of ossification
was subject to a considerable personal error, and the numbers of corpora lutea were considerably divergent in each ossification class. Andso, the average value was taken in each class, and are plotted inFig. 42.
From this figure we may state that, in both blue and fin whales,
the ossification of· both thoracic and lumbar series is not completed atcorpora lutea numbers less than 20, and the physical maturity begins

K. MIZUE & T. MURATA

122

l31ue
F;n

j

i

i

l

j

Humpback

i

I

I

i

I

i

i

I

JO

/

···~

,.,,.

/
NN

· Nn

·nn

na

aa

'16
24
42
22
28
-66464956.48
10:411i62

aA
2!1
·74
·6

AA
42
99

OSsification of Vertebra
No. of Blue whales
No. of Fin whiles
No. of Humpback whales

Fig. 42. Relation between number of corpora lutea andossification of vertebrae.

16.

10

5

... ~
0

10

16

20

. . . . . ...I'--··~--...__.

25

30

No. of corpora Jutel'

Fig. 43. Frequency curve of number of corpora lutea inBlue whales.

123

Biological Investigation on the Whales Caught

10

10

15

20

25

30

35

40

45

6-0

No. of corpora lutea

Fig. 44.

Frequency curve of corpora lutea in Fin whales.

at corpora lutea number of 3 or 4. The
humpback whales examined were so few
that the correlation has not been clearly
represented for this species.
The percentage frequencies of numbers of corpora lutea are given in Figs.
43-45 for the blue, fin and humpback
whales respectively.
Testes20

15

10

The weight and volume of the testes
excluding deferent ducts were measured
in every male whale captured.
·•·•··· .......
·..,
The weights and volumes of the testesof blue whales are plotted against the%lengths of whale in Figs. 46 and 47. The
15
0
25
10
20
distribution of the plots in both theseNo. of corpora Jutea
figures generally agree with the records
Fig. 45. Frequency curve offor the usual years. If we consider thenumber of corpora lutea inmale blue whales with the testes weighHumpback ~hales.
ing 10 kg. upwards as being sexuallymature, only 33 whales or 6% of the male blue whales taken were
sexually immature.
The data for the fin whales are plotted in Figs. 48 and 49 in same
fashions. These figures also give just same features as have beenrecorded in the preceding seasons. Only 30 or 5% of the male fin
whales that were caught in this season were sexually immature, if\A. .

····-..oK. MIZUE & T. MURATA

124

120

110

100

90

80

70

..
60

";

60

-:-:-

..
....

40

:.

-:

.

....
.. ..

..

..
-:
-:;:

80

:.

..

-:

.:.

:.
20

~

~

;.

:.

10

a
m

i

I>

~

•..
6G

~·

71

76

00

85

Body length in ft.

Fig. 46.

Relation between total weight of right and left testes and bodylength in Blue whales.

Biological Investigation on the Whales Caught

125

19
·18

17

16
l&

14

13

12

II
10

9

:~

-

.
.:.

.

- -

~
!t
~

~

1

.

...

:y1;%0

7

I

.

;.

... ··· ·"
60

71

:

:.~

::·.
...
::

~

!

~

~

.

~

i.. ! -_i i
!

.:.

:

•

!

·.i

I

~

:

;

.:.

-:

::
75

80

85

Fig. 47. Relation body length and volume of testes in Blue whales.

5 kg. is taken as the minimum testes weight of the sexually mature
fin whales.
The writers are of opinion that both of the weight and the volumeof testes need not be measured, as one is to give the same result as
the other. And it seems more advisable to choose the weight, forweighing can be done more easily and accurately than measuring thevolume, and, in addition, the data of weight are far easier to handle
than the volume data.
The measurements on the humpback whales are plotted in Figs.
f>O and, 51 in s.ame manners.. .But the data are too s.ca:rce to justify-

K. MIZUE & T. MURATA

126
60

40

..
./

80

20

10

~

.
I

"
~

g.

S'

...

'
60

~

"

'
66

70

Body length in ft.

Fig. 48.

Relation between weight of testes and body length in Fin whales.

Biological Investigation on the Whales Caught

127

10

9

8

.·

7

6

:.
6

-·. - .
:.. ... --.. ... -.....
.... .....
- .
. . -· = .. ~~ i~;f~~--:
...

4

3

2

"

·A···=---::===---== .. - .
=~.. 7.. ..=.. ~.:-_ ~~ ...... -: /:: :- :. ::::
-·

,J _
~

---

~

~:

··.=:· ·::: """"

·~·-~

~

.

. -·
60

65

70

Body length in feetFig. 49. Relation between body length and volume of testes in Fin whales.

any statement concerning the correlation of these measurements withthe length of whale. Such biological characters as the body length·
at the sexual maturity and others, that have already been clarified in
the Antarctic blue and fin whales, remain obscure in the case of
humpback whales. It is necessary to throw light upon these problems
by repeating the investigations in future.
The correlation of the weight of testes with the ossification of

K. MIZUE & T. MURATA

l28
16

10

..
:----·----

..
46

40

40

'
Fig. 50. Relation
between body length
and weight of testes in Humpback
whales.

Blue whale

40

Fin whale~------~~

NN

Na

nn

na

46

Body length in ft.

Body length in feetaaaA

State of O&illfieatlon

AA

Fig. 52. Relation between state of ossification of vertebrae and weight of testes
in Blue and Fin whales.

Fig. 51. Relation between body lengthand volume of testes in Humpback
whales.

vertebrae is shown in Fig. 52.
Humpback whales are omitted
because their number examined
are so small.
The weight of testes is sodivergent in each ossification class,just as the number of corpora
lutea was, that the average weightwas calculated for each class, andwas plotted in Fig. 52. But theobtained correlation curve is far
difficult to interprete, comparedwith the one or the number ofcorpora lutea.

Vertebrae

The ossification of the vertebrae was examined by chipping off
the cartilage layer between epiphys and centrum. But it seems somewhat doubtful that the data obtained by different investigators are
perfectly comparable with one another.
The .correlations of the ossification with the numbers of corpora
lutea and with the weights of testes have been dealt with respectively
in the sections of "Ovaries" and "Testes". The correlation with bodylength of the whale will be discussed here. Figs. 53 and 54 show

Biological Investigation on the Whales Caught

129

this correlation in the blue and fin whales. Body lengths are also
divergent in each ossification class, just as the numbers of corpora
lutea and the weights of testes were. And so, the average length
is computed for each class, and isplotted in these figures.
85

70

80

gi 65
~

J
NN

Na

{
l::r'

s·

...iti'
(!)

nn

na.

aa

aA

State of Ossifl.c.ation

AA

Fig. 53. Relation between state of ossification of vertebrae and body length inBlue whales.

NN

Na

nn

na

aa

aA

AA

Fig. 54. Relation between state of ankylosis of vertebrae and body length of Fin
whales.

According to Figs. 53 and 54 the ankylosis of the vertebrae iscompleted (i. e. ossification class "AA") at the following body lengths:
Blue whales, males
80 ft.; Blue whales, females 85 ft.
Fin whales, males
67 ft.; Fin whales, females 72 ft.
Then, the body lengths at which the ankylosis of vertebrae is completed differ by 5" between the two sexes in both of blue and fin
whales.
If we regard the whales showing the ossification of vertebrae of"aa" or further as physically mature, such whales have accounted for
58% or 470 whales of the blue whale catch of this season, and 57%
or 597 whales of the same fin whale catch.

*

*

*

*

*

*

*

On closing this report, mention should be made of such phases ofthe present investiga.tio'.1 that were not dealt with in this report.
General biological data 1 as were :i;>resented, in this re:port respec~-

130

K. MIZUE & T. MURATA

ing the baleen whales, were also collected on all the sperm whalescaught in the expedition. But they had not been finally compiled by
the time this report was prepared. They are to be dealt with inanother report.
In parallel with the general biological investigation into the whale
carcasses, the writers carried out further specialized studies on the
biology of the whale. The projects of such studies follow :Study on the blood-group in the whale.
Study on the whale food.
Study on the lung of the whale.
Identification of the fishes found in the whale stomachs.
Identification of the whale lices.
Until present the writers have not had time to compile and analyse
the data of these studies. Results of these studies will be publishedwhen the necessary treatments of data are finished.
References
Hvalrodets Skrifter.
International Whaling Statistics.
Karcher: Ueber den Algenbuwuchs auf siidlichen Walen. Zeitschrift fiir FischereiBeiheft 1. (1940)
Kasahara, Hiroshi : The whaling industry and whale resources in the adjacent seasof Japan. Report of the Japan Marine Products Co., Ltd. Research Institute.
No. 4. (1950) (in Japanese)
Laurie: The age of female blue whales and the effect of whaling on the stock·
Discovery Reports. Vol. XV. (1937)
Mackintosh: Distribution of the macroplankton in the Atlantic sector of the Antarctic. Discovery Reports. Vol. IX. (1934)
Mackintosh and Wheeler: Southern blue and fin whales. Discovery Reports. Vol. I.
(1927)
Matsuura, Yoshio: The composition of the whale catch in the Antarctic. Blue whales.
Bull. Japan. Soc. Sci. Fish .. Vol. 8, No. 5. (1940) (in Japanese)
Ibid.: Ibid. Fin whales. Bull. Japan. Soc. Sci. Fish .. Vol. 9, No. 1. (1940) (in Japanese)
Ibid.: Ibid. Humpback whales. Bull. Japan. Soc. Sci. Fish .. Vol. 9, No. 2. (1940) (inJapanese)
Ibid.: On the multiple conception and multiple ovulation in the baleen whales. Dobutsugaku Zasshi. Vol. 52, No. 11. (1940) (in Japanese)
Ibid.: Biological investigation into the whales found in the North Pacific. Whaling
Materials. No. 9, Part 1. (1942) (in Japanese)
Matthews: The humpback whale, Megaptera nodosa. Discovery Reports. Vol. XVII.
(1937)
Norman: Oceanic fishes and flatfishes collected in 1925-1927. Discovery Reports. Vol.
II. (1930)

Biological Investigation on the Whales Caught
Ibid:

Coast fishes, Part HI, the Antarctic Zone.

131

Discovery Reports. Vol. XVI!!.

(1938)

Omura, Hideo: Whaling Manual. (1941) .(in Japanese)
Ibid.: Whales. (1942) (in Japanese)
Ibid.: Report of the biological investigation into the whales found in the adjacentseas of Japan. Published by the Japan Whaling Association. (1950) (in Japanese)
Rayner: Preliminary results of the marking of whales by the Discovery Committee.
Nature. Vol. 144, No. 3659. (1939)
Wheeler: The age of fin whales at physical maturity. Discovery Reports. Vol. II.
(1930)

Ibid.:On the stock of whales at South Georgia.

Discovery Reports. Vol. IX. (1934)