THESCIENTIFIC REPORTS
OF

THE WHALES RESEARCH INSTITUTE
No. 18

THE WHALES RESEARCH INSTITUTETOKYO· JAPANMARCH 1964

THE SCIENTIFIC REPORTS OF THE WHALESRESEARCH INSTITUTE
CONTENTS OF NUMBER 18
Page
K.
Fin whale subpopulations in the Antarctic whaling areas II, III and IV .

FUJINO,lcHIHARA, T.

Prenatal development of ear plug in baleen whale .
S.
Examination on age determination of the fin whale

29

0HSUMI,49

NEMOTO, T.

School of baleen whales in the feeding areas . . . .

89

0KUTANI, T. AND NEMOTO, T.

Squids as the food of sperm whales in the Bering Sea and Alaskan Gulf
S.
Comparison of maturity and accumulation rate of corpora albicantia between the left and rightovaries in Cetacea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

111

0HSUMI,OMURA,123H.

A systematic study of the hyoid bones in the baleen whales . . . . . . . . . . .
M.
Revision of the article "Taxonomical consideration on genera of Delphinidae" in No. 17
TsuvuKI, H. AND NARUSE, U.
Studies on the lipids in brain of black right whale in the northern Pacific Ocean . .

149

NISHIWAKI,

171
173

FIN WHALE SUBPOPULATIONS IN THE ANTARCTIC
WHALING AREAS II, III AND IV
KAZUO FUJINO
Investigation on identifying breeding populations of wild-life is not only ofsignificance as the first step of the stock assessment for management of the commercially exploited animals in fisheries, but also itself provides the biological bases forthe physiological and the ecological studies and for the population genetics. For thispurpose, marking investigations which were initiated by the ' Discovery Committee' in 1932 have been succeeded by the National Institute of Oceanography,
United Kingdom. This program has been continued under a scheme for the international co-operation since 1953 (Clark & Brown, 1957). Bi-lateral investigations
under the immunogenetical concepts were commenced in 1960/61 season (Fujino,1962).
Reviewing knowledges obtained so far in relation to identification of stocks,
major results of marking investigations for the Antarctic fin whales reported byBrown (1954 a, 1954 b, 1962 a and 1962 b) can be summarized as follows. 1)
There distribute one or more populations in each area of the Antarctic whaling
grounds. 2) Different stocks from separate breeding areas mingle in the feeding
grounds each other. 3) The majority do not disperse more than 50° east or westof the positions of marking.
Basing upon the blood typing investigation which was undertaken in the 1960/61
Antarctic whaling season for the first time, Fujino (1962) states that there distributeat least two populations of fin whales which have different incidences of Ju blood
types each other in area III and that this support the items 1) and 2) of the resultsof marking investigations stated above.
When the migratory ranges of different populations overlap each other, situation of problems concerned becomes to be much more complicated. After summarizing results of blood typing study obtained during three seasons from 1960/61
to 1962/63 and of marking investigations undertaken since 1932/33 season, thepresent paper deals with problems in 1) identifying breeding subpopulations, 2)
migratory ranges and rates of intermingling of different populations in the feeding
grounds of the Antarctic, and 3) some problems in physiology and in ecology relating to the differences of population.
The author acknowledges co-operation in collecting and transporting blood
specimens of inspectors, biologists, and officers and crews of the whaling factoryships. Staffs of the Kyokuyo Hogei Company kindly offered some detailed logs
on their whaling operations. The author would like to express his sincere thanks
in using the precious materials which were compiled from a series of publicationsof Mr. S. G. Brown, National Institute of Oceanography, United Kingdom.
Sincere thanks also due to Dr. H. Omura, Director of the Whales Research

K. FUJINO

2

Institute who organized extensive collection of bloods, Dr. E. Matsunaga at the
National Institute of Genetics and Dr. Y. Nose at the University of Tokyo whogave to the author valuable suggestions and advices.
BLOOD TYPING INVESTIGATIONS
Relative incidences of hereditary characteristics, of which the phenotypes reveal
polymorphism, are of worth as genetic marker for identifying isolated breeding populations. Blood type antigen is generally inherited in simple way, so that it is understood to be one of the most useful characters for such analysis. In the present
investigation, Ju blood type system was utilized similarly to that in the previous
paper (Fujino, 1962)
Materials and Methods
Bloods spout out from the cut at the tip of snout or in the palate or
remaining in the heart were collected into 50 ml. plastic bottles. In 1960/61 season,
the fresh samples were used for examination which was made on board Kyokuyomaru no. 2. In 1961/62 and 1962/63 seasons, the samples were collected by inspectors boading on Japanese seven whaling factory ships, and were successively
kept frozen until the examination was undertaken at the laboratory of the '!\Thales
Research Institute, Tokyo. As shown in Fig. 1, localities, where blood specimens
were taken, cover areas II, III and IV, including lower latitudinal portion of area
III of north of 50° south. Number of whales examined and their percentages against
the catch in each year was shown in Table 1. Approximately 6000 fin whales were

Whale bloods

TABLE 1.

NUMBER OF BLOOD SAMPLES EXAMINED IN THE THREESEASONS DURING FROM 1960/61 TO 1962/63

No. of samples
examined*

No. of fin whales
taken byJapanese fleets

1960/61
1961/62
1962/63

1,266 (14.2%)
2, 188 (18.5%)

8,912
11,861

2,483 (23. 7%)

10,475Sum

5.937 (19.0%)

31,248

SeasonRemarks
Tested for fresh samples+}

Tested for preserved samples(Cushing et al., 1959)++* Samples, from which no cells were recovered, are excluded. In addition 21 and 41 whales
were examined in 1961/62 and 1962/63 respectively, but no information was given. Numbersof hemolysed samples are 244 and 240 in the seasons 1961/62 and 1962/63 respectively.
Figures in parentheses show percentages of samples examined against total catch.
+ Examination was made on board Kyokuyo-maru no. 2 only.
++ Collected by inspectors and biologists boarding on Japanese seven whaling fleets.

examined during the three seasons, and this corresponds 19.0 per cent of the total
number of this species taken by Japanese fleets in these periods.
Reagents After being diluted and absorbed, were used the following serums whichwere prepared by immunizing fowls or rabbits intraveneously with Jul type or Ju2positive type erythrocytes of fin whales.

ANTARCTIC FIN WHALE SUBPOPULATIONS

3

Anti-Jul immune fowl serums nos. 47 and 70
Anti-Ju2 immune rabbit serum no. 34
Anti-Ju2 1 immune rabbit serum no. 61
Anti-Ju2 5 immune rabbit serum no. 65
A part of each serum of no. 47 and no. 34, being prepared by injecting the erythrocytes of the north Pacific fin whales, had been used in the previous investigations(Fujino, 1960 & 1962). Serums nos. 61, 65 and 70 were prepared by immunizing
with erythrocytes of the Antarctic fin whales which were taken in 1961/62 season
and were successively stored by glycerol-freezing (Cushing et al., 1959).
Testing methods Test-tube method and slide-glass method were used for blood
typing tests. To treat the large numbers of specimens taken in the 1961/62 and
1962/63 seasons efficiently, were made the following procedures. At first, allsamples obtained during one whaling season were tested by 1 : 10 diluted anti-Ju2
no. 34 or 1 : 10 diluted anti-Ju2 5 no. 65 serums which were in advance sufficiently
absorbed with Jul cells. After being classified into Jul and Ju2-positive groups
by these tests, the samples of the latter group were subdivided into sub-specificities
of Ju2 antigen complex, and were successively identified as heterozygous or homozygous types.
Reagents for subtyping five specificities in Ju2 antigen complex were prepared by absorbing nos. 34 and 61 serums with various subtypes of erythrocytes.
A part of these absorbed reagents, being used for testing 1961/62 samples, were kept
frozen for about one year to be used for 1962/63 samples.
Classification and Genetics of Ju Blood Groups

In the previous paper, Fujino (1962) states that bloods of the Antarctic fin
whales can be classified into three major types of Jul homozygote, Ju1·2 heterozygote, and Ju2 homozygote similarly to those of this species in the North Pacific
TABLE 2.

FIN WHALE JU BLOOD TYPES CLASSIFIED BY SIX KINDS
OF ANTISERA*

Jui homozygote**

Specificity ofreagents**
Anti-Jui
Anti-Ju2 5
Anti-Ju2 4
Anti-Ju2 3
Anti-Ju2 2
Anti-Ju21

I***+

Jui• 2 heterozygotes**

Ju2 homozygotes**l ·21 l ·22

1.2.

l •24

l ·25***

+

+
+
+
+

+
+
+

+
+

7-

+
+
+
+

+
+
+
+
+

21

22

2.

24

2s***

+
+
+
+
+

+
+
+
+

+
+
+

+
+

+

* Cited from Fujino (1963b).

* * Major three types.
* * * Eleven types subdivided by five specificities of Ju2 antigen complex.
by agglutination with the anti-Jul and the anti-Ju2 reagents, including three subtypic specificities in each group of the latter two. Large scale collection of frozen
samples in 1961/62 season made it possible to make further detailed analysis by

4

K. FUJINO

repeated tests, and led to subdivide Ju2 antigen complex into five specificities.
Then the blood types of this species amount to eleven kinds in all as shown in Table

2.
Table 3 shows differential partial agglutinin titres between immune serums
nos. 65 and 61 after being absorbed with various types of erythrocytes. AntiJu25 no. 65 serum absorbed with Jui type erythrocytes agglutinates Jul ·2 1 typecells up to dilution I : 320 and Jui· 25 type cells up to I : 40, and the relative highest
dilution against these two different subtypes of cells is only 8 : I. On the other hand,anti-Ju2 1 no. 61 serum absorbed with Jui type cells agglutinate Jui ·2 1 cells up
TABLE 3. AGGLUTININ TITRES AGAINST SUBTYPIC PARTIAL
SPECIFICITIES IN DIFFERENT IMMUNE SERUMSa)

Anti-fin Ju2 5 serum (No. 65)

cells ofno.
typeabs. by Jui
cells (2K 270)

JO 20 40 80 160 320

JO 20 40 80 160 320

+
-!ft
-!ft
+It
-!ft
+It

+It
+It
+It
+It
+It

**
**

2K 270 Jui
3K 70Jul ·25
3K 148 Jui ·2 4
3K 83Jul·23
3K 127 Jui ·2 2
3K 12Jul·21

20

40

80 160 320

+ +
+

**

+It
+
+It +It++It -!ft +It++It +It +It +It +It +It

***

10

20

* *+ +

abs. by Jui
cells (2K 270)

unabsorbed
10

5

+It
+
+It
+
+It +It++It +It +It+It +It +It +It*+It *+ ++It +It++It +It * ++It +It *+It*

Anti-fin Ju2 1 serum (No. 61)

cells ofno.
typeabs. by Jui ·2 5cells (3K 70)~

2K 270 Jui
3K 70 Jui ·2 5
3K 148 Jui ·2 4
3K 83 Jui ·23
3K 127 Jui ·2 2
3K 12 Jui ·2 1b)unabsorbed

2

5

JO 20 40 80 160*+It *+ ++It +It++It+It +It ** + ++It +It +It +It +It +It +It*

abs. byJul ·2 2cells (3K 127)
10 20 40 ... 1280 2560

+It +It +It ...

* +* Positively agglutinated up to dilution I : 2560.
to dilution 1 : 2560 and Jui· 25 cells up to 1 : 5, and the relative titre reveals marked
difference. According to these observations, it was noticed that degree of dilutionof the latter serum (no. 61) should be carefully adjusted to avoid mistyping Ju2 5or Ju2 4 specificities of cells into Ju2-negative types.
As regards the allelic system of Ju blood groups of the Antarctic fin whales,
Fujino (1962) states that no significant difference was seen in the relative incidencesof the major three blood types between the observed and the calculated figures
expected from two equal allelic system. Table 5 shows the observed and thecalculated (parenthesized) figures of frequency of occurrence of the major three
types for each population which are expected from the allelic system noted above.
Both these figures are well consistent each other, and this might support the hypothesis proposed.

ANTARCTIC FIN WHALE SUBPOPULATIONS

5

Relative Incidences of Blood Types and Stock Identification

Existence of local subpopulations as shown by geographical non-random distribution of blood
types In 1960/61 season localities, where blood typing investigation was made,cover mostly the southern part of 50° south of area III ranging from 0° to 70° east
(Fujino, 1962). In the successive two seasons, further informations were added forthis area, and the investigations were extended to the lower-latitudinal portion ofarea III of north of 50° south, eastern portion of area II, and western portion of area
IV (Fig. 1). Table 4 shows the summary of relative incidences of the major threeblood types for different localities obtained during the successive three seasons.
' Lower latitude ' of area III in this table correspond the portion north of 50°
south ranging from 20° to 50° east. Most samples (83.3 per cent) of area II wereobtained from a sector ranging from 0° to 10° west. It can be seen from this tablethat percentage incidences of Ju2-positives (sum of Jul ·2 heterozygote and Ju2
TABLE 4. NON-RANDOM GEOGRAPHICAL DISTRIBUTION OF JU MAJOR
BLOOD TYPE INCIDENCES IN THE AREAS II, III AND IV*
Area III
Major bloodtypes

Area II***

High. latitude

Low. latitude**

Jui
Jul·2
Ju2

692
48
4

3,323
194
16

Sum

744

3,533

% of Ju2-positives

Area IV

Sum

889
33

704
32

5,608
307
22

923

737

5,937

7.0
5.9
3.7
* Summarized data obtained during from 1960/61 to 1962/63.
* * North of 50°S, 20°E to 50°E.
* * * 620 samples out of these were taken from a sector of 0° to 10° W.

4.5

5.5

homozygote) reveal the geographical dine in order of area II>southern part of
50° south of area III>area IV> northern part of 50° south of area III. This factsuggests that the fin whales which distribute in these areas do not belong to one
homogeneous stock, but rather consist of at least two or more populations that havedifferential incidences of the blood types each other.
As noted in the previous paper, percentage incidence of Ju2-positive types
reveals generally to be low figure of approximately 2 percent in the southern part of
50° south of area III, representing that of a population of which the major stock
distributes in area III. Though previously being called as the aboriginal population in area III, this may be more appropriately named as the West Indian population. Superimposed upon the usual daily frequency of occurrence, sharp upward
fluctuations in the take of Ju2-positive whales in the south-western portion of area
III occurred in an intermittent series of days, and the upper limit of Ju2-positive
incidence was estimated from the daily incidences as a constant figure of approximately 30 per cent. These whales were interpreted to represent a part of theAtlantic population which migrates eastwards in the previous paper by basing uponknowledges of marking returns (Brown, 1954). Figures of Ju2-positive incidences

6

K. FUJINO

of 30. 7 per cent for the Atlantic population in Table 5 were drawn by summarizing
data of days when incidence of Ju2-positive types jumped up markedly as noted
above. In the west portion of area IV, Ju2-positive incidence reveals nearly thesame figure as that of the West Indian population, but upwards fluctuations wereobserved in some days. Although these are not so marked as those in the case ofmingling with the Atlantic population, this fact show that another population, which
has some higher incidence of Ju2-positive types than that of the West Indian
population and may be named as the East Indian population, distributes in thisarea. There can be seen some inconsistency in the estimates of the incidence ofJu2-positives between the results of both years in 1961/62 and 1962/63, which might
TABLE 5.

FREQUENCIES OF OCCURRENCE OF JU MAJOR BLOOD TYPESIN EACH PURE POPULATION*
East Indian population
Lower latitudinal West Indian
population
population

Major bloodtypes

Atlantic
population

Jul
Jul·2
Ju2

278 (276.2)
109 (114.2)
15 ( 11.6)

41 (41.8)
19 (17.4)
1 ( 1. 8)

Sum

402

61

% of
Ju2-positives

30.7

32.8

Sum

1961/62

1962/63913 (910. 9)21 ( 23.9)( 0.2)

370
13
0

86
6
0

456 (456.2)
19 ( 18.6)
0 ( 0.2)

935

383

92

475

(6.5)

4.0

2.4

(3.4)

Remark, Figures in parenthesis show those expected from hypothetical major two equal allelic system.
* Summarized from data of days when whales belonging to each pure population were postulated
to be taken in the seasons during from 1960/61 to 1962/63.

be derived from errors in summarizing the data, because they were taken from thelocalities where two different populations mingle each other. Actual figure forthis population might be about 4.0 per cent of average for both seasons or higher.
Precise estimation for this figure could be made by extending the investigation to
the eastern portion of area IV where pure East Indian population may distribute.
In the lower latitude of area III also daily incidence of Ju2-positive types
jumped up significantly in an intermittent series of days against the lower percentagesof the backgrounds of the West Indian population. Ju2 incidence being summarized from data of these days is more than 30 percent which is shown as thefigure for the 'Lower latitudinal population' in Table 5. The Ju2-positive types
incidence is close to that of the Atlantic population noted above, but these twogroups of whales can be distinguished by the differential Ju2 subtypic incidences.
As shown in Table 6, relative incidences of Ju2 1 antigen among total Ju2-positives which can be definitely distinguished by its specificity and the strongest reactivity with reagents from other Ju2-positives are 33.7 per cent (35 out of all 104 Ju2
positives) for the Atlantic population and 50 percent (21 out of all 42 Ju2-positives)
for the Lower latitudinal population, the difference can be accepted to be significant. In Table 6, it is also characteristic that no Ju2 1 antigen has been found in
the East Indian population. Thus it became to be obvious that the four different
breeding populations distribute in areas II, III and IV. These might support theresults of marking investigations described by Brown (1954 a, 1954 b, 1962 a, &

y

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----

30°r I' ~------- - - · -Fig. l. Geographical areas II, III and IV where blood typing investigations were undertaken in the threeseasons during from 1960/61 to 1962/63. Four circles summarize data given in the text and Table 5.
Black sectors correspond relative incidences of total Ju2-positive whales for the Atlantic, the aboriginals
of areas III (West Indian), the aboriginals of area IV (East Indian), and the Lower latitudinal populations. Small circles, triangular spots, and crosses show the localities (noon positions of factory-ships)
where whales belonging to the Atlantic, the Lower latitudinal, and the East Indian populations weretaken respectively.

~

'?-

"" "'

,v

0

c,"-

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K. FUJINO

81962 b), however, in which no remark was given for the existence of the Lower
latitudinal population.
TABLE 6. DIFFERENTIAL FREQUENCIES OF OCCURRENCE OF SUBTYPES IN
JU2 ANTIGEN COMPLEX CONFIRMING EXISTENCE OF DIFFERENTPOPULATIONS*
Ju2-subtypic
specificities

Atlantic
population

Lower latitudinal**
population

West Indian**
population

East Indian**
population

Ju2 1
Ju22
Ju2 3
Ju2 4
Ju2 5

35
21
9
16
23

21
2
7
3
9

19
11
9
10
21

0
9
5
6
4

Sum

104

42

70

24

* Summarized results of 1961/62 and 1962/63 seasons.
**.Including data of days when whales belonging to both of different populations were taken.

Direct evidences showing overlaps ef migratory ranges ef different populations in feeding grounds
Basing upon results of marking investigations, Brown (1962 a) states that in the Antarctic feeding grounds, whales from two separate breeding areas are to be found in
l 9'E

54' s

20' E

2 I' E

54'5

x ~
xx
xx
oox;-xx

0
00
00

x

l

2

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.. .

.

0

~~

~"o

~.·ii

x

3
x
00

55°5

.
l 9' E

20' E

21° E

Fig. 2. Evidences showing mixing of the different populations in the feeding grounds
as revealed by data of days when whales belonging to both the Atlantic and the West
Indian populations were taken in a day. Population differences of whales groupedby three localities where whale carcasses were gathered, drawn by basing upon thelogs in Feb. 23, 1961. Concrete lines with arrow show wakes of factory-ship. Threepoints with Nos. 1, 2 and 3 mean localities where factory ship gathered whales taken.
Crosses, open and closed circles mean localities of capture of individual whales belonging
to groups Nos. 1 (West Indian population), 2 and 3 (Atlantic population) respectively.
(See Table 7).

ANTARCTIC FIN WHALE SUBPOPULATIONS

9association in summer, and Fujino (1962) also states that a portion of the Atlantic
population from area II migrates to area III and mingles with the population
there by basing on the immunogenetical study. No description, however, on
direct evidences for overlaping of migratory ranges of different populations has
been given. Detailed informations in some days when the whales belonging toboth the Atlantic and the West Indian populations were taken might serve as the
direct proof for intermingling of different populations in feeding grounds. Fig. 2
shows localities of capture for 54 whales taken by one fleet in Feb. 23, 1961.
Carcasses of these whales were successively gathered at three points nos. 1, 2 and3 on the wake of the factory-ship shown by concrete lines. Some remarks on thesethree groups of whales are given in Table 7. Number of Ju2-positive whales ·were
TABLE 7.
Locality no.,gatheringwhalescaptured2
3

LOG OF FEB. 23, 1961 SHOWING OVERLAPS OF MIGRATORYRANGES OF DIFFERENT BREEDING POPULATIONS
Blood type
incidencesTimeofcaptureNo. ofwhalescapturedJui

6.5512.45*

24

23. taleWest Indian
population
female

16

10

6

r•k

14

8

6

10.3520.20
13.0020.00

Populations'.J u2-postives belonging to

Adomk
population

Group-composition2
13 {imm.
mat. 11uemm.
lrreg. 4
mat. 10 ovul. O**
rest.

6

i6emm. 2
mat. 14

Atlantic .
female 14emm. 2{preg. 8
populat10n
mat. 12 ovul. 2**
rest. 2*Three out of these captured later (at 14, 16 and 18 o'clock).
* * Having ovaries with functional corpora lutea but lacking fetus.

only one out of 24 examined for point no. 1 group (crosses), six out of 16 for no. 2
group (open circles), and six out of 14 for no. 3 (closed circles). These suggest thatmost whales of point no. 1 group belong to the West Indian population andwhales of points nos. 2 and 3 to the Atlantic population. The later part in therange of time of capture for point no. 1 group overlaps with the early part inthat of no. 2 group. These facts show that groups of whales belonging to different
populations migrate to approximately same locality in the feeding grounds withslight time lags. This is a first example that can be regarded as the direct
evidence for overlaping of migratory ranges of different populations. Further detailed evidences are shown in Figs. 3 and 4. Fig. 3 shows locations of capture ofindividual whales taken in Dec. 12, 1962 as grouped by catcher-boats. Ju2-positive
type incidences were calculated as 27.8 per cent by testing 18 samples (5 Ju2positives) for 26 whales taken by catcher-boats A, B, C, and D, and as 0.0 percent
for 11 whales (alljul) by catchers E, F, G, and H. The former was regarded as
those belonging to the Atlantic population (closed circles) and the latter to the West
Indian population (open circles). Another chart basing on the log in Dec. 14, 1962

10

K. FUJINO

is drawn in Fig. 4 under the similar expression as previous one. There can be seen
characteristic differences between these two figures as follows. Whales belonging
to the Atlantic population were found and captured in the locations southern sideof that for the West Indian population in the case of Fig. 3, but in Fig. 4 whales
belonging to the Atlantic population were found at the both sides of locations for
the West Indian population. While, the blood type incidence is maintained to be
indigenous for each population, so that the observations described above can be
0-------0.-0...,

',, E

G

I'-,

i . . . . . . . o---. . -:,_:":~-----------____ o F'0" ...

1

1

I

I

0

H

A

Fig. 3. Evidences showing mixing of the different populations in the feeding grounds
as revealed by data of days when whales belonging to both the Atlantic and the West
Indian populations were taken in a day. Population differences of whales groupedby catcher-boats, drawn by basing on the logs in Dec. 12, 1962, when 29 whales examinedout of 37 those taken. Open and closed circles show the localities where individual
whales belonging to the Atlantic and the West Indian populations respectively weretaken. These were successively captured from lst catch with alphabet letter showing
different catcher-boats after chasing; All of 11 whales taken by catcher-boats E, F,
G & H were typed as Ju I. 13 and 5 taken by catcher-boats A, B, C & D were typed
as Ju I and Ju 2-positives respectively.

interpreted as the most reliable evidences showing that despite of such interminglingsin feeding grounds the different populations have been completely isolated eachother in breeding from generation to generation.
Boundary of migratory ranges and rate of intermingling Table 8 shows frequency distribution of number of whales daily examined and of Ju2-positive whales occurred inthose. In this table, scattered diagrams are divided into four zones by the threeboundary lines corresponding to Ju2-positive incidences of 50, 33 and 20 percent
respectively, and majority in zones more than 20 percent were identified as those
representing whales which belong to the Atlantic or the Lower latitudinal populations. As stated already the former and the latter can be geographically distinguished each other. In Figure I, are plotted noon positions of factory ships in some

ANTARCTIC FIN WHALE SUBPOPULATIONS

11intermittent days when the whales belonging to the Atlantic, the Lower latitudinal
and the East Indian populations were taken during the three seasons. Small closed
circles show those for the Atlantic population. According to this figure, this groupof whales were taken on a band of ground which runs southeast direction fromthe whaling ground lying south of South Africa and extends to about 60° east, but
did not occur in the catch from the northeastern side of this band in spite of fairly
larger number of whales taken. This might suggest that the above-noted bandmight be interpreted as the east boundary of migratory range in feeding groundfor the Atlantic population. According to the results obtained in the three seasons,
48° E

so· E

q

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G'

~

Fig. 4. Evidences showing mixing of the different populations in the feeding grounds
as revealed by data of days when whales belonging to both the Atlantic and the West
Indian populations were taken in a day. Population differences of whales also groupedby catcher-boats, drawn by basing on the logs of Dec. 14, 1962, when 45 whales were
examined out of 50 those taken. 29 whales taken by E', F', G' & H' were typed
as Jui, so that, were regarded as those belonging to the West Indian population. 10
and 6 taken by A', B', C' & D' were typed as Jui and Ju2-positives and were recognized as those belonging to the Atlantic population.

in the east half of area III corresponding to the east end of the migratory range forthis population distribute tolerable number of the Atlantic population in December atthe beginning of whaling season, but hardly occur after January. Some exceptional records taking this group of whales in this ground, however, were made for eachone day in mid- and late-March respectively in 1961/62 season. Ju2-positive type
incidences in the east half of area II reveal fairly lower figures than those of pure
Atlantic population, so that it can be thought that the West Indian population

12

K. FUJINOTABLE 8.

FREQUENCY DISTRIBUTION OF DAILY OCCURRENCE OF
JU2-POSITIVE BLOOD TYPES
No. of J u2-positives

No. of whales
daily examined
2

3
4
5
6
7
8
9
10
II
12
13
14
15
16
17
18
19

0

2

79

4

95
71

4
5

4

3

8

6

5

9

10

11

12

13

14

83

99

I
I
I

77

'

74
67

~~ -~-r;-1
52

48
26
32

26
20
13
8
2
5

8
11

6

s
4
1
4
2
4

3
3
2
2

L ___ l

2

--.

1
3

I I L---,
2
2 u_ 2 L___ _
3
I '
I
:
I

I

I

I

L---i

L .....
I
,

2

:

100%

~13

~---,

I

L__

2

3

2
4

24
25

2

6
6
12
13

L___ ,

I

I

I

i
L---•

I

:
L___I

J

20

I

7
I

6

I

L__

·1

iL __

2

I

L___ ,

4

!

6

'

----,

SO%

I
I

I

L_,

28

2
5
I
3

L---1
I

I

26
27

61
57
33
38
34
23
18

I

I

LL,

21
22
23

L---

29

I

30

L __

31
32
33
34
35

I

3
I
0
2
3

I

'

I

L __

2
2
5
2

I

2

Sum

I

2

36
37
38

39
40
41

0
2
0

I

LL

42
43

44
4;5

2
0
I

I
0
0
I
0

46
47

48
49
53
Sum

642

77

28

13

7

3

4

0

0

0

2 780

ANTARCTIC FIN WHALE SUBPOPULATIONS

13

disperses to this ground beyond the boundary between areas II and III. To makeclear the west boundary of migratory range of the West Indian population should be
extended the investigation hereafter to the western portion of area II. A part of the\Vest Indian population disperses eastwards to the west portion of area IV andmingles with the East Indian population there. On the other hand, little numbersof East Indian population seem to distribute to area III, but inter-relation in boundaries of migratory ranges between West Indian population and East Indian population have not been made so clear as that between Atlantic population and West
Indian population. As shown in Fig. 1 by small triangles, noon positions of factory
ships in some intermittent days, when the whales of Lower latitudinal population
were taken, mostly occur in the portion, of north of 50° south of area III, ranging
from 30° east to 50° east.
Rates of intermingling of different populations can be estimated from blood
type incidences for each pure population in Table 5 and those in various geographicalgrounds in Table 4. In area II (east half) and the higher latitudinal portion ofarea III (south of 50° south), 16 and 12 per cent of the samples respectively consistof the whales of Atlantic population and the residues are of West Indian population.
As fairly large number of samples were tested for area III, the latter might be accepted to nearly represent actual figure of the population there for the periods ofinvestigation. Rate of mingling of the Lower latitudinal population in the northern portion of 50° south of area III does not reach up more than 4.3 percent. As
precise estimation of blood type incidences for the East Indian population has notbeen made, rate of mingling in the areas concerned should be postponed in future.
INTERMINGLING OF DIFFERENT POPULATIONS AS REVEALED BY
RATE OF EMIGRATION OF WHALES MARKED

To obtain informations on migrations and on movements of whales, materials ofmarking investigations have been dealt in various ways (Brown, 1954 a, 1954 b,
1962 a, & 1962 b). For the purpose of identifying stocks, it might be more effective
to analyse materials as geographical groups than to treat those as signs of movementof individual whales. Accordingly, in this paragraph will be mostly discussed theinter-areal relationships especially the problems of intermingling between areas
II and III where different populations distribute respectively as clarified by blood
typing investigations aiready. Calculations of rate of emigration between different
areas will be made by basing on a method which was applied by the present author
to the north Pacific fin whale stocks previously (Fujino, 1960).
Materials used Number of fin whales taken and number of fin whales marked andsuccessively recaptured in the Antarctic during from 1932/33 to 1961/62 seasons wereused to calculation. Table 12 shows the former figures which were cited from theInternational Whaling Statistics, and Tables 9, 10 and 11 show the latter figures
which were arranged by compiling materials described in a series of Brown's reports(1954, '56, '57, '58, '59, '61 b & c). Number of whales taken and those recaptured
at land stations in South Africa are not included in the figures of these tables. Fig.

K. FUJINO

14

5 shows the summarized results of marking investigations which were made mareas II, III and IV during the pre-war and the post-war seasons.
Methods and practice of calculations 1) Major points of calculations of rates of
emigration between different areas follow those which were described in the previous
paper (Fujino, 1960). For this purpose population sizes of the two different
populations I and II of which the main stocks distribute in the grounds A and B neighbouring each other were expressed as N 1 and N 2 , and their relative abundancesin the grounds A and Bas a and 1-a for the population I and as 1-b and b for the
population II respectively as shown in Fig. 6 diagramatically. To make estimation of figures a and b averaging for the periods of investigations is the purposeof the present calculations.
2) In the light of length of lapse of years from marking to recapture and
TABLE 9.

No. of whales
effecti\'ely

NUMBER OF FIN WHALES EFFECTIVELY MARKED IN AREA II AND
SUCCESSIVELY RECAPTURED, 1932/33 TO 1961/62.
In the seasons of:Recaptured in the area II,
Markedin themarked

-\

war
marks

Post-

war
marks

1932/3'35/6·

j

j

299
572
652
447
34

j

j
-

-

l

'lf/

'5516
j

'50/1
j

'45/6

'40/l

1932/3
'33/4
'34/5
'35/6
'36/7
'37/8
'38/9

200

ND*
ND*

s

S1,1m

Sum

1- 1 - - - I 2- 1 2 2 - - 2 1 - - - - 1 - - 1
2 2 ~ I 2 1 2 8 I 3 1 1- 1 2- 2 2 2 2- 1 1- 2- 1 3-- l
13 5a1 4 4bl _cl J _d> I 2 I I _el 3 _o I 4 2 2 2 3 1 1- - - - - - - - - 1-- 1 - - - - - - - - - - -

34
15
56
51

I

15

4

194516-5213·'53/4'5415'.5516
'5617
'5718
'5819
'59160
'6011
'61/2

114
41
84
23

1

-

2

8

3

a 41

16

1

a

1

2 -

s

1

2

6

s

4

6 -

4

10

4

9 14

6

s

s

2

2

7 200

Recaptured in the area III,

p,.,_

w"'

marks

Postwarmarks\!93213
'3314
'3415
'3516
'36/7
'3718.
'3819
194516-52/3
'53/4
'5415
'55/6
'56/7
'5718
'58/9
'59160
'6011
'61/2

Sum

2

I

Remarks, * ND : No available data. In addition, one, two and three whales moved from area
I were recaptured in c) d) f) g) h) j) 1), in b) e) i) and in a) respectively Also excluding one
and two whales moved from lower latitudes and recaptured from j) and k) respectively. One,
three and two whales which were marked in 1935/36, 1936/37 and 1937/38 respectively with noinformation on area recaptured are excluded. Each one whale marked in area II in 1934/35,
1936/37, 1937/38 and 1938/39 was recaptured in area I, and three marked in area II in 1953/4
also recaptured in area I.

10ANTARCTIC FIN WHALE SUBPOPULATIONSTABLE 10.

15

NUMBER OF FIN WHALES EFFECTIVELY MARKED IN AREA III
AND SUCCESSIVELY RECAPTURED, 1932/33 TO 1961/62
In the seasons of:Recaptured Ill the area II,

No. of whales
effectively
marked

p,,.
war
marks

f

463
285
395
II
15

I934/5
'35/6
'36/7
'37/8
'38/9

I934/5

'40/I

'45/6

j

j

j

- -

-

~;

'50/I

'55/6

j

j

'60/1

!

Sum

3· 4

22

2

I945/6-52/3
'53/4
'54/5
'55/6
'56/7
'57/8
'58/9
'59/60
'60/I
'6I/2

7

I94
I02
Postwarmarks

Markedin the

50.

35
ND*
ND*

- - - -

Sum

2

-

--1

I -

I.

4

3

1-

I
2

I

Recaptured in the area III,

Pro-(
marks
war

1934/5
'35/6
'36/7
'37/8
'38/9

Postwarmarks

1945/6-52/3
'53/4
'54/5
'55/6
'56/(
'57/8
'58/9
'59/60
'60/I
'6I/2
Sum.

-

2
-

2

3

I

2

1

1·
I

2

38&)

I

29
5

4''
6
I9
9
I2

3

2

3

3

4 -

-

-

-

-

2

I..

2

3

2 -

5

6·

4·

9

5

2·

9

7

7 22 3II

5!ff

Recaptured in the area IV,war
P.-c-1

I934/5
'35/6
'36/7
'37/8
'38/9

Postwarmarks

I945/6-52/3
•53/4
'54/5
'55/6
'56/7
'57/8
'58/9
'59/60•60/I• '6I/2

marks

·Sum·

~~==---­'=i- --

2----------------

I

1-

9
2

1-

Remarks, *ND: No available data. In addition, in lower latitude (land stations) were recaptured one in a) in 1937, two and one in b) in 1959 and 1962 respectively and two in c) in
1959. One whale moved from area I is excluded. One, two and two whales, which weremarked in 1957/58, 1954/55 and 1961/62 respectively, with no information for area but recaptured, are also excluded.

16

K. FUJINO

complexity of the factors concerned, calculations were made with priority given
to the pre-war marks and with a prospect obtaining complementary knowledges
from the post-war marks.
3) Pre-war marks shot in area II in the five seasons of 1932/33, 1934/35,
1935/36, 1936/37 and 1937/38 and those in area III in the three seasons of 1934/35,
1935/36 and 1936/37 were used. Marks shot in area II in 1938/39 and those inarea III in 1937 /38 and 1938/39 were excluded from calculations because of few
numbers of the whales effectively marked.
TABLE II.

Peewac (marks

Postwac
marks

NUMBER OF FIN WHALES EFFECTIVELY MARKED IN AR~A IV
AND SUCCESSIVELY RECAPTURED, 1932/33 TO 1961/62
In the seasons of:Recaptured in the area III,No. of whales
effectively
markedMarkedin the19
48
58

1934/5
'35/6
'36/7
'37/8
'38/9

14
2

15
59
ND*
ND•

'40/I
)

1934/5
j

'50/1
)

'45/6
)

'55/6
)

1953/4
'54/5
'55)6
'56/7
'57/8
'58/9
'59/60
'60/I
'61/2

'60/1

!

Sum

-~--(----- 1------------- - - - - - - 2 -

-

-

2 -

-

4

~=

Sum

-· -

-

-. -

-

-

-

-

-

I -

-

-

-

-

-

-

I -

-

-

Recaptured in the area IV,p,e- (wa'
marks

PostWUmarks

4.

1934/5
'35/6
'36/7
'37/8
'38/9

3

1953/4
'54/5
'55/6
'56/7
'57/8
'58/9
'59/60
'60/1
'61/2
Sum

-

-

-

1

2 -

-

-

-

-

-

-

I -

-

-

-

-

-

-

-

-

-

l

2

12

4

2

25

Remarks, *ND: No available data. In addition, were recaptured each one in a) and b) andthree in c) which were marked in the area V. Three whales marked in 1959/60 but with noinformation on area recaptured are excluded. One whale marked in 1955/6 and moved toarea V are also excluded.

4) Post-war marks shot in area II in the season of 1953/54, 1954/55 and1955/56 and those in area III in the seasons of 1954/55 and 1955/56 were used.
5) As the numbers of whales effectively marked in area IV were small,calculations were not undertaken for these marks.
6) Number of whales taken and of those recaptured at land stations inSouth Georgia Islands were made together with those of the pelagic operations
in area II for the calculation.

17

ANTARCTIC FIN WHALE SUBPOPULATIONS

7) The following arrangements were made for various parameters necessary for calculations. a) As discussed in the previous paper (Fujino, 1960), errors
in the estimates of rate of confirming (g) whales as ' Hit ' among those effectively
marked and of rate of recovery of marker (f) from whales actually recaptured do
SOUTH

AFRICA

AREA Ill

ANTARCTICCONTINENT

5:~ L-----"\~7ri----_Jwq

Fig. 5. Summarized results of emigration of marked fin whales between areas II, III and
IV during from 1932/3 to 1961/2 seasons (compiled from reports by S. G. Brown).
Figures in circles with alphabet letters C, R and M show summarized numbers of fin
whales taken, of marked whales recaptured up to 1961/2 seasons and number of fin
whales effectively marked respectively. Figures with arrow mean number of whales
recaptured after moving to the different areas.

populationI

populalion

N,

II

N,

00
Area A

Area B

Fig. 6. Diagrammatic interrelationships between different two populations distributedin the neighbouring two areas as shown by movements of marked whales.

hardly effect upon final results of calculation for the rates of emigrations. Then no
Although materials have not been available, however, it could be assumed that there exist significant differences in the figures off

g- andf-corrections were made.

18

K. FUJINO

between Japanese and the foreign fleets in relation to the methods of treating whale
body especially whether or not utilize meats. Therefore the recoveries of pre-war
marks in the seasons after 1960/61 whenJapanese fleets commenced intensive operations in area III were not included. While, for calculation on the post-war marks,
all recovery up to 1961/62 season was used because of avoiding reduction of numberof data. b) Sufficient materials of age-composition, which can be used to estimate
mortality rates for both pre-war and post-war seasons, are not available. It seems
to be impossible, even if materials were available, to estimate precisely mortality rate
for each year. Then figures 0.10 and 0.05 were arbitrarily used as annual rate of
total mortality and annual rate of natural mortality respectively averaging for thewhole periods of investigations involved. The latter figure was applied as annual
mortality rate to five seasons from 1940/41 to 1944/45 for area III and to the
TABLE 12.

NUMBER OF FIN WHALES TAKEN IN THE AREAS II, III AND
IV DURING FROM 1933/34 TO 1961/62*

Area

1933/4

'34/5

'35/6

'36/7

'37/8

'38/9

'39/40

'40/1

'41/2

'42/3

S. Georgia
II
III
IV

I ,728I, 1152, 178
2,177

836
2,246
7,985
1,368

520
3,375
5,236
548

1,079
1,552
6,004 11,505
5,002 8,297
2,285
6,610

1,307
6,252
5,710
5,540

937
7,840
2,218
574

747
831
49

I, 189776

Area

1943/4

'44/5

'45/6

'46/7

'47/8

'48/9

'49/50

'50/1

'51/2

'52/3

S. Georgia
II
III
IV

632
529

987
679

1,456
4,901
2,800

1,670
4,655
4,382
3,355

2, 1426, 136
6,483
4,654

1,922
4,995
6,457
3,068

1,999
7, 1505, 117
2,940

1,982
5,081
4, 133
4,210

2,007
5,977
7, 122
2,141

1,670
4,551
11,364
1,449

Area

1953/4

'54/5

'55/6

'56/7

'57/8

'58/9

'59/60

'60/1

'61/2

S. Georgia

2,673
7,653
11,459,
2,195

2,746
4,963
13,607
2,790

2,669
6,619
7,088
3,208

2,057
10,697
3,812
291

2,251
5,211
9, 197
3,579

1,291
4,298
9,385
7,277

1,160
4,920
9,307
6,501

1,387
5,223
13,269
2,086

661
6,650
11,8473, 129II

III
IV* Cited from the International Whaling Statistics.

six seasons from 1940/41 to 1945/46 for area IV during the World War II. It was
already discussed in the previous paper that these arrangements hardly influence
upon the final results of calculations.
8) As lapse of years from marking to recapture for the Antarctic investigations is generally longer than that for the north Pacific, to obtain the mean value (r)from rate of recapture for each year of marking was made simple arithmetical
averaging instead of that with weight expressed by formula 6 in the previous paper(Fujino, 1960, p.111).
9) According to the results of stock assessments on the Antarctic fin whale
population (Fifteenth Annual Meeting of International Whaling Commission, June,
1963,), it is obvious that the stock of this species has not been in a stabilized statethroughout pre-war and post-war seasons. For the convenience of calculation for
the rate of emigration, however, number of survivors (C') of initial stocks at the time

ANTARCTIC FIN WHALE SUBPOPULATIONS

19

of marking in the annual catches (C) in successive years were obtained by formula
12 in the previous paper (Fujino, 1960). It can be understood, even if such arrangements were made, from the definition of rate of emigration and formulae 5 and 6
in the previous paper that final results of calculation must be little biased from thoseto be obtained by considering annual stock size fluctuations which were demonstrated by the stock assessment.
Results of calculation and their interpretations Table 13 shows the results of calculations
on the rates of emigration between areas II, III and IV. In this table figures are
TABLE 13.

RATE OF EMIGRATION CALCULATED BY MARKING RETURNSFOR THE PRE-WAR AND THE POST-WAR MARKSa>
Pre-war marks*

Rate ofemigration

r22/rl+ra2

A

B

Post-warmarks

rs"/r22+ra2

0.88 (0.88) bl
0.12 (0.12)

0.90
0.10

0.83
0.17

Taa/ra"+r2a
Tz 3/Ta 3+Tz3

0.93
0.07

0.90
0.10

0.58
0.42

r,•/ras+r4a
T4a/ras+r4a

0.88 (0.88)bl
0.12 (0.12)

0.78
0.22

0.68 (0.77)0l
0.32 (0.23)

r28/r2s+raa+r4a
r 33/r23+ra 3+r43

0.11 (0.10) b)
0.69 (0.61)
0.20 (0.29)

0.08
0.71
0.21

0.32 (0.35)0)0.47 (0.50)
0.21 (0.15)

r.8/r2•+ra•+r4 8

Remarks, Calculation was made for the two cases including (A) and excluding (B) recaptures inpost-war seasons, 1945/46 through 1959/60. a) No calculation was made for recapture ofwhales marked in area IV. b), c) Figures in parenthesis correspond to those excluding higher
rate of recovery for area II in 1940/41 and for area IV in 1959/60 respectively.

shown for both pre-war and post-war marks. The former those are further subdivided into two cases of A and B whether or not including the post-war recoveries
respectively. Figures in parenthesis correspond those for the case excluding materials
for the year when high rate of recovery was recognized. At first the results forpre-war marks will be discussed.
As regards inter-relations between areas II and III, rate of emigration fromareas II to III, r3 2 /r 22 +r3 2 , reveals figures of 0.10 and 0.12 for two cases A and B
respectively, and that from areas III to II, r2 8/r 2 3 +r3 3 , 0.07 and 0.10 respectively. These results confirm the non-random distribution of whales in areas II and
III, saying in other words, existence of the different populations, and show thatapproximately 10 percent of the Atlantic population contribute to the stock in area
III and also approximately same percent of the West Indian population distributeto area II. Definite informations for relative stock size between the Atlantic andthe West Indian populations have not been available. If both populations havecomparable sizes of stocks, however, figures of the rate of emigration from areas
II to III noted above correspond to the rate of intermingling of the Atlantic popula-

20

K. FUJINO

tion in area III which is close to that obtained from the blood typing investigations. The results may lead to obain following informations. Although in areas·II and III distribute the different populations which migratory ranges overlap eachother, the facts that both figures of rate of emigration reveal approximately 10
percent suggest that final surplus and deficit of the stock for each area are inconsequence comparatively small. This might be important as a basic information to make stock assessment for each geographical area separately. Rate of emigration from areas III to IV, r4 3 /r4 3 +r3 3 , ranges from 0.12 to 0.22 which are bigger
than those between areas II and III. Reasons that marked inconsistency was seen
between figures for two cases A and B have not been made obvious.
Rates of emigration calculated from post-war marks reveal bigger figures
than those from pre-war marks. Although no sufficient evidence has been given,
the following probable reasons could be assumed to be concerned. Then it might
be impossible to expect nothing more reference informations from the post-war
marks at present. I) In post-war seasons when marking investigations have been
undertaken, the major whaling grounds in area III moved to the lower latitudes,
so that whales of the Lower latitudinal population contribute to the catches inthis area besides the West Indian population. 2) The Japanese fleets utilizing
whale meats commenced their intensive operation in areas III and IV. 3) Scantiness of whales effectively marked might bring larger errors and some biases.

OTHER BIOLOGICAL CHARACTERISTICS RELATED TO
DIFFERENCE OF STOCKSAs discussed in the previous paragraphs, it became to be obvious that in areas II,
III and IV distribute at least four different fin whale populations. Some biologicalcharacteristics related to the difference of population will be described and discussed
in this paragraph.
Differential Sizes of Group of Whales by Stock

As the numbers of samples daily collected by Kyokuyo-maru No. 2 in 1960/61
season and by Kyokuyo-maru Nos. 2 and 3 in 1962/63 season were generally large,
majority of whales taken in these days can be identified as those of Atlantic population and of West Indian populations by basing on blood type incidences and localities
of capture. In Table 14 are shown frequency distributions of' number of whales
observed' for groups from which whales were taken according to four different
classes of blood type incidences. In this table groups of whales, whichJu2-positive
incidences show zero percent, were regarded as those of pure West Indian population, and those more than 11 percent as groups in which whales of Atlantic population
mingle at fairly high percentages. Comparing these distributions between the twodifferent stocks, in the former the classes less than I 0 whales and more than 41
whales occupy 37 and 21 percent respectively on an average 29 whales, and in thelatter those less than I 0 whales only 5 percent and contrarily those more than 41

ANTARCTIC FIN WHALE SUBPOPULATIONS

21

whales 44 percent on an average 48 whales. This result of observations suggeststhat size of group of whales migrating to the feeding grounds in the Antarctic isdifferent by stocks each other. · Although no available data has been obtained to
TABLE 14. FREQUENCY DISTRIBUTION OF NUMBER OF WHALES OBSERVED,SUGGESTING POSSIBLE DIFFERENTIAL SIZES OF SHOALS BY RACESIN THE FEEDING GROUNDS*
Perc~ntage incidence of Ju2-positive types

No. of whales
observed
1- 5
6-10
11-20
21-40
41-80
more than0

more than II

1~} 37%

~} 0%

~} 5%

:} 42

2'
7 J 75

14}
14 50

!}

~} 25

II}
14 45

12
42

56
48

81

Sum
Average no. of whales

I to 1021

38
29*Basing on the logs of catcher-boats.

discuss what other biological characteristics of the population correlates with thisfact, this may bring some problems to the hypothetical basis on 'the geographicaluniformity of distributing concentration of animals ' in stock assessments.
Natural ~election Related to Blood Types

Many discussions on natural selections related to blood types have been publishedin recent years from the view-points of Human Genetics and Anthropology. Althoughsome informations concerning to relationships between blood types and fertility or
age were noted already by the present author (1963b), additional evidences aredescribed in this section.
Differential rates of pregnancy by blood rypes According to the results of the following
observations, Fujino (1963a) describes for the first time that the fairly strong intrauterine selection of Jul ·2 heterozygous fetuses might occur in whales in relation
to the maternal-feta! incompatibility of blood types and states that incidences of the
TABLE 15.

DIFFERENTIAL PERCENTAGE PREGNANCY BY BLOOD TYPESIN THE ATLANTIC FIN WHALE POPULATION

Blood types

1960/61

1961/62

Sum

Jut
(P 1)
Ju2-positives (P 2)

63.9 (36)78.9 (19)55.6 (18)75.0 ( 8)61.1 (54)77 .8 (27)

0.81

0.74

0. 78

Remark, Figures in parenthesis mean the number of mature females examined.

selection will closely relate to the frequency of occurrence of blood types of the population. The observations include that 1) rate of finding fetuses from mature
females is lower in Ju 1 type mothers than in Ju2-positive types those ; the differences
are statistically significant and that 2) isoantibodies from Jul female donors reveal

22

K. FUJINO

hemolytic property and significant high titres were detected for the isoserums ofJui female donors from which fetus was not found in spite of having functional
corpus luteum in their ovaries and congested uteruses. As shown in Table 15,
observations in 1961/62 season confirm the results of differential apparent rate of
pregnancy noted above.
Blood type and age Table 16 shows relative blood type incidences in connection
with age classes which are expressed by number of laminae layers of ear-plug.
It can be seen from this table that incidences of Ju2-positive types decline andcontrarily those of Jui type ascend in accordance with increment of ages and thatthese trends are statistically significant. This observation suggests that relative
viability between different blood types varies in relation to age classes. As reproducibility lastes to fairly older age classes in this species of whales, these facts can be assumed to play an important role in maintaining blood type gene frequencies in a
population together with the differential rate of pregnancy noted already.
Relation between Intra-uterine Selection and Ovulating Cycle

Basing on knowledges in human genetics, Fujino (1963 b) noted that stages of theintra-uterine selection could be broadly divided into pre- and post-fertilization
TABLE 16.

RELATIONSHIPS BETWEEN AGE AND BLOOD TYPES IN
THE ATLANTIC POPULATION*
Blood types**

No. of laminae of
ear-plugJul

J u2-positives

11-20
21-30
31-40
more than 41

19 (55.9)
13 (72.2)
14 (82.4)
14 (77 .8)

15 (44.1)
5 (27 .8)
3 (17 .6)
4 (22.2)

Sum

60 (69.0)

27 (31. 0)

Remark, *Sum of males and females, 1960/61 and 1961/62 seasons.
relative incidences in percent.
** X 2 =4.98, 7 d.f., 0.70>P>0.50.

Sum
34
18
17
18
87
Figures in parenthesis show

those which probably more intensive selective pressure plays in the former. If
the differential rate of pregnancy shown in Table 15 is actually caused by in partdescending ofrate offertilization inJul type mother whales, it should lead to accelerate successive ovulations in the infertilized individuals. The frequencies ofovulation in a breeding period may be different by blood types of mother whales
and also different on the average by races which have different incidences of blood
types each other. In consequence it must reflect on geographical differences inaccumulating rate of ovarian corpora as noted previously. Table 17 shows thecomparison of accumulating rates of ovarian corpora per two laminae layers of earplug drawn by ovulation-lamination keys (Form D) which were submitted to the
Joint Meeting of the Special Committee of Three and the Ad Hoe Scientific Committee of the International Whaling Commission held in Seattle, December, 1962.

ANTARCTIC FIN WHALE SUBPOPULATIONS

23

Figures for area II in this table were cited from those of Laws (1961). Marked
geographical differences are seen in these figures by area. Materials, by whichthese figures were drawn, base on the observations for ovaries and ear-plugs madeby the several biologists of the Whales Research Institute. Even if some individual
errors are involved in readings, it can be said that the geographical differences are
significant. Among the materials for area III of Table 17, readings for numberof ovarian corpora were made by author himself who served as a biologist on board
in 1960/61 season and those for ear-plug laminae by several staffs of the Institute.
The results show fairly marked differences between west-half and east-half of area
III. It was noted aready (Fujino, 1963 b) that types of frequency distribution of
accumulated number of ovarian corpora at an age class expressed by ear-plug !amine
are not always symmetrical, but are rather different by area. Geographical differences in accumulating rate and type of frequency distributions of ovarian corpora
between west- and east-halves of area III seem to support the concept proposedalready. Fig. 7 shows the analysis of frequency distribution for west-half of area
III, which was presented in Fig. 2 in the previous paper (Fujino, 1963 b), by
normal probability paper. This figure shows that the bimodal distribution for thisarea can be divided into two components which correspond 0.6 (83 percent) and1.4 (17 percent) of average rates of accumulating corpora per two laminae of earplug respectively. According to Fujino (1963 a), possible relationships of rates
TABLE 17. ACCUMULATION RATE OF OVARIAN CORPORA OF THE FIN
WHALES TAKEN FROM DIFFERENT AREAS OF THE ANTARCTIC*
Areas

II

W·III**

E·III**IVv

VI and I

2.80-3.00

2.31

1.91

1.84

1.80

1.60

* Cited from Fujino (1963b).
* * Temporarily divided into the two portions of west-half and east-half at 35 degrees east longitude.
of pregnancy between three blood types for the Atlantic population can be expressed
as Jul ;£Ju2 ;£Jul·2. Basing on the above-noted concept, relative rates of accumulating corpora will be arranged in a reverse order. Therefore it can be thoughtthat one components showing higher accumulating rate (1.4) corresponds to Jul
group of the Atlantic population and another component of lower rate (0.6)
consists of Jui ·2 group of the Atlantic population and also of all kinds of Ju bloodgroups of the West Indian population. Although distribution corresponding to
Ju2 homozygote group of the Atlantic population does not appear clearly as a component in Fig. 7 probably because of its low incidence (less than 2 percent), it might
constitutes a component which may have an intermediate mean between abovenoted two figures. According to Fujino (1963a), intra-uterine selection related
to Ju blood type incompatibility little occurs in the West Indian population becauseof the low incidences of Ju2-positive types, so that it can be assumed that type of
distribution is nearly a symmetrical one at least regarding to Ju blood type system.
By these concepts, relative incidences of the two components of the distribution in
Fig. 7 well consistent with those calculated from rate of intermingling of both po-

24

K. FUJINO

pulations for this geographical area (Fujino, 1962). Thus the quantitative relationships will become to be obvious for a pure population between three factorsof the relative incidences of blood types, the incidences of intra-uterine selection
due to blood type incompatibility, and the rate of accumulating ovarian corpora
in females. These observations and analyses could offer some reliable informations.
%

17%

7

99

95

I

90

µ+u
CJ)

u
c

70

~
u

50

0

30

u
0

>.

g µ-<Y
~

rr

!

10
5

15
10
5
o~~--L__JL_-'----'--'-----'L_-'----'---'-~L::=>=._,____,

2

4

6

8

10 12 14 16 18 20 22 24 26 28

accumulated number of ovorion corpora

Fig. 7. Analysis of the bimodal frequency distribution of the accumulated number ofovarian corpora at an age class of 28 laminae of ear-plug for the west-half of area III
by normal probability paper, showing that this consists of more than one component
distributions (see text).

to an essential problems in ovulating cycles especially to the details in frequency
of ovulation, if simultaneous examinations could be precisely made in blood typing,in counting accumulated number of ovarian corpora and in reading number of
ear-plug laminae for each individual females belonging to a pure population suchas the Atlantic one.
SUMMARY

This paper deals with problems of identification of breeding populations, migratory

ANTARCTIC FIN WHALE SUBPOPULATIONS

25

range of each population and some other biological discussions on the fin whales
taken from the Antarctic whaling areas II, III and IV by means of the blood typing
and the marking investigations. These base upon the materials of approximately
six thousands blood specimens collected by Japanese expeditions during three successive seasons from 1960/61 to 1962/63 and those of recoveries of the pre-war andthe post-war marks compiled from data described in a series of Brown's publications. It was emphasized throughout this paper that the facts of overlap of
migratory ranges of different populations made situations of problems in population study much more complex. The observations and the discussions in the present
paper will be summarized as follows.
1. By the agglutination reactions with immune rabbits' and fowls' serums,
erythrocytes of the Antarctic fin whales were classified into Ju major three groups,
i.e., Jul homozygote, Jul·2 heterozygote and Ju2 homozygote, in which the latter
two were further divided into five subtypic specificities, amounting to eleven kinds
in all.
2. Results of X 2 tests for the relative incidences of the major three bloodgroups for the pure population might support that the hypothetical major two equalallelic system is involved as noted in the previous paper (Fujino, 1962).
3. Non-random geographical distributions of Ju blood type incidences showthat four different breeding populations distribute in the Antarctic whaling areas
II, III and IV which can be named as the Atlantic, the West Indian, the East Indian,and the Lower latitudinal populations. Most of these results might support the
Brown's findings (1962 b), but no specific description has been made for the Lower
latitudinal population. Ju2-positive types incidences were estimated as 30. 7, 2.4,
4.0 and 32.8 percent for each pure population noted above. As regards the latter
two figures, more precise estimates will be expected after conducting further investigations. The Atlantic and the Lower latitudinal populations can be distinguishedby the differential Ju2 subtypic incidences.
4. Direct evidences showing overlaps of the migratory ranges of the different
populations in feeding grounds were described by basing on the logs of days when
whales belonging to both the Atlantic and the West Indian populations were takenin the same day.
5. Boundaries of migratory ranges for some populations in the feeding grounds
were estimated. Whales of the Atlantic population disperse eastwards to area III,and the east side boundary of migratory range of this population was became tobe obvious. On the other hand whales of the West Indian population migrate
westwards to the east-half of area II, but its west side boundary has not been madeclear. Then migratory ranges of these two population overlap in the feeding grounds
each other. Major migratory range of the Lower latitudinal population was estimated from locations of capture to cover a part of area III ranging from 30°
east to 50° east, north of 51° south.
6. Rate of intermingling of the Atlantic population in the whales taken fromarea III was calculated to be 14 percent or less by blood typing data. According
to the rates of emigration calculated from marking returns, approximate 10 percent

26

K. FUJINO

of the Atlantic population disperse to area III, and about 10 percent of the West
Indian population disperse to area II. If the both sizes of the two populations
are comparable each other, these figures show the rate of intermingle for each area
as they are.
7. Significant difference was seen in the frequency distribution of numberof whales observed from catcher-boats between the Atlantic and the West Indian
populations in feeding grounds. Although it has not been made obvious what
factors correlate with this result of observation, it may bring some problems to the
hypothetical basis for the ' geographical uniformity in distributing concentrationof animals ' in stock assessment.
8. Additional data were obtained to confirm the occurrence of intra-uterine
selection due to maternal-feta! incompatibility of Ju blood types for the Atlantic
fin whale population which was reported already (Fujino, 1963 a).
9. Relative incidences of Ju blood types were compared by different age
classes for the samples taken from the Atlantic population. Slight but significant
difference was seen between different blood groups in the relative viability in accordance with increment of ages. This fact was interpreted to play an importantrole in maintaining the blood type gene frequencies in a population together withthe fact noted as item 8 in this summary.
10. Possible influences of the intra-uterine selection to the ovulating cycles
were discussed, and the mechanisms that might bring geographical differences in
the rate of accumulating ovarian corpora were considered as a prelimiary meaning.

REFERENCESBROWN, S.G. (1954a). Dispersal in blue and fin whales. Discovery Rept., 26: 355-84.
BROWN, S.G. (1954b). The movements of fin and blue whales in Antarctic Waters. Norsk HvalfangstTid., 43 (6): 301-9.
BROWN, S.G. (1956). Whale marks recently recovered. Norsk Hvalfangst-Tid., 45(12): 661-4.
BROWN, S.G. (1957). Whale marks recovered during the Antarctic Whaling Seasons 1956/57. Norsk
Hvalfangst-Tid., 46(10): 535-9.
BROWN, S.G. (1958). Whale marks recovered during the Antarctic Whaling Season 1957/58. Norsk
Hvalfangst-Tid., 47(10): 507-7.
BRoWN, S.G. (1959). Whales marks recovered in the Antarctic Seasons 1955/56, 1958/59, and in South
Africa 1958 and 1959. Norsk Hvalfangst-Tid., 48(12): 609-16.
BROWN, S.G. (1961). Whale marks recovered in the Antarctic Whaling Season 1960/61. Norsk HvalfangstTid., 50(10) : 407-10.
BROWN, S.G. (1962a). A note on migration in Fin Whales. Norsk Hvalfangst-Tid., 31(1): 13-6.
BROWN, S.G. (1962b). The movements of Fin and Blue Whales within the Antarctic Zone. Discovery
Rept. 33: 1-54.
BROWN, S.G. (1962c). Whale marks recovered during Antarctic Seasons 1960/61, 1961/62, and in South
Africa 1962. Norsk Hvalfangst-Tid., 51(11): 429-34.
CLARK, R. & BROWN, S. G. (1957). International co-operation in Antarctic whale marking from 1945
to 1957. Norsk Hvalfangst-Tid., 46(9): 513-17.
CusmNG, J.E., K. FUJINO & K. TAKAHASHI (1959). Glycerol-freezing technique as an aid in blood-typingof whales. Sci. Rept. Whales Res. Inst., 14: 89-100.
FUJINO, K. (1960). lmmunogenetic and marking approaches to identifying sub-populations of the northANTARCTIC FIN WHALE SUBPOPULATIONS

27

Pacific whales. Sci. Rept. Whales Res. Inst., 15: 85-142.
FUJINO, K. (1962). Blood types of some species of the Antarctic whales. American Naturalist. 96 (889):
205-210.
FUJINO, K. (1963a). Intra-uterine selection due to maternal-feta! incompatibility of blood types in thewhales. Sci. Rept. Whales Res. Inst., 17 : 53-65.
FUJINO, K. (1963b). Population genetics of whales with reference to blood types. Bul. Jap. Soc. Sci.
Fisheries, 29(12): 1133-38.
LAWS, R.M. (1961). Reproduction, growth and age of Southern Fin Whales. Discovery Rept., 31: 327-486.
Office of the International Whaling Commission (1963). International Whaling Commission, Fifteenth
Annual Meeting. Norsk Hvalfangst-Tid., 52(8): 225-26.

PRENATAL DEVELOPMENT OF EAR PLUG
IN BALEEN WHALESTADAYOSHI ICHIHARA
The ear plug is a fairly soft tissue existing in the external auditory meatus of the
Mysticeti. It is composed of independent two tissues derived from the epidermisof external· auditory meatus and from that of so-called glove-finger. The glovefinger projects outwards from the tympanic bulla into the external auditory meatus.
Since Purves (1955) found out ring-like laminae in the longitudinally bisected plugcore derived from the epidermis of the glove-finger, the plug-core has encharmed
many cetacean biologists interested in determining the age of whales. Counting
the ring-like laminae to evaluate age of baleen whales is no more than understanding life histories of these whales through their ear plugs.
As series of studies on ear plugs, I have much interested in the formation of ear
plugs in the prenatal stage, because animal tissues begin to develop from the prenatal
period and the epidermis of the glove-finger also belongs to the same growth category.
It was also necessary to confirm my previous finding (Ichihara, 1959) through themany materials from the baleen whale foetuses. In this paper, I examine the morphology and histology for the prenatal development of the glove-finger along withthe ear plug. The keratinized and fatty degeneration of epidermal cells of the
glove-finger are alternately accumulated to form the plug-core in the postnatal stageof the baleen whale. The present study not only supports this fundamental mechanism found by me, but also gives some suggestions to interpret the factors affecting the formation of the plug-core.
I am much indebted to Dr. Hideo Omura, the Director of our Institute for hiskind support throughout this work. My sincere thanks are dut to Messrs. Toshitomo Shida and Yasuji Fukuda, the Department of Anatomy, Faculty of Medicine,
University of Tokyo, for their kind helps in the histological examination and photomicrographic technique. I also indebted to Dr. Kazuo Fujino, a staff of our Institute, who collected several heads from fin whale foetuses in the Antarctic expedition and brought them to my study.
MATERIAL AND METHOD

Most of materials in this paper were collected by myself on board Nisshin-maru,
a factoryship of Taiyo Gyogyo Company in the Antarctic expedition in the 1959/60
season. Foetuses were taken from the uteri of £lensed mother whales. After measuring the lengths of foetuses, their heads were cut off and pieces available for this study,
that is, posterior portions of heads including the external auditory meatus, glovefinger and tympanic bulla were obtained. These specimens were preserved in the
10% formalin solution soon after this treatment. The large blocks from full-grownfoetuses are preserved in diluted formalin solution under 10% as the first step and29

30

T. ICHIHARA

removed gradually into concentrated solution for the examination at our Institute.
In the same way Dr. Fujino kindly presented me several heads from fin whale foetuses in the Kyokuyo-maru No. 2 expedition in the 1960/61 Antarctic season. These
specimens are used to check my interpretation. The examined specimens which I
collected comprise 48 Antarctic fin whale (Balaenoptera physalus), 17 sei whale (Balaenoptera borealis) and 2 humpback whale (Megaptera novaeangliae) foetuses as presented
in the appendix.
Law's finding (1959) for the foetal growth curve is applied to determining
accurate foetal months from the lengths of examined foetuses. According to Laws
the average duration of gestation is 11 1/4 months for the Antarctic fin whale andabout 12 months for the North Pacific sei whale.
I counted numbers of ovulation in mother's ovaries at the spot aboard the factory
ship to evaluate the relative age of the mother whale. The examined foetuses are
obtained from mother whales of various ages and there is no bias in the sampling,in which I intended to obtain the foetuses of various length. The specimens from
foetuses under 71 cm, corresponding to the 3 3/4 foetal months, also were obtained
but failed to be examined in the sectioning course. These blocks from heads
were dissected for the morphological study. Later glove-fingers and ear plugs wereembedded in the celloidin solution, and sectioned in the thickness from 10 to 15 µ.
The staining method by haematoxylin eosin was applied.
The post-mortem times range from 1 hour and 25 minutes to 13 hours and 35
minutes for the foetuses of fin whales, from 45 minutes to 9 hours and 40 minutes
for the sei whale foetuses, and from 3 hours and 45 minutes to 7 hours and 5 minutes
for the humpback whale foetuses, as listed in the appendix. In addition to thespecimens from such foetuses, I examined the prenatal layers of ear plugs fromadult baleen whales, which also includes the blue (Balaenoptera musculus), theBryde's (Balanoptera edeni) and the minke whale (Balaenoptera acutorostrata).
MORPHOLOGY OF GLOVE-FINGER AND EAR PLUG
In the course of dissecting the external auditory meatus of foetuses from the earhole to the tympanic bulla through the blubber, I observed the colour on the surfaceof auditory meatus and glove-finger and then measured the length of space fromthe blind section beneath the blubber to the distal end of the glove-finger. Taking
the glove-finger out of the auditory meatus, I measured the length of glove-finger,from its distal end to the proximal end of tympanic ligament, and its breadth.
From the colour on the surface of glove-finger and from that on the internal
wall of external auditory meatus, four stages are present in the foetal stage of thebaleen whale as indicated in Table 1. In fin whales, stage I indicates the development until the 3rd and 4th foetal months, stage II the 5th and 6th foetal months,
stage III from the 7th to 9th months and stage IV after the IOth foetal months.
In sei whles, stage II represents the 5th to 7th foetal months. Glove-fingers of
foetuses in stage I are transparent and rather whiter. From stage II to III theircolours change from pinkish-white to dark-brown. In stage IV, glove-fingers of

PRENATAL EAR PLUG

31

fin whales are brown, while those of sei whales do gradually black. Ear plugs fromadult sei whales is more black than that from [fin whales. The content of melanin
during the keratinized degeneration of epidermal cells probably is more abundant
for the sei whale than for the fin whale. The colours of stage IV are maintained
from juvenile to adult both for fin whales and for sei whales. The observation for
foetuses of the humpback whale is insufficient for describing the colour change during foetal development but glove-fingers are pinkish-white in stage II.
TABLE 1.

FIN WHALE
Pregnancy
Stage
month

COLOUR OF GLOVE-FINGER, EXTERNAL AUDITORY MEATUS
AND BLIND SECTION FOR EACH FOETAL MONTH
OF THREE SPECIES IN THE BALEEN WHALE

External auditory meatus

Glove-finger

I {!

White (transparency)~

Pinkish-white

II {

~

Light-brown
Dark-brown

Light-brown, Black antero-dorsal portion
Dark-brown"
Dark-brown

Dark-brown

III {

IV

10

"

White
Pinkish-white"

Blind section

Yellw
Yellowish-white"

SEI WHALE
Stage

Pregnancy
month
5

II {
III {

IV

Glove-finger
Pinkish-whiteLight-brown
Dark-brown
Black"
Light-brown
Dark-brown
Black

6
7
8

9
10

External auditory meatus
Pinkish-white"

Blind section

Black antero-dorsal portionHUMPBACK WHALE
Stage
II

Pregnancy
month

Glove-finger

6

Pinkish-white

External auditory meatus
Pinkish-white,

Blind section

Black antero-dorsal portion

The colour on the internal wall of external auditory meatus is very similar tothat on the surface of the glove-finger but it becomes black at stage III particularlyin the antero-dorsal portion. The black portion tends to extend gradually to otherpart of the external auditory meatus. The black part occurs in stage II for sei andhumpback whale foetuses.
In the early foetal month, the colour on the suface of glove-finger depends on
the thickness of connective tissue and the abundance of blood capillaries or bloodvessels. However the brown colour over stage III indicates the occurrence ofadhesive materials on the surface of the glove-finger and of the internal wall of theexternal auditory meatus. In fact, the original colour of the glove-finger and theexternal auditory meatus appears again after scraping these materials off. From

T. ICHIHARA

32
12
10

A. length of tympanic

8
6
4
2

E

u

10

B. Length of glove-finger

8
6
4
2

E
u

3

..

C. Breadth of glove-finger

2

E
u

50 -

-C40D.
~·~ 30 Space of auditory-meatus
~ 20
l 0

Distal end of glove-finger •to blind section
!

'

I

2

•
•

3

'

4

5

~

6

•
•

7

8

'1•:1~9l0

11Pregnancy Month

Fig. I. Growth of tympanic bulla, glove-finger and external auditory meatus in the fin
whale foetus from the Antarctic.
12
lO

A Length of tympanic bull a

8
E 6

4

u

2
l0

..

B. Length of glove-finger

8
E 6

4

u

2L-~~~========::::::'.==--~~~~~~~~~__J...

3 ·C. Breadth of glove-finger
E 2
u

l

50

c 40
~ 30
~20

D. Space of auditory-meatus
Distal end of glove-finger
to blind section

. ..

10

.

2

3

4

5

6

7

8

9

l0

...
11

Pregnancy Month

Fig. 2. Growth of tympanic bulla, glove-finger and external auditory meatus in the sei
whale foetus from the Antarctic.

12

PRENATAL EAR PLUG

33

the naked-eye observation, the horny layer of foetal epidermis seems to be accumulated
from 7th foetal month for fin whales and from about the 8th foetal month for sei
whales. In fin foetuses, the yellow adhesive materials are observed on the blind
section of the auditory meatus over the 8th foetal month. These materials develop
into ear plugs and observed by the naked-eye as various shapes in the latter half of
the 9th foetal months.
To examine the transformation of the glove-finger, its length and greatest
breadth were measured. The measurement of the distance from the distal endof the glove-finger to the blind section of the external auditory meatus wasneeded for examining the mechanism which the prenatal ear plug is preserved
throughout the life span of whale. Fig. I indicates the relation between the development of the glove-finger and that of the external auditory meatus. The shapeof glove-finger changes from the early to the late foetal stage. The length of glovefinger from its distal end to the end of tympanic ligament increases rapidly after 4th
or 5th foetal months for the fin and sei whale. Until the middle foetal stage, thegreatest breadth is indefinitely measured but estimated to grow in the same way as
the increment oflength. As shown in Fig. 1, the length of tympanic bulla, which
is a bony tissue closely connected with the glove-finger, also increases in a sigmoid
curve in the foetal stage. The size of the tympanic bulla seems to increase slightly
in the postnatal stage, while the growth of the glove-finger is completed in the latefoetal stage. Although the size of the sei whale golve-finger is different from that of
the fin whale, the growth pattern is about the same between two species (Fig. 2).
This observation may be applied to the other baleen whales.
The relation between the glove-finger and the external auditory meatus is of
most importance to pursue the prenatal development of the ear plug. In fin whale
foetuses the space between the blind section of the external auditory meatus and theglove-finger is large in the early stage. At each foetal month, the relative value ofthe space changes as indicated in the lowest in Figs. 1 & 2. The space in thesefigures represents the length from the distal end of the glove-finger to the blind section of the external auditory meatus. If the relative value of the space is expressed
as a percentage of the length of the auditory meatus from the proximal end to theblind section, it distributes along the concave curve with the developing foetal month.
The external auditory meatus is closely connected with the glove-finger at its proximal
end. In fin whales the relative space exceeds 40 percent under the 4th foetal monthand approaches to zero percent from the 8th to 9th foetal months, when some foetuseshave no space between the blind section and the glove-finber. In the late foetal
month, it increases again and is supposed to extend rapidly at the postnatal stage.
In fact the external auditory meatus of the adult whale is elongated along thesquamosal region of the large skull. This change of space also is drawn in Fig. 3.
On the other hand the sei whale foetus has a fairly larger space in the 8th,
9th and lOth foetal months, compared with the fin whale foetus. The space is 10
percent in these foetal stages, as shown in the lowest of Fig. 2 and there is only one
foetus having no space. The change of space in Fig. 1 & 2 represents an evidence
that the development of the external auditory meatus is not proportionate to that

T. ICHIHARA

34

of the glove-finger in the foetal stage. In two humpback whale foetuses, relativevalues of spaces are 29.6 and 44.4 percent but these foetuses are in the 6th foetal
months. This evidence probably is expanded for the other species of the balaenopterid whale than fin, sei and humpback whales.
BS

i

BS

BS

GF

2

3

Fig. 3. Relation between the gave-finger and the external auditory meatus in the developing foetus of the fin whale.
1. The 4th foetal month
BS :Blind section
EAM: External auditory meatus
2. The 7th foetal month
3. The lOth foetal month GF:
Glove-finger

In fin whale foetuses the external auditory meatus becomes to cover the outerside of the glove-finger after the keratinized epidermal cells was accumulated. Therefore, the prenatal plug-core of the fin whale is surrounded by the keratinized layer
derived from the epithelium of the external auditory meatus. The mechanism thatthe prenatal ear plug is preserved for the all life of fin whales is interpreted from thisfinding. In most of sei whale foetuses, the external auditory meatus does notsurround the surface of the glove-finger throughout the foetal stage. The prenatal
ear plug, therefore, is unstably accumulated. In fact, it is very difficult to findthe prenatal layer in the ear plug from the adult sei whale. At the distal end of
the plug-core, it is easily separated from the outer covering. The practical collectionof whole ear plugs to evaluate the age is difficult for the sei whale.

35

PRENATAL EAR PLUG

From the presence of the prenatal ear plug and space of the external auditory
meatus, baleen whales are divided into two categories. The one includes the ear
plugs from blue, fin, Bryde's and humpback whales. In the most of these whales,prenatal ear plugs are preserved completely throughout the life span. The othercontains the ear plugs from sei and minke whales, in which prenatal layers are indistinguishable. In the former category, the shape of prenatal ear plug depends upon
the shape of space between the glove-finger and the internal wall of the external
auditory meatus near the full foetal month. I draw the shape of the prenatal ear
plug of the fin whale in Fig. 4. The ear plugs accumulated at the distal end of the
glove-finger develops according to the shape of the increasing space after the 8th
foetal months.
BS
BS

BS

GF

GF

GF

Fig. 4. Shapes of ear plug in the late foetal stage of the fin whale. It correlates with theshape of space from the distal end of glove-finger to the blind section of external auditory
meatus.
BS : Blind section of external auditory meatus.
EP: Ear plug.
GF: Glover-finger.

There are various kinds of shapes in the prenatal ear plugs. The most dominant shape is crescent and the triangular shape sometimes present. Such a finding
is applied to blue, Bryde's and humpback whale foetuses. In the ear plugs fromadult blue, Bryde's and humpback whales there remain various shapes of prenatal
layers.
HISTOLOGY

The study on the formation of prenatal ear plug should be approached by the histological examination. When age of baleen whales are estimated by ear plugs,
the core part is more important than the outer-covering (Purves, 1955), although thecore and outer-covering constitute socalled ear plugs of baleen whales. The histological examination in this paper, therefore, was forcused on the plug-core derived
from the degenerated epidermal cells of the glove-finger. Ichihara (1959) points
out that the celloidin section suits for the hard materials like the glove-finger andthe frozen section for the soft materials like the ear plug. In the foetal stage, how-36

T. ICHIHARA

3200
Antarctic Fin Whale

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Pregnancy

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Fig. 5. The increasing thickness of the connective tissue of the glove-finger from the fin
whale foetus. The broken line is estimated.

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Fig. 6. The increasing thickness of the connective tissue of the glove-finger from the sei
whale foetus. The broken line is estimated.

PRENATAL EAR PLUG

37

ever, very thin ear plugs are accumulated on the surface of the glove-finger, andhence I used only the celloidin section for this study. On the basis of the sectionof thickness from 10 to 15 µ, I measured the thickness of the connective tissue ofthe glove-finger, that of the keratinized layer and fatty degenerated layer of the
glove-finger epidermis for each specimen. My observations also are made forthe degeneration of nucleus of the germinal layers and for the occurrence of thekeratinized layer densely stained by eosin.
Thickness of connective tissue: The thickness of the connective tissue was measured
between the basal layer of the outer epidermis and that of the inner one of the glovefinger. As papillary layers undulate slightly after the 6th foetal months, the meanvalue is obtained from several measurements for each specimen. The thickness ofthe connective tissue is plotted against each foetal month of the fin whale as shownin Fig. 5. The broken line is estimated in the figure, because available data are
insufficient. There is a suitable straight line for the increasing thickness until about
the 6th foetal month and then the thickness grows rapidly until the full foetal month.
Just after birth, the thickness of the connective tissue approaches to about 2900µ,
the mean value for the adult fin whale.
The thickness of the connective tissue represents the same increment for the sei
whale foetus but it is thinner than for the fin whale foetus as, indicated in Fig. 6.
Keratinization: A specimen from the 3 3/4 to 4th foetal months is covered with
two layered epidermis. The outer layer, the periderm, constitutes a protective
covering although the nucleus is in a depressed form (see Plate I, Fig. 1). The basal
layer of early embryo is composed of low cuboidal cells with clearly stainable nuclei
and a smooth basal surface. With the increasing embryo, the basal cells become
columnar with large, darkly stained nuclei and proliferative. Even in a specimen
from the 3 3/4 to 4th months, the compact basal layer is covered by periderm cells,
some of which are exfoliating.
In the human embryo, a stratum intermedium, proliferated from the basal layer
develops between the basal layer and periderm at about the 4th foetal months andtoward the end of foetal life it, now called stratum spinosum, or prickle cell layer,
is several cells thick (Montagna, 1962). These processes also exist in the epitheliumof baleen whale foetuses.
The periderm of the foetal glove-finger is stained lightly by eosin. Montagna(1962) states that the keratohyalin granules appear where the epidermis is thickest
but the general epidermis has no stratum granulosum at the end of the 5th months
in the human embryo and that the keratinization progresses only when the stratum
granulosum is formed. The stratum granulosum is not observed definitely in the
thick epidermis of the glove-finger from the baleen whale, although it is assumed
that the same mechanism as in the man progresses in the keratinization of thewhale epidermis.
To examine when the keratinization begins, I measured the thickness from theupper edge of the basal layer to the most distal end of accumulated substance foreach specimen from fin whale foetuses and plotted it against each foetal month in
Fig. 7. The thickness expressed in such a way certainly includes both the kera-

38

T. ICHIHARA

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Fig. 7. The increasing thickness of the accumulated layer of the fin whale foetus, including the keratinization and the fatty degeneration layer in the epidermis of the glovefinger. Broken line is estimated and chain line indicates the mean curve.

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Fig. 8. The increasing thickness of darkly stained part by eosin with the advancement of
the foetal month of the fin whale. This part is present at the lowest of keratinizedlayer.

PRENATAL EAR PLUG

39

tinized layer and the fatty layer described later. Therefore, the thickness of keratinized layer will be obtained by subtracting the fatty layer from total accumulated
layer. It is difficult to examine accurately the primitively keratinized cell from the
prickle cell layer in the late foetal stage.
Fig. 7 indicates the accumulation speed in the fin whale foetus. From fertilization to the 6 l /2 foetal months, the accumulation progresses in a constant ratio,
although it is estimated by the broken line in the early foetal stage from fertilization
through the 3rd foetal month. After the 6 l /2 foetal months, the accumulated layer
is rapidly thick but there are great variations for individual specimens. An accumulated layer from one specimen of the 8 1/4-8 2/4 foetal months is 119 µthick,while that from another specimen of the same foetal month is 28 µ thick. As theexternal auditory meatus covers the surface of the glove-finger after the 8th foetal
months, it is difficult to examine the whole accumulated layer only from sections ofglove-fingers. The prenatal ear plug, disconnected from the surface of glove-finger,
indicates various heights. The values of the keratinized layers are about 4300 11
for a specimen from the 9 2/4-3/4 foetal months, about 850 µfor that from the 1010 1/4 foetal months and about 3800 µfor that from the 10 3/4-11 foetal months.
These variations probably depends on the activity of the mitotic division on
the prickle-cell layer or the basal layer of the epidermis. There are also great
variations for the lengths of plug-cores from adult fin whales (Nishiwaki, Ichihara & Ohsumi, 1958: Purves & Mountford, 1959).
The germinal layer also becomes thick rapidly after the 6th foetal months andis maintained for the late foetal month. Probably the thickness of the germinal
layer and hence the number in stratified cells, also will be kept in the postnatal life.
At the same, the layer stained darkly by eosin begins to occur in the distal endof the accumulated layer as indicated in Plate II, Fig. 1 & III, Fig. I. This darkly
stained layer is thick with the growing foetuses and reaches about 40 µ in thickness
at birth. The increment of this layer for examined specimens is plotted against eachfoetal month of the fin whale in Fig. 8. Although the periderm in the early foetal stage
appears to undergo cornification, it probably does not mean the keratinization.
The occurrence of darkly stained layer seems to indicate the keratinization in theepidermis of the glove-finger.
In the sei whale foetus as well as in the fin whale foetus, the darkly stained
layer occurs when the accumulation ratio increases rapidly. Fig. 9 shows the increasing thickness of total accumulated layer against each foetal month of the sei
whale, although available specimens are insufficient. The keratinization in the epidermis of the glove-finger arises at the 8 l /2 foetal months of the Antarctic sei whale.
For the sei whale foetus, there is a divergence between the growth curve by
obtained by Matthews (1938) and that indicated by Laws (1959). Interpretationby Matthews results from the Antarctic sei whale, while Laws has his conclusion on
the basis of the North Pacific sei whale, therefore, the divergence may be derived
from the localities of sei whales. In determining the foetal month of the sei whale,
I adopted Laws' finding, because his curve fits the growth patterns of otherbalaenopterid whales. I am afraid, however, the keratinization for the Antarctic

T. ICHIHARA

40

sei whale foetus occurs slightly earlier than the 8th foetal month. There are also
great variations in the thickness of the keratinized layer for the individual foetusof the sei whale. In the 10 1/2 foetal months, an accumulated layer from a
specimen is 273 µ thick, while that from another specimen is 35 µ thick.
The keratinized layer in the foetal stage remains in the ear plug of the adultbaleen whale. Plate V indicates the presence of the prenatal keratinized layer,
appearing at the most distal end of the plug-core, outside of the prenatal fatty layer
for various baleen whales. The prenatal keratinized layer is observed more clearlyin the fin, blue, Bryde's and humpback whale than in the sei and minke whale.

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Pregnancy Month

Fig. 9. The increasing thickness of the accumulated layer of the sei whale foetus, including
the keratinizatin and the fatty degeneration layer in the epidermis of the glove-finger.
Broken line is estimated and chain line indicates the mean curve.

Fatty degeneration: The germinal layer becomes thick with the advancementof the foetal month and composed of cells in several layer at the 6 1/2 foetal months.
The outside prickle-cell layer continue to degenerate into the keratinized cells
from the 6 l /2 to the 8th foetal months, when slightly swelled cells in the pricklecell layer sometimes contain lipoid granules in their cystopasms. This indicatesthe occurrence of fatty degenerated cells in the epithelium of the glove-finger. The
fatty degeneration progresses rapidly in the whole prickle-cell layer in larger foetuses
after the 8th foetal months. The cystoplasms filled with lipoid granules develop
into the fatty layer which is removed outwards by the pressure of newly degenerated
fatty cells. The accumulation processes of fatty layers are clearly indicated in Plate
III, Fig. 1 & 2 and IV, Fig. 1 & 2. From the lOth to 11 th foetal months of the
fin whale, the fatty layer is from 33 µ to 130 µ thick and estimated rapidly thickat birth.
As the fatty layer remains on the surface of glove-finger, its thickness can bemeasured accurately through the section. Fig. 10 indicates the increment of fatty
layer against each foetal month of fin whales. The thickness of the fatty layer ismeasured between the lower border of the keratinized layer and the basal layerof the glove-finger epidermis. According to this figure, the fatty degenerated cells•

PRENATAL EAR PLUG

41

appears at the 8th foetal months and the fatty layer develops over 180 µ in thicknessfor 3 l /4 month until the birth of the fin whale foetus. Through the microscopic
examination, my previous finding (1959) can be applied to the process of fatty
degeneration in the prenal ear plug. This suggests that the fatty degeneration passes
through the same mechanism in the prenatal as well as in the postnatal ear plugs.
In specimens from sei whale foetuses, fatty granules are found for the first timein the cystoplasm of degenerated cells in the 10 1/4 foetal months. Although a fe\vspecimens do not represent the rigid finding, it is assumed that sei whale foetuses
develop more thin fatty layer than do fin whale foetuses.

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By the naked eye observation, these fatty layers remain at the distal end of all
ear plugs from fin, blue, Bryde's and humpback whales, therefore, it can be recordedby the photometric method (lchihara, 1962). Prenatal fatty layers of ear plugs
from various kind of baleen whales are indicated Plate V; Figs. I, 2, 3, 4 & 5.
The longitudinal fatty layer is absent in the keratinized layer of the prenatal
ear plugs. In the bisected specimen of the ear plug from the adult baleen whale,
the longitudinal fatty layer is clearly present at the concavity in the epidermis corresponding to the undulate papillae in the derma of the glove-finger. In the postnatal ear plug, furthermore, the longitudinal fatty layer becomes more clear near
the proximal end with the advancement of the whale age. This is primarily because
the papillae of derma project outwards with the increasing age of the whale, although
there are individual variations in its degree. The absence of the longitudinal fatty
layer in the prenatal stage is based on not only the comparatively flat surface ofpapillae but also the unique process in which the keratinized fusiform cell is nearly

42

T. ICHIHARA

the same size as the fatty degenerated cell. This feature is shown in Plate IV, Fig.
2. The transformation of degenerated cell in the ear plug from the adult whale
was already described (see Fig. 9, Ichihara, 1959). The physical force during thedevelopment of ear plug effects intensively on the formation of the longitudinal
fatty layer. This will be examined in connexion with the renewal time of epidermal cells in the future study.
DISCUSSION

Laws & Purves (1956), examing ear plugs from young fin whale captured at
the norweigian coast, confirm their earlier conclusions about initial stages in theformation of the plug. They continue their statements that the first lamination
which is always a small, conical, unstratified body rich in calcium, is deemed
to be that part of the plug which is present in the ear before birth. It is vague
what they mean by the first lamination, but the unstratified body probably
indicates only the fatty layer described in the previous chapter of this paper. There
are, however, two layers in the ear before birth, composed of dark and brightlayers.
Chittleborough (1959) reports that only the secretary membranes were foundwhen the ear plugs from near-term humpback whale foetuses were dissected out,
and he considers that the first lamination of the ear plug is laid down soon after birth.
Although he disagrees with the presence of prenatal ear plug in the humpback whale,
I suppose that his finding depends on examing the surface of the glove-finger onwhich the collapse of prenatal keratinized and fatty layer has already progressed.
Vith the increasing time from kill to Bensing, the new ear plug rich in keratin undergoes decomposition and hence it is disconnected from the surface of the glove-finger,even in adult baleen whales. I confirmed the presence of the prenatal ear plug fora near-term humpback whale foetus taken off Ryukyu Islands, as reported in myprevious paper (lchihara, 1959). Besides in this paper I reconfirm the occurrenceof degenerated epidermal cells in glove-fingers from two Antarctic humpback whale
foetuses. Crisp (1963) discusses the effect of adult whale length and post-mortem
time on ease ofremoving ear plugs from fin whales and concludes that there is a significant difference in the success of extraction between the whales with post-mortem timesof less than 7 hours and those that had post-mortem times of more than 7 hours.
There is a positive relationship between the ease of removing ear plugs and the decomposition of their tissues, however, the technical ease is different from the accurate examination on the ear plug. Histological examinations need the freshmaterials.
The development of baleen plate should be noticed here. The periodic growthof the cortical layer sheathing the medullary layer in the baleen plate has been an
indicator of age of baleen whales since Ruud (1940) pointed its significance. The
cortical layer is formed by the cornification of cells from the lateral surfaces of theblade-pulp, while the medullary tissue is formed from the lower and inner margin(Eschricht & Reinhardt, 1866; Tullberg,1883). Citing Tullberg's paper, Mackin'1

PRENATAL EAR PLUG

43

tosh and Wheeler (1929) states that the first rudiments of the two blocks of baleen
plate are found after the blue whale foetus reaches a length of 2 metres or more
and then two plain strips of a soft whitish material appear, one on each side of theupper jaw. They state, furthermore, that at the 2.5 to 3 metres, minute transverse
ridges appear on these strips and later develop into whalebone plates. With regard
to fin whales, Mackintosh & Wheeler describe that the development of the baleenin the blue whale foetus applies equally to its develpoment in the fin whale foetus.
Ohsumi (1960) reports that the first rudiments of the baleen plates are found at thelength of 1.75 metres in the Antarctic fin whale foetus.
According to the foetal growth curve of baleen whales, indicated by Laws
(1959), the length of 2 metres in the blue whale and that of 1.75 metres in the fin
whale correspond to the 7th foetal months. The occurrence of rudiments of baleen
plates does not yet indicate the keratinization of cells from lateral surfaces of theblade-pulp.
The evidence that the keratinized cells in the epidermis of the glove-finger
appears at the 6 l /2 foetal month of the fin whale supports the finding that steps inthe prenatal development of keratinized cells depend on various tissues of the whale
body. The keratinization might be more precocious in the epidermal cells of the
glove-finger than those of the other tissues, however, it is necessary to reexamine thesignificance underlying in the comparison between the periodic mark on the baleen
plate and the laminae number in the ear plug, because these two age indicators forbaleen whale is formed primarily from the keratinization of cells.
In the prenatal stage of fin whale, the fatty degenerated cells appears from the
8th foetal months and develops until birth. The prenatal fatty layer in the otherbaleen whale enables us to discriminate it from the postnatal accumulation of the ear
plug. A sudden turn of the epidermal cells from the keratinized to the fatty degeneration can not occur without the internal stimulation of the body. In the foetal
stage, it is the most reasonable to accept the endocrinal stimulus through the blood
supply from the maternal body. Although enzymes act as catalysts in the regulationof metabolic processes, hormones in vivo exert their influence by acting indirectly
upon the enzymes which catalyze the particular reaction (Rothman, 1954).
The season when the fatty degeneration arises in the maternal ear plugs will be
examined in relation to the physiologicals rhythm in the future study, throughwhich the relation between the biological clock and the calendar period vlill beclarified.
The neonatal line of the ear plug is defined as the part where the formation of
the prenatal fatty layer ends.
SUMMARY

In the course of my continuous study on the accumulation of the ear plug, the mostreliable material to determine the age of baleen whales, I examined the prenatal
development of ear plug by using foetal specimens from 48 fin whales, 17 sei whalesand 2 humpback whales in the Antarctic. The foetal growth curve by Laws (1959)

44

T. ICHIHARA

is applied in this paper to obtain the accurate foetal month for the examined specimens. Through the naked eye observation during dissecting the external auditory
meatus from the blind section to the glove-finger and through the histological examination on the celloidin section of the glove-finger, my findings are summarized
as follows.
I. The shape of prenatal ear plug is determined by the difference in growth
between the external auditory meatus and the glove-finger in the foetal stage ofbaleen whale. With regard to shapes, there are individual variations in the same
species as well as the specific differences among baleen whales.
2. The prenatal ear plug is essentially maintained throughout the life span of
the baleen whale. It is observed clearly in the ear plugs from the adult blue, fin,
Bryde's and humpback whales but rarely in the ear plugs from adult sei and minke
whales. In the sei and minke whale, the connection between the ear plug-core andthe outer-covering is so weak that the ear plug is separated at the distal portionof the core in the course of removing ear plugs from the whale bodies. This implies
some difficulties in age determination by ear plug for these two species.
3. The keratinization in the epidermal cells of the glove-finger appears at the
6 1/2 foetal month of the fin whale, according to the histological examination. It
arises at the 8 I /2 foetal month of the sei whale. The observation by the naked eyefor foetuses endorses this finding. The keratinized layer in the prenatal stage,
showing great individual variation of thickness, remains as the first dark layer atthe distal end of the plug-core.
4. The fatty degeneration in the epidermal cells of the glove-finger occul's at
the 8th foetal months and continues to progress until birth in the fin whale. It also
appears at the late foetal month of the sei whale. In the adult ear plugs frombaleen whales, the fatty layer remains as the first bright layer following the above
keratinized layer.
5. The neonatal line of the ear plug is defined as the part where the firstbright layer ceases to grow.
6. The longitudinal bright layer is not yet present in the foetal ear plug.
7. The substances stimulating the foetal epidermis of the glove-finger to thefatty degeneration seem to be supplied through the maternal blood. The endocrine
factors may act an important part.
REFERENCES
Chittleborough, R. G. ( 1959). Determination of age in the humpback whale, Megaptera nodosa (Bonnaterre).
Aust. J. Mar. Freshw. Res., 10: 125-143.
Crisp, D. T. (1963). The effect of whale length and post-mortem time on ease of removing ear plugs fromfin whales. Norsk Hvalfangst-Tid., 5: 121-123.
Eschricht, D. F.,&]. Reinhardt (1866). On the greenland right whale. Recent memoirs on the Cetacea.
Roy. Soc. of London.
Ichihara, T. ( 1959). Formation mechanism of ear plug in baleen whales in relation to glove-finger. Sci. Rept.
lJ7hales Res. Inst., 14: 107-135.
- - (1963). Photometric method for counting laminae in ear pug of baleen whale. Sci. Rept. Whales
Res. Inst., 17: 37-48.

PRENATAL EAR PLUG

45

Laws, R. M. & P.E. Purves (1956) The ear plug of the Mysticeti as an indication of age with special reference to the North Atlantic fin whale (Balaenoptera physalus Linn.) Norsk Hvalfangst-Tid., 8: 413-35.
Laws, R. M. (1959). The foetal growth rates of whales with special reference to the fin whale, Balaenoptera
physalus Linn. Discovery Repts., 29: 281-308.
Mackintosh, N. A. &J. F. G. Wheeler (1929). Southern blue and fin whales. Discovery Repts., 1: 257-540.
Matthews, L. H. (1938). The sei whale, Balaenoptera borealis. Discovery Repts., 17: 183-290.
Montagna vV. (1962). The structure and function ef skin. Academk press, New York.: 1-454.
Nishiwaki, M., T. Ichihara & S. Ohsumi (1959). Age studies of fin whale based on ear plug. Sci. Rept.
Whales Res. Inst., 13: 155-169.
Ohsumi, S. (1960). Relative growth of the fin whale, Balaenoptera physalus (Linn.) Sci. Rept. Whales Res.
Inst., 15: 17-84.
Purves, P. E. (1955). The wax plug in the external auditory meatus of the Mysticeti. Discovery Repts., 27:
293-302.
Purves, P. E., & M. D. Mountford (1959). Ear plug laminations in relaion to the age composition of a
population of fin whales (Balaenoptera physalus). Bull. Brit. Mus., (Nat. His). Zool., 5: 125-61.
Rothman, S. (1954). Physiology and biochemistry of the skin. The University of Chicago press. Chicago; 1741.
Ruun, J. T. (1940). The surface structure of the baleen plates as a possible clue to age in whales. Hvalradets
Skrifter., 23: 1-23.
TuLLBERG, T. (1883). Bau und Entwicklung der Barten bei Balaenoptera sibbaldii, Nova Acta Soc. Sci. Upsal.,ser. III, 11 : 1-36.

46

T. ICHIHARAAPPENDIX.

THE BIOLOGICAL DATA FOR EXAMINED FOETUSESFIN WHALE

Dateobtained

No.

Foetallengthin cm

Foetalmonth

Sex infoetusElapsedtime
No. of ovulaaftertion in mothkilling er's ovaries Position captured

1
2
3
4
5

9, Jan.
4, Jan.
6, Jan.
26, Jan.
7, Jan.

1960
1960
1960
1960
1960

6.6
19.0
47.5
52
71

3/4-1
1-3/4
2 3/4-33
3 3/4-4

F
F
F
M
M

9-20
12-40
11-10
7-10
5-15

11
25
25
7
13

56°-I9 1S, 94°-561 E
57°-0718, 100°-231E
56°-3415, 95°-09 1E
60°-55 1S, 153°-01 1 E
56°-26'5, 92°-57 1 E

6
7
8
9
10

29, Dec.
29, Jan.
28, Dec.
8, Jan.
30, Dec.

1959
1960
1959
1960
1959

79
117
122
122
127

4 1/4
5 1/4
5 3/4-6
5 3/4-6
6

F
F
M
M
F

7-40
8-25
6-20
11-35
2-55

2
4
14
5
9

58°-3618, 92°-27 1 E
59°-31'5, 150°-!41 E
59°-12'S, 94°-241 E
57°-0018, 93°-361E
57°-5415, 93°-45'£

11
12
13
14
15

2, Feb.
23, Jan.
24, Jan.
30, Jan.
9, Mar.

1960
1960
1960
1960
1960

130
140
145
145
145

6-6 1/4
6 1/4-6 2/4
6 2/4
6 2/4
6 2/4

M
F
F
F
M

7-50
6-50
8-15
12-15
5-00

I
22
13
11
7

59°-321S, 150°-47 1E
62°-2l'S, 146°-l21 E
61°-4315, l50°-l7 1E
59°- I 41S, I 48°-441E
60°-541S, 150°-571E

16
17
18
19
20

10, Jan.
12, Feb.
31, Jan.
2, Feb.
11, Jan.

1960
1960
1960
1960
1960

165
173
175
175
183

6 3/4-77
7-7 1/4
7-7 1/4
7 1/4

M
M
M
F
M

11-40
11-00
6-15
1-35
9-35

7
I
2
5
3

56°-l61S, 92°-l91 E
68°-241S, 168°-l2'W60°-4818, 148°-521 E
59°-321S, 150°-47 1E
57°-l91S, 9! 0 -291E

21
22
23
24
25

21, Jan.
22, Jan.
19, Jan.
28, Dec.
30, Jan.

1960
1960
1960
1959
1960

183
183
191
203
206

7 1/4
7 1/4
7 1/4-7 2/4
7 2/4
7 2/4-7 3/4

F
F
F
M
M

7-45
12-45
10-10
5-25
10-50

3
2
21
19
2

63°-l61S, 140°-231E
62°-l21S, 144°-061E
64°-0618, 126°-321 E
59°-121S, 94°-241E
59°-l41S, 148°-44 1E

26
27
28
29
30

29, Dec.
21, Jan.
30, Jan.
. 4, Jan.
4, Feb.

1959
1960
1960
1960
1960

219
242
252
259
264

7 3/4
8-8 1/4
8 1/4
8 1/4
8 1/4-8 2/4

M
F
F
F
F

5-50
7-05
10-30
4-15
4-55

14
19
2
13
9

58°-37'S, 92°-26'E
63°-I61S, 140°-231 E
59°-I41S, 148°-44'£57°-07 1S, 100°-231£
59°-48'5, 150°-241 £

31
32
33
34
35

25, Jan.
30, Dec.
23, Jan.
4, Feb.
12, Jan.

1960
1959
1960
1960
1960

269
280
280
292
300

8 2/4
8 2/4-8 3/4
8 2/4-8 3/4
8 3/4
8 3/4

M
M
F
M
F

10-05
3-25
5-55
6-05
7-30

2
12
12
13
27

60°-38'5, 153°-561£
57°-541S, 93°-451E
62°-2! 1S, 146°-l21 E
59°-48'S, 150°-241 E
57°-00 1S, 92°-57 1E

36
37
38
39
40

18, Jan.
28, Dec.
28, Jan.
29, Jan.
29, Jan.

1960
1959
1960
1960
1960

300
323
338
348
353

8 3/4
9
9 1/4
9 1/4
9 1/4-9 2/4

M
M
F
M
F

11-55
3-15
5-55
10-00
12-50

16
19
15
17
20

64°-191S, 122°-101£
59°-!21S, 94°-241 £60°-35'5, 150°-361E
59°-3l'S, 150°-l4'E
59°-31 1S, 150°-!4'E

41
42
43
44
45

1, Mar.
25, Jan.
4, Feb.
9, Mar.
9, Mar.

1960
1960
1960
1960
1960

353
374
384
424
437

9 1/4-9 2/4
9 2/4
9 2/4-9 3/4
10
10

M
F
F
M
F

10-20
5-00
5-55
13-35
8-55

9
10
13
4
7

65°-05 1S, 17! 0 -48'E
60°-38'S, 153°-561E
59°-481S, 150°-24'E
60°-541S, 150°-571 E
60°-54'S, 150°-571£

46
47
48

22, Mar. 1960
11, Mar. 1960
22, Mar. 1960

440
531
556

10-10 1/4
10 2/4-10 3/4
10 3/4-11

F
M
F

1-25
2-20
2-05

4
29
17

59°-3! 1S, 150°-40'E
59°-3 l'S, I 50°-35'E
59°-3 l'S, 150°-40'E

M: MaleF: FemalePRENATAL EAR PLUG

47

SEI WHALE

No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

FoetallengthDateobtained
25, Jan.
12, Feb.
7, Feb.
29, Jan.
5, Feb.
7, Feb.
13, Feb.
25, Jan.
27, Jan.
2, Feb.
8, Feb.
12, Feb.
27, Feb.
8, Feb.
22, Feb.
10, Feb.
30, Jan.

in cm

Foetalmonth

Sex infoetus

84
153
175
183
193
198
198
242
247
249
264
300
305
315
315
323
325

5-5 1/4
7 1/4-7 2/4
8 1/4-8 2/4
8 2/4
8 2/4
8 3/4
8 3/4
9 1/4-9 2/4
9 2/4
9 2/4
9 3/4
10 1/4-10 2/4
10 1/4-10 2/4
10 2/4
10 2/4
10 2/4-10 3/4
10 2/4-10 3/4

M
F
M
M
M
M
M
F
F
M
F
M
M
F
M
M
F

1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960
1960

Elapsedtime
No. of ovulaaftertion in mothkilling er's ovaries
Position captured
9-40
5-25
3-30
8-30
6-05
3-40
5-50
9-00
7-15
9-05
2-45
8-05
0-45
3-50
3-50
4-45
9-35

8
4
4
10
13
8
11
6
13
6
4
6
5
9
10
13
5

60°-38'S, 153°-56'E
68°-24'S, 168°-12'W
65°-lO'S, 165°-00'E
59°-3l'S, 150°-14'E
60°-29'S, 153°-46'E
65°-lO'S, 165°-00'E
69°-0l'S, 166°-ll'W
60°-38'S, 153°-56'E
60°-19'S, 148°-42'E
59°-321s, 150°-47'E
66°-53'S, 169°-22'E
68°-24'S, 168°-12'W
66°-43'S, 178°-54'W
66°-53'S, 169°-22'E
65°-32'S, 163°-041W
69°-31 1s, 179°-00'W
59°-141s, 148°-44'E

HUMPBACK WHALE

No.

2

Date
obtained

Foetallengthin cm

Foetalmonth

Sex infoetusElapsedtime No. of ovulaaftertion in mothkilling er's ovaries
Position captured

21, Jan.

1960

109

6 1/2

M

3-45

8

63°-16'S, 140°-23'E

21, Jan.

1960

125

6 3/4

M

7-05

8

. 63°-16'S, 140°-23'E

M: MaleF: Female

EXPLANATION OF PLATESPLATE I
Fig. 1. The cross section of the glove-finger from the 3 3/4-4th foetal months of the
fin whale ( x 400). The compact basal layer, covered by periderm cells, some ofwhich are exfoliating. The basal layer is composed of low cuboidal cells.
P:
Periderm
BL : Basal layer
CT : Connective tissue
Fig. 2. The cross section of the glove-finger from the 8 1/2-8 3/4 foetal months of the
fin whale ( x 100). The thick epidermis is much proliferated. The keratinizedlayer is disconnected from this specimen.
BL : Basal layer
CT : Connective tissue

48

T. ICHIHARA
PLATE II
Fig. 1. The cross section of the glove-finger from the 9 1/4-9 1/2 foetal months of
the fin whale ( x 100). The keratinized layer darkly stained by eosin, is clearlyfound at the most outer side of the epidermis. The most part of keratinized layer
is disconnected from this specimen.
KDS : Keratinization darkly stained by eosin
BL :Basal layer
The enlarged photomicrograph for the same specimen ( x 300).

The lipoid

granules are found in the cystoplasm of the upper prickle-cell layer.

There areFig. 2.

many transofrmed nuclei.
FC : Fatty degenerated cell
PLATE III
Fig. I. The cross section of the glove-finger from the lOth foetal months of the fin
whale ( X 100). The fatty degenerated layer is clearly observed. The most part ofkeratinized layer is disconnected from this specimen.
KDS : Keratinization darkly stained by eosin
BL :Basal layer
Fig. 2. The enlarged photomicrograph for the same specimen ( X 400). Swelledcells, undergoing the fatty degeneration, are found at the upper prickle-cell layer.
At the most outside of the fatty layer depressed nuclei remain yet. The keratinizedlayer darkly stained by eosin is found at the most distal end.
FC : Fatty degenerated cell.
FL: Fatty layer.
PLATE IV
Fig. 1. The epidermis from the 10 3/4-11 th foetal months of the fin whale ( X 100).
The lower parts of keratinized layer is on the thick fatty layer.
KL: Keratinized layer
FC : Fatty degenerated cellFig. 2. The enlarged photomicrograph for the same specimen indicates the fatty
degenerated cells at the prickle-cell layer ( X 400).
the same size as the fatty degenerated cell.
KC : Keratinized cell
FC : Fatty degenerated cell.

The keratinized cell is about

PLATE VThe prenatal layers remaining at the most distal ends of plug-cores from adultbaleen whales. Prenatal layers are composed to two layers: keratinized (KL) andfatty degenerated (FL) layers.
Fig. 1. Fin whale ear plug
2. Blue whale ear plug
3. Humpback whale ear plug
4. Sei whale ear plug
5. Bryde's whale ear plug
PKL : Keratinized layer of the prenatal stage
PFL : Fatty layer of the prenatal stage

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EXAMINATION ON AGE DETERMINATION
OF THE FIN WHALE
SEIJI OHSUMIINTRODUCTION

As the age characters of the fin whale (Balaenoptera physalus L.), the following havebeen reported hitherto. They are body length, stage of growth, number of ovulation, white scars (Mackintosh & Wheeler, 1929), baleen plate (Ruud, 1940),
christalline lens (Nishiwaki, 1950), and ear plug (Purves, 1955). Among them,laminations presented in core of the ear plug is considered as the best age character,because the lamination is considered to be formed periodically, is used for both
sexes, and is recognized for all life span. Furthermore, ear plug is relatively easy
to be collected and prepared to examine the number of laminations in the core.
Number of corpora albicantia accumulated in overies has some weak points as
an age character. There is individual variation in the accumulation rate of corpora,and number of corpora is applicable as an age character for only sexually mature
females. However, it is useful for age character next to ear-plug lamination, andthe data of corpora count have been collected for long seasons. Furthermore theannual accumultion of corpora is also useful for the study of reproductive physiologyof the whale.
Ridges presented on the baleen plates is considered to be the most excellent
age character of the baleen whales in younger age groups, but unfortunately, it is
not able to be used for older age groups.
Now, it is very important to determine age of whale from above age characters,
and many hypotheses have been published on the age determination.
Concerning the ear-plug laminations, Purves (1955) first considers that theperiod of arrested growth corresponds to the migratory periods when physiologicaldemands of active swimming coincide with complete absence of food, so that eachlamination represents a growth period of 6 months. Laws & Purves (1956)
estimate that the biannual formation of lamination is correct, compared the ear
plug with baleen plate for small samples of fin whales. Nishiwaki (1957), Chittleborough (1959), Dawbin (1959) and Laws (1961) did not denied the hypothesis.
The hypothesis of biannual formation oflamination now influences on the cetacean
biology and population dynamics. However, recently long term marked whales
have been recovered (Brown, 1962) and the investigation of ear plug of the recaptured fin whales give a question on the annual accumulation rate of ear-pluglamination (Ohsumi, 1962). Purves & Mountford (1959) state that it is very
doughtful whether environmental conditions have any direct influence of the timeof formation of the laminae of the ear plug in whales. Since there is strong evidence(not given by them) that lamina formation is in inherent moulting cycle, it is very
probable that it takes place whether the whale migrates or not, and Ichihara (1959)
49

50

S. OHSUMI

discribed by the histological examination of ear plug that the ·effects of hormone
and enzyme on the degenerations of epithelial cells of glove-finger were regarded
initially, besides, the effect of the environmental factors were preseumed indirectly.
There are also many hypotheses on the accumulation rate of corpora albicantia
in ovaries. Laws (1958, 1961) reviewed the previous works on the problem. On
the fin whale, Mackintosh & Wheeler (1929) plotted the frequencies of corpora,found peakes occurred at 4-5, 12 and 19 corpora, and suggested that these represented the increase in number of corpora at intervals of 2 years. ·wheeler (1930)
developed this hypothesis by more material, and concluded that about 5 ovulations occur each breeding cycle, or in average 2.5 per year. Peters (1939) reported
that he had been able to establish morphological and histological criteria for distinguishing the corpora albicantia representing pregnancy and ovulations, and be
estimated that there is an average of0.9 in a year by counting the pregnant corpora
albicantia and assuming a 2-years reproductive cycle. Mackintosh (1942) shmved
by a marked fin whale recaptured that the annual increment of corpora albicantia
had possibility to be less than one. Using the baleen plates as a new method forage determination, Ruud (1940, 1945) suggested that in the breeding season, up
to 6-7 ovulations are possible before pregnancy inpervenes. Nishiwaki (1952)
assumed that the annual increment of corpora albicantia after the first sexuallymature age should be 1.5, combining baleen plates, crystalline lens, number ofovulation and sexual and physical maturity.
Since ear plug was discovered as a new method of age determination by Purves(1955), many authors have reported the relation between ear-plug lamination andnumber of corpora in the ovaries. Nishiwaki (1957) drew a figure on this relation
for the Antarctic fin whales and got a result that in average corpora accumulation
was 1.2, if ear-plug laminations are formed biannually. Nishiwaki, Ichihara andOhsumi (1958) drew similar figure as above paper and got that there was individual
and racial variation in annual accumulation rate of corpora and in average theannual corpora accumulation rate was 0.9 in the Antarctic fin whale and about
0.8 in the North Pacific fin whales, if ear-plug lamination was formed biannually.
Laws studied the annual accumulation rate of corpora albicantia in his valuable
paper (1961) from several aproaches, and got the annual accumulation of corpora
albicantia is 1.43 in average.
And he compared the ages of the fin whales between the age from ear plug(biannual accumulation) and the age from ovary (annual accumulation rate is1.4), and got the exact agreement between both ages. Fujino (1963) also calculate
the corpora accumulation rate per 4 ear-plug laminations from the relation between
ear plug and corpora for the Antarctic fin whales separating the areas, and got theresult that the rate was 2.80 in Area-II (Laws's result), 2.31 in Area-III west, 1.91
in Area-III east, 1.84 in Areas-IV, and 1.60 in Areas-VI and I respectively. Then,the difference of the annual rate of corpora between Nishiwaki et al. ( 1958) and
Laws ( 1961) will be caused by the difference of races.
On the age determination of baleen plates, Ruud (1940, 1945), Tomilin
1940, 1945), Nishiwaki (1950 a, 1950 b, 1951, 1952, 1957), Chittleborough (1954,

AGE DETERMINATION OF FIN WHALE

511959), Laws & Purves (1956) and Laws (1961) all recognize that one ridge grows
in one year. Especially Nishiwaki (1952) tried to estimate the annual growth ofbaleen plates.
Although there are many hypotheses on the age determination of the baleen
whales, I think the age determination has not been established. Recently theage characters have been obtained from the long term recaptured fin whales(Ohsumi, 1962). Direct age of recaptured whale is able to be checked by the timefrom marking till recovery. And examinning the recaptured fin whales, above
hypotheses are not able to explain some of the actual data. We must re-examine
the age determination to solve the actual results on the age characters.
MATERIAL AND METHOD

Several methods were shown to examine the age determination of the whales
by Ohsumi, Kasuya & Nishiwaki (1963). Among them breeding experiment as usedby Sergeant (1959) and the time marking in the age characters of living animals as
used by Nishiwaki & Yagi (1953) are not able to use for the fin whale because of
the difficulty of the breeding of the whale. And I have no material for study ofthe seasonal growth of the age characters as used by Ohsumi, Kasuya & Nishiwaki.
(1963) on tooth of the sperm whale (Physeter catodon).
I examined the age determination in this report by the following three methods.
One is the examination of age characters from the recaptured fin whales. The
second method is the comparison between each age characters. The third
is a population dynamical examination on the age composition based on the
ear-plug laminations. Combining the results obtained from above methods, I
will examine whether the previous hypotheses are contradictory or not.
Biological material obtained by Japanese fleets from recovered fin whales are
based on the data by my previous paper (Ohsumi, 1962).
Baleen plates were collected with ear plug from 74 fin whales in the Antarctic
and northern part of the North Pacific, and the ridges appeared on the plates arecounted by eye. Ear-plug laminations are counted after the same preparation as
by Nishiwaki, Ichihara and Ohsumi (1959).
Ear-plug laminations are counted by the saffs of our Institute using dissectingmicroscope. Standardization of the reading ear-plug lamination is need as trying by Ichihara ( 1963). If the standardization is established and the reading isdifferent to the present reading, my following examinations are needed to be reexamined.
Number of corpora lutea and albicantia were counted with naked eye by slicing
the left and right ovaries.
Sexual maturity is determined by the investigation of ovaries or testes. For
females, those who have at least one corpus luteum or albicans in their ovaries are
determined to be sexually mature. For males, those whose weights of larger sideof testes are 2.5 kg or more than 2.5 kg are recognized as sexually mature.
Material for the comparison between ear-plug lamination and other age

52

S. OHSUMI

characters are all obtained from fin whales caught by Japanese fleets in the
Antarctic Areas IV and V in 1958/59 and 1959/60 seasons and northern part of the
Pacific during 1959 to 1961 seasons.
Ear-plug laminations are counted from 978 female fin whales caught in thenorth of east Aleutian Islands in seasons from 1959 to 1961, and the age compositions are drawn in the two cases of annual accumulation rate.
Estimated number of marked fin whales in the north of east Aleutian Islands
and the number of recaptured whale from the marked whales are gathered fromJapanese whale marking and recovery records during 1954 to 1962.
Number of female fin whales of sexually mature, immature and pregnant arecited from annual reports on the biological investigation of whales caught in the
North Pacific from 1954 to 1961.
EXAMINATION OF AGE DETERMINATION BY MEANS OF WHALE
MARKINGSOME POINTS TO BE CONSIDERED IN THE MARKING METHODFOR EXAMINATION OF GROWTH AND AGE OF WHALES

On the whale marking investigations many reports have been published. However, most of them are on the migration and movements. And the reports on theexamination on the age and growth by means of whale marking are relatively few,
and all of them are fragmentary. Mackintosh (1942) discussed the rate ofaccumulation of corpora albicantia in the ovaries on a recaptured fin whale. Omura &Kawakami (1956) studied the growth of the marked sperm whales. Ohsumi,
Nishiwaki & Hibiya ( 1958) discussed the growth and age of the fin whale in thenorthern Pacific from the data of whales recaptured by Japanese whalers. Chittleborough (1959) used results of marking for the study of age in the humpback
whale (Megaptera novaeangliae). Dawbin (1959) also studies whale marking as theevidence on growth rate of the humpback whales. Laws (1961) examined theannual corpora accumulation rate from 10 recaptured fin whales.
In the whales, it is entirely difficult to use the similar marking method as is
usually used in other animals liked as fishes or birds. That is to say, in the whales
except some porpoises and dolphins, we cannot catch and examine biologicallythe individual on board of ship before the marking and discharge. Therefore,
one of the weak points in the whale marking is the difficulty of the biologicalinvestigation at the time of marking. Although it is not so weak point for the
purpose to examine the movement of whales, it is the biggest defect to the study ofthe growth and age of the whales.
We usually estimate the species and body length of the whale at marking. At
that time, the estimation involves more or less errors, because we measure witheye the whales moving in the water. Sometimes we make mistakes in estimationof species. For example, a Japanese mark No. 4267 whales was recorded as a sei
whale (Balaenoptera borealis) at the marking, but it proved to be a fin whale in therecovery. It is difficult to distinguish between a sei whale and a Bryde's whale

AGE DETERMINATION OF FIN WHALE

53(B. edeni) at the time of marking, therefore, Bryde's whales were recorded as se1
whales in the marking records of our country. The mistake of this sort affects tothe calculation of population size by means of the marking method. It is also difficult to estimate the sexes of the whale at marking, except adult killer whale orsome other species. Furthermore, we cannot estimate the age of a whale at marking. When a calf with its mother is marked, we can estimate its approximate
age. But in other cases, we cannot estimate the age and collect the age characters of a whale at marking. Whale mark is only used as a correct artificial age
character from marking till recovery.
The next point is the scantiness of the marked and recovered whales. For the
purpose of the study of growth and age of whales by means of marking, the morerecovered whales we get, the better results are obtained. But, at first, we cannot
use many marks, for the marking investigation is very expensive. On the second,
the rate of hit on whales is relatively low. On the third, the rate of recovered whales
per marked whales is also relatively low.
The third point to be considered in the marking method for the study of growth
and age of the whale is the influences to the whale body by the marking. Whalemarking which we use is not what is called a marking but a sort of tagging, and a
25-28 cm long metal tube is inserted in the body of whales. The body parts of theinsertion is mainly the muscle of back, but sometimes the mark destinates the vertebrae or internal organ. Therefore, sometimes abnormality must be consideredin the growth and life of whales by marking. The example that 3 sperm whales
which had been marked in the adjacent waters to Japan were found floating deadshortly later shows a fatal influence of marking to those whales (Omura & Kawakami, 1956). The marks were inserted in the body cavity of those whales. There
are other some examples in which the marks influenced badly on the growth ofwhales.
The fourth point is the difficulty of investigation of recovered whales. The
best condition to investigate the marked whale is to discover the mark before theflensing and for that purpose streamer mark was made to try (Ruud, Clarke &Jonsgard, 1953; Omura & Kawakami, 1956), and a modified mark was tested
by Chittleborough & Godfrey (1957), because the earlier the mark is discoveredin flensing, the better investigation is made on the recovered whales. ·when
the mark is recovered in flensing, meat cutting or bone cutting, the mark is usuallychecked with the marked whale and we can investigate and collect the necessary
data and material for the examination of the age and growth. But if a mark is
recovered in cooker or reflegarator vessel, we cannot connect the mark with themarked whale. Fortunatley, in Japanese fleets, we flense the whales thoroughly,
because we use the whale for food, and we can recover many marks in the placeoutside of the cooker.
Marking is considered to be an artificial age character, and although marking
has a weak point that we cannot know the age of the whale before the time of marking, it has an advantage that we can confirm the elapsed time from marking
until recapture.

54

S. OHSUMI

If an age character increase in arithmetical progression, age at the time ofmarking is symbolized as x, elapsed time as t, and the annual accumulation rate isb, the size of age character at the time of recapture (y) is:y = b(x+t)

Then,

The smaller x is, and the larger t becomes, the smaller x/t becomes. Then, y/t becomes near b. Therefore, the useful material for estimation of the accumulation rate of age character by means of marking is desireble to be long elapsed timeand younger age until the time of marking.
EAR-PLUG LAMINATIONS OF RECAPTURED 'v\"HALES

Tables 1 and 2 show the number of ear-plug laminations, elapsed years and number of laminations dividing by the elapsed years for 59 fin whales recaptured by
Japanese fleet in the Antarctic and the northern part of the North Pacific, which
are listed in the paper of Ohsumi (1962).
If a whale mark fit a new-born whale, we can get an actually annual accumulation rate of ear-plug laminations, but this case is practically impossible. All whales
will be marked at some time after birth. And if we can record the time of marking in an ear plug, we shall get an accurate number of laminations per year bycounting the number of lamination from the record, but such recording is now
also impossible.
Then, as the laminations accumulated in the time from marking until recovery
are added to the laminations which were accumulated by the time of marking, themean values which are got dividing the total number of ear-plug laminations by
the elapsed time come to be more than the actually annual number of laminations.
The longer the elapsed time is, the shorter relatively is the time from birth
until marking. Therefore, the mean number of laminations per year approaches
to the actually annual increment of laminations as the period from marking until
recovery increases.
Fig. 1 shows the relation between the elapsed time and the mean number of
ear-plug laminations, and in addition shows the typical curves of mean number of
ear-plug laminations for the case of 4 whales which are, respectively, just born
(D, D'), 10 laminations (C, C'), 25 laminations (B, B') and 50 laminations (A, A')
at the time when they are marked. Broken lines (A', B', C', D') show the casein which the annual increment of ear plug is 2 laminations, and solid lines (A, B,
C and C) show the case in which the annual increment is one lamination.
In the whales which were recovered within one year, the apparent mean
numbers of laminations per year are relatively large. But in those which wererecovered after more than 2 years, we get relatively smaller figures.
There is a North Pacific fin whale (No. J. 6817) of which mean number ofAGE DETERMINATION OF FIN WHALE

55

TABLE 1. DATA FOR EXAMINATION OF ACCUMULATION RATE OF EARPLUG LAMINATION BY RECAPTURED FIN WHALES IN THE
ANTARCTIC (DISCOVERY MARKS)Mark No.

17860
22236
22417
22517
22526'30'33
24038
24083
24202
24361
24501
22517
24064
24349
24547
17876
17476
17903
198I3
20944
21077'90
2116I'72
20927'813347
198II
2I08I'5
21 I90
I7516
I4610
I7894
I7945
18049
18330
I8573
I6309
I4700
I2761
I4779
1462I
12798
I2677
30I3
3I84
2825
2932
3I71
5763

Sex
M
M

F
F
M
M
M
M
M

F
M

F
F
M
M
M

F
M

F
F
F
F
M
M
M
M

F
M

F
M
M
M

F
F
F
M

F
F
F
F
F
F
F
M

F
M

Elapsedtime (A)(Yr.-Mon.)

0-2
0-1
0-0
0-1
0-1
0-1
0-1
0-0
0-1/2
0-0
0-2
0-2
0-2
0-3
1-1
1-2
I-I
1-1
I-1
I-1
1-1
1-2
2-4
2-2
2-I
2-I
3-I
3-1
3-2
3-1
3-2
3-1/2
3-3
4-0
4-I
4-2
4-3
5-2
5-4
6-4
24-11
24-II
25-0
25-0
25-0
24-lI 1/2

Estimated
No. ofbody length
Body length
ear-plugat marking (ft.) at recapture (ft.) laminations (B)

59
66-67
65
70
67
60
70
70
62
66
66-65
70
55
70
58
63
70
74
65
67
54
65
65
63
68
64
64
75
70
66
67
62
66
68
62
63
65
68
70-75

57
60
66
73
69
63
64
65
66
68
62
70
62
70
63
67
69
69
75
74
71
64
64
63
66
62
72
66
67
67
65
67
68
73
77
67
73
69
73
72
70
69
71
66
72
69

7
8
18
22
31
10
8
10
16
24
6
16
7
53
24
16
10
I5
60
22
19
6
8
9
15
9+ (3)
18
21
2I
14+ (2)
57
I2
24
42
29
I4
67+
I5+ (2)
48
3I
33
36
38
38+ (3)
28
34

B/A

22.2
I3.7
9.23
I3.8
55.4
20.3
I7.5
5.15
3.44
4. I5
7.20
5.76
5.84
6.8I
6.63
5.17
18.0
3.96
7.38
I0.5
7. I I
3.36.
15.8+
3.29
9.00
4.90
1.33
1.45
1.52
1.64
1.12
1.37

S. OHSUMI

56

TABLE 2. DATA FOR EXAMINATION OF ACCUMULATION RATE OF
EAR-PLUG LAMINATION BY RECAPTURED FIN WHALESIN THE NORTHERN PART OF THE NORTH PACIFIC(JAPANESE MARKS)Mark No.

Sex

7968
8416
8433
8434
8567
8618
8632
7988
6801'2
6799
7962
6834
6831'7
7975
7686
4552
6264
6807
6939
7708
6923
5979
8089
6808
4558
7026
7200
6274
6835
7170
6504
6782'53243
6471'7'8'80
6498
7705
7727
7737
7541
6817
6977
3391
6044
7025
4393
6052
6098
4615
4452
6172
4564
6097
5960
4146
3287'3343
4651

F
F
F
M
F
M
F
M
F
M
F
M
M
M
F
F
M
F
F
F
F
M
F
F
M
M
M
F
M
M
F
F
F
F
M
F
F
M
F
M
M
M
F
M
F
F
M
M
M
F
F
M
M
F
M
M

Elapsedtime (A)(Yr.-Mon.)

0-0
0-0
0-0
0-0
0-0
0-0
0-1/2
0-0
0-10
0-10
0-11
0-9
0-10
1-0
1-1
1-10
1-10
1-10
1-11
1-11
2-0
2-0
2-1
2-9
2-10
2-10
2-10
2-10
2-10
2-11
2-11
2-11
3-0
3-0
3-0
3-0
3-0
3-1
3-1
3-10
3-10
3-11
4-10
4-10
4-11
4-11
4-11
4-10
5-0
5-1
5-9
5-9
5-11 1/2
6-0
6-11
6-11

No. ofEstimatedbody length
Body length
ear-plugat marking (ft.) at recapture (ft.) laminations (B)

62
62
65
53
60
63
66
64
60
60
61
69-70
61-62
64
62
60
60
56-57
62
55-57
62
60
73
65-66
65
60
54
60
60-61
55
63
60
(70)
54-55
61
66-68
58
60
60
57
55
63
65
55
60
62
52
56
60
62
50
60
65
65

66
57
63
61
69
61
73
59
58
59
64
61
58
61
57
62
56
57
64
62
64
58
68
64
62
62
58
62
61
59
58
61
55
57
60
60
65
64
58
59
61
64
67
63
65
67
62
61
59
62
56
65
64
68
64
67

9
4
9
6
31
19
12
6
7
13
12
28
14
50
10
II

8
5
41
8
32
9
13
15
21
14
8
8
16
9+
7
8
13
12
12
13
19
10
6
6
12
27
21
13
21
9+
9
12
10
II

10
23
15
16
16
43

B/A

8.43
15.7
13.2
37.3
16.9
50.0
9.23
6.01
4.37
2.73
21.5
4.19
6.00
4.50
6.25
5.45
7.42
4.95
2.83
2.83
5.65
3.08+
2.40
2.74
4.33
4.00
4.00
4.33
6.33
3.25
1.95
1.57
3.13
6.89
4.35
2.69
4.27
1.83+
1.83
2.48
2.00
2.16
I. 74
4.00
2.52
2.67
2.31
6.22

AGE DETERMINATION OF FIN WHALE

57

laminations per year is 1.6, although it was recovered only 3 years and 10 months
later. According to the record at marking, the whale was estimated as 57 feet long,and it might be over one year old at marking. When the age at marking is added on the elapsed time, mean number of laminations per year becomes under
1.3.

IOI
I I

20

"'
0

\

H· \

(})

I I

\o I

I

-0

19 I

I

>(})

"'

Q.

0

(})

15

~

'\
18 I

(})

Q.

"'

c

I

u

·E

~

tI \I \I

Ol

\

\

;;;
::>

c

0

',
',

.....

\

J ""''-....,~

lo •a

(l)

E

\
\

\

0

..0

\

0

\
•

~

0

\

I
\

10

::>

\

5

o
<f,

'

',,

''A-!__------------.a,, "'~'--Ji~_...._ • ....._ c'~--------------·-=-::::-,,-:--.-----=~a • •o"-;!2._ - - _ _-~-1.-).~D'~-----------------

t--~~~~~-~~~~~~~~~~~~~~~---'~~~D

5

15

20

25

Elapsed years from marking

Fig. 1. Change of number of ear-plug laminations per elapsed years according to theelapsed years from marking until recapture.
A, A': 50 laminations at marking, B, B': 25 laminations at marking, C, C': 10 laminations at marking, D, D': 0 lamination at marking (birth at marking), A, B, C, D:
One lamination accumulate a year, A', B', C', D': Two laminations accoumulate ayear. Open circle: Antarctic fin whale, closed circle: North Pacific fin whale.

In the North Pacific, Nos. J. 7541, J. 6098 and J. 4564 whales are also calculated the mean number oflaminations per elapsed years as under 2, notwithstanding their elapsed times are within 6 years. Further, in the Antarctic, 6 long termmarked fin whales from which ear plug were collected had been recaptured by
Japanese fleets by 1961/62 season. The mean numbers of laminations per elapsed
year of the 6 whales are all under 2 (1.33 in No. E. 3013, 1.45 in No. E. 3184,
1.52 in No. E. 2825, 1.64 in No. E. 2932, 1.12 in No. E. 3171, and 1.37 in No. E.
5763). The tip of ear-plug core of No. E. 2932 whale is broken, but the broken
laminae layers are estimated to be less than three, and the total lamination areS. OHSUMI

58

estimated to be 41.
There is no whale of which mean number of ear-plug lamination is calculated
as under 1.0 per year.
The mean number of ear-plug laminations per year calculated in this way,should be more than 2 for all recaptured whales, if they are actually laid down
biannually. However, in view of these examples, the annual increment of ear-pluglaminations is estimated to be under 2 for the marked fin whales, perhaps near one
lamination per year. The solid lines in this examination also support the estimationthat the accumulation rate of ear-plug lamination must be under two annually,
and may be near one per year.
TABLE 3. ESTIMATION AND COMPARISON OF THE AGE COMPOSITION
OF RECAPTURED FIN WHALES AT MARKING BETWEEN TWO CASES
OF ANNUAL ACCUMULATION RATE OF EAR-PLUG LAMINATION
Annualaccumulation
rate ofear plug

Elapsed years(actual figures)
Age atmarking

f
One

Two

l

51<
26-50
11-25
6-10
0-5
0>
Total

51<
26-50
f 11-25
6-10
0-5
0>

l

Total

0

1-2

2
7

Elapsed years(per cent)

5-7

Total

0

1-2

3-4

4
10
10
2

3-4
2
2
12
7
6

3
4
6
3

4
11
33
34
12

4.6
9.1
31.8
50.0
4.6
0.0

3.7
14.8
37.0
37.0
7.5
0.0

6.9
6.9
41.4
24.2
20.7
0.0

5-7
0.0
18.8
25.0
37.5
18.8
0.0

22

27

29

16

94

1
4
8
8
6

2

2
7
11

3.7
14.8
29.6
29.6
22.2
0.0

6.9
3.4
27.6
31. 1
24.2
6.9

0.0
12.5
25.0
6.3
43.8
12.5

27

4
9
27
29
21
4
94

4.6
9.1
31.8
50.0
4.6
0.0

22

2
4
1
7
2
16

11

8
9
7
2
29

Table 3 and Fig. 2 show the estimated age composition at the time of marking
by recaptured fin whales. Estimated age at marking is calculated from numberof lamination at recapture, elapsed time and the annual accumulation rate of earplug laminations. I calculated the estimated age in two cases where annual accumulation is one and two. The comparison of age composition at marking is
made in elapsed year classes 0, 1-2, 3-4 and 5-7. According to Fujino (1960),
the estimated size distribution of marked whale at the time of marking is not so
different from that which were caught, although young whales distribute little rather
more than the whales caught and the markings of whales are considered to be made at
randum from the stock in the whaling ground. If so, the estimated age distribution
at the time of marking must be not so different in each season. Now, as shown in
Fig. 2, the age composition at the time of marking is not so changed according to
the elapsed years for the case of one-lamination age. Ratio of the age class of 0
to 5 at the time of marking increases according to the elapsed years. This can

AGE DETERMINATION OF FIN WHALE

59

be explained that small whales are not caught soon after marking, but they growto captuable size as the time goes by. On the contrary, in the case of two-laminations age, estimated age composition of marked whale at the time of marking changes
by the increment of elapsed years. And in 5 to 7 elapsed years classes, the composition of under 5 years old class exceed the half of total whales. This is not able to be
explained, because the age distribution of marked whales must not be so different
from the whales caught at the time of marking. Besides, there exist the whales
under 0-year old at the time of marking in the case of two-laminations age. They
must be marked before birth. This is not practical.

75

11-25

75
l l-25

'J!_
c
0

50

50

·~

0
Q.

E

3

6-10
0-5

ID

"' 25

<(

25

0-5

0

2

4

6
Elapsed years from

0

2

4

6

marking

Fig. 2. Change of estimated age composition of recaptured fin whale at the time ofmarking according to the elapsed years from marking. Left figure : Annual rate of
ear-plug accumulation is one lamina, Right figure : Annual rate is two laminae.

However, Chittleborough (1959) reported that a male humpback whale wasmarked when its body length was approximately 30 feet (he estimated to be anyearling) and it was recaptured 4 years and 10 2/3 months later. The ear plug
contained as 12 laminations. From the above result, he agreeded with the biannual
formation of ear-plug lamination. I am afraid that the whale was truly yearling.
The estimate body length is sometimes different with the actual length. And
there is individual variation in the body length. Dawbin (1959) also reports amarked humpback whales which had been at least one year old at marking andwas recaptured 19 months later. Examining its baleen plate and ear plug, hestates that the result are consistent with the view that ear plugs develope twolaminations per year.

60

S. OHSUMI
EXAMINATION OF THE AGE AT SEXUAL MATURITY
BY THE MARKED WHALES

Sexual maturity is one of the remarkable stages in the life history of whales.
Besides, it is used for classification of broad age groups. Therefore, it is considered
to be a kind of age character. On the age at sexual maturity of the fin whale,
Mackintosh & Wheeler (1929) state that an examination of sizes of young whales atdifferent times of year suggests that sexual maturity is reached about 2 years
after birth. Studying the baleen plates, Ruud (1945) describes that it is apparent
that majority of the northern fin whales attain sexual maturity at an age of 3
years. From the similar method, Nishiwaki (1952) states that females reach tosexual maturity in the pairring season following the fourth birth day and themales at the age of about 3 years and a half in the case of the southern fin
whales. In the modified method of surveying baleen plates, Van Utrecht (1956)
obtained a result that the age at which the female becomes sexually mature lies
between 5 and 6 years.
TABLE 4. SEXUALLY MATURE AND IMMATURE FIN WHALES IN
EACH ELASPED YEARS FROM MARKING UNTIL RECAPTURE(INCLUDED DATA FROM TABLE BY LAWS, 1961)
Elapsed years from marking

I

Males

{
{s
{s
s

M
I

Females

M
I

M+F

M
Total

0

2

8 4
7 2
8 8
8 8
5 4
13 6
16 12
12 6
21 14
49 32

2
3
2
1
8
4
I
II
16

3
3
5
5
4
6
6
7
JI
24

4

5

6

7

11

12

17

19

20

21

23

24

25

3
2
2

3

5
7

2

5
4
3
6
13

2

4
I
6
8

4

2
2

5

Total
19
15
32
25
16
57
44
31
90
164

Remarks: I: Sexually immature (under 2.4 kg in larger testis for male, 0 ovulation for female).
S: Soon after sexual maturity (2.5-5.0 kg in testis for male, 1-2 ovulations for females).
M: Sexually mature (over 5.1 kg in testis for male, over 3 ovulations for females).

Since the discovery oflaminations in ear plug, Laws & Purves (1956) reported
that sexual maturity was reached at the age from 4 to 6 years in the male from theNorth Atlantic. Nishiwaki (1957) learned in the same method the age of sexual
maturity of the southern fin whale was 4 or 5 years. Ohsumi, Nishiwaki & Hibiya( 1958) state that if two laminations are formed every year, the fin whale in the northern Pacific will attain at sexual maturity in early term of seventh year after birth, andthe precocious will be mature sexually by the fifth year, furthermore, by the eighthyear all the fin whales will attain at sexual maturity. Purves & Mountford (1959)
give a figure of 4 and a half years for males and 5-6 years for females. Laws ( 1961)
also shows the percentage frequency of sexually mature females in different agegroups from ear plug (biannual rate), and get that the age corresponding to 50%
of mature females is about 5 years.

AGE DETERMINATION OF FIN WHALE

61

Above results are not lead with the absolute age of whales. Table 4 shows
the number of animals which are determined their sexual maturity among the recaptured fin whales. Data used for this purpose are from Ohsumi (1962) and Laws
( 1961). I divided sexually mature whales into two groups, that is, soon after
maturity and fully mature groups.
100

80
Mature'2Z600<.!":·

9
E

0

40

v

Soon after maturity""---..:~
'-.
'-..

20

'-..

'-..

'--,
'-.

Immature

'-.

'--,
'-..

2

3

4

5

6

7

8

9

l0

11

Elapsed years from marking

Fig. 3. Change of composition of sexually mature and immature fin whales recaptured
according to elapsed years, and estimation of age at sexual maturity. Chain line :Regression line of immature rate, Broken line: Estimated decreasing line of immature
rate assuming the age at sexual maturity as 5 years.

And Fig. 3 shows the change of the composition of sexually immature andmature animals according to the elapsed years calculated from Table 4. In 0year group which were recovered within 3 months later, the rate of sexually immature whales is 32.7%. This is almost the same ratio as the usually caught whalesin the factory ship whaling. But as the time elapses, the rate of immature whales
gradually decreases. There is a sexually immature female whale (J. 4564) which
was recovered 5 years and 9 months later. This whale certificates the existence ofan individual which is sexually immature in the age of at least 5 years and 9 months. This whale had been estimated to be 60 foot long at the time of marking.
Considering the error of the estimation, the whale is thought to be at least 1 or 2
years old at that time. If so, this whale must be still sexually immature in theage of 7 or 8 years.
There were several recovered whales which are estimated to be soon after
sexual maturity more than 3 years later from marking. One of them is a female
recovered 3 years later (J. 3243). It has only one corpus albicans in the ovaries.
Considering from the existence of vaginal band and immature mammary gland,
this whale is assumed to be soon after sexual maturity (puberty as defined by Chittle-

62

S. OHSUMI

borough, 1954).
Regression line is calculated from the elapsed time and the composition
equation of immature whales. It is:

Y = -3.68X +36.49
Where, Y is a percentage of immature whales, and X is the elapsed years. From thisequation, following values are calculated : The percentage of immature whales is36.49 at the time of marking (X =0), and the elapsed time is 9.93 years when percentage of immature whale is 0.
Thus, we can estimate that the age at sexual maturity is about 10 years fromthe examination of age at sexual maturity by the recaptured fin whales. Broken
line in Fig. 3 is a estimated declining line of sexually immature ratio, when the age
at sexual maturity is considered to be 5 years as many authors reported. This
broken line does not fit the actual change of composition of sexually immature
animals. We must consider that there is individual variation in the age at sexual
maturity, but usually whales are marked somewhile later from birth. And there
are 5 immature animals (25%) among 20 animals which were recaptured after 4
and 5 years from marking. Even among 10 recaptured animals after 6 and 7 years'
elaption from marking, there is one immature animal (10%). This phenomenon
may mean that the age at sexual maturity is longer in fin whale than those which
are recognized today by us, and I estimate from the change of composition of sexually immature animals according to elapsed years that the age at sexual maturity
is about 10 years.
On the humpback whale, Chittleborough (1959 b) reported an sexually immature male which was recaptured 4 years and 1 month later.
ANNUAL ACCUMULATION RATE OF CORPORA ALBICANTIAIN THE RECAPTURED FIN WHALES

Chittleborough (1959 a) reportes "One female humpback whale marked when
it was accompanied by a calf was killed 9 years later. The ovaries then obtained 10
corpora albicantia, so that if this female had been marked at the end of its firstpregnancy, the average rate of ovulation would have been 1.0 ovulations per year."And calculating from the data by Chittleborough (1959 b), a mean number ofovulations per year for a marked humpback whale recovered 17 and a half years
later is 0.9 ovulations.
By a result of a fin whale recovered 6 years and 2 months later, Mackintosh(1942) states that one cannot draw any final conclusion, but in this one, since it
had only 8 corpora lutea, the rate of accumulation (mean number of ovulations is
1.3 per year) cannot have been much more than about one a year, and since there
was no clue to the whales age at the marking, the rate of accumulation may havebeen even slower.
Laws (1961) checked the corpora accumulation rate by 10 recaptured fin
whales. He calculated the mean elapsed period as 13.8 years (ranging from 2 to
24 years) and the mean corpora as 15.7 (ranging from 3 to 40). Then he gets theAGE DETERMINATION OF FIN WHALE

63

TABLE 5. DATA FOR EXAMINATION OF ANNUAL ACCUMULATIONRATE OF CORPORA ALBICANTIA IN THE MARKED FIN WHALESCAUGHT IN THE ANTARCTIC (DISCOVERY MARKS)Mark No.

24350
18087
21196'98
14576
19843
20502'4
21187'21200
24064
24349
19837'9
20735
17903
19746
19835
19840
20927'8
15388
17839
17457
17516
18073
19921
13278
13481
6472
3507
3103
2627
5594
*10504*12870* 696* 7972* 4938* 6818* 1199'1203}* 1300Elapsed time
(Year-Month)

Estimated bodylength atmarking (ft.)

0-0
0-1
0-1
0-2
0-2
0-2
0-2
0-2
0-2
0-3
0-3
1-1
1-1
1-1
1-1
1-2
1-2
1-2
2-1
3-1
3-3
3-2
5-2
6-2
20-1
20-11
24-11
24-1
22-11
2.23
3.23
6.21
I 1.13
12.06
17.05
19.12

* Cited from Table 30 by Laws (1961)

61
66
70
60
66
62
70
70
55
66
67
70
60
63
67
65
62
65
64
62
60
68
60-65

Body length
at recapture (ft.)

No. ofcorporaNo. of corpora
per elapsed
year

63
73
64
69
64
66
73
70
62
64
66
69
65
69
69
64
65
66
71
72
68
63
73
73
71
70
70
69
74
71
70
76
69
73
75

19
18
0
0
0
1
0
2
6
0
2
0
6
3
2
0
15
13
9
23
15
32
12
10
3
8
5
14
40

0.60
1.33
0.53
4.48
0.93
1.29
0.45
1.16
2.33

76

II

0.58.

0
12
4
3
0

0.92
0.00
1.85
5.53
0.00
I. 72
0.00
2.88
0.97
0.60
0.00
2.90
2.11
0.45
I. JO

64

S. OHSUMITABLE 6. DATA FOR EXAMINATION OF ANNUAL ACCUMULATIONRATE OF CORPORA ALBICANTIA IN THE MARKED FIN WHALESCAUGHT IN THE NORTHERN PART OF THE NORTHPACIFIC (JAPANESE MARKS)Mark No.

Elapsed time
(Year-Month)

Estimated bodylength atmarking (ft.)

Body length
at recapture (ft.)

4266
7968
8416
8433
8632
4684
4802
7720
8567
4270
4658
4543
6815
6843
6801'2
7962
4552
6042
G995
6939
7708
6807
7686
4267
6923
6274
6504
6782'5
6808
8089
3243
3213
64 71 '7'8'80
7705
7270
7727
7541
4393
6044
6052
6172
4564
4146

0-0
0-0
0-0
0-0
0-1/2
0-1
0-1
0-1
0-0
0-2
0-11
0-11
0-10
0-10
0-10
0-11
1-10
1-8
1-10
1-11
1-11
1-10
1-1
2-0
2-0
2-10
2-11
2-11
2-9
2-1
3-0
3-2
3-0
3-0
3-2
3-0
3-1
4-11
4-10
4-11
5-1
5-9
6-0

68
62
62
65
66
65
71
64-66
60
68
61
62
62
62-63
60
61
60
55
57
62
55-57
56-57
62
45
62
60
63
60
65-66
73
(70)
60
54-55
66-68
60
58
60
60
65
62
56
60
60

62
66
57
63
73
61
65
66
69
63
58
66
60
56
58
64
62
64
65
64
62
57
57
63
64
62
58
61
64
68
55
63
57
60
60
65
58
65
67
67
62
56
68

No. ofcorpora

1
0
0
4
2
1
7
11
0
0
9
0
0
7
2
1
9
15
14
0
0
0
3
8
0
0
6
3
1
16
0
3
4
0
5
7
2
0
0

No. of corpora
per elapsed
year

0.00
9.81
0.00
0.00
8.08
2.18
0.55
5.40
8.27
7.30
0.00
0.00
0.00
1.50
4.00
0.35
0.00
0.00
2.18
1.44
0.33
5.06
0.00
1.00
0.32
1.33
0.00
1.02
1.45
0.41
0.00
0.00
0.17

AGE DETERMINATION OF FIN WHALE

65

result that mean increment of corpora is likely to be 1.14 per year if fin whales aremarked on average at about the time of puberty.
Table 5 and 6 show data for examination of corpora accumulation rate byrecaptured fin whales. Most of data are obtained by Japanese fleets in the Antarctic and the northern part of the North Pacific which are listed in the paper of
Ohsumi (1962). In addition to them, I cited the data from Table 30 of the paperby Laws (1961).
I
10

I
I
I

I

.1

I
I
I

8

I

\

.~

I
\

\

I

\

~

\

I
I
I
I

6

\
\

0. \\

\

\

.

'\

\

:t( \

•

4

\

0

2

•

',

'

',
0

•

'O

''

'-......
0','- ------',..._ /{

.....

--

B - -~--------:t(__, ____ e---,x-------------- ,.•

0

0

-----

-

---

0

0

M

---

•..
. .~
.
ft'•.,- ~-·5.

-----~.,., -----------~
D~--------

c

o~

-----

-------- ------

c'

:a:
10

D

15

20

25

Elapsed years from marking

Fig. 4. Change of number of ovulations per elapsed year according to the elapsed years
from marking until recapture. A, A': 25 ovulations at marking, B, B' : 10 ovulations
at marking, C, C': Just sexually mature at marking, D, D': Just birth at marking,A, B, C, D : Age at sexual maturity is 5 years, and 0.9 ovulations per year (Nishiwaki
et al., 1958), A', B', C', D': Age at sexual maturity is 5 years, and 1.43 ovulations per
year (Laws, 1961).

If the time of marking coincides with the attainment of sexual maturity of themarked whale, we can get the actual annual-increment of corpora albicantia,
dividing the number of ovulations by the elapsed years. But it is a very rare case,and most whales will be marked after or before the time of sexual maturity. Whena sexually mature whale is marked, the mean number of ovulations per year, given
by dividing the number of ovulations at recovery by the elapsed years, is more than
the actually annual number of ovulations. On the contrary, when a sexually im-

66

S. OHSUMI

mature whale is marked, the mean number of ovulations per year should be lessthan true annual number of ovulations. However, as the elapsed time from marking
increases, the number of ovulations accumulated before marking becomes relatively
small, and· mean number of ovulations calculated must approach to the actuallyannual rate of ovulations.

10

0

8

">-

-a·

• •
•

Q)

Q_
0

Q)

6

(])

0..

"'c

0

~
=>

4

>
0

0

0
(])

...n
E
=>
c

2

•

!\'

•

'6 "' •
0-:ci:•915> .. '4>

•••

•

P'.

B"

~c--~~~~~~~o~~-o~~~-_..•____.,;Jr."'-~i---.c"--_~-------------_-_-D-"-:=_-:=_-:=_-:=_-:=_:_~~:..._---'--o-0

5

10

15

20

25

Elapsed years from marking

Fig. 5. Change of number of ovulations per elapsed year according to the elapsed years
from marking until recapture. A": 25 ovulations at marking, B": 10 ovulations at
marking, C": Just sexual maturity at marking, D": Just birth at marking. A", B",
C", D": Age at sexual maturity is 10 years, and 0.5 ovulations per year.

Fig. 4 shows the relation between the elapsed years from marking till recapture
and the mean number of ovulations per elapsed year. The range of the mean
number of ovulations in marked whales which were recaptured shortly after, arelargely distributed. The reason is that the number of ovulations before marking
greatly influences the value obtained. However, with the lapse of time, the range
becomes narrow, and more than 19 years later, mean annual number of ovulations in 6 Antarctic fin whales are within the limits of 0.45 and 1.33. The meanvalue of the 6 individuals is 0. 77.
The broken line (A', B', C', D') in Fig. 4 is a case where the age at sexual
maturity is 5 years and the annual accumulation rate of corpora is 1.43 as calculatedby Laws (1961), and solid line (A, B, C, D) is another case where the age at sexual

67

AGE DETERMINATION OF FIN WHALE

maturity is 5 years and the annual rate of corpora is 0.9 as calculated by Nishiwaki
et al. ( 1958) from the relation between the number oflamination in ear plug and thenumber of ovulation when annual accumulation of ear-plug lamination is assumed
as two. A, B' ; B, B' ; C, C' and D, D' is the cases of 25 ovulations, 10 ovulations justpuberty and just birth at the time of marking. According to this figure, brokenlines do not fit the actual values, and there are 8 individuals which are under D' line.
This means that the individuals had been marked before birth. This hypothesis isinconsistant with the actual data, for they must have been marked after birth. Solidlines are more suitable than the broken line, but they have the same inconsistanceas broken line. Therefore, above two theories are not able to explain the actual
figures obtained from recaptured fin whales.
TABLE 7. ESTIMATION AND COMPARISON OF OVULATION COMPOSITION
OF RECAPTURED FIN WHALES AT MARKING BETWEEN TWO CASES OF
ANNUAL RATE OF OVULATION
Annualrate ofovulation

0.50

1.43

Elapsed years (actual figures)
Ovulation
at marking.

(
J

l

26<
11-25
6-10
1-5
0
Total

26<
11-25
6-10
1-5
0
Not birth
Total

0

1-2

4

2
6
6
10
24

I

8
8
21
4
8
8

2
4
5
13

3-4

5-7

I

7
8
16

1
14

3
4
9

5
2

21

24

16

9

10-25

Elapsed years (per cent)

0

Total

1-2

3-4

5-7

10-25

}

2
2
2
2
9

19.0 8.3 6.3 11.1 30.0
1010
} 42.9 50.0 43.7 44.4 40.0
26
32
38.1 41. 7 50.0 44.4 30.0
79

3
5
9

8.3 6.3
10.0
8 } 19.0
6} 42.9 37.5 6.3 22.2 0.0
1538.1 54.2 87.4 55.6 30.0
43
0.0 0.0 0.0 22.2 60.0
779

Fig. 5 shows the change of mean number of ovulations per elapsed year in thecase where age at sexual maturity is 10 years as shown in previous section and theannual accumulation rate is 0.5 as discussed in the following chapter. According
to this hypothesis, the curves (A", B", C" and D") fairly fit the actual values.
Age composition of marked whales is shortly less than the whales caught (Fujino,1960). According to Laws (1961) and Mackintosh (1942), the average numberof corpora of fin whale is calculated as 12.5 in adult female in 1939""41 season andthe ratio of immature whales is 15.1%in1936-37 Antarctic pelagic whaling. Therefore, the mean number of corpora including immature whales in 1936""40 season
is calculated to be 10.6. If the mean number of corpora in ovaries of marked fin
whales is 10 in the Antarctic pre-war seasons and the annual rate of corpora accumulation is assumed to be 0.5, mean corpora divided elapsed years after 20 to 25
years' elaption is calculated to be 1.0 to 0.9. This mean values agree relatively
well with the mean number of corpora calculated from 6 recaptured fin whales

68

S. OHSUMI

after 19"'25 years elaption (0.77). If annual accumulation rate is 1.43, the former values must be comes between 1.93 and 1.83. This is larger than the actual
values.

75

75
1-10 ov.

"J'!.
c

~
0

"-

50

50

E
0

u
c

~
0

"0 25

25

oov.

2

' 4

6

10-25

2

4

6

10-25

Elapsed years from marking

Fig. 6. Change of ovulations composition ofrecaptured fin whales at the time of marking
according to the elapsed years from marking. Left: Annual rate of ovulation is 0.5 andthe age at sexual maturity is 10 years, Right: Annual rate is 1.43 and age at sexual
maturity is 5 years.

Now, Table 7 and Fig. 6 show the estimated corpora composition at the timeof marking by recaptured fin whales. Estimated number of corpora at marking is
calculated from number of corpora at recapture, elapsed time and the annual rateof corpora accumulation. And I calculated the estimated corpora number in twocases where annual accumulation rate is 0.5 and 1.43. The comparisons of corpora
composition at marking is classified in elapsed year classes 0, 1-2, 3-4, 5-7 and 10-25.
As repeatedly said, the estimated size distribution of marked whale is not so different from that which caught. If so, the estimated corpora distribution at the time ofmarking must be not so different in each season. According to Fig. 6, the estimatedcorpora composition is not so changed by 7 years of elaption from marking in thecase of annual accumulation rate is 0.5. In the 10-25 elapsed years group, estimatedimmature whale is smaller than the former years classes. But this can be explainedthat they are pre-war marked whales, and in pre-war seasons the composition oflarger whales must be larger than recent season. And the estimated compositionof immature class of pre-war marked whale (22%) fairly agrees with the immature
rate (15.1 %) of pelagic catch in 1936-37 season obtained by Mackintosh (1942).
On the contrary, in the case of which annual accumulation rate is 1.43, estimatedAGE DETERMINATION OF FIN WHALE

69

corpora composition at the time of marking changes remarkably by the incrementof elapsed years. And over 4 elapsed years classes, the percentage of immature
whales attaines over 75°/o. This is not able to explain the actual age compositionof the whales in the sea. Besides, there exist the whales before birth at the time ofmarking in the case of annual rate of 1.43, and the rate attains to 55% in 10-25
elapted years class. This is not practical. Thus, this examination also support
the estimation that the annual rate of corpora accumulation must be under 1.43,
and may be near 0.5 per year.
However, above examination of annual rate of ovulations is considered as meanvalue. And we must remember that there are indivdiual variations in the ovulation rate as shown by Nishiwaki et al. (1958), and racial variation as shown by
Fujino (1963).

RELATION BETWEEN EAR-PLUG LAMINATION AND
OTHER AGE CHARACTERS
RELATION BETWEEN EAR-PLUG LAMINATION
AND NUMBER OF OVULATION

Fig. 7 shows the mean number of ovulations (corpora lutea and albicantia) in eachclass of ear-plug lamination for the fin whales caught in Antarctic Areas IV and
V in 1958/59 and 1959/60 seasons.
As shown in this figure, there is linear relation between number of laminations
and number of ovulations except the old age. An equation is given from this line.
It is
Y = 0.49X-4.28

Where, Y is the mean number of ovulations, and X is the number of ear-plug laminations. This equation is similar with that obatined by Nishiwaki, lchihara &Ohsumi (1958).
Thus, coefficient of X is given as 0.49. If the accumulation rate of ear-pluglamination is one per year, the coefficient, that is, 0.49, shows the annual ovulation
rate. Notwithstanding two ovulation rates are calculated independently by examination of ovulation of recaptured whales and by relation between number of
ear-plug laminations and number of ovulations, the both agree closely with eachother. This is, in other word, one of the certification that accumulation rate of
ear-plug lamination is one per year.

SEXUAL MATURITY AND NUMBER OF EAR-PLUG LAMINATIONS

Fig. 8 shows the change of ratio of sexual maturity according to increment of earplug laminations for the Antarctic fin whales caught in Areas IV-V in 1958/59 and1959/60 seasons. Individual stages of sexual maturity have been estimated fromthe standard described in previous chapter.

S. OHSUMI

70
30

25
.,.,
c

g_
a

20

=>

>

a

0
ill

_o

15

E

=>
c

c

a
QJ

2'

10

5

10

20

30

50

40

60

90

70

Number of ear-plug laminations

Fig. 7. Relation between number of ear-plug laminations and the numbr of ovulationsin the Antarctic fin whale in Areas IV-V.

--

JOO

•
/
0

75
I

I

I

I

I

I

I

/

• ,.......-o
5'"

0

/

/

h

50 -------------------------------.- ----i
I
I

I

a

=>
x
QJ

(/)

/

o /
/
_,,.,,

2

4

6

/

"?

:

:

'I

/

I

lI

I

I

I

I

I
I
I

I
I
I

l
t

l
I

I

.,,,,,./
O

8

/1
I

: /(:,

0? ~I

•

•

25

I

I

I

10

12

14

16

18

Number of ear-p.J.ug laminations

Fig. 8. Percentage of sexual maturity in successive ear-plug laminations, on the Antarctic
fin whales in Areas IV-V. Open circles and broken line: Females, Closed circles andsolid line : Males.

AGE DETERMINATION OF FIN WHALE

71

Males start to attainment of sexual maturity from 4 laminations, and by 14
laminations all individuals attain to maturity. Females attaines to maturity later
than the males, they start from 6 laminations and end by 15 laminations. The
number of ear-plug laminations corresponding to 50% of maturity is 9.4 in males
and 10.7 in females. In Fig. 7, the number oflaminations at the point where one
corpus level accross the average line is 11 laminations.
On the relation between number of ear-plug laminations and sexual maturityof fin whales, Laws & Purves (1956) compared testes weights and ear-plug laminations, and they concluded that sexual maturity is attained at 8-12 laminations in
the case of males in the North Atlantic fin whales. Nishiwaki ( 195 7) compared thenumber of laminations with number of corpora in ovaries of 34 Antarctic fin whales
and he found that 10 laminations corresponded to one corpus. Nishiwaki, Ichihara& Ohsumi (1958) tablated the frequency of sexually immature and mature fin
whales caught in the Antarctic and North Pacific in different number of ear-pluglaminations in Apendix. And they said that male and female fin whales matured
at about 11 laminations. Purves & Mountford (1959) draw growth curves ofmales and females in the Antarctic areas I and II where ages are based on ear-pluglaminations, and estimating body lengths at sexual maturity as 66 feet in females
and 63 feet in males, they concluded that the age at sexual maturity is 10-12 laminations in the females and 9 laminations in the males. Laws (1961) shows the percentage of sexually mature females in successive age groups based on ear-pluglaminations, and he obtaines that age corresponding to 50% of mature female isabout 5 years (10 laminations).
Summarizing the above results, the number of ear-plug laminations at sexual
maturity may be concluded to be 10-11 in the females and 9-10 in the males respectively in the case of fin whales.
Now, in the examination of age at sexual maturity by recaptured fin whales,
it is estimated to be about 10 years. This result is based on absolute time as elapsed
years from marking until recapture. On the other hand, the number oflaminationsat sexual maturity is obtained independently as 9-11 laminae. Connecting these
two results, I can get a conclusion that the annual accumulation rate of ear-pluglaminations must be near one. This conclusion also coincides with the results
obtained by the examination of annual rate of ear-plug laminations from recaptured
fin whales.
RELATION BETWEEN EAR-PLUG LAMINATIONS AND RIDGESON BALEEN PLATE

On the relation between number of ear-plug laminations and the number of ridges
on baleen plates of fin whales, Laws & Purves (1956), Nishiwaki (1957) and Laws
(1~61) examined, and Chittleborough (1959) also examined the relation between
ear plug and baleen on the humpback whale. They all recognized that two laminations corresponded to one ridge. However, for example, in Fig. 55 (p. 467) on thereport by Laws, there are individuals which are over the 45° line. If two laminations correspond to one ridge, all individuals must be plotted on or right side of the

72

S. OHSUMI

line. And in the Fig. 4 of the paper by Chittleborough (1959), also there aremany individuals of which number of ridges more than half of the number of earplug laminations. And from these figures, we can consider that there is possibility of the existence of individual of which one ridge on baleen plate correspondto less than two laminations.

8
2
0

6

0

0

Q_
c

§0

"'

~
0

0

..n
c
0

4

"'

Ol

~

0

"'E

-"

2

z
5

l0

15

20

25

30~

Number of ear-plug laminations

Fig. 9. Relation between number of ear-plug laminations and the number of ridges onbaleen plate for fin whales. Open circle: Antarctic, Closed circle : North Pacific, Solidline: One lamina correspond to one ridge, Broken line : Two laminae correspond to
one ridge.

Fig. 9 shows the relation between number of ear-plug laminations and baleenridges on 53 Antarctic and 21 North Pacific fin whales. In this figure, broken line
is base on hypothesis that two laminations correspond to one ridges, and solid line
is based on another hypothesis that one lamination corresponds to one baleen ridge.
As mentioned above, if former hypothesis is true, all individuals must be on thebroken line or right side of the line, because baleen plate become to wear at the
tip from relatively young ages (Ruud, 1950). However, there are many individuals
which are on the left side of the broken line. Then, we must abandon the former
hypothesis. On the contrary, almost of all points distribute on solid line or rightside of the line. I have scanty of data on the material less than 3 laminations, but thelatter hypothesis approaches to the truth more than the former hypothesis. That is
to say, there is possibility that one ear-plug lamination corresponds to one baleenridge in the first few ages. As reviewed in Introduction, nowaday, it seemes to berecognized that annual increment of baleen is equivalent to one ridge (Ruud, 1940,
1945; Nishiwaki, 1951 ; Chittleborough, 1959). If it is correct, one ear-pluglamination corresponds to one year. This conclusion agrees also with the resultsin former sections in the present paper. However, I must notice that there are
3 individuals which distribute on the left side of the solid line. Ichihara ( 1964)
confirms the prenatal formation of ear plug. But there is no report on the forma-

AGE DETERMINATION OF FIN WHALE

tion of ear plug chiefly in calf stage.
problem.

73

Furhter examinations are needed for thisEXAMINATION OF AGE COMPOSITION BASED ON EAR-PLUG
LAMINATIONSAGE COMPOSITIONS OF FIN WHALES CAUGHT IN NORTHOF EAST ALEUTIAN ISLANDS

By immunologic and marking approaches, Fujino (1960) reported that almost of
the fin whales caught in the north of east Aleutian Islands are composed withpure Population-II. And as Omura ( 1955) reported, the whaling in this area had
not been operated on a large scale before the time when Japanese fleets began tooperate in 1954.
TABLE 8. AGE COMPOSITION OF FEMALE FIN WHALES CAUGHT IN THE
NORTH OF EAST ALEUTIAN ISLANDS DURING 1959 TO 1961
Annual accumulation rate

Annual accumulation rate
Age
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

One lamination Two laminations

2
5
29
59
69
90
64
50
51
36
30
27
27
15
22
20
17
17
12
28
18
18
20
15

7
88
159
114
87
57
42
42
34
40
36
35
37
23
18
25
17
19
13
17
8
5
2
8
4

Age

One lamination

Two laminations

26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51<
Total

17
20
12
11
9
9
12
13
7
10

2
2
6
4
4
3
3
4

II

8
6
7
8
9
4
4
2
3
2
2
6
2
43
978

2

2
3
978

Table 8 and Fig. 10 show the estimated age compositions of female fin whalescaught in the north of east Aleutian Islands during 3 years from 1959 to 1961 basedon ear-plug laminations. In this figure, the age distributions are converted on both

74

S. OHSUMI

assumptions of biannual (two-laminations age; broken line) and annual (one-lamination age; solid line) accumulation rate of ear-plug laminations. Frequencies areshown in logarithm.
Modes of frequencies exist in 7 years in the case of one lamination age and in
3 years in the two-laminations age. This is because size limit is prescribed as 55
feet for northern hemisphere fin whale in the factory ship whaling, and younger
animals are protected from whaling.

100
80
60
40
~

<JJ
0
-"'

5

20

0

1'

~ I

;;;

I
I

_Q

E
~

z

10
8

I

~

x
I\

I

\

6

'1

I\

f

\ :

~

jl
JI

I J

I

\

t f \\

4

11

1J I

f~

JI

1

/ \

\ I

\I \ I: I

k-1

'f

/

v \xxf I1'I

2

x

iil/
l/

l/

v

*
5

10

15 - 20

25

30

xx x

35

40

x

45

50

55

60

65

70

Age !years I

Fig. 10. Age compositions based on ear-plug laminations of the female fin whales caught
in the north of east Aleutian Islands during the seasons from 1959 to 1961. Opencircles and solid line: Annual accumulation rate is assumed as one, Cross andbroken line : Annual accumulation rate is assumed as two.

Now, as shown in Fig. 10, catch curves are seemed to be separated to two straightlines excluding older age respectively in two accumulation rates. The cross pointof two straight lines is estimated to be 15 years for the case of one-lamination age
and 7 years for the case of two-laminations age.
If there is a population of which natural mortality coefficient (M) is constantand a constant fishing (coefficient is F) is operated to the population (more thanA-age individuals are catchable), the logarithmic catch curves must be changed by
years as shown in Fig. 11. Catch curves are separated to two straight lines. And
right line has the same coefficient as M. On the other hand, left line has a coeffici-

75

AGE DETERMINATION OF FIN WHALE

ent which is Z ( = M + F). Cross point of these two lines moves according to thefishing years, and after t years, the cross point must become to (A+t)-age.

·"

.i
0

OJ

.2

\

\

t\
A age

\

A+ I age\

i

\
5

\

25

20

15

10

Age (years)

Fig. 11. Modelal catch curves according to the change of years, when a constant fishingeffort (F) is given to a population of which natural mortarity (M) is constant and recruit
is constant.

vVhen this modelal catch curves are able to adapt the actual catch-curves, thefollowing factors must be chequed:
1) Natural mortality rate is constant: We cannot cheque on this factor.
But in the one-lamination age, mortality is seemed to be constant during theages from 15 to 40.
2) Recruitment to the age catchable is constant: We cannot know on thisfactor.
3) Fishing effort is constant: Table 9 shows the C.D.W. (catchers days
work) in the operation in the north of east Aleutian Islands from 1954 to
1961. During the 8 years, C.D.W. are not always constant, and they vary
between 110 and 350. But there is no tendency in the variation. And
average of C.D.W. is 286.8.
Although there are above weak points, the actual curve is seemed to be adapted
the modelal catch-curve.
On the cross point of two straight line, following result is obtained :A
One-lamination age
Two-laminations age

7
3

A+t

6
6

13
9

Actualcross point
15
7

76

S. OHSUMI

As actual catch-curve is given from sum of 3 seasons 1959-1961, this is considered
to be a catch curve in 1960. Therefore, t is 6 years. From above result, I cannot
determine which curve is more suitable to truth, but deviation between actual crosspoint is 13% in one lamination age, on the other hand, it is 29% in two laminations
TABLE 9. CATCH EFFORTS FOR FIN WHALES.IN THE NORTH OF
EAST ALEUTIAN ISLANDS (Areas P 25 BS AND P 26 BS)
AverageNo. of fin
YearCatchers*
Days work
C.D.W.
tonnagewhales caught

1954
1955
1956
1957
1958
1959
1960
1961

5
9
10
10
10
10
10
10

260
450
330
220
110
290
370
260

52
50
33
22
II

29
37
26

460.4
504.0
572.7
632.0
657.2
673.5
688.8
690.7

587
1177
773
408
299
705
948
585

* Including scouting boats
age. More accuarate result will be obtained in future on this subject by examining the tendency of change of age composition.
NATURAL AND FISHING MORTALITY RATE OBTAINED FROM AGE
COMPOSITION BASED ON EAR-PLUG LAMINATIONS

From Table 9, natural mortality coefficient (M) and total mortality coefficient (Z)are calculated on two cases of annual accumulation rate of ear-plug laminations asfollows:
Annual accumulation rateof ear-plug lamination
One (one-lamination age)
Two (two-laminations age)

z

M

0.192
(7-15)
0.336
(3-7)

0.067
(16-50)0.150(8-25)) : Range of age classes in the calculation

The values ofZ and Min the latter case are about twice of the former.
mortality coefficient (F) is calculated from Zand M values. That is,

Fishing

F=Z-M

So, F values are given as 0.125 and 0.186 respectively for above two cases.

Then

total mortality rate ( 1-S), unconditional natural mortality rate ( D =1-S))and exploitation rate ( E =~ (1- S)) are calculated as follows :Annual accumulation rate
One lamina
Two laminae

1-S

D

E

0.174
0.285

0.061
0.127

0.113
0.158

1: (

AGE DETERMINATION OF FIN WHALE

77

RELATION BETWEEN NATURAL MORTALITY RATE AND RECRUIT RATEIn the virgin stock, if natural mortality rate and pregnant rate in mature stage areconstant throughout life, recruit rate is calculated presumably by the mortality rate
and pregnant rate.
In the north of east North Pacific, the pregnant rate are obtained from matureand pregnant female whales caught as shown in Table 10.
Pregnant rates vary between 43.9% and 68.l %, and average rate during 8
years is 55.5%.
TABLE 10. PREGNANT RATE OF FIN WHALE CAUGHT IN THE NORTHOF EAST ALEUTIAN ISLANDS DURING 1954 TO 1961
Year

Mature females

Pregnant whales

Pregnant rate (%)

1954
1955
1956
1957
1958
1959
1960
1961
Total

224
395
269
140
64
204
337
160
1793

139
219
118
85
41
139
164
88
996

62.1
55.4
43.9
60.7
64.1
68.1
48. 7
55.0
55.5

Vv e consider that above pregnant rates do not show the true value, and I guess
the rate is higher than the true value, because lactating animals are protected fromcatch by International Whaling Regulation, and so, most of them are not included
into the figures in Table 10.
Now, recruit rate (R) are calculated in Table 11, when the first recruit number(number of whales born) is 1, sex ratio of females is 0.5, natural survival rate is S,
age at sexual maturity is m, and pregnant rate is P, as follows :R = P/2 (S

m

+S

m+l

oo

+ ...... + S )00

P • Sm ( 1- S
2
1-S

)

Then S is smaller than 1,
p. Sm
R = 2(1-S)

Age at sexual maturity (m) is considered to be 5 years in the case of two-laminations age and 10 years in the case of one-lamination age. And true pregnant rate
is not known, but I set the rate as 0.30, 0.40, 0.50, and 0.60. Then, the recruit
rates are calculated as shown in Table 11.
If survival rate does not vary throughout life, in the range in which R is smaller
than 1, the number of whales born become to be less than the previous number, andsuch a population cannot maintain the number of stock. Then, in general, theS. OHSUMI

78

mortality rate in calves is conciderable to be more than the adults, so, the R-value
calculated by above process must be fairly more than I in practice.
In one-lamination age, survival rate in which the stock continue the size are
more than 0.93 and 0.90 respectively in the cases of which pregnant rates are 0.30
and 0.60. On the contrary, in two laminations age, they are more than 0.9I and
0.86 respectively.
TABLE 11.

Age at sexual
maturitys.r.\p.r.
0.97
0.96
0.95
0.94
0.93
0.92
0.91
0.90
0.89
0.88
0.87
0.86
0.85

RECRUIT COEFFICIENT OF THE FINWHALE CHANGING THE
SURVIVAL RATES AND PREGNANT RATES

5 years old

10 years old
0.50

0.40

0.30

0.60

0.50

0.40

7.38
5.00
3.60
2.69
2.08
1.63
1.30

6.15
4.16
3.00
2.25
I. 73
I.36

4.92
3.33
2.40
1.80
1.39

3.69
2.50
1.80
1.35

1.09

0.82

1.08

0.86

1.04

0.87

8.60
6.13
4.65
3.67
2.98
2.51
2.08
1. 77
1.52
1.32
1.15

7 .17
5.11
3.88
3.06
2.48
2.09
1. 73
1.48
1.27

5.73
4.09
3.10
2.44
1.99
1.67
1.39
1.18

1.10

0.88

0.60

0.85
0. 70
0.53
0.47
0.39

1.04

0.30
4.30
3.06
2.33
1.83
1.49
1.25
1.04

0.89

1.02

0.96

1.01

0.88

s.r. : Survival rate, p.r. : Pregnant rate

Now, the natural mortality rates were shown in previous section that 0.06I(survival rate is 0.939) in the case of one lamination age. This value satisfy the Rvalue even if pregnant rate is 0.30, and when pregnant rate is more than 0.30, themortality rate is suitable for the continuance of the population size. On the other
hand, the natural mortality rate in the case of two-laminations age is 0.127 (survival
rate is 0.873). In this case R-value is lower than I when pregnant rate is lower
than 0.50. Even if the pregnant rate is 0.60, R-value is I. I. This value will be
not safe for the continuance of population size, considering the higher mortality ratein the young stage.
Therefore, when the annual accumulation rate of ear plug is assumed to be
two, the natural mortality rate calculated from age composition is too high for maintain the population size. On this point of view, the hypothesis of two-laminations
age should be abandoned.
Purves & Mountford (I959) calculated the mortality rate from the age distribution based on ear-plug lamination on the fin whales in the Antarctic area I.
And they got mortality coefficient. They are 0.133 in the female and 0.106 in the
male. The figures are based on an assumed rate of formation of 2 laminations per
year. Although Purves & Mountford did not consider the effect of whaling on
the age distribution, they seem to recognize the figures show the natural mortality

AGE DETERMINATION OF FIN WHALE

79

coefficient. The coefficient in the female is similar to my result in 2 laminationsage.
Laws ( 1961) calculated the mortality rate from the age distribution based on
number of corpora in the ovaries on the female fin whale in the Antarctic area IIin pre-war period when, as he estimated, fishing mortality was relatively small. The
mortality coefficient is 0.0973 corresponding to annual mortality rate of 9.2%.
In the calculation, the annual accumulation rate of corpora is assumed to be 1.43.
However, Doi (in press) calculates the natural mortality rate comparing the changeof number of fin whales catch per unit effort between the Antarctic pre-war andpost-war seasons independently to the age distribution. And he got the result thatthe natural mortality rate is 5-7%.
CALCULATION OF FISHING AND SURVIVAL RATEBY THE RECOVERY OF MARKED FIN WHALE

There are many undetermined factors for adaption of marking to population dynamics (Ricker, 1958). And I don't want to examine thoroughly the marking method
for population dynamics. In this section, I examine the marking result only forcheck the fishing rate and total survival rate calculated by the age composition basedon ear-plug laminations.
Table 12 shows the estimated number of fin whales marked in the north of east
Aleutian Islands and number of whales recaptured among them during 1954 to 1962
seasons. Number of whales recaptured are variable according to the number ofwhales caught. Then, the number of whales recaptured are reviced assuming that1000 whales are caught in every year. Number of whales marked (M) and recaptured (R) are so small that the average value is considered to be more suitable forthe exmaination.
Survival rate S is estimated by following formula (Ricker, 1958) :S=

Ri +R2+ ......Rn
Ro+R1 + ..... Rn-1

The number of recaptured whales in the same year of marking have many discussablefactors, so I consider the data of the recovery in the same season must be excluded
for this calculation, so the formula is reviced as following :S = R2+R 3 + ..... Rn
R 1+R 2+Rn- 1
The results are shown in Table 13. The calculated survival rate becomes
more correct by the increment of elapsed years. In the last 4 cases in the table,
survival rates are 79-86%.
The survial rate S calculated from age composition is 82.6% in the case of one
lamination age, and 71.5% in the case of two laminations age. Then one lamination
age corresponds to the result obtaned from marking experiments. And the survival
rate attained from age composition of two laminations age is considered to be too high.

80

S. OHSUMI

Fishing mortality rate is calculated briefly as follows :j - Ro-M

They are 5.1 % and 8.3 % respectively in actual and reviced. But whaling andmarking are operated almost parallelly in practice. So the twice of the calculated
TABLE 12. NUMBER OF FIN WHALES MARKED AND RECAPTURED IN THE
NORTH OF EAST ALEUTIAN ISLANDS DURING 1954 TO 1962
Actual figure.
No. ofwhalesYearmarked
A.

1954
1955
1956
1957
1958
1959
1960
1961
1962
Tota!
average
B.

210
33
57
41
28
15
II
23
6
424
47.1

Elapsed years from marking till recapture
0
7
2

2
7 (1)
1 (1)

3 ( 1)
I

4

7 (2)
I
2

2
6(3)
I
3

5
22(1)
2.44

2
20(4)
2.50

I
13(3)
1.86

3

4

3
6
2 (I)
I
14(1)
2.33

1 ( 1)
1
1
4(1)
0.80

5

7

6

5(2)
I
2
7 (2)
I. 75

2
0.67

2
1.00

8

Total

No. ofwhalescaught

7
9(1)
3(1)
10(4)
11 (2)16(2)11(1)
12( 1)
584(12)

585
1177
773
601
455
705
1066
587
284
6233

12.0
7.7
3.9
16. 7
24.2
22.7
10.3
20.4
17.6
135.5

1000
1000
1000
1000
1000
1000
1000
1000
1000
9000

Reviced figure when 1000 whales were caught in every year.

1954
1955
1956
1957
1958
1959
1960
1961
1962
Total
average

210
33
57
41
28
15
11
23
6
424
47.1

12.0
I. 7
5.0
2.2
5.7

6.0
1.3
15.4
1.4
1.9

2.6
10.0
2.2
4.3

8.5
35. l
3.91

7. l
33. l
4.14

3.5
22.6
3.23

I. 7
2.2
4.3
5.6
3.4
3.5
20.7
3.45

2.2
7. I
0.9
0.9
I. 7
I. 7
3.5
9.7
8.3
1.66 2.42

0.9
I. 7

3.4

2.6
0.87

3.4
I. 70

) ; Number of whales recaptured in other whaling areas or whales which were not known the position
recaptured.
TABLE 13.

TATOL SURVIVAL RATE OF MARKED FIN WHALES CALCULATED
1954-1957

1954-1962

Elapsed years (n)ActualRevicedActualReviced

2
3
4
5
6
7
Fishing mortality rate

0.800
0.852
0.684
0.805

0.841
0.794
0.678
0.785

0.062

0.102

0.744
0.961
0. 757
0.912
0.811
0.857
0.111

0.780
0.906
0. 771
0.862
0.781
0.845
0.194

AGE DETERMINATION OF FIN WHALE

81

f will become near the truth.

Then, they are 10.2% and 16.6% respectively. As
the data concerning recoveries in the same year of marking have many discussive
factors, the following formula (Ricker, 1958) are suitable for this purpose:f =R 1 +R2+ ...... +RnSM(l+S+ ...... Sn-2)

The results calculated from above formula is :sfD

1954-1957
Reviced
0.785
0.102
0.113

Actual
0.805
0.062
0.133

1954-1962__._
ActualReviced
0.845
0.857
0.111
0.194
0.032
-0.029Fishing mortality rates are situated between 0.062 and 0.194. The calculated
fishing mortality rates from age compositions are 0.113 and 0.158 respectively in
one lamination age and two laminations age. The former rate corresponds to reviced result of 1954-1957 and actual result of 1954-1962. And the latter is near
the result of reviced data 1954-1962. However, in the latter case the natural
mortality rate obtained from marking experiment is smaller than 0 (-0.029). Thiscannot explain the actual phenomena, because the natural mortality rate should
be more than 0. Therefore the fishing mortality rate of 0.194 is higher than theactual states of the whaling. Then, the one-lamination age agrees more with examination of fishing mortality rate from marking than the two laminations age.
CHANGE OF MATURITY RATE ACCOMPANIED WITH WHALING

Sexual maturity rate changes accompaniing with the increasement of whaling years.
Table 14 and Fig. 12 show the change of maturity rate of female fin whales caught
in the north of east Aleutian Islands from the begining of whaling in 1954 to 1961.
The rate decrease by the increasement of years.
Now, taking following two model-age-compositions, and the change of sexual
maturity rate are calculated from the begining of whaling in Table 15.

Natural mortality rate
Fishing mortality rate
No. of whales in 0 year classAge at sexual maturity
Age at recruitment for whaling
No. of whale caught before racruitment

Model I(One lamination age)
0.061
0.113
10,000107No. of whales in age 7 X 2Model II
(Two laminations age)
0.127
0.158
10,0005
3No. of whales in age 3 X 1

In Model I, number of mature females at the begining of whaling is 87,363.
If a quater of the mature females is the number of female whales which are born,the number is 21,841. Whereas the first assumption of females which are born is
10,000. From this calculation we can recognize that the natural mortality rate inyoung stage is fairly large. By the way, in Model I, whaling does not influence toS. OHSUMI82

the recruitment at least until 7th years after the beginin of whaling. In practice,there are whales caught before the age at recruitment for whaling, as shown Table
15, so, I assumed the whales as the twice of the number of whales at the age ofrecruitment (12,873). In Fig. 12, the change of maturity rate of Model I is similar
to the actual change of the maturity rate.
TABLE 14. ACTUAL NUMBER OF SEXUALLY MATURE AND IMMATURE
FEMALE FIN WHLES CAUGHT IN THE NOTH OF EAST ALEUTIANISLANDS DURING THE SEASONS FROM 1954 TO 1961.
Year

Immature

MatureMature rate (%)

1954
1955
1956
1957
1958
1959
1960
1961
Total

80
166
103
70
77
153
223
135
1007

224
395
269
140
64
204
337
160
1793

73.7
70.4
72.3
66.7
45.4
57 .1
60.2
54.2
64.0

TABLE 15.

CALCULATED NUMBER OF TOTAL AND MATURE FEMALESCAUGHT IN THE CASES OF MODELS-I AND -II.

Model-I: D=0.061, E=0.113 (One-lamination age).
Total
Year
lst
2nd
3rd
4th
5th
6th
7th
8th

118391.2
106468.896621.988483.7
81765.2
76287.771589.867842.9

MatureMature rate (%)

87362.6
76849.9
67601.859465.6
52747.1
47269.6
42611. 738824.8

73.8
72.2
70.0
67.2
64.5
62.0
59.5
57.2

Model-II: D=0.127, E=0.158 (Two-laminations age).
Year

Total

MatureMature rate (%)

lst
2nd
3rd
4th
5th
6th
7th
8th

59041.4
50764.844846.8<40614.8<37589.3<35425.8<33879.4<32773.1

39926.6
32701.1
26782.7
22551.0
19525.5<17362.0<15815.6<14709.3

67.6
64.4
59.7
>55.5
>51.9
>49.0
>46.7
>44.9

However, in model II, even in the virgin stock, the number of whales born islower than the firstly assumed number of whales born which can maintain the
population size. Then the whaling will influence to the number of recruitment for
whaling after 3 years.
Assuming the number of whales caught before the age of recruitment to be as

AGE DETERMINATION OF FIN WHALE

83

the same as number of whales at the age of recruitment, the maturity rates are lower
than the actual figures.
After 3 years from the start of whaling, the number of recruit becomes to besmaller than the virgin stock. Then, as the number of immature whales become relatively smaller, the maturity rate must be higher than the calculated rate.
In Fig. 12, the estimated changes of maturity rate are shown. This estimated change
in Model II does not correspond the feature of the actual data.

"'Q)
0

E

70

Q)

Q)

::J

0

E

60

0

c
Q)

u

© 50

0..

'54

'56

'58

'60

Year

Fig. 12. Change of sexual maturity rate of the female fin whales for actual and twomodels. Open circle and straight line: Actual data from the female fin whales caught
in the north of east Aleutian Islands, Closed circle and solid line : Model I, Cross andbroken line: Model II.

In conclusion, the actual change of maturity rate correspond fairly with ModelI (the accumulation rate is one annually), but those of which Model II is not consistent with the actual change.
DISCUSSION

By some examinations which were described above, I conclude that the annual
ear-plug accumulation rate must be under two which is nowaday recognized by us,
and I showed some examples for estimation that the annual accumulation rate may
be near one.
Indeed, ear plug is the best of age characters in the fin whale, but there are many
points which must be investigated further. One of them is a standardization of lamination count. As Ichihara (1963) reported, there is individual discrepancy in lami-

84

S. OHSUMI

nation count. And the photometric method which lchihara (1963) manufactured
for trial must be developed further for this purpose. When standardization of ear
plug reading is estabished, and if the new reading becomes different to the present
reading, the above examinations should be re-examineed. The second point to
be investigated in future is the periodicity of laminae formation. Purves (1955)
considered the migratory period as the relation of laminae formation. However,
Clarke (1962) reported the feeding of fin whales off the coast of Chile in October andNovember. And according to Mackintosh (1942) and Nemoto (1962), food of whales
are scanty in the lower latitude, and the baleen whales do not feed so much in winterseason. If the mechanism of formation of ear-plug lamination is coincided to thenutrition, the formation of ear-plug lamination must have more relation with the winter(reproductive season) or summer (feeding season) than the migratory seasons. Ridges of baleen plates are also considered to have relation with nutrition (Ruud, 1940,1945). If so, the periodicity of formation of ear-plug lamination and ridges of baleen
plates should be the same each other. My result of correlation between baleen ridges
and ear-plug lamination briefly support on the same mechnaism of formation between two characters. On the lamination formation, Purves & Mountford (1959)
and lchihara (1959) discribed on possiblity as shown in Introduction. Furthermore, Mr. lchihara suggests me the possibility of the change of periodicity of earplug lamination by the age. We must investigate the formation mechanism of earplug lamination. Then the factors conserning the formation of laminae will beknown, and it will be solved the annual rate and whether the periodicity of formation are variable or constant.
My second conclusion is on the annual ovulation rate of the fin whale. The
rate must be less than 1.4 which as Laws (1961) studied throughly. I got a resultthat it may be near 0.5 although there are individual variations and the difference
among the different stocks as shown by Nishiwaki, lchihara & Ohsumi ( 1958)
and Fujino (1963), and Kimura (1956) reported the tendency of multiple ovulationsin the course of increase of age by ths study of twinning.
The annual ovulation rate is very important not only for the age determination
but also for the reproductive physiology of the whales. According to my result,the fin whale ovulates in average one every two years. Then pregnancy rate
may be under 50%, because there are evidence that some corpora albicantia are
non-pregnant (Laws, 1961). Apparent pregnancy rate is 55% in my material,
but I consider that they are higher than the true rate. Although Laws (1961)
considered that over 80 % of females wean their calves before they enter the
pelagic whaling grounds, Chittleborough (1958) reported that the weaning periodof humpback whales is 10 months. And there are other observations on the suckling of dolphins. According to Tavolga & Essapian (1957) and Nakajima et al.
(1962), bottlenose dolphin (Tursiops sp.) suckles for over 1 year in aquarium. Although we have no data on direct observation of weaning period in the fin whale
and above data are given by other species, I think the lactating stage of the fin whale
will be longer than previous descriptions (Mackintosh & Wheeler, 1929; Laws,
1961). Mackintosh & Wheeler (1929) suggestthatforthenursing period the lactat-

AGE DETERMINATION OF FIN WHALE

85

ing females are segregated from the main herds, so that all lactating females do notappear on the whaling grounds. And in the whaling grounds, the taking of calvesor females accompanied with calves are prohibited by the International Whaling
Convention. Therefore, the pregant rate calculated by actual data are considered
to be higher than the true rate.
Concerning this subject, Laurie (a letter to Purves & Mountford, 1959) also
discussed and he wrote, if so, annual increment of corpora in the blue whale must
be lower than 1.13 and connected as 0.69. Further ecological knowledges are needon this problem. I think that the two-years breeding cycle will be common in thefin whale, but there will be some individuals whose breeding cycle is more than two
years.
In the examination on the relation between ear-plug laminations and baleen
plate ridges, there are some material which are not able to explain by the correspondence one to one. The number of ridges is more than the number of ear-plug lamination. As one of the caution, the discount of ear-plug lamination or baleen ridges
is considerable, but more collection and comparison are needed on this subject especially on the calves.
SUMMARY

1. Age determination of the fin whale (Balaenoptera physalus L.) was examinedby some methods.
2. Considering the elapsed time from marking, the annual accumulation rateof ear-plug lamination of marked whales recaptured should be less than two, andthere is no whale of which number of ear-plug lamination devided by elapsed years
is less than one.
3. Sexually immature rate of recaptured whales decrease with the increasementof elapsed years. And from the tendency of the decrease of immature rate, the age
at sexual maturity is estimated to be about 10 years.
4. Numbers of corpora lutea and albicantia in the ovaries of recaptured fin
whales devided by elapsed years are able to be explained more easily in the assumed
case which the annual ovulation rate is 0.5, and age at sexual maturity is 10 years.
5. Relation between the ear-plug lamination and mean number of corpora
shows that annual accumulation rate of corpora is 0.49 in the fin whales caught in
the Antarctic areas IV and V, if one lamination accumulates in a year.
6. Percentage of sexual maturity in successive the number of ear-plug lamination shows that the number of ear-plug lamination corresponding to 50% of sexual
maturity is 9-.4 in males and 10. 7 in females.
7. Before the tip of baleen plates begin to wear, number of ear-plug lamination coincide the number of ridges on baleen plates.
8. Age compositions of the female fin whales caught in the north of east
Aleutian Islands based on ear-plug lamination are drawn in following two cases.
And the natural mortality rate (D) fishing mortality rates (E) and total mortality rate(Z) are calculated as follows:S. OHSUMI86
Annual rate
One lamination
Two laminations

z
0.174
0.285

D
0.061
0.127

E
0.113
0.158

9. In the virgin stock, relation between natural mortality rate and recruit
rate is discussed. And natural mortality rate in the case of two laminations age isconsidered to be too high for maintainance of the stock size.
10. Examining the number of fin whales marking and recovery in the northof east Aleutian Islands, survival rate is calculated to be 79""'86 %· And the fishingmortality rate is also calculated from the data. It is 10-12%.
11. Yearly change of sexual maturity among the actual, Models I and II
populations are compared. And the change of Model I (annual rate is one lamination) is suitable to the actual change. On the contrary, Model II (annual rate is
two laminations) is not able to explain the actual change.
12. Thinking collectively above examinations, it will be concluded that theannual accumulation rate of ear-plug lamination must be less than two, probably
near one, and average annual ovulation rate will be under one, probably near 0.5,
although there are individual and racial .variations. In addition, the average age
at sexual maturity will be older than 5 years, probably 9""' 11 years. Of course there
are individual variation in the age of sexual maturity.
13. The standardization of the reading of ear-plug lamination should beestablished, and after then above examinations must be re-examined.
ACKNOWLEDGEMENT

Marking material used in this paper are based on the endeavers by Discovery Committee and National Institute of Oceanography which have been engaged to the whale
marking in the Antarctic from 1932, International Whales Marking Program in
the Antarctic from 1954 and the Fisheries Agency of Japanese Government whichhave marked into the whales in the North Pacific since 1949. Unless the endeavers
by above Agencies, present examinations would not be studied. I am indepted toabove Agencies for use the material. I would like to thank Mr. S. G. Brown who
kindly checked the marking data in the Antarctic.
And this paper could not be written unless the strenuous efforts of the biologists
who investigated, coll~cted and examined the material under the leading by Dr.
Omura, Director of the Whales Research Institute. In particular, Dr. M. Nishiwaki, Dr. K. Fujino, Dr. T. Nemoto, Mr. T. Ichihara and Mr. K. Nasu of the
Whales Research Institute. I due especially to Mr. T. Ichihara and Dr. M.
Nishiwaki, on the reading of ear-plug laminations. I wish to thank them.
My sincere thanks are due to Dr. H. Omura and Dr. M. Nishiwaki of the\!\Thales Research Institute and Dr. T. Hibiya, Assistant Professor of the Universityof Tokyo for their guidance throughout the work.
Dr. F. Nagasaki of the Fisheries Agency of Japan and Dr. N. Doi of Tokai
Resional Fisheries Research Laboratory kindly suggested me the method for analyzing
the population dynamics. Dr. R. M. Laws of the former staff of National InstituteAGE DETERMINATION OF FIN WHALE

87

of Oceanography kindly corrected some parts of my draft and gave me suitable
cnt1c1sm. I have benefited from discussions with Mr. T. lchihara. I should liketo thank them.
Finally, I am much indebted to many members of the Japanese whaling companies for the help to investigation and collection of the materials.

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33: 1-54.
- - (1962 b). Whale marks recovered during Antarctic seasons 1960/61, 1961/62 and in South Africa
1962.
Norsk Hvalfangst-Tid., 51 (11): 429-34.
Chittleborough R. G. (1958). The breeding cycle of the female humpback whale, Megaptera nodosa (Bonnaterre). Aust.]. Mar. Freshw. Res., 9 (1): 1-18.
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Chittleborough, R. G. & Godfrey, K. (1957). Review of whale marking and some trials ofa modified whalemarks. Norsk Hvaifangst-Tid., 46 (5): 485-508.
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towards and beyond the Garapagos Islands in 1959. Norsk Hvalfangst-Tid., 51 (7): 265-87.
Clarke, R. & Brown, S. G. (1957). International co-operation in Antarctic whale marking from 1945 to
1957. Norsk Hvaifangst-Tid., 46 (9): 513-7.
Dawbin, W. H. (1959a). Evidence on growth-rates obtained from two marked humpback whales. Nature
183: 1749-50.
- - (1959 b). New Zealand and South Pacific whale marking and recoveries to the end of 1958. Norsk
Hvaifangst-Tid., 48 (5): 213-38.
Doi, T. (1964). Estimation of coefficient of natural mortality rate of fin whale population in the Antarctic.·
Bull. Takai Reg. Fish. Res. Lab., 38 (In press)
Fujino, K. (1960). Immunogenetic and marking approaches to identifying subpopulations of the North
Pacific whales. Sci. Rep. Whales Res. Inst., no. 15 : 85-142.
- - (1963). Population genetics of whales with reference to blood types. Bull. Jap. Soc. Sci. Fish. 29(12): 1133-8
Hylen, A.,Jonsgard, A., Pike, G. C. & Ruud, J. T. (1955). A preliminary report on the age composition of
Antarctic fin whale catch 1945/46 to 1952153 and some reflections on total mortality rates of fin whales.
Norsk Hvaifangst-Tid., 44 (10): 577-89.
Ichihara, T. (1959). Formation mechanism of ear plug in baleen whales in relation to glove-finger.
Sci.
Rep. Whales Res. Inst., no. 14: 107-135.
- - (1963). Photometric method for counting laminae in ear plug of baleen whale. Sci. Rep. Whales Res.
Inst., no 17 : 37-48.
- - (1964). Prenatal developement in ear plug of baleen whale. Sci. Rep. Whales Res. Inst., no. 18: 29-48
Kimura, S. (1957). The twinning in southern fin whales. Sci. Rep. Whales Res. Inst., no. 12: 103-25.
Laurie, A. H. (1937). The age of female blue whales and the effect of whaling on the stock. Discovery
Repts. 15 : 223-84.
- - (1959). See Purves & Mountford (1959).
Laws, R. M. (1960). Problems of whale conservation. Trans. N. Amer. Wildlife Conf. 25: 304-19.
- - (1961). Reproduction, growth and age of southern fin whales. Discovery Repts. 31: 327--486.
Laws, R. M. & Purves, P. E. (1956). The ear plug of the Mysticeti as an indication of age with specialreference to the North Atlantic fin whale. Norsk Hva{fangst-Tid., 45 (8): 413-25.

88

S. OHSUMI

Mackintosh, N. A. (1942). The southern stocks of whalebone whales. Discovery Repts. 22: 197-300.
Mackintosh, N. A. & Wheeler, J. F. G. (1929). Southern blue and fin whales. Discovery Repts. 1:
257-540.
Nakajima, M., Takahashi, K., Ogura, M. & Sawaura, K. (1963). On the growth of infants of the small size
toothed whales. ]. Jap. :{,oo and Aquarium. 5 (1): 16-22 (In Japanese)
Nemoto, T. (1962). (Food of baleen whales) Geiken Sosk_yo no. 4: 136 pp. (In Japanese)
Nishiwaki, M. (1950a). Determination of the age of Antarctic blue and fin whales by the colour changes incrystalline lens. Sci. Rep. Whales Res. Irist., no. 4: 115-61.
- - (1950 b). Age characteristics in baleen plates. Sci. Rep. Whales Res. Inst. no. 4: 162-83.
- - (1951). On the periodic mark on the baleen plates as the sign of annual growth. Sci. Rep. Whales
Res. Inst., no. 6: 133-52.
- - (1952). On the age-determination of Mystacoceti, chiefly blue and fin whales. Sci. Rep. Whales
Res. Inst., no. 7: 87-119.
- - (1957). Age characteristics of ear plugs of whales. Sci. Rep. Whales Res. Inst., no. 12: 23-32.
Nishiwaki, M. & Yagi, T. (1953). On the age and the growth of teeth in a dolphin (Prodelphinus caernleoalbus) (1). Sci. Rep. Whales Res. Inst., no. 8: 133-46.
Nishiwaki, M., Ichihara, T. & Ohsumi, S. (1958). Age studies of fin whales based on ear plug. Sci. Rep.
Whales Res. Inst., no. 13: 155-69.
Ohsumi, S. (1962). Biological material obtained by Japanese expedition from marked fin whales. Korsk
Hvalfangst-Tid., 51 (5): 192-8.
Ohsumi, S., Nishiwaki, M. & Hibiya, T. (1958). Growth of fin whales in the northern Pacific. Sci. Rep.
Whales Res. Inst., no. 13: 97-133.
Ohsumi, S., Kasuya, T. & Nishiwaki, M. (1963). The accumulation rate of dentinal growth layers in the
maxillary tooth of the sperm whale. Sci. Rep. Whales Res. Inst., no. 17 : 15-35.
Omura, H. (1955). Whales in the northern part of the North Pacific. Norsk Hvalfantst-Tid., 44 (6): 323-45,
44 (7) : 395-405.
Omura, H. & Kawakami, T. (1956). Japanese whale marking in the North Pacific. Norsk Hvalfangst-Tid.,
45 ( 10) : 555-63.
Peters, N. (1939). -Ober Grosse, Wachstum und Alter des Blauwales (Balaenoptera musculus (L)) und Finnwales (Balaenoptera physalus (L)). :{,ool. Anz. 127: 193-204.
Purves, P. E. (1955). The wax plug in the external auditory meatus of the Mysticeti. Discovery Repts. 27:
293-302.
Purves, P. E. & Mountford, M D. (1959). Ear plug laminations in relation to the age composition of a
population of fin whales (Balaenoptera physalus). Bull. British Mus. (H.N.). :{,ool. 5 (6): 6-161.
Rayner, G. W. (1940). Whale marking. Progress and results to December 1939. Discovery Repts. 19:
245-84.
Ricker, W. E. (1958). Handbook of computations for biological statistics of fish populations. Bull. Fish.
Res. Board Canada no. 119: 300 pp.
Ruud,]. T. (1940). The surface structure of the baleen plates as a possible clue to age in whales. Hvalradets
Skrifter nr. 23: 24 pp.
- - (1945). Further studies on the structure of baleen plates and their application to age determination.
Hvalradets Skrifter nr. 29: 69 pp.
Ruud, J. T., Clarke, R. & Jonsgard, A. (1953). Whale marking trials at Steishamn, Norway. Norsk
Hvalfangst-Tid., 42 (8): 429-41.
Sergeant, D. E. (1959). Age determination in Odontocete whales from dentinal growth layers. Norsk
Hvalfangst-Tid., 48 (6): 273-88.
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Bull. Fish. Res. Board Canada no. 132 : 84 pp.
Tavolga, M. C. & Essapian F. S. (1957). The behavior of the bottle-nosed dolphin (Tursiops truncatus):
Mating, pregnancy, parturition and mother infant behavior. :{,oologica 42 (1): 11-31.
Tomilin, A. G. (1945). (The age of whales as determined from their baleen apparatus). C.R. Acad. Sci. Dok!.
Acad. Nauk .. SSSR. 49 (6) : 460-3.
Wheeler, J. F. G. (1930). The age of fin whales at physical maturity. Discovery Repts. 2: 403-34.

SCHOOL OF BALEEN WHALES IN THE
FEEDING AREAS
TAKAHISA NEMOTO
From the ecological point of view, the school of the baleen whale is one of the mostimportant theme although it has not been fully studied. The observations on theschool of whales from the aircraft, ships and the marking cruise have been carriedout (Chittleborough, 1953: Clarke & Ruud, 1954: Brown, 1957: 1958: Nemoto,
1959: Clarke, 1962), however, these are descriptions on the constituent numberof whales in schools in general.
Andrews (1914), Slijper, (1958) and Nemoto, (1959) discuss the schools ofbaleen whales considering the socionomic sex ratio, the affection, number ofwhales and the mutual help among whales in a school. Some studies and discussions on the ecological segregations in the migrations of certain baleen whales also
have been done, (Mackintosh, 1942: Fujino, 1960: Laws, 1961: Nemoto, 1959:
1962b), but it may be generally accepted that there has been few ecologicalstudy on the school of baleen whales.
The catch data and the whale marking results of the whales in the North Pacificand the Antarctic waters give biologists many materials, and I examine here themchiefly in the feeding grounds. The number of baleen whales in a school andthe sex ratio are checked in a first step. Sexual maturity in each member of a schoolis also important for this study, however, it is impossible to examine the whales
observed in the marking cruise in the sea. The most reliable data on the sexual
conditions of the baleen whales are obtained through the investigations carried out inthe factory ships, in the whaling stations, in the North Pacific and in the Antarctic.
It should be noted that the most part of the sexual conditions are obtained in the feeding areas, not in the breeding areas in the lower latitudes. I would think theschools of baleen whales should be examined also in the breeding areas, in which
the meaning of the school of baleen whales is somewhat different from that ofschools in the feeding areas.
The whaling has been opressing whales and have the great influence on theconditions of baleen whales such as migrations, reproductions and formations ofschools. Especially the whaling in the feeding grounds break up the schools by
the catch, and this affects the data treated here too.
Several populations are considered both in the Antarctic and in the North Pacific,
and individual numbers of baleen whales effect the schooling of them. But materials
are treated here as a whole in each whaling areas, Antarctic, North Pacific, andadjacent waters to Japan. Futher consideration will be made in due course on
these points.
The term ' school' of baleen whales is also said in other ways, pod, herd andgroup. 'School' and 'herd' are commonly used in the biology of whales, andI use here the word ' school' for the baleen whales. According to Clarke, (1956)
89

T. NEMOTO

90

the old whalernen distinguished ' pods ' or 'garns ' numbering up to about twenty
whales, 'schools' or 'shoals' of some twenty to fifty, and the 'herd' or 'body ofwhales ' comprizing some fifty to serveral hundred. The term ' herd ' is usedmostly for the land mammals ungulates, ' school ' for fish, and group ' is used
for the general expression in the recent ecology.
MATERIALS

The materials. treated here consist of two parts. One is the marking data in the
North Pacific, adjacint waters to Japan and the Antarctic ocean. The anotheris the catch data in the North Pacific by the Japanese factory ships in 1955 and 1956.
The marking data base on three groups described following.
North PacificAdjacent waters to Japan andBonin Islands
Antarctic
l:fj'

t,.j'

1953 ............ 1961
1949 ............ 1955
1954............ 1961
l2J'

120'

iCJ'

12J'

--~''

Fig. 1. The whaling grounds where the observations on the schools of baleen whales
have been carried out. Lateral line--North Pacific pelagic : Straight line-Coast ofJapan: Black circle--Okinawa, Black square-Bonin Island pelagic: Obliqueline-Antarctic pelagic.

From the marking data, the number of whales in a school is discussed
as well as the formations of the school of different species of baleen whales. The

91

SCHOOL OF BALEEN WHALES

socionomic sex-ratio and sexual conditions are mostly obtained from the biological
data based on the whales caught in the North Pacific. The pair schools of cow andcalf have been obtained through the marking research, and the variation in the number of baleen whales in a school from the marking and catch results both in the North
Pacific and the Antarctic. These research areas are shown in Fig. 1.
SCHOOL OF BALEEN WHALES IN THE NORTH PACIFIC,FIN WHALES (BALAENOPTERA PHYSARUS)
Number of fin whales in a school
The number of fin whales in a school has been discussed by Clarke & Ruud ( 1954)
Nemoto (1959) and Clarke (1962). According to their reports and other descrip
tions (Chitterborough, 1953 etc), fin whales have been. mostly found four or lessin a school in the feeding areas. The schools consist of five or more whales are
TABLE 1.

June
July
Aug.
Sept.
Total

62
178
64
305

NUMBER OF FIN WHALES IN A SCHOOLIN THE NORTH PACIFIC IN 1956
Number of fin whales in a school

2

3

4

5

6

7

8

88
204
151
2
445

32
100
52

17
72
28

8
32
9

3
9
7

2
5
3

10
3

18
13

184

117

49

19

10

13

31

May
Male Female
3
5
1955
1956

TABLE 2. SEASONAL OCCURRENCES OF SINGLE
FIN WHALES IN THE NORTHERN PACIFIC
Aug.
Sept.
July
June
Male Female
Male Female
Male Female
Male Fema,le
103
33
9
81
38
41
45
13
100
36
78
28
36
26
1

---------- -----------

9

10-

Total
Male Female
173
198
173
132

TABLE 3. OCCURRENCES OF IMMATURE FIN WHALESIN THE SINGLE SWIMMING FIN WHALE
MatureImm.
MatureImm.
Preg .
..---"'-..
. 164
34
45
71(55.5%)
128
1955
110
22
141
32
62(43.9%)
1956

comparatively scarce. The number of fin whales in a school in the North Pacificin 1956 is shown in Table 1 on 1298 fin whales. The number of fin whales in aschool vary with the proceeding of the seasons, an:d the single swimming fin whale
decreases in number in the late of summer (Nemoto, 1959).
This tendency is clearly shown in the Table 1 and Fig. 2. The one of themain reasons for the fact may be the leaving of the single swimming pregnant
female to the breeding area as it has been considered (Mackintosh, 1942 : N emoto,
1959: Laws, 1961), however, July in the North Pacific must be the feeding season
for fin whales and they come to the feeding areas in July successively. The forma-

~I

92

T. NEMOTO

tion oft he school in the feeding areas also should be considered as suggestedby the prevous report (Nemoto, 1959).
Single swimming fin whale
From the observations in the catcher boats chasing fin whales are used for the examination. The seasonal occurrences of male and female in single swimming
fin whales is given in Table 2 and 3 according to the data in 1955 and 1956. Thereis no consistent tendency in the occurrence of each sex, and no clear tendency inthe occurrences of immature and pregnant whales too. It has been generally ac100

JOO

50

50

<ll

g

~
=>
u
u

0

2

I~

l~

May

June

June

July

Aug.

Juiy

Aug.

Fig. 2. Seasonal variations of the number of fin whales in a school in the North Pacific.
Left-1954: Right--1956.

cepted that there are some ecological segregations in the baleen whales according
to the sex and sexual conditions. But there is no pecurial feture in the characters of
the fin whales in the data in 1955 and 1956. The pregnant ratio is also not so highor low comparing with other fin whales caught. Five lactating fin whales arepresent out of fifteen resting whales in 1955. The occurrence of the immature fin
whale are also not so different from the total catch of the fin whale. This may
partly be affected by the size regulation in the whaling. The shorter young fin
whales may sometimes form a large school but they are saved from the catch. As
a conclusion, single swimming fin whales in the feeding areas show no pecurialfeature. But it will be re-examined by the futher accumulated data in due cource.
Pair fin whales
The catch data of the pair fin whales are not so large in number. Twenty-six
pairs of fin whales in 1955 and sixty pairs in 1956 are caught by whaling, the occurrences of each sex of which are illustrated in Table 4. The combination of maleand female is dominant among three combinations. Male and male combinations
exceeds female and female combinaions. This may due to one reason of theaffection between male and female form the school. The sexual conditions of

93

SCHOOL OF BALEEN WHALES

those pair fin whales are as follows. Although the number of cases is not so large,
the immature combination of male and female is scarce. In the pair of female fin
whales, the occurrences of the combinations of mature and immature females andimmature combination are observed. Among the pregnant females in the pair of
two female fin whales, there are two cases of the two female fin whales pregnant outof seven. Among the mature male and female pairs, four male and female combinations are pregnant out of nine in 1955. Twelve pairs out of twenty-five
have the pregnant female and others are resting in 1956. From the above facts, it
is considered that all these pairs of mature male and female fin whales are not theTABLE 4.

1955
1956
TABLE 5.

Both Mature
Female Imm.
Male Imm.
One Imm.
Both Imm.

SEXUAL COMBINATIONS OF TWO FIN WHALESIN A SCHOOL IN THE NORTH PACIFIC (%)

Female & Female4(15.4)11(18.4)

Female & Male16(61.5)33(55.0)

Male & Male6(23.1)16(26.6)

Total
26
60

SEXUAL MATURITY IN TWO FIN WHALES IN A SCHOOLIN THE NORTHERN PACIFIC IN 1955 AND 1956
F. & F. F. & M. M.&M.
F.* & F. F. & M*. M.&M.
9
3
2
3

4

6

2

2
3

2

25
5
2

12

3

* M-Males, F-Females.
TABLE 6. OCCURRENCES OF MALE AND FEMALE FIN WHALESIN ONE FIN WHALE CAUGHT FROM A SCHOOL OFTWO FIN WHALES IN THE NORTH PACIFIC
FemaleMale
Mature Imm. Total
Mature Imm. Total
95(57) 37
132
119
21
1955
140
127 (56) 43
181
170
34
215
1956
Numbers in blacket are pregnant females.

school from the breeding areas. Some of them may be formed in the feedingareas bacause these resting fem ales are sometimes considered not to migrate to
the breeding areas.
Three of female fin whales pairs are not pregnant, and other two cases havepregnant females in the pairs. Three cases of mature and immature fin whales
out of five, the adult female fin whales are pregnant.
It seems that the more common pairs of fin whales in the feeding areas iscomposed of different sex fin whales, namely the pair of male and female. The
tendency is comfirmed by the catch of one fin whale from the pair of two fin whale's
school. The number of fin whales caught as only one whale catch from the pairof two fin whale's school are shown in Table 6. The sex ratio is high in male bothin 1955 and 1956. Generally speaking, the females are larger than males in Ba-

T. NEMOTO

94

laenoptera whales, the selection may choose females better. But the contraly tothis, the male is dominant. If the ratio of male and female fin whales is the sameas it is seen in the former example in the pair of two fin whales, the probability of
male from the pair fin whales is 0.539 in 1955 and 0.542 in 1956. The sex ratio ofmale is 0.515 in 1955 and 0.558 in 1956 which fairely coincide with the calculations.
These combinaions of the pair fin whales may be consistent both in two years in 1955
and 1956. The occurrences of immature fin whales do not differ from those of thecatch of two fin whales in pair, however, the slight high maturity ratio is observed
comparing with the single swimming fin whales., The pregnant ratios are 0.60
in 1955 and 0.44 in 1956 respectively which show no pecurial tendency.
Three fin whales in a school
The observation and chasing for three fin whales school are far less than the single
and pair fin whales. There have been five cases in 1955 and only one in 1956. As
shown in Table 7, one school is composed of all males, and three cases of two males
and one female and one case of one male and two females. The three males in themale trio are sexually mature, however, one of which is just mature. Perhaps it is
not the potencial male and it may not play the active sexual behaviour considering
the weight of the testis, 2.5 and 3.0 kg, (N emoto, 1962).
TABLE 7.

SEXUAL COMBINATION IN A SCHOOL OF THREE FIN WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Sexual combination
3 males

2 males & 1 female

3

1955
1956

male & 2 females
2

TABLE 8. SEXUAL OCCURRENCES IN THE CATCH OF TWO FIN WHALESFROM THE SCHOOL OF THREE FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956
Sexual combination

1955
1956

Male & Male
7
14

Male & Female
17

15

Female & Female
75

One mature male and one mature but resting female and immature female makethe school in one case, and one immature male, pregnant female and resting female
make the another school of one male and two females. There are three cases of two
males and one female. The mature males and one immature female are found in
two cases, two mature males and a mature pregnant female are found in anothercase.
It is very difficult to get general tendencies about the school of three fin whales,
however, it is interesting to note that two males and one female combinations occupy
the first rank. The period of pregnancy is about a year in fin whales (Ohsumi, Nishiwaki & Hibiya, 1957: Laws, 1961), and the nursing may be about seven months.
The number of males is dominant owing to above reason in schools as usually the
cow and calf pair do not allow the joining of other male whales in the feeding areas.

SCHOOL OF BALEEN WHALES

95

There are rather many examples of the catch of two whales from the school of three
fin whales. The occurrences of each sex are given in Table 8. The combinationof male and female is dominant through the catch in 1955 and 1956, and two males'
pair stands as the second. Especially fourteen pairs of males are caught out ofthirty-four examples in 1956. As compared with the occurrences of three males
school in 1956, it is the same tendency in the catch of the two fin whales from theschools of three fin whales. In 1955, seventeen pairs of male and female are caught
TABLE 9. SEXUAL CONDITIONS IN THE CATCH OF TWO FIN WHALESFROM THE SCHOOL OF THREE FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956 EXCLUDING UNKNOWN PAIRS
Sexual combination
Male & Female Female & Female
Male & Male
1955
1956
1955
1956
1955
1956
Both mature
11
10
5
3
5
II
Mature & Immature2
2
Both immature
J
2
Male mature & Female immature
3
4
Female mature & Male immature
TABLE 10. SEXUAL COMBINATIONS IN THREE FIN WHALES CAUGHTFROM THE SCHOOL OF FOUR FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956
1956
1955
Three males
I
3
Female & Two males
Two females & One male
TABLE JI. SEXUAL OCCURRENCES IN THE CATCH OF FIN WHALESFROM THE SCHOOL OF MANY FIN WHALES MORE THAN FIVE
IN THE NORTH PACIFIC IN 1955
2/5* 3/5 2/6 3/6 4/6 2/7 3/7 2/8 2/!0 2/12 2/10-15 2/20** 2/50**
13
3
7
3
1
2
1 2
4
1
1
I
I
2\iumber
Male & Male
5
3
6
Male & Female
43Female & Female
2
Male & Two females
2
Three males
Two males & One Female
Three males & One female
Three females* The lower shows the number of fin whales in a school and he upper shows number of whales caught.
** These schools are somewhat doubtful, possibly shoals of schools.

and there are seven pairs two males and two females respectively. The sexual
conditions of those fin whales are as follows. Among the seven pairs of male andmale, five cases are both mature and one mature in two cases. This may be affected by the size regulation for the catch as stated in the formar part. In those groups,
the pairs of mature male and immature female are more than the one of immature
male and mature female in general, which is already pointed out in the case of two
fin whales' school. Eleven pairs of males are sexually mature and two pairs are

96

T. NEMOTO

composed of one mature male and another immature male in 1956. There are ten
combinaions of mature one male and another female fin whales, two combinations aresexually immature in both whales. Mature males and immature females form threecases but there is no case of immature male and mature female fin whales in 1956.
School composed of more than four
There is none of the record of the perfect catch of the school composed of morethan four, but there are considerable number of the chasing for the school ofmany fin whales more than four. Two cases in 1955 and four ones in 1956 arefound catching three fin whales from the school of four fin whales as illustrated
in Table 10. It is very interesting to note th~t the males are dominant in the catchin spite of the size selection by catcher boats.
Especially the immature males are scarecely observed in those cases. If thesize selection is effective for the catch of those fin whales, the number of female fin
whales might be dominant. It is suggested the dominant catch of males showthese school are composed of more males than females.
The example of the catch of fin whales from the schools of many fin whales isfound in 1955. The occurrences of males and females are given in Table 11. Malefin whales are found more than female in general and if the size selection affectthe catch it should be reverse to the facts. This tendency may comfirm the generalfeature of schools of fin whales in the feeding grounds. In the land mammals, thesocionomic sex ratio is high in females in their group and herd (Ito, 1959), the factof which is the reverse to the fin whales.
It is interesting that the catch of immature males and females are observed
from the comparatively large schools. Two fin whales are caught from the schoolof five fin whales in 1955, and both males are sexually immature. The body lengths
are 53 and 50 feet and other fin whales in the same school are estimated as the samelength. The catch of two fin whales from the school of five whales show those two
females are immature, the body length of which are 58 and 59 feet respectively.
These two cases show to some extent the young agers assemblage and sexual assemblege in fin whales as it is supposed up to this time.
Andrews also recognizes such assemblege in grey whales (Andrews, 1914).
There have been sometimes found the school of fin whales more then ten, however,these schools may be the congregation of many schools especially in the feedingarea to take the shoal of euphausiids. It is generally accepted the schools of
many fin whales have been observed in their migartion route to and from the feeding and breeding areas. Brown (1958) reports the greatest numbers of rorquals
observed by ships are about fifty and thirty in the north Atlantic.
BLUE WHALE (BALAENOPTERA MUSCULUS)

In the North Pacific, blue whales are ocean denizen and their main schools neverpenetrate into the Bering sea (Nemoto, 1959). The number of blue whales observed in the data is also small, and there still remains some question for the reliability of the samples.

SCHOOL OF BALEEN WHALES

97

Signle swimming blue whales are dominant among the schools in the data, and thirtysix blue whales out of thirty-eight schools in 1955. and fifty-eight blue whales outof sixty-seven schools in 1956 are observed to be single in the feeding areas. In
1955, those single swimming blue whales are of more males than females and thisis the same in 1956 too. Sexual maturity conditions are given in Table 12 but it
is difficult to get any concludion from the table because the number is rather limited.
The chasing and the catch are done for one school in 1955 and nine schools
in 1956 which consist of two blue whales in a school. Two blue whales in a school
are caught in 1955, one ofwhch is male, sexually mature, and another is also malebut it is considered it just attains sexual maturity. In 1955, two blue whales are
TABLE 12.

SEXUAL CONDITIONS OF BLUE WHALES CAUGHT
IN THE NORTH PACIFIC IN 1955 AND 1956
Number of whales in a school

1955
1956

2

3

MatureImmature

MatureMatureMale
Female227

42(2/2*)

2(2/3*)

Male
Female

28
21

2
7

3
8(1/2*)
I (1/2*)* Upper shows the catch number and the lower shows the number of whales in a school.
caught from the three blue whales' school, which are sexually mature and just matured ones. I have nine cases of the capture that only one blue whale is caught
from the two blue whales' school in 1956. All eight males are sexually mature andone sexually mature female blue whales is pregnant. It is suggested two blue
whales' schools are composed of more males than female like the cases in 1955.
But it is also considered the male sex ratio in single swiming blue whales is high,and the female blue whales swimming with calf escape the chasing by catcher
boats.
The one reason that the number of blue whales in a school is rather small, is
attributable to the relative abundance of blue whales in the North Paciffc. Comparatively large schools of blue whales had been observed in the Antarctic in
the former age of the whaling, when blue whales were dominant.
SEI WHALE (BALAENOPTERABOREALIS)

There have been considerable differences among the annual catches of sei whales.
The general tendency has not been obtained as for the school of sei whales, butthree sei whales have been found in a school both in 1955 and 1956 as the maximun
number. The school of six sei whales is reported in the previous report (Nemoto,1959), however, the most common schools are up to three sei whales in a school.
Generally speaking, the number of sei whales are comparatively small in a school
comparing with other fin and humpback whales.
In 1955, ten males and nine females are caught from single swimming sei whales.

T. NEMOTO

98

Four males and two females of them are sexually immature. But two immature sei
whales have been caught from the school of two sei whales. Although the sample
is rather scarce, it may be considered that immature sei whales sometimes swim
alone to feed more often than the sexually mature sei whales. The sei whales caught
in 1956 also show such tendency that the sexually mature whales form the schoolof two or more whales
The cases of two sei whales caught from two whales' school are observed bothin 1955 and 1956. One case in 1955 and five cases in 1955 respectively. All sei
whales are sexually mature and all females are pregnant, the compositions of which
TABLE 13. NUMBER OF SEI WHALES IN A SCHOOL CHASED BY
CATCHER BOATS IN THE NOTH PACIFIC IN 1955 AND 1956
Number of sei whales
in a school
1
19
4

1955
1956

2
II
5

3
2

TABLE 14. SEXUAL COMBINATIONS IN SEI WHALES CAUGHT IN
THE NORTH PACIFIC IN 1955 AND 1956
IN RELATION TO
NUMBER IN THE SCHOOL
M&M

2/2*
M & F

F&F

3

1 (Female )pregnant

I (Both)pregnant

1955
1956

2/3*
_________,..___
M&M M & F
1 (Female )pregnant

3 /3*M, F & F
1 (Both females)pregnant* Upper shows the number of sei whales caught from a school and the lower shows thenumber of whales in a school. M-Male, F-Female.

are given in Table 14. Although the number is rather small, the male pair is dominant among the schools, and there are one combination of male and female, andanother of both females respectively. Three sei whales are caught from three whales'school in 1955. Two pregnant females and one sexually mature male are present
in the school. There have been two cases of the catch of two sei whales from theschool of three sei whales, and one is the pair of male and female sei whales, and two
males are another.
Owing to the small number of the examples as repeated, there has been no clear
tendency in the schooling of sei whales. It is suggested only that the two males'school is more than female combination in the school of two sei whales like thecase in fin whales.
HUMPBACK WHALE (MEGAPTERA NOVAEANGLIAE)

The number of humpback whales caught in 1955 and 1956 is not so large as fin
whales. In 1956, single swimming humpback whales are observed in nineteencases and two humpback whales in a school eight cases. Three or more whales

SCHOOL OF BALEEN WHALES

99

found in a school are rather scarce, and humpback whales are observed up toseven in a school. The same tendencies are found in the data in 1955, whensingle humpback whales and schools composed of two humpback whales are dominant among them. Especially many pair humpback whales in a school are reported
m 1955 as shown in Table 15.
TABLE 15. NUMBER OF HUMPBACK WHALES IN A SCHOOLIN THE NORTH PACIFIC IN 1955 AND 1956
Number of whales in a school

1955
1956

2
31
8

27

19

3
2
1

4

6

5

7

TABLE 16. SEXUAL COMBINATIONS IN THE PAIR HUMPBACK WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Sexual combination
Male & Male

1955
1956

Male & Female
31

Female & Female

TABLE 17. SEXUAL CONDITIONS OF HUMPBACK WHALES'SCHOOLS IN THE NORTH PACIFIC IN 1955 AND 1956
1/2*

1/1*

MatureImmature(Pregnant)Total----------

8
9
(5)
17

10

1955

1956

1955
....---Female

Male
10

1956

Male

FemaleMale

FemaleMale

Female

7
2

5
5
(3)
10

7

6

1

2

7

4
(3)
10

2

3

9

* Upper shows the number of whales caught and the lower shows the number of sei whales
in a school.

TABLE 18. SEXUAL COMBINATIONS IN HUMPBACK WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Male
Female

2/3*

2/4*

3/4*

1

2

2

2/5*

1/7*

2

* Upper shows the number of catch and the lower shows the number of whales in a school.
From the biological data collected on the whaling factory ships, comparatively
many immature humpback whales have been found as the single swimming whale.
The termination of two whales in a school is done in four cases in 1955 and three
in 1956, the occurrences of each sex of which are given in Table 16. The pair ofmale and female is dominant among the schools although the school number israther small. It is interesing the sexually immature male or female humpback
whales are present in the pairs in five cases, and only two cases composed of sexuallymature whales. This tendency has not been observed in other baleen whales.
The sexual conditions of one whale from the pair are illustrated in Table 17.

T. NEMOTO

100

The catch of humpback whales from three or more party is far less comparedwith said cases. Three whales are caught from four humpback whales in a school
in 1955 which composed of one resting mature female and one mature male and immature male. The occurrences of each sex in those catches from schools composedof three or more whales are given in Table 18.
The humpback whales in the breeding area seem not to form groups of many
whales, Chittleborough (1953) describes only up to three adults in a school in the
coasts of Australia, and Brown (1957: 1958) describes that seven is the greatest
number and other observations are all of single or very small parties in the northof the equator in the Indian ocean. About twelve whales are found in the coast ofAustralia in two of the four records in his report, however, the number of the observations on humpback whales in the area is rather scarce and these observations do
not reliably sample the coastal areas of Australia as discussed by Brown. The sexual
segregation in humpback whales in migration is very tipical, and those results should
be examined by futher materials. In the breeding areas of the North Paific,
there is also very few data on the schools of humpback whales.
RIGHT WHALE (EUBALAENA GLACIALIS)The observations, marking and bilogical research on right whales have been rather
scarce both in the Antarctic and in the North Pacific. The observations on rightwhales in the North Pacific are given in Table 19. The single swimming rightwhale is dominant among the schools and four right whales is at most in a school.
Japanese investigations on right whales have caught eleven right whales in recent
years with special permssion by government. And those right whales have been
all single swimming right whales but one case, which consists of two right whales.
When the one puberty female is caught (Kasuya, 1962. personal communication),
it is said the another right whale comes back again after a little while and swims
around the captured right whale.
TABLE 19.

NUMBER OF RIGHT WHALES IN A SCHOOLIN THE NORTH PACIFIC
Number of whales in a school

1941-1957*
1961-1963

Coast of Japan
North PacificNorth Pacific

53
58
21

2
15
30
8**

3
2
4
4

4
2

* Omura (1958).

* * Including one cow and calf.
Other ten right whales consist of seven males and three females. Among sevenmales, three whales are sexually immature, and two females are also sexually
immature out of four females. Two pregnant females are caught in 1963, when
they are swimming as the single in the feeding areas in the North Pacific.

SCHOOL OF BALEEN WHALESIOIGREY WHALE (ESCHRICHTIUS GLAUCUS)
According to Gilmore (1958), grey whales are not a highly social animal, and the.
most commonly integrated social groups are the pair, and the trio. He considers
the trio is made up usually a female and two males, and is also somewhat imparmanent. Scammon (in Andrews, 1914) writes also the case of the school, composedof a female, her calf and a male will go to the northward to the feeding. The observation of schools of grey whales are also found in the papers by Andrews (1914),
Nasu (1960) and Pike (1962), which suggest the school of grey whales is sometimes
containing many whales. As a important notice, the leadership by the female inthe school of grey whales should be noted in relation to the land mammals such as<leers. But the discussion by Andrews is a preliminary one, and these ecologicalpoints should be examined on more detail characteristics.
The available observations on the school of grey whales are rather few. In
1955, Japanese marking ship found grey whales feeding in the north-west sea of St.
Lawrence Is. in Bering sea. In the descriptions, one to three groups of grey whales
are mostly found. Two grey whales, 41 feet and 37 feet long are found in a schoolat 63-34 N and 172-48 W on 2th August. Other two pairs of grey whales, 40 and
36 feet, and 37 feet, and two trio (36 and 37 feet trio) are reported in tne neigbouring
waters and the most schools are single, pairs and trios.
In recent observations, Wilke and Fiscus (1961) describe eight grey whalesin scattered pairs were seen moving toward narrow Kodiak and Ugak Is on llth
May in 1957, and two grey whales were seen from the 'John N. Cobb' feedingnear 67-40N, 167-12W on 19th Ausust in 1959, and on 20th Aug. three others
are feeding. These observations comfirm the comparatively small unit in schoolingof grey whales in the feeding areas, although they sometimes form the huge congregations in the feeding areas in the narrow place.
DISCUSSION AND RESULT BY MARKING RESEARCH
The general observations on the school of whales chased in the marking research
have been carried out in the North Pacific and the Antarctic, and the catch log on
the recaptured marked whales usually refer the behaviour of the whales including
other whales in the same school. From these materials, very interesting consideration on schools of baleen whales are deprived.
One of the most interesting example is found in the marking for the pair of cow
and calf of fin whales in the North Pacific. In 1955, two cows with calves weremarked on 18th July and 26th July. These adult females are caught in 1957, when
they are feeding in the North Pacific solitary. Further, these two whales are pregnant.
The patterns of the whales may be summerized as follows. In the summer of 1955,
these two mother whales were feeding with their calves, and their calves were within
two years after the birth, perhaps yearing, considering their body length (Ohsumi,
Nishiwaki & Hibiya, 1958: Laws, 1961). The larger calf might be feeding on theplanktons with his mother, as the body length is about 46 feet which is estimated102

T. NEMOTO

4

4

3

3

2

2

0

0

:"
0
\I)

>CJ

"'
Q_
0

u:;

5

9

5

10

Number of Fin Whales

Fig. 3. Formation and separation in the number of whales in the school of fin whalesin the Antarctic (Left) and North Pacific by the marking research.

M

D

N

5

10

20

Number of fin Whales

Fig. 4. Formatin and separation in the school of fin whales in the Antarctic by themarking research. The _marks are recovered within the summer Antarctic season ofeach case.

103

SCHOOL OF BALEEN WHALES

after the weaning. When the mother fin whales recaptured in the feeding areas
in summer, they have five and nine months' foetuses calculated from the body length(Ohsumi, Nishiwaki & Hibiya, 1958). They must have copulated five and ninemonths in the late winter respectively. January and October are the possible
breeding months for them and the grown calves might be free from the motherfin whales before the time of those copulations because there are few cases of theother whales joining in the pair of cow and calf schools. The fin whales seperated
with males after copulation between the fertilization and being caught.
Au.

Ju.

Ap.

Fe .
...c

g De.

:2
Oc.

Au.

Ju.
5

10

15

20

Number of Fin Whales

Fig. 5. Formation and separation in the number of whales in the school of fin whalesin the North Pacific by the marking research. The mark are recovered within theseason of each case.

The number of baleen whales in a school has been examined by the marking
research too. As it is discussed in the former part, the single swimming fin whales
are considered to decrease with the proceeding of the summer season in the observation of the catch log. But the marked fin whales in a school of many whales partwith the parties, and they are found in the schools of smaller number. This would
deary show the breaking down of the school of fin whales in the feeding areasin the summer season too. Considering these two facts together, the school of fin
whales may be inconstant in the feeding areas in the summer. It is not clear
which is more important factor from the ecological point of view. The clear tendency
to form the school of male and female pairs and some pecurial sex ratio should beconsidered again as one of the significant point in the school of fin whales in thefeeding grounds.
If it is supposed that fin whales migrate south to breed, the formation ofschools in the feeding areas may be very usefull. On the other hand, the se-

104

T. NEMOTO

peration of the sexually mature fin whales from the other younger whales in theschool may break the school. It is considered to be natural that mutual affection is
one reason to form or break the schools among the sexually mature fin whales. This
type of the seperation in the school of fin whales in the feeding grounds has been
observed in the Antarctic too. The case of the formations in the school also havebeen observed, however, available examples are less than those of the seperations.
To make up the gap of the above described results by the observations by catch
log and the marking research, futher accumulations of the materiales are necessary.
And it should be considered that the pregnant females, sometimes feeding alone
in the feeding areas as discussed in the former part, leave the north sea feedingarea earlier than other whales (Laws, 1959). The schools consist of many fin whales
may seperate and form each party by some reasons such as affections, and younger
agers assemblage keep their schools still in the feeding grounds. These schools
consist of comparatively many small whales are sometimes observed in the marking research in the North Pacific and the Antarctic.
The variation of the number of the whales in a school for a long time also has
been checkd by the marking the results of which are shown in Fig. 3, In these
examinatins, many schools of fin whales decrease the number of the party in theschools, but some schools have the participipants, between the time being marked and caught.
Besides fin whales, the marking data on the schools of other baleen whales arerather scarce. In the North Pacific, a school of three blue whales is observed on
20thJuly and one of them, the marked whale, is found solitary after twelve days, on
24th July.
Five blue whales observed in a school in the Antarctic on 13th Dec. and they
have six members in the next year, namely 22nd January, after the lapse of nineteendays. One of a pair of blue whales marked on 19th December in 1958 is caught
on 8th February 1959 when the blue whale is swimming solitary.
There is one case of humpback whales in 1958. The pair of humpback whales
marked on 25th December in the Antarctic and found in the next year in the same
number pair of two on lst February.
The ecological habit such as the forming or the breaking of schools must
be connected with the very characteristic feeding migration in baleen whales. The
solution of this origin and history may be one key to the problem (Marr, 1962).
SCHOOL OF DIFFERENT WHALE SPECIESSchool of blue and fin whales
Sometimes baleen whales swim with different species of whales in the same school.
Gunther (1949) describes the case of one blue whale swimming with four fin whales
in a school in the Antarctic. From the data collected in the Antarctic from theyear 1957 to 1958, it is rep.orted five cases composed of blue and fin whales (Nemoto,1959). In that paper, that the sexually immature blue whales swim with the sexual-

SCHOOL OF BALEEN WHALES

105

ly mature fin whales and the number of blue whales are always less than fin whales or
the same number, is described. The followings descuss the problem chiefly according to the marking and the catch results.
School composed of fin and blue whales
There are eleven schools composed of fin and blue whales up to these days as given
in Table 20, five of which were already reported in the previous paper (Nemoto,1959). The number of blue whales are the same or less than fin whales, and the
body length estimated by the crew of catcher boats shows the possible sexual
immaturity as described by me. The school composed of less fin and more blue
whales in number has not been observed in the records yet.
TABLE 20. THE OCCURRENCES OF THE SCHOOL COMPOSED OF FIN
AND BLUE WHALES OBSERVED BY JAPANESE WHALE MARKING CRUISE
IN THE ANTARCTIC FROM 1954 TO 1961

Number of whales
Estimated bodylength in feet
Total number ofwhales in a school
Number of whales
Estimated bodylength in feet
Total number ofwhales in a school,---"'-,,---"'-,,---"'-,,---"'-,

Blue
1

Fin

Blue

Fin

Blue
1

Blue

62

71

70

68

73

2

2

60-63

,..---"---.

_____....._,,

Blue Fin
1
4

Blue Fin
1
4

Blue Fin
1 5

80

70

65-67

65-70
6

5

,---"'-,

Fin
2

78

Blue
1

Fin
3

72

63-65

3

3

,..---"---.

5

Fin
2

..----...-

Blue Fin
4
2
64-65

73

4

_____....._,,_____....._,,

Blue Fin
2
6Blue Fin
2 Ca 10? 50-65

60

Ca 12

8

6

70

TABLE 21. THE OCCURRENCES OF THE SCHOOL COMPOSEDOF FIN AND SEI WHALES IN THE FEEDING GROUNDSNorth Pacific
Antarctic_____...__.....
,-----"--o,Number of whales
Estimated length of whales in feet
Total number of whales in a school

Fin

Sei

2

2

60

45
4

Fin
2
56-57

Sei
4
45-48

6

~

Fin
I
58

Sei
2
3

School of fin and sei whales
There have been three cases of fin whales swim with sei whales in the records.
In 1960, a school of two fin and two sei whales is observed in 56-32 S, 77-06W
in the Antarctic, and two cases observed in the North Pacific. The latter cases
are composed of two fin and four sei whales in one and one fin and two sei whales
in another case. The body sizes of fin whales are cmparatively small, andthey are estimated to be sexually immature or just matured. On the contraly
to this, the body length of sei whales are large and possibly sexually mature. I
would consider this is the same tendency with the case of blue and fin whales andthat the larger baleen whales sometimes swim with the different smaller species ofbaleen whales in the case that they are sexually immature and the number is thesame or the less. The sexual potensiality may be the one reason to join a school106

T. NEMOTO

of different baleen whales in the feeding areas. This tendency is considered
common m Balaenoptera whales both in the Antarctic and the North Pacific.
School of sei and bryde's whales
A school of sei and bryde's whales is obserevd in the adjacent waers to Japan in
1961. About 180 miles from Kinkazan, the north-east part of the Pacific coast ofJapan, one mature male bryde's whale, testis of which are both 1.6 kg, is foundswimming with a immature sei whale and those two whales are caught by catcher
boat.
School of fin and little piked whales
A little piked whale (Balaenoptera acutorostrata) is observed in a school of fin whales
on 13th Dec. in 1959, 59-17S, 82-52W in the Antarctic. But it may be acceptedthat the little piked whale only follows the school of fin whales a little while.
There has been no record of the school composed of Balaenoptera and Megaptera
whales. Sometimes it is observed that humpback whales feed with Balaenoptera
whales in the same feeding areas in the very near place and seem to be in the sameschool, but they are split into respective species after a while by the chasing. The
swimming speed and the general diving depth may have the relation with the formation of schools in the case. And frequent turning in humpback whales is also one
reason of the seperation too.
Mackintosh (1942) and others (Matthews, 1938: Nemoto, 1959: 1962b) pointout that the pecurial migrating time to the feeding areas and segregation in the
distribution in the feeding areas both in the southern and the northern waters
is observed in each baleen whale species. One example in the North Pacific isshown in Fig. 6. There are differences among the distributions of baleen whales
according to species, and the primary preferances of their foods is considered as thefirst reason for their distributions. Blue whales feed only on euphausiids, and sei
whales prefer copepods especially Calanus plumchrus, but they rarely take Calanus
cristatus in these waters (Nemoto, 1959). Fin whales feed on euphausiids as wellas copepoda, Calanus cristatus, but they rarely take Calanus plumchrus (Nemoto, 1959).
These selections of foods and different oceanographic conditions for each foodspecies may form such distriutions, however, the feeding range in each speciesof baleen whales and the occupation is considered if it is fixed within a certain time.
Thus the two types of ecological segregations (Miyaji & Mori, 1953) are recognizedin these distributions. In the previous report (Nemoto, 1959), I suggest the possible
biological strength, numbers and migration time between two baleen whalescause some segregations in the feeding grounds. The case that the habit of feeding
is affected also by the number of each species is pointed out by Elton on the land
animal Buffalo (Bos cajfer) in Africa (Elton, 1927).
These types of the segregations in the feeding grounds have been observed
between blue and fin whales, fin and sei whales. In recent years, the distributions of
fin whales become tdifferent from the former days, and sei whales also penetrate
into the Antarctic high latitudes and waters of pack ice. This is partly attrubut-

SCHOOL OF BALEEN WHALES

107

able to the numbers of individuals and biological strength among baleen whales
as suggested by Nemoto (1959). These biological strength may be confirmed by
the presence of the school of different species as disscused in the former part.
There is another explanation for the fact that the different species baleen whalesof the same size may sometimes swim togather in the feeding grounds. But considereing the number of baleen whales in a school, that the larger whales are usuallyless than the smaller species, the former is more suitalbe explanatin for the problem.

"'!:'·=t-=-=-=-~~===~~========~~-=-~~=-~--~-------~~~~·
Fig. 6. Distributions of baleen whales in the North Pacific in July in 1960, showing thedifferent patterns in distributions of baleen whales by species. Open circle-Fin
whales : Black circle-sei whales : Cross-Blue whales.

COW AND CALF PAIR

It seem rather rare that the pair of cow and calf swims with other whales evenin the same species. Gunther (1949) describes a case that a cow and a calf swim
with other whales but it is only one case in his report. Slijper (1958) also states
the maintenance of the family in blue and right whales, however, the sources ofwhich are not indicated.
Both in the Antarctic and North Pacific, the cases that the pair of cow and calf
is found with other whales are rather scarce as illustrated in Table 22. But inhumpback whales, the calves sometimes are accompanied not only by their motherwhales but also other adults (Chittleborough, 1953).
In the Balaenoptera whales, only females give protections to their calves after
their parturition. The new born calves in Balaenoptera whales can swim perfectrywith their mother but the family of Balaenoptera whales consists only of females and108

T. NEMOTO

their calves in general. Those pregnant whales in feeding grounds might migrate
to the south single or with other whales but they will be alone after their parturition.
Chittleborough (1953) observes two cases of cow and calf pairs of fin whales
but no other whale in them in the waters off Australia in the lower latitudes.
TABLE 22.

THE SCHOOL OF COW AND CALF PAIR AND OTHER WHALESFOUND WITH THE PAIR IN THE FEEDING GROUNDS
Number of other whales with the pair
Numberof Cow& calfAntarctic
Blue whales
Fin whales
Humpback whales
North PacificBlue whales
Fin whales
Sei whales
Humpback whales
Bryde's whales

+l

+3

+2

+5

+6

+9

6
14

9

4

2

3
16

2

9
8
2 years

Less than 2
years ?

-5~9months-

Cow & Calf

0

/

0

0

8

+4

Weaning

Pregnant00Seperotion

Poturition

Feeding &Nursing

WinterSummer()_/Pairing

Copulation

8~
Feeding~
WinterSummer

WinterSummerFig. 7 Schema of the cycle of cow and calf fin whales in the North Pacific by the marking
research. The marks were hitin 1955 and recovered in 1957 both in summer seasons.

The pair of cow and calf in humpback whales sometimes swims with other
adult whales. This tendency is given in Table 22 too. Chitteleborough (1953) also
describes that a calf usually accompanies a single adults, but sometimes two adults
were present. This confirmes the results in the Antarctic area in Table 22. If
the starting of the pair of cow and calf to the south only by themselves, the formationof the school may be done in the route or in the feeding areas where the range in

SCHOOL OF BALEEN WHALES

109

the distribution is rather small and they may contact with each other more often
than other baleen whales. The companionship is built in their migraion and feeding, however, the sex of the members are still unknown.
The pair of cow and calf have been observed in a considerable number in thefeeding areas. But it is very rare to be found with other whales besides thefamily. Namely cow and calf form the family by themselves. The nursing duration is about seven in fin whales, and fin whales uaually do not form the school ofmany whales with the family within it, as a conclusion.
It is clear from above facts, that Balaenoptera baleen whales do not accept thefamily (cow and calf) in their school although the calf of Balaenoptera is able toswim with their mother and adults.
SUMMARY

The preliminary consideration on the school of baleen whales in the feeding areas
are made based on the Antarcic and the North Pacific baleen whales caught by theJapanese whaling and the whale marking data. The important points are as
follows.
1. The number of baleen whales in a school is examined on fin, blue, sei, humpback, right and grey whales. The seasonal change in the number of fin whales
in a school is suggested.
2. The sex ratio and sexual combinaions are studied on the school of baleen
whales especially in fin whales. From the catch of the pair fin whales, the combination of male and male, and male and female fin whales are more than the oneof both females. The sexual combinations of members of the trio and otherschools of fin whales are also investigated.
3. Based on the marking research, the following up to the number of baleen whales
in a school is done both in the Antarctic and in the North Pacific. The numberof fin whales in a school varies and the breaking up of the school is observed in thefeeding grounds. Two pregnant fin whales are caught which had been marked
when they swam with calves, and they are feeding solitary, suggesting one type ofthe formation and seperation of breaking the school in fin whales.
4. The pecurial feature of the school of different species of baleen whales aredescribed. These schools are observed in fin and blue whales, fin and sei whales,and sei and bryde's whales. Among these combinations, the larger species ofwhales are the same or less in number than the smaller baleen whales in a school.
The estimated body lengths of the blue whales in the school of fin and blue whales
are comparatively short, and fin whales also small in the school of fin and sei whales
and the possible reason, sexual potentiality, is suggested for the combination of different whale species.
5. The family of fin whales, cow and calf, is examined. It seems that the fin whales
do not accept the family (cow and calf) into the school, and this tendency may begenerally observed in Balaenoptera baleen whales.

110

T. NEMOTO

REFERENCES
ANDREWS, L.C. (1914). Monographs of the Pacific cetacea. I, The California gray whale (Rhachianectes
glaucus Cope). Mem. Amer. Mus. Nat. Hist., N.S. 1(5): 231-84. 9pls.
BROWN, S.G. (1957). Whales observed in the Indian Ocean. Noted on their distribution. Marine. Obs.,
London, 27: 157-65.
- - (1958). Whales observed in the Aitlantic Ocean. Marine Obs., 28(181) & (182): 142-6, 209-16.
CHITTLEBOROUGH, R.G. (1953). Airial observations on the humpback whale Megaptera nodosa (Bonnaterre),with notes on other species. Aust. J. Mar. Freshw. Res., 4(2): 219-26. 2pls.
CLARKE, R. (1962). Whale observation and marking off the coast of Chile in 1958 and from Ecuador towards
and beyond the Galapagos Islands in 1959. Norsk Hvaifangst-Tid. 51(7): 265-87.
CLARKE, R & Ruun, J.T. (1954). International co-operation in Antarctic whale marking the voyage of the
Enarn to the Antractic 1953.
Norsk Havaifangst-Tid. 43(3): 128-46.
ELTON, C. (1927). Animal ecology. London
FUJINO, K. ( 1960). Immunogenetic and marking approaches to identifying subpopulations of the north Pacificwhales. Sci. Rep. Whales Res. Inst., 15: 85-142.
GILMORE, R.M. (1958). The story of the gray whale.
GUNTHER, E.H. (1949). The habits of fin whales. Discovery Rep., 25: 113-42.
IMANISHI, K. (1951). Ningen izen no Shakai. [Society before the man.] Tokyo.
- - (1959). Dobutsu no Shakai to Kotai. [Society and individual in animals.] Tokyo.
ho, Y. (1959).Hikaku Seitaigaku. [Comparative ecology.] Tokyo.
LAws, R.M. (1959). The foetal growth rates of whales with special reference to the fin whales, Balaenoptera
physalus Linn. Discovery Rep., 29: 281-308. !pl.
- - (1961). Repoduction, growth and age of southern fin whales. Discovery Rep., 31: 327-486. 4pls.
MACKINTOSH, N.A. (1942). The southern stock of whalebone whales. Discovery Rep., 9: 67-158.
MARR, J.W.S. (1962). The natural history and geography of the Antarctic krill (Euphausia superba Dana).
Discovery Rep., 32: 33-464. lpls.
MATTHEWS, L.H. (1938). The sei whale, Balaenoptera borealis. Discovery Rep., 17: 183-290. 2pls.
MIYAJI, D. & Mori, K. (1953). Dobutsu Seitaigaku. [The animal ecology.] Tokyo.
NEMOTO, T. (1959). Food of baleen whales with reference to whale movements. Sci. Rep. Whales Res.
Inst., 14: 149-290. I pl.
- - (1962a). A secondary sexual character of fin whales. Sci Rep. Whales Res. Inst., 16: 29-34. I pl.
- - (1962b). Food of baleen whales collected in recent Japanese Antarctic whaling expeditions.
Sci,
Rep. Whales Res. Inst., 16: 89-103.
0HSUMI, S., NISHIWAKI M. & HrnIYA, K. (1957). Growth of fin whales in the northern Pacific.
Sci. Rep.
Whales Res. Inst., 13: 97-134.
PIKE, G.C. (1962). Migration and feeding of the grey whale (Eschrichtius gibbosus). J. Fish. Res. Bd. Canada,
19(5): 815-38.
SLIJPER, E.J. (1958). Das Verhalten der Wale (Cetacea). Handbuch der :(oologie. 8Bd. 15 Lief., 14 Tei!,
14 Beit., 1-32.
WILKE, F. & Fiscus, C.H. (1961). Gray whale observation. J. Mamm., 42(1): 108-9.

SQUIDS AS THE FOOD OF SPERM WHALESIN THE BERING SEA AND ALASKAN GULF
TAKASHI OKUTANI* AND TAKAHISA NEMOTO

It is well known that sperm whales, Physeter catodon (Linnaeus), feed on squids inthe world seas. There are many reports on the feeding of sperm whale and squids
found in the sotmach of that whale (Mathews, 1938: Mizue, 1950: Clarke,
1955: Betesheva & Akimushikin, 1955: Clarke, 1962). Betesheva & Akimushkin(1955) described the food species of sperm whales in the waters of Kurile Island,and Pike (1950) and Rice (1963) reported the food animals of whales in the west
coast of America.
The pelagic whaling by Japan and U.S.S.R. have been operating in the Aleutian
waters and Bering Sea, and sperm whale is one of the important species of thecatch therefrom. However, the foods of the sperm whales caught in the northern
North Pacific have seldom been examined, although a report on the stones and otheraliens found in the stomachs of the whales was published by Nemoto and Nasu
( 1962).
The stomach contents of the sperm whales from the waters around AleutianIslands, Bering Sea and Alaskan Gulf were collected in 1963. These specimens
were examined taxonomically, and their occurrences were studies in viewpoint of
distributions of the squids and the predators in the north Pacific. Here this reportdeals with the preliminary results of the investigation, and this study will be continued to contribute the knowledge on distribution and taxonomy of squids in the
North Pacific.
MATERIALS
The present samples were collected through the survey carried out in the North
Pacific on board the factory ship. This investigations are mainly carried out in thewaters around Aleutian Is., Alaskan Gulf and the Bering Sea. The field observations
are made on all sperm whales caught, and the contents of stomachs are descriminatedas squids, fish and other items. The observation was made on the first stomach
content which is in fairly better condition than that elsewhere. However, sometimes second stomach was erroneously dissected for examination. The content
found in the first stomach in worse condition might be the second stomach content
surged back into the first. The squids have been preserved in 10 % formalin sea
water, and they are tentatively classified into types A,B,C,D,E and G. A part ofsamples taken out from the whale stomach was brought home for close examination.

* Tokai Regional Fisheries Research Laboratory, Tokyo.
Ill

~: !
I'

I
I
I

112

T. OKUTANI AND T. NEMOTOSYNOPSIS OF THE SPECIES IDENTIFIED
As was mentioned in the preceding section, at the field observation six forms
discriminated were classified into A, B, C, D, E and G. On the basis of the samples
brought home, each group was found to be composed of the species as follows :A: Moroteuthis robustus (Verrill, 1876)
B & D: Gonatopsis borealis Sasaki, 1923, makko, n. subsp.
C: Mastigoteuthis (?) sp.
Stigmateuthis sp.
Galiteuthis armata Joubin, 1898
Taonius pavo (Lesueur, 1821)
E: Gonatus (Berryteuthis) magister Berry, 1913
G: Gonatus fabricii (Lichtenstein, 1818)
Only C-Group was found containing four species. This is because these
species have gelationus integuments which are easily matilated badly when takenby the predators. Sometime fragments of transparent pens of some unidenified
Cranchiids were remained undigested.
Synoptic notes on the results of examination on the specimens are present in
the following lines.
OEGOPSIDA

Onychoteuthidae

Moroteuthis robustus Verrill, 1876
Because of huge size, reddish variegation and rippled skin, this species is easily
discriminated at the field observation on board the factory ship. One of thespecimens brought home was measured about 700 mm in dorsal mantle length.
Both tentacles were removed, but other characteristics are quite agreeable to thedescription by Sasaki (1929). Another specimen of head-foot part (mantle andvisceral parts lacking) is much larger than the other, and the tentacular club iswell preserved as is illustrated in Fig. 1 a. The specimens examined for the present study are generally gigantic in size, but a unique example of 300 mm-individual was found in the course of field observation. (seep. 118.)
Histioteu thidae

Stigmateuthis species
A badly matilated specimen was examined. The mantle length measured 100 mm
and the longest arm, 300 mm. A part of the integument with some photophores
is preserved. But identification to the species cannot be made because of lack oftentacle.
Gonatidae

Gonatus (s.s.) fabricii (Lichtenstein, 1818)
A single specimen brought home presented a very large size: Dorsal mantle
length, 300 mm; width of the mantle, 56 mm; length of the fin, 170 mm; widthof the fin taken together, 150 mm.

FOOD OF SPERM WHALES

113

Mantle is robust, purplish in color in preserved state, elongated cylindricaland length is about five times diameter. The fins are muscular and rhomboidal
in outline. They seem to present more elongated shape than those of younger
specimens taken from the North Pacific on other occasions. Arms have two seriesof hooks on inner rows and two series of small suckers on outer rows. Armformula is 3, 1, 2, 4.
The distal parts of both tentacles which may be the most important key ofidentification, were already lost when the specimen was taken out from the whale
stomach. However, rows of small fixing pads disposed on both margins of suckerbearing face of the tentacualr carpus were observed. These rows of pads in
G. fabricii reached far proximally than those in the next species. From suchcharacter and shapes of locking cartilages led the present authors to the conclusive
identification of the present specimen.

Gonatus (Berryteuthis) magister Berry, 1913
Specimens examined are mostly adults measured about 200-250 mm in dorsal
mantle length. They are seldom found broken into the body and head-foot parts, as
their locking apparatuses may be fairly tighter than those of other species.
This species is readily identified by muscular and broad fin and moderately
squat body. At a glance, it may be taken as Ommastrephids, if four-series ofbrachial armatures and peculiar tentacular armatures are overlooked.
Nothing could be added to the careful descriptions by Berry (1912 as a partof G.fabricii; 1913, an amendment of the name) and Sasaki (1929).
Gonatopsis borealis Sasaki, 1923 makko*, n. subsp.
Oegopsida of moderate size; integument soft in touch and smooth all over.
Mantle loligiform, soft, subcylindrical, tapering gradually posteriorly to an acutely
attenuated point ; anterior margin truncated, projecting very slightly at the middorsum, broadly emarginated ventrally leaving rounded lateral angles on bothsides of the funnel ; the widest part of the mantle about one-third the dorsal
mantle length. No sculptures and color patterns present externally but dark
violet internally (in preserved state).
Fins muscular but rather soft with thinned margins, one-thirds as long as thedorsal mantle length, subrhomboidal, length equal to the width of both fins taken
together, obtusely angulated at three-tenths posterior from the anterior margin.
Head as broad as the mantle opening. Neck moderately constricted, probably marginated by a circum-nuchal ridge, which is indistinct in the type specimen.
N uchal locking cartilage elongated rectangular with rounded corners, feebly narrowed at the middle, width a quarter long. Funnel excavation demarked bydepressed nuchal folds on both sides. Funnel moderate in size, semilunar valve
presents inside. Dorsal funnel organ V-shaped, the posterior tips of rami reachas far as the anus. Ventral organs small and ovoid. Funnel locking cartilage
lanceolate, slightly curved, tapering anteriorly and widened posteriorly and then

* The subspecific name, makko, means sperm whale in Japanese.

114

T. OKUTANI AND T. NEMOTO

rapidly narrowed to an angulated posterior end; groove very shallow, widened
posteriorly ending an open end. Mantle locking cartilage very weak and ridgelike in shape.
Arms robust, very powerful in appearance; the ventral pair decidedly shorter
than the others and as long as two-thirds the longest arm; the arm formula 2, 3, I, 4;
the longest arm attains two-thirds the dorsal mantle length. All of the arms nearly
the same strength, gradually tapering distally ; the sucker-bearing faces flat meeting with the side faces in a rectangle ; the aboral side roundish. lntegumental keel
poorly developed on the third lateral arms. Web not well developed except at
the proximal portion of the ventral arm. Armatures of arms composed of hooks
and suckers. In the ventral pair, they present only suckers with several teeth
at the distal margin of the horny rings. In other pairs of arms, the proximal
several rows are loosely arranged suckers, there followed about thirty transverserows of two small suckers outer side and two large hooks of inner side each. The
outer suckers are borne on the thick and long pedicels and bear horny rings withfew triangular teeth at the distal margin. The inner hooks are very sharp withvestigial sucker-like structure proxiamally. Tentacle completely absent. Buccal
membrane papillated and dark violet in color (in preserved state) with sevenprojections on the margin, each suspended by long rib.
Gladius slenderly penniform, about one-fifteenth as broad as long.
Radulae not examined.
Types*: Holotype, male, found from the stomach of a sperm whale ; the integument
is somewhat matilated probably by action of digestive fluid of the whale. Dimensions of the type specimen are as follows : dorsal mantle length, 350 mm ;width of the mantle, 55 mm; length of the fin, 100 mm, width of the fin taken together, 100 mm; length of the dorsal arm (right), 200 mm; second lateral arm(right), 210 mm; third lateral arm (right), 225 mm; ventral arm (right), 170 mm.
Another specimen (paratype) with the dorsal mantle length 300 mm long is
also matilated and separated into two parts. The third specimen (catch number
39: 52°26N, 175°11E) was only head-foot part remained and was the largest of all.
The longest arm measured 300 mm in length and the arm formula was 2, 1=3, 4.
Remarks: At a glance, the present new subspecies is very similar to the typical
Gonatopsis borealis Sasaki which is abundant in the northern North Pacific. However,some external morphological characteristics do not coincide with those of G. borealis,
unless G. borealis presents a remarkable individual changes in proportion of various
parts of the body.
An abridged comparison of those two types are as follows :typical borealis
makko, n. subsp.
General shape of the mantle Cylindrical, somewhat
Cylindrical, verysquat; skin thickslender; skin thin
Fin length
2/3 total breadth or
The same as the total
2/5 mantle length
breadth or 2/3 mantle
length* Deposited in the National Science Museum, Tokyo, Reg. Nos: Mo. 13311 (Holotype), Mo. 13312(Paratype).

FOOD OF SPERM WHALES

115

N uchal locking cartilage

Panduliform, with aElongated rectangular
gentle constriction
near the middle
Funnel locking cartilage
Panduliform, 1/3 asCurved lanceolate,broad as long
1/4 as broad as longArm
2/5 the mantle length
2/3 the mantle length3, 1=2=4
2, 3 ( =) 1, 4
The criteria common to both forms are armature of arms which composedof four series of suckers and hooks all the way through and the sagittate outline of
the fins. In contrast to these, another known Gonatopsis, G. octopedaus Sasaki has
8-12 series of small suckers on the distal parts of the arms and a reiniform fins.
Distribution: Probably a bathyelagic zone of the northern North Pacific.
Mastigoteuthidae
Mastigoteuthis ( ?) sp.
A single strange specimens in a half digested state is taken to be a Mastigoteuthid.
The specimen has degenerated tentacles which present only muscular short
appendages between the third lateral and ventral arms. Degeneration oftentacles are hitherto known on Gonatopsis (Gonatidae) and Octopodoteuthis (Octopodoteuthidae) and none on any other families. Therefore, it is still inconclusive whether the present specimen belongs to Mastigoteuthidae.
Cranchiidae
Taoniuspavo (Lesueur, 1821)
Galiteuthis armata (Joubin, 1898)
Two above-mentined Cranchiids were found mixed with the preceding species
and Stigmateuthis sp. As they have very delicate and gelationous integuments,
they are found to be completely destroyed.
DISTRIBUTIONAL IMPLICATIONThe catch of sperm whales have been concentrated to the coastal waters of the
Aleutian Is., the Bering Sea and Alaskan Gulf. This is corroborated by Clarke(1956) who described that sperm whales congregate to the neighborhood of theislands in the mid oceans and continental shelves. The distributions of sperm
whales and their foods are illustrated in Figs. 1 and 2 based on the results in 1960
and 1963, respectively.
The male whales occupy the major part of the catch, and very small numberof females were caught as are so for the Antarctic catch of sperm whales. Matthews (1938) suggests the difference in food between the male and fameal is possiblypresent as the males are usually large in size and more powerful in catching preys
by deep sea diving. But no clear difference between the size of food squids intaken
by male and female has been proved. (Matthews, 1938: Clarke, 1956).

T. OKUTANI AND T. NEMOTO

116

0

2J-39

0

5-19

0

J-4

Fig. I. Distribution of squids and fish in the stomachs of sperm whales from the Bering
Sea, 1960. White-Squids, Black-Fish.
1'10''/,

160"

040i

to
j

0

0

J

~i

:_1~-'

E

180'

160'V;

20-39

0

~0-19

0

5-9

0

J-4
J4C/ ·,v

Fig. 2. Distribution of squids and fish in the stomachs of sperm whales from the Bering
Sea and the Alsakan Gulf, 1963. White-Squids, Black-Fish.

FOOD OF SPERM WHALES117

It is evident from the Figs. 1 and 2, squids dominantly occur in the westernpart of the coastal waters around the Aleutian Is. Fish as the food of the whaleare, on the contrary, mostly predominate in the eastern waters along the Alaskan
Gulf and the east Bering Sea. This tendency was also noticed by Ohsumi (personalcommunication, 1956) for the Bering Sea. In 1960, the dominant occurrences ofsquids were observed in the waters around 176 °E longitude and fish are mostly
found in the northern area of the Bering Sea.
The 1963 catch of sperm whales was taken from the Alaskan Gulf where thesperm whales feed on fish in larger quantity than squids. For the foods of sperm
whales in the other parts of the North Pacific Ocean, there are some reports available:
Mizue (1950) described squids and fish as the foods of sperm whales in theadjacent waters to Japan without classifiying them. Betesheve & Akimushkin(1955) described foods of sperm whales from the Kurile waters. The foods speciesof sperm whales in the east Pacific along the American coast were described by Rice
(1963).
TABLE I.

OCCURRENCES OF SQUIDS AND FISH IN THE STOMACHS
OF SPERM WHALES FROM THE NORTHERN PARTOF THE NORTH PACIFIC, 1960 AND 1963
Beiing Sea &Aleutian coast-180°

Bering Sea &Aleutian coast
180°-160°W

1960{ Squids
Fish

240
16

434
178

1963

{Squids
Fish

129
19

116
9

Coast of
Alaskan Gulf
160°W-130°W

45

94

According to Betesheva & Akimushkin (1955) and Sleptozov (1955), the mostimportant species of suqids as the food of sperm whales are Gonatus magister and
Gonatus sp. followed by Gonatus fabricii, Galiteuthis armata, Taonius pavo, Chiroteuthis
veranyi and Meleagrotheuthis seperata. They presented few occurrences of giantsqids, Moroteuthis robustus and Architeuthis Japonica, from the Kurile waters. On theother hand, Moroteuthis robustus occupied 41 % of the total food of sperm whalescaught off America (Rice, 1962), although the materials are rather poor. Gonatopsis
borealis stood the second rank of the foods reported by him.
From the materials treated here, the. following patterns of distributions byspecies are observed:
Type A: Moroteuthis robustus
This was the most important squid in the waters around Aleutian Is. and the occurrences of this species are illustrated in Fig. 3. Moroteuthis robustus was found in
the coastal areas of Alaskan Gulf as far as the Canadian coast. This squid wasreported to be found from the stomachs of sperm whales taken off the west coast of
British Columbia (Pike, 1950: Robbins, Oldham & Geiling, 1937). These obserbation suggest that M. robustus is also common in the California Current area.

118

T. OKUTANI AND T. NEMOTO

There was found no diurnal change in occurrences as is shown in Fig. 5.
Matsushita (1955) stated that the sperm whales in the Antarctic feed on squids inthe early or the late hours of the day when those squids come up to the surface of thesea. Thus, whales need not to dive so deep in the sea to feed on large squids. At
feeding, sperm whales in the Bering Sea may reach at the sea bottom sometimes, assome stones and other sedimentary aliens are found in the stomachs of sperm whalescaught there (Nemoto, & Nasu, 1962). But, the ocean depths are generally not solarge there as in the Antarctic waters.-The coastal waters of the Aleutian Is.
are shallow enough for sperm whales to reach at the bottom, so that Moroteuthis
robustus may be fed by them even in the mid-day at or near the bottom.

0
0
0
0

Type A, l l -,,,,Type E,

5-10
l-4
l-4
j

180'W

re:/~',

l40'W

Fig. 3. Distribution of squids found in the stmaches of sperm whales from the Bering Sea
and the Alaskan Gulf: Type A (Moroteuthis robustus) and Type E (Gonatus magister).

The specimens of M. robustus reported by Betesheva & Akimushkin ( 1955)
were mostly ranging in size from 100 cin to 140 cm in total length including thefoot. The largest one reported by Pike (1950) and Robbins, Oldham and Geiling(1937) measured 250 cm in length. In the present study, the large six specimensof Moroteuthis were found in the stomach of a single sperm whale, and thirty specimens of 100 cm or smaller were found from another sperm whale.
Type B & D:

Gonatopsis borealis makko

The position for the largest specimen (Type B) found together with Moroteuthis
was the west Aleutian waters. Other small specimens could not be identified on theFOOD OF SPERM WHALES

119

occasion of field observations. They were described as type D and were found in
the central part of the Bering Sea and the adjacent waters to the Aleutian Is. This
species was also found in the comparatively high latitudes of the Bering Sea. A
single occurrence was also observed in the coast of Alaskan Gul£'t~' :.

•

0Type B,

1

Type D, JO-

0 ,,
0

,,

1 -4

6

Type C, 1-4

xType G,.IG'',\

Fig. 4. Distribution of squids by type found in the stomachs of sperm whales from theBering Sea and the Alaskan Gulf: Type B (Gonatopsis borealis makko), Type D (thesame), Type C (Mastigoteuthis ( ?), Stigmateuthis, Galiteuthis and Taonius), and Type G.
(Gonatus fabricii).

Type C: Mastigoteuthis? sp., Stigmateuthis sp., Galiteuthis armata, and Taonius pavo
Above four species are described as type C on the field note although the shapeand other taxonomical criteria are different. These species were mainly found in
the central part of the Bering Sea as shown in Fig. 4. From the occurrences offragmental integument in the stomachs of sperm whales, these squids were suspected
to be distributed mostly the central part of the Bering Sea.
Type E : Gonatus magister
This species was observed in the coastal waters of Aleutian Is. and Alaskan Gulf
as in Fig. 3. This species is considered to be very common in the north-eastern
Pacific.
Type G: Gonatus fabricii
Gonatus fabricii was recorded as the main food of the toothed whale (bottlenose) in the Atlantic (Hjort & Ruud, 1929). Betesheva & Akimushkin (1955) des-T. OKUTANI AND T. NEMOTO

120

cribed considerable numbers of occurrences of this species from the adjacent waters
to Kurile Is. Pike (1950) also found this species from sperm whales taken off the
Birtish Columbia coast. In the present survey, only a single large specimen was
found from the Alaskan Gulf.
Type D55Type A

5

10

5

6

8

10

12

14

18

Time of the Day

Fig. 5. Occurrences of Type A (Moroteuthis robustus) and Type D (Gonatopsis borealis
makko) in the stomachs of sperm whales from the northern part of the North Pacific byhours of a day.

It is interesting to note that none of Myopsida, mostly coastal and benthonicforms, was found in the stomachs of sperm whales. Myopsida is generally tropic
and temperate water forms and they are naturaly not distributed in the waters ofhigh latitudes.
SUMMARY

The squids specimens found in the stomach of sperm whales taken from the northernpart of the North Pacific (Bering Sea and Alaskan Gulf) were examined.
1. Moroteuthis robustus, Mastigoteuthis? sp., Stigmateuthis sp., Galiteuthis armaa, Taonius
pavo, Gonatus magister, Gonatus fabricii, and a new subspecies, Gonatopsis borealis makko,
were found in the stomachs of sperm whales as their foods.
2. The distributions and occurrences of those squids are discussed.
Moroteuthis robustus, which is considered to be the most important squid for the foodof sperm whales, is common in the adjacent waters to Aleutian Is. Gonatopsis
borealis makko is also common not only in the central part of the Bering Sea, but also
in the northern part. Gonatus magister is found along Aleutian Is. and Alaskan Gulf,
while G. fabricii is found in the Alaskan Gulf. Cranchiids are discovered from hecentral part of the Bering Sea.
3. The distribution of those food squids is considered to be concentrated to thecentral part of the Bering Sea along the chain of Aleutian Is. This coincides withthe major distributional area of sperm whales. On the other hand, fish as the foodof sperm whales, are mainly found in the waters of the northern part of the Bering
Sea and Alaskan Gulf.

FOOD OF SPERM WHALES121

REFERENCESAKIMUSHKIN, I.I. (1955). The feeding of the Cachalot. C.R. Acad. Sci., U.S.S.R. IOI (6): 1139-40.
BERRY, S.S. (1912). A review of the cephalopods of western North America. Bull. Bur. Fisher. 30,
Doc. 761: 267-336. 25pls.
- - (1913). Notes on some west American cephalopods. Proc. Acad. Nat. Sci. Phil. 65: 72-77.
BETESHEVA, E.I. & AKIUMSHKNI, I.I. (1955). Food of the sperm whale (P. catodon) in the Kurile Islands.
Trans. Oceanogr. Inst., Moscow 18: 86-94.
CLARKE, R. (1955). A giant squid swallowed by a sperm whale. Norsk Hvalfangst-Tid. 44(10): 589-93.
- - (1956). Sperm whales of the Azores. Discovery Rep., 28: 237-98. Ip!.
CLARKE, M.R. (1962). Stomach contents of sperm whales caught off Madeira. Norsk Hvalfangst-Tid.,
51(5): 173-91.
HEEZEN, B.C. (1957). Whales entangled in deep sea cable. Deep Sea Res., 4: 105-15.
HJORT, J. & RUND, J.T. (1929). Whaling and fishing in the North Atlantic. Rapp. Proc. Vverb. Re. 56:
5-123.
MATTHEWS, L. H. (1938). The sperm whale (Physeter catodon). Discovery Rep. 17: 93-168. 9 pls.
MATSUSHITA, T. (1955). Daily rhythmic activity of the sperm whales in Antarctic Ocean. Bull. Japan. Soc.
Sci. Fish., 20(9) : 770-3.
MIZUE, K. (1950). Food of whales (in the Adjacent waters of Japan.) Sci. Rep. Whales Res. Inst., 5:81-90.
NEMOTO, T. & NAsu, K. (1962). Stones and other aliens in the stomachs of sperm whales in the Bering Sea.
Sci. Rep. Whales Res. Inst., 17: 83-91.
RICE, D.W. (1963). Progress report on biological studies of the larger cetacea in the waters off California.
Norsk Hvalfangst-Tid., 52(7): 181-7.
PIKE, G.C. (1950). Stomach contents of whales canght off the coast of British Columbia. Prag. Rep. Paci.fie
Cosat St. 83: 27-8.
ROBBINS, L.L., F.K. OLDHAM, & E.M.K. GEILING (1937). The stomach contents of sperm whales canght
off the west coast of British Columbia. Rep. British Columbia Museum 1937: 10-20, Ip!.
SASAKI, M. (1923). On a new eight-armed squid from Hokkaido, Gonatopsis borealis n. sp. Ann. :(,ool. Jap.
10: 203-207- - (1929). A monograph of the dibranchate cephalopods of the Japanese and adjacent waters. J. Coll.
Agr., Hokkaido Imp. Univ., 20: 1-357. 30pls.
SLEPTOzov, M.M. (1955). On the biology of cephalopod molluscs of the far-eastern seas and the northwestern Pacific. Trans. Ocenolog. Inst., Moscow, 18: 69-77.

122

T. OKUTANI AND T. NEMOTO

EXPLANATION OF THE PLATESPLATE I
Fig. 1. Moroteuthis robustus (Verrill), dorsal mantle length 700 mm.
la. Tentacular club of another specimen.
PLATE II
Fig. 2. Gonatus (s.s.) fabricii (Lichtenstein), dorsal mantle length 300 mm.
Fig. 3. Stigmateuthis sp. (separata Sasaki?), dorsal mantle length 100 mm.
PLATE III
Fig. 4. Gonatus (Ben:_yteuthis) magister Berry, dorsal mantle length 250 mm.
Fig. 4a. Tentacular club of the same specimen.
PLATE IV
Fig. 5. Gonatopsis borealis makko, n. subsp., dorsal mantle length 350 mm. (Holotype)Fig. 5a. Left lateral arms of the same specimen.
Fig. 5b. A funnel locking cartilage.
Fig. 5c. Nuchal locking cartilage.
PLATE V
Fig. 6. Taonius pavo (Lesueur), anterior part of the mantle torn out, dorsal mantle length 250+x mm.
Fig. 7. An unidentified squid, probably Mastigoteuthis sp.

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COMPARISON OF MATURITY AND ACCUMULATION RATEOF CORPORA ALBICANTIA BETWEEN THE LEFT
AND RIGHT OVARIES IN CETACEASEIJI OHSUMIINTRODUCTION

On the activity of ovaries in animals, there are some species of which one side ofovary is not functional, and there are other species of which both ovaries arefunctional. And the latter species are separated into two kinds, one is a animal ofwhich both ovaries are active equally, the other one is a animal of which one
ovary is more active than the other. Limitting to mammals, Orinithorhynchus
paradoxus of Monotremata is functional in the left ovary only and the embryos arealways found in the left uterus (Flynn & Hill, 1938) In some vespertilionid bats,
only one ovary, usually the right, is functional; in others, both appear to be functional, but pregnancies are found only in the right horn of uterus (Asdell, 1946).
In domestic cattle (Bos taurus), the right ovary tends to produce more ovulations
than the left. A corpus luteum count showed 60.2% in the right ovary (Reece& Turner, 1938). According to Henning (1939), the right ovary-functions act
more frequently than the left, since ovulations have been found in that ovary in
58.58±1.85 % of cases. The other hand, in domestic pig (Sus scrofa), the leftovary appears to be slightly more active than the right. Warwick (1926) reported
that 55.3% of ovulation were shed from the left ovary. The left ovary of horse(Eqnus caballus) functions more frequently than the right. In a series of 185 ovulations 61 % were from the left (Andrews & McKenzie, 1941). But in many animal,
there is practically little or no difference in the relative activity of the two ovaries(Guinea pig, Gavia porcellus; domestic rabit, Oryctologus cuniculus; Woodchuck,
Marmota monax; rat, Rattus rattus; Bengal rhesus monkey, Macaca mulatta etc.),
according to a book by Asdell (1946).
Concerning the difference of ovulation or pregnancy between the left and rightovaries in CETACEA, Sleptsov (1940) reported that in only 17% of 635 pregnant
dolphin and beluga embryos were found in he right horn of uterus. And Slijper(1958) described that 'In all ODONTOCETES so far investigated, the fertilized
ovum was almost invariably attached to the distended left horn of the uterus, while
the smaller right horn was found to contain a part of the allantois. In MYSTICETES, on the other hand, the foetus may develope in eigher horn.' In
CETACEA, a ovum ovulated from one side of ovary, usually attached to the sameside of horn of uterus (Slijper, 1949), therefore we can estimate by the horn inwhich foetus is, from which ovary ovulation occured. And fortunately in CETACEA, all ovulations are recorded permanently in the ovaries as corpora albicantia.
So, we can determine the number of ovulation by the time of investigation by
123

124

S. OHSUMI

counting corpora lutea and albicantia in each ovary. Laws (1961) reported thatcombining both corpora albicantia and corpora lutea, of 724 fin whale (Balaenoptera physalus) corpora, 52.4±3.72% were in right ovary and of 454 blue whale(Balaenoptera musculus) corpora, 52.4±4.68% were in right ovary, and he estimatedpossibility that there is a slight prevalence of right side in both species. Sergeant(1962) described that from the distribution of corpora lutea and albicantia in
42 ovary pairs of the pilot whale (Globicephala melaena) it was found that 70 % of
ovulations on average took place from the left ovary with wide individual variation
in incidence of scars between two ovaries.
Reviewing the above reports, they seems to investigate the comparison ofovulation between the left and right ovaries including all age groups, and it seems
that there is no report on the variation of accumulation rate of corpora in one sideof ovary according to the increment of age. I studied the number of corpora lutea
and albicantia between the left and right ovaries in 23 species of CETACEA, forthe purpose of caparison of maturity and variation of corpora accumulation rate
between the left and right ovaries. And then taxonomic consideration was givenon the typing of relative corpora accumulation and interrelationship of the types.
I wish to express my sincere thanks to Dr. D. E. Sergeant of the Fisheries
Research Board of Canada, Dr. M. Nakajima of the Enosima Marineland, Drs.
M. Nishiwaki and T. Nemoto and Mr. T. Ichihara of our Institute, who kindly gave
their valuable data for my study. Present paper would not be completed, ifl did'nt
get their valuable materials. Especially Drs. Sergeant and Nishiwaki gave me
many data and many suggestions. I am indebted to Professor H. Hosokawa ofDepartment of Anatomy, School of Medicine, University of Tokyo, AssistantProfessor T. Hibiya of Department of Fisheries, School of Agriculture, Universityof Tokyo and Dr. H. Omura, Director of our Institute for their helpful commenton my draft.
MATERIALSpecies, locality, number of samples, and investigater used in this study are shownin Table I. To my regret, I collected the data on only 23 species, and they are notcontained in all Genera of CETACEA.
Ovaries are convinced of the left and right, and number of corpora lutea andalbicantia in each ovary are counted as accurate as possible. Mature ovary isdefined as that in which more than one corpus luteum or albicans is accumulated,and I did not use an individual of which both ovaries are immature as the material
for this paper.
As mentioned in above chapter, in CETACEA, corpus albicans is considered
to be not absorbed. Therefore, the ovulations are recorded permanently as corpus albicans. Although there are individual variation in the ovulation rate,number ofcorpora albicantia is related to age in average. Then, the comparison of maturity
and accumulation rate of corpora between the left and right ovaries are able to be
examined by the comparison of number of corpora in the left or right ovary to theCORPORA ACCUMULATION IN CETACEA

125

total number of corpora in both ovaries.
Frequencies of number of corpora in the left ovary in each class of number ofcorpora in both ovaries are tablated for eight species as shown in Appendix-Tables.
Frequency of number of corpora in the right ovary is calculated easily from the table.
From an Appendix-Table, a figure which shows a process ofrelative accumulation of
corpora in the left and right ovaries is drawn for each species. On the species of whichsamples are small, indicidual data are plotted in the figure, and estimated mean
curves of accumulation or corpora are drawn in the left and right ovary. Other
species of which samples are collected more than 40, I calculated average numberof corpora in the left or right ovary in adequate class of total number of corpora,and connected each average values by straight line.
TABLE 1.

Species
Balaenoptera musculus--physalus--edeni--borealis--acutorostrata
Megaptera novaeangliae
Eubalaena glacialis
Physeter catodon
Kogia sp.
Berardius bairdii
Z,iphius cavirostris
Delphinapterus leucus
Phocaenoides dalli
Grampus griseus
Globiceplala melaena--scammoni
Orcinus area
Feresa attenuata
Lagenorhynchus obliquidens
Tursiops truncatus*
Delphinus delphis
Stenella attenuata--caeruleoalba

LIST OF SPECIES AND NUMBER OF INDIVIDUALSEXAMINED IN THIS PAPER
Locality
N. Pacific
N. PacificJapan
Antarctic
Japan
N. P. and Ant.
N. P. and Ant.
Japan
Japan
Japan
Japan and N.P.
Hudson Bay
Japan
Japan
Newfoundland
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Japan

No. ofspecimen

57
297
54
80
2
100
3
298
13
3
16
5
2
173
7
4
1
26
6
3
333

Investigator
S. 0HSUMI
S. 0HSUMI
S. 0HSUMI
S. 0HSUMI
T. lcHIHARA
S. 0HSUMI
T. NEMOTO and MATTHEWS (1938)
S. 0HSUMI
S. 0HSUMI
S. 0HSUMI
S. 0HSUMI and KENYON (1961)
D. E. SERGEANT
S. 0HSUMI
M. NAKAJIMA
D. E. SERGEANT
S. 0HSUMI
S. 0HSUMI
M. NrsHIWAKI and S. 0HSUMI
M. NAKAJIMA
M. NISHIWAKI, M. NAKAJIMA and S. 0HSUMI
M. NISHIWAKI, and M. NAKAJIMA
M. NAKAJIMA
M. NrsHIWAKI and S. 0HSUMI* More taxonomic studies are needed on this species.
RESULTS

Balaenoptera musculus
Slijper (1949) reported 59% of pregnancies came from the left ovary inthe blue whale, and Laws (1961) described that of 454 corpora, 52.4±4.86%
were in right ovary. According to my material, total corpora in the left ovaries
are 47.4% of total number of corpora in both ovaries.

126

S. OHSUMIAs shown in Appendix-Table 1, each ovary attains to maturity by the time of
two ovulations in each other side of ovary. And as shown in Fig. 1, accumulation
rates of corpora are almost piled up each other in both sides of ovaries.
Considering above phenomenon, I conclude that in Balaenoptera musculus theleft and right ovaries attain at maturity in the same time and ovulation occuresalternately from the left and right ovary in average.

Balaenoptera physalus
Many materials are obtained for this examination from the northern part of
the North Pacific. In total individuals, 51.9% of corpora accumulated in the leftovary. Slijper (1949) reported the percentage of existence of corpus luteum of
pregnancy on 17, fin whales and the result was 65% of fin whales the corpus luteum
was in the right ovary. However, Laws (1961) describes that combining the corpora
lutea and albicantia, of 724 fin whale corpora, 52.4±3.72% were in the rightovary, and he states it seems possible that there is a slight prevalence of the rightside in the fin and blue whale. My result is that the left side is silghtly more, but it
is included into the standard deviation by Laws ( 1961).
Appendix-Table 4 shows the distribution of number of corpora in the leftovary in each class of number of corpora in both ovaries. There is individual
variation, for instance, in the 8 corpora class in both ovaries, the number of corpora
in the left ovary distribute from 2 to 7, but the average is 4.6. That is to say, theaverage of corpora in the right ovary is 3.4. The left ovary attaines to maturityby the time when the other side of ovary accumulated 4 corpora, on the other hand,right ovary attaines to maturity by the time when 6 corpora accumulate in theleft ovary.
As shown in Fig. 1, the maturity and the relative accumulation rate of corpora
are almost the same between the left and right ovary in average.
Balaenoptera edeni
Materials were collected from Japanese coast. In total of 54 whales, 48. 7 %of corpora accumulate in the left ovary. Each ovary attaines to maturity by 3
corpora accumulate in each other side of ovary. And as shown in Fig. 1, the maturity
and relative accumulation rate of corpora are seemed in average to be the same
between the left and right ovary, although there is some individual variation.
Balaenoptea borealis
Materials were obtained from the Antarctic Areas IV, V, and VI. 49.7% ofcorpora accumulate in the left ovary. The individual variation is seemed not tobe so wide as Balaenoptera physalus. The left ovary attaines to maturity by 5 corpora
accumulate in the right ovary, on the other hand, the right ovary attaines to maturiyby 4 corpora accumulate in the left ovary. The average accumulation of corpora
in each ovary is shown in Fig. 2, and maturity and corpora accumuation is almost
the same each other between the left and right ovary.

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Fig. 1. Relative accumulation of corpora lutea
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Balaenoptera musculus, B. physalus, and B. edeni.
Open circles and broken line: Average values
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Thin line A: Ovulation occures from one side
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Balaenoptera acutorostrata
I have only two materials. But as shown in Fig. 2, the maturity and corpora
accumulation is seemed to show the same type as the above species.
Megaptera novaeangliae
I used the ovaries materials from the Antarctic and the North Pacific. In
the total of 100 individuals, 53.4% of corpora accumulate in the left ovary. The
left ovary attaines to maturity by 5 corpora in the right ovary, and the right ovary
attaines to maturity by 4 corpora in the left ovary. But in average, as shown in
Fig. 2, the left and right ovaries are almost the same in the maturity and relative
accumulation of corpora.
Eubalaena glacialis
By 1963, 11 right whales were killed by Japan in the North Pacific on thespecial permission of scientific research. Among them female whales are 4. The
ovaries of one of the females were entirely immature and no follicle was seen on
their surface (Omura, 1958). The ovaries of the secon~ female are seemed to be
prepuberal, because one follicle of which diametre is 3.8 cm is seen in the left ovary
but there is not difference in the size between the both ovaries (Left: 30.0 x 12.0
cm, Right: 31.0 x 11.5 cm), and they are considered to be almost the same stage
from the observation by naked eye. Other two females are both pregnant. One
individual has only one corpus luteum in the right ovary and there is no corpus
albicans in both ovaries. The other individual has one corpus luteum in the leftovary and two corpora albicantia in the right ovary.
Matthews (1938) reported that No. 1019 right whale in the southern hemisphere
had one corpus luteum and 6 corpora albicantia in one side of ovary, and has 6
corpora albicantia in the other side of ovary.
Although I have small data on this species, and it is difficult to conclude, I
estimate that maurity and relative corpora accumulation are the same in average
between the both ovaries like the above 6 species.
Pfryseter catodon
Materials were obtained in the coast of Japan. In the total 298 whales, 51.6%
of corpora accumulate in the left ovaries. From this point, we can estimate that
ovulation occures equally from the both sides of ovaries. Appendix-Table 6 shows
the distribution of corpora in the left ovary. Each ovary attaines to maturity by
5 coprora accumulate in the other side of ovaries. Deviation of corpora is not so
wide even ifin the old stages. As shown in Fig. 3, the maturity and relative accumulation rate of corpora is seemed to be equall in the both side of ovaries like as
MYSTACOCETI.
Kogia sp.
A Kogia was caught in a coast of Japan. Dr. M. Nakajima investigated andcollected many materials on the species, but it is not yet identified. This individualhas 6 corpora albicantia in the left ovary and 7 corpora albicantia in the right ovary.

134

S. OHSUMI

I have only one material, but I estimate that this species will be the same tendency
as Physeter catodon.

Berardius bairdii
13 individuals were examined the corpoa counts separating the left and rightovaries. 47 corpora (47.5%) accumulated in the left ovary. Although the materials are not so many, we can estimate the maturity and relative accumulation
will be the same between the both ovaries.
Ziphius cavirostris
I have only two materials from the coast of Japan. And Kenyon (1961)
describes that one corpus albicans accumulated in each ovary of a female. Consideraing the above data and Fig. 3, I estimate that the tendency of maturity andcorpora accumulation will be the same as Physeter.
Delphinapterus leucus
In the total corpora, 68.9-70.8% of corpora accumulate in the left ovary, andapparently the ovulations from the left ovary exceed those from the right side.
As shown in Fig. 4, there is an individual of which right ovary is still immature when 5 corpora accumulate in the left ovary. On the contrary, there is anindividual of which left ovary is still immature when 3 corpora accumulate in theright ovary. The right ovary in average attaines to maturity later than the leftovary, but the deviation is not so much. Relative accumulation rate in the rightovary is somewhat lower than that in the left ovary in younger stage, but the deviation of corpora accumulation between the both ovaries seems to become shorter
gradually.
Phocaenoides dalli
There are 5 paires of ovaries taken in the coast of Japan.
Unfortunately they are all relatively young stage (the oldest individual has
only 4 corpora in the both ovaries), and data are given from only 5 individuals.
Therefore, conclusion will be not introduced, but all corpora accumulate from theleft ovary. Right ovary is still immature, when 4 corpora accumulate in the leftovary. And the size of ovary is smaller in the right ovary than in the left ovary.
Grampus griseus
One individual has one corpus albicans in the left ovary and one corp. luteum
and two corp. albicantia in the right ovary, whereas the other individual has one
corp. luteum and 7 corp. albicantia in the left ovary and one corp. albicans in theright ovary. Then, 69.2% of corpora accumulate in the left ovary.
Globicephala melaena
In total corpora, 65.5% of corpora accumulate in the left ovary, therefore
ovulation occures more frequently from the left ovary than from the right ovary.
Left ovary attaines to maturity by the time when 9 corpora accumulate inCORPORA ACCUMULATION IN CETACEA

135

the right ovary, on the contrary, there is an individual of which right ovary is immature when 9 corpora accumulate in the left overy. As shown in Appendix-Table
7. there are many individuals of which left ovary is mature but the right ovaryis still immature.
Fig. 5 shows the average corpora in the left and right ovaries in each total corpora class. From this figure relative corpora accumulation in the left ovary exceeds that in the right ovary.

Globicephala scammoni
I have only 7 data on the corpora count on this species. Considering Fig.
5, the relative accumulation curve is similar with that of Globicephala melaena.
58.9% of corpora accumulate in the left ovary.
Orcinus orca
I have only one corpora count on this species. One corpus luteum and 3
corpora albicantia accumulate in the left ovary and one corp. albicans exists in
the right ovary. Assuming from only this specimen, this species is included into
the similar type as Globicephala.
Feresa attenuata
There is an individual of which right ovary is still immature when 10 corpora
accumulate in the left ovary. However, in total corpora, 82.6% of corpora accumulate in the left ovary. Although there are scanty of data, the relative
corpora accumulation will be similar with that of Globicephala.
Lagenorhynchus obliquidens
I have only one material. This individual has two corpora albicantia in theleft ovary, but the right ovary is still immature.
Tursiops truncatus
Zoological name of this species caught in the coast of Japan must be studied
further, but I used it as T. truncatus according to Ogawa (1938).
82.8% of corpora accumulate in the left ovary, and all left ovaries are maturein the materials, but mature right ovary appears from the time when 3 corpora
accumulate in the left ovary. And there is an individual of which right ovary isimmature when 10 corpora accumulate in the left ovary. From Fig. 5, it will
be assumed that the left ovary attaines at maturity first, and in younger stage
ovulation occures in average from only the left ovary. Then, after attainment oflater maturity of the right ovary, relative corpora accumulation rate of the rightovary will be larger than the left ovary.
Delphinus delphis
Of total individual, 88.5% corpora accumulate in the left ovary. In 5 individuals of total 11 corpora only the left ovaries are mature. The other in-

136

S. OHSUMI

dividual has 15 corpora albicantia in the left ovary and 6 corpora albicantia in
the right ovary. From Fig. 6, it will be considered that the right ovary attaines tomaturity by the time when about 10 corpora accumulate in the left ovary, after thenrelative accumulation rate will be more in the right ovary than in the left ovary.

Stenella attenuata
I have 3 corpora counts taken and kept in Japan.

The data are scant and got
from young animals, but all corpora accumulate in only the left ovary.

Stenella caeruleoalba
As many as 333 materials are obtained from the coast of Ja pan as shown inAppendix-Table 8.
There is no individual of which only left ovary is immature. On the other
hand, there are many individuals of which right ovary is still immature by thetime when 14 corpora accumulate in the left ovary. 93.4% of corpora accumulate
in the left ovary in total corpora.
In average, ovarian maturity occures from the left ovary first, and until thetime when about 9 corpora accumulate in the left ovary, the right ovary is still
immature. But the right ovary is not immature for life. After the maturity of
the right ovary, relative corpora-accumulation rate becomes more in the right ovary
than in the left ovary.
TYPES OF CORPORA ACCUMULATION IN BOTH SIDES OF OVARIES
Considering the relative corpora-accumulation curves, we can classify them into
three kinds of types for 23 kinds of Cetacean species.
Type I : Left and right ovaries attaines to maturity almost the same time in average,
and there is no difference in the relative accumulation rate of cropora between theleft and right ovary. Following 10 species are considered to be included into thiskind of type: Balaenoptera musculus, B. physalus, B. edeni, B. borealis, B. acutorostrata,
Magaptera novaeangliae, Eubalaena glacialis, Physeter catodon, Berardius bairdii, andZiphius cavirostris. I have only one Kogia sp. of which ovaries are examined. So,
it is dangerous to conclude, but I consider that this species is also included in Type I.
Type II : Maturity ofright ovary is attained somewhat later than the left. Relative
accumulation rate of corpora in the left ovary is more than that in the right during
young stage, but the difference between the left and right ovaries is not so much.
In older stage, relative accumulation rate of corpora in right ovary exceeds thatof the left ovary. Following 4 species are considered to be included into Type II :Delphinapterus leucus, Globicephala melaena, G. scammoni and Feresa attenuata.
Owing to the deficiency of samples, I could not determine the type of cropora
accumulation for Grampus griseus and Orcinus orca. But I presumably consider they
are also included into this kind of type.
Type III : Remarkable difference of corpora-accumulation rate occures between
the left and right ovaries. Left ovary attaines to maturity earlier than the right.
And for relatively long time, ovulation occures from only left ovary. But after

137

CORPORA ACCUMULATION IN CETACEA

attainment of maturity of right ovary, the ovulation from right ovary becomes
more frequently than the left. Following 5 species are considered to be included
into this type: Phocaenoides dalli, Tursiops truncatus, Delphinus delphis, Stenella attenuata and S. caeruleoalba.
On Lagenorhuchs obliquidens, I have only one material, so I hesitate to conclude
that this species is included in Type III, but I think it is possible.
2

>Q_ ~

0

0u 0~
~_c

0

u

~

0

QJ

QJ

Type

I

A

Type

B

II

A

Type

IlI

A

B

...D

E .':

:0

z

Number of corpora in both ovaries

Fig. 7. Schematic figures of the three kinds of types of relative corpora accumulation in
the left and right ovaries of cetacea.
Broad solid line: Left ovary, Broad broken line: Right ovary, A-line: Ovulation
occures from only one side of ovaries, B-line: Both ovaries attains to sexual maturity
in the same time and ovulation occures equally from both sides of ovaries.

Table 2 shows the accumulation type and the per cent of number of ovulations(number of corpora lutea and albicantia) from the left ovaries to total ovulations
from both ovaries for 23 species ofCETACEA examined. As shown in the previous
figures, such percents must be variable according to the variation of age distribution,
especially in Types II and III. For instance, in Stenella caeruleoalba, if we collect
only young animals, the percentage of ovulation in the left ovary is near 100%.
On the contrary, if we collect only older animals, the percentage decrines remarkably. Therefore, I want to emphasize on this phenomenon. Previous workers
reported percentage of the existance of fetuses in left or right uterine cornu (Sleptsov,
1940; Slijper, 1949 etc.) or percentage of number of corpora in left or right (Laws,
1961 ; Sergeant, 1962). But I think they did not consider the above phenomenon.
Nevertheless, as shown in Table 2, the percentages of total ovulation from leftovary to that from both ovaries are seemed to have relation with the types of corpora
accumulation. That is to say, it is as a matter of course, the percentages of ovulation from left ovary are distributed between 45 and 55% in 11 species of Type I.
They are 52.0% in average. In Type II, percentages of ovulation from the leftovary are distributed between 58 and 83 % for 6 species. They are apparently
separate from the values of Type I. And in average 65.9% of ovulations occuresfrom the left ovaries on the 6 species.
Type-III species have much percentage of ovulation from the left ovaries. The
range of the ratios is between 82and100% and the average is calculated as 92.7%
for the 6 species.

S. OHSUMI138

I consider that if we have only material on the distribution of corpora in left
and right ovary or the percentage of foetal existence in the left or right uterine
cornu on one species, we can estimate briefly in what kind of corpora-accumulation type the animal is classified.
TABLE 2.

TYPES OF CORPORA ACCUMULATION AND TOTALNUMBER OF CORPORA
No. of total corpora

Species
Balaenoptera musculus-physalus-edeni-borealis-acutorostrata
JY!egaptera nouaeangliae
Eubalaena glacialis
Physeter catodon
Kogia sp.
Berardius bairdi i:(,iphius cauirostris
Delphinapterus leucus
Phocaenoides dalli
Grampus griseus
Globicephala melaena--scammoni
Orcinus orca
Feresa attenuata
Lagenorhynchus obliquidens
Tursiops truncatus
Delphinus delphis
Stenella attenuata-caeruleoalba

No. ofspecimens

No.of
Type

57
297
54
80
2
100
3
298

I

13
3
16
5
2
173
7
4
26
6
3
333

I

I
I?

II
III
II?
II
II
II?
II
III?
III
III
III
III

...--------...

Left

Right

LOI*
/0

755
1056
147
350
19
198
7-8
909
6
47
7
51
10
9
607
33
4
19
2
101
46
7
1750

172
981
155
354
16
173
9-10
853
7
52
6
21-23
0
4
320
33

47.4
51.9
48.7
49.7
59.3
53.4
41.2-47. I
51.6
46.2
47.5
53.8
68.9-70.8
100.0
69.2
65.5
58.9
80.0
82.6
100.0
82.8
88.5
100.0
93.4

4
0
21
6
0
123

* Per cent of number of corpora in the left ovary to total corpora in both ovaries.
TAXONOMIC CONSIDERATION ON THE TYPES OF RELATIVECORPORA ACCUMULATION IN CETACEA

In the previous chaper, I classified the relative corpora-accumulation curves into
three kinds of types. ·Among 23 species examined, there are only three genera in which more than
two species are included (Balaenoptera, Globicephala and Stenella). But we can findthat the sepcies included in same genus show the same type of corpora accumulation.
Then, I arrange genera of living CETACEA in Table 3. Types of corpora
accumulation and the combination of genera by Flower & Lydekker (1891), Winge(1918), Fraser (1938), Simpson (1945) and Nishiwaki (1963, 1964) are also
recorded in this table.
To my regret, I could not examine the types of corpora accumulation on allMesopfodon._)'ot<1lia

Stenella

Ste''°

Ill

Ill

Ill

Tursiops

Ill?

Delphinus

Lagenorhynchus

Lissodelphis

Feresa

II

II

II?

GlobicephalaOrdnusPseudorca

II?

Jll

Grampus

Orcaella

Phocaenoides

Plwcoena

Neophocaena

Delphinapterus

MonodonPlatanista

lnia

Lipotes

Pontopoia

II

I

Ziphius1·asmacet11s

I

GROUP B

GHOUi' A

ZIPllllNAE

DELl'll!NIDAE)~"'"""""

l··"~""'"'

BAl-AENil)AE

FLOwlm & LYOl:.'l\h'.l::R (1891)l } l'llYSETERlNAE
I?

IJerardt'us

lfyperoodon

Kogia

Physeter

Balaena

E11balaena

Neobalaena

I

I

Rhachianeelus

I

Megaptera'1'ypcBalaenoptcra

Genusz;tl'l!lI

DoLl'll<N<

Jl} L•GENOR«YNC!UGLOBICil'lTl:iS} PuocAENAo} MoNoOONTESf

1\Hmoooo•,.)ZtPHllNI} P11YsETi>REs-P11Ys1rnm1N1} BALAONINI} BALAENOPTERINIWIN<Jh (i 918)

ZIPlllIUAE} l'llYSE'i'El\iD,\E} BAL'"""""I

DELPJHNIDAE)

I

Dm,rmNINAE} DELPHINt\PTERlNAE)""'"~--· )'"'""""'

P11~·s1.rnm1DAE)··""'"

RllACHIA:-.ECTIDAE. } ilALAENOPTERlllAE

F1t.\s1m (1938)

B,,L,\E~IOAE

DELl'lJl:-.:IUAE)'"'"""J)I, lJELPlllNOIDAE} P110CA0NIDA0) !\.loNODONTWAE

PLATANISTIN/\I~

l:"UN"1.E} Sn.-..:00ELP111s

KOGll:"'AEl'IIY:>ETl::RJ:-.:A,E \ PHYSE.TER\llAE}

H11AClllA!\ECTIOAE} B.\LAENOPTERIUi\E

S1:-.m;:o:-. (1945)

OEt.PlilNOJUAEl'LAT"IS'flNOlDAEl'LAT,,NIST!OAE·l
J

11 llYSETEHAIUAE)) DELPHINIDAE

JG~=~~GRAMPIUAE

OncAELLlDAE

l'llOCAEN!OAE

J} MONODONTIDAE)•u"'"'" "')'"""..

Koo11DAE

P11YSlffEitlOAE

N1::;mwaK1 (1963-M)

TABLE 3. TYPES OF CORPORA ACCUMULATION AND THE CONBINATION OF GENERA IN LIVING CETACEABY FIVE AUTHORS

~

""ta

,...

>
Q
>

g

~
z.....

~
.....

~t'"

8

>
>
0

~

0

'"d

0

140

S. OHSUMI

living genera. Especially there is no material on RHACHIANECTIDAE and
PLATANISTITIDAE. Now, three genera belonged to MYSTICETI are all included into Type I, and I guess all species of MYSTICETI has Type I corpora
accumulation. In other words, we cannot divide MYSTICETI more than one
group by only the corpora-acumulation curve.
On the contrary, ODONTOCETI are able to be divided at least three types
by the corpora accumulation. Physeter, Kogia, Berardius and Ziphius are included
into Type I. And Slijper (1958)'s discription must be added that in ODONTOCETI, there are some species of which foetus may develope in either horn. A.g:
the way, recently many authors use the same the classification as Fraser (1938),
that is, Physeter and Kogia are classified into PHYSETERIDAE and Berardius,
Hyperoodon, Ziphius, Tasmacetus and Mesoplodon are classified into another family of
ZIPHIIDAE. But Flower & Lydekker (1891) and Winge (1918) recognized they
are belonged to subfamily of PHYSETERIDAE. And Simpson (1945) established Superfamily PHYSETEROIDEA combining PHYSETERIDAE and ZIPHIIDAE. The phenomena in corpora accumulation will support the taxonomic
interrelationship between PHYSETERIDAE and ZIPHIIDAE.
I cannot show the type of corpora accumulation for PLATANISTIDAE.
Abel (1913) made special researches on the fossil CETACEA, and he tried todetermine their position to recent forms. According his genealogical tree, PLATANISTIDAE is included into SQUALOCETI with PHYSETERIDAE and
ZIPHIIDAE. But Slijper (1936) shows that from primitive SQUALODONTIDAE
separate four branchs of ODONTOCETI, and one of branches becomes to PLATANISTIDAE and PHYSETERIDAE. ZIPHIIDAE become from the second
branch and DELPHINIDAE from the third branch. It is very interesting taxonomically that whether corpora accumulation shows Type I or the fourth typein PLATANISTIDAE.
Superfamily DELPHINOIDEA classified by Simpson (1945) and family
DELPHINIDAE classified by Flower & Lydekker (1891), Winge (1918) andFraser ( 1938) etc. does not show Type I. From this point of view, we will understand that so called DELPHINIDAE can be separated phylogenically from MISTICETI and PHYSETEROIDEA.
However, there are at least two types of species in DELPHINOIDEA by
the examination on the corpora accumulation rate. That is to say, Delphinapterus,
Grampus, Globicephala, Orcinus, and Feresa show Type II, on the contrary, Phocaenoides, Lagenorhynchus Tursiops, Delphinus and Stenella are considered to be included
into Type III. Flower & Lydekker (1891) separated DELPHINIDAE into Groups
A and B. The species included in Group B show Type III, but in Group A
there are two types of corpora accumulation. Winge (1918) describes that
DELPHINIDAE is divided into five subfamily ; MoNODONTES, PHOCAENAE,
GLOBICIPITES, LAGENORHYNCHI and DELPHINI, This classification is not contradictory to my result. Fraser (1938)'s classification of subfamily DELPHININAE
which is widely used today is considered to be too large as Nishiwaki (1963)
reported. Slijper (1936) and Simpson (1945) divided DELEPHININAE by Fraser

CORPORA ACCUMULATION IN CETACEA

141(1938) into two families PHOCAENIDAE and DELPHINIDAE but their
DELPHINIDAE must be divided at least two kinds from the view point of mytyping of corpora accumulation. Recently Nishiwaki (1963, 1964) compared bodylengths, number of vertebrae, fused bone in cervical vertebrae, shape of skull,number maxillary teeth and length of rostrum for 12 genera of ODONTOCETI,and he separated living ODONTOSETI into 10 families as shown in Table 3.
I have no data on the ovaries count for Orcaella, Noephocaena, Phocaena Pseudorcaand Lissodelphis and I cannot conclude the typing of corpora accumualtion for
Grampus. Excluding these 7 genera, the typing of corpora accumualtion agrees
well with Nishiwaki's description. And on the standing point of only corpora accumulation, MONODONTIDAE and GLOBICEPHALIDAE is taxonomicallynear each other, because they show Type II of corpora accumulation, the other
hand, PHOCAENIDAE (PHOCAENEA) and DELPHINIDAE (LAGENORHYNCHI and
DELPHINI) show another type of corpora accumulation (Type III). They seemto be somewhat separated taxonomically from MONODONTIDAE and GLOBICEPHALIDAE. But, I consider that the difference between Type II and III
is not so substantial as Type I. So, to my opinion, superfamily DELPHINOIDEA is needful for the classification of DELPHINIDAE-type species.
DISCUSSION
In DELPHINIDAE, especially Type III group, left ovary attaines at maturity
first, and ovulations occure only from the left ovary in young generation, but after
the right ovary attains at maturity, ovulations occure more frequently from theright ovary than from the left ovary. Such a phenomenon is interesting for thephysiology of reproduction. The mechanism of control for maturity and ovulation in the each ovaries must be studied in future. As morphological approach,
distribution of blood vessels and nerves, thickness of coatical layer of each ovary andtheir change according to age should be researched for the settlement of themechanism.
It is notable that in the males both testes are almost equally mature and thedifference of weight between both testes is very slight in the case of DELPHINIDAE
so far as I investigated. Then, it is interesting why in the only females maturity andovulations are different between each sides of ovaries. Ontogenical comparison
is needful on the reproductive organs between both sexes for solution of this problem.
The asymmetry of maturity and ovulation in DELPHINIDAE is considered
to be related to the asymmetry of skull of ODONTOCETI, but PHYSETEROIDEA has same ovulatory pattern as MYSTICETI although the skull of it is asymmetry like DELPHINIDAE.
In the previous chapter I discussed the interrelationship between corporaaccumulation types and the taxomic position of CETACEA, and I found ovulatory pattern is related with the taxonomic status of the animals. Johnson & Ostenson(1959) describes that "modern taxonomic studies on specific and above must be
based on more than simple morphologic comparison when complex relationships

142

S. OHSUMI

are involved. Further research into their biologic nature is necessary ". And
they showed several taxonomic methods. As one of modern morphologic comparisons, they showed the genital tracts and foetal menbranes reported by Mossman(1953). I believe in fact that the total biologic relationship and not any single taxonomic criterion is important as Johnson & Ostenson described. And the comparisonof corpora-accumulation rate will be useful as one of the taxonomic criteria. For
this purpose, we must gather more material on all species. Especially we haveno or very small materials on PLATANISTIDAE and PHOCAENIDAE. I mustsay that comparison of corpora accumulation is only one method of taxonomical
approaches and many other biological relationships are needful for the complete
attainement to truth.
SUMMARY

1. Comparison of maturity and accumulation of corpora between the left andright ovaries is studied for 23 species of CETACEA.
2. Accumulation curves of CETACEA so far as investigated are classified into
three kinds of types.
3. Type I: Maturity and ovulation occures from both ovaries equally. Following species are considered to be included in this kind of type:
Balaenoptera musculus, B. physalus, B. edeni, B. borealis, B. acutorostrata, Megaptera novaeangliae, Eubalaena glacialis, Physeter catodon, Kogia sp. Berardius bairdii and Ziphiuscavirostris.
4. Type II: Corpora accumulation in the left ovary is rather more than the rightin young stage. But the difference between both ovaries is not so much. Following
species are considered to be included in Type II :Delphinapterus leucus, Grampus griseus, Globicephala melaena, G. scammoni, Orcinus orca
and Feresa attenuata.
5. Type III: For relatively long time, ovulation occures only from the left ovary,
but after attainement of maturity of the right ovary, corpora accumulation of theright ovary becomes more frequently than the left. Following species are included
into this type: Phocaenoides dalli, Lagenorhychus obliquidens, Tursiops truncatus, Delphinus delphis, Stenella attenuata, and S. caeruleoalba.
6. As regards the percentage of distribution of corpora in the left ovary, range
and average values of above three types are counted as follows :Range (%)
Average (%)
Type I
52.0
45-55
Type II
58--8365.6
Type III82-100
92.7
7. Corpora accumulation in MYSTJCETI and PHYSETEROIDAE is classified
into Type I. On the contrary, DEPHINIDAE seusu lato shows other types, andthey should be separated into at least two classification by consideration of corporaaccumulation types.

CORPORA ACCUMULATION IN CETACEA

143

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1-Varwisk, . L. (1926). Anat. Ree. 33: 29-33 (Cited from Asdell 1946).
vVinge, H. (1918). A review of the interrelationships of the Cetacea. Vidensk Medd. Nat. Faren. Bd.
70. (Translated by Miller, Jr. G. S. in Interrelationships of the Mammalian genera III. 222-302,
1942).

144

S. OHSUMI
APPENDIX.

RELATION OF THE NUMBER OF CORPORA BETWEEN THE
BOTH OVARIES AND THE LEFT OVARY

B: Number of corpora in the both ovaries.
L: Number of corpora in the left ovary.
2

L\B
0

2
5

2
3
4
5
6
7
8
Total

TABLE 1.
4
5

3

BALAENOPTERA MUSCULUS
10
6
7
9
8

11

12

13

2
3
7

2

2
2

2
2
2

3

4
12
16
8
8
3
3
2

2
2
2

7

4

II

3

4

TABLE 2.
L\B

I

2

0

2
3

1
6

3
2

5

4

5

4

5

6

7

6

3

2

57

BALAENOPTERA EDENI
7

8

9

10

11

12

14

13

15

3
4

2
4

5
6
7
8
Total

I

8

6

8

4

8

3

TABLE 3.
LB
0

1
2

2

3
4
5
6
7
8
9
10
II
12
Total

2

3

2
1
2

I

4

2
4

5

6

7

2

2

3

3

3

BALAENOPTERA BOREALIS
8

9

10

II

12

13

14

15

16

17

18

19

2

2
3
2
2

4
5
2

9

12

3
2

I

2

2
2

4

6

20

Total
5
8
6
13
15
8
10
3
4
4
3

2
3

Total
6
16
7
10
4
2
4
3
2
54

1

3

Total

I

3

5

8

2

6

5

3

5

2

2

3

-

3

80

6

7 8 9
10

11

12

13

0 12 8 11
1 21 24 19 7 5 2 1 - 8 12 15 6 7 3 12
6 8 9 5 2 2 5
1 31
2 3 3 9 3 4 -1
4
2- 2 5 3
1 4
3 2
5
22
1 3 6
1 1
1 2
7
1
2
3 4
8
I
1
9
1
10
11
12
13
14
15
16
17
18
19
35
9
Total 33 40 38 32 25 17 17 14 14
3 II IIL\B 1 2 3 4 5

5

3

4

1
1

2

1

I

16

-

-

4

1

1

1

1

17

-

-

2 -

-

1 -

-

20

-

1

1

18

1
1 -

3

-

18

-

-

21

-

3

I

1

1

22

~

-

-

23

BALAENOPTERA PHYSALUS

1 -

1

15

1 -

1

14

TABLE 4.

-

I

1

24

-

I

1

25

I

1

26

-

-

28

2 -

1 -

1

27

-

-

-

29

-

I

1

I

I

I

I

1

30 35 47 69

>
2

297

-

~

tr:1

tr:1

0

z0......
z......

c:s::c:I:""
>
;.-3

0
0

:>

>

~

0

~
"tl

>!
0

0

0

21
80
52
40
27
22
10
7
12
7
5
3
4
1
1
1

Total

S. OHSUMI146

MEGAPTERA NOVAEANGLIAE

TABLE 5.
L\B

2
9
13

0
I

2
3
4
5
6
Total

I

4

5
7
2

3
2
5

22

7
12

2
3
4
5
6
7
8
9
10

5

7

6

Total

13

12

II

10

9

8

13
33
22
17
7
6
2
100

I

2
II

7

L' B
0

3

20

15

4
3
2

I

4
3

10

II

2

3

4

5

6

5
16
5

2
16
26
4

2
7
26

I

I

13

II

II

2

3

6
7
8
2

8

2
2
2

2

7

3

TABLE 6.

PHYSETER CATODON

7

10

8

9

12

II

13

14

15

16

17

24

37

25

2

16
53
81
57
34
20
14
9
5
5

5

298

5
II

6
7
5

5
2
2

7
4
3

I

2
4
2

2
2
5

2
2

2

2

Total

2

II

12
13
20
Total

I

19

26

48

48

28

24

25

19

17

TABLE 7.
L\B
0
2
3
4
5
6
7
8
9
10
11
12
Total

3
20

2

3

4

I
6

I

2
3
3
4
6

5

2
17
10

5

6

9

7

8

6

4

GLOBICEPHALA MELAENA
7

8

9

10

II

12

13

2
2
6

2
3
6
3

17

3
6

2
3
3
4

2
4

12

13

8

Total
8
33
26
28
17
27
21
5
3
2
2

I

7
3
6

14

2
1
3

I

23

12

30

18

16

II

2

6

4

173

CORPORA ACCUMULATION IN CETACEA

147

TABLE 8. STENELLA CAERULEOALBA
L,B

2

3

4

5

6

7

8

9 10 II12 13 14 15

16 17 18 19 20 21

Total

0
I

2
3
4
5
6
7
8
9
10

33

34
39
46
39
43
31
21
22
17
17
9
6
4
3

I

38
44
38
41

I

24

2
19

3
19

2
14

I

10

II

12
13
14
15
16
Total 33 39 44 40 43 25 22 23

2
5

2
2
4
2
2

14

12

9

8

4

4

4

3

2

2

2
333

148

S.. OHSUMIEXPLANATION OF PLATE
Left side shows the left ovary and the right side shows right ovary in each figure. Numbersof corpora are shown as follows ; a-b : a is the number of corpora lutea, and bis the numberof corpora albicantia.

A: Balaenoptera physolus, L: 0-6, R : 0-9
B : Physeter catodon, L : 0-3, R : 0-2
C: Kogia sp., L: 0-6, R: 0-7
D: Feresa attenuata, L: 0-3, R: 0-1
E: Phocaenoides dalli, L: 1-1, R: 0-0
F: Stenella caeruleoalba, L: 0-2, R: 0-0(X 0.17)(x0.33)( x 1.1)(x 1.1)( x 1.3)(x 1.4)8l ・oN・
／SU
J ・
s
a
Hs
a
7
v
1
1
M・
J
r
》
H・
!
J
S

オ

ヨ
、
＼

。

つ

v

包

I
J
！
＼
！
凡 SHO ・
s

I3
:
.
LV'1d

A SYSTEMATIC STUDY OF THE HYOID BONESIN THE BALEEN WHALESHIDEO OMURAThe hyoid bone is accepted as having characteristics which can be used as a taxonomic criterion in the terrestrial mammals (Sprague, 1941; Johnson & Ostenson,1959). But in the whales it seems that no special importance has been placed on
the hyoid bone for systematic studies. It is of interest, therefore, to know taxonomic
characteristics of the hyoid bone of the whales. Further in whales, especially inlarger cetaceans, it is very difficult to collect a reasonable numbers of skeleton to treat
them quantitatively. Accordingly it is also difficult to ascertain whether the differences noted are the individual one or those between subspecies, species or genera.
Hyoid bone is without great difficulty be collected even in the larger whales.
In the last four years I could collect them from a total of more than 100 baleen whales,
excepting grey, greenland, and pigmy right whales. These were gathered fromthe Antarctic, Bering Sea and its neighbouring waters, and coast of Japan by mycolleague in the Whales Research Institute with assistance of personnel of thewhaling companies concerned.
In the present paper these hyoid bones were treated statistically from theviewpoint of the taxonomy.
MATERIAL
The material treated in this study are shown in Table 1.
TABLE 1.

NUMBER OF WHALES FROM WHICH HYOID BONE WAS COLLECTED
SpeciesBlue whale Balaenoptera musculus
Fin whale B. physalus
Sei whale B. borealis
Bryde's whale B. edeni
Minke whale B. acutorostrata
Humpback whale Megaptera novaeangliae""
Black right whale Eubalaena glacialis

LocalityYear

NumberAntarctic!)
Antarctic
Bering Sea•>
Antarctic
Coast, Japan
Coast, Japan
Coast, Japan
Bering Sea•>
Coast, Okinawa
Bering Sea•>

1961
1961
1960
1961
1960
1960, 62
1962
1962
1961
1062, 63

9
10
13
9

1) Pigmy blue whale. 2) Includes its nearby waters.
4) Not complete sets. 5) In meter.

10

22 8 >
11
4
94)
5

Averagebody length5>

21.77
21.00
19.16
15.27
13.21
13.05
6.24
13.50
ll .4015.28

Abbreviation
BmA
BpA
BpB
BbA
BbC
Bee
Bae
MnB
MnB
EgB

3) In which 7 samples lacking stylohyals.

As shown in Table 1 the hyoid bones have been collected from seven species
i.e. from blue, fin, sei, Bryde's, minke, humpback, and black right whales. In
order to investigate intra-specific differences samples of some species have beengathered from different localities. My first intention was that to collect each ten
149

150

H. OMURA

samples from different species and from different localities for a preliminary study.
This has not been completed.
For the blue whale samples were only collected from the pigmy blue whale in
the Antarctic. Ichihara (1961, 1963) separates the pigmy blue whale from theordinary blue whale in the Antarctic. His conclusion is mainly based on theexternal characters. It is of great interest, therefore, to examine the difference inthe hyoid bones between the two groups. But this is not possible in the present paper.
For the humpback whale samples were collected from the Bering Sea and its
nearby waters as well as from the waters around Okinawa Islands. But in the former
only four samples were collected. From the latter waters a good number werecollected, but during the course of transportation these bones were damaged andonly parts of them are available for comparison. The results of whale marking
suggest that the two stocks are belong to a single population. They are treatedin this paper for the time being as a whole accordingly.
For the black right whale I have two additional samples. In 1961 two skeletonsof this species have been secured from the same locality, but they are not available
for the present study, because they are still hurried in the earth for extraction of oil
contained in them.
Further it is interesting to compare the hyoid bones of fin whale from the East
China Sea to those from other localities, but this was impossible. The whaling
operation in that area has been stopped since 1961. I could not collect any sample
from the grey whale, Eschrichtius gibbosus.
In osteological study of such nature it is very important to compare samplesof similar age and preferably those of physically matured animals. But as a matterof fact this was very difficult. If the samples are selected only from the physicallymatured animals, then the sample number will be reduced considerably and theycannot be treated statistically. In the present study, therefore, I used hyoid bones
from animals which already attained sexual maturity or in the state of puberty inprinciple. Samples from animals younger than these have also been collected insome species, but these were not used in the present study from the above reason.
For the minke and humpback (from Okinawa) whales, however, this principle was
not applied. They include sexually immature animals because of difficulty ingathering samples. Especially in the case of the minke whale the hyoid bones wereobtained mostly from the immature whales. The average body lengths of thewhales from which the hyoid bones were collected and used in the present study
are also shown in Table 1 and in detail in Appendix 1.
The present paper, under circumstances mentioned above, is of preliminary
nature and it should be supplemented or revised in future when more samples arecollected.
GENERAL DESCRIPTION(Plates I-XV)
The hyoid bones of baleen whales are consisted of three separate bones i.e. one

HYOID BONES

151

combined bone of basihyal and thyrohyals, and two stylohyals. In general thebasihyal and thyrohyals are united completely and no suture between them isvisible. Omura (1958) reports that in his Ayukawa specimen of the black rightwhale the basihyal and thyrohyals are not ankylosed into a mass and in his specimen
from Kiritappu of the same species the sutures were still visible, though the bones
were united completely. They were both sexually immature and the body lengthof these whales were 11.65 and 12.40 meters respectively. Omura (1957) also
reports that his specimen of minke whale (7 .50 meter long) had a combined
basihyal and thyrohyals in which two shallow notches were present, in addition
to the median notch, on the anterior margin of the bone, on the borders of basihyal
and thyrohyals. In the hyoid bones used for the present study none of such facts
was observed. The basihyal and thyrohyals are united completely into a massand no suture between them is visible. The smallest black right whale in the present
study is 14.10 meter in length. This is much larger than the Ayukawa and Kiritappu specimens. This whale was a female and it had no corpus luteum andc. albicans in its ovaries, but contained in one of the ovaries a ripening follicle.
Also in this specimen no sture was visible (Plate XV Fig. 1). It is suggested, therefore, from the above facts that in the black right whale the basihyal and thyrohyals
are separated in younger stages as in the case of the toothed whales, but they unite
completely before the whale reach puberty.
For the minke whale all of the samples except two were collected from smaller
animals than 7.50 meter, but none of them had any additional notch on the anterior
margin of the combined bone of basihyal and thyrohyals, except the median notch.
It is possible, therefore, that the case of the presence of the two additional notches,
as reported by him, is the exceptional one. In the samples from the sei and Bryde's
whales, which had not been used in the present study because of immature, also no
additional notch is present.
The ankylosed bone of basihyal and thyrohyals is wing-like shape in general.
The central portion (basihyal) is dorso-ventrally compressed and has two anterior
projections, forming a median notch. The length of the anterior projections isdifferent individually, but in general they are short in the black right and humpback whales and long in whales which blong to genus Balaenoptera. I have no
specimen from the grey whale, but according to Andrews (1914) they are also short.
In the central portion there also present a pair of projections on the posterior
side. These posterior projections are rounded in general, but subject to heavy individual variation. In some specimens they are prominent, but in another specimens they are less prominent and in the extreme case they are jointly forming one
roundish median projection. Such cases are observed in the sei and Bryde's whales(Plate VI, Figs. 5, 6, Plate X, Fig. 3, Plate XI, Figs. 1, 8, 10). In the minke
whale the posterior projection present as single roundish median projecion or lessdeveloped (Plate XIII).
The wing portion (thyrohyals) thickens towards the distal ends in general andin the black right whale it becomes nearly cylindrical, but in the sei, Bryde's andminke whales they are rather flat. In the blue whale it increases its thickness

152

H. OMURA

rapidly, but it also increases its breadth in the mid-length. The both distal ends
are narrow and thin in the whales belong to the genus Balaenoptera, but very massivein the black right whale. In the humpback whale they are more massive than thoseof the genus Balaenoptera, but in lesser degree than in the black right whale.
The ankylosed bone of basihyal and thyrohyals is concave from the dorsal aspect,
but the degree of the curvature is seemed more individual than specific, excepting
the black right whale in which the bone is nearly straight on the ventral surface.
I have used, therefore, the overall length along the outer surface and passing thecenter of the basihyal as the length of the bone, instead of the straight length between
the two distal ends. The overall lengths of the combined bones are generally between five and seven per cent of the body lengths of the whales. No significant difference according to species is noted among these percentages.
The stylohyals are flat in the whales of the genus Balaenoptera. Also in the humpback whales they are rather flat, but those of the black right whale are quite different
from other species. They are nearly cylindrical and somewhat constricted in the
one-thirds portion from the proximal ends. In one occasion among four, however,no such constriction is observed (Plate XV, Fig. 8). In this sample the ventral
view of the stylohyal resembles more closely to that of the humpback whale andrather flat in general. But it thickens suddenly towards the distal end and approaches to cylinder.
The stylohyals of the fin, minke, and humpback whales are narrower than thoseof the blue, sei, and Bryde's whales. But in the fin whale, in some specimens they
are broader than the other and very difficult to identify them from those of the blueand sei whales (Plate III Lower, Fig. 3, Plate V, Fig. 7). In the sei whale thestylohyals are much curved forwards and in the Bryde's whale they are less curved
and more slender, but there present some exceptinal cases (Plate VII, Fig. 2,
Plate XII, Fig. 14).
The surface of the hyoid bones, both the cmbined bone of basihyal and thyrohyals and the stylohyals, are generally smooth in most species. In the humpback
whale, however, they are rugose bones. In the blue and fin whales the anterior andposterior projections are more or less corrugated, but in lesser degree than in the
humpback whale. Andrews (1914) reports that the hyoid bone of the grey whale
is extremely massive and rugose bone. He also describes that the shape of the
thyrohyal portion of the combined bone resembles to that of Eubalaena and his photograph supports this, but in the present samples from the black right whale thesurface of the bone is very smooth. It is suggested, therefore, the rugose hyoidbone is a specific character of the humpback and grey whales.
MEASUREMENTS

The following measurements were made on each hyoid bone collected (see Fig. 1).
A. Ankylosed bone of basihyal and thyrohyals.
a. Overall length. This was measured between the tips of the wings (thyrohyals)
by a curved line, running along the outer surface of the bone and passing the

HYOID BONES

b.

153

center of the basihyal.
Straight length. This was measured by a straight line between the tips of
the wings, disregarding the curvature of the bone. This length was onlyused for checking.

I lpl

Fig. 1.

c.

Showing positions of the measurements.

Greatest height. Greatest height between tips of the anterior and posterior
projections of the basihyal.
d. Height at center. Height measured at the center of the bone.
e. Forward notch, depth. Depth of the notch between the pair of forward projections of the basihyal.
f. Height at middle of the wing, right. Height measured at middle between thecenter of the basihyal and the tip of the right wing.
g. Height at middle of the wing, left. Height measured at middle between thecenter of the basihyal and tip of the left wing.
h. Thickness at middle of the wing, right. Thickness of the right thyrohyal on theline of the measurement f.
1.
Thickness at middle of the wing, left. Thickness of the left thyrohyal on theline of the measurement g.
j. Height at distal end, right. Height of right thyrohyal at its distal end.
k. Height at distal end, left. Height of left thyrohyal at its distal end.
B. Styohyall. Total length, right. Length measured by a straight line between the tips ofthe right stylohyal.
m. Height at middle, right. Height at middle of the right stylohyal.
n. Thickness at middle, right. Thickness of the right stylohyal measured on theline of the measurement m.

H. OMURA

154

Degree ef curvature, right. Greatest distance between the straight line whichpass the most prominent parts of the right stylohyal and its forward surface.
p. Total length, left. Corresponding measurement of 1 of the lef stylohyal.
q. Height at middle, left. Corresponding measurement of m of the left stylohyal.
r. Thickness at middle, left. · Corresponding measurement ofn of the left stylohyal.
s. Degree ef curvature, left. Corresponding measurement of o of the left stylohyal.
o.

~7

BmAR
BmAL

~8

BpAR

.10

BpAL

~

BpBR

(Kil113

BpBL

~13

~9

BbAR
BbAL
BbCR
BbCL

I 10

.9

l]i:J

I

I

10

11•1110

•

Be CR
BeCL
BaCR

I .

Ba Cl

I

20

I

20
I

111

I.

MnBR

11

11•1
1•1
1

MnBL

I
I

EgBR

5

EgBL

5
5

6

7

8

9

10 11 121010

13 14 15 16 17 18 19%

Fig. 2. Combined bone of basihyal and thyrohals.
Proportional height at distal ends against overall length.
The horizontal line represents the ranges ; the vertical midline the arithmetic mean ; the outerbox one standard deviation on either side of the mean; the inner box two standard errors on eitherside of the mean ; the figures are the sample numbers.
See Table 1 for explanation of abbreviation. R and L attached mean the right and left sides
respectively.

Above measurements were then calculated of their percentages against theoverall length in the case of the combined bone of the basihyal and thyrohyals. For
the stylohyals also were calculated percentages of their length against the overall
length of the combined bones, but their heights, thickness and the degree of curvature
were calculated as the percentages of the total length of the stylohyals. Further
for each measurement the arithmetic mean, standard deviation and the two standard
errors were calculated. The results are shown in Figs. 2-11, together with the ranges

155

HYOID BONES,f the value.

The details of the measurements are shown in Appendix 1 and theesults of the calculations in Appendix 2.

1~1 1 8

BmA

11~1

BpA
BpB

I

I

r~

110

I

1

13

11~1

BbA
BbC

1-.1110

BeC

I •

I

122

l~l

BaC

19

111

1~1110

MnB

~5

EgB

12 13 14 15 16 17 18 19 20 21

22 23 24 25 26%

Fig. 3. Combined bone of basihyal and thyrohyals.
Proportional height at center against overall length.
See Fig. 2 for explanation.

1~1,3

BmA

1l-l16

BpA
BpB

1

I

BbA
BbC
BeC
BaC
MnB
EgB

11

~-1~~ii~~fW-~W;;1W;W~1$l~_____,I 9t------+---< 5

21 22 23 24 25 26 27 28 29 30 31' 32 33 34 35 36 37 38

Fig. 4. Combined bone of basihyal and thyrohyals.
Proportional height (greatest) against overall length.
See Fig. 2 for explanation.

A.

The combined bone of basih;_yal and thyrohyals.
1. Proportonal height at distal ends (Fig. 2). As seen in Fig. 2 the whales are
divided into three groups in this character. The blue, fin, sei, Bryde's andminke whales (genus Balaenoptera) are all belong to one group. The humpback
whale (genus Megaptera) are separated significantly from this group. It ishighly possible that the black right whale (genus Eubalaena) is distinct fromthe above two groups, though the sample number is fewer than any otherH. OMURA

156

11w~1

BmA
BpA

8

·l•~I

BpB

6

1~11

· 11

J!W~lsi----~~1t:=!~~Wi~~~~~@~@i~~~l~10

BbA

I

BbC
BeC

I

i------tJ~W,~Wi~@~~~~~~=I-~ I I

Bae

I SI

20

[WJ 9

MnB

I

EgB

!--I----<

5

2

6

3

4

5

7

8

9

10 11 12 13 14%

Fig. 5. Combined bone of basihyal and thyrohyals.
Proportional depth of forward notch against overall length.
See Fig. 2 for explanation.
BmAR

BmAR

BmAL

BmAL

BpAR

BpAR

BpAL

BpAL

BpBR

BpBR

BpBL

BpBL

BbAR

BbAR

BbAL

BbAL

+•1

18

·1•1

18

~ 10

~I

I

10

~13
~13
~9

•

19

~10

BbCR

BbCR

BbCL

BbCL

BeCR

Be CR

i:mJ 20

BeCL

BeCL

~20

BoCR

Bo CR

BoCL

Bo Cl

MnBR

Mn BR

MnBL

MnBL

EgBR

EgBR

~5

EgBL

EgBL

~5

.10
I

11•1;11
111
liil.
EMJ110

I

~10
I

8

9

10 11 12 13 14 15 16 17%

Fig. 6. Combined bone of basihyal and thyrohyals.
Proportional height at middle of the wing against
overall length.
See Fig. 2 for explanation.

5

6

7

8

9

10 11

12
"1

·''

Fig. 7. Combined bone of basihyal andthyrohyals.
Proportion! thickness at middle of thewing against overall length.
See Fig. 2 for explanation.

157

HYOID BONES

species. In the fin and sei whales, those from the Antarctic show somewhat
different value of the arithmetic mean from those from the Bering Sea or thecoast of Japan, but they cannot be separated, because the two standard errors
are overlappng each other. In other words neither racial nor subspecific difference is noted within the same species. But there is a significant difference
between the minke whale from the coast of Japan (BaC) and the sei whalefrom the same locality (BbC), though no difference is present between the
BmAR
BmAL
BpAR
BpAL
BpBR
BpBL
BbAR
BbAL
BbCR
BbCL
BeCR
Be CL
Ba CR
Ba CL
MnBR
MnBL
EgBR
EgBL

r----t-----;>--t----;

4

3

32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 ,.
%Fig. 8. Stylohyals. Proportional length of stylohyals against the overall length of the combined bone.
See Fig. 2 for explanation.

former and the sei whale from the Antarctic (BbA). The same is applied also
to the fin whale. In general no significant difference is noted in this character
among the species of the genus Balaenoptera.
The values for the right and left sides are coincide fairly well in eachspecies.
2. Proportional height at center (Fig. 3). In this character the whales are divided
ino two groups. The blue and fin whales are belong to the same group andthe sei, Bryde's, minke and humpback whales to the another. The blackright whale is probably be included in the former group. No difference isnoted in the fin and sei whales between those from different localities.

H. OMURA

158

3.

Proportional height (greatest) (Fig. 4). In this character all species except theblue whale are grouped into two. The fin, minke, humpback and black rightwhales are belong to one group and the sei and Bryde's whales to theanother. Also in this character no difference is noted in the fin and sei whales
between whale stocks in different localities.

1mJ 9

BmAR

~3

BmAL
BpAR

1rl-1,-~=•'r37.=,,,,-;;i;;~-~~='1-I_

BpAL

1e------<1~•-4<'~A'0+--+-___,. ]0

BpBR
BpBL

____, I 0

113
1•1113
1~1

BbAR
BbAL
BbCR
BbCL
BeCR
BeCL
Ba CR
BaCL
MnBR
MnBL
EgBR
EgBL

4

~3
14 16 18 20 22 24 26 28 30 32 34 36 38 40

Fig. 9. Stylohyals. Proportional height at middle against its length.
See Fig. 2 for explanation.

4.

Proportional depth of forward notch (Fig. 5). In this character the humpback
and black right whales are forming one group, distinctly different from theblue, fin, sei and Bryde's whales. In other words the forward projections
are generally much longer in the genus Balaenoptera than Megaptera and Eubalaena. One exception of this is the minke whale. It has much shorter forward
projections than any other species of that genus. It should be reminded,however, that the samples from the minke whale were mostly collected fromthe immature whales as stated before.

5.

Proportional height at middle of the wing (Fig. 6). In this character there canbe noted two distinct groups and one overlapping group. The blue and minke
whales belong to one group and the fin and humpback whales to the another. The other species i.e. the sei, Bryde's and black right whales are over-HYOID BONES

159

lapping to these groups. I cannot separate the fin whales in the Antarctic
from those from the Bering Sea. The two standard errors are overlapping
each other, though very slightly. But probably they can be separated whenmore samples are collected in future. The blue whale is distinctly separated
from the fin whale in this character. No difference is noted between right andleft sides in each species.

BmAR

9.

BmAL

s.

,,.,

BpBR

,.

BpBL
BbAR
BbAL

13

I~ I
I~ I

I9
I8

I
I

••

I ,9
I ~ I I 10

BbCR
BbCL
BeCR

'

Be Cl

~ I
I~ I
II ~ I
:~ I

BaCR

1\

BaCL
lv\nBR
lv\nBl
EgBR
EgBL

I 10
I 10

I~
I IW"frM
fWI ' 13

BpAR
BpAl

~I

~AMI

I· 15

I I15

I 11
I 11
18

I8
4
3

)------

89

10 11 12 13 14 15 16 17 18 19 20 21 22~10

Fig. 10. Stylohyals. Proportional thickness at middle against its length.
See Fig. 2 for explanation.

6.

B.

7.

Proportional thickness at middle of the wing (Fig. 7). In this character the genus
Balaenoptera is divided into two groups. The blue and fin whales belong to one
group and the other species to the another. The humpback and black rightwhales are also belong to the former group. But this character might be oflittle value for comparison of the genera. In the genus Balaenoptera the thickness
is usually the greatest towards the middle of the wing, whereas in the genus
Megaptera and Eubalaena the distal end is the thickest.
Stylohyals
Proportional length of stylohyals (Fig. 8). The genus Balaenoptera is devided into
three groups in this character. The blue whale has the shortest stylohyals, theH. OMURA

160

fin whales comes next, and the sei, Bryde's and minke whales have longer
stylohyals than other species. The humpback whale has wider ranges of variation and they are overlapping to the values for the blue and fin whales. The
black right whale seems to have little longer stylohyals than the humpback
whale. No difference is noted between the right and left sides. No differenceis also observed in the fin and sei whales between those from different localities.
BmAR

I w.~~

BmAL

I

BpAR

~8,V~

•9

I

s

IW~l·

I

BpAL

I
9

WY,.
I
-J#,1

W~fim

I

BpBR
BpBL

I

BbAR

9•1

BbAL

8 1·

·10
13

I

13

~~
~4M] I
i·W~A

BbCR
BbCL

I

••a I

I~ I
15
/
~ /
.15
1~1·11

Be CR
BeCL
BaCR
Ba CL

/~/·11

Mn BR

·l~•I

MnBL
EgBR

,..,.1•7
f----i-------1 4

EgBL

3
2

3

4

5

6

7

8

9

10 11

I

9

lo

,1

12 13 14 15 16 17 18%

Fig. 11. Stylohyals. Degree of curvature.
See text and Fig. 2 for explanation.

8.

Proportional height at middle (Fig. 9). In this character all whale species except the Bryde's whale are classified into two groups. The blue and sei whales
have broader stylohyals than other species. The Bryde's whale has a greater
vaue than fin whale, but they are still separated from the sei whale in thischaracter. Again no difference is noted between the right and left stylohyals
and between those from different localities within the same species.

9.

Proportional thickness at middle (Fig. 10). As seen in Fig. 10 the blue whale
has thicker stylohyals proportionally than any other species. It should be
noted that the Bryde's whale is separated from the sei whale in this character
too.

161

HYOID BONES

10. Degree of curvature (Fig. 11). The stylohyals are usually curved forwards
and the degree of the curvature was expressed as percentage of the lengthstated already (measuremens o and s) against the length of the stylohyal.
Rather wide ranges of variation are observed in each species. The Bryde's
whale is separated from the sei whale from the coast ofJapan, but the two standard errors are very slightly overlapping to that of the sei whale in the
Antarctic. It seems that this character is of less importance in other species.
CONCLUSIONIn Table 2 the results of the measurements are summarized briefly. As seen inthis table most whale species, from which the hyoid bones were collected, areseparated from each other by the combined bone of basihyal and thyrohyals.
One exception of this is the distinction of the Bryde's whale from the sei whale.
The combined bone of basihyal and thyrohyals of the both species resembles
each other very closely and they cannot be identified by this bone. But in the stylohyals the Bryde's whale is separated from the sei whale, having less broader, muchthicker and less forwardly curved stylohyals. As already noted, however, there
TABLE 2.

SUMMARY OF COMPARISON
Species and locality

A.

Items
Combined bone of basihyal and thyrohyals
I. Proportional height at distal ends .........
2. Proportional height at center ...............
3. Proportional height (greatest) ...............
4. Proportional depth of forward notch ......
5. Proportional height at middle of wing ...
6. Proportional thickness at middle of wing

Stylohyals
7. Proportional length of stylohyals ............
8. Proportional height at middle ...............
9. Proportional thickness at middle ............
10. Degree of curvature ...........................

BmA BpA

BpB

BbA

BbC

BeC

Bae

MnB EgB

0
0
OL1
0
0
0

0
0
0
0
L1
0

0
0
0
0
L1
0

0
L1
L1
0
OL1
L1

0
L1
L1
0
OL1
L1

0
L1
L1
0
OL1
L1

0
L1
0
OL1
0
L1

L1
L1
0
L1
L1

O?

0
L1
OL1
0

0
0
0
0

L1
L1
L1
0

L1
L1
L1
0

x
x

x
x

x

x

L1
Od

L1
d

Ll'
Ll'

L1
L1
0

OL1
L1
L1
Od

L1X
L1
L1
Od

x
O?

B,

0

See Table I for species and locality.
0, L1, X, showing groups of species of similar value.

are some exceptional cases in which the identification is very difficult. The stylohyals
reported by Lonnberg (1931), Junge (1950) and Omura (1959) show the typicalshape in the Bryde's whale and that reported by Andrews (1916) shows that in thesei whale.
On the whole the most important character seems to be the proportionalheight at the distal end of the combined bone of basihyal and thyrohyals. The
genera Balaenoptera, Megaptera and Eubalaena are separated in this character and the
proportions in these genera can be expressed as 5-9, 9-12 and 12-19 per centrespectively of the overall length of the combined bone. I have no material from

162

H. OMURA

the grey whale (genus Eschrichtius), but according to the report by Andrews (1914)
the combined bone of this species resembles very closely to that of Eubalaena. It
is thought that it cannot be separated from the black right whale in this character.
He further reports, however, that in the grey whale the combined bone and stylohyals
are rugose bones. He also reports that the stylohyals are decidedly more liketo those of the genus Balaenoptera than the genus Eubalaena. The above two facts
may be the distinction between the two genera (or families).
The genus Balaenoptera is further devided into two groups by the proportionalheight at center of the combined bone. The blue (B. musculus) and fin (B. physalus)
whales belong to one group and the rest to the another. The blue and fin whales
are then separated decidedly from each other by the proportional height at the
middle of the wing of the combined bone.
Among the another group i.e. the sei (B. borealis), Bryde's (B. edeni) and minke(B. acutorostrata) whales, the minke whale is separated from the other two by the
total height of the combined bone. The remaining two species are not separated
from each other in the combined bone as stated already.
In the stylohyals each species of the genus Balaenoptera is separated by the proportional length of stylohyals and then by the proportional height at middle of thebone. Further the blue whale is separated very clearly from the other species by
the proportional thickness at middle of the stylohyals.
The above is arranged in the order of the following systematic key.

I.

2.

3.
4.

5.

Key to the genera and species of mystacoceti
by means of hyoid bone
Height at distal end of the combined bone of basihyal and thyrohyals morethan 12 per cent of its overall length. . . . . . . . . . . . . . . . . . . . . 2
The same height 9-12 per cent. Bone surface much corrugated.
Genus Megaptera. Single species. . . . . . . . . . . . . . . . M. novaeangliae
The same height less than 9 per cent. Bone surface smooth.
Genus Balaenoptera. . . . . . . . . . . . . . . . . . . . .
. . . . . 3
Bone surface much corrugated. Stylohyals massive but not cylindrical.
Genus Eschrichtius. Single species. . . . . . . . . . . . . . . . . . . E. gibbosus
Bone surface smooth. Stylohyals roughly cylindrical. Basihyal and thyrohyals separated in younger stages.
Genus Eubalaena. Single species . . . . . . . . . . . . . . . . . . . E. glacialis
Height at center of the combined bone less than 18 per cent of its length. . 4
The same height more than 18 per cent. . . . . . . . . . . . . . . . . . . . 5
Height at middle of the wing of the combined bone less than 12.5 per centof the length. Stylohyals long and narrow. . . . . . . . . . B. physalus
The same height more than 12.5 per cent. Stylohyals short,broad and massive. . . . . . . . . . . . . . . . . . . . . . .
. B. musculus
Greatest height of the combined bne less than 29 per centof the length. . . . . . . . . . . . . . .
. B. acutorostrata
The same height more than 29 per cent. . . . . . . . . . . . . . . . . . . 6

HYOID BONES

163

Stylohyals broad, flat and much curved forwards . . . . . . . . . B. borealis
Stylohyals less broad, rather thick and less curved. . . . . . . . . . B. edeni
In the above key the greenland whale (Balaena mysticetus) and the pigmy rightwhale (Caperea (Neobalaena) marginata) are not included. These two are very rare
species, at least at present. The key was made for the convenience of the identification of the species by means of the hyoid bone, disregarding families. It is clear thattaxonomic studies on the specific level and above must be based on more than single
morphologic comparison and any single taxonomic criterion is less important. My
first intention was that to study whether there present any skeletal difference between
the whale populations from the different localities within the same species. As already stated before any such racial difference was not proved. But in the case of
the fin whale the population in the Bering Sea show lower value than that in the
Antarctic in the proportional height at middle of the wing (Fig. 6) and also in the
proportional height at distal ends of the combined bone (Fig. 2). These give theformer bone a slender appearance than the latter. The two standard errors calculated for the both are overlapping very slightly. The sample number used for thepresent study is rather limited and it is thought probable that a significant difference might be proved when more samples are gathered. Also in the sei whale
collection of more samples are needed in order to discuss the difference between thatfrom the Antarctic and that from the coast of Japan. It might be most interesting
to compare the hyoid bone from the usual blue whale in the Antarctic to that ofthe pigmy blue whale.
In conclusion more attention than bebore should be paid on the morphologicalstudy of the hyoid bone in establishing relationships of subspecies, species and generaof the baleen whales.

6.

SUMMARY

The hyoid bones of the baleen whales were collected from seven species. These
are the blue, fin, sei, Bryde's, minke, humpback and black right whales. For thefin and sei whales they are collected from the two different localities. Total numberof whales from which the bones were sampled had amounted a little over 100.
Various measurements were made on each bone and then they were treated statistically. Distinctions among species were studied and a key to the genera and species ofbaleen whales (mystacoceti) by means ofhyoid bone was prepared. Distinction between different populations within the same species was not proved statistically,
but it is thought more collection is necessary in order to obtain a conclusion on thismatter.

164

H. OMURA

ACKNOWLEDGEMENT

Sincere thanks are due to my colleague in the Whales Research Institute. They
helped me in the collection and measurement of the samples. Especially I amvery grateful for Drs. K. Fujino and T. Nemoto. They also took photographs
shown in Plates I-XV.
REFERENCES
ANDREWS, R.C. (1914). The California gray whale (Rhachianectes glaucus Cope). Mem. Amer. lvlus. Nat.
Hist., New series, l(V): 229-87.
- - (1916). The sei whale (Balaenoptera borealis Lesson). }vfem. Amer. Mus. Nat. Hist., New series,!(IV): 291-388.
lcHIHARA, T. (1961). Blue whales in the waters around Kerguelen Island. Norsk Hvalfangst-Tid., 50(1):1-20.
- - (1963). Identification of the pigmy blue whale in the Antarctic. Norsk Hvalfangst-Tid., 52(5):128-30.
JOHNSON, M.L. & OSTENSON, B.T. (1959). Comments on the nomenclature of some mammals of the PacificNorthwest. J. Mamm. 40: 571-7.
JuNGE, G.C.A. (1950). On a specimen of the rare fin whale, Balaenoptera edeni Anderson, stranded on Pulu
Sugi near Singapore. :(oologische Verhandelingen, no. 9: 1-26.
LoNNBERG, E. (1931). The skeleton of Balaenoptera brydei 0. Olsen. Arkivf. Zoologi, 23(1): 1-23.
OMURA, H. (1957). Osteological study of the little piked whale from the coast of Japan. Sci. Rep. Whales
Res. Inst., no. 12: 1-21.
- - (1958). North Pacific right whale. Sci. Rep. Whales Res. Inst., no. 13: 1-52.
- - (1959). Bryde's whale from the coast of Japan. Sci. Rep. Whales Res. Inst., no. 14: 1-33.
SPRAGUE, J.M. (1941). A study of the hyoid apparatus of the Cricetinae. J. Mamm. 22: 296-310.

_2)

- 2>
- 2>

720
1790
1850
1870
1890
2010
2020
2180

II
2
3
4
5
6
7
8

BpB

9

1940
1950
2040
2090
2110
2110
2130
2170
2190
2270

I
2
3
4
5
6
7
8
9
10

BpA

10
II

2100
2100
2230
2280
2280
2300
2050
2250

2000

I
2
3
4
5
6
7
8
9

BmA

a

b

c

d

104.0

88.0

-

16.0

c

13.7
17.0
14.5
14.0
15.4
14.0
13.4
17.0
20.0

f

g

19.5
19.3
22.7
23.2
21.8
26.0
22.6
18.5
21.4

h

12.2
12.2
15.2
14.3
16.4
16.5
15.8
12.5
13.4

i

12.l
12.5
14.6
14.6
16.9
16.8
15.3
12.5
13.1

12.6 12.4 10.4 10.0

19.8
20.0
22.5
22.2
22.6
25.8
22.0
19.2
21.2

k
l

m

7.2

7.4 47.0

12.5

10.3 9.7 55.5 17.6
11.3 11.9 60.0 18.3
9.3 9.9 55.0 20.2
65.0 19.8
11.2 11.4 57.0 20.5
11.8 11.0 63.0 21.2
10.1 62.0 21.4
12.0 13.0 56.5 19.0
10.3 10.7 61.0 20.6

jMeasurement

M
M
M

118.0
106.0
109.0
F 120.0
M 118.0
F 124.0
F 135.0- 2 > 123.0- 2 > 111.0- 2 > I I6. 0

M 108.0

17.3
33.l 19.4
33.6 19.1
17.6
35.3 17.2
33.5 17.4
11.2
11.0
13.5
15.5

15.2
12.9
14.9
15.6
11.5
14.3

91.0 33.0 17.3 11.4 9.7
97.0 26.3 16.3 9.0 11.5
90.0 25.3 17.3 7.2 10.6
91.0 27.0+ 16.7 8.2+ 10.5
101.0 42.0 25.5 15.3 14.I
100.0 29.0+ 15.5 10.6+ 12.0
106.0 38.0 18.3 13.5 14.0
110.0 32.3 17.0 10.5 12.3
99.0 37.3 23.2 12.4 14.2
97 .0 25.6 17 .7 6.0 10.9
92. 0 25. 2 I6. 2 7. 5 I0. 0

119.0 104.0
M 133.0 109.0
M 128.0 109.0
F 124.04>
F 123.0 109.0
F 125.0 109.0

F

JO.I
12.2
10.5
10.5
14.3
lI.I
13.3
13.0
14.3
10.8
10. 3

14.8
13.4
14.7
15.4
11.7
13.8
7.9
10.4
8.8
9.0
11.5
9.0
II.I
12.2
9.7
9.8
10. 0

12.6
11.3
10.0
13.0
9.6
10.8
7.5
10.0
8.6
8.9
11.3
8.4
11.3
12.2
9.6
9.4
9. 7

13.0
11.5
9.7
12.7
9.9
10.6
5.9
7.9
6.1
6.5
6.9
7.9
6.2
7.6
8.4
8.0
7. 2

8.0
8.8
9.0
9.4
8.7
8.4
5.9
8.1
6.2
6.5
7.2
7.9
7.1
8.3
8.2
8.0
7.0

7.8
8.7
8.5
9.2
9.2
8.3

50.0
56.0
47.0
48.0
54.0
53.5
57.0
60.0
56.0
53.5
50.0

55.0
64.0
56.0
59.0
57.0
59.0

12.0
13.0
12.3
8.4
II.I
13.0
15.2
15.5
15.7
12.1
10.6

12.8
17.3
11.8
16.2
15.0
13.3

M 119.0 99.0 29.8 18.8 10.5 12.7 12.7 10.6 10.2 7.4 7.4 54.0 11.4
M 130.0 109.0 38.8+ 23.0 7.8+ 14.3 14.7 12.3 13.0 10.0 10.9 55.0 19.2
M 124.0 108.0 34.8 22.5 9.5 13.3 13.4 9.9 9.9 8.2 7.8 55.0 14.7

F

136.0 113.0 38.0 20.2
F 150.0 127.0 42.4 22.7
M 147.0 120.0 44.4 26.2
M _s>
43.5 26.5
F 146.0 120.0 43.8 25.5
M 115.0 129.0 45.3 28.0
F 168.04>
44.6 25.6
F 144.0 112.0 44.6 24.8
F 158.0 133.0 46.3 24.3

M

Species,
Body S
locality No. length ex

APPENDIX !. MEASUREMENTS OF HYOID BONE (in cm.)
Sec text for explanation of abbreviation and measurements number

4.5
5.2
4.4
4.8
6.4
5.2
6.3
6.7
5.2
5.6
4.6

12.3
13.0
12.1
8.4
12.0
13.5
14.7
14.5
15.3
12. l
11.0

50.0
56.0
48.0
48.0
54.0
53.0
56.0
60.0
56.0
54.0
50.0

5.3
5.0
3.6
4.6
4.3
4.2
7.2
6.7
3.4
4.0
5.5

4.8
5.2
4.5
4.8
6.7
5.3
6.2
7.1
5.5
5.6
4.5

5.6
5.6
8.0
5.4
5.8

7 .6

6.4
5.7

5.8
4.8
4.0
5.1

7 .0

4.3
4.0

4. 7

5.4
5.0
4.1

1.3
1.3
4.0
7.5
3.9
4.2
5.7
6.0
5.7
6.5

6.4
7 .0

4.0
1.4
4. I
7.0
8.9

20.7 12.1
21 .5 12.5
21 .8 10. I
19.9 9.0
20.4 11.0

59.5
62.5
62.0
58.0
60.5

12.5
11.3
19.0
14.5
13.4
17.4
12.5
16.0
14.9
13.5

2.7
4.0
3.0

p
q
r
55.0 18.3 9.3
61.0 18.4 11.2
56.0 20.2 12.2

48.0
54.0
55.5
55.0
54.0
63.0
57 .5
5.8 59.0
5.8 57.0
6.6 60.0

1.3
I.I
4.2
6.5
4.0
4.5

6.7
7.1
6.3
5.3
7.6
5.8
6.2
8.0
5.0
5.6

o

2.2
3.5
3.1
3.5
3.5
I .4
4.0
7.0
8.0

n

9.5
10.9
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85.0
88.0
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83.0
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96.0
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75.0
73.0
72.0
75.0
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89.0
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72.0

78.0
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66.0
69.0
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1280
1280
1290
1300
1340
1350
1360
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1300
1450
1450
1520
1560
1570
1610
1610
1670

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-

1230
1290
1200
1230
1260
1270
1270
1360
1360
1230
11 1250
12 1270
13 1290

2
3
4
5
6
7
8
9
10

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2
3
4
5
6
7
8
9
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2
3
4
5
6
7
8
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12
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67.0
70.0
64.0
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62.0
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73.0
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70.5

61.0
61.0
66.0
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15.2
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4.4
5.2
5.5
5.4
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4.8
4.8
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6.3 10.0 9.9
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4.8
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6.3
5.0
4.5
5.4
6.1
5.6
6.1
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8.8
8.9

11.8
10.3
10.4
13.7
10.9
10.3
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6.3+ 12.5
10.5 10.9
10.7 10.0
10.5 14.1
10.8 10.9
8.0 9.8
13.0 11.0
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9.8 10.9 10.6
8.8 11.1 10.9

13.6
9.6 10.l
14.6 10.6 8.3 8.4
13.7 8.7 8.6 8.6
12.6 9.3 8.6 8.7
15.2 7.0 9.0 9.5
16.0 9.3 9.9 10.2
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13.9 10.0 9.2 9.5
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24.2 15.6 8.2 8.8 9.2
25.3 15.1 9.1 9.3 9.5
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25.5
22.5
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22.7
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79.0 25.6+ 18.0
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92.0 26.8 15.2
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6.8
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5.8
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4.9
5.5
4.7
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6.4
5.5
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5.5
4.8
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4. 7

5.2
5.5
5.7
5.6

5.3
5.1
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5.5
4.9
6.0
5.5
6.0
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5.1
5.2
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4.6 39.0 12.0
3.6 37:0 11.8
5.3 40.0 13.0
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5.6 39.0 12.9
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4.7
3.8
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39.6
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11.4
11.7
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38.5 12. 3
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16.5
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16.4
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18.0
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4.5
4.2
5.1
5.5
5.3
5.9
4.7
4.8
4.8
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45.0
46.0
42.0
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50.0
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6.7
6.0
6.1
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6.4
6.4
6.9
6.6
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6.7
5.8
6.5
6.3
6.8
6.3
6.3
6.0
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6.3
5.1
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5.2
6.3
5.6
5.9
6.4
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7.4 51.0 10.2
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7.4
6.8

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5.1
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5.1
6.2

5.3
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4.3
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4.5
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12.0
11.9
13.3
12.6
13.5
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2.9
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40.0 11.8
41.3 11.6
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5.1
6.3
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5.2
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4.5
3.9
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4.8

46.0 14.8
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38.0
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4.5
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4.8
4.6
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2.5 39.0 11.9
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4.8
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15.7
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5.7
3.5
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4.7
4.8
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500
540
576
578
580
590
637
670
710
718
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1300
1310
1330
1330
1340
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1380
1390
1440

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12
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1410
1290
1290
1410
1070
1070
1130
8 11309 119010 1250

1
2
3
4
5
6
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10
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8
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2
3
4
5
6
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14
15
16
17
18
19
20
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55.0
79.0

50.0 14.4 11.6
70.0 22.4 16.5

62.0 19.2 13.3
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3.3

3.8
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42.0 10. 7 8.6
74.0
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48.0
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2.5
1.2
2.6
1.3
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2.7
2.9
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3.1
3.4
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4.5

81.0
72.0

f

g

8.6
10. 7

8.4

6.9
7.8

8.2

8.1
7.0
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7 .1

7 .0

5.2
7 .8

5.4
8.3

7 .9

9.9

8.2

7 .9

4.4
4.6
4.5
5.0
5.0
4.5
5.3
5.7
5.8
5.8
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8.5

4.6
4.6
4.5
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4.6
4.5
5.5
5.8
6.2
5.9
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10.7 9.6 9.6
10.3 8.8
7.6
8.4
8.9 9.7 9.8
9.2 9.6 9.4
9.8 9.6 9.9
10.1 10.5 9.9
10.3
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20.9 15.5
22.7 16.4
20.6 16.3
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9.9 7.6
7.9 6.8
9.1 6.8
8.1 6.5
9.3 7.2
8.3 6.8
10.5 7.5
11.9 9.2
12.4 9.6
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14.8
14.3
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80.0
76.8
69.5
81.3

29.2
30.0
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83.8
81.5
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34.0
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5.3
6.0

5.2
6.3

4.2
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6.6
6.4
6.2
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2.6
2.8
2.5
2.4
2.4
2.1
2.5
2.5
3.0
2.7
2.9

5.3
5.5

5.5
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4.2
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7.7

6.5
6.1
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2.6
2.8
2.4
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2.6
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2.8
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6.0
6.0
5.9
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6.2
5.6
5.9
5.7
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5.7

5.6
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7.0
7.8

7.8
6.4

7 .1

5.6

7.7
7.2
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2.7
2.6
2.9
2.6
2.7
2.3
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5.5
6.2
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36.7
38.6
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2.7
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6.8
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5.8
5.4
5.2
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3.5
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4.1
3.2
4.4
3.7
4.5
4.9
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12.8
11.3
12.3
13.9
13.2
13.0
12.8
12.0
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m

3.8

4.0
2.7
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3.7
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1.8
2.2
1.8
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1.8
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2.4
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2.5
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5.6
5.7
5.9
5.9
5.8
5.8
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37.3
37.2
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18.6
15.7
19.2
17.9
20.1
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19.3
21.3
24.5
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45.0
41.0
42.0
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43.2
40.6
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3.1
3.4
3.9
3.7
3.1
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3.9
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12.9
11.8
12.1
13.9
13.4
12.6
12.7
12.2
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3.6

2.7
2.9

3.8
4.3
4.4
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1.8
1.9
1.9
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15.4 14.2
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11.5 11.3
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1-4 from Bering Sea, 5-10 from Okinawa.
Body length and sex unknown. Identification tag was lost during transportation.
Each tip of wings cut off slightly.
Double of right or left half. One wing broken.

1410
1470
1610
1610
1540

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35.3
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4.2 35.7
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0.61
2.57
2.22
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2.05
1.15
1.17
2.25
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0.27
1.33
1.14
1.12
1.06
0.60
0.60
1.16
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1.62
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5 R
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BR
SL
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0.86
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1.35
1.42
I.58
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1.14
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1.39
2.08
1.65
2.17
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3.42
0.61
0.90
0.95
1.00
1.12
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0.73
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0.81
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I L

SR 12.4-19.I 12.2-11,r, 16.3-18.1 20,c>-2·1.9 2.1-[J,3 11.8-13.8 12.2-13.7 n.r.-9,8
SD
2SE

N

SU

15.0

20

N

SR

7.0

AM

lkC

7 .0

BbC

SR
SD
2SE

N

AM

SR 5.0-7.2
SD
0,63
2SD
0.35

AM

SR
SD
2SE

N

6.3-8.3
0.66
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7.4

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SR
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N

AM

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0.56
0.37
AM
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10
SR 5.0-7.7
SD
0.86
2SE
0.54

BbA

BpB

BpA

Species,
locality
BmA

APPENDIX 2. RESULTS OF CALCULATIONSAM Arithmetic mean,
N Sample number,
SR Sample range,
SD Standard deviation,
2SE Two standard errors.
See text for explanation of other abbreviation and calculation number

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170

H. OMURA

EXPLANATION OF PLATESThe photographs shown in the Plates were all taken from the ventral side. Details of the measurements
are shown in Appendix 1.
Plate I. The combined bone ofbasihyal and thyrohyals of the blue whale (pigmy) from the Antarctic (BmA).
Figs. 1-9 are the order of BmA 1-9.
Plate II. The combined bone of basihyal and thyrohyals of the fin whale from the Antarctic (BpA). Figs.
1-7 are the order of BpA 1-7, Fig. 8 BpA 9 and Fig. 9 BpA 10.
Plate III. Upper. The stylohyals of the blue whale (pigmy) from the Antarctic (BmA). Figs. 1-9 are theorder of BmA 1-9.
Plate III. Lower. The stylohyals of the fin whale from the Antarctic (BpA). Figs. 1-10 are the order of
BpA 1-10.
Plate IV. The combined bone of basihyal and thyrohyals of the fin whale from the Bering Sea (BpB).
Figs. 1-13 are the order ofBpB 1-13.
Plate V. The stylohyals of the fin whale from the Bering Sea (BpB). Figs. 1-13 are the order ofBpB 1-13.
Plate VI. The combined bone ofbasihyal and thyrohyals of the sei whale from the Antarctic (BbA). Figs.
1-9 are the order of BbA 1-9.
Plate VII. The stylohyals of the sei whale from the Antarctic (BbA). Figs. 1-7 are the order of BbA 1-7
and Fig. 8 BbA 9.
Plate VIII. The combined bone of basihyal and thyrohyals of the sei whale from the coast ofJapan (BbC).
Figs. 1-10 are the order of BbC 1-10.
Plate IX. The sytlohyals of the sei whale from the coast of Japan (BbC).
Figs. 1-10 are the order of
BbC 1-10.
Plate X. The combined bone ofbasihyal and thyrohyals of the Bryde's whale from the coast of Japan (BeC).
Figs. 1-12 are the order of BeC 1-12.
Plate XI. The combined bone of basihyal and thyrohyals of the Bryde's whale from the coast of Japan(BeC). Figs. 1-10 are the order of Bee 13-22.
Plate XII. The stylohyals of the Bryde's whale from the coast of Japan (BeC). Fig. 1 BeC 1, Fig. 2 BeC
2 and Figs. 3-15 are the order of BeC 10-22.
Plate XIII. The combined bone of basihyal and thyrohyals (Figs. 1-11) and stylohyals (Figs. 12-22) of theminke whale from the coast of Japan (BaC). Figs. 1-11 and Figs. 12-22 are the order of BaC 1-11
respectively.
Plate XIV. Upper. The combined bone of basihyal and thyrohyals of the humpback whale from theBering Sea and on the coast of Okinawa (MnB). Figs. 1-4 are the order of MnB 1-4, Fig. 5
MnB 6, Fig. 6 MnB 7, Fig. 7 MnB 9, Fig. 8 MnB 10, Fig. 9 MnB 12 and Fig. 10 MnB 13.
Plate XIV. Lower. Stylohyals of the humpback whale from the Bering Sea (MnB). Figs. 1-4 are the orderofMnB 1--4.
Plate XV. The combined bone of basihyal and thyrohyals (Figs. 1-5) and stylohyals (Figs. 6-9) of theblack right whale from the Bering Sea (EgB). Figs. 1-5 are the order of EgB 1-5 and Figs. 6-9
EgB 1-4.

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REVISION OF THE ARTICLE "TAXONOMICAL CONSIDERATION ON GENERA OF DELPHINIDAE" IN NO. 17
MASAHARU NISHIWAKII revealed my opinion on the genera of Delphinidae in the Scientific Reports of the
Whales Research Institute, No. 17. Some faults and misprints were found in it.
Accordingly, I would like to correct them.
Grampus was used as the scientific name of killer whale, but it should be changed
to Orcinus, and Grampidelphis of Risso's dolphin should be changed to Grampus. It
seems that Neomeris will better to be changed to Neophocaena.
Fortunately I could study on Cephalorhynchus and Sotalia recently in UnitedStates. According to the observation, Cephalorhynchus and Sotalia were consideredas the Delphinus type. The family Delphinidae, therefore, is consisted from the eight
genera as follows; Delphinus, Stenella, Sotalia, Cephalorhynchus, Lagenorhynchus, Tursiops, Steno and Lissodelphis.
Globidelphinidae could not use by the code, and the genus Grampidelphis waschanged to the genus Grampus again. I would like to suggest an idea a new family
Grampidae for the Risso's dolphin (Grampus griseus).
13 and 14, attached number of marks in the Fig. 1, should be exchanged eachothe_r.
Dentition and length/breath ratio of rostrum and skull on Globicephala andGrampidelphis in the page 103 of No. 17 should be exchanged their places.
I am considering that the suborders Mystacoceti and Odontoceti are reasonable
enough to be arised in the independent order respectively. However, I shall discuss
about this problem in next chance, because this paper is the information of thegenera and the families in the Odontoceti.
The key to the living families of Odontoceti should be changed as follows.

171

172

M. NISHIWAKIKEY TO THE LIVING FAMILIES OF ODONTOCETI
11

Tip oflower jaw ending an appreciable distance behind foremost part of head; lower teeth
functional, upper teeth rudimental and usually found in gum.
2 1 Head massive, 1/4 to 1/3 of body length; blowhole far foreward on head; functional
teeth large, 18 to 28 pairs confined to lower jaw ; dorsal fin an ill-defined lump ; flipper
rounded; size large (30 to 60 feet) ; lst cervical vertebra (atlas) free, 2nd (axis) to 7tli
cervical vertebrae fused.
Physeteridae
2 2 Head 1/6 of body length; functional teeth small, slender and curved, 9 to 16 pairs confined to lower jaw; dorsal fin well developed; flippers tapering; size small (9 to 13feet) ; all cervical vertebrae fused.
Kogiidai
12 Lower jaw extending at least as far as tip of snout; blowhole some distance from tip of snout.
3 1 Two conspicurous grooves forming a V-shape on the surface of throat blubber ; dorsal fin
present, considerably behind middle of body ; notch of tailflukes usually shallow orabsent ; foremost 3 or 4 cervical vertebrae fused.
;:,iphiidai
3 2 No grooving on throat ; dorsal fin when present at or near middle of body ; notch of
tailflukes conspicuous.
41 Seven cervical vertebrae all separate from one another.
5 1 Dorsal fin absent or rudimentary ; beak absent ; inhabits Arctic regeon.
Afonodontidai
5 2 Dorsal fin present but almost low; beak extremely long (1/6 to 1/7 of bodylengtli); inhabits fresh water in tropical or warmer region; teeth very numerous
in upper and lower jaws.
Platanistidat
4 2 Two or more cervical vertebrae fused.
6 1 Beak long and narrow (breath of snout less than 1/2 of its length) ; more than
20 teeth in each row of upper jaw; size small (less than 13 feet) ; usually lst (atlas)and 2nd (axis) cervical vertebrae fused.
Delphinidae
6 2 Head without distinct beak.
71 Only lst (atlas) and 2nd (axis) cervical vertebrae fused; less than 20 teeth ineach row of upper jaw ; size small.
Orcellidae
72 Not only atlas and axis fused, but also third or more cervical vertebrae fused.
Phocaenidat
8 1 Each row of upper teeth more than 15; body length less than 8 feet.
8 2 Each row of upper teeth less than 15 ; body length more than 8 feet.
Globicephalidae
9 1 Teeth present in upper jaw.
9 2 Teeth absent in upper jaw.
Grampidae

STUDIES ON THE LIPIDS IN BRAIN OF BLACK RIGHTWHALE IN THE NORTHERN PACIFIC OCEANHIDEO TSUYUKI* AND UHEI NARUSE**INTRODUCTION

fhere have been many works on lecithin contained in the brain of human andmammal living on land as well as on lecithin in the egg of hen. The works on lecithinin the brain of human and mammal were reported by Yokoyama & Suzuki (1932 ab)
md Levene & Rolf (1921, 1922). Reviewing the works on lecithin in the brain)f sea mammal, Igarashi & Zama (1955) studied on lecithin in the brain of sperm
whale (Physeter catodon) and Alaskan plolack (Theragra chalcogramma).
According to the works of lgarashi & Zama (1955), the characteristics of the.ecithin in the brain of sperm whale was as follows : Iodine value 71.5, Nitrogen:ontent 1.68%, Phosphorus content 3.61 %, Choline content 14.4%. Further the)resence of palmitic, stearic, oleic and eicosatetraenoic acids was confirmed and the)resence of C 20 , C 22 , and C 24 acids as saturated fatty acids and C 20 monoenoic
lcid as unsaturated fatty acids were presumed as the component fatty acids of:he lecithin.
In the present work, the writers have studied the properties of the acetone;oluble lipid and phospholipids in the brain of the black right whale in the Northern
Pacific Ocean.
It is pleasure that the writers express here their sincere thanks to Dr. Hideo'.)mura and Dr. Akio Shionoya for their kind advices and thanks to Mr. Seiji Ohsumi
who had kindly them the frozen brain of the black right whale.
EXPERIMENTS AND RESULTS

fhe operation such as the distillation and concentration of solvents were taken inltmosphere of nitrogen gas. Iodine value was measured by Wijs' method, N:ontent by micro-Kjeldahl method, P by method of Beveridge & Johnson (1958),~thanolamine and serine by method of Levine & Chargaff (1951), choline by Glick's
method (Glick, 1944) and inositol by method of Bohm & Picharz (1954).
l. Material
Material is the frozen brain of the black right whale, Eubalaena glacialis (male, bodyength: 15.1 m, presumed age: more than 9 years old) which was caught in the:outhern sea of Kojak Island in the Northern Pacific Ocean (N: 55°53'-54', W:

l54°4'-6').
*Department of Food Engineering, College of Agriculture & Veterinary Medicine, Nihon University,49, 3-chome, Shimouma-cho, Setagaya, Tokyo.
~*Dept. of Fisheries, Coll. of Agr. & Vet. Med., Nihon Univ.
173

174

H. TSUYUKI AND U. NARUSE

2. Preparation of Acetone-Soluble Lipid and Phospholipids
The acetone-soluble fraction was 5 times extracted from 500 g of the frozen brairwith 5 weights of acetone, and the obtained acetone-soluble fraction was 3 time
extracted with 5 weights of ethyl-ether. Then ethyl-ether was distillated off fronthe ethyl-ether extract and the acetone-soluble lipid was obtained from the 500 !
of the frozen brain. The properties of the acetone-soluble lipid are shown ii
Table 1.
TABLE I.

PROPERTIES OF ACETONE-SOLUBLE LIPID IN BRAIN
OF BLACK RIGHT WHALE

Yield

N~

g
%*
6.3
1.26
Phosphorus Nitrogen
(%)
(%)
0.03
0.02

1.4765Choline
(%)
0.01

Acid
value
2.6
Ethanolamine
(%)
0.01

Iodinevalue
142.1
lnsitol(%)
trace

Sapon.
value
183. lSerine(%)
0.02

Unsapon.
matter(%)
1.37
Sterol**(%)
18.62* % of acetone-soluble lipid from the frozen brain.
* * % of sterol in unsaponifiable matter by digitonin method.

The residue obtained after extracting the acetone-soluble lipid from the brai1
and the residue after extracting ethyl-ether-soluble fraction from the acetone-solubl,
fraction were mixed, and the mixture was 5 times extracted with 5 weights of chloro
form-methanol solution (2 : 1). The extract was 3 times treated by the washing oFolch, Ascoli, Leas, Mexth & Lebaron (1951), and the chloroform layer wa
separated and then chloroform was distillated off from the layer. Thus the phospnolipids were obtained. After all 2.1 g of phospholipids was obtained from th;material (Fig. 1). The properties of the phospholipids are given in Table 2.
TABLE 2.
Yield
%*
0.42

Nitrogen
(%)
1.81

N/P**

Choline/P**

Serine/P** Ethanolamine/P**

1.08

0.31

~

g

2.1
Inositol(%)
0.82

PROPERTIES OF PHOSPHOLIPIDS IN BRAIN

Phosphorus
(%)
3.72

0.24

Choline(%)
4.68

Ethanolamine
(%)
4.11

Serine
(%)
3.03

0.55

* % of phospholipids from the frozen brain.
* * molar ratio.

3. Component Fatty Acids of Acetone-soluble Lipid and Phospholipids
Mixed fatty acids were prepared from the acetone-soluble lipid and phospholipid
in the brain of the black right whale by alkali-hydrolysis.
The mixed fatty acids obtained from the acetone-soluble lipid were separatec
into two portions, solid and liquid fatty acids with lead salt-ethanol fractionatio1of Hilditch (1956) (Table 3). After synthesizing the acetal-ester of the solid fattacids with mono-brome-acetone, the acetal-ester of solid fatty acids were dissolved and heated in ethanol, and a little excess volume of 2N-HC1 methane
solution contained 2,4-dinitrophenylhydrazine were added to the above solutior:

LIPIDS OF BLACK RIGHT WHALE

175

Then 2,4-dinitrophenylhydrazone of acetal-ester was educed by cooling thissolution at the room temperature, and separated with filtration. Finally 2,4-dinitrophenylhydrazone of the acetal-ester was identified with paper chromatography
as its 2 % benzene solution by the method of Inoue, Hirayama & Noda (1956 a).
The results are shown in Table 4. The other hand the liquid fatty acids were con-'T'"1Extract wifh 5 weights of acetone 15 times)

Residue

Acefone exfract

Extract with 5 weightsof ethyl-efher 13 times J

Residue

Acefone-soluble lipid

Extract with 5 weighfs ofchloroform/mefhanol 12: l I. solufion 15 times I

ResidueldiscardJ
Folch's washing

Chloroform soluble
fraction(3 times}

Methanolsolution!discard I

Phospholipids

Fig. 1.

Extraction and fractionation of lipids from brain of balck right whale.

verted into the methyl ester of the fatty acids by the usual method. Mercuric
acetate was added to the methyl ester of the fatty acids in methanol by method of
Noda, Hirayama & Inoue (1956), and the liquid fatty acids were indentified with

176

H. TSUYUKI AND U. NARUSE

paper chromatogaphy as their mercuric acetate complexes of methyl ester (Table

5).
TABLE 3.

FRACTIONATION OF MIXED FATTY ACIDS OBTAINED FROMACETONE-SOLUBLE LIPID
Iodine value
Kinds of fatty acids
Neutr. value%
151.2
Mixed fatty acids
191.8
Solid fatty acids
38.6
200.2
10.3
Liquid fatty acids
61.4
183.4
200.3

TABLE 4. RF VALUE OF 2,4-DINITROPHENYLHIDRAZONES OF ACETAL ESTER
OF COMPONENT SATURATED ACIDS OF ACETONE-SOLUBLE LIPID
Acid
SampleAcetone soluble lipid
Standard

Myristic
0.35

Palmitic
0.29
0.29

Stearic
0.22
0.23

Arachidic
0.15
0.16

Behenic
0.10
0.11

Paper: Toyo No. 2. Moving phase: methanol-acetic acid-tetralin (l"O: 2: 1).
Stationary phase: Tetralin. Development: Ascending at30°C. Detection: N/2 KOH
in ethanol.
TABLE 5. RF VALUE OF MERCURIC ACETATE COMPLEXES OF
METHYLESTER OF COMPONENT LIQUID ACIDS OF ACETONE-SOLUBLE
LIPID
Acid
SampleAcetonesoluble lipid
Standard

Zoomaric
0.26
0.25

Oleic
0.14
0.16

Eicosenoic
0.09
0.09

Erucic0.05
0.05

Linoleic
0.51
0.52

Stationary and moving phase were the same as shown in Table 4.
0.2% dinitrocarbazone in ethanol.

Linolenic
0.70
0.71

Detection :While para-bromophenacyl bromide were added into the methanol solution
contained 20mg of the mixed fatty acids (Table 6) separated from the phospholipids,
and the solution was heated for two hours in water bath and then cooled, 2N-HC1
methanol solution contained 1 % 2,4-dinitrophenylhydrazine was added into theabove cooled solution, and the solution was set on for 3 hours at room temperature.
TABLE 6.

PROPERTIES OF MIXED FATTY ACIDS OBTAINED FROMPHOSPHOLIPIDS

%
62.38

Neutralization value
155.3

Iodine value
190.1

Thus para-bromophenacyl-ester-2,4-dinitrophenylhydrazine of the fatty . acids
was synthesized. This ester was extracted with ether. After the extracted solution was washed with water, the water in the solution was removed with anhydrous
sodium sulfate and the ether solution was divided into two portions. After eachportion of the ether solution was concentrated to 1 ml, anhydrous methanol solution
contained mercuric acetate was added to one portion. The solution was heatedfor 40 minutes at 40°C and cooled. Then 1 ml of benzene, lOml of water and one

177

LIPIDS OF BLACK RIGHT WHALE

drop of acetic acid were added into the above solution, the benzene-ether solution
was produced on the upper layer. This solution was called as Sample B. To anotherportion, benzene, water and acetic acid were added by the same method mentioned
above except mercuric acetate, thus sample A was prepared. The sample A and
B of complexes of fatty acids were treated with paper chromatography of Inoue,
Hirayama & Noda (1956 b.) Rf value of the sample A and B are shown in
Table 7 and 8.
TABLE 7.

RF VALUE OF SAMPLE A OF MIXED FATTY ACIDS OBTAINEDFROM PHOSPHOLIPIDS BY BROMOZONE METHOD.
Acid
SamplePhospholipids
Standard

Myristic
0.34
0.35

Palmitic
0.27
0.29

Stearic
0.23
0.23

Arachidic
0.18
0.17

Behenic
0.12

Oleic
0.25
0.26

Paper: Toyo No. 2 (40 X 40 cm). Stationary phase: Petroleum hydrocarbon (b.p.
140-170°C). Moving phase: Methanol-Acetic acid-Petroleum hydrocarbon (5: l: l).
Ascending at 30°C. for 5 hours.
TABLE 8.

RF VALUE OF SAMPLE B OF MIXED FATTY ACIDS OBTAINEDFROM PHOSPHOLIPIDS BY BROMOZONE METHOD
Acid
SamplePhospholipids
Standard

Zoomaric
0.55
0.57

Oleic
0.51
0.51

Eicosenoic
0.46
0.47

Erucic0.41
0.39

Linoleic
0.73
0.72

Linolenic
0.68
0.69

Paper, ascending method, stationary and moving phase were the same as shown in
Table 7.

4.

Silca Gel Column Chromatography and Silicic Paper Chromatography of
Phospholipids
Phospholipids in the brain of black right whale were fractionated with silica gelcolumn by Rhodes' method (Rhodes & Dawson, 1960). At first, 40 g of silica gel(Kanto-kagaku Co.) being suspended in methanol, the silica gel-methanol solution
was poured into glass column fulled with glass-fiber for chromatography (30 X
1.7 cm), and set until the silica gel was sunk down. Then the solution was flowed
down by opening the glass cock of the column. Directly before the surface of thesolution reached to the top of silica gel column, the column was washed with2 volumesof chloroform. When 2-3ml of chloroform was remained on the top of the silica
gel column, the cock was closed. Next, the chloroform solution contained 100 mg
of phospholipids was added into the column mentioned above. Various phospholipids were eluted with various methanol-chloroform solvents (Table 9). The
properties of each phosphlipid are shown in Fig. 2 and Table 10.
Morever, the phospholipids were treated with silicic paper chromatography(Rhodes & Dawson, 1960) to separate each phospholipid. After the filter paper
for chromatography (Toyo No. 51) was immersed in sodium silicate solution(sodium silicate: water/I : 1) for 5 minutes, the paper was suspended in air for 5
minutes and the excess solution was removed from the paper. Further the paper

178

H. TSUYUKI AND U. NARUSE
TABLE 9. SOLVENTS FOR FRACTIONATION OF PHOSPHOLIPIDStS im
Kinds of phospholipids
Chloroform : Methanol
Volume(ml)~she<
25Polyglyceroric acid90: 10ern1
15Phosphatidyl serine and Phoshatidyl ethanolamine 1
80: 20ared
Phosphatidyl ethanolamine50
75: 25·eatt
Monophosphoinositide25
60:40
Phosphatidyl choline
50:50
75
Sphingomyelin and phosphatidyl choline
10: 9025

TABLE 10.

PROPERTIES OF EACH FRACTION OBTAINED FROM PHOSPHOLIPIDS
BY SILICA GEL COLUMN CHROMATOGRAPHY
Fraction

Component
Phosphorus (%)
Nitrogen (%)
Choline (%)
Ninhydrin
Inositol
N/P*
Choline/P** Molar ratio

1
3.31
0.23

0.15

2
3.72
1.62

3
3.70
1.61

4
3.34
0.39

5
3.36
1.66
12.40

6
3.67
3.34
11.30

+

+

+
+

+
+

+

0.95

0.96

0.25

0.99
0.87

2.01
0.83

f(µg)

!5

20

25

30

35

f-90: 10.fso:2of---1s: 25----:-60:.10-:- s o :25Fig. 2.

15

50

25

75

T.be

so--: o: o~~ !~~:orc!o,~:-,,,·~or.ol]
i

i

25

ml

Silicic column chromatography of phospholipids.

RF VALUE OF PHOSPHOLIPIDS BY SILICIC PAPER
CHROMATOGRAPHY
ComponentStandard
SamplePhosphatidic acid
0.72
Phosphatidyl ethanolamine
0.56
0.54
Phosphatidyl serine
0.52
0.51
Phosphatidyl choline
0.33
0.33
Sphingomyelin
0.23
0.22
Inositol phosphatide
0.20
0.18
Development: di-isobutylketone: acetic acid: water (40: 25: 5), ascending at room
temperature for 12 hours.
Detection : all lipids-rhodamin 6G, phosphatidyl choline and sphingomyelinmolibdic phosphate, phosphatidyl ethanolamine and phosphatidyl serine-ninhydrin,
inositol phosphatide-Elson-Morgan reagent.

TABLE 11.

\s

:ig1
an
se1
oi
li
c

LIPIDS OF BLACK RIGHT WHALE

179

was immersed in dilute HCl solution for 30 minutes. Then the paper was 5 times
washed with water in order to remove the HCI. After setting the paper in air
overnight, the paper was dried for one hour at ll0°C. The silicic paper was prepared by the process above mentioned. The result of chromatography which wastreated with this silicic paper was shown in Table 11.
DISCUSSION

As has been shown in Table 1, the acetone-soluble lipid in the brain of the blackright whale contained a trace of nitrogen, phosphorus, choline, ethanolamine, serine
and its acid value and unsaponifiable matter content were lower. Therefore it
seems that the main constituent of acetone-soluble lipid is glyceride, and the contents
of free fatty acid and unsaponifiable matter are little. The yield of acetone-soluble
lipid was 1.26% to the frozen brain of the whale, and was comaratively lower. The
content of sterol in unsaponifiable matter was 18.62 %. The paper chromatography
by the method of Inoue, Hirayama & Noda (1956 a) and Noda, Hirayama &Inoue (1956), indicated that palmitic, stearic, arachidic and behenic acids as saturated fatty acids, and zoomalic, oleic, eicosenoic, erucic, linoleic and linolenic acids
as unsaturated fatty acids were contained in the acetone-soluble lipid (Table 4, 5).
M yristic acid was unable to be found in the aceone-soluble lipid in the brain.
The yield of phospholipids obtained from the brain of the whale was 0.42 %.
The properties of the phospholipids were as follows : choline content 4.68 %,ethanolamine content 4.11 %, serine content 3.03% and inositol content 0.82%(Table 2). According to the bromozone method of Inoue, Hirayama & Noda (1956b), component fatty acids of the phospholipids seemed to be myristic, palmitic,
stearic and arachidic acids as saturated fatty acids, and zoomaric, oleic, eicosenoic,
erucic, linoleic and linolenic acids as unsaturated fatty acids. However, the presence ofbehenic acid was not able to be found in the phospholipids.
When the component fatty acids of the acetone-soluble lipid and phospholipids
were compared, the presence of palmitic, stearic and arachidic acids were found inboth lipids in the case of saturated fatty acids, but myristic acid was not containedin the acetone-soluble lipid and behenic acid was not able to be found in thephospholipids. Considering of the component unaturated fatty acids, their component acids were common to both lipids and the presence of zoomaric, oleic,eicosenoic, erucic, linoleic, linolenic acids were observed in the case of both lipids.
Perhaps, various component unsaturated fatty acids seemed to be contained in phospolipids in the whale brain. The results of silica gel column chromatography
by Rhodes' method indicated the presence of phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl choline, sphingomyelin and inositol phosphatide
was observed in the phospholipids. But phosphatidic acid was not able to foundin the phospholipids (Table 11).

180

H. TSUYUKI AND U. NARUSE

SUMMARYI) The characteristics of the acetone-soluble lipid and phospholipids in thebrain of black right whale in the Northern Pacific Ocean were studied.
2) The yield of acetone-soluble lipid obained from the frozen brain was 1.26 %and sterol content in unsaponifiable matter was 18.62 %. The results of paper
chromatography by the methods of Inoue, Hirayama & Noda (1956 a) and Noda,
Hirayama & Inoue (1956) indicated that the presence of palmitic, stearic, arachidic,
zoomaric, oleic, eicosenoic, erucic, linoleic and linolenic acids in the acetonesoluble lipid.
3) The yield of phospholipids obtained from the frozen brain was 0.42 %.
The results of the bromozone method indicated the presence of myristic, palmitic,
stearic, arachidic, zoomaric, oleic, eicosenoic, erucic, linoleic and linolenic acids inthe phospholipids.
The results obtained by the silica gel column chromatography and silicic paper
chromatography indicated the presence of phosphatidyl ethanolamine, phosphatidylcholine, inositol phosphatide, polyglyceroric acid, phosphatidyl serine and sphingomyelin in the phospholipids.
REFERENCES
BEVERIDGE, J.M.R. & JOHSON, S.E. (1958). "Biochemistry ef Lipid", Kyoritsu-Syuppan Co. Tokyo, 311.
BoHM, P. & G. PICHARZ (1954). Von Quantitative Bestimmung Von Inosit in Phosphstiden, ..(:'. Phisiol.
Chem., 298: 110-120.
FoLCH, J., I. Ascou, M. LEAS, J.A. MEXTH & F.M. LEBARON (1951). Preparation of Lipide Extracts
from Brain Tissue, J. Biol. Chem., 191 : 833-841.
GLICK, D. (1944). Concerning the Reineckate Method for the Determination of Choline, J. Biol. Chem.,
156: 643-651.
HILDITCH, T.P. (1956). " The Chemical Constitution of Natural Fats (3rd. ed.) " Champan & Hall, London, 574.
IGARASHI, H. & ZAMA, K. (1955). Studies on the Phosphatide of Aquatic Animals. Part 2. Nippon Nogeikagakukaishi, 29: 958, 961.
INOUE, Y., HIRAYAMA, O. & NODA, M. (1956·a). Paper Chromatography of Fatty Acids as their Acetal
Ester Derivatives, J. Japan Oil Chemists' Soc., 5: 16.
- - (1956· b). Separation and Identification of Fatty Acids. Part XX. Bull. Agr. Chem. Soc. Japan.
20 : 200-205.
LEVENE, P.A. & ROLF, I.P. (1921). Lecithine 4-Lecithine of the Brain, J. Biochem. 46: 353-65.
- - (1922). Unsaturated Fatty Acids of the Brain Lecithines, J. Biochem. 54: 99-100.
LEVINE, C. & E. CHARGAFF. (1951). Chromatographic Behavior of Analogues of the Nitrogenous Lipide
Constitutes, J. Biol. Chem., 192: 481-483.
NODA, M., HIRAYAMA, O. & INOUE, Y. (1956). Separation and Identification of Fatty Acids, Part XIX.
Nippon Nogeikagakukaishi, 30 : 106-111.
RHODES, D. N. & DAWSON, R.M.C. (1960). "Chromatographic and Electrophoretic Technique 1." 363 p.
New York.
YOKOYAMA, Y. & SuzuKI, B. (1932·a). Phospholipids in Human Brain-2, P.I.A. Japan 8: 375-60.
- - (1932·b). Phospholipids in Human Brain-3, P.I.A. Japan, 8: 361-3.

THE SCIENTIFIC REPORTS OF THE WHALES RESEARCHINSTITUTE, TOKYO, JAPANNUMBER 1, JUNE 1948
Akiya, S. and Tejima, S. Studies on Digestive Enzyme in Whale. 3-7
Akiya, S., Ishikawa, Y., Tejima, S. and Tanazawa, T. Studies on Tryptase from a Whale (Balaenoptera
borealis L.) 8-10
Akiya, S., Tejima, S. and Ishikawa; Y. Studies on the Utilization of Whale Meat by the use of Pancreatic
Tryptase of Whales. 11-14
Akiya, S. and Kobo, F. The Test Culture of Some Microorganisms with Whale Meat Peptone. 15-16
Nakai, T. Chemical Studies on the Freshness of Whale Meat. I. Evaluation of Freshness and Changes
in Quantity of Several Kinds of Nitrogen in Whale Meat Following Deterioration of Freshness. 17-26
Nakai, T. Chemical Studies on the Freshness of Whale Meat. II. On Comparison between Whale Meatand Beef on Deteioration·of Freshness and Autolysis. 27-30
Tawara, T. On the Simultaneous Extraction of Vitamin A-D and Vitamin B2 Complex from the Liver ofa Fin Whale (Nagasu-Kujira, Balaenoptera physalus L.). 31-37
Tawara, T.. Studies on Whale Blood. I. On the Separation of Histidine from Whale Blood. 38-40
Nakai,]: and Shida, T. Sinus-hairs of the Sei-Whale (Ealaenoptera-borealis). 41-47

NUMBER 2, DECEMBER 1948
Ogawa, T. and Arifuku, S. On the Acoustic System in the Cetacean Brains. 1-20
Yamada, M. Auditory Organ of the Whalebone'Whales. (Preliminary Report). 21-30
Nakai, T. Chemical Studies on the Freshness of Whale Meat. III. Effect of Hydrogen-ion Concentration
on Decrease in Freshness and Titration Curve of Whale Meat with HC! and Na 2C0 3 • 31-34
Ishikawa, S., Omote, Y. and Soma, Y. Analytical Distillation of Vitamin A in the Wt,.lle Liver Oil. 35-41
Ishikawa, S., Omote, Y. and Kanno; H. Molecular :OistiJlation of Sperm Whale Blubber Oil. 42-45
Kaneko, A. Molecular Distillation of Fin Whale Liver Oil. 46-50
Akiya, S. and Takahashi, K. Determination of Tryptophane in Whale Meat. 51-54
Ishikawa, Y. and Tejima, S. Protein Digestive Power of Sperm Whale Pancreatic Enzyme. 55-60
Tsukamoto, S. Experiment on Digestion of Whale Meat by Koji-mould. 61.-66

NUMBER 3, FEBRUARY 1950
Ogawa, T. and Shida, T. On the Sensory Tubercles of Lips and of Oral Cavity in the Sei and the Fin
Whales. 1-16
Ohe, T. Distribution of the Red ]\farrow in Bones of the Fin Whale. 17-22
Hosokawa H. On the Cetacean Larynx, with Special Remarks on the Laryngeal Sack of the Sei Whale andthe Aryteno-Epiglottideal Tube of the Sperm Whale. 23-62
Akiba, T., Tsuchiya, T., Umehara, :M. and Natsume, Y. Bacteriological Studies on Freshness of Whale
Meat. (Report No. 1). 63-70
Ishikawa, Y. Protein Digestive Power of Sperm Whale Pancreatic Enzyme. II. 71-78
Mori, T. and Saiki, M. Properties of Fats and Oils Contained in Various Parts of a Sperm Whale Body.
79-84
Tawara, T. and Fukazawa, R. Studies on Kitol. I. Preparation of Kitol from Whale Liver Oil. 85-88
Tawara, T. and Fukazawa, R. Studies on Kitol. II. Influence ofKitol Fraction on the Determination of
the International Unit of Vitam!n A. 89-91
Tawara, T. and Fukazawa, R. Studies on Kitol. III. The effect of Sunlight, Air and Heat on the Vitamin
A and Kitol Fractions. 92-95

I
I

Tawara,T. Ont
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1
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Mizue,K.andJimbo,H. S
t
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2
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9
0

NUMBER 4, AUGUST 1950
Omura,H. OntheBodyWeighto
fSpermandSeiWhalesl
o
c
a
t
e
di
nt
h
eAdjacentWaterso
fJapan. 1‑
1
3
Omura,H. DiatomI
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nt
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6
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h
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t・
w
a
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r
so
fJ
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. 27‑113
N
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,M. D
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m
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a
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,M. OntheBodyWeighto
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s
. 1
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0
9

NUMBER 5,JUNE 1951
A
k
i
b
a
,T
.
,Umehar品， M.a
ndNat
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R
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No. I
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Hosokawa,H. Ont
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. 71‑79
Mizuc,K. Foodo
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fJ
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)
. 31‑90
N
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)Caughtbyt
heJapaneseA
n
t
a
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t
i
cWhalingFleets. 91‑167、

NUMBER 6,DECEお1BER 1951
Hosokawa,H. Ont
h
eE
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s
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iii
Omote, Y. Complete Recovery of Vitamin A from Molecular Distillation Residue of Whale-liver Oil. 187191
Omote, Y. Chemical Structure of Kitol (I). Double Bonds and Hydroxyl Groups. 193-198
Hirata, Ivf. Experimental Investigation on Flattened Head Harpoon an Attempt for Restraining Ricochet.
199-207

NUMBER 7, JULY 1952
Ogawa, T. On the Cardiac Nerves of Some Cetacea, with Special Reference to those of Berardius bairdii
Stejneger. 1-22
Akiya, S., Hoshino, 0. and Motohashi, N. On an Attempt to Preserve Whale Meat Freshness with 5Nitrofurfuriden Aminoguanidine from Decay. 23-30
Akiya, S. and Sawamura, R. Colorimetric Determination of 5-Nitro-2 furfurdiene Aminoguanidine. 31-36
Tomiyama, S. and Takao, M. Studies on Utilization of Higher Fatty Alcohol from Sperm Whale Oil.
37-46
Omote, Y. A Rapid Method for the Separate Determination of Vitamin A and Kitol in the Whale-liver
Oil. 47-50
Arai, Y. and· Sakai, S. Whale Meat in Nutrition. 51-67
Yamaguchi, K. and.Fujino, K. On the Serological Constitution of Striped Dolphin (Prodelphinus caeruleoalbus (Meyen)) (I.) 69-77
Nishimoto, S., Tozawa, M. and Kawakami, T. Food of Sei Whales (Balaenoptera borealis) Caught in the
Bonin Island Waters. 79-85
Nishiwaki, !VI. On the Age-Determination of Mystacoceti, Chiefly Blue and Fin Whales. 87-119
Nishiwaki, M. and Hibiya, T. On the Sexual Maturity of the Sperm Whales (Physeter catodon) Found in the
Adjacent Waters of Japan (II). 121-124
Ohno, M. and Fujino, K. Biological Investigation on the Whales Caught by theJapanese Antarctic Whaling
Fleets, Season 1950/51. 125-188

NUMBER 8, JUNE 1953
Yamada, M. Contribution to the Anatomy of the Organ of Hearing of Whales. 1-79
Omura, H. Biological Study on Humpback Whales in the Antarctic Whaling Areas IV and V. 81-102
Fujino, K. On the Serological Constitution of the Sei-, Fin-, Blue- and Humpback-Whales (I). 103-125
Ogawa, T. On the Presence and Disappearance of the Hind Limb in the Cetacean Embryos. 127-132
Nishiwaki, M. and Yagi, T. On.the Age and the Growth of Teeth in a Dolphin, Prodelphinus caeruleo-albus).
(I). 133-146
Kakuwa, Z., Kawakami, T. and Iguchi, K. Biological Investigation on the Whales Caught by the Japanese
Antarctic Whaling Fleets in the 1951-52 Season. 147-213
Nishiwaki, M. Hermaphroditism in a Dolphin (Prodelphinus caeruleo-albus). 215-218

NUMBER 9, JUNE 1954
Akiya, S., Hoshino, 0. and Motohashi, N. Attempt to Preserve Freshness of Whale Meat with Germicides.
II. 1-10
Ogawa, T. On the Musculature of the Sinus Venosus and its Continuation with the So-called Conducting
System of the Whale's Heart. 11-35
Yamada, M. Some Remarks on the Pygmy Sperm Whale, Kogia. 37-58
Yamada, M. An Account of a Rare Porpoise, Feresa Gray from Japan. 59-88
Omura, H. and Fujino, K. Sei Whales in the Adjacent Waters of Japan. II. Further Studies on theExternal Characters. 89-103:fujino, K. On the Serological Constitution of the Sperm- and Baired Beaked-Whales (I) Blood Groups

ivof the Sperin- and Baired Beaked-Whales. 105-120
Fujino, K. On the Body Proportions of the Fin Whales (Balaenoptera physalus (L) Caught in the Northern
Pacific Ocean (I) (Preliminary Report). 121-163
Nishiwaki, M., Hibiya, T. and Kimura, S. On the Sexual Maturity of the Sei Whale of the Bonin waters.
165-177
Uda, M. Studies of the Relation between the Whaling Grounds and the Hydrographical Conditions (I).
179-187

NUMBER 10, JUNE 1955
Hosokawa, H. Cross-Section of a 12 mm. Dolphin Embryo. 1-68
Nemoto, T. White Scars on Whales (I) Lamprey Marks. 69-77
Omura, H. and Nemoto, T. Sei Whales in the Adjacent Waters of Japan: III. Relation between Movement and Water Temperature of the Sea. 79-87
Omura, H., Fujino, K. and Kimura, S. Beaked Whale Berardius bairdi ofJapan, with Notes onZiphius cavirostris.
89-132
Fujino, K. On the Body Weight of the Sei Whales Located in the Adjacent Waters ofJapan (II). 133-141
Nishiwaki, M. On the Sexual Maturity of the Antarctic Male Sperm Whale (Physeter. catodon L.) 143-14!:>
Ohta, K. and Others. Composition of Fin Whale Milk. 151-167

NUMBER 11, JUNE 1956
Omura, H. and Sakiura, H. Studies on the Little Piked Whale from the Coast of Japan. 1-37
Nishiwaki, M., Hibiya, T. and Kimura, S. On the S.exual Maturity of the Sperm Whale (Physeter catodon)
Found in the North Pacific. 39-46
Fujino, K. On the Body Proportions of the Sperm Whales (Physeter catodon). 47-83
Fujino, K. On the Serological Constitution· of the Fin Whales II. Further Studies on Blood Groups.
85-98
Nemoto, T. On the Diatoms of the Skin Film of Whales in the Northern Pacific. 99-132
Hoshina, T. and Sugiura, Y. On a Skin Disease and a Nematode Parasite of a Dolphin, Tursiops truncatus(Montagu, 1821). 133-138
Iwai, E. Descriptions on Unidentified Species of Dibranchiate Cephalopods. I. An Oegopsiden Squid
belonging to the Genus Architeuthis. 139-151
Iwai, E. Descriptions on Unidentified Species of Dibranchiate Cephalopods. II. A Cranchiidae Squidof the Genus Taonius. 153-161
Uda, M. and Nasu, K. Studies of the Whaling Grounds in the Northern Se~-Region of the Pacific Ocean
in Relation to the Meteorological and Oceanographic Conditions. (Part I). 163-179
Kimura, S. and Nemoto, T. Note on a Minke Whale Kept Alive in Aquarium. 181-189
Ishikawa, Y. A Characteristic Property of Whale Oils concerning the Absorption of Gases. I. On theAbsorption of Carbon Dioxide by Whale Oils. 191-213

NUMBER 12, JUNE 1957
Omura, H. Osteological Study of the Little Piked Whale from the Coast of Japan. 1--21
Nishiwaki, M. Age Characteristics of Ear Plugs of Whales. 23-32
Nemoto, T. Foods of Baleen Whales in the Northern Pacific. 33-89
Nasu, K. Oceanographic Conditions of the Whaling Grounds in the Waters Adjacent to Aleutian Islands
and the Bering Sea in Siimmer of 1955. 91-101
Kimura, S. The Twinning in Southern Fin Whales. 103-125
Ichihara, T. An Application of Linear Discriminant Function to External Measurements of Fin Whale.
127-189

v

Nishiwaki, M. Very Small Embryo of Cetacea. 191-192
Nishiwaki, M. One-eyed Monster of Fin Whale. 193-195
Ogawa, T. and Kamiya, T. A Case of the Cachalot with Protruded l<.udimentary Hind Limbs. 197-208
Uda, M. and Dairokuno, A. Studies of the Relation between the Whaling Grounds and the Hydrographic
Conditions. (II) A study of the Relation between the Whaling Grounds offKinkazan and the Boundaryof Water Masses. 209-224
Abe, T. Notes on Fishes from the Stomachs of Whales Taken in the Antarctic. I. Xenocyttus nemotoi, a New
Genus and New Species of Zeomorph Fish of the Subfamily Oreosominae (Goode and Bean, 1895). 225233
Tsuyuki, H. On the Oils Contained in Various Blubbers of Northern Elephant Seal, .i\1irounga angustirostris.
235-240NUMBER 13, SEP'J;'EMBER 1958
Omura, H. North Pacific Right Whale. 1-52
Nishiwaki, M. and Kamiya, T. A Beaked Whale Mesoplodon Stranded at Oiso Beach, Japan. 53-83
Nishiwaki, M. and Randa, C. Killer Whales Caught in the Coastal Waters off Japan for Recent 10 Years.
85-96
Ohsumi, S. (Kimura) Nishiwaki, M. and Hibiya, T. Growth of Fin Whale in the Northern Pacific. 97-133
Nishiwaki, M., Hibiya, T. and Ohsumi, S. (Kimura). Age Study of Sperm Whale Based on Reading ofTooth Laminations. 135-153
Nishiwaki, M., Ichihara, T. and Ohsumi, S. (Kimura). Age Studies of Fin Whale Based on Ear Plug.
155-169
Fujino, K. On the Serological Constitution of Fin Whale III. Human B Blood Group Substances in Erythrocytes and Some Notes on Anti-fin Ju Specific Antibodies. 171-184
Nemoto, T. Cocconeis Diatoms Infected on Whales in the Antarctic. 185-191.
Nemoto, T. and Nasu, K. Thysanoessa macrura as a Food of Baleen \'\Thales in the Antarctic. 193-199
Ichihara, T. Gray Whale Observed in the Bering Sea. 201-205
Ohsumi, S. (Kimura). A Descendant of Moby Dick or a White Sperm Whale. 207-209
Nasu K. Deformed Lower Jaw of Sperm Whale. 211-212
Omura, H. Note on Embryo of Baird's Beaked Whale. 213-214
Uda, M. and Suzuki, N. Studies of the Relation between the Whaling Grounds and the Hydrographic
Conditions. III. 215-229
Seki, Y. Observations on the Spinal Cord of the Right Whale. 231-251
Kamiya, T. How to Count the Renculi of the Cetacean Kidneys, with Special Regard to the Kidney of theRight Whale. 253-267
Hosokawa, H. and Sekino, T. Comparison of the Size of Cells and Some Histological Formations between
Whales and Man. 269-301
Ogawa, T., Tsunoda, T. and Osawa, M. Amino Acid Composition of Whale Meat. 303-307
Ishikawa, Y. A Characteristic Property of Whale Oils Concerning the Absorption of Gases II. On theAbsorption of Nitrogen by Whale Oils. 309-321
Tsuyuki, H. Component Fatty Acids of Northern Elephant Seal Oil. 323-332

NUMBER 14, SEPTEMBER 1959
Omura, H. Bryde's Whales from the Coast of Japan. 1-33
Nishiwaki, M. and Kamiya, T. Mesoplodon stejnegeri from the Coast of Japan. 35-48="l"ishiwaki, M. Humpback Whales in Ryukyuan Waters. 49-87
Cushing, John E., Fujino, K. and Takahashi., K. Glycerol-freezing Technique as an Aid in Blood Typingof Whales. 89-100
Fujino, K. and Cushing, John E. Blood Typing of Dried Whale Erythrocytes with 131 1 Labelled Antibody.
101-106

vi
Ichihara, T. Formation Mechanism of Ear Plug in Baleen Whales in Relation to Glove-finger. 107-135
Nasu, K. Surface Water Condition in the Antarctic Whaling Pacific Area in 1956-57. 137-143
Ohsumi, S. (Kimura). A Deformed Fin Whale Fetus. 145-147
Nemoto, T. Food of Baleen ''\'hales with Reference to Whale 1\fovements. 149-290
Yamada; M. and Yoshizaki, F. Osseous Labyrinth of Cetacea. 291-304
Nakai, T. Distribution of Amino Acid in Proteins from Various Parts of Whale Body. 305-326

NUMBER 15, NOVEMBER 1960
Nishiwaki, M. Ryukyuan humpback whaling in 1960. 1-16
Ohsumi, S. Relative growth of the fin whale, Balaenopteraphysalus (Linn.). 17-84
Fujino, K. Immunogenetic and marking approaches to identifying subpopulations of the North PacificWhales. 85-142
Nasu, K. Oceanographic investigation in the Chukchi sea during the summer of 1958. 143-158
Tokita, K. and ECG Research Group. Electrocardiographical studies on Bottlenosed dolphin (Trusiops
truncatus). 159-165

NUMBER 16, MARCH 1962
Omura, H. Bryde's whales occurs on the coast of Brazil. 1-5
Omura, H. Further information on Bryde's whales from the coast of Japan. 7-18
Nishiwaki, M. Ryukyuan whaling in 1961. 19-28
Nemoto, T. A secondary sexual character of fin whales. 29-34
Omura, H., Nishiwaki, M., Ichihara, T. and Kasuya, T. Osteological note of a sperm whale. 35-45
Ichihara, T. Prenatal dead foetus of baleen whales. 47-60
Nishiwaki, M. Mesoplodon bowdoini stranded at Akita beach, Sea of Japan. 61-77
Nishiwaki, M. Observation on two mandibles of Mesoplodon. 79-82
Sinclair, John. An early dolphin embryo (Stenella caeruleoalbus) in serial sections. 83-87
Nemoto, T. Food of ballen whales collected in recent Japanese antarctic whaling expeditions. 89-103
Uda, M. Subarctic oceanography in relation to whaling and salmon fisheries. 105-119

NUMBER 17, FEBRUARY 1963
Nishiwaki, M., Ohsumi, S. and Maeda, Y. Change of form in the sperm whale accompanied with growth.
1-14
Ohsumi, S., Kasuya, T. and Nishiwaki, M. The accumulation rate of dentinal growth layers in the maxillary
tooth of the sperm whale. 15-35
Ichihara, T. Photometric method for counting laminae in ear plug of baleen whale. 37-48
Yoshikawa, T. and Suzuki, T. The lamination of the masseter of the humpback whale. 49-52
Fujino, K. Intra-uterine selection due to maternal-foetal incompatibility of blood type in the whales. 53-65
Cushing, J.E., Fujino, K. and Calaprice, N. The Ju blood typing system of the sperm whales and specificsoluble substances. 67-77
Nemoto, T. New records of sperm whales with protruded rudimentary hind limbs. 79-81
Nemoto, T. and Nasu, K. Stones and other aliens in the stomachs of sperm whales in the Bering Sea. 83-91
Nishiwaki, M. Taxonomical consideration on Genera of DeljJhinidae. 93-103
Nasu, K. Oceanography and whaling ground in the subarctic region of the Pacific Ocean. 105-155
Nemoto, T. Some aspect of the distribution of Calanus cristatus and C. plumchrus in the Bering and its neighbouring waters, with reference to the feeding of baleen whales. 157-170
TsuYUKI, H. and Naruse, U. Studies on the oil of black right whale in the northern Pacific Ocean. 171-190
Yagi, T., Nishiwaki, M. and Nakajima, M. A preliminary study on method of time marking with lead-salt
and tetracycline on the teeth of northern fur seal. 191-195

vii

NUMBER 18, MARCH 1964
Fujino, K. Fin whale subpopulations in the Antarctic whaling areas II, III and IV. 1-28
Ichihara, T. Prenatal development of ear plug in baleen whales. 29-48
Ohsumi, S. Examination on age determination of the fin whale. 49-88
Nemoto, T. School of baleen whales in the feeding areas. 89-110
Okutani, T. & Nemoto, T. Squids as the food of sperm whales in the Bering Sea and Alaskan Gulf.
111-122
Ohsumi, S. Comparison of maturity and accumulation rate of corpora albicantia between the left andright ovaries in Cetacea. 123-148
Omura, H. A systematic study of the hyoid bones in the baleen whales. 149-170
Nishiwaki, M. Revision of the article "Taxonomical consideration on genera of Delphinidae" in No. 17.
171-172
Tsuyuki, H. & Naruse, U. Studies on the lipids in brain of black right whale in the northern Pacific
Ocean. 173-180

昭 和 39年 3月 20 日 印 刷
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日本捕鯨協会

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