On the Body Weight of the Sei Whales locatedin the Adjacent Waters of Japan (II)By
KAZUO FUJINO

After studying the correlation between body length and weight ofvarious parts of the body, i.e. meat, bones, blubber and internalorgans, in sei whales located in the adjacent waters of Japan, Omura(1950) notes the differences in weights between sei whales from Bonin
Islands and those from Kamaishi, from which a clue for identifying
two types of sei whales was drawn. Further study has been carriedout consecutively, mainly on the external characters of both types byOmura, Nishimoto and Fujino (1952) and Omura and Fujino (1954),
reaching finally to a conclusion that there present two species in theso-called sei whales in the waters adjacent to Japan, i.e. Balaenoptera
borealis and B. brydei, the latter mostly located in the seas around
Bonin Island.
As only scanty data were available as regards sei whales from
Bonin waters (brydei) at the time when Omura reported previously(1950), further weighing of whales were carried out in 1950. In theyear 1950, 20 whales (7 males and 13 females) of Bonin Islands. wereweighed. These materials are studied in the present paper, comparing
with those presented by Omura (1950).
I am much indebted to the crew of the whaling factory ship'' Baikal Maru '' of Kyokuyo Hogei Company who engaged in the actual
weighing of the carcass, and to the whaling inspectors of Japanese
Government Messrs. Setsuo Nishimoto and Hirosaku Koda who helped
me immensely in the field work. My sincere thanks are also due toDr. Hideo Omura who directed this investigation.
Nearly the same method as reported by Omura (1950) were followed
also in 1950, i.e. the various parts of the body were weighed separately
according to blubber, meat, bones, and internal organs, etc., cutted
into small pieces and using 50 kg. balance. As regards bones andinternal organs, each parts of them were weighed in detail in general,
however in some occasions, some parts were weighed together, when
it was deemed that more reliable data will be obtained by doing so,
not separating into so minor parts. Blood was not weighed. Size
distribution of sei whales weighed are shown in Table I, together withthose from Kamaishi for comparison.

134K. FUJINO

Sex

Table I.

Size distribution of sei whales weighed in
Bonin waters and Kamaishi.
Kamaishi
Bonin Islands

MaleFemale

Total

1
13
1

4

MaleFemale
1Total
112

3

4
4

2
5
3

6
9
33
2

*37
38
39

40

41
42
43

22244
45

112
1

1
12
12
1

2
1

12
42.8

16
42.0

2

2

46

47
48
Total No.
Av. length

439.8

1041.61742.12741.9* Body length in feet.
1. Meat: In the previous report (Omura, 1950) the weight of" Tongue " is included in the category " Meat," but in 1950 those twoparts were recorded separately. Weight of meat in.each measurements
are plotted in Fig. 1. For the sake of comparison to those from Kamaishi, the weight of tongue is added also in those from Bonin Island.
It will be seen from this figure that sei whales from Kamaishi arelittle heavier than those from Bonin Islands in meat, though the difference is small, as already pointed out by Omura (1950). Regression
line of weight of meat obtained from the actual values of each whale
is given by the formula I.
W =0.00015·V- 8~• • • • • • • • (I)
0Bo!lin group-------· • Komoishi group---•104045

body length 1n fee-'.Fig. 1. Weight of meat, sei
whales taken from Bonin andKamaishi areas.

In Table II, the weight of meatfrom both regions are compared, andfrom which it will be seen that thewhale from Kamaishi is heavier thanthose from Bonin Island by about 10%
in meat. However, this weight ofmeat includes weight of tongue,
therefore, net weight of meat is also
shown in this table, calculated bydeducting the weight of tongue, whichis easily computed from the similar
formula for itself.
2. Blubber: In the category"Blubber, "the weight of "Ventral
grooves '' is also included. '' Ventral

On the body weight of the sei whales located in the adjacent waters of Japan (II) 135
Table II.

Standard weight of meat.

Weight of meat calculated fromformula (I)Net weight of meat

- - - - - - - - - - -----------·-

Body length in feet

Bonin.
metric tons

Kamaishi.
%against Bonin

4.38
5.46

113.9
111.2
109.1
107.0

37
40
43
46

6.718.12

Bonin.
metric tons

4.17
5.23

6.45
7.83

grooves '' means the ventral part of the body, consisting of furrowed
blubber and attached meat to it. As seen in Fig. 2 difference in weightof blubber between sei whales from Bonin Island and Kamaishi is very
remarkable, the former having very
heavier blubber than the latter. The
ratios of " Ventral grooves " against
the total weight of Blubber in Boninand Kamaishi groups are, in average,
42.64 and 30.97 percent, respectively.
·;;;
This fact endorses that the ventral:t 1•grooves of the southern type sei
whale (brydei) extend more posteriorly
4045
than those of the northern type sei
body length in feetwhale (borealis). Regression line. ofFig. 2. Weight of blubber, sei
the weight of Blubber against bodywhales taken from Bonin andlength is given by the formula II, andKamaishi area.
standard weight is shown in Table III,
calculated from this formula.

-t2

W = O. 00076 · L2•21........ (II)From this table, it is seen that blubber of Kamaishi group weighonly about 72% of those of Bonin Islands group.
Table III.

Standard weight of blubber.
Weight of blubber

Body length in feet
Bonin. metric tons

3740
4346

2.21
2.63

3.09
3.58

Kamaishi. % against Bonin
71.5
71. 7
71.9
72.l

3. Bones: As shown in Fig. 3, the bones of Bonin Islands groupare heavier than those of Kamaishi group, and this difference increases

136

K. FUJINO

gradually with the growth of bodylength. Regression line is given by
the formula III.
W =0.00005·U81 • • • • • (III)Standard weight is shown in Table
IV.
Average weight of skull, jaw
Fig. 3. Weight of bones, seibones and back bones are shown inwhales taken from Bonin and
Table V. From this table it is shown
Kamaishi areas.
that Bonin Islands group have heavierbones than those of Kamaishi group.
40
15
body ierig+h ;nfee+

Table IV.

Standard weight ot bones.

Body length in feet

Bonin.

metric tons

i Kamaishi.

% against Bonin·----·- ------------·---

37
40
43
46

87.9
80.1

1.41
1. 76
2.16
2.61

Table V.

73.1
67.4

Average weight of skull, jaw bone and back bone.
unit:skull

I jaw bone ! back bonekilogrammesbone total

Remarks----- -'Bonin Is.

524.4
(25.83)209.2(10. 30)901.3(44. 38)

2030.9(100.00) %Average of 27 whales,
average body lengthof which is 41.9 ft.

Kama is hi

467.1(30.28)146.1(9.47)

655.2(42. 47)1542.4(100.00) %'Average of 16 whales,
average body lengthof which is 42.0 ft.

4. Internal organs: In the year"'1948 the heart, lung, stomach and ~3
kidney of Bonin Islands group were
not weighed separately. As it is not c:clear that whether those are added to i1. g'" Others " in the item of " Internal 11: ...._,.....,.__,..-,--,--,-...-,..-,,.....,.--,..-,-40
45
organ '' or to '' Others '' in the itembodylength
infeeiof " Miscellaneous," such materials
were excluded in comparison according
Fig. 4. Weight of internal organs, sei whales taken fromto areas (Fig. 4).
Bonin and Kamaishi areas.
From this figure it may be understood that Bonin Islands group have heavier Internal organs thanthose from Kamaishi. Regression line is given by the formula IV.
<.:)

i2

On the body weight of thesei whales located in the adjacent waters of Japan (II) 137

W =0.000003-L3· 50........ (IV)Standard weight 1s shown in Table VI.

Table VI.
Body length in feet

Standard weight of internal organs.
Bonin.

metric tons

Kamaishi.

%against Bonin.. - - - - - -37

0.88

86.4

40

1.16

83.6

43

1.49

80.5

46

1.89

77.8

5. Total weight: The category" Total weight " is consisting of theabove stated four items and of "Miscellaneous" · which includes baleen,
tongue, jaw ligament and scraps ofvarious parts of the body. As shownin Fig. 5, the Bonin Islands group isheavier than the Kamaishi group inthe "Total weight" also. Regression
line is expressed as the formula V.

• II;'t/ •150I0C/)

co.

00~/-t-III~.

o o Io I o.,,sY. ,;W =0.00047 ·L2· 74 • • • • • • • • (V).

/~//~lo/

//1.
/p "'

Standard weight is shown m
Table VII. Table III shows the differences of weight of various parts
40
45
body length ico fee+
between both areas. It may be seenFig. 5. Total weight, sei whales
from this table that the difference inBlubber weight occupies the greatest
taken from Bonin and Kamaishi
ratio in the difference of Total weightareas.
between both areas. As already stated, "Ventral grooves" in theTable VII.
Body length in feet
37
40
4346

Standard weight of whale body.

Bonin.

metric tons
9.27
11.47
14.00
16.83

Kamaishi.

% against Bonin
94.2
92.0
89.9
88.1

itern of '' Blubber '' includes the meat just underneath the furrowed
blubber in the ventral region. It is quite natural that the sei whales

138

K. FUJINO

from Bonin waters have more heavier ventral grooves than those fromKamaishi, because the ventral grooves extend far more posteriorly inthe former, this being one of every important character identifying
brydei from borealis.
Table VIII. Differences in weight of various parts of the body
between sei whales taken in Bonin area and those from Kamaishi.

Bonin, average of27 whales
Kamaishi, averageof 16 whales
Difference of theabove
Ditto(%)

total
weightmeatbone

blubberinternalorgansmiscellaneousm. tons
13.001m. tons
6.362

m. tons
2.031

m. tons
2.949

m. tons
1.293

m. tons
0.366

11.981

6.958

1.542

2.124

1.163

0.194

1.020

-0.596

0.489

0.825

0.130

0.172

100.0

-58.4

47.9

80.9

12.7

16.9

Table IX shows the weight of various parts of the body, expressedas percentages of the total weight, for the sei whales from Boninwaters. As already stated these weights are calculated from the formulae I-V, and it is not certain that these formulae can be applied forwhales of which body length does not fall within these limits of length,
because these formulae were obtained from the measurements of whales
ranging from 37 to 45 feet in length.
Table IX.
Body length
in feetStandard weight of sei whales captured in Bonin area.

Total weightin metric
tons

meat*

blubber

bones

%%

%

internalorgans %miscellaneous%-·--------~----------

3740
43
46
----------

9.27
11.47
14.00
16.83

45.0
45.6
46.1
46.5

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

23.8
23.0
22.1
21.3
--- - -

15.2
15.3
15.4
15.5

9.5
10.1
10.6
11.2

6.5
6.0
5.8
5.5

------- --* not include the tongue.

Summary

Various parts of the whale body were weighed for 20 sei whalescaught in the Bonin waters in 1950, and after comparing with thosefrom Kamaishi the following conclusions have been reached.
(1) Total body weight are heavier in whales from Bonin Islandthan those from Kamaishi, however,(2) Those from Bonin Islands is lighter than the latter in Meat.

·On the body weight of the sei whales located in the adjacent waters of Japan (II) 139(3) On the contrary Bones, Blubber and Internal organs are heavier
than in Kamaishi group.
(4) Correlations between body length and weight of various partsof body are expressed by the following formulae for the sei whales
from Bonin Island, which are in reality belong to B. brydei.
Total weight
MeatBones
BlubberInternal organs=0.00047. u·7l
=0.00015·U· 81=0.00005•L2' 81=0.00076·U·~ 1=0.000003·L3·" 0Literatures

1.

Omura, H.: Whales in the adjacent waters of Japan. Sci. Rep. Whales Res. Inst.,
4: 27-114, 1950.
2. Omura, H.: On the body weight of Sperm and Sei Whales located in the Adjacent
Waters of Japan. Sci. Rep. Whales Res. Inst., 4: 1-13, 1950.
3. Omura, H., Nishimoto, S. and Fujino, K.: The Sei Whales in the Adjacent Watersof Japan, 1952. Fisheries Agency of Japanese Government.
4. Omura, H. and Fujino, K.: Sei Whales in the Adjacent Waters of Japan II. FurtherStudies on the External Characters. Sci. Rep. Whales Res. Inst., 9: 89-103. 1954.

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total

1,835 47 86 101 171 49 200 77 332 1,063 140 83 206 143 572 11,927

1,856 38 90 86 161 51 203 56 403 1,088 133 111 259 79 582 11,641-

820 200 260

750 170 220

2,930 490
3,510 510

760 180 250

3,100 440~

* Cited from Sci. Rep. Whales Res. Inst., 4:~

130 ~ 220 -550

610190 - 570- 110 - 190 -100 -900910860- 590 590 13' 870

440 440 11, 770

480 480 11, 980

1-13, 1950.

2,262 48 100 174 148 59 256 59 446 1,290 149 141 252 83 625 13,460- 110 1,900

90 1,720-2,244 68 90 117 203 60 324 716201,553 157 139 258 161 715 13,760

90 1,720927 248 301 64 99 -44 May 28 6,540 1,037 1,706 2,743 570 1,060 208 265 66 93 1950"

*42 April 15 6,970

I/*42 April 13 5,820
1948*42 April 15 5, 770

I/

42 June 1 6,345 1,260 1,643 2,903 605

I/

41 June 9 6,390 1,361 1,714 3,075 420 1,084 237 296 49 83 56 2,225 64 102 113 180 53 279 86 387 1,264 157 90 258 152 657 13,611

I/"~987 135 105 413 105 758 11,494

0...,,';;;...,,

981 185 155 47 71 -·;::::..CJuro..i::

41 June 9 5,907 1,001 1,549 2,550 396

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840 204 159 45 75 -..CJ.><:

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1,867 44 140 102 188 59 248 64 474 1,319 115 74 100 78 367 11,752"'.><:"3....<l) ....
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Miscellaneous~774 196 257 53 69...,,0';;;...,,Internal organs"
41 June 8 5,775 1,005 1,335 2,340 533

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1,836 47 94 92 120 38 203 62 331> ....
b.()<l)

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750 214 265 74 83 -1;JCl

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Weight of various parts of sei whales caught in the waters adjacent to Bonin Island, 1948 and 1950
(in kilogrammes)

40 June 8 5,573 1,069 1,271 2,340 450
1950
41 May 29 5,570 1,085 1,544 2,629 518

P'.I'"Cl
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Appendix......

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45 262 11,893

400 400 14, 120//* Cited from Sci. Rep. Whales Res. Inst., 4: 1-13, 1950.

- 2,567 83 116 154 225 68 334 86 718 1,784 180 135 319 173 807 15,959

45 May 31 7,513 1,327 1,961 3,288 712 1,080 232 367 75 101,,- 2,693 71 143 150 278 79 413 72 892 2,098 143 130 304 109 686 16,151- 521 12,550- 600 600 15,430

74 38 2,214 83 98 98 210 58 281 75 363 1,266 120 146 255-- 2,283 35 108 120 300 78 331 95 698 1,805 187 149 304 145 785 15,471-75- 130 - 190 -1,0701,390-- 200 200 13,910

90 1,850 ---- 140 - 240 - 870 1,250 --405 12,792- 100 1,850 -

2,020 54 94 165 210 60 383 83 529 1,588 154 ·- 251 -- 562 12,458

882 219 199 41 97 - 1,983 68 86 90 210 60 311 50 540 1,415 165 112 285
920 200 254 56 68 -- 547 13,908

898 233 263 67 73 30 2,134 50 113 90 202 56 247 53 427 1,238 131 146 2702,367 93 101 119 251 74 352 88 547 1,625 140 113 236 149 638 14.850

45 May 30 7,073 1,650 1,951 3,601 745 1,090 267 394 66 131//.

940

424 11,315940 243 285 63 95 39 2,187 84 101 131 283 77 443 86 513 1,718 137 125 251 139 652 12,775*43 Apr. 14 6,940- 3,670 500 800 190 260 1948
*43 Apr. 16 7,700- 3,890 490 820 210 240 1948
44 June 5 7,353 1,283 1,962 3,245 536 1,061 266 283 621950
44 May 16 6,356 937 1,256 2,193 652 986 240 176 48,,42 May 22 5,531 1,590 1,377 2,967 545,,
43 May 24 5,648 1,421 1,710 3,131 522,,

42 May 16 7,068 1,207 1,714 2,921 570//- 150 - 220 - 570

414 1,221 49 120 255

1,959 51 101 155 204 56 316 56 261 1,200 136 81 -90 1,920 --860 213 214 56 80 -860 170 280 -804 215 254 49 69 19 1,832 59 96 88 210 68 286 -42 June 2 6,980 1,290 1,950 3,240 598 1,074 271 279 62 83 -,,*41 Apr. 16 7,240·- 3,620 520
1948
42 May 23 5,760 1,144 1,568 2,712 536
1950
42 June 4 5,266 1,275 1,677 2,952 522//

41 May 26 5,115 1,125 1,598 2,723 422//*37 Apr. 12 4,040- 2,040 290 580 90 140 - 630 630 8,390
40 1,140 - 100 - 150 - 290 540
1948
40 May 15 6,825 1,230 1,549 2,779 544 1,065 161 281 38 52 375 2,516 45 109 94 184 64 307 64 323 1,191 101 109 263 - 473 13,784
1950
40 May 27 3,725 1,148 1,390 2,538 525 870 186 156 42 55 24 1,858 68 120 101 180 64 314 56 503 1,406 94 139 229462 9,989

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