FOOD HABITS OF THE BRYDE'S WHALES TAKEN
IN THE SOUTH PACIFIC AND INDIAN OCEANS*
AKITO KAWAMURA
Faculty of Fisheries, Hokkaido University, Hakodate, Hokkaido

ABSTRACT

A total of 459 Bryde's whales were taken in the Coral Sea, South Pacificand Indian oceans during the seasons of 1976/77-1978/79 under the schemeof scientific permit. As one of research items on the least known baleen
whale species, food habits of the caught animals were studied on the carcasses in the field, and some 234 stomach samples out of 252 animals of filled
stomach were closely examined in the laboratory. On the whole 55% or
252 animals out of 459 were found to be retaining stomach contents with varying fulness. Analysis on stomach samples suggested that the Bryde's whales
in pelagic waters of the southern hemisphere largely prey upon the euphausiid crustaceans in stead of the fish. These evidences clearly suggest the locally abundant distributions of food organisms. The southern Bryde's whales
may be considered to live substantially on euphausiids such as Euphausia
diomedeae, E. recurva, and Thysanoessa gregaria widely in the studied area, butboth Pseudeuphausia latifrons and E. sibogae may characteristically become
more important food items than the three others in the equatorial eastern
Indian Ocean. Although the found evidence as a whole is the phenomenon
confined to somewhat local areas, both rich fulness of stomach and monospecific composition of the prey organisms suggest that those euphausiid
species may occur with fairly large biomass by forming densely aggregatedswarms even in the tropical and subtropical pelagic regions. The ecologicalimportance of euphausiid crustaceans over the warmer seas as well as those in
the colder seas is discussed.
INTRODUCTION

Since Olsen (1913) studied the Bryde's whales, Balaenoptera brydei from the South
African waters, distribution of the Bryde's whales in the southern hemisphere haslong been known but this animal remained as less known balaenopterid whales due
to rather sporadic information. Except several taxonomical studies on the stranded and/or occasionally taken animals, there has been no biological study of any extent. Recently, however, Best (1960, 1967, 1977) studied the Bryde's whalescaught off Durban and Donkergat, South Africa and found that there occurs two
allopatric forms, i.e. inshore and offshore forms. The main difference which separates the species into two forms was the morphological differences in the shape of* Abstract of this work was orally reported at the XIV Pacific Science Congress, Khabarovsk, USSR,
1979.
Sci. Rep. Whales Res. Inst.,

No. 32, 1980, 1-23

2

KAWAMURA

baleen plates such as the width/length ratios in addition to the general biologicalcharacteristics by each form (Best, 1977). The exhibited character of baleen plates
in both forms resulted to show a considerable different food habits among them.
Best (1977) states that the inshore form feeds mainly on small gregarious fishes suchas anchovy (Engraulis capensis) and pilchard (Sardinops ocellata), while the offshore
form strongly prefers to feed upon the Euphausiacea such as Euphausia lucens. It
can be said that our knowledge on the biology of the southern species of Bryde's
whales has largely increased during the past two decades.
However, our knowledge having been obtained to date seems to be still
confined to that from local and possibly coastal stocks of this animals. The catches
at South Africa (Best, 1960), Western Australia (Chittleborough, 1959), New Zealand(Gaskin, 1972) and Chile (Aguayo, 1965) were all done by the land based whaling.
On the other hand, there occurs more larger number of Bryde's whales over thevast pelagic regions of the southern hemisphere (Gambell et al., 1974), but neither
has been studied concerning the status of possible pelagic stocks nor the biologicalcharacteristics due to the international control measures of whaling.
It has been known that the distribution of Bryde's whales are confined largely
within the temperate to tropical seas where the temperature is higher than 20°C
(Omura and Nemoto, 1955). The habitat for the Bryde's whales is quite unusual
when it is compared with the case in another balaenopterid whales, to which mostbaleen whale species may visit only for breeding.
From the viewpoints of ecological energetics, the breeding ground for thebaleen whale species cannot be considered the place of any extent of feeding, i.e.,there is no nutritional importance at all. On the other hand, some observations
strongly suggest that the feeding of balaenopterid whales may take place in thewarmer seas (Gambell et al., 1974; Masaki, 1979). The author too observed many
Bryde's whales that swam away leaving a patch of brick red feces when they werechased during the tagging investigations in the equatorial Pacific. An estimationof the energetic budget of locomotion in balaenopterid whales suggests that eventhe animals under breeding migrations to the warmer seas must perhaps feed tosome extent (Kawamura, 1975). The above mentioned facts strongly suggest that
there must exist the aggregations of possible food organisms which are available forthe baleen whales visiting those warmer waters. These, however, must be clarified by the actual observations on the collected materials and the examination of
stomach conditions of whales occurring in the warmer waters.
In order to study the southern Bryde's whales (Balaenoptera edeni) in pelagic
waters, Japanese Government granted to take specially 120 animals per fleet perseason in 1976, and the programme went on next three successive seasons, 1976/771978/79. The special permit programme for the purpose of scientific research carriedout under the supervision of the Far Seas Fisheries Research Laboratory of Fisheries
Agency, and the whole programme came to an end in 1979. A total of 459 animals
have been caught in the pelagic waters over the central South Pacific and Indian
oceans. Although there has preliminarily been reported on earlier results by separating each fishing season (e.g. Ohsumi, 1978; Kawamura, 1977), Ohsumi (1979)
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

3

finally submitted provisional report to the 3lst IWC meeting, in which he dealt
with the whole result throughout the past three seasons, and estimated a possible
harvestable quotas by the sea regions worked out. However, the food habits of the
Bryde's whales were not treated in his report since it was not the subject being
treated in the fishery biology and stock management. Therefore, this report could
be considered as one of the supplements relating to the Japanese catch of the southern Bryde's whales under the scheme of scientific permit.
MATERIAL AND METHOD
A total of 459 Bryde's whales were caught during the past three exploratory expedtions. It is, however, still unknown to date that to which forms, inshore or offshore,
the animal belongs. The overall figures for the experimental catch are given in
Table I and Fig. 1. Two factories, Tonan Maru No. 2 and Nisshin Maru No. 3 of
TABLE I.

EXPLORATORY CATCHES OF THE SOUTHERN BRYDE'S
WHALES DURING THE SEASONS, 1976/77-1978/79
No. of animal caught

SeasonSea areaMale

1976/77

1977/78
1978/79

Coral Sea
Central S.
Pacific
SW Indian
Ocean
Central S.
Pacific
E. Indian
Ocean

Total

FemaleTotal

Stomach contents
Present
(A)

A/A+B
Empty
(B)

(%)

No. ofstomachsampleexamined

3

4

7

5

2

71.43

5

66

47

113

85

28

75.22

64

61

44

105

49

56

46.67

52

72

42

114

60

54

52.63

60

61

59

120

53

67

44.17

53

263

196

459

252

207

54.90 (Av.)

234

Nippon Kyodo Hogei K. K. operated during 1976/77 season and each of them was
granted to take 120 animals. However, during the two successive seasons, there
operated only one factory, Nisshin Maru No. 3 and the catch reduced to about anhalf from that expected when programme came to an implementation in 1976, andthis resulted somewhat insufficient collection of data for the general biologicalstudy.
The observations on the stomach condition of animals were carried out on two
different basis: 1) eye observations on the carcasses in the field, and 2) more closer
examinations of the food species based on a fraction of stomach materials by random
samplings. The stomach contents were collected regardless the magnitudes offreshness and of the amount in a stomach. Observations in the field may provide
somewhat rough evidence such as an approximate amount of stomach contents interms of percent stomach volume by five different fulness and the kind of food species by rough systematic taxa such as Pisces, Euphausiacea, Amphipoda and Copepoda. In the case of Euphausiacea, however, the difference of body size by threesize classes, viz. 'large', 'medium', and 'small' were also recorded by a personel who
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

KAWAMURA

4

was skillful enough for this kind of observations. The observed records in the field
were compiled into a register format, 'Catch Records of Whales' by the whaling inspectors of the Fisheries Agency. I used some data from that records especially inconstructing the general catch figures and stomach conditions.
A total of 234 stomach contents were collected from 252 animals with filled
stomach. The collected materials preserved in 10% formalin solution were sent
to the Whales Research Institute, Tokyo, but later to Hokkaido University where
the composition of food species were studied.
RESULTa)

Catch distribution

It has long been known that the Bryde's whales occur frequently in the tropical to subtropical waters of both hemispheres where the whaling fleet passed byevery season en route to and from the Antarctic whaling ground. By taking accountof this fact but with an uncertainty as the object of mothership operation, experimenN
30°
20'

100

'17

w (jp

oo

\.;Jc:::;,, V1f

10'

3-19~7~w ~ ~ ~C\'-.-,

20'

120 animals

30°

30 X-5 XI ~/1976
29 X-18 XI
113 animals~ 1977'V
114 animals

rJ

40°
50°
60'
SO'

24-25 x 1976
~ 7 animals

20'

40'

60°

80' 100' 120° 140° 160° 1 80' 1 60' w

Fig. I. Catch areas of the Bryde's whales taken by scientific permit in the South
Pacific and Indian oceans during the seasons of 1976/77-1978/79. The shaded
area indicates heavy concentration of catches.

tal and exploratory catch investigations were carried out by setting a possible sea
regions in the South Pacific and Indian oceans. It was proved by sighting investigations that the Bryde's whales largely distribute in both South Pacific and Indian
oceans, and the latitudinal range may extend over the tropical to temperate regions. During the 1976/77-1978/79 seasons the main concentrations of Bryde's
whales were spotted in the Coral Sea, central South Pacific, and eastern andsouthwestern Indian oceans (see Ohsumi, 1978, Fig. 1).
Figure I demonstrates approximate catch areas along with related figures wherea total of 459 animals was taken during the exploratory whaling. It is obvious thatthe catches in the central South Pacific and equatorial eastern Indian oceans wereactually made being based on the sightings worked out in 1976/77 season. Except
the catch in the southwestern Indian Ocean all the rest were caught in the tropicalsea regions where the south equatorial current or its counter current prevails. The
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

5

observed surface sea temperature ranged 20.0-30.3°C during October to November.
Contrary, the region of south west Indian Ocean was operated in March when thesurface sea temperature showed 24.6-26.6°C. According to Ohsumi (1979), theaveraged body length and weight of animals by catch areas was found to be 13.05 m(15.2 tons) as the largest figure in the South Pacific, while the smallest was 12.10 m(12.36 tons) in the Indian Ocean animals (Table 2).
Comparing these figures with those having been observed in the northernequatorial to temperate Pacific (e.g. Wada, 1975; Ohsumi, 1978; Masaki, 1979),
it may be considered that the Bryde's whales seem to distribute with somewhat
biantitropical pattern over the both hemispheres.
TABLE 2. THE AVERAGE BODY LENGTH OF SOUTHERN BRYDE'S
WHALES BY THE SEA AREAS (AFTER OHSUMI, 1979, TABLE 13)
Sea area

Indian"'S. Pacific**Total

No. of whales caught
Total average body length (m)Estimated average body weight (ton)

225
12.10
12.36

235
13.05
15.12

459
12.58
13.66

* Baths outhwestern and eastern areas of the Indian Ocean are combined.
** Coral Sea animals are included.

TABLE 3. STOMACH CONDITIONS OF THE BRYDE'S WHALES IN THE SOUTHERNHEMISPHERE. THE QUANTITY OF FOOD IS APPROXIMATED BY THE VOLUMESOF BOTH STOMACH AND THE AMOUNT OF CONTENTS
WhalinggroundSW Indian
E Indian
Coral Sea
CentralPacific
CentralPacific
Total
Percentb)

Quantity less than :Food species

Total

SeasonEuphausiacea Pisces1976/77
1978/79
1976/77

49
46
5

1976/7785

1977/78

7

60
245
96.8

8
3.2

Empty

25%

50%

75%

100%

56
67
2

21
16
2

lO
24
l

1
lO
l

17
3

105
120
7

28

47

19

12

7

113

53

28

15

9

9

114

206
44.9

114
24.8

69
15.0

33
7.2

37
8.1

459
100.0

Stomach condition

The stomach condition in general was observed in the field. The catch record shows quite high percent occurrences of the Euphausiacea (96.8%) throughout five different whaling grounds worked out. There were no biassed trends ofthe regional occurrence in Euphausiacea, and fish food accounted only 3.2% amongall. This was really unexpected evidence from that supposed in advance to thecatch of whales came to an implementation (Table 3).
The quantity of stomach contents actually found in each animal was found to
be relatively abundant. Table 3 shows that 253 animals (55%) out of 459 wererepleted with food under various magnitudes. It must be noted that 70 animals
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

KAWAMURA

6(27.7%) out of 253 were found to be very abundantly (75%+100%) repleted withfood. To see the similar figures by each whaling ground, the highest was foundin the Coral Sea (40.0%) and/or southwestern Indian Ocean (36.7%) while thelowest was in the central South Pacific (22.4%) for the 1976/77 season. Thesefigures may suggest that there must be comparatively abundant distributions ofavailable food concentrations even in the so-called 'barren' tropical seas, the placeof far well outside from the proper feeding ground of baleen whales in the southernoceans.

Diel changes in the quantiry of stomach contents
It may be hard to believe that the baleen whale shows any local behavioral
changes in their feeding activity or behavioral pattern to an appreciable extent although some locally modulated changes are expected by the composition of available food species due to their own local characteristics in the diel migratory pattern. If the whale does not change essentially their behavioral pattern of feeding,then the diel variation of the quantity of stomach contents may suggest the dielvariation offeeding activity and/or its intensity.
c)

Fulness of st0<00ch

20

SW Indian OceanCl976/77)

N:I05

Empty

15

c:::::::J

0-25% ~

JI)

25-50% ~50-75%lllllllllllllil
75-100% Eastern Indian OceanU978/79)

Nd20

L_. ~~~~n~L.l.L....m.J
0 [k, [lm Dm
n ~ M..LJ.. - [l. [}A 0 -1051---1-Jf

r4

[km

....-iI~::1~._F[ _.....So-ut-h~Poc~lf~lc-Cl...i97~7/~73•)--'-"'N:Lll~4._..."""'--'--"'....,l...JIZ£"-l..lim._.LIZElllll...l~.._..EaS!...._-"""~Jm....ia.c:""--'
0 0 [b [l_ f1i J1Jm. ~ CL ___,,__ crmi rrOJAm.!]k ,n,. • .,.,.
_!

S~ea1C I_97-6/...i~7_,,'.,.L..-N ~ ..m"'PlllL--'-'_ _,__ _.___._ _ _ _-'no___,5 ,_f--'C'-o-ro_l

=
.....

South PaciflcCI976/77l

N:113

19

Local time of catch

Fig. 2. Change of stomach fulness by the local time of catch in five different whaling areas.

Figure 2 demonstrates the number of animals by the five different stomach conditions against local time when the animals were caught. Among the animals withfood of any magnitudes in their stomach, it is observed that th.e stomachs repleted
50% or more seems to occur poorly except very few examples. This may suggestthat the stomachs with food are represented chiefly by rather poorly repleted
animals. The occurrence of empty stomach predominated during the first halfof day, and seems to reduce toward evening. The empty stomach was foundSci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

7

largely in three examples; southwestern Indian Ocean (1976/77), equatorial eastern
Indian Ocean (1978/79) and the South Pacific (1977/78). In the Coral Sea region
the number of catch amounted only seven animals in all, and it is difficult to draw
any general trends offeeding activity. On the other hand, feeding condition in theSouth Pacific region for 1976/77 season showed very high percent occurrence of well
repleted animals (75.22%), while the rest ranged 44.7-52.6% (see also Table 1).
The die! changes in feeding activity can be observed over the regions in question.
In the animals from southwestern Indian Ocean the occurrence of well repleted stomachs was concentrated clearly in the first half of the day, and this region must be
noted of being different feeding conditions from the four others. There were nocatches after 1600 hours in this region. On the other hand, the animal with well
repleted stomachs in the eastern Indian Ocean, South Pacific and possibly in the
Coral Sea showed dispersed occurrence over the whole daytime but somewhat biassed

30.A---& Total

t'.'\

28

I'

26

0 - 0 S. Pacific (76/77)
x------x S. Pacific (77 /78),._ __ _., E. Indianl'r- -l:. SW Indian

.

\

24

\

22
20

r,k--~\\, It-'Vj

ro 18

-~

~ 16

'O 14

lf-4 ~·

0

z 12
10

\\

\

8
6

I
I

4
2

I

I
I

''

6

Fig. 3.

_,·/

x' /

J,_

I

7

8

9

10 11 12 13 14 15 16 17 18 19 20
Local time of catch

Diel variation in the number of animals with filled stomach.

in the afternoon toward evening, and a possible nocternal feeding may take place inthese sea regions. Although there observed quite unusual large number of animals in
the morning for the 1976/77 and the 1977 /78 seasons of the South Pacific, the feeding
activity of whales on the whole possibly follows to a definite trends. That is, despite a great variety in the die! feeding activity of whales by season and localities,
it is noteworthy that more intense feeding would take place twice a day to show abimodal changes, once in the early morning and then toward the evening (Fig. 3 ).
The more detailed figures relating feeding activity are given in appended tables(Appendix Tables I and II).
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

KAWAMURA

8TABLE 4.

SYSTEMATIC LIST OF THE FOOD ORGANISMS
OF THE SOUTHERN BR YDE'S WHALES

Euphausiacea :Euphausia recurva Hansen
Euphausia diomedeae Ortmann
Euphausia sibogae Hansen
Pseudeuphausia latifrons (G. 0. Sars)
Thysanopoda tricuspidata Milne-Edwards
Thysanoessa gregaria G. 0. Sars
Pisces:Vinciguerria nimbaria (Jordan & Williams)
Auxis thazard (Lacepede)
M yctophiformes** unidentifiable larval forms
TABLE 5.

KIND OF FOOD ORGANISMS OF SOUTHERN BRYDE'S
WHALES BY THE SEASON AND CATCH AREAS

SeasonDate

Sea temp.
(oC)

1976/77

Oct. 24-25

28°

Oct. 30Nov. 5

200-23°Mar. 7-13

24.6°-26.6°

1977/78

Oct. 29Nov. 18

20.2°-23.4°

1978/79

Nov. 3Nov. 19

25 .8°-30. 3°

Approx.
location
9°49 1-10°17 1 sCoral Sea
157°291-157°561E
24°25 1-27°59 1 s
S. Pacific
l 77°1l1-l 78°34 1E
28°23 1-31°47 1s
SW IndianOcean
43°55 1-51°36 1E
21°15 1-29°24 1s
S. Pacific
179°45 1 E-l 70°58 1W
Sea area

E. IndianOcean

9°47 1-12°49 1 S
92°021-118°321E

Food species

Euphausia diomedeae
Euphausia recurva
Thysanoessa gregaria
Euphausia recurva
Hatchetfish*
Euphausia recurva
Thysanoessa gregaria
Gonostomatid fish**Euphausia diomedeae
Euphausia sibogae
Pseudeuphausia latifrons
Thysanopoda tricuspidata
Vinciguerria nimbaria
Auxis thazard
Myctophiformes* fouf!d only one specimen as a possible contaminant.
** probably V. nimbaria.

Kind offood organisms
There have been found comparatively poor compos1t10n of food species forthe southern Bryde's whales in pelagic waters (Kawamura, 1977). It is clear thatthe Bryde's whales feed mainly upon Euphausiacea and the shoaling fish or its larval forms, and epipelagic planktonic or micronektonic organisms other than eueuphausiids were much lesser extent (Table 4 ).
The result actually found was that hardly been expected until the catches ofBryde's whales were implemented. Among the Euphausiacea, there found three
species of the genus Euphausia (E. diomedeae, E. recurva and E. sibogae) and one species
belonging to the three different genera, i.e., Thysanopoda tricuspidata, Thysanoessa gred)

Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

9garia, and Pseudeuphausia latifrons. T. gregaria must be considered tentative identification due to ill conditioned specimens by digestion. The geographical occurrence ofeach food species is given by the whaling grounds in Table 5. It is observed thatthe composition of food organisms is very monotonous over the first four whaling
grounds where E. diomedeae, E. recurva and/or T. gregaria predominated. Fish wasconsidered to be less important by any magnitudes. The equatorial eastern Indian Ocean, on the other hand, showed relatively diversed complexity to the another four cases in the composition of stomach contents. However, there foundonly P. latifrons as the principally important food species than three another species.
As for the gonostomatids, Vinciguerria nimbaria showed a mesa-scale importanceamong the whole member of food species. V. nimbaria has been found to be of greater importance as the food of skip jack, Katsuwonus pelamis in the tropical Pacific(Kubota and Kawamura, 1972).
TABLE 6. OCCURRENCE OF SPERM SAGS IN SIX EUPHAUSIIDSPECIES FED BY THE SOUTHERN BRYDE'S WHALES
Sperm sac present:
Both
Male+Female
E. diomedeae
E. diomedeae
E. recurva
E. recurva
E. recurva
T. gregaria
T. gregaria
E. sibogae
P. latifrons
T' da tricuspidata

3
6
2

Only
Male

AbsentFemale
I
6
28
29
3

2

Unknown

Whaling groundMale+Female
2
5
5
30
11
35

2
29

2
11
16
2
2
4
2

Coral Sea
E. Indian
S. Pacific (76/77)
SW Indian
S. Pacific (77 /78)
S. Pacific (76/77)
S. Pacific (77 /78)
E. Indian
E. Indian
E. Indian

The populations of six euphausiid species above mentioned are usually composed of both adult male and female in similar sex ratios though there were several
cases of slightly biassed sex ratios with more numerous in the number of male than
the female. Although the majority of T. gregaria was composed of adult forms ofboth sexes, there were a few cases that adolescent or juvenile forms occurred mixing with the adults. Some male and/or female individuals over several populations of above six euphausiid species carried a sperm sacs on the thelycum or ejaculatory duct but this strongly biassed to females (Table 6). E. diomedeae of theCoral Sea population carried the sperm sacs on both sexes, while it was only on
females from the equatorial eastern Indian Ocean. Similar trends were found in
T. gregaria but no sperm sacs were found in the South Pacific populations occurredin the 1976/77 season. Although, there found very occasional occurrence of carrying sperm sacs in P. latifrons, it may be reasonable to refer the species as having
no associations with mating at this time of the season viz. early to mid-November.
One of interests is that there were very close associations in the occurrence of posSci. Rep. Whales Res. Inst.,

No. 32, 1980

KAWAMURA

10

sible euphausiid eggs with P. latifrons. The appearance of the egg was observed
very similar to those of euphausiids. Therefore, it is reasonable to suppose that theegg might perhaps come from P. latifrons since it was the only species that possibly
lost sperm sacs from all individuals occurred. Thysanopoda tricuspidata also did notcarry sperm sacs but this species by no means occurred associating with any kindof planktonic eggs.
In summerizing the results concerning euphausiid food, it is noticed that bothE. recurva and T. gregaria covered geographically wider ranges and are consideredmost important food species in the central South Pacific while it was only E. recurva
in the southwestern Indian Ocean. In the equatorial eastern Indian Ocean, on
other hand, the principal dietary members turn to P. latifrons and E. sibogae. BothT' da tricuspidata and E. diomedeae occurred with much lesser extent.
TABLE 7. PREY ORGANISMS FOUND FROM SOME FISH SPECIES THATWERE FED BY THE BRYDE'S WHALES TAKEN IN THE EQUATORIAL
EASTERN INDIAN OCEAN DURING 1978/79 SEASONFish species

Body length(mm)

Au.x:is thazard (Frigate
mackerel)

215

Vinciguerria nimbaria

38-50

Location

Date

Food items

10"14 1 s

Nov. 9, 1978

Nov. 15-17, 1978

Candacia pachydactyla
Euchaeta marina?
Others*
Copepods**
Fish larva
Euphausiid(P. latifrons) -egg?

Nov. 15, 1978

Copepods**

112°12 1 E
11°00 1 s
97°121 E
11°13 1 s
95°26 1 E

11°15 1 s
95°32 1 E

M yctophiformes

24-25

11°16 1 s
95°28 1 E
11°52 1 s
94°12 1 E
11°16 1 s
97°34 1 E

* Decapoda-megalopa, large cheliped like appendages, Amphipoda-Hyperiidae, Lucifer? Cavolinia sp.
Bivalvia larvae, and unidentifiable crustaceans due to heavy digestion.
** unidentifiable.

As for the fish diet there found three kind of shoaling fish species: the Myctophiformes, gonostomatids (Vinciguerria nimbaria), and possibly contaminated one
specimen of frigate mackerel (Auxis thazard). Among these fish diet only the gonostomatid species, V. nimbaria was actually formed the diet of the southern Bryde's
whales especially in the equatorial eastern Indian Ocean. The unidentifiable larval
forms of fish belonging to the Myctophiformes was also preyed upon the animals
but by far the lesser magnitudes than V. nimbaria. In general the occurrence offish diet is very local phenomenon limited spacially in small area. Althouth the
Myctophiformes species was found only in one stomach, and V. nimbaria in five stomachs in the 1978/79 catches, they occurred in the state of solely monospecific cornSci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

11

position except one mixed example with E. diomedeae.
The prey organisms found from those above mentioned fishes were examinedin order to compare them with the stomach contents of whales. Both frigate mackerel and the Myctophiformes were very young forms, while V. nimbaria was adult.
Although the taxonomical details of prey organisms from these fish species are stillinsufficient, Table 7 demonstrates that the species composition of prey organisms
in the gut from those fish species are very variable. The frigate mackerel ate atleast several adult males of Candacia pachydactyla, Euchaeta marina (?) and many unidentifiable copepod species, Decapoda, Amphipoda, and very young Thecosomata
of possibly belongs to Cavolinia sp. It is noteworthy that not withstanding the factof greatly diversified prey items, there found to lack euphausiid species that were themain diet of the Bryde's whales. This, however, seems to be confirmed by further
TABLE 8.

NUMBER OF STOMACHS BY THE KIND OF FOOD ORGANISMS
1977/78

1976/77

1978/79---

S. Pacific Coral Sea SW Indian
E. diomedeae
T. gregaria
Euphausia sp. *E. recurva+ T. gregaria
T. gregaria+E. recurva
E. recurva
E. sibogae
P. latifrons
P. latifrons +E. diomedeae
T' da tricuspidata
Euphausia sp.**
E. diomedeae + V. nimbaria
Fish larva***+E. diomedeae
V. nimbaria

S. Pacific

5

38

7
29
2
2

11
38
8
11
9
109
7
29
2
2

4

4

6

10
7
8

28

51****Total

E. Indian3820

Gonostomatid fish
* Probably E. recurva.
** Probably E. sibogae.
*** Larval forms of Myctophiformes.
**** Mixture with one individual of hatchet fish is included.

examinations since micronektonic fish migrants in the tropical Pacific are known tofeed euphausiids by a magnitude accounting for 8% of total food ingested (Roger,
1973a). Even so the completely different gut contents of preyed fishes found fromthe whale stomachs suggest that these fish species were not associated with the occurrence of food euphausiids. It may be considered that those micronektonic fishes may linked with another branched off foodchain systems which are perhaps different one from the prey- predator relationships between Bryde's whales and euphausiids.

e) Composition of stomach contents
The composition of stomach contents from the collected samples is given in
Sci. Rep. Whales Res. Inst.,

No. 32, 1980

KAWAMURA

12

Table 8 by separating the' catch area and the season. In order to show the characteristics of the composition of stomach contents a matrix was constructed (Fig. 4 ).
Although a considerable diversity in the composition of forage was observed in general, it may be noticed that the principal food items were comprised of four major
euphausiid species; Euphausia diomedeae, E. recurva, Pseudoeuphausia latifrons, and Thysanoessa gregaria. Both South Pacific for the 1976/77 season and southwestern Indian oceans were represented largely by E. recurva, where this species accounted
59.4% and 98.1 % respectively in number of the stomach. Different from the previous season, however, T. gregaria occurred in addition to E. recurva as major food
Minor components

Food species

2

I

4

3

5

7

6

I

3

1)3

T, gregariaI2
5

P. latifrons

6

T. tricusp!data

Q)

c

0
o_

E
0

u

20 8

3

g I Jn ?O

7

4 E. sibogae..,c"''-----

51

2 E. recurva

29

I

2
I

L

0
·3 7 Euphausia sp,•

T

"'

I

8 Euphausla sP. ••Key to the nun1erals
in sauare

9 V. nimbarla
10

Gonostomatids

11

Myctophi formes

10

I

5

E. di omedeae

9

3

6

L >od<o"Coral Sea
I

4

~OW""'°"__l_s. Pacifics. Pacific( 1976/77)( 1977 /78)

• Probably E. recurva•• Probably E. sibogae

Fig. 4. Composition matrix for the 234 stomach analysis in the southern Bryde's
whales. Numerals in the square denote the number of stomachs by the five different whaling areas.

species by 50% of occurrence in the South Pacific for the 1977 /78 season. Although
the number of whale catches in the Coral Sea were seven in all, there occurred only
E. diomedeae. In the equatorial eastern Indian Ocean P. latifrons occurred in great
numbers, where this species accounted for 58.5% among all. E. recurva did notoccur in this locality but E. diomedeae and E. sibo,£;ae accounted for 11.3% and 13.2%
respectively. The latter two species can be refered to as a meso- scale importanceas the whales food. As it is noticed in Fig. 4 one of the characteristics in the equatorial eastern Indian Ocean may be found in the diversity of species composition
when it is compared with the case in four another whaling areas. It must be noted
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

13

that both E. sibogae and T' da tricuspidata by no means occurred under the mixed
state in composition with another kind of food species, while E. diomedeae, E. recurva, P. latifrons and T. gregaria, the principal food items of the southern Bryde's
whales in pelagic waters, occurred at times by mixture with one of each other. The
stomach contents composed of the Euphausiacea seem to very similar composition
over the different four whaling ground occupied through the 1976/77-1977 /78 seasons
while they changed notably to different food species in the equatorial eastern Indian
Ocean. Except the case in T. gregaria and E. recurva, there were very few stomachs
that were composed of mixture by more than two food species. Although there
were several instances scattered at far from the diagonal line which indicates a single species composition, the most stomachs were found to be characteristically composed of mono-specific composition, that is, 210 (89.7%) stomachs out of 234 foodcontained stomachs were comprised of only one food species. The animals in theSouth Pacific ground for both the 1976/77 and 1977 /78 seasons fed same euphausiid species and their mixture. It can be said that the general feature of the foodcomposition was very simple and the fish was of minor importance in so far as thegiven localities in pelagic waters.
While laboratory examination of the stomach contents under the microscope,
it was noticed that there were difference between each component species in theirfreshness and/or the magnitude of damages among the preserved materials of mixed composition with two or more kind of species. This may suggest a possible timelag due to the difference in feeding time by each component species. The whalemight have fed upon them from one to another, each of which might have hadformed aggregations independently with a little spacing over the spacially small
scaled area.

f)

Distribution offood species
Figures 5-6 demonstrate the horizontal distribution of food orgamsms by
species over the five whaling areas. The plot in the Fig. 5 represents all position
where positive occurrence of each food species was recorded. When the stomach
was composed of two species in mixed state, they were plotted separately by eachspecies elsewhere in the chart.
In the Coral Sea there found only five stomachs of containing E. diomedeae.
The South Pacific areas were visited twice during two successive seasons as noted in
the figure. Each whaling area is located at almost same sea region with a little
overlappings, but there were no notable differences in the catch periods and sea
temperature in these two seasons (see Fig. 1 and Table 4).
Since the catch of whales in the Coral Sea took place in a locally biassed area,
the occurrence of E. diomedeae was also confined to spacially small area. The
central South Pacific areas, on the other hand, covered over the wide latitudinalor longitudinal ranges of magnitudes expanding for several degrees. Both E. recurva and T. gregaria occurred over the whole geographical ranges but somewhat
dispersed distributions in the latter species. E. recurva for the 1976/77 season fairly well concentrated focally where the species occurred approximately within a laSci. Rep. Whales Res. Inst.,
No. 32, 1980

KAWAMURA

14

20'"' E. sibogae

40'• E. diomedeaeo E. recurva+ P. latifrons
b. T. tricuspidata• T. gregaria<> FishFig. 5.

24'

27'

0
0

Distribution of euphausiids and fish that were fed by the southern Bryde's whales.

s20'.---~~~~--.~~~-r---,-~~~~~~~

S. AFRICA

E. recurva~

30'

Southwestern Indian Ocean

1976/77
40'
S T. gregaria

-J-

28'
29'
50'

a....

30' :~·

Fig. 6.

·::

31' 'ri

32'
44'

60' 20'

...,

30'

46'

40'

50'

48'

50'

52'E

60'

E

Distribution of euphausiids that were fed by the southern Bryde's whales.

titudinal or longitudinal square by one-degree. Similar local concentrations wereagain observed in the 1977/78 season but lesser magnitude. It is, however, hard
to know whether or not the horizontal distribution of E. recurva and T. gregaria wasdifferent to any appreciable magnitudes. Very similar locally biassed concentrations of food euphausiids are also observed in the southwestern Indian Ocean but
the spacial expand of the whaling area was relatively larger than the formers.
In the equatorial eastern Indian Ocean the food species distributed with conSci. Rep. Whales Res. Inst.,
No. 32, 1980

15

FOOD OF BRYDE'S WHALES

siderable geographical differences by each species. P. latifrons was the most dominant food species among three others, and occurred more frequently in the eastern
half of this whaling area. Both P. latifrons and E. sibogae showed a possible very
closer associations with each other in their occurrence. Although very occasionalin frequency occurrence, E. diomedeae did not show such characteristic trends as
the former two species but somewhat closer associations with the gonostomatid
fish, V. nimbaria in the western area. T' da tricuspidata occurred at only two positions and hardly be known its distributional characteristics. There was the space
where the food organisms distributed very sparcely in the midst of the eastern Indian Ocean area. Although the reason why food organisms distributed so sparcely is unknown at present, the region well coincides with the area where distinct discontinuity of euphausiid distributions has been demonstrated (Ponomareva, 1972).
S Southwestern Indian Ocean
2 8 ',---,---,-,---,--,-~--,-----,---,S
South Pacific (1977 /78)
21 '.-----.--.---,---,-~~--.--.---,-~~

29'

22'

g':{;go

00

23'

30'

.i ::·

31°
32'

0.

24'

50'

25'
52'E 26'(1976/77)
So"th
Poomo

28'

'o

~~~_...,._~~-~~~~

s

44'

46'

"1 ~
26

I

24'

25

0

·i~:"::
~
••

··;.:

48'

27'
•

0

•

0

o •

12'

•

·.·
~-

•

~~o.

98'

Oo

0

Eastern Indian Ocean~~.

0g o•~\ce
00

0
0
0

00

96'

og

0

0

0
0

00~~

0

o••
0

13'
94'

0

: \=: : •

•

•

·.

OpP

0

27'
o
28'
..
176' 178'E

11 °

l, o

0
• 8.
29'
:?o 0 °
30°'----'--'--'---'-.1---'----'--'--'---'--'-'
178' E 180' 178' 176' 174' 172'W

0

10°

o

•·:•A>:

100'

102'

104' 106'108' 110'

8o

0

~

•

0.
• 0

o~•

112'

oi;•:
114' 116° 118'E

Fig. 7. Catch distribution of Bryde's whales during the seasons of 1976/77-1978/79.
Filled and open circles denote the animal of filled and empty stomach respectivelly.

To summerize the overall distribution characteristics of the food species
throughout the five different whaling areas, it is obvious that the main concentration area of food organisms and whales distributed unevenly with local biass
over the regions worked out. From this viewpoints it may be observed that theconcentration of whales occurred at very spacially small localized areas where the
distribution of aggregated food organisms showed quite biassed occurrences. These
therefore, can be confirmed that 'the animals with filled stomach concentrated in
the way above mentioned while those with empty stomach having been possibly
in search of food were found to show relatively scattered distribution over the whole
whaling areas (see Fig. 7). This evidence may suggest that the movement of whales
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

16

KAWAMURA

in the tropical and/or subtropical seas is significantly related to the presence of available foods. Where abundant food distribution is exhibited, movement of whales
may become stationary for the time being.
DISCUSSION

Several past catch records of the Bryde's whales in the southern hemisphere arecompletely confined to the catches by the land based operations. This may represent very locally limited feeding conditions for the whales occurring in coastal tooffshore regions since locally characteristic environmental conditions in near shore
waters may determine the faunal distribution-the occurrence of endemic species
including planktonic organisms.
There have been reported a several number of such informations as that camefrom the coastal whaling. In regard to food and/or feeding habits of the Bryde's
whales in the southern hemisphere, Symons (1955) described only pilchards foundfrom the Saldanha Bay animals. Examining Donkergat animals, South Africa,
Olsen (1913) more earlier reported that the Bryde's whales feed upon 'fish' and hefound but one occasion of the remains of euphausiid crustaceans. Best (1960)
summerized some of those earlier data and reported that the catches of Bryde's
whales in the southern hemisphere are largely took place around the South African
coast, but there were also catch records of lesser extent in Western Australia, North
Island of New Zealand, and northern Chile. The Saldanha Bay animals were
found to feed upon pilchard (Sardinops occellata) and anchovy (Engraulis japonicus)(Best, 1960), but the latter was corrected to be E. capensis in the later study. Morelater, Best (1967) reported that the majority of Bryde's whales of visiting Cape Province region, South Africa feed upon both shoaling fish such as pilchard (Sardinops
occellata) and anchovy (Engraulis capensis), and euphausiids, Euphausia lucens. Bannister and Baker (1967) also reported but one instance of E. recurva as the food of
Bryde's whales off Durban. Best (1977, Table 5), however, gave more complete
sets of dietary habits, where he reported the following food items by identifying
both inshore and offshore forms of the Bryde's whales each of which demonstrates
very characteristic food habits: The inshore form chiefly feeds upon shoaling fish
members, Engraulis capensis, Trachurus trachurus (jack mackerel), and Sardinops occellata, while the offshore form feeds largely upon the Euphausiacea such as Euphausia
lucens, E. recurva, Nyctiphanes capensis and Thysanoessa gregaria along with some pelagic fish species such as Maurolicus muelleri, Lestidium sp., Scomberesox saurus and Scombrid sp. He (Best, 1977) also found cephalopods, Lycoteuthis diadema, as the first record as whales food from the same locality. In northern waters off Point Cloates,
Western Australia, Euphausia hemigibba and Pseudeuphausia latifrons were found fromthe humpback whales (Dall and Dunstan, 1957), and these are considered to be apossible Bryde's whales food in that locality. In the southern waters off Western
Australia, the Bryde's whales are known to feed upon Engraulis australis and/or
young mackerel, Pneumatophorus australiasicus (Chittleborough, 1959), while itchanges to mugilid fish called 'mullet' and crustaceans at Great Barrier Island in
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

17

the Hauraki Gulf, New Zealand (Gaskin, 1976). Aguayo (1965) examined first
the South American 'sei' whale at Iquique, northern Chile and found the animal
was identical to the so-called Bryde's whales but failed to show its food items except 'fluid' from the lst to 2nd stomachs.
All that the food items of the southern Bryde's whales having been known todate strongly suggests the animal preferable feeds upon shoaling fish of mostly commercial importance instead of planktonic organisms during their stay in the coastal or near shore waters. On the population and movements of the Bryde's whalesin the New Zealand waters, Gaskin (1977) states that " ... it is largely confinedto the area between North Cape and East Cape on the eastern side of the North
Island, and migratory only in the sense that groups of these whales appear tofollow local movements of pelagic fish schools". However, the distinct planktivorous food habits as demonstrated by the offshore form of the Bryde's whales'in
the South African waters where the animal feeds largely upon euphausiids (Best,
1977) are noteworthy. The animal of offshore form is characteristic for having ashort but relatively broader width of baleen plates while the inshore form is furnished with slender, a more sei whale-like baleen plates. Form the morphological orfunctional point of view concerning baleen plates (e.g. Nemoto, 1970), the offshore
form seems to be more adapted to swallowing type of feeding which seems to be more
effective to eat fish.
Although the baleen plates of the southern pelagic species caught by special
permit have not been studied to date the whole filter area formed by the baleenseries in the South Pacific animals caught during 1976/77 season was significantly
smaller than that found in the pelagic North Pacific animals (Kawamura andSatake, 1976; Kawamura, 1978a). This may suggest the South Pacific, Coral Sea,and possibly the Indian Ocean animals to be an identical types of baleen plates tothe offshore form of the South African waters. According to Kawamura and Satake(1976) the North Pacific Bryde's whales show two different types of baleen plates
but each of which is similar to the forms found in the South African animals although there were considerable variations from one to the another. The baleen
plates of Bryde's whales being caught in the coastal region in Japan showed generally a stronger similarity to those of offshore form while the animals in the pelagic
waters were of the inshore form. The 88.9% of totaling 109 North Pacific animals
from pelagic waters feed the Euphausiacea while 11.1 % were the fish (N emoto and
Kawamura, 1977). On the other hand, the animal in the coastal waters around
Japan feeds on variable food items by the localities but mainly focussed on both
shoaling fish such as anchovy (Engraulis japonicus), Trachurus japonicus, Afyctophum
asperum and euphausiids (E. similis, E. recurva and possibly E.pacifica) (Nemoto, 1959).
In the eastern North Pacific off Baja California, the Bryde's are reported to feed
upon the red crab, Pleuroncodes planipes and anchovy, Engraulis mordax (Rice, 1977).
These above mentioned evidences may suggest that the Bryde's whales of occurring in the coastal waters of both hemispheres are considered to be a distinct
ichtyophagous animals among all of the balaenopterid whales, i.e., the Bryde's
whale seems to feed upon whatever the organisms of greater availability or encountSci. Rep. Whales Res. Inst.,
No. 32, 1980

18

KAWAMURA

ered frequently in the surrounding environments. In this connection such the morphological characteristics of baleen plates as found in both allopatric forms by nomeans determine the kind of food species, and these perhaps mean the lesser ecological functions in the food preference throughout the whole population of the Bryde's
whales. An instance that ichtyophagous inshore form of Bryde's whale feeds aneuphausiid, Nyctiphanes capensis in the South African waters (Best, 1977) suggests
the animal preys upon simply due to the abundant distribution of N. capensis in the
neritic waters (Brinton and Gopalakrishnan, 1973).
As observed in this study it was only the Euphausiacea that was taken largelyby the Bryde's whales in the pelagic waters as the main dietary organisms of the
Bryde's whales over the central South Pacific, Coral Sea, southwest and equatorial eastern Indian oceans. In general the food of tunas and skip jacks occurringin the Pacific equatorial regions is composed of young or larval forms of many kindof fish, cephalopods and planktonic crustaceans other than euphausiids which areof minor importance, although the larval fish feed largely on zooplankters (Shirota,
1975 ). These might resulted from the difference of feeding types of animals as thefilterer and/or the attacker, but also came from the difference of ambient biomass ofeach prey organism and diel feeding activity of predators (Roger, 1973b). Even
young fish of various kinds in the tropical pelagic waters by no means forms such
school or aggregations of enormous biomass as usually found in euphausiid swarms.
The fish usually shows more dispersed distribution than the euphausiids but may
give fairly larger biomass by the individual basis (Nemoto and Kawamura, 1977).
This may be more beneficial for the attack-feeder than for the filter-feeder. The
baleen whales cannot but feed upon euphausian swarms, which may occur under
the strongly and locally biassed conditions. Although some copepods such as
Clausocalanus arcuicornis seems to occur numerously in the Central Pacific (Chiba
and Hirakawa, 1972), and actually both C. arcuicornis and C. laticeps have been foundas the food ofsei whales (Best, 1967; Kawamura, 1974). Even so, there seems little
possibility of occurring any kind of prey organisms except euphausiids for thebaleen whales in the pelagic region of the tropical to subtropical waters where noplanktivotous and school forming fish stocks hardly be exist. The possible total
amount of available euphausiid food per head of animals in the tropical sea regionin terms of occurrence freguency of animals was 44-7 5 % (Table 1), and this ishardly comparable with that of 70-90% found in the feeding grounds in boreal orcolder seas (e.g. Kawamura, 1978b).
The concentration or the feeding of Bryde's whales took place was spotted insome local area while the euphausiid species in general distribute widely over thewhole South Pacific and Indian oceans in question (Brinton, 1962; Brinton and
Gopalakrishnan, 1973). To see the distinct mono-specific composition of stomach
contens, it is clear that the euphausiid species actually fed by the Bryde's whales
are considered to be the swarm forming species that distribute numerously in theepipelagic and/or meso-pelagic waters.
According to Brinton (1962), E. recurva shows biantitropical distribution in
the Pacific but somewhat scarce in the southern hemisphere. The day-night depth
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S. WHALES

19

distribution of this species is biassed in the upper 100 m during the night but it isbelow 140-700 m during the day, and he (Brinton, 1962) found only daytime aggregations of furcilia larvae below 140 m. T. gregaria, one of another importantfood species of the Bryde's whales in the South Pacific may occur between 25-300 m
during the night but it is below 500 m during the day. E. diomedeae, the only foodspecies both in the Coral Sea and equatorial eastern Indian Ocean is found 10140 m during the night but this species goes down to deep far below during the day.
The rest euphausiid species fed by the whale may demonstrate a similar pattern ofdiel depth distribution or the species known as the lesser migrant such as P. latifrons(Brinton, 1962). The Brinton's findings suggest a scarcity of the whales food during
the day. The diel changes in stomach conditions, however, strongly suggest thata possible daytime feeding of whales actually took place in all five different whaling
areas (see Fig. 2). This may lead to a consideration that those food euphausiid
species may come to or be stationary close to the surface layers even the daytime atleast when they aggregate to form the patchy swarms. However, it is still unknown
that the aggregation of euphausiid species is related to their feeding, since active
feeding intensity in the shallower layer in E. diomedeae and T' da tricuapidata is concentrated during the night later than 20 hrs (Roger, 1973c). The occurrence of
sperm sacs in female or in both sexes of those species might have possibly related
to their aggregations at such a shallower layer as to be fed by the whales during the
austral summer. Even so, it is curious that any species of the genera Stylocheiron and
Nematoscelis were not fed by the whales while only these genera having been known
to occur abundantly during the day in the tropical South Pacific Ocean (Roger,
1973d), and actually ichtyofauna of Gempylidae, Paralepididae, and Bramidae
feed largely upon Stylocheiron and Nematoscelis (Roger, 1973b). The catches in thesouthwestern Indian Ocean represents only the materials collected in the austral
autumn while other four collection areas are early summer. The food species foundin each local and seasonal set of the catches and the magnitude of stomach fulness,were not different each other. This may lead to a consideration that there might
be very few seasonal changes in the availability of food euphausiids in terms of both
quality and quantity. The abundance of euphausiids in a magnitudes of ordinalbiomass by no means of any importance for the baleen whales but surface swarms
of several hundreds to thousnads times of biomass per unit volume of water must
be expected over the study areas as the similar case found in the copepod food(Kawamura, 1974).
The complicated occurrence of euphausiid food in the equatorical eastern
Indian Ocean may largely be due to the characteristics of zoogeography in the
Inda-Pacific regions. The eastern Indian Ocean ground was situated within theranges of the South Equatorial Current systems to which strong westerly currentof Pacific origin may flow via the Arafura, Banda and Java seas (Wyrtki, 1973).
Although the distribution of zooplankton biomass in this region varies with seasons
under the influence of southwestern or northeastern monsoon, the whaling area inthe eastern Indian Ocean was corresponded to relatively larger biomassed planktonrich region especially during October-November (Rao, 1973). Studying the mysids
Sci. Rep. Whales Res. Inst.,
No. 32, 1980

20

KAWAMURA

and euphausiids in the eastern Indian Ocean, Taniguchi (1974) actually found afairely complicated faunal composition in the waters south of Java Island and pointed out that the diversity of species composition in the area is mainly due to the inflowof the Banda Sea waters. Among the euphausiids species that showed the mostfrequent occurrence in the region as reported by Taniguchi (1974), three food species for the Bryde's whales, T'da tricuspidata, P. latifrons and E. diomedeae were included. Only E. sibogae is reported to be of minor importance by lesser magnitudes ofoccurrence (Taniguchi, 1974). The lesser occurrence of the genus Euphausia asfood of Bryed's whales in the eastern Indian Ocean agrees well to the findings by
Taniguchi (1974), and this along with the ocean current systems may further related to the faunistic characters of the Euphausiacea in the Sulu Sea region (Ponomareva, 1976). Brinton and Gopalakrishnan (1973) found the abundant distributionof P. latifrons, that was the commonest food species in the equatorial eastern Indian Ocean during November-March and noted the region as "a typical parts ofthe distribution". Ponomareva (1972) also showed the eastern equatorial Indian
Ocean including southern waters off Java Islands as the high biomassed and ecologically interesting region from a viewpoint of food chains. Brinton and Gopalakrishnan (1973) states "Essentially a neritic euphausiid, P. latifrons was nevertheless caught sporadiacally throughout the oceanic part of the tropical zone, but usually near islands". The frequencies of euphausiid occurrence as the food of Bryde's
whales in the Indian Ocean was very similar to the general geographical abundance. of each euphausiid species.
Despite the very much diversified communities, species composition and distribution of euphausiids in the tropical to temperate Pacific and Indian oceans(Mauchline and Fisher, 1969), there seems to be very little number of species thatare actually available to the baleen whales as their primaly diet in the pelagic partof those warmer sea regions. The former studies on the diet of baleen whales
made it clear that the food organisms must be the species undoubtedly aggregate
densely to form the patchiness (Nemoto, 1963; Kawamura, 1974, 1978c; Brodie
et al., 1978). From the obvious mono-specific composition of stomach contents,
E. diomedeae, E. recurva, E. sibogae, P. latifrons, and T' da tricuspidata may be refered
to as the distinct swarm-forming species. Among these members, at least T' datricuspidata, P. latifrons and E. diomedeae have been known to be the omnivorous and/or detritus feeders (Ponomareva et al., 1962; Roger, l 973c, 1978; Mauchline andFisher, 1969). The pelagic food relationships, Bryde's whale vs euphausiids, copepods vs young fish and then, young fish vs larger fish are the subject of biologicalinterests in connection with comparing those in the coastal waters and with the casein another whale species. Both biological and ecological knowledge on the euphausiid swarms along with their food habits would be one of the key subjects inthe steps of studying tropical marine ecosystems since only the genera Stylocheiron
and Nematoscelis have been known as possible swarm-forming food organisms during
the light hours of the day in the tropical Pacific (Roger, l 973e,f).

Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES21

REFERENCES
AGUAYO L., A. 1965. Bryde's whale in the Southeast Pacific. Norsk Hvalfangst-Tid., 54 (7): 141-148.
BANNISTER, J. L. and A. de C. BAKER, 1967. Observations on food and feeding of baleen whales at Durban.
Norsk Hvalfangst-Tid., 56 (4): 78-82.
BEST, P. B. 1960. Further information on Bryde's whale (Balaenoptera edeni Anderson) from Saldanha Bay,South Africa. Norsk Hvalfangst-Tid., 49 (5): 201-215.
BEST, P. B. 1967. Distribution and feeding habits of baleen whales off the Cape Province. Invest/ Rep. Div.
Sea Fish. S. Afr., 57: 1-44.
BEsT, P. B. 1977. Two allopatric forms of Bryde's whale off South Africa. Rep. int. Whal. Commn. (Special
Issue 1): 10-38.
BRINTON, E. 1962. The distribution of Pacific euphausiids. Bull. Scripps Instn. Oceanogr., Univ. Calif., 8 (2):51-270.
BRINTON, E. and K. GoPALAKRISHNAN, 1973. The distribution of Indian Ocean euphausiids. In: B.
Zeitzschel (ed.) The Biology of the Indian Ocean., Springer-Verlag Berlin, Heidelberg, New York: 357382.
BRODIE, P. F., D. D. SAMEOTO and R. W. SHELDON, 1978. Population densities of euphausiids off Nova
Scotia as indicated by net samples, whale stomach contents, and sonar. Limnol. Oceanogr., 23 (6): 12641267.
CHIBA, T. and K. HIRAKAWA, 1972. Classification and communities of the zooplankton in the South-Western Pacific Ocean, with special reference to copepods. j. Shimonoseki Univ. Fish., 21 (1): 67-80.
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DALL, W. and D. DUNSTAN, 1957. Euphausia superba Dana from a humpback whale, Megaptera nodosa (Bonnaterre), caught off southern Queensland. Norsk Hvalfangst-Tid., 46 (1): 6-12.
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Sci. Rep. Whales Res. Inst.,
No. 32, 1980

FOOD OF BRYDE'S WHALES

23

APPENDIX TABLE I. NUMBER OF ANIMALS BY THE QUANTITY
OF STOMACH CONTENTS AGAINST LOCAL CATCH TIME
CORAL SEA (1976/77)

c0.
s
i:Ll

..i::

B
(';j
u

......
0

.§"'
OJu
0

....:I

Quantityless than (%)
25

50 75 100

Total
with
food

c0.
s
i:Ll

I

4
4
4
I
2

5
6
7
8
9
JO
II
12
13
14
15
16
17
18

SOUTHWEST INDIAN
OCEAN (1976/77)

SOUTH PACIFIC (1976/77)

2

Quantityless than (%)
25

50 75 JOO

6
12
3
3

2
4

5
4
4
3
3

2
4

2

2

2

3
2

2

25 50 75 100

5
3
6

7
16
6
9
2
7
3
5

4
5
6
8
8
JO
4
4

3
2

Quantityless than (%)

I

8
20
5
3

3

3
2

2

c0.
s
i:Ll

Total
with
food

2
2

I
7
3
2
I
2

3

2

Total
with
food

2
7
12
12
2
3
6
3

APPENDIX TABLE II. NUMBER OF ANIMALS BY THE QUANTITY
OF STOMACH CONTENTS AGAINST LOCAL CATCH TIME
SOUTH PACIFIC (1977/78)
Quantity less than (%)
Empty
25

..i::

B
(';j
u

......
0

.§"'
OJu
0

....:I

6
7
8
9
JO
II
12
13
14
15
16
17
18
19

5
6
7
7
5
3
3
4
2
2
3
4
2

50

75

JOO

EASTERN INDIAN OCEAN (1978/79)
Total
with
food

25

50

75

JOO

2*
3*
3
2
3
2

2
3
4

2
3

2
2
2

2
2

2

2
2

3
5
3
7
9
2
3
3
7
8
7
2

* one stomach by fish food is included.

Sci. Rep. Whales Res. Inst.,
No. 32, 1980

Quantity less than (%)
Empty

6
9
5
4
3
5
2
4
JO

9
4
6

4**

2
2*
3
2
I*

2
2
2*
2

Total
with
food

4*
4
3
3

I

2
2
2

6
4
2
2
3
5
9
6
7
6

* one stomach by fish food is included.
** two stomachs by fish food are included.