HUMAN ACTIVITIES DISTURBING NATURALMIGRATION ROUTES OF WHALES*MASAHARU NISHIWAKI
Department of Marine Science, University of the Ryukyu, Okinawa

AND
AKINOBU SASAO
Ocean Research Institute, University of Tokyo, Tokyo

ABSTRACT

Trying to prove human activities which disturbed natural migration routesof whales, two populations of whales were investigated.
In Tokyo Bay area, annual catch numbers of the Baird's beaked whale(Berardius bairdii) in Boso whaling ground are between 50-300. Although
the whales have shown no sign of average body length decrease, (Nishiwaki
and Oguro 1971 ), apparent decrease of whales caught inspite of increasing CatchPer Unit Effort makes us no other way, accept the fact that the maritime
transportation disturbed the migration routes of whales of this stock.
Same is true in the northern coast of Kyushyu. Reason of catch decrinein the present investigation can not be considered as damage to the minke
whale (Balaenoptera acutorostrata) stock caused by whaling. Catch Per Unit
Effort is, as a whole, in an up surging, but the number of whales caught is decreasing without average body length decrease.
Great number of vessels are coming into and going out of the both areas
and the number is still increasing. Not only those whales, but also various
species of marine mammals may be troubled by the busy traffic. The result of
this investigation would be a warning to the countless activities by men,which disturb or expel wild animals from their natural inhabiting ground andmigration routes everywhere in our environment.
INTRODUCTION

Handreds of years ago, when human population was moderate and people did not
try to catch whales, many species of big whales which by nature favored to breedin temperate or warmer waters, may have entered into lagoons and inlets of Japan.
Evidences of half fossilized whale skeletons have been found at many places along
the coast of the Inland Sea, in the western K yushyu Island and even on the coastof Tokyo Bay. At present, however, there are very few sighting reports of big* This report was submitted to FAO/ACMRR/MMWP and taken up as No. 124 by the Scientific Consultation on the Conservation and Management of Marine Mammals and their Environment, Bergen, 1976
and published in the Scientific Report of Whales Research Institute .because publishment of the Proceedingsof the above conference is later than that of WRI, and earlier publishment was desired.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 113-120.

114

NISHIWAKI AND SASAO

whales in those areas.
In 1969, a stray calf of the bowhead whale came into Osaka Bay and was accidentally caught by local fishermen (Nishiwaki and Kasuya 1970). The incident
was a proof of the natural preference of this species which had favored the temperate waters of the Inland Sea.
At Scammon's Lagoon, Baja California, gray whales had come abundantly tobreed in former days. However, when the rumour of this phenomenon spreadamong people, not only scientists but also a large number of general people
gathered to see the whales. Disturbed by the sightseers, it was reported, that the
number of whales coming to the lagoon had apparently decreased. The incident
was one of disturbances, not by whaling activities, but by another human action
affected the whales.
Trying to prove human activities which disturbed natural migration routes ofwhales, we investigated the two populations of whales, the Baird's beaked whale(Berardius bairdii) in Boso whaling ground and the minke whale (Balaenoptera acutorostrata) in Yobiko whaling ground, both of which did not receive a serious damage
by whaling, but affected by the increasing number of ships and boats coming inand out or passing near by the whaling grounds (there are very few whale population which have received no harm from whaling).
INFLUENCES OF VESSELS OVER THE BAIRD'S BEAKEDWHALES IN BOSO WHALING GROUND

Baird's beaked whale catch has been operated from land stations in certain limitedareas of Japan. One of such whaling grounds is Boso ground in Chiba Pref. The
ground is only 20 miles distant from the mouth of Tokyo Bay. Coast of Tokyo
Bay is dotted with commercial, naval and fisheries' ports. As shown in Fig. 1, there
140°E

142°E

JAPAN

36°N

PACIFIC
OCEAN
34°N

32°N
142°E

Fig. I. Boso whaling ground and the main course of vessels in and out of TokyoBay.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMAN ACTIVITIES DISTURBING WHALESTABLE I.

ANNUAL NUMBER OF VESSELS ENTERED THE PORTS
Tokyo Bay Area

Northern coast of Kyushyu

Year
Tokyo

1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974

11941
11301
13797
13913
12625
13957
15038
15116
12066
20649
22813
27360
31776
32767
31358
33936
45886
53381
57356
64502
68894
70158
78816
76586
79763
81689
72222

115

Yokohama Yokosuka

5870
12507
14723
16262
21093
20009
17118
22953
26737
28384
30573
37120
45121
45644
50649
60078
71087
76039
88238
99691
106721108427104742101537102946
93987

3521
1768
3228
3806
6220
7182
8337
8101
9156
10063
12408
14690
16085
16206
16114
16223
19136
24719
27880
26404
24556
27549
28243
28632
26225
27673

Chiba

3744
6306
4155
6708
9479
11198
9942
18513
31237
32241
33500
39480
35336
60065
73713
72098
77347
87185
80827

Dokai Area Kokura

41756
37132
58467
47441
42926
49788
72641
10391
72450
75743
63310
65657
70136
71648
69944
67224
76418
76544
68172
64064
58037

15330
14108
12849
30427
29211
28211
28192
18858
29398
27165
27394
29265
28117
28354
29952
28792
30013
26424
23450
25034
25994

Moji

Shimonoseki

17738
34839
33884
13156
40612
47807
44655
43447
27857
27564
43600
42820
45100
77778
66141
65720
62430
55807
65530
84363
62448

5199
11478
90886
11333290239
96694
100046
56812
42382
47460
80323
77185
78151
75664
77257
77317
75909
74237
72665
71059
73913
65317
64124
65993
71576
69319
66845

are Tokyo, Kawasaki, Yokohama, Yokosuka, Chiba, Kisarazu, Uraga and Kurihama Ports. Various ships and boats which are coming into those ports, mustenter the mouth of Tokyo Bay. A list of a great number of vessels of over 5 tons isshown by the year in Table 1. Moreover, all boats which once enter into the Bay,
must inevitably go out. So, the number of boats must be considered as twice asmuch to become an amazingly big number. Although it was difficult to get datafrom every port of Tokyo Bay area, general circumstances of maritime transportation around the Bay might be understood with this table. Actual number of theboats was, of course, much more than the indicated number. In the year when
100 whales were caught, the number of boats coming into Tokyo Bay was about
250,000. That is, one boat per minute was passing through the mouth of the Bay.
In Fig. 2, annual number of vessels entered into Tokyo Bay is compared withthat of Baird's beaked whales caught at Boso whaling ground since 1948 till 1974.
These numbers are averages of every three years. This method makes the curves
smoother and the curves show the tendencies more clearly.
As it is also indicated in Fig. 2, CPUE (Catch Per Unit Effort) has been increasing in the years. The reason of the remarkable increase of CPUE between
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

116

NISHIWAKI AND SASAO
300,000.5'O.,,...
~.,,

15

300

f".,

I

.,,...

0

i

0.

j:i

200,000

"'""

::>
u

~
u

:fl

!

"

. ,,

i

10 g 200

]

.'G.

'

.i i

5 0100
~·

....

"'·'~

,:;,.'v......
•<'.,;:x.•·····X•·-··-•X'"

0

t

0

1949

1952

1955

1958
Year

1961

1964

1967·

1970

1973

Fig. 2. Annual number of vessels entered into Tokyo Bay compared with that of
Baird's beaked whales caught from Boso whaling ground.

1961 and 1964 was that, small tonnaged (15-20 tons) catchers were abolished andbigger (30-50 tons) catchers were taken up for operation. Accordingly, numberof catchers decreased, instead, capability per boat increased. Nevertheless, thepopulation seems to have shown no sign of receiving damages during the 25
years, although biological examination on those whales caught has not been done
every years. Annual catch numbers are between 50-300. The numbers arerather small, but the whales have shown no sign of average body length decrease(Nishiwaki and Oguro 1971). Considered the increasing CPUE and apparent
decrease of whales caught without population damage, we have no other way,
accept this phenomenon as a fact that the maritime transportations have disturbed the migration routes of the Baird's beaked whale.
MINKE WHALES IN YOBIKO WHALING GROUND AND MARITIME
TRAFFIC ON THE NORTHERN COAST OF KYUSHYUIn the northern part of Kyushyu Island, local people have had a habit of eating
whale meat since more than four hundred years ago. Among the species of whales
coming near to the coast, minke whales are relatively fearless and even coming into
set net to be an easy harvest for fishermen. The meat of minke whale was a very
important protein resources at the time of devastation just after World War II:
minke whale meat was a necessary food in northern Kyushyu and consumed abundantly. Whaling on minke whale is usually done by small boats of 15-20 tons
with 35-50 mm harpoon guns. The whaling ground is naturally limited within
30 miles from the shore (Fig. 3).
Fortunately, the record of the body length of minke whales caught in this area
since 1948 has been kept to date, and was very important reference to our investigation. It was very difficult to grasp a number of vessels coming in and out of all
the ports in Northern Kyushyu. As main transportations of this area, numberof vessels coming into Dokai district (Yahata, Wakamatsu and Tobata), Kokura,
Moji and Shimonoseki Ports, were investigated. Fig. 4 shows a relation between
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMAN ACTIVITIES DISTURBING WHALES

129'E

36'N

131'E

SEA
OF
JAPAN

REPUBLIC

OF
KOREA

35'N

34'N

33'N

33'N

131'E

Fig. 3. Yobiko whaling ground and ports of Northern Kyushyu on the coast of
Korean Strait.
ti

250,000£

200,000

"'u0

100

.

\
50,000 iil

§

/

/

•\,...- ....!

P-'""'\_.,/I"-·-et""· \

\.
\

\,
z QiL-1~94-8~'-...---1~95-0~~-19~5-2--'~l-9~54~-'--1~9~56~-'---1~95-8~'---1~96-0

0 ~

Year

Fig. 4. Relation between the incresing number of vessels and that of the decreasing
whales caught in Yobiko whaling ground since 1948 till 1957.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

117

118

NISHIWAKI AND SASAO

the increasing number of vessels and the decreasing number of minke whalescaught in Yobiko whaling ground. Similar number to that in Tokyo Bay, 250,000
vessels came to those ports in the most prosperous years. In Fig. 4, actual numbers of whales caught are used, not averages of every three years. So, the curves
are not so smooth as those in Fig. 2, but the tendency of traffic and catch number
might be recognized.

JO

Number of whales caught by year
lOO .--"r20-'Tl5,_,lr-O'f-5-¥-0-415""-'l!'-O'f-5-'i-0--'l'i'-O+5-¥0~1T-O_,,_5-¥0_1'+0-¥5--iOi-'lT-5¥10-T5'-'0f--¥10_,5~0r--""1'10--i5,_0J-_.,10~5,_0J-~5f-10

31
29
28

27
25

t:0

fil
~24 13
~

<:23

§

'§

~ "&5

-~

7,;"' 20 ~0

=f21 "'
u

't:J

50

~

"'u "'u"' c;;"'~..c:: 19 ~~ "O ..c::"' ·..c::~ ;;: ;;:OJ";:'.,11
't:J
0

.0

.8 15
~

OJ

]16 "O"O...OJ ...OJOJ""..."'

.0

.0

§
z" z
E

OJ

~ 13 ~

t i f
14

0

0

1952
Year

1954

1956

Fig. 5. Annual number of whales caught, its body length distribution and average
body length with CPUE in Yobiko landstation during the period 1948-1957.

We would like to discuss at this point whether that decline of catch in Yobiko
was caused by whaling damage on the minke whale stock. Fig. 5 shows the annual size distribution, average body length and number of whales caught with
CPUE since 1948 till 1957. The data of whales caught were exclusively bodylength without physiological records such as maturity or pregnancy. The numberof whales caught were rather small in most years, especially in 1957. Very little
can be presumed only from size distribution of each year. However, if the size
distribution of all whales caught during the ten years period is observed collectively, whales can be divided into groups. Each peaks of size distribution appears at
the body lengths 15, 18-20 and 23-24 feet respectively. These peaks are considered to be groups of yearings, the one to two years old and the older than three
years. At that time, minke whale whaling in Japan was not restricted by regulations. So1 females and calves were caught together. But in later years of theperiod, number of yearings became smaller: disturbed frequently by increasing
maritime transportations, mothers with calves must have detoured the coast of
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

119

HUMAN ACTIVITIES DISTURBING WHALES

northern Kyushyu.
Record in 1947 is unknown. In 1948, 93 individuals were caught. Then
Korean War broke out in 1950. Number of vessels coming to Northern Kyushyu
in 1950 was triple times as much as the number in 1949. The least catch in 1950
was not because exclusively of disturbing maritime traffic, but also of various industrial reasons, including munitional boom. In other words, wages from suchindustries became more profittable than those from whaling, so whalers switched to other employments in those years. Conditions were similar in 1951 and1952. In 1953, the war stopped and the munitional boom gradually ceased.
However, number of vessels showed little decrease. Whalers of the ground saw
unstable status of their whaling desperately and wanted to move to some other district. One catcher boat moved to Ushizu, Ishikawa Pref. in 1950 and caught fiveminke whales (average body length of them was 20 feet), then other two followed
in 1951 and caught 25 individuals (average body length of them was 23.3 feet).
In 1956, one whaling boat of Yobiko made an expedition to southern islands of
Kyushyu as far as Naze, Amami-Oshima and caught 19 individuals (average bodylength of them was 25.0 feet). Finally whalers of Yobiko whaling ground gave up
the entire ground and all except one moved to the far northern district, Wakasa
Bay, Fukui Pref. And though remained one worked, caught only two individuals
in the following year. Then Yobiko whaling was ceased at all.
TABLE 2. ANNUAL NUMBER OF CATCHER-BOATS, WHALES CAUGHT WITH
AVERAGE BODY LENGTH AND CPUE IN YOBIKO WHALING GROUND
Year

1948

1949

1950

Number of catchers
Number of whales caught
Average body length in feet
CPUE

10
93
17.8
8.5

7
39
17.0
5.6

5
17
17.7
3.4

1951
5
20
20.0
4.0

1952
6
43
19.3
7.2

1953

1954

6
43
20.1
7.2

6
31
20.5
5.2

1955
5
28
21. 7
5.6

1956
6
37
20. 7
6.2

1957
2
18.0
2.0

Again, reason of the catch decline can not be considered as damages caused
by whaling to the whale stock. As it can be understood from Fig. 5, though
CPUE has been flactuated by the years, as a whole, it was in an up surging, but
average body length of the population showed no sign of decrease, or even showedmcrease. We would like to introduce here a letter from Mr. S. L. Bowen addressedto the senior auther written on 18th April, 1972. He was then an army soldierdispatched to Korea. He had had interest in the gray whale and its status andconditions. He told Nishiwaki that in 1970, total number of whales caught fromthe whaling ground adjacent to Ulsan was 740, among them, 715 were minke
whales. It may be safe to presume that the stock of minke whales there was identical population to the Y obiko stock. Distance between the two grounds is little
more than 100 miles. If the number which Mr. Bowen indicated, is right, cause of
Yobiko whaling decline (they caught, at most, 100 a year since 1948 till 1957) was
not by damages on the minke whale stock by whaling activities. At present,minke whale whaling can not be operated in the Y obiko whaling ground, eastern
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

120

NISHIWAKI AND SASAO

channel of the Korean Strait, but is still prosperous in the Ulsan whaling ground,
the western channel of the Korean Strait. Considered the experience in Yobiko
whaling ground, one can hardly deny influences of maritime traffic to the minke
whales. As great number of vessels which belonged or connected to the Northern
Kyushyu Industrial Zone, in which Moji, Tobata, Yahata, Karatsu, Sasebo andNagasaki, biggest ports of Japan, are included, are coming in and going out andthe number is still increasing, various other species of marine mammals may betroubled similarly by the busy traffic.
CONCLUSION

Naturally, there might have been other additional factors of influences which affected the whale populations to some extent. But, at least, result of the present
investigation shows apparent disturbances by ships and boats to the migrationroutes of Baird's beaked whales in Boso whaling ground and minke whales in
Yobiko whaling ground.
The result of this investigation would be a warning to the countless activities
by men, which disturb or expel wild animals from natural inhabiting grounds andmigration routes everywhere in our environment. As well as aerial and landtransportations, maritime traffic is another environmental problem. Damages bywhaling has been so controvercial in recent years, but those by maritime traffic
tends to be overlooked. From the view point of ecosystem, maritime influences
to animals are not small, but little countermeasures to those have been taken up
till now.
REFERENCES
BOWEN, S. L., 1972. Personal communication.
CHIBA PREFECTURAL OFFICE, 1948-1974. "Chibaken Tokei Shiryo" (Statistical Data of Chiba Prefecture)(in Japanese).
DEPARTMENT of RESEARCH and DATA PROCESSING, MINISTRY of TRANSPORTATION, GOVERNMENT of JAPAN,
1948-1974. "Nippon-Koku Kowan Tokei" (Harbor Statistics of Japan) (in Japanese).
KANAGAWA PREFECTURAL OFFICE, 1948-1974. "Kanagawaken Tokei Shiryo" (Statistical Data of Kanagawa Prefecture) (in Japanese).
NISHIWAKI, M. and T. KASUYA, 1970. A Greenland right whale caught at Osaka Bay. Sci. Rep. Whales Res.
Inst., 22 : 45-62.
NISHIWAKI, M. and N. 0GURO, 1971. Baird's beaked whales caught on the coast of Japan in recent 10 years.
Sci. Rep. Whales Res. Inst., 23 : 111-22.
STATISTICS DIVISION, MINISTRY of AGRICULTURE and FORESTRY, GOVERNMENT of JAPAN. Agriculture, Forestry
and Fishery Statistics Data 1948-1974. Association of Agriculture and Forest Industries.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.