THE OCCURRENCE OF THE PHOCID SEALS ALONGTHE COAST OF JAPAN AND POSSIBLE
DISPERSAL OF PUPSY ASUHIKO NAITO
Kominato Marine Biological Laboratory, Tokyo University of Fisheries,
Amatsu-kominato, Chiba.

ABSTRACTThe distribution of the phocid seals was studied both outside area
and in the border area of their habitat. Sixteen catch or observation
records from Honshu, Shikoku and Kyushu of Japan were examined.
Three species appeared, the ice-breeding harbour seal (Phoca vitulina),
the ringed seal (Pusa hispida) and the bearded seal (Erignathus barbartus)
occurred while the land-breeding harbour seal (Phoca vitulina) and the
ribbon seal (Histriophoca Jasciata) did not occur in those areas. In theborder area of the habitat, all four species of the ice-breeding seals
occurred. These seals were mostly pups indicating that the new born
pups spread their distribution after ice season being carried by the ice
floes and some of them occurred far south from their habitats.
INTRODUCTION

The author has studied the pagophilic (ice-breeding) and the pagophobic (landbreeding) harbour seals (Phoca vitulina) comparing their ecology and morphology. The pagophilic form annually shifts their habitat from the edge zone ofdrifting ice to coastal area, while the pagophobic form stays at the same habitat(coastal) even in breeding season. These differences of their life systems between two forms may strongly relate with their adaptation systems, especiallyin the period of new born pups. In the pagophilic form the shift of habitat
occurs several weeks after their birth, and during this short period, importantlife events occur on the new born pups such as suckling, weaning, moulting,and moreover physical and morphological changes. It is the problem that these
events are performed on unstable ice floes in the edge zone of the drifting ice.
If the shift of habitat was unsuccessful processing these events, as Naito andNishiwaki (1972b) suggested, the pups would be carried away by ice drift so as
to spread their distribution. In the pagophobic form, however, such habitat
shift does not occur, and mother-pup relationship continues longer to result thesteady and successful weaning and independent life of the pups. Therefore,
the pup distribution of this form is settled.
The present study is aimed to examine the above understandings by studying the distribution of these seals (including other species) in the border areaof their habitat and also out side of the border.
Sci. Rep. Whales Res. Inst.,
No. 28, 1976, 175-185.

NAITO176

DISTRIBUTION OUT SIDE OF THE BORDER OF THE HABIT AT

The present study deals with occurrences along the coast of Japan other than
Hokkaido (Honshu, Shikoku and Kyushu). Catch or sighting records of theseals along the coast of Japan other than Hokkaido are rare and scarce, so it
is difficult to collect such records. In the present study records and informations
were collected from following three sources. (1) The newspaper or T.V. broadcasting as a local news ; the seals in these areas are very strange animals, therefore if they were caught or sighted such seals were sometimes reported by them.
(2) Aquariums; if the animals were caught alive, they were usually sent to theaquariums near by for display, and aquariums kindly sent me the informations
to my requests. (3) The prefectural fisheries research station or local museum;the catch or sighting informations by local people were given to them. As tothe biological informations, species, date, place and length or approximate length
were available from above informations. However, to my regret, sex, bodyweight and age determined from canine teeth are unknown.
Appeared species
Three species, bearded seal, ringed seal and harbour seal were accidentallycaught or sighted along the coast of Honshu, Shikoku and Kyushu (Fig. 1).
Only two bearded seals were recorded at Akita and Niigata of the Japan Sea
coast of the Northern Honshu, and there are no records from Shikoku andKyushu. Out of 5 records of ringed seals, two were from Japan Sea coast of
Honshu and two were from Pacific Ocean coast of Honshu and Shikoku. The
130°E

14d'E

150°E

45°N

45°N

•
40°N

40°N
PACIFIC OCEAN

35°N

140°E

150°E

Fig. 1. Some catch or observation records of the phocid seals from the coastof Honshu, Shikoku and Kyushu of Japan and others.
the ice-breeding
harbour seal; .A., the ringed seal; •• the bearded seal.

e,Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

PHOCID SEALS ALONG THE COAST OF JAPAN

177

far south record was from Fukuoka-city, Kyushu. Nine ice-breeding harbour
seals were recorded. Out of nine, 6 seals were recorded from the Pacific Ocean
coast of Honshu and only one seal was from Japan Sea coast of Honshu. None
were recorded from Kyushu. In the present study, records of occurrences fromJapan coast other than Hokkaido were dealt with as a materials, however, in
this chapter additional two examples were also included. One was the catchrecord by fishing boat from the Pacific Ocean, about 300 miles from the coast.
The other is sighting record by research vessels at the mouth of Port Hakodate,the most south of Hokkaido. From above records, it is supposed that the ringed
seal and the ice-breeding harbour seal occur more often and futhermore south
than the bearded seal, but it is quite difficult to get any conclusion as to themigration route of these seals from their habitat towards southern areas. The
most stressed facts in this chapter is that none of the ribbon seals which are as
popular as the ice-breeding harbour seal in the Sea of Okhotsk, and none of
the land-breeding harbour seal of which habitats distribute in the furthest southof Hokkaido, were recorded in the coast of Honshu, Shikoku and Kyushu.
Appeared season
The seasons when the seals occurred along the coast of Honshu, Shikoku
and Kyushu were shown in Fig. 2. In this chapter, the seals were not treatedseparately by species but as a total records of 3 species were treated, andaddional 2 records of the ice-breeding seal from the Pacific Ocean and the portof Hakodate were excluded because they were not the records from intended
area (Honshu, Shikoku and Kyushu). As shown in Fig. 2, the seals begin to occur
from April at 12.5% frequency, and the highest frequency was 25% in May.
After May seals decrease to occur. In June and July 18.7% of the total occurred

25.0

4
Ul

0:I

3

"U

>
iJ
c

0
.....
Q)

2
1

..0

E
::I

z

J

F M

A M

J

Fig. 2. The seasonal appearance frequency of the seals occurred along the coastof Honshu, Shikoku and Kyushu. Numbers were shown in percentage. Dottedspace shows the ice-breeding harbour seal; horizontal line, the ringed seal;vertical line, the bearded seal.

Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

NAITO178

respectively and none of seals occurred in December. Seventy five percent
seals of all occurred from April to July. Being still short data, from mentioned
above, the following two problems were indicated. 1) The seals begin to occur in
April. This time well corresponds with after-season of drifting ice in Hokkaido.
2) The seals decrease to occur after May. This may indicate that the smaller
number of seals occur in later season in farther south area. The problem 1)
will be discussed later. The problem 2) may be explained by Fig. 3. In
M

A

•
•

N.HONSHU

S. HONSHU

SHIKOKU

J

M

-·

J

A

AA

A

0

N

•

D

9
64.3°/o2
14.3°1o••A•

KYUSHUs2
14.3°1oA

7.1°1oFig. 3. Time difference of the first occurrence between each area. The seals
begin to occur from north. They occur in Northern Honshu at ffrst and in
Kyushu at latest.
the ice-breeding harbour seal; .A, the ringed seal; . ,the bearded seal.

e,Fig. 3, the area where the seals recorded were separated to. four districts,
from north to south; northern Honshu, southern Honshu, Shikoku and Kyushu.
Honshu was sepatated by the line between Boso Peninsula and Noto Peninsula.
As shown in Fig. 3, in northern Honshu 9 seals (64.3%), in southern Honshu
and Shikoku 2 seals (14.3%) in each and only 1 seal in Kyushu were recorded
respectively. Furthermore, the seals were recorded from earier season innorthern Honshu, and in Kyushu it recorded in latest season. From all above
mentioned, it is suggested that the seals move towards south from main habitatin the Sea of Okhotsk and the adjacent waters.
Ages of the seals recorded
In the present study, age informations based on examination of canine toothwere not available. Only measured body size or approximate body size wasused for growth developmental class estimation. In general it is difficult toestimate ages by body size, however, body size indicates such growth stages aspup, young subadult and full adult. Tikomirov et al. (1969) showed the growth
curves of the bearded seal, ringed seal and the ice-breeding harbour seal. Naito
and Nishiwaki (1972) also showed the growth curves of the ice-breeding harbour
seal. From these curves and the measured body size or approximate body size
shown in Table 1, the growth developmental classes were possibly estimated tobe pups in the ice-breeding harbour seal and ringed seal. In the bearded seals
one was young or subadult and the other was also pup.
Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

~

about 100 cm
about 100 cm

Susaki-Bay, Kochi
Miyazu-Bay, Kyoto
Kiso-River, 20-25 km up from mouth of river

' '58
' '53
. '73

Jui.
Jui.

z

0

80cm
104 cm (total length)

Kominato.Bay, Chiba
Hazaki-Beach, Kashima, Ibaragi
Kashimanada, Ibaragi

Apr. 23, '72

May 30, '49<.c:>...,.....

>
'"tl
>
z

":!

'-<

-

Jui.

about 150 cm

0

...i

VJ.

>

0

::r:
l:T:I

Q
...i

16 kg

10 kg

0

>
I:""

VJ.

I:""

>

l:T:I

VJ.

t::I

0

-

'"tl

::r:

0

85 cm (measured bymolted specimen)
femaleless than 100 cm

Ayukawa, Miyagi''54(young)- (pup)less than JOO cm-

90 cm (total lengh)

11. 3 kg
12.4 kg

120 kgBody weight

60 cm (total lenght 88 cm)

May

male

male

75. 0 cm (total length)

Port of Ayukawa, Miyagi

mouth of Hakodate-Bay Hodkaido'Pacific Ocean 43°!4 1 N; 156°34 1 E

Azirozaki-Beach Hiwasa, Tokushima

Shiratori-Beach Toyama

Creek in Tsuyasaki-Bay Fukuoka

75.0cmmale

Teisan-Cannal Yuriage, Natori-city Miyagi

145 cm180cm

Body length

100 cm (total length)

male

Sex

Senami-Beach Murakami-city, Niigata

set net Teno-cho, Akita
Port of Niigata

Locality

THE LIST OF SEALS CAUGHT ALONG THE COAST OF JAPAN.

Jun. 7, '68
May 20, '69
May
' '54

4, '752, '75

"

Jun.
Nov.

Jun. II, '69
Aug. 7, '74

Apr. 28, '68
Oct. 18, '70
Sep. 15, '73"

Phoca vitulina largha

Pusa hispida

Erignathus barbartus

Date of catch,,..

Species

TABLE 1.

~

'~"'

1'"

.~~"'

._

""~
~Co~

~ ?:

180

NAITO

THE CATCH RECORDS IN THE BORDER OF THE HABITATAs already described, the bearded seal, the ringed seal and the ice-breeding
harbour seal had occurred along the coast of Honshu, Shikoku and Kyushu,
and the ribbon seal and the land-breeding harbour seal had never occurred inthese areas. It is also mentioned that these occurred seals were mostly pups.
They begin to occur from north to south indicating the southwards moves, andthese occurrences began from April indicating some relation with the time of
habitat shift from the ice floe to the coast in these three species, because theice floes melt and disappear from mid March to mid April in Hokkaido. In
this chapter, to examine above problems more precisely the catch records byfishing nets in the border of the habitat were studied in two seasons, after ice
season and in October (6 months after ice season).
There are two border parts in Hokkaido. One is the Soya Strait whichconnects the Sea of Okhotsk to the Japan Sea, and the other is the Nemuro
Strait which connects the Sea of Okhotsk to the Pacific Ocean. The study was
performed in the Nemuro Strait which is generally known as the southern borderof the habitat of the pagophilic seals in the Sea of Okhotsk (the bearded seal,
the ringed seal, the ice-breeding harbour seal and the ribbon seal, Naito, 1969).
Especially in the ice-breeding harbour seal the lake Furen in the Nemuro Strait
area is known as the southern edge of the distribution of their hauling grounds.

The catch records after the ice season
The Nemuro Strait area are also known as almost southern limits of annual
constant occurrence of the drifting ice from the Sea of Okhotsk. The ice prevails through this strait area from early February to mid or late March, sometimes mid April when the ice is eminent (Ruhyo-Sokuho, 1969-1975). During
this season, the ice moves from north to south being carried by the wind andcurrent, and it occurs in the Pacific Ocean passing through the strait (Fig. 4).
After the ice occurred in the Pacific Ocean it melts quickly near around the
Nemuro Peninsula. However, when the ice is extensive, it is occasionally driven
as far as the Point Erimo. The ice condition in the Nemuro Strait is notconstant, and it is always drifting making open seas somewhere in this strait.
The ice floes occuring in these areas are relatively small but varied such asslush ice, ice-cake, small or medium floe berg, rafted or hummocked ice, brash
ice. These ices in these areas are capable of supplying hauling or breedingsite for the seals. However, the breeding population were found only in thearea between the Shiretoko Peninsula and the Kunashiri Island (Naito, 1969;
informations from the hunters). In this area, the dominant breeding species is
the ice breeding harbour seal and the ribbon seal, and the ringed seal and thebearded seal are quite rare (Naito, 1969). After the ice season, from May only
the ice-breeding harbour seal occurs along the coast to haul out the grass bars
making 30-70 individuals groups in Odaito and the Lake Furen which open
Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

PHOCID SEALS ALONG THE COAST OF JAPAN

181

43°N

1970 MARCH 26-28

1971 MARCH 24-27

Fig. 4. The distribution of the pack ice in its southern border at the later puping
season of the ice-breeding seals. The ice floes occur in the Pacific Ocean from thesouthern Sea of Okhotsk passing through the Nemuro Strait or near by.

to this strait.
Sampling was performed at Kanazawa Fur Company from 1969 to 1971
during later half of May and June (1969, 1970 May 8-June 30, 1971 May 11June 30) when the ice completely disappeared. The results were shown in Table
2. The seals mostly caught accidentally by fishing nets along the Nemuro Peninsula (Both coasts of the Nemuro Strait and the Pacific Ocean) were collected at
this Fur Company. Almost of these collected seals were examined in 1969 and
1970, however, in 1971 about half of the collected were examined. All 4 ice
Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

:">" ,;"'.,. .,

~~

"
~~
""~
.,,O::J ~

~

~

~

"'~-

1971

1970

1969

95.0 cm

May 28

NM 23

Sankaku

May 12
May 17
May 20

145
150
160

HanasakiMay 30June 7
May 14182
214

June 27
June 27
May 16

446
452

"
"
"
419

2

439

Ribbon seal

May 22
June

422

147

Sankaku

May 26175

78. 0 cm
85. 5 cm

femalefemalefemaleHokakemale

femaleHokakeSankaku

male

male

femalemale

91. 0 cm

99. 0 cm

98.0 cm

97.0 cm

88.0 cm

89.0 cm

89.0 cm

76 cm
104. 5 cm
male

101.0 cm

male
male

Futatsuiwa-

OnnetoOnnetoTokatan

May 24

167

Horomoshiri

May 20
May 23

male

-

165

95. 5 cm

femaleSankaku

100. 5 cm

125. 0 cm

female161

Ice-breeding harbout seal

Ribbon seal

"
"

"
"
"

femaleOnnetoIce-breeding harbour seal

"
166

male

Honioi227

Ringed seal

146.0 cm

female151. 5 cm
83. 5 cm

149.5 cm

femaleMay 14

148
Ochiishi

91. 0 cm

June 7
June 23
May 23

Sankaku

Tomoshiri

female87.0 cm

femaleMay 26

Sankaku

Sankaku

May 26NM 22

73. 5 cmmale
female-May 17

NM 10
NM 21

213

Bearded sealIce-breeding harbour seal

72. 5 cm

68.0 cm

141.0cm

femaleMay 30NM 24

femaleBody size

NemuroMay 19NemuroSankakuSex

77.5 cm

May 13

NM 5
NM 15

Locality

femalefemaleMay 21

NM 17

Date of catch

Ringed seal

Field number

CATCH RECORDS ALONG THE NEMURO PENINSULA AFTER ICE SEASON.

Bearded seal

Species

TABLE 2.

pup

pup
pup

pup

pup

probably pup

pup
pup

pup

1

pup

1

pup
1

pup
2

probably pup
probably pup

pup

pup

pup
pup

pup

pup

probably pup

pup

pup

Age

0

..,i

z

>
......

o;

""

183

PHOCID SEALS ALONG THE COAST OF JAPAN

breeding seals occurred in this area. The ice-breeding harbour seal occurredat the highest frequency as same as seen in Honshu, Shikoku and Kyushu areas.
The bearded and the ringed seals occurred at the same frequency. The ribbon
seal has never been reported in Honshu, Shikoku and Kyushu, but occurred inthis area at the lowest frequency. Concerning the ages of these seals, some were
not examined by the canine tooth, for the whole skulls were reserved andattached to the skin for the moulted specimen. However, as well as in former
chapter, the ages were estimated by the body size. In all species, the seals caught
in this area were mostly pups indicating same tendency seen in Honshu, Shikoku
and Kyushu areas. These facts may strongly relate to the movement of ice
mentioned above. In the present study, there were no direct observation thatthe ice carried such pups through this strait to the Pacific Ocean. However,to examine the seasonal changes the author studied the distribution of these
seals in other season, October, in the same area.

Catch records in October
The sampling was performed in October 1969 (3-30) by v1s1tmg the fishingvillage when informations were brought by fishermen. The results were shownin Table 3. In this season the result was quite different from that of the after
ice season. Only two species, the ice-breeding harbour seal and the ribbon seal
were caught. None of the ringed seal and the bearded seal were caught. The
TABLE 3.

CATCH RECORDS ALONG THE NEMUROPENINSULA IN OCTOBER (1969)

SpeciesFieldnumberDate ofcatch

Ice-breeding
harbour seal

Ribbon seal

Locality

Sex

Body size

7

Ochiishimale

162. 0 cm

8

9

Habomaifemale149.0 cm

Toritoishi

female160.5 cm

3
18

Age

16

October 14

18

October 15

Tohbaifemale36

October 23

Habomaifemale

156

cm

10

39

October 26

Odaitohfemale130.5 cm40

male

133. 5 cm

3
2

41

female33
34
43

October 23
October 27

Sankaku
Sankaku

male

adult

male

153. 0 cm
132. 0 cm

male

149.0 cmadult
immature
immature

data are quite small, however as seen in Table 3, half of the ice-breeding harbour
seals were adults, which had been never caught after ice season. In the ribbon
seal the adult seal was included.
Aboves are quite short data to get some conclusion, however it is clear thatage composition of the ice-breeding harbour seal which occurred in this area
Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

184

NAITO

is quite different between after ice season and in October. In the former season,
seals were mostly pups (76.5%) and none of adult seals occurred. On the other
hand in the later season adult seals (50%) occurred in the same area. It is still
uncertain when these age compositions change, yet it is supposed that the dispersion of adult seals in this area is due to the salmon migration, because these
seals were caught by the salmon set nets which were operated from summer toautumn when the salmons migrate to the coast for their up river spawningmigration. There is no clear explanation why the bearded seal and the ringed
seal never occurred in this season. However, it is supposed that their habitats(hauling grounds) are too far north in Sakhaline (lnukai 1942) to occur in thisarea except ice season. Three ribbon seals were caught in this season, however,these seals were not caught by the coastal salmon nets but caught by the gillnets offshore in this area, and this seal is still seemed to be rare species in the
coast.
DISCUSSION
The author examined the distribution of the pagophilic seals in area outside of
their habitat and in the border area, and the followings are recognized. The
ice-breeding harbour seal, the bearded seal and the ringed seal occurred in
Honshu, Shikoku and Kyushu moving from north to south. These seals were
mostly pups. The ribbon seal has never occurred in this out side area of theirhabitat. The land-breeding harbour seal also has never occurred in this area.
In the border area of their habitat, all 4 pagophilic seals occurred along thecoast of the Nemuro Peninsula after ice season. The most of these seals were
pups. However in October in the same area, only two species, the ice-breeding
harbour seal and the ribbon seal occurred, and the adult seals occurred in highfrequency.
The present study depended on short data, however, above facts furthermore lead to the important conclusion as follows. The pagophilic seals especially
ice-breeding harbour seal (except the ribbon seal) disperse their distribution
during or after the drifting ice melted. On the contrary, the land-breeding
harbour seal which distributes along the Nemuro Peninsula to the Point Erimo
does not shows such wide dispersion not only by the pups but also by others.
These difference may due to their mode of life. The ice breeding seals shift
their habitat from ice floe to the coast except the ribbon seal. These shift
may occur pretty shortly after birth for the pups especially in the ice-breeding
harbour seal (2-3 weeks after birth), for they occupy the edge zone of theseasonal pack ice (Burns, 1970; Fay, 1972; Naito, 1972a). During this shortperiod, pups have to accomplish their life events on ice floe such as suckling,moulting of the lanugo coat and the weaning for their swimming life. The dispersion carried by the ice floes is innevitable for the pups which possess such
above life, and this periods is highly critical for their survivals. However,
perhaps for compensating these critical early stage of life, pups of these seals
Sci. Rep. Whales Res. Inst.,
No. 28, 1976.

PHOCID SEALS ALONG THE COAST OF JAPAN

185

possess the very thick blubber as energy storage (Naito and Nishiwaki, 1972b).
The pups of the land-breeding harbour seal have much more stable life. They
begin to swim soon after birth. The mother-pup relationship continues longer(about 4-6 months-Naito and Nishiwaki, 1972b; Belkin et al., 1969), and theweaning occurs gradually. Therefore the dispersion of pups may not occur.
In the present study the ribbon seal has not occurred in Honshu, Shikoku andKyushu areas. This may relate with that the ribbon seal apparently becomespelagic after the breeding and moulting season (Burns, 1970; Fay, 1972).
ACKNOWLEDGMENT

Through this work, I owed it to many people that I could collect records andinformations about wondering seals along the coast of Japan for many years.
The greatest thanks are due to many aquariums, museums, prefectural fisheries
experimental stations who are very kind to send me the valuable informations
for my requests. In the field works, I wish to thank to Mr. Nobuyoshi Kanazawa, Kanazawa Fur Company, and many fishermen who gave me informations
and chances to examine the specimens.
REFERENCESBURNS, J. J., 1970. Remarked on the distribution and natural history of pagohilic Pinnipeds
in the Bering and Chukchi Seas. ]. Mamm.,51 (3): 445-454.
FAY, F.H., 1972. The role of ice in the ecology of marine mammals of the Bering Sea. International Symposium for Bering Sea Study. Hokkaido University, Hakodate, Japan. (inpress).
INUKAI, T., 1942. Hair seals in our northern waters (I). Shokubutsu oyobi Dobutsu, 10(10): 927932. (iu Japanese).
NAITO, Y., 1971. A report on Japanese sealing. Geiken Tsushin, 238: 49-52. 48-52. (in Japanese).
NAITO, Y., and M. NISHIWAKI, 1972a. The growth of two species of the harbour seal in theadjacent waters of Hokkaido. Sci. Rep. Whales Res. Inst., 24: 127-144.
NAITO, Y., and M. NISHIWAKI, 1972b. Ecology and morphology of Phoca vituline largha andPhoca kurilensis in the southern Sea of Okhotsk and north east of Hokkaido. Symposium on
the Biology of the Seal., University of Guelph, Ontario Canada.
TIKHOMIRov, E. A., 1971. Body growoth and development of reproductive organs of the North
Pacific Phocids. In: Pinnipeds of the North Pacific. (Israel program for scientific translations). Keter Press, Jerusalem, 213-241.

Sci. Rep. Whales Res. Inst.,
No. 28, 1976.