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ANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES
No. 4914
1•113.MRY ItiND OCE •
nIt5LIOrTistQUE• " „ •, Fuf oethISS pl.7.(1n'b
Report of an ecological survey of the Steller sea lion in Hokkaido
by T. Itoo, H. Katoh, K. Wada, K. Shimazaki, and K. Arai
Original Title: Hokkaido ni okeru todo no seitai chosa hohoku
From: Geiken tsushin, January (305/6): 1-18, 1977
Translated by the Translation Bureau Multilingual Services Division
Department of the Secretary of State of Canada
Department of Fisheries and Oceans Pacific Biological Station
Nanaimo, B.C.
1983
60 pages typescript
Year Année
Issue No. Numéro Volume
Jan 305/6 1977
DATE OF PUBLICATION DATE DE PUBLICATION
Page Numbers in original Numéros des pages dans
l'original
1 - 18
Publisher - Editeur
Japanese Whaling Society, Inc.
Place of Publication Lieu de publication
Etchujima 1-3-1, Koto ku, Tokyo, Japan
Number of typed pages Nombre de pages dactylographiées
60
1008910 Translation Bureau No.
DEC - 198?
Secretary Secrétariat of State d'État
MULTILINGUAL SERVICES DIVISION — DIVISION DES SERVICES MULTILINGUES
TRANSLATION BUREAU BUREAU DES TRADUCTIONS
LIBRARY IDENTIFICATION — FICHE SIGNALÉTIQUE
c rriti-s 4/1/-1 Translated from - Traduction de
Japanese Into - En
English
Author - Auteur Tetsuro ITOO, Hidehiro KATOH, Kazuo WADA, Kenji SHIMAZAKI and
Kazutoshi ARAI
Title in English or French - Titre anglais ou français
Report of an ecological survey of the Steller sea lion in Hokkaido
Title in foreign language (Transliterate foreign characters) Titre en langue étrangère (Transcrire en caractères romains)
Hokkaido ni okeru todo no seitai chosa hohoku
Reference in foreign language (Name of book or publication) in full, transliterate foreign characters. Référence en langue étrangère (Nom du livre ou publication), au complet, transcrire en caractères romains.
Geiken tsushin
Reference in English or French - Référence en anglais ou français
Whale research reports
Requesting Department Fisheries and Oceans Ministère-Client Notre dossier no
J. W. C. // Ps Translation (Initials)
Direction ou Division Traducteur (Initiales) Branch or Division Sci Info and Pub
Person requesting Dr M. Bigg Demandé par
Your Number Votre dossier no
Date of Request August 19, 1982 Date de la demande
SEC 5-111 (81/01)
TRANSLATION BUREAU BUREAUDESTRADUCTIONS
No. 305 January 1977
Id
.4„ Smetary Secrétariat of State d'État
MULTILINGUAL SERVICES DIVISION — DIVISION DES SERVICES MULTILINGUES
C l ients No.—No du client Department — Ministère Division/Branch — Division/Direction City — Vine
Scientific Information Fisheries and Oceans and Publications Ottawa
Bureau No.—No du bureau Language — Langue Tmmlator (Initials) — Traducteur (Initiales)
1008910 Japanese J.W.C. / ps DEC - 6 198e
WHALE RESEARCH REPORTS
Japanese Whaling Whale Research Tokyo, Kotoku, Society, Inc. Institute Etchujima 1 - 3 - 1
T 135 Tel Tokyo (642) 2888
pl Report of an ecological survey of the Steller sea lion
in Hokkaido1
. (I)
Tetsuro ITO°2, Hidehiro KATOH
3, Kazuo WADA
4, Kenji SHIMAZAKI
3
and Kazutoshi ARAI5 .
Fc:r
preheyi si ve_ 1. Part of a y study, "Biological research on the stocks of
Pinnipedia" partly funded by the Ministry of Education (Research representative Prof. Masaji NISHIKAWA, Ryukyu University).
2. Gifu Dental College
3. Northern Sea Fisheries Research Institute, Faculty of Fisheries, Hokkaido University.
4. Primate Research Institute, Kyoto University.
5. Faculty of Fisheries, Hokkaido University.
SEC 5-25 (Rev. 81/11)
Canacrâ
The objectives of the survey
Steller's sea lion, Eumetopias jubata (SCHREBER 1776) (1
2
Japanese
"todo") has long been known to occur in the Sea of Japan. In addition to
Allen (1880), Naumov (1933), Ognev (1935), Okada (1938), Matsuura (1943),
Ellermann and Morrison-Scott (1951), there can be mentioned the more recent
work of Nishiwaki (1972) and Geptner and Naumov (1976).
Nishiwaki and Nagasaki (1960), Nishiwaki (1965) and Nishiwaki
(1967) have given outlines of the migration, ecology and regional characteristicS
of the herds which visit Hokkaido.
Using specimens from various parts of Hokkaido, Itoo (1973) stated
that three sea areas could be distinguished in which the herds of visiting
sea lions were of differing age and sex compositions. However collections
were not made along the whole coast, so this study was both limited and
preliminary.
There are also studies made some twenty years ago of the damage
done by sea lions to the fishery, particularly by collecting the observations
of people engaged in coastal fishing, but there have been absolutely no
studies of sea lion ecology in Japan.
According to Nishiwaki (1967) and Itoo (1973) it could be considered
that the sea lions visited two sea areas, in north and south Hokkaido, with
contrasting characteristics. The objective of the survey was to clarify
many basic points about the ecology of the sea lions such as the seasons
at which they appear and disappear, their distribution,their haul-out areas,
the composition of the migrating herds, the size of the herds and their
feeding. Also included in the planning were studies of the growth, sexual
maturity, breeding, comparative morphology and parasites of captured specimens.
3
During the course of the survey many people gave us assistance.
We wish to express and record our gratitude to the following persons.
In the survey in Northern Hokkaido:-
Mr Shigeo OISHI (Rebun town, Funadomari)
Mr Yasuo OISHI (Rebun town, Funadomari)
Mr Hirota SAKANO (Rebun town, Funadomari)
Mr Binichi KURI (Rebun municipal offices)
Mr Jusuke OTSUKA (Rebun municipal offices)
Mr Takaji FUJIMOTO (Sarafutsu village, Hamaonishibetsu)
Mr Mitsutaka KURASHINA (Keio University)
In the survey in Southern Hokkaido:-
Mr Yoshietsu ARASHIDA (Usushiri Fisheries Experimental Station,
Faculty of Fisheries, Hokkaido University)
Mr Kiyoshi NOMURA (Usushiri Fisheries Experimental Station
Faculty of Fisheries, Hokkaido University)
and also all the hunters from Minamikayabe town, Birodomari, especially
Mr Ryoji KAMATA and everyone at the Northern Sea Fisheries Research
Institute of the Faculty of Fisheries of Hokkaido University.
The methods of the survey
The Northeill Hokkaido survey, which centre3around the north shore
of Rebun Island (Rebun town, Funadomari) was made in two periods, from
21 December 1975 to 13 January 1976 and from 27 February to 10 March 1976.
The Southern Hokkaido survey was made in the southwest part of Funka Bay
(Minamikayabe town) from 28 February 1976 to 22 March 1976. (Figure 1)
* Funka Bay is shown on many maps as Ushiura Bay. Translator.
ESR1FIA i* «REF N
. 4- HI MAS11111A REE F
,Z:31000 - ,tstANI
• CAPE e lIKO.T1111
FIINA »MAU BA y
Wt.% NA Ke.
AMIN MALI
lkm
FUNKA IA?
SR1RA SE
B IRQUIMA RI
ik.** UE11.11F1
13 6 ilokm
:17)
• • .•: •
T R
Figure 1
The survey areas and the places where sea lions were
captured. The * shows the places of capture, the
numbers in brackets shows the number captured.
•
Cooperation was obtained in both areas from the persons locally
concerned with sea lion destruction operations. In Northern Hokkaido six
trips were made with Mr Yasuo OISHI in his Kojumaru No. 5 - (1.5 tons) to
observe the number of individuals, the size composition and movements of
sea lions on the reefs and at sea. Following Scheffer (1967) and Allen
(1880) the measurements made on the eleven individuals captured included
the body length and thirteen other measurements and there were also
thirteen measurements of the size and weight of the internal organs,
including the gonads. The skulls and the whole skeletons were preserved
as dry specimens and the gonads, the exterior and interior parasites were
preserved as specimens hardened in 10% formalin.
The age was assessed principally from the annual ring structure
of the cementum layer and the dentine layer of No. 3 incisor in the upper
jaw10,45
. The stomach contents were investigated after hardening in
20% formalin.
Through the good offices of Mr Yasuo OISHI it was also possible
to obtain as specimens nineteen skulls captured before and after the survey
periods. The teeth and tusks of an individual captured in February 1976
were received from Mr Kiyoshi ARASHIDA, and these twenty individuals were
included as specimens for age determination.
Reference was made to the capture records (1973 to 1975) in the
Rebun town municipal offices to ascertain the numbers captured in recent
years. Sea lion hunters and others in the fisheries business were
interviewed about sea lion ecology.
6
Results and discussion
Because the number of specimens is extremely small, analyses
and discussions of the habits and movements of the sea lions, their exterior
morphology and of the data related to the weight of their interior organs,
gonads and skulls are omitted from the present report. Studies of the
exterior and interior parasites and information obtained about pinnipedia
other than sea lions are to be presented in separate reports.
1. Report of observations (Rebun)
Number of individuals on land
On trips with Mr OISHI and with local sea lion hunters, observations
were made of sea lions on land on Hirashima reef about 600 m north of Todo
Island, offshore from the northwest of Rebun Island, and the numbers were
counted with binoculars (Nikon 9x35).
The dates of observations and the numbers of individuals
were as follows:-
12 December 1975 30 - 40
28 December 1975 30 - 40
30 December 1975 71
2 January 1976 1
The reefs were assigned numbers by the authors (see Figure 2).
Observations were made on 30 December without being noticed by the sea lions
for about 15 minutes after 6.35 a.m. from the point on land marked "0" on
reef No. 4 (R - 4). The herds were resting on land and the largest total a L: a oiist- ance oF
number observed on the southern side of reef No. 2 s/ (R - 2 , local name
"uchinoshima" -"middle island") and on the southern side of reef No. 1, at .1
àieLarice. of go vyt
(R 1, "okinoshima" - "outer island") was 71.
•
7 •■■■
Hm
Figure 2
The Hirashima reefs on the north coast of Rebun Island.
(On 30 December 1975, 71 sea lions were observed on the shaded areas in the map)
R1 to R8 : The reef numbers (assigned by the authors)
0 : The observation point.
.detire,teenne›.-"".."«"""""•••
,
- --se::::•••;••
•
,
imate.,,reelle"e".›. ••• e.avé*.z:."Ys:.. • r-
Figure 3
The sea lion herd on land on the Taneshima reefs on the north coast of
Rebun Island. (Photographed by Mr Hirota SAKANO in the last third of
January 1973).
A: Part of the chain of reefs, 123 or more are on land.
B: Almost the whole of the chain of reefs, 288 or more are on land.
One tenth of the count was estimated to be missed because the
point of observation was low, about three to four metres above the sea
surface, and because all the individuals were sleeping or resting. It
was later ascertained from the tracks in the ice and snow that just the
same number of individuals were on land in the dead space on the north
side of the reefs. Thus, making something of a guess, the total number of
individuals was estimated to be about 150. None were swimming in the
nearby sea at the time of counting, and several individuals were seen on
land on the Taneshima reef about 3 km offshore which was visited about an
hour later. It was not known at either reef whether there were individuals
at sea and out of sight. There has not been sufficient study of the diurnal
activities of sea lions during the winter20
. However in this area there
are relatively large numbers on land, and according to the hunters, they
are not at this time to be found at sea.
The number of 150 is said in the interviews to be consistent with
the largest number on land in a normal year. The other three observations
were made from boats 50 m to 100 m away from the land sites, and the numbers
seen on land during eleven hunting trips from 18 December to 4 January was
70 to 80 on 20 December on Taneshima reef, so that the 71 on 30 December
is essentially the same.
Apart from our observations we received records from the same part
of the winter two years earlier which give information on the number on
land and which are presented here.
These are photographs of Taneshima which were taken during the
last third of January 1973 by Messrs. OISHI in company with Mr Hirota
SAKANO (three colour slides, 6 x 7). The number of sea lions on land was
9
counted by direct measurement of the film with a binocular microscope
(10 to 40 times). There are two films in which about four fifths of No.1
reef (local name "dohe")dere photographed from a short distance. In one
of them (Figure 3A), at least 123 were counted, and at least 129 in the
other. At least 288 were counted on Ule almost e.nire, Taneshima
reef photographed from a distance (Figure 3B).
The total number on land was estimated according to the following
assumptions. The proportion omitted in counting the film with 129+ was one
tenth. In the film with 288+ it was two tenths. (Discrimination between
individuals is more difficult in the photographs from a distance, and there
were many individuals which were asleep before the photograph was taken and
had not assumed the sea lion vigilance posture, with the head and the upper
half of the body held up to watch for dangerous objects).
To estimate the proportion of individuals in the dead spaces, it
was supposed that because of piling up on the reef the individuals in the
dead spaces of the film with 288+ would number one quarter of those counted.
The density on the back side of the reef was taken in both films to be the
same as that seen.
The densities on all reefs were taken to be the same as those found
in the film with 129+ and the film with 288
+ for reef No. 1, and the areas
of the other five reefs were found, neglecting reef No. 7 on which sea lions
were not believed to land. The area of reef No. 1 and the total areas of
reefs Nos. 1 to 6 were determined from an enlarged drawing (Figure 5) of
the air navigation chart (HO - 73 - 7Y, Rebun) and the ratio was taken as
the multiplier
+ 288 film: 288
+ x 2/10 x 5/4 x 2 = 864
+
+ 129 film: 129
+ x 11/10 x 2 x 90/36 = 709.5
+
10
These are extremely rough estimates, but if there is significance
in the near equality of the two numbers, there will be no great error in
thinking that the number on land on the whole of the Taneshima reefs on
that day was from 700 to 900. In conjunction with testimony from the
hunters that "there were none on land on the Hirashima reefs on that day
and no sea lions were seen swimming in the nearby sea" and that "so many
were seen on land only once in several years" one may think that in many
years the size of the herd wintering along the north coast of Rebun Island
is less than 1000. To estimate the total number visiting during the winter
would require data on the individuals arriving and leaving and this is not
possible in the present survey.
The individual composition of the herd
The size composition of the herd seen on 30 December was such that
large adult males accounted for at least 80%. One specimen, No. 75-K-6,
which was shot at the end of the period of observation, was estimated to
be 9 years old. There were some medium size individuals which were slim
from neck to shoulder (adult females or young males), and there were two bv, out,1-- bort lasE year.)
small individualewhose body length from the head to the stomach was about
half that of the adult males and were estimated to weigh about one tenth
the weight of an adult male. One of these small individuals was lying by
the water's edge ventrally touching a medium size individual, and from
their activities these two appeared to be mother and child.
On 25 December the sea lions were forced into the sea from the l or s■vo i‘uur.S
Hirashima reefs by shooting and were pursueefor trophies at sea with a
boat. Even when chased by the boat they did not immediately disperse but
11
continued to swim in groups of two to ten. It was possible to ascertain
the size composition during this by the relationship between the size of
the heads and upper half of the body which could be seen above the water
and the colour of the fur.
I) Adult males. Large size and thick neck. The profile from
forehead to snout is a concave curve, which is a noticeable
characteristic. Many are light brown but some are light grey.
II) Medium size individuals. Evidently smaller than I. The
neck is narrow and slim. When the upper part of the body is
seen out of the water this characteristic clearlydiscriminates
from I. They are believed to be almost all adult females but
may perhaps include young males. The fur is brown strongly
tinged with black.
III) Small individuals. Even smaller than II. The fur appears
jet black. They are probaby one to two years old.
Of these three, the proportion of I was overwhelmingly high, and
Of III extremely small.
From these observations on land and at sea, the composition of
the herd visiting the north shore of Rebun Island in the latter part of
December 1975 was over 80% adult males, about 10% medium size individuals,
and in addition a small number of individuals one to two years old.
This result probably confirms the herd composition in the Rishiri
and Rebun regions reported by Nishiwaki (1965) and Nishiwaki (1967).
12
2. Methods of capture and numbers captured in recent years
North coast of Rebun Island
Sea lions are hunted from December to the following May as a
joint enterprise of the Northern Rebun Island Funadomari Fisheries
Cooperative and the Funadomari branch of the Rebun town municipal office
(the budget for 1975 being 800.000 yen). Hunters with licences to
destroy noxious birds and animals are paid a bounty for each animal caught,
but do not use specially designed boats. There has been no destruction
in the south from Kafuka since 1974.
Sea lion destruction operations commence on the Taneshima and
Hirashima reefs when the sea lions arrive in November or December and
continue until they disappear from the area about April. The most prolific
season is late December to late January.
Sea lions are shot with rifles, and there are three methods of
hunting. These are "okauchi" (hill hunting), "mizuuchi" (water hunting)
and "funauchi" (boat hunting). In the "hill hunting" method the hunters
go stealthily ashore when the sea lions are on land and shoot at short
range. This is the most efficient method from December to January when
there are many sea lions on land. In the "water hunting" method sea lions
on land, on the reef or swimming in shallow water close to the shore are
shot from behind the rocks, and in the "boat hunting" method sea lions at
sea are chased into shallow water by small boats and are there cornered
and shot.
After February there are few sea lions ashore, and since the
transparency of the coastal water is lowered after the middle of the month
it becomes especially difficult to detect sea lions which have sunk after
13
being killed, so that the effectiveness of all methods is reduced. There
are no restrictions on the methods of hunting to be used, so that the
method used in each hunting trip is changed at will as may be expedient.
There is a very strong tendency on the north shore of Rebun Island
to hunt large individuals selectively. The reasons for this include "the
fact that the large ones make the easiest targets and have the greatest
weight of meat" for since Rebun is a remote island the seal meat has not
until recently been discarded but has been preserved as food. They also
include the hunters' eagerness "to get a large trophy". Consequently the
group of individuals taken does not correctly reflect the composition of
the natural herd and is almost restricted to the adult males (see below).
It is said that over a number of years the greatest damage was
done here by sea lions in 1972. According to the records of Funadomari
branch of the Rebun town municipal office, total numbers killed in 1973
to 1975, including the number captured and the number killed but not
recovered, are shown in Table 1.
The annual kill number can be seen to be practically constant at
50. If the size of the visiting herd is about 1000 as stated above for
late January 1973, the kill in 1973 was about 5%. Since the visiting herds
in 1974-1975 were certainly smaller than in 1973, the kill rate may be
taken to have been greater.
Of this total kill, 90% was due to Mr OISHI's hunting group.
The exact dates of capture in 1974 and 1975 were known from his diary.
These are shown by thirds of the month in Table 2. The individuals
captured were all males.
48
51
43
Period 1974-1975 1975-1976
December middle third 4 2
last third 5 5
Table 1
Recent scores in sea lion hunting operations in Rebun1
.
Hunting season Total number killed
February to April 1974
December 1974 to March 1975
December 1975 to February 1976
1. Rebun municipal office records
2. Total number captured or killed but not recovered.
Table 2
The number of sea lions taken in each third of a month
in recent years by the Rebun Island hunting group
Number captured
14
January first third 4 2
middle third 2 , 1
last third 11 • 10 .
February first third 2
middle third 4
Totals 26 26
15
Both years agree in that the peak in the number captured is found
in the last third of January. The probable reasons for this include the
land habits of the sea lions (see below), and the effect of the weather
conditions on hunting trips (trips in small boats, landing on the sea
lion reefs governed by sea conditions, especially wave height). This
peak in capture must also be strongly related to the peak in the
number visiting.
South-west shore of Funka Bay
According to an enquiry (1975, unpublished) concerning sea lions
made by the Northern Fisheries Research Station of the Faculty of Fisheriesm
Hokkaido University, six of the ten fishery cooperatives in the southern
part of Funka Bay have a policy of destroying sea lions.
About ten persons are licenced to destroy destructive birds and
animals in Birodomari, Minamiyakabe town, the survey area in the south of
Hokkaido. The sea lions begin to appear in November and December, and the
hunting season is from late December to the middle of May. The period of
most abundance is from early February to early March. There are no sea
lion haul-out places in the south-west part of Funka Bay and the hunt
always takes place at sea about 500 m offshore.
The number captured from December 1975 to March 1976 was 14, all
of them males, and in 1974 it was 20, including 2 females. In 1973,
about 70 were taken, including 3 females of which one was pregnant, the
others were males. Thus the most recent annual mean is about 40.
UNEDTD T
A :
16
3. The age and sex composition of the individuals captured
Eleven sea lions were captured during the period of the survey,
five at Rebun and six in Funka Bay. Figure 1 shows the places of capture werc
and Table 3 the external measurements. Twenty others ''captured in the
same areas before or after the survey period (nineteen at Rebun, one in
Funlça Bay were added), and the results ordetermining the ages of these
thirty one specimens, all of which were males, are shown in Table 4.
The 24 from Rebun Island are 24 of the 26 shown for 1975 in
Table 2 and were all captured during the main season (late December to late
January). All except one of the 7 captured in Kinka Bay were taken in the
latter half of the main season from late February to late March.
All those from Rebun Island were captured one or two at a time
to thin out the herd on the reefs, those from Funka Bay were captured at
random from the herds of one to several swimming offshore.
Turning to the age composition it is seen that at Rebun Island
88.5% were adult males five or more years old which had reached sexual
maturity38
and 54.5% of these adults were older individuals of nine years
or more (individuals reaching social maturity50
). Only 11.5% were immature,
and these three immature individuals (two-year olds), were small and were
captured when showing trust in the hunters. p6
In the proportion of adult males this age composition of sea lions
at Rebun Island is close to the results of visual observation by Itoo (1973)
which have already been mentioned and in which all fourteen were males of
These percentages are as given in the text, though I cannot make them agree with Table 4. Translator.
H) 0
5-1 4-t E
al 0 -4) A P. H 0
0
g-i
O. 00. -P -r-1
g-1 E • S-1 4-.) 4-1 Q. 0 g-1 0.0 0.0 CH 0 0
CIO 0.bO O bO 15 • IC 0 CO 15
4-40 0 0 4-. M CI-4
4-) 4-) -P 4-, 4-) (Q 4-) e O 0 W (fl R. 0 g-f g-1 • g-1
Ç34) Ç4
E 0
O M O E 0. m z
0.1 cn 8
ndy
leng
th Location of capture
South-west shore of Funka Bay
76-1 1976 2 28 8 : 00
76-2 1976 2 28 8 : 00
76-3 1976 3 3 9 : 00
76-4 1976 3 4 9 : 15
76-5 1976 3 14 8 : 15
76-6 1976 3 22 8:30
Yasuuchi offshore at.; 2 211 128 60 49 86
Yasuuchi offshore 3 222 142 60 53 96
Iwato offshore 5 265 166 83 63 113
Futami offshore 8 298 205 86 63 121
Birodomari offshore ,'» 3 223 147 76 53 101
Birodomari offshore 5 259 178 79 52 119
North shore of Rebun Island
75K5 1975 12 24 7 : 30 Taneshima inshore 5 262 — 86 60
75K6 1975 12 30 6 : 53 Hirashima reef 9 300 — 96 63.5
75K7 1975 12 30 7 : 15 Hirashima inshore 6 268 — 95 62.5
75K8 1976 1 .1 7 : 30 Hirashima reef 7 257 207 93 62
75K9 1976 1 4 7 : 30 Hirashima reef 15 286 223 102 66
Table 3
Measurements (in cm) of sea lions captured in Funka Bay and at Rebun Island
.•
,■■■
..1■1,
■1,
.1■1,
•■•
3
■.
3
3
2
2
4
1
2
2
1
1
Table 4
Age composition of sea lions captured in Funka Bay
and at Rebun Island
Age South-west shore North shore Funka Bay Rebun Island
Feb - Mar 1976 Dec 1975 - Feb 1976
2 1
3 2
4 1
5 2
6
7
8 1
9
10
12
13
15
17
Total 7 24
18
19
five years or more. However it differs with regard to the absence of medium
size individuals. Consequently it is biased towards old age as compared
with the age composition of the natural herd.
The Funka Bay specimens included four immature individuals of
four years or less and three adults of five years or more. Of the 23
included in Itoo's (1973) results for this area, one was an adult female,
the remainder being all males of which more than 70% were immature. Thus
females were extremely rare, and these results evidently agree with the
present results in the great excess of immature males over females. diverj en c_e_ be_weevi
The above account shows a s.e the seasons for collection are
limited, that there are questions about the methods of capture used at Rebun
Island, and that the number of specimens from Funka Bay is extremely small.
Comparison of the compositions of the separate herds of sea lions which
visit the two areas would be premature, but if the attempt must be made,
they are seen to agree on the rarity of females and to differ in that there
is a high proportion of adult males at Rebun , but a high proportion of
immature individuals in Funka Bay.
4. Survey of the stomach contents.
After the weight of the stomach contents had been measured they
were classified into fish skeleton specimens and cephalopod jaw and mouth
parts as was done by Hotta (1961), Matsubara (1955), Svetovidov (1948) and
Watenabe (1955). In order to compare the degree of digestion of the
stomach contents they were recorded on a digestion scale of 1 to 5, following
Wada (1971). In order to make comparisons of the weight ingested by each
individual, the weight of the stomach content was expressed as the
(Stomach content weight) x 10
5
(Body weight) 3 ■•■•. Index
stomach contents weight index
20
Feeding habits
The results of the analyses of the contents of the sea lion
stomachs are shown in Table 5.
Funka Bay
The stomach contents included the following four species
Smooth lumpsucker Aptocyclus ventricosus
Walleye pollock (bigeye) Theragra chalcogramma
Sculpins Gymnocanthus sp.
Giant octopus Paroctopus dofleini dofleini
Lumpsuckers were found in all individuals. The lumpsucker is known
to approach the coast to spawn from winter to spring, to be sluggish in AS
movements and to have ventral adhesive discs. The morphologies of the males
and of the females differ. In normal years, fishing in the southern Punks Bay starts in late January.
Where it was possible to measure the exterior morphology of the ()LÀkIcl_
lumpsuckers the average body length'was 27.00 cm and the average
weight was 1109 g. The females in the contents contained many eggs.
One bigeye was found. Digestion was advanced and only bones were
found but the lower gill cover bone of the bigeye is distinctive and
identification is easy. The length of the otolith found in the stomach
content was 20 mm which is taken to imply a body length of 380 to 420 mm
(Hokkaido Regional Fisheries Research Laboratory, 1973).
A-,
-p
weight in
dex
4-1 CO 0
Cll .0 -H E Z
Notes bD
0 3 D
iges
tion in
dex
Stomach
contents
Food species o
• 0 --- 0 E g-f -Poe
aica 0.0 W ES-1 • E • c 0 -p— m c (I)
1 20
many 5,840
1
21+
8,440
1
100.0
99.2
0.8
20.0
80.0
100.0
98.2
1.8
91.0
9.0
97.4
0.4
2.2
Stones (250, 7 g) Fish net
Stones(365,250) (160 g )
Stones(270,230 g)
Table 5
Stomach contents of sea lions captured in Funka Bay and at Rebun Island (1975 - 1976, winter)
76-1 4,770 50.8
76-2 8,670 79.2
76-3 5,450 29.3
76-4 21,340 80.6
76-5 13,080 117.9
76_6 22,790 131.2
75K5 21,180 117.8
75K6 Empty 0 75 1(7 5,860 30.4
751(8 8,440 49.1 75K9 T 0
Funaka Bay Smooth lumpsucker Giant octopus Smooth lumpsucker Sculpins
Walleye pollock (bigeye) Giant octopus Smooth lumpsucker Giant octopus Smooth lumpsucker Smooth lumpsucker Giant octopus Smooth lumpsucker Giant octopus
Rebun Island Atka mackerel Smooth lumpsucker Giant octopus
Atka mackerel Sand lance Sculpins
Smooth lumpsucker Giant octopus
(ilptocgc.lu4 ventnico4u4) (Panoctopu4 doe,Ceini doeteini) (AptocycLu4 ventn-Lco41/4) (§ymnocanthilA 4p.) (Thenagna chatcogmfmmz) (Panoctopu4 doeteini doelein£) (4/3-toceci_u4 ventnico4u4) (Panoctopu4 doeteinL doeteini) (Aptocecla4 ventnicoAaA) (Aptocec-CuA ventnicoAuA) (PanoctopuA doeieini doeteini) (Aptocyc2.114 vent7ico4u4) (Panoctopu4 doeCeini doeteimL)
(Pieuno9nammu4 4p.) (Aptocecitm ventn)coAuAl (Panoctopu4 de-Lei/1i deleiai)
(i-Ceunognammu4 Ap.) (AinmodeteA pen4onatuA) (Cottidae) (Aptocgc-LA ventnico4u4) (Panoctopu4 dofieiai deleini)
10+
4,770 2
2 T 5
18+
8,600 2
1 70 4
2 T 5
2 T 5
2 1,095 2
1 4,335 1
30+
21,340 2
16+
12,850 1
3 230 3
18 20,730 2
1 2,060 1
61+
20,640 2
1 80 3
1 460 3
Stone (880 g) 4 0.3
3 99.7
5
2-3 100.0 Stone (232 g) 5 - Stone (335 g)
Stomach content weight index = (Stomach content weight)
x 105
(Body weight) 3
Percentage by weight of each type of food, excluding stones, etc.
T: Trace
22
In late February to March the spawning season of the bigeye is
already over and they are moving offshore to search for food. This is
thought to be why the sea lion stomachs contained little bigeye.
One sculpin was found. This species lives throughout the year
in a zone close to the coast.
Five giant octopuses were found. Cephalopocb are rapidly digested
but the beaks, the eyeballs, and the soft shells (of squids) are often
found present as remnants in the stomach contents of normal pinnipeds.
Thus when pieces of flesh are found, it may be supposed that the time
elapsed since they were caught and eaten is relatively short.
Large quantities of giant octopus flesh were found in sea lion
specimens 76 - 3 and 76 - 6 and the shape of the arms could be distinguished.
In 76- 6 in particular the tentacles and head were complete, so obviously
the sea lion was captured immediately after catching and eating the octopus.
Apart from food, stones were obtained from 76 - 2, 76 - 5 and
76 - 6, and nylontex fish net was obtained from 76 - 2. The net was
believed to have been used to catch lumpsuckers.
The weights of the stomach contents of the six sea lions were from
4770 g (76 - 1) to 22790g (76 - 6). Expressing these as the stomach content
weight index shows the approximate trend of the quantity of food eaten
(ranging from 29.3 in 76 - 3 to 131.2 in 76 - 6). The degree of digestion
in 76 - 6 was low (1 to 2) so that the diminution of the weight of the
contents was relatively small.
These values may be considered as standards with which to estimate
the weight of food eaten by a sea lion.
23
None of the six was found to have an empty stomach. According
to Spalding (1964b) few empty stomachs appear among the sea lions of British
Columbia 1.5 hours after sunrise, but are most frequent after 17.5 hours.
The quantity of stomach contents is also greatest at 1.5 hours after sun-
rise, averaging 1750 cc, but smallest and practically 0 cc at 15.5 hours.
This must be considered to show that food catching activity is vigorously
undertaken from midnight to early morning.
It is not known whether or not the Funka Bay sea lions have a
similar diurnal feeding habit, and the conditiors of the survey in British
Columbia were quite different, but all the six individuals were taken
between 8 a.m. and 9.30 a.m. and this is thought to have affected the
reasons why no empty stomachs were found.
Rebun Island.
In contrast to the specimens from Funka Bay, the weights of the
stomach contents were small except for one individual (75 K 5) and two
individuals were empty. This is thought to be affected by the fact that
the sea lions were not taken at sea as they were in Funka Bay but on land
while resting (75 K 6, 75 K 8, 75 K 9).
The stomach contents included five species:-
Smooth lumpsucker Aptocyclus ventricosus
Atka mackerel Pleurogrammus sp.
Sand lance Ammodytes personatus
Sculpins Cottidae
Giant octopus Paroctopus dofleini dofleini
Bigeye bones were also found in vomit collected at the landing sites.
24
Lumpsuckers were found in two individuals, and nine with relatively
clear external morphology had an average length of 23.3 cm and weight
317 g. Compared with Funka Bay the weights were extremely light. This
may be thought to be due to the difference between the survey seasons
(two to three months) and to the fact that there were many males at Rebun P8
Island and the females had eggs which were not completely mature.
Atka mackerel were found in two individuals. Both Pleurogrammus
azonus and Pleurogrammus monopterygius occur in this area and their remains -
are difficult to distinguish in the stomach contents so they are recorded
as Pleurogrammus sp. 75 K 5 had caught at least 60, and their size was
found to be about 30 cm. The Pleurogrammus found in 75 K 7 had a
reconstructed length of 32.6 cm (from the tip of the skull to the caudal
fin bone).
Sand lances were found in one individual but the number was uncertain.
Sculpins were likewise found in one individual but the species
could not be determined.
Giant octopus were found in two individuals. In 75 K 5 there was
a large tentacle 67 cm long, in 75 K 9 only a beak was found.
The following deductions can be made from the stomach contents of
the eleven sea lions caught in Funka Bay and at Rebun Island.
The stomach contents of the sea lions were composed of fish and
cephalopods, predominantly lumpsuckers and octopus. Large quantities oflump- diA:4-re n c.e in
suckers were being eaten in both areas, with no effect due tcithe survey season.
This is thought to suggest that there is some relation between the
habits of the lumpsuckers and the sea lion migrations. The sea lion diet
tended to include items which were coastal, were spawning near the shore
or were bottom-dwelling.
Books
1) van Bree, P.J.H. 1976. On the correct Latin name of the
Indus susu (Cetacea, Platanistoidea). Bull. Zool. Mus.
Univ. Amsterdam, 5(17)1139-140.
2) Einarsson, S.T. and E. Jonsson. 1976. Nahveli blaupa Zi land
i nagrenni Reykjavikur. Natturufraedrngnrinn, 46(1-2)
22-24.
Perrin, W.F. J.M. Coe and J.R. Zweifel, 1976. Growth and
reproduction of the spotted porpoise, Stenella attenuata,
in the offshore eastern tropical Pacific. Fish. Bull.
74(2):229-269.
4) Perrin, W.F. 1976. First record of the melon-headed whale,
Peponocephala electra, in the eastern Pacific, with a
summary of world distribution. Fish. Bull. 74(2)1457-458.
5) Kenyon, K.W. 1977. Caribean Monk seal extinct. J. Mamm.
.58(1):97-98.
6) Brown, S.G. 1977. Twenty-eighth meeting of the International
Whaling Commission, 1976. Polar Records, 18(115):386-388.
7) Anonymo”s, 1977. Porpoises school mon in sonar technology.
Australian Fish. 36(2)26.
8) Anonymous, 1977.. Antarctic seal at home in Coffs Harbour.
Australian Fish. 36(2):27.
9) Anonymous; 1977. River dolphin protected. Fishini News
Inter. 16.(6):13.
* This list occurs here in the text and is consequently included though it appears not to be connected with the main article.
Translator.
25
3 )
26
WHALE RESEARCH REPORTS
No. 306 February 1977
Japanese Whaling Whale Research Tokyo, Kotoku Society, Inc. Institute Etchujima 1 - 3 - 1
T 135
Report of an ecological survey of the Steller sea lion
in Hokkaido (II)
Tetsuro ITOO, Hidehiro KATOH, Kazuo WADA, Kenji SHIRAZAKI
and Kazutoshi ARAI.
5. Survey of interviews (Rebun)
Introduction
As is true of all pinnipeds living in Hokkaido, there have been
no studies of the ecology of sea lions in this region, and sea lions are
extremely difficult animals for researchers to collect.
The hunters have obtained knowledge of how to obtain their
catches by means which differ from those of the researchers, but there is
no doubt that this is just the knowledge which must be accumulated in
order to make any catch.
In this survey of interviews we have endeavoured to deduce the
ecologically distinctive characteristics, particularly the regional
characteristics, of the animal in question from the knowledge which has
;
TR
e - z t%1
27
historically been accumulated. At the present stage of our studies it is
even essential to acquire such preliminary but complementary knowledge.
It was felt that in the present state of study of pinnipeds in
Japan the interviews obtained during the past years form something which
could not be omitted from the survey, and it was decided to record an
outline of the content of these interviews.
In keeping with the character of this report, all matters concerning
the movements and mode of life of individuals have been omitted.
The following persons were interviewed during the survey. We are
deeply grateful to each of them for this cooperation.
Mr Shigeo OISHI (Rebun town Funadomari, fisherman, sea lion yasuo oist-ii ( Same, Sanla, born 1944 ),
hunter, born 1918)‘,"Mr Hirota SAKANO (Rebun town Funadomari, iron works
manager, born 1918), Mr Yoichiro SAITO (Rebun town Funadomari, former sea
lion hunter. born 1901),Mr Tomiyoshi SASAKI (Rebun town Nishiuedomari,
fisherman, born 1901), Mr Setaro SETOGAWA (Rebun town Funadomari, fisherman,
sea lion hunter, born 1911), Mr Yukio SAKANO (Rebun town, former head of
the town council), Mr Jingoro KAMATA (Rebun town, Kafukafunbe, fisherman,
sea lion hunter, born 1919), Mr Takaji FUJIMOTO (Soya county, Sarafutsu
village, Onishibetsu, fisherman, born 1935).
Coastal Ecology
The inshore migration route
The migration route of the sea lions which appear annually on the
north shore of Rebun Island from the end of November to the beginning of
December and leave at the end of April is thought "to follow the increase
and decrease of the drift ice on the shores of the Kurile Island and
Okhotsk Sea, making a round trip between those areas and Rebun Island"
1113 ite do Mara:
■2;kix.r4k i
AJove* bt,e N
1)ectow4f./1_
liEnceeet. . DNI
etedffli
ki&e.45,4,
re_edr)4 .:1•-•
i5af.4kr.: 14- , igice .•\1•3- ,„\,
ic.fitke L414 Mel‘i
Ci.ne 13e,i. ■ *
&to. of 7Ixéc,,,
0 10ko:
Figure 4
Distribution and migration of sea lions in winter and spring
on the shores of Rishiri and Rebun
Dotted areas : Areas in which sea lion herds are frequently observed
H : Haul-out places
DH : Abandoned haul-out places
H1 : Taneshima reef
H2 : Hirashima reef
H3 : Neko rocks
DH1 ; Todo (Sea lion) Island
DH2 : Tataki Island
DH3 : Cape Gorota
DH4 : Bukkoda (the name of a coask)
Arrows : Directions of migration
28
F.1
29
and there is no known connection between Rebun Island and more southerly
parts of Hokkaido.
Concerning the route by which the herd goes north, it was observed
50 to 60 years ago that "the herd which departed from the Taneshima reef
off Rebun Island went by way of Moneron Island offshore from south-west
Sakhalin (former Japanese Todo Island, 46°15'N, 141 °15'E, about 90 km off
Cape Sukoton, the northern tip of Rebun Island)".
It is also said that "sea lions which now cross annually at the
beginning of May from the south shore of Rebun Island to the north shore
of Rishiri Island congregate in an area two to three miles offshore from
Cape Fuji to Oshidomari, where they form a large herd and depart northward".
These two stories are of course conjectures but they probably indicate
the ends of the migratory routes (Figure 4).
Seasonal abundance and disappearance in coastal areas
Firstly we discuss conditions from Cape Sukoton to Taneshima reef
(Figure 4 and Table 6). As already stated, "the season of arrival is late
November to early December. The season of abundance is late December to
late January, when almost all are adult males with a few adult females
and young. At this season they haul out on the Taneshima and Hirashima
reefs. In a normal year the maximum number on land is about 150". The
total visiting number is thought to be greater than the number on land,
but no estimate has been made.
"There are no sea lions hauled out after February and the number
seen at sea near the haul-out reefs diminishes". Causes for this are the y
known dispersals to neighbouring areas aneMigration to Rishiri Island,
Now Now
December
February
Late May
October
April to May
June
0 0
Off North coast Vicinity of of Rishiri Island Todo Island reef
1 1
February to March
0
October to May
0
Yes Yes
Table 6
Comparison of sea lion ecologies on the shores of Hokkaido
Locality North shore Rebun Island
South shore Rebun Island
Hamaonishibetsu coast
Period
Time of arrival
Time of most abundance
Time of disappearance
Number of summer residents and composition
Number of haul-out places
Haul-out period
Number of rookeries
Assembly areas before going north
Damage to useful fish or fishing gear
50 years ago
(present all year)
May
(2/3 disappear in May)
1/3 of winter number,mainly young animals
more than 6
October to May
1
Vicinity of Taneshima reef
No
Now
Late November to early December
Late December to late January
Late April
0
2
December to January
0
None
Yes
31
but it is thought that an immediate cause is the sea lion hunting,
particularly the "okauchi" (hunting from behind the rocks), which is
continuous from the first arrival.
"The composition of an individual herd gradually changes from
February to April, and the proportion of females and young increases. In
April the number of young individuals increases to more than in February
and March but at the end of April almost all disappear and it is rare to
see a young one in May".
It was found that the ecology of the sea lions forty to fifty
years ago differed from the present ecology in the following ways (Table 6).
"At that time they hauled out during the period of most intense
cold in January and February, and the number hauled out did not diminish
at the beginning of February as it does now. The season with the greatest
number hauled out was when the sea lions began to gather together on
Taneshima reef in May before going north, and the season of abundance was
not in December or January as it now is". As mentioned above, at present
the area for gathering together is probably on the north coast of Rishiri.
"Nowadays they disappear at the end of April, but at that time
small and medium sized individuals to a number of about one third of those
present in the winter remained in this area during the summer after the
herd had left for the north".
On the coastal area of the southern end of Rebun Island, "they
arrive in December, the number of individuals is greatest in February, and
the herd then contains several tens. At the end of May herds of 30 to 40
each are formed and move over to the north shore of Rishiri, and in June
they become extremely rare, only one or two being seen".
32
The distribution along the coast
It is thought that "the place where the sea lions first arrive
is, without exception, the Taneshima reef, and from there they disperse
to other coast lines among the islands" (Figure 4).
"The visiting season lasts from December to the end of April
and the distribution density is greater on the west coast of Rebun Island
than on the east coast, but the areas in which the sea lions are often
observed in a herding situation are restricted. The places in which there
are many sea lions are, in order,
1) The area extending from Taneshima and Hirashima reefs to Todo
Island and as far as Cape Sukoton (called, below, the NW area). In this
area there are from several tens to a hundred and several tens.
2) In the area on the south coast of Rebun Island offshore from the
Neko coast extending from Chiyuka to Cape Karannai (the S area) there are
from around ten to several tens of individuals.
3) In the NE area off Cape Kanedano in the north east of Rebun
Island there are from several to several tens of individuals.
In addition herds of a few to several tens of individuals are
found in the neighbourhood of the two capes at Nishiuedomari on the west
coast and on the reefs by the gathering places on the north east coast
of Kafuka".
It is believed that these herds are all "gathered together while pll
resting". Concerning the feeding areas "large herds appear in December
to January in a six mile area off the west coast from Uennai to Motochi
and in a three to four mile area of Cape Uedomari on the east coast, which
are the fishing areas for Atka mackerel (Pleurogrammus) and bigeye (Theragra)"
Figure 4.
33
From these conditions of distribution, it is thought that "the
centre of the distribution of sea lions on the coast of Rebun Island is
the NW area, which has haul-out places and storm-time refuge places (see
below), and small migrations from there are repeatedly made to the feeding
areas". There are small scale haul -out places in the S and NE areas
and it is thought that "houses are rare at the ends of the capes and under
the cliffs and the sea lions can evade disturbance by humans or by fishing
boats and rest for a while" but "the NW area provides sufficient haul-out
and rest places". In addition, at Cape Gorota, Cape Sukoton, the Amanna
beach north of Utomai and other places of similar beach topography "there
are often several sea lions sleeping or resting at sea, especially in the
early morning" and hunters from coasts other than the NW area where there
are no haul-out places have always caught these sea lions by "mizuuchi"
(hunting from boats).
It is also said that "herds at the gathering places will come
to eat fish thrown overboard from fishing boats returning to the port
of Kafuka".
The haul-out reefs and their characteristics
The Taneshima reefs consist of seven reefs lying directly north
to south, all of them narrow and extending from south west to north east
(Figure 5). The first and northernmost reef (R-1, local name "Dohe") is
the largest (about 90 m by 30 m). The island about 60 m north of Reef
No. 1 (Okinoshima) is for some unknown reason not included in Taneshima.
"Among these, the favourite haul-out places for sea lions are
Reef No. 1 and Reef No. 2 (R-2, "Nagashima"). The north east of the former
o
34
1- o
Figure 5
The principal sea lion haul-out places on the Taneshima reefs,
(A and B) and the rookery about 50 years ago (A).
R1 to R7 are the reef numbers (authors' nomenclature).
ï
0 54
Figure 6
The principal sea lion haul-out places on the Hirashima reefs, (A and B)
R1 to R8 are the reef numbers
For C and D see the text.
35
is high and the south west is low. The centre of the south west part is
concave. In contrast the north east part of R-2 is low. The sea lions
prefer to haul out on the concave part of R-1, their next preference being
the north-east of R-2. (Points A and B in Figure 5). When there are
many sea lions those which,do not manage to haul out on these two reefs
haul out on the other reefs Nos. 4 and 5. (The haul-out conditions in
Figure 3 form an example of this).
"In March and April of a normal year, there may exceptionally be
a few hauled out on No. 4 only".
The Hirashima reefs consist of eight reefs in an almost circular
cluster about 150 m north to south and about 130 m east to west, located
about 600 m to the north of the centre of a bay on the north shore of
Todo Island. "Of these, those on which the sea lions haul out are mostly
restricted to reef No. 1 (Okinoshima, R-1) and reef No. 2 (Nakanoshima, R-2).
Both of these are about 40 m east to west and 30 m or 20 m north to south.
.(Figure 6).
"Like reef No. 1 at Taneshima, the western half of reef No. 1 here
is concave and the sea lions like to haul out there (point A). When there
are many individuals they haul out on the high part (about 3 m) on the
eastern side. On reef No. 2 point B to the east is normally used. Reef
No. 4 is used only when Nos. 1 and 2 are covered with individuals already
hauled-out".
"In March to April one or two individuals haul out at point C on
reef No. 8. Point D was used for hauling out in the winter several year
ago but recently it has not been used".
Moreover, for unknown reasons "For about 5 years from 10 years
ago to 5 years ago, no sea lions hauled out on any of the Hirashima reefs".
36
These "ways in which the haul-out places are chosen have not
changed on the Taneshima and Hirashima reefs from 50 years ago" and the
surfaces of the rocks in the haul-but areas of the reefs much used by
the sea lions are smooth (authors' observation). The reason for the
constant use of the same areas is thought to be that they satisfy the
following requirements - - "a distinct topography providing places from
which the approach of men or boats can easily be seen, deep water next to
the rocks so that the sea lions can dive in their preferred response to
an emergency, and shelter from wind and waves".
The centre of distribution of sea lions on the shores of Rebun
Island is considered to be in the NW area from Taneshima Reefs to Cape
Sukoton. An important condition for this is probably that in addition
to containing the two haul-out reefs "the topography of the coast of Todo
Island within easy reach from the Hirashima reefs has the shape of a
letter H with the lower right tip missing, and provides locations which
are excellently protected, not only from the prevailing north west wind
but from severe waves from all directions".
Another haul-out place is the Neko beach near the south west tip
of Rebun Island (about 4 km south of Motochi). It was often observed that
"sea lions have hauled-out here since about 1975 and in the same months of
the following year, February to March 1976, there have continually been
from 4 - 5 to 10 sea lions hauled out there".
On the eastern shore "there are occasional haul-outs on the shore
of Kitousu" but it is not certain that these haul-outs are to be confirmed
(it is believed that sea lions will occasionally haul out here_ ancLUier in (-21e.
37
early morning and at times when fishing boats are not around on shores
away from habitation).
Further it is said that "independent individuals may haul out
at quite unusual places, but they are usually wounded or ill".
"There used to be normal haul-out areas on the west shore of
Todo Island and on Tataki Island (a reef about 150 m south west of Todo
Island)" but they are not used at present. According to Mr SAITO who lives
on Cape Sukoton the sea lions he caught "were almost all taken on Tataki
Island (Figure 4, DH2) and hunting trips were rarely made to Hirashima and
Taneshima reefs as they are now". (According to tradition, the origin of
the name Tataki was "the name given by the Japanese who saw the Ainu hitting
(Japanese "tataki") seals and sea lions with clubs).
Also "large numbers of sea lions climbed up the steep slopes to
haul out on the large reef at the end of Cape Gorota" according to
observations made about 60 years ago, and there is evidence that the sand
beach in the centre of Hamanaka Bay (local name Bukkoda) was the scene of
special sea lion hunts with nets in 1914 to 1915 so one may suppose that
this point was a haul-out area. However sea lions rarely haul out on
that beach nowadays.
Former breeding records
It was generally agreed between fishermen and hunters in Rebun
town, Hamanaka, that sea lions used to give birth on Taneshima reefs. The
"History of Rebun" (1972) states that according to data obtained by the
Agriculture Development Faculty of the University of Tokyo in 1963 "sea
lions were giving birth to pups (p 42), but the date is not recorded.
38
Interviews with old-time hunters and other observers convinced us of the
actuality of breeding up to 1926.
It is believed that there are no existing reports of sea lion
rookeries on the shores of the Sea of Japan, so the contents of the
interviews are reported here with slight abridgements.
I. Mr Tomiyoshi SASAKI's stories
First story
About 20 May 1923, Mr Sasaki, then 18 years old, accompanied his
father and elder brother to fish with nets for lumpsuckers in the sea near
the Taneshima reefs. Sea lion parents and pups were found on the SW part
of reef No. 1 (Figure 5, point A). There was a "makabu" (a name used for
a particularly large adult male, now obsolete) with a length from nose
tip to edge of rear flipper of 1 go 2 - 2 shaku (364 to 394 cm), six or
seven adult females, 8 to 9 shaku (242 - 273 cm) and six pups, 3 to 4 shaku
(91 - 121 cm). Five of the pups were held in the mothers' flippers as they
escaped to sea, the remaining pup fell between the rocks and was captured
by the Sasaki party. This pup was rather smaller than the others with a
body length of about 1 m, its fur had regions of a more reddish colour,
and it had an umbilical cord about 2 to 3 sun (5.1 to 7.6 cm) long. On
the homeward journey the mother chased the boat, (which had two pairs of
oars) and bit repeatedly at the oars which were of evergreen oak. By the Eue. cajeS cq. 211.
time Todo Island was reached veight oars had been c..11eweci away. The
captured pup was fed for about 50 days but it was eventually eaten.
Second story
In the summers of 1915 and 1916 mother sea lions and pups were
seen playing together just as dog puppies play on land on the reef
furthest offshore of the small chain of reefs stretching NNE from Cape p13
39
Sukoton (Manju rock). The mothers swam around in the vicinity and did
not attack. At that time such la- born pups were called unibankon
(second pups).
Third story
In the latter part of July 1920 or 1921 five or six sea lions
were observed to be accompanied by pups in the sea close to Todo Island.
One of them was swimming with the pup riding on its back.
II. Mr Yoichiro TSUSHIMA's story
Mr Tsushima, a fisherman who was born in 1897 and who died in
1963 told the following story about 1953 to Mr Yukio SAKANO.
While harvesting funori (glue-plant, Gloiopeltis furcata) one
densely foggy morning in May, Mr Tsushima who was then in his teens went
on a pleasure trip in a small rowing boat with a fishing crew of three
young people about 30 or 40 minutes from Todo Island towards Taneshima
reefs to catch sea lion pups. Because of the thick fog they lost their
way and were not able to get to Taneshima. They wandered around all day
at sea, and finally just managed to arrive late at night at Awabikotan
(on the north west coast of Rebun Island) and were able to take refuge in
a house.
This is the story of a failure but it can be taken at least to
show that at that time many trips were made to capture sea lion pups
which were normally easy to capture.
III. Mr Yoichiro SAITO's story
After 1921 Mr Saito fished for herring and kelp at Cape Sukoton
and Todo Island and also incidentally killed sea lions. (When he stopped
hunting sea lions in 1945 his total kill was about 70).
40
When he wasa child in the latter part of the Meiji era and during
the Taisho era (i.e roughly the first quarter of the present century), sea
lions gave birth on Taneshima reefs, but no breeding activity has been
seen since 1928. Births were practically restricted to the hollow places
on the south west of the northernmost reef No. 1 (point A, Figure 5), and ree Fs or ori
there were no births onvHirashima Island, Todo Island or Tataki Island.
He thinks that the birth season was May to June, but fishing was
very busy after the middle of May and he is not certain.
The largest number of pups observed was about ten. The migrant
labourers who came from inland ("nishin no wakamono" - the herring laddies")
would frequently go out to catch a pup which would be 2 shaku 5 sun to
3 shaku long (73 to 91 cm) and would amuse themselves by making it swim
around while tied to a rope.
Around the time directly before the sea lions gathered together
on Taneshima began to go north thirty to forty would be resting hcre. avlcl
ol the shoals and reefs, and they included the extremely large adult males 1K viorma/ years,
which were called "makabu". v hese makabu did not appear until the time Lc) L7c1i
for going north, and vto one tried.' them (they were 1 jo 3 - 5 shaku (394
to 455 cm) long and their flesh is said not to have been eaten because it
had a very offensive odour). The makabu were often observed to fight among
themselves, leaping violently out of the sea and biting at the upper parts
of their bodies. Blood would frequently flow from necks and shoulders and
many new and old scars were often found in those parts. At haul-out time
the makabu would take up positions on the highest rocks and would normally
keep their heads up even when the other sea lions were sleeping. When
humans approached they were the last to rush away.
41
In the Meiji and Taisho eras (i.e. before about 1926) the
individuals hauled out on land did not rush headlong into the sea at one
gunshot, as they do now, and even after two or three gunshots most of
them remained asleep. However one reason for not giving birth on
Taneshima was the disturbance produced by the annual capture of pups.
At that time part of the herd which had left Taneshima for the
north hauled out at Moneron Island (also called Todo Island, i.e. Sea in Sakkalin
Lion Island) vand it was once observed that a large number of sea lions
were born there.
A study of the content of these stories
1) The season when breeding occurred
Verifiable memory of observations of pups on Taneshima dates
only from 1923, but however one regards the evidence of Mr SAITO, the best
informed of the three informants, there can be no doubt that breeding
regularly occurred from about 1910 to about 1928. No pups have been seen
since 1933 - 1934 when Mr SETOGAWA began hunting, and it may be supposed
that breeding had stopped about the beginning of the Showa era (1926).
2) The season of birth
The occurrence of birth in mid May to June agrees with reports
on the birth season in.America and Canada3
'24
'39
'42
and on the birth
season in the Kurile Islands4. It is very likely that the births on
lake.
Manju Island were exceptionally births in an exceptional locality in that area.
3) The place of birth
Among the several haul-out places of the period, the place of birth
was restricted to reef No. 1 at Taneshima, which is very interesting because
42
it is the place most used by sea lions both then and now. One may suppose
that the conditions required of a birth place are more numerous than those
required of a haul-out place.
4) The size of the breeding herd
All informants agree that the size of the breeding herd was
extremely small. Examples of breeding in such small herds are not other-
wise known4,39
, and this is thought to be very unusual. The harem
structure (6 to 7 cows to one bull) agrees with the ratio already reported39,47
.
5) The size of the new-born pups
The sizes given in the stories are all estimates and memories
of estimates so they may not be of great significance even though they
agree with known data (89 - 122 cm, average 100 cm23,24,42,45).
In this
region in particular it is customary to express the length of adults as
from the tip of the nose to the end of the rear flipper, so the estimates
for pups may be too small.
6) Parent-child relations
There are no existing reports of actions such as the cows holding
pups by the front flippers when escaping, a cow robbed of her pup chasing
and attacking the boat and a pup riding on the back of a swimming cow, but
they could be anticipated from the actions of other pinnipeds.
7) The reason for abandoning breeding
According to the History of Rebun (1972) advances in motive
power of the boats (p 522) at the beginning of the Showa era (the middle
1920's) caused changes in the character of the herring fishery during the
main fishing season (p 444), but this is not believed to be directly
p14
43
related to the abandonment of the rookeries. Mr SAITO's suggestion "there
was no breeding because of the disturbance produced by hordes of people"
may be appropriate. Even at the present time the haul-out place is
disturbed by hunting every day of fine weather after December, and in the
past there were probably similar occurrences when, according to the story
on page 31 (page 10 of the Japanese text) the sea lions used to haul out
and gather together on the reefs in February.
8) The bio-geographical situation of the rookery
Apart from the observation by Mr SAITO there is an observation
made by Mr Jingoro KAMATA's father about breeding on Moneron Island in
Sakhalin "there were so many sea lions that there was nowhere left to
set foot on the shore. The sea lion pups had no fear of man". This suggests
that Moneron Island was a fâilrly large scale rookery.
Metaphorically, one might wonder whether Taneshima may have been
a "branch store" of this Moneron rookery.
Voronev (1974) has reported the occurrence of sea lions on Moneron
Island, but breeding there is not believed to have been previously reported.
Bobrinskii (1944) reported a sea lion rookery at Vladivostok but
this is not a very recent report, and since Geptner and Naumov (1976) do
not mention it, the report may not be accurate.
Thè'southérnmost rookery at present known in the Okhotsk Sea and
the Kurile Islands is that reported on the southern tip of Etorofu Island
by MIYATAKE (1943). Recently, according to Belkin (1966) and Perlov (1970)
this is a haul-out place for young adults and the southernmost rookery is
the south of Chirihoi Island (Brat Chirpoev).
44
Thus there are places which have been lost, but the first rookery
known to have existed on the shore of the Sea of Japan was at Taneshima
reef. This would make it interesting to know whether there is still a
rookery on Moneron Island.
6. A preliminary survey at Hamaonishibetsu, Soya county
Hamaonishibetsu in Sarafutsu village is not far from either Rebun
or Rishiri Islands and is visited by many sea lions during the winter.
Moreover there is a sea lion haul-out reef (Todo Island, or Sea Lion Island)
only 1.5 km from the main island, and this is expected to present a
favourable location for ecological studies of sea lions.
A comprehensive study of the ecology of sea lions will probably
require knowledge of the migrations which link the rookeries in Soviet
territory to Hokkaido and also the movements between the haul-out places
and the assembly places and their utilization throughout Hokkaido.
With this in mind a preliminary survey was made on 9 and 10 March
1976 of the present conditions at Hamaonishibetsu where the circumstances
mentioned above are present.
Results of the investigation
Through the courtesy of Mr Takaji FUJIMOTO, we went out in a small
boat to observe the sea lions on Todo Island, and observations of the total
number were made for about 30 minutes on the morning of 10 March, starting
at 6.20 a.m.
Todo Island is formed of two reefs of almost equal area. A
maximum of 86 was counted on the south west sides of the two reefs (the
Hokkaido side). In addition, 101 could be counted on a slide-film photo-
graph taken by our companion Mr Mitsutake KURASHINA.
45
An estimate based on the topography of the reefs and the situation
of the sea lions on land suggested that the total number hauled out was
1.5 times as many (130 to 150).
The size structure of the individuals on land was taken from the
same film by Mr KURASHINA and divided into the standard sizes previously
used, large individuals, medium individuals and small individuals, with
the results shown in Table 7.
• About one half were large, one quarter medium and there were only
a few small individuals.
More individuals were seen at sea than were hauled out on the
reefs and there were more medium and small individuals than large individuals.
In contrast with the structure described above on the North shore
of Rebun Island in late December, it was thought that medium and small
individuals were more common than large individuals in both the hauled-out
and swimming herds.
Stories
Mr FUJIMOTO told us the following stories about the ecology of
sea lions at Hamaonishibetsu.
"Sea lions appear every year in this area in October, and haul
out on Todo Island from November. The number of individuals is greatest
from April to May (about 500). The maximum number hauled out is of the p15
order of 150, and this is composed of large individuals. There is no room
for small individuals and they gather together at sea".
"The season during which they stay is from October to May. During
this time there is no change in size structure, with medium and small
being 20% to 30% of the large size".
Table 7
The number and size structure of sea lions found hauled out
on the reefs (Todo Island) at Hamaonishibetsu, Soya county 1.
Ree2
Large3
Medium4
Small5
f
Unknown Total name size size size size
Reef No. 1 32 18 3 12 65
(19.2) (27.7) (4.6) (18.5) (100)
Reef No. 2 19 9 1 7 36
(52.8) (25.0) (2.8) (19.4) (100)
Totals 51 27 4 19 101
(50.5) (26.7) (4.0) (18.1) (100)
1: 10 March 1976
2: Authors' nomenclature
3: Adult males
4: Adult females and young males
5: One year olds
( ) Percentages
46
. 47
"They start to go north in May and in June they have disappeared.
(Table 6).
"No sea lions can be seen when drift ice covers all the sea and
touches the shore, but when the drift ice moves away they are to be seen
immediately. Abnormally, the drift ice did not touch the shore even once
from the end of 1975 to 10 March 1976".
About 25 km from Hamaonishibetsu "they may haul out on Benten
Island on the south side of Cape Soya during rough weather when they cannot
haul out on Todo Island. There are no haul out places on shore to the
south east in the direction of Esashi. It is thought that the Nijo shore
(45o47'N, 142
o14'E) on Soviet territory, about 48 km NNW of Hamaonishibetsu
is used as a main haul-out place from Todo Island".
"Sea lions damage nets set for salmon. Five years ago Mr Koichi
SHIBUTA (Mombetsu) hunted sea lions at the request of the local fisheries
cooperative. During the year he killed about 100".
General discussion
This survey was on a very small scale (about 1.515 million yen)
but it will no doubt be valuable as the first study officially initiated
of Japanese pinnipeds, which, except for a survey of the fur seals made
long ago on the basis of an international treaty, have been completely
neglected.
All over the world studies of sea lions in winter have lagged far
behind summer (breeding season) studies20,44
48
Sea lion migrations are known in the following areas -
Central California3,6,7,11,36
, Oregon22
, the Aleutian archipelago and the
east coast of the Bering Sea20
, and the Commander Islands2
'12
However the characteristics of the migration depend on the area
and do not agree with the Hokkaido pattern of arrival in October to
December and departure in April to May. If one looks carefully for some
point of seasonal agreement, it may perhaps be found in the movement
between Kamchatka and the Commander Islands of the herd which contains
the main body of the young males. This herd is to be found in the
Commander Islands in winter from October to March and disappears in April.
Or there is the herd of adult males and half grown males with no females
which goes north in summer and migrates south to the Aleutian Archipelago
in late autumn just as the ice arrives.
These studies of sea lion migration in foreign countries are in
general made by observation of the increases and decreases of the numbers
in rookeries and haul-out areas and of the directions of swimming and
migration at sea, and surveys of specimens taken from specified areas
during the winter are completely lacking.
Consequently nothing now exists which can be directly compared
with the very modest data concerning the ecology of the wintering herd
which we obtained in our survey.
There were differences in the amount of effort we expended on
interviews on the north and south coasts of Rebun Island and at Hamaonishibetsu,
and we cannot say that it was enough for the two latter places, but we wish
to mention some pointswhich we think should be subjects for later studies.
49
1) The date of arrival at Hamaonishibetsu is about one month earlier ((.5thoi, r)
than on the north and south shores of Rebun Island, and the date of
departure is about one month later (May to June), and they are the same
at Rebun south shore, Rishiri south shore and formerly (40 to 50 years ago)
at Rebun north shore. The former main season at Rebun north shore (May)
was the same April to May, but now it is greatly different on the north
shore (December to January) and on the south shore (February). It is a
very interesting point that the present season at Hamaonishibetsu is very
similar to the former season on the Rebun north shore, except that none
remain after June (Table 6).
The geographical and temporal variations of the times of
appearance, prevalence and disappearance and the simultaneous changes in
the herd assembly and the migration routes are phenomena connected to the
increase and decrease of rookeries and haul-out places. One may suppose
that in order to understand the changes in sea lion ecology on the coastal
areas of Hokkaido it will be necessary to analyse the long period climatic
changes and the related changes in the animals used for food, and also the
increases in fishing activities (especially in winter) which have occurred
for at least twenty and perhaps up to fifty years.
2) While the sea lions remain at Rebun Island (December to April) they
haul out on the reefs in the north but are believed to tour all the
coastal areas (from Taneshima reef to Soya Island is about 26 km) and at
the end of May they are said to cross the Rebun strait (about 10 km) to
the north coast of Rishiri Island. At Hamaonishibetsu they are known to
respond to the state of the sea by moving to Cape Soya (about 25 km) and
to the Nijo coast in Soviet territorg (about 48 km).
p16 p16
50
Taking these movements into consideration, it may be conjectured
that there will be movement to and from Rebun and Rishiri Islands to Cape
Noshappu and Cape Soya, in the direction of Todo Island at Hamaonishibetsu
and even further to Yagishiri and Teuri Islands (about 75 km from Rishiri
Island) and to the Soviet Moneron Island (about 90 km from Taneshima reef).
Consequently elucidation of the ecology of sea lions in the
Hokkaido area will require a survey throughout a wide area from Mombetsu
to Cape Soya to Rumoi to determine the movements of sea lions inside this area.
Next we wish to say a word about the character of the present survey.
In both north and south Hokkaido the survey was completely dependent
on the sea lion destruction business (the restricted sea lion hunting by
means of small boats or beach boats). These are suitable if the objective
is a sea lion hunt but even if there is an opportunity to ride with them
satisfactory time for observation and counting cannot be guaranteed.
Moreover, since sea lion hunting combines aspects of recreational fishing,
recreational hunting and net profit, it is suspended as soon as the
numbers hauled out or coming to the local hunting area decrease, and there
is no possibility of making trips to neighbouring areas or of searching
offshore.
Some advance should be made in the relations between researchers,
fishermen and hunters concerning damage to nets and fish, which at present
is limited to exchange of examples. The researchers should include the
demand for the reduction and disappearance of sea lion damage in their
long term programme but the research activities and the destruction
business complement each other and at first they should probably remain
independent. The future survey will have no plans in this direction and
will be content with restricted results.
51
*
4
For more than 20 years in the USA and Canada, and more recently
in the Soviet Union, aircraft have been used to take censuses of pinnipeds
including sea lions, and they are now regarded as the conventional
means 8,20,25,39,40,46
. One of the most important subjects is the
determination of population sizes for resource studies, and it is considered
to be close to impossible to do so by accumulating small surveys such as
this. Studies of pinnipeds in Japan suffer from great handicaps concerning
funding, research organization and research personnel, and we would like
in this report to list in a few simple phrases the studies which we
consider necessary to make sea lions the centre about which this lost
opportunity can be regained.
1) A survey of the sea lion distribution in the entire area of the Hokkaiso coast21 line (survey of the state of distribution of the waters where the sea lions congregate and of the reefs on which they haul out, and more particularly a study of the state of use and of the conditions of location of the haul-out reefs)
2) Studies of the social ecology of sea lions during the non-breeding
season. (This is an area which is as yet untouched, not only for sea lions
but for other pinnipedia. Studies at selected haul-out reefs of the
seasonal and annual changes of the number and of the composition of the
herd and of the organization of the herd and the relations between the
individuals. Naturally the use of marking and telemetry should be considered).
3) Surveys of the feeding habits and the food animals of sea lions and
studies of the actual damage caused by sea lions. (At present no data
have been accumulated which researchers can use on the actual damage. This
should be combined with studies of sea lion feeding. At the same time it
will be necessary to find out the historical changes in coastal fishing
activities and the ways in which sea lions have become harmful. A
prerequisite will be cooperation between the research organization and
the sea lion destruction business).
52
4) A survey of the number of sea lions which visit all areas of the
coast of Hokkaido. (Based on studies Nos. 1, 2 and 3, the most effective
method will be simultaneous surveys by all means from boats and aircraft
and on land of the number visiting during the winter and spring periods)
5) A coordinated study by means of a survey (research) vessel. (The
Hokkaido coast would be divided into three or four areas and a vessel of
30 to 100 tons would be used for three to five years for the ecology
(herd composition, breeding circumstances, feeding, etc.), morphology
(aquatic adaption, growth),physiàogy and other basic studies. In this way
the characteristics of the Hokkaido coast as the southern limit of the
sea lion migration area will become known).
6) An oceanological study, centered on the ecology of pinnipeds and fish
in the Okhotsk Sea, the Sea of Japan and the North Pacific Ocean (a long-
term joint study by Japan, USSR, Korea, Canada and USA). This should make
it possible to understand the whole life history of sea lions, including
their migration).
' -I
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