SC/60/O5

Cruise report of the second phase of the Japanese Whale
Research Program under Special Permit in the Western North
Pacific (JARPN II) in 2007 - Offshore component MATSUOKA, K.1) , OTANI, S.1), ISODA, T.1), WADA, A.1), KUMAGAI, S.1), OHSHIMA, T.2), YOSHIMURA, I.2), SUGIYAMA,K.2), AKI, M.2), KATO, K. 3), BHUIYAN M.M.U. 4, 6), FUNASAKA, N.5), SUZUKI, Y. 6), SUDO, R.1), MOTOHASHI, Y.2), MORI,
M.2), TSUNEKAWA, M. 2), INAGAKE, D. 7), MURASE, H. 1) AND OGAWA, T.2)
1) The Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan2) Kyodo Senpaku Co. Ltd., 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan
3) Tokyo University of Marine Science and Technology, Faculty of Marine Science, 4-5-7, Konan, Minato-ku, Tokyo,108-8477, Japan
4) Department of Surgery and Obstetrics, Faculty of Veterrinary Science, Bangladesh Agricultual University,
Mymensingh 2202, Bangladesh5) Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan
6) Obihiro University of Agriculture and Veterinary Medicine, 2-11, Inada-cho, Obihiro, Hokkaido 080-8555, Japan
7) National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648,
Japan
Contact e-mail:matsuoka@cetacean.jp

ABSTRACTThe sixth cruise of the full-scale survey of the second phase of the Japanese Whale Research Program under Special
Permit in the Western North Pacific (JARPN II) -offshore component- was conducted from 11 May to 6 September
2007 in sub-areas 7, 8 and 9 of the western North Pacific. The objectives of the full-scale research were (a) feeding
ecology and ecosystem studies, (b) monitoring environmental pollutants in cetaceans and the marine ecosystem and (c)elucidation of stock structure. Target species were common minke whale (Balaenoptera acutorostrata), sei whale (B.
borealis), Bryde’s whale (B. edeni) and sperm whale (Physeter macrocephalus). A total of six research vessels wereused: one dedicated sighting vessel (SV), three sighting/sampling vessels (SSVs), one trawl and dedicated sighting
survey vessel (TSV) equipped with quantitative scientific echo sounder and one research base vessel. A total of 17,200.5
n.miles was surveyed in a period of 119 days. During that period 9 common minke, 52 sei, 235 Bryde’s and 264 sperm
whales were sighted by the SV. 148 common minke, 548 sei, 376 Bryde’s and 620 sperm whales were sighted by the
SSVs. And 5 “like common minke”, 107 sei, 76 Bryde’s and 87 sperm whales were sighted by the TSV. Biopsy samples
were collected from 2 fin whales and 1 humpback whale. And 10 blue whales and 3 humpback whales were
photographed. A total of 100 common minke, 100 sei, 50 Bryde’s and 3 sperm whales was sampled by the SSVs. All
whales sampled were examined on board the research base vessel. Common minke whales fed mainly on Pacific saury(Cololabis saira) and Mackerels in the sub-area 8 and 9 and on Japanese anchovy (Engraulis japonicus) in sub-area 7.
Sei whales fed mainly on mackerels in May and June and on copepods and Japanese anchovy in August. Bryde’s whales
fed mainly on Japanese anchovy. Sperm whales fed mainly on various kinds of squids, which inhabit the mid- and deepwaters. The whale prey species surveys were conducted by TSV using midwater trawl, IKMT and NORPAC net, CTD
and XCTD observations in a part of sub-area 7, 8 and 9. The cooperative survey on the prey species and whale sampling
to compare with results of echo sounder and stomach contents were conducted with the participation of the five vessels
in a part of sub-area 7 and 9 between 9 July and 13 August.
KEYWORDS: COMMON MINKE WHALE; BRYDE’S WHALE; SEI WHALE; SPERM WHALE; NORTHPACIFIC OCEAN; DISTRIBUTION; FOOD/PREY; ECOSYSTEM; SCIENTIFIC PERMITS

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BACKGROUND
After the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN) from 1994 to
1999, the IWC Scientific Workshop to review the survey results and data availability was held in February 2000. In thatworkshop, participants agreed that no sub-stock scenario existed within the O stock (Government of Japan, 1994) for
common minke whale in western North Pacific but the hypothesis of whether the W-stock exist (western part of subarea 9) was not resolved. Regarding the feasibility studies on feeding ecology, the workshop considered them as
successful. The results showed that the main prey species of common minke whale changed seasonally andgeographically. As most of these prey species are also the target species of Japanese commercial fisheries, possible
competition between common minke whales and fisheries was postulated. The Workshop agreed that, if ecologicalstudies are to be conducted in the area, the sampling regime must be designed to allow for a more quantitative
estimation of temporal and geographical variation in diet. It was also recommended that acoustic and trawl surveys
should be conducted concurrently with future whale surveys, if possible (IWC, 2001).
The second phase of Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPNII)
was started in the 2000 summer season as a two-year feasibility study (Government of Japan, 2000). One of the major
objectives of this research was to study the feeding ecology of whales and the marine ecosystem. During the previous
JARPN surveys, it was revealed that common minke whales consumed various commercial fish species such as Pacificsaury, Japanese anchovy. Japanese flying squids (Todarodes pacificus) and walleye pollock (Theragra chalcogramma)
and that they ate considerable amounts of these prey species. The second objective of the feasibility survey of JARPNII
is related to stock structure issues, and the third to pollution studies. Sampling of common minke, Bryde’s and sperm
whales was conducted in the feasibility research program.
Based on the success of the feasibility study (Government of Japan, 2002a) and increasingly strong support frominternational fisheries organizations, including FAO, for research to improve multi-species approaches to management,
JARPN II, as a full-scale research program, started from 2002. The full-scale study aimed mainly i) to evaluate thefeeding ecology and ecosystem studies, ii) to monitor environmental pollutants in cetaceans and the marine ecosystem
and iii) to elucidate the stock structure (Government of Japan, 2002b).
The full-scale JARPN II plan involved two survey components: the ‘offshore’ survey was covered by the Nisshin-Maru
research unit and the ‘coastal’ survey was covered by small type whaling catcher boats. The coastal component wasnecessary to cover the temporal and spatial gaps, which could not be covered by the Nisshin-Maru unit (Government ofJapan, 2002b).
Sampling of 100 minke, 50 Bryde’s and 10 sperm whales as in the JARPN II feasibility study is continued in the fullresearch program with the addition of 50 sei whales in each year and 50 common minke whales to be taken by smalltype whaling catcher boats in 2002. Sei whale is selected as a target species as they feed on fisheries resources such as
Japanese flying squid and the estimated biomass is larger than that of Bryde’s and common minke whales. The
additional 50 common minke whales provide full coverage of the spring and autumn seasons in coastal waters where thecompetition between cetaceans and fisheries is likely to be substantial. In the full JARPN II plan, the coastal survey
component was presented as a two-year feasibility study to be conducted in 2002 and 2003. The plan also noted that in
the case of the sei whale, ‘the required sample size will be recalculated after the first two years making use of the data
accumulated’ (Government of Japan, 2002b).
In accordance with these provisions, a revised JARPN II research plan was presented for the period starting from 2004,
which takes into consideration i) the results of the coastal survey component (feasibility surveys in 2002 and 2003)
regarding logistic and sample size of the common minke whales and ii) the results of new calculations of required
sample size for the sei whales based on the data accumulated in those two years. The research area was set in sub-areas
7, 8 and 9, and the target species and sample sizes in 2005 were set as follows: 160 common minke whales (100 were to
be sampled by the offshore survey and 60 - by the coastal component); 100 sei whales (offshore component), 50 Bryde’s
whales (offshore component) and 10 sperm whales (offshore component) (Government of Japan, 2004a, 2004b).
In this paper, we present an outline of the sixth full-scale survey of the JARPN II -offshore component- with thecooperative survey on the prey and whale sampling, which was conducted between 11 May and 6 September 2007.

MATERIALS AND METHODS
Research area
Sub-areas 7, 8 and 9 constituted the research area (Fig. 1). Those sub-areas were further divided as follows:2

Sub-area 7: Five small blocks (7N, 7MI, 7MO, 7SI, 7SO) were stratified for taking into account satellite information onwater temperature.
Sub-areas 8 and 9: Four small blocks were divided at latitude of 40ºN in each sub-area (8N and 8S, 9N and 9S).
In the case of the cetacean prey survey, three blocks were predetermined in the survey areas which were set in theoffshore area (see Appendix A).
Research vessels
Six research vessels were used. The research base vessel Nisshin-Maru (NM: 8,030GT) commanded the research andwas used for conducting the biological examinations of whale samples and in the processing of by-products. The
Yushin-Maru (YS1: 720GT), Yushin-Maru No.2 (YS2: 747GT) and Kyo-Maru No.1 (K01: 812.08GT) were used as thesighting/sampling vessels (SSVs), which conducted sighting activities, sampling of targeted whale species and various
experiments and observations. The Kyoshin-Maru No. 2 (KS2: 372GT) was used as a dedicated sighting vessel (SV).
The Kaiko-Maru (KK1: 860.25 GT) was engaged the cetacean prey species and whale sighting surveys (TSV) using
midwater trawl, Isaacs Kidd Midwater Trawl (IKMT), NORPAC net and Oceanographic observations.
Survey components
The survey was composed of three main components: (1) dedicated sighting survey, (2) whale survey and (3) the whale
prey species survey (Table 1).
Dedicated sighting survey
Vessel: One research vessel (SV)
Research area: Sub-areas 7, 8 and 9
Research period: From 11 May to 1 August
Whale survey
Vessels: Four research vessels (three SSVs and NM)
Research area: Sub-areas 7, 8 and 9. In addition, a ‘special monitoring survey’ (SMS) was settled in some areas where
the number of common minke, Bryde’s and sei whales was expected to be abundant.
Research period:First period:

From 11 May to 8 July.

Second period:

From 9 July to 18 August.

Cooperative survey on the prey species and whale sampling
Vessels: Five research vessel (three SSVs, NM and TSV)
Research area: Three blocks (1, 2 and 3).
Research period: Block 1 (from 9 to 22 July), block 2 (from 3 to 5 August) and block 3 (from 11 to 13 August).
Methods for setting cruise track line for the whale survey
Track lines and allocation of vessels were made as in previous JARPN and JARPN II surveys (Fujise et al., 1995, 1996,
1997, 2000, 2001, 2002, 2003; Ishikawa et al., 1997; Zenitani et al., 1999; Tamura et al., 2004, 2005, 2006 and 2007).
The zigzag-shaped track line was established on an arbitrary basis in each sub-area and month, taking into consideration
previous sighting information of target whales and sea conditions.
Furthermore, some ‘special monitoring surveys’ (SMS) were conducted in areas where the abundance ofcommon minke whales, Bryde’s and sei whales was expected to be high. Track line in the SMS was designed separatelyfrom the original track line. Three SSVs were allocated to these tracks with the allocation being changed every day.
The SSVs surveyed in the following manner: the research course consisted of one main track and two parallel tracks
established in 7 n.miles apart from both sides. The track line of the TSV in the cooperative survey was determined andthe zigzag-shaped track line was set independent of whale survey.
Apart from these sampling activities, an independent track line for dedicated sighting survey was determined in
the research area.

3Sighting surveys
Sighting procedure both for the whale survey and dedicated sighting survey was similar to the previous surveys of
JARPN and JARPN II. In the research area sighting survey was conducted mainly under closing modes (NSC and NSS
modes) by the SSVs. Furthermore two modalities of sighting in closing mode by the SSVs were adopted, NSC and NSS
modes, by taking into consideration weather and sea conditions mainly. The NSC and NSS modes were the same as BC
and BS modes in the previous JARPN II surveys, respectively. The conditions to conduct sighting surveys by the SSVs
under NSC mode were similar to those established in Japanese sighting surveys conducted by the National ResearchInstitute of Far Seas Fisheries (i.e. visibility of 2 n.miles or more and wind force of 4 or below). The NSS mode by the
SSVs was used under more bad weather conditions such as heavy rain and fog but under this condition the collection ofwhale samples was possible. This NSS mode was used only by SSVs.
The ASP and NSP modes by the SV and TSV were used (ASP: closing mode under normal sighting conditions,
NSP: passing mode under normal sighting conditions). Closing was performed mainly on sightings of common minke,
Bryde’s, sei and sperm whales. Furthermore closing was made on sightings of large whales, such as blue, humpback,right and fin whales. In these cases, closing was done in order to confirm species and school size and in order to conduct
some experiments.
Sampling of common minke, Bryde’s, Sei and sperm whales
Most of the target whale species sighted on the trackline were approached for sampling. Furthermore sampling effort
was applied outside the established research hours (SSV: 06:00-19:00, SV: 06:00-18:00), if collection of whale samples
was considered as possible.
For schools consisting of two or more animals, numbering was made for all the whales in the school; to set samplingorder randomly in accordance with the table of random numbers (Kato et al., 1989). Cow and calf pairs were nottargeted for sampling.
Sampled whales were immediately transported to a research base vessel, where biological measurements and sampling
were carried out.
Cooperative survey on the prey species and whale sampling
Prey distribution and abundance surveys using the quantitative echo sounder, midwater trawl, IKMT and NORPAC with
XCTD oceanographic observation were conducted by the TSV. In addition to the whale prey survey, TSV conducted
dedicated sighting survey within the cooperative survey area. During the daytime, TSV steamed at about 10 knots along
the tracklines to conduct cetacean sighting and acoustic survey. Research hour was from an hour after sunrise to an hour
before sunset while the maximum research hours were set at 13 hours. Generally, the survey started at 5:00 and end at
18:00 at local time. Detailed report on this activity is shown in Appendix A.
Experiments
The following experiments and observations were conducted on board the SSV:
1. Sighting distance and angle experiments to examine the precision of sighting data (YS1, YS2 and K01).
2. Biopsy sampling on gray, blue, fin, sei, Bryde’s, minke, humpback, right, bowhead and sperm whales.
3. Photographic records of natural marks in blue, humpback and right whales.
4. Preliminary examination of attachment of satellite tag to common minke, sei and Bryde’s whales.
5. Feeding behaviour observation of large whale species (blue, fin, sei, Bryde’s, common minke, humpback, right andsperm whales).
On board the SV and TSV, the following experiments and observations were conducted:
1. Sighting distance and angle experiment to examine the precision of sighting data.
2. Biopsy sampling on gray, blue, fin, sei, Bryde’s, minke, humpback, right, bowhead and sperm whales.
3. Photographic records of natural marks in blue, humpback and right whales.
4. Feeding behaviour patterns of large whales.
5. Oceanographic observations using EPCS (Electric particle counting and sizing system), CTD and XCTD.

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Observations of marine debris in the research area were conducted from the wheelhouse of the research base vessel(NM) (mainly during transit cruises). Marine debris was also investigated in the stomach contents of common minke,
Bryde’s, sei and sperm whales sampled. Experiments on killing method were conducted onboard of both the researchbase vessel and the SSVs.

RESULTS
Searching distance
Track line covered by the SV is shown in Figs. 2a and 2b. Track line covered by the SSVs is shown in Fig. 3.The total
searching distances were 4,042.5 n.miles by the SV, 11,416.4 n.miles by the SSVs and 1,741.6 n.miles by the TSV(Table 2).
Sightings of common minke, sei, Bryde’s, sperm and other large whales
Dedicated sighting survey
During the research cruise by the SV, 9 schools (9 individuals) of common minke whales were sighted, consisting of 8
schools (8 individuals) of primary sightings and 1 school (1 individual) of secondary sightings. For sei whale, 35
schools (52 individuals) were sighted, consisting of 34 schools (51 individuals) of primary sightings and 1 school (1individual) of secondary sightings. For Bryde’s whale, 152 schools (235 individuals) were sighted, consisting of 148
schools (229 individuals) of primary sightings and 4 schools (6 individuals) of secondary sightings. For sperm whale,
101 schools (264 individuals) were sighted, consisting of 90 schools (248 individuals) of primary sightings and 11
schools (16 individuals) of secondary sightings. Large baleen whales such as blue (2 schools /5 individuals), fin (20schools /24 individuals) and humpback whales (8 schools /12 individuals) were found in the sub-areas 7, 8 and 9 (Table
3a, Fig. 2a and 2b).
Whale survey
During the research cruise by the SSVs, a total of 146 schools (148 individuals) of common minke whales were sighted,
consisting of 63 schools (64 individuals) of primary and 83 schools (84 individuals) of secondary sightings. For sei
whales, 298 schools (548 individuals) were sighted, consisting of 204 schools (398 individuals) of primary sightings and
94 schools (150 individuals) of secondary sightings. For Bryde’s whales, 260 schools (376 individuals) were sighted,
consisting of 215 schools (314 individuals) of primary sightings and 45 schools (62 individuals) of secondary sightings.
For sperm whales, 231 schools (620 individuals) were observed, consisting of 173 schools (457 individuals) of primarysightings and 58 schools (163 individuals) of secondary sightings. Large baleen whales such as blue (14 schools / 17
individuals), fin (33 schools /42 individuals), humpback (46 schools /85 individuals) and North Pacific right whales (oneschool /one individual) were found in the sub-areas 7, 8 and 9 (Table 3b).
Cooperative survey on the prey species and whale sampling
During the research cruise by the TSV, a total of 5 schools (5 individuals) of like common minke whales were sighted,
consisting of 3 schools (3 individuals) of primary sightings and 2 schools (2 individuals) of secondary sightings. For sei
whale, 56 schools (107 individuals) were sighted, consisting of 55 schools (105 individuals) of primary sightings and 1
school (2 individuals) of secondary sightings. For Bryde’s whale, 47 schools (76 individuals) were sighted, consisting of
42 schools (69 individuals) of primary sightings and 5 schools (7 individuals) of secondary sightings. For sperm whale,
60 schools (87 individuals) were observed, consisting of 59 schools (86 individuals) of primary sightings and 1 school(1 individual) of secondary sightings. Large baleen whales such as blue (2 schools / 3 individuals) and fin (5 schools /5
individuals) whales were found in the sub-areas 7, 8 and 9 (Table 3c).
List of cetacean species and number of sightings (no. schools/no. individuals) were made by all vessels in the 2007
JARPN II are shown in Table 3d.

Sampling of common minke, sei, Bryde’s and sperm whales
This survey covered spatial and temporal gaps for studies on feeding ecology and stock structure. Table 4 shows thenumber of whales sampled in each sub-area or special block for each research component and period. A total of 100
common minke whales (Male: 86 individuals, Female: 14 individuals) were sampled. A total of 100 sei whales (Male:
54 individuals, Female: 46 individuals) were sampled. A total of 50 Bryde’s whales (Male: 23 individuals, Female: 27
individuals) were sampled. A total of three sperm whales (Female: 3) were sampled during the whale survey component.

5Geographical distribution of common minke, Bryde’s, sei and sperm whale samples are also shown in Fig. 3 based on
the sighting positions.
Cooperative survey on the prey species and whale sampling
During the cooperative survey on the prey species and whale sampling, a total of 18 sei, 28 Bryde’s and one sperm
whales were sampled in the block 1. A total of 5 sei and 2 Bryde’s whales were sampled in the block 2. A total of 15
Bryde’s whales were sampled in the block 3 (Table 4).
Biological research for common minke sei, Bryde’s and sperm whales
Table 5 summarizes the biological data and samples collected from whale sampled such as the common minke, sei,
Bryde’s and sperm whales sampled. A total of 52 research items were covered. These items are related to the studies
conducted under the three main objectives of the JARPN II: study on feeding ecology of whales and marine ecosystem,
pollution studies and elucidation of stock structure. Composition of sex and sexual maturity of common minke, sei and
Bryde’s whales is shown in Tables 6a, 6b and 6c, respectively. The rate of mature males in common minke was higher
than in Bryde’s and sei whales.
Preliminary analyses of biological data and experiments
Body length of sampled whales
The statistics of body length of whales sampled are shown in Tables 7a, 7b, 7c and 7d. Mean body length of common
minke whales is 7.25 m and 6.50 m for males and females, respectively. For sei whales, mean body length is 13.14 m
and 13.84 m for males and females, respectively (Table 7b). Mean body length of Bryde’s whales is 11.44 m and 11.93
m for males and females, respectively (Table 7c). For sperm whale, mean body length is 10.06 m for females (Table 7d).
Distribution and food habit
During research season (from May to August) in the offshore area, common minke whales fed mainly on Pacific saury.
They also fed on mackerels. On the other hand, the common minke whales fed mainly on Japanese anchovy and walleye
pollock in coastal area. The geographical changes of the prey species of the common minke whales seem to reflectchanges in the distribution of prey species in feeding areas. The common minke whales seem to be opportunistic feeders
with a broad diet and with flexible feeding habits in the research area (Table 8a). Sei whales were distributed widely inthe research area. From May to August, they fed mainly on copepods, mackerels, Japanese anchovy and krill in the
research area. The sei whales seem to be opportunistic feeders with a broad diet and with flexible feeding habits in the
research area. There are geographical and seasonal changes of their prey species (Table 8b). Bryde’s whales were
distributed in the southern part of research area during research periods. They fed mainly on Japanese anchovy. They
also fed on mackerels (Table 8c). Sperm whales were distributed widely in the research area. From three sperm whale
samples, they fed mainly on deep sea squids in offshore area (sub-area 9).
Experiments, whale prey species surveys and oceanographic surveys
Biopsy sampling
Table 9 shows the results of biopsy skin sampling for blue, fin and humpback whales. A total of 3 blue, 4 fin and 3
humpback whales were targeted by the SV and SSVs. As a result, 2 fin and 1 humpback whale’s skin samples werecollected.
Natural marks (photo ID) for blue and humpback whales
Table 10 shows the result of the photo-ID experiments on blue and humpback whales. A total of 10 blue and 3
humpback whales were targeted and 8 blue and 2 humpback whales photographed by the SV and SSVs.
Feeding behaviour for large baleen whales
The SV and SSVs had a plan to conduct recording of the feeding behaviour of large baleen whales using a video
recorder. A total of 24 schools of Bryde’s and 2 schools of sei whale’s feeding behaviour were observed. However,
because of far from distance from the schools, it was difficult to take video recording for these schools.
Cooperative survey on the prey species and whale sampling
Echo sounder survey was conducted on TSV (KK1) and they operated to cover the planned track lines using a Simrad
EK500 echo sounder with operating frequencies at 38 and 120 kHz was carried out to quantify prey abundance as wellas to elucidate the distribution patterns. Species compositions of acoustical backscatterings were identified using
midwater trawl and plankton nets. In addition, trawls were towed at predetermined stations independently from theacoustic survey. IKMT and NORPAC were used to collect zooplanktons. Midwater trawl, IKMT and NORPAC were6

towed at 66, 12 and 62 stations, respectively. The details of these survey conducted by TSV are described in Appendix
A.
Oceanographic observation
CTD (Model SBE 19) casts were made at 16 stations by SV with down to 500m at each station to collect thetemperature and salinity profiles in the study area. Oceanographic observations were conducted using CTD and XCTD
(1,000m) at 57 and 16 stations respectively by TSV. EPCS (Electric particle counting and sizing system) data werecollected at 913 hours by SV.
Attachment of satellite telemetry
One satellite telemetry tag was attached for sei whale in the Western North Pacific dated 4th August by YS2. However,position data was not received successfully.
By-products of whales
After biological measurements and sampling were completed, all the whales were processed according to Article VIII of
The International Convention for the Regulation of Whaling. Total production including red meat and blubber from 100
sampled common minke, 100 sei, 50 Bryde’s and 3 sperm whales was 258 tons, 1,220 tons, 413 tons and 9 tons,
respectively.

DISCUSSIONSThis sixth JARPN II was completed satisfactorily. New samples and data ware collected to allow advances in the main
objectives of JARPN II, some of samples and data were collected from areas and months not covered in previous
surveys.
The distributions and food habits of whales targeted
Common minke whale
Common minke whales were widely distributed in the sub-area 7, 8 and 9. They were not found in the southern parts of
sub-area 7, 8 and 9, where surveyed after late June. It was confirmed that they migrated into higher latitude waters
during the summer season. Regarding to seasonal movement, Hatanaka and Miyashita (1997) conducted theexamination of movement of common minke whales in the western North Pacific. They summarized the pattern ofseasonal movement of the O stock as follows: i) immature males migrate into the coastal area of sub-area 7 south inApril and then disperse to sub-area 7 north and the southern Okhotsk Sea from June, ii) immature females follow asimilar pattern of immature males, iii) mature males found throughout coastal and offshore waters during May to
September, iv) mature females are found in the Okhotsk Sea in May, after which they move further north to the middle
and northern Okhotsk Sea. In this research, the proportion of mature females was only 6.0% (6 individuals). This fact isindirect confirmations of the hypothesis that in summer season almost all females are feeding in the Okhotsk Sea.
In recent years, during early seasons (May - June) in the sub-areas 8 and 9, Japanese anchovy was the dominant
prey species (Tamura and Fujise, 2002a). However, they fed mainly on Pacific saury, krill and Chub mackerel this year.
It seems likely that the Japanese anchovy will be replaced by other prey in this year in sub-areas 8 and 9. On the other
hand, coastal area in sub-area 7 during June, Japanese anchovy was the dominant prey species in this research. This isconsistent with the results of previous years. We confirmed that Japanese anchovy was the most important prey species
for common minke whales in the coastal area in sub-area 7.
Sei whale
Sei whales were sighted mainly in the sub-areas 8 and 9. It was confirmed that they were distributed into middle andhigher latitude waters in the research area during the summer season. Our research seems to investigate habitat of thesouthern limit of their distribution. Sighting north of 45 oN was few, because we could not conduct the research activity
due to bad weather such as high density fog. In recent years, during all seasons (May - September), Copepods andJapanese anchovy were the dominant prey species. And, during late season (July – August), Japanese anchovy was thedominant prey species (Tamura et al., 2006). However, they fed mainly on mackerels in the sub-areas 8 and 9 during
early season (May - June) this year. This is first information through the JARPNII. During late season (July - August),
Japanese anchovy was the dominant prey species which is consistent with the results of previous years.
Bryde’s whale
Bryde’s whales were sighted mainly in the southern part of sub-areas 7, 8 and 9. It was confirmed that they were
distributed in lower latitude waters in the research area during the summer season. Regarding seasonal movement, some7

researchers conducted the examination of movement of Bryde’s whales in the western North Pacific that Bryde’s whales
were distributed south of 40 oN within higher surface water temperatures (over 20 oC) and migrated in the areas of thehigher surface water temperature of 18 oC or more degrees. Water temperature of 20 oC was their distribution boundary
in the offshore (Nemoto, 1959). In this research, it was confirmed that their distribution area was south of 40 oN, and our
research seems to investigate habitat of the northern limit of their distribution. In previous years, during early seasons(May - June), krill was the dominant prey species. And, during late season (July – August), Japanese anchovy was thedominant prey species (Tamura and Fujise, 2002b). In this research they fed mainly on Japanese anchovy in the researcharea in July and August which is consistent with the results of previous years.
The importance of the research for ecosystem modelling
In this research, there was difference of prey species among three baleen whale species. Especially, the proportion ofJapanese anchovy as the prey for baleen whales was lower than that in previous years. It is well known that the mostabundant species were replaced successively starting with the Japanese sardine, Pacific saury and Japanese anchovy,chub mackerel and Japanese sardine again in periods of 10 to 20 years in Japanese waters (Yatsu et al. 2001). In recent
years, Japanese anchovy was dominant. Japanese anchovy will be replaced by other fishes in the future. There is a needto monitor the resource of prey species and the food habit of whales. Our results will be used to build ecosystem models.

ACKNOWLEDGMENTS
The present research project (JARPN II) was funded under the subsidy of the Ministry of Agriculture, Forestry and
Fisheries, Government of Japan. The authors are greatly indebted to Mr. Joji Morishita and Mr. Hideki Moronuki, theFisheries Agency of Japan, Dr. Hidehiro Kato, Tokyo University of Marine Science and Technology, and Mr. Minoru
Morimoto, Dr. Hiroshi Hatanaka, Dr. Seiji Ohsumi, Dr. Yoshihiro Fujise, Dr. L.A. Pastene, and Mr. Shigetoshi
Nishiwaki and staff of the Institute of Cetacean Research (ICR) for their guidance in the design and implementation of
the research. We thank all Captains, officers and crew of the research vessels and the staff of the ICR, Kyodo-Senpaku
Co. Ltd. and Kaiko-Senpaku K.K.

REFERENCES
Fujise, Y., Kishiro, T., Zenitani, R., Matsuoka, K., Kawasaki, M. and Shimamoto, K. 1995. Cruise report of the Japanese whale research program
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Fujise, Y., Tamura, T., Bando, T., Watanabe, H., Kiwada, H., Otani, S., Kanda, N., Yasunaga, G., Mogoe, T., Konishi, K., Inamori, M., Shigemune, H.
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Fujise, Y., Tamura, T., Bando, T., Yasunaga, G., Konishi, K., Murase, H., Yoshida, T., Itoh, S. Ogawa, R., Oka, T., Sasaki, T., Fukutome, K., Isoda,T., Birukawa, N., Horii, N., Zharikov, K.A., Park, K.J., Tohyama, D. and Kawahara, S. 2003. Cruise report of the Japanese whale research program
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8

Government of Japan. 2002b. Research Plan for Cetacean Studies in the Western North Pacific under Special Permit (JARPN II) Paper SC/54/O2
presented to the IWC Scientific Committee, May 2002 (unpublished). 115pp.
Government of Japan. 2004a. Revised research plan for cetacean studies in the western North Pacific under special permit (JARPN II). Paper
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Kato, H., Hiroyama, H., Fujise, Y. and Ono, K. 1989. Preliminary report of the 1987/88 Japanese feasibility study of the special permit proposal forSouthern Hemisphere minke whales. Report of the International Whaling Commission, 39: 235-248.
Nemoto, T. 1959. Food of baleen whales with reference to whale movements. Sci. Rep. Whales Res. Inst., Tokyo, 14: 149-291.
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Kawahara, S., Pastene, L.A. and Hatanaka, H. eds.), Report of 2000 and 2001 feasibility study of the Japanese Whale Research Program underSpecial Permit in the western North Pacific-Phase II (JARPN II). Paper SC/54/O17 submitted to the 54th IWC Scientific Committee Meeting.
Tamura, T., Fujise, Y., Bando, T., Yasunaga, G., Konishi, K., Kiwada, H., Isoda, T., Itoh, S. Machida, S., Tsunekawa, M., Konagai, T., Takamatsu, T.,
Ohshima, T., Honjo, K., Matsuoka, T., Zharikov, K.A., Yong, Rock AN, Tohyama, D. and Kawahara, S. 2004. Cruise Report of the Japanese Whale
Research Program under Special Permit in the western North Pacific -Phase II (JARPN II) in 2003 (part I) - Offshore component –. Paper
SC/56/O13 presented to the IWC Scientific Committee, June 2004 (unpublished). 46pp.
Tamura, T., Fujise, Y., Mogoe, T., Kanda, N., Yasunaga, G., Konishi, K., Kiwada, H., Ogihara, M., Hasegawa, A., Kitajima, M, Sugiyama, T., Sasaki,T., Mori, M., Teraoka, T., Tsunekawa, M., Fukutome, K., Zharikov, K.A, NA, Jong-Hun., Tohyama, D, Inagake, D. and Kawahara, S. 2005. Cruise
Report of the Japanese Whale Research Program under Special Permit in the western North Pacific -Phase II (JARPN II) in 2004 (part I) - Offshore
component –. Paper SC/57/O3 presented to the IWC Scientific Committee, June 2005 (unpublished). 33pp.
Tamura, T., Otani, S., Kiwada, H., Mori, M., Konishi, K., Isoda, T., Wada, A., Ogihara, M., Hasegawa, A., Kumagai, S., Komatsu, W., Hayasaka, K.,
Fukutome, M., Siozaki, M., Zharikov, K.A, NA, Jong-Hun., Ogawa, T, Watanabe, H., Yonezaki, S, Inagake, D. and Kawahara, S. 2006. Cruise
report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2005 –Offshore component –. Paper SC/58/O8 presented to the IWC Scientific Committee, June 2006 (unpublished). 52pp
Tamura, T., Matsuoka, K., Bando, T., Mogoe, T., Konishi, K., Mori, M., Tsunekawa, M., Okamoto, K., Funasaka, N., Sakajiri, H., Yoshida, Y.,
Kumagai, S., Kimura, K., Takamatsu, T., Konagai, T., Sasaki, T., Kuwaoka, J. and Ogawa, T., 2007. Cruise Report of the Japanese Whale Research
Program under Special Permit in the western North Pacific -Phase II (JARPN II) in 2006 (part I) - Offshore component –. Paper SC/59/O5 presented
to the IWC Scientific Committee, June 2007 (unpublished). 26pp.
Yatsu, A., Nishida, H., Tomosada, A., Kinoshita, T. and Wada, T. 2001. Trajectories of catch and stock abundance of dominant small pelagic fishes
and common squid with some related environmental indices around Japan. PICES Sci. Rep. 18: 175-8.
Zenitani, R., Fujise, Y., Matsuoka, K., Tamura, T., Bando, T., Ichihashi, H., Shimokawa, T., Krasnenko, A.S., Taguchi F., Kinoshita, T., Mori, M.,
Watanabe, M., Ichinomiya, D., Nakamura, M., Sakai, K., Matsuzaka, K., Kamei, H. and Tohyama, D. 1999. Cruise report of the Japanese Whale
Research Program under a Special Permit in the North Pacific in 1998. Paper SC/51/RMP7 presented to the IWC Scientific Committee, May 1999
(unpublished). 20pp

9

Table 1. Outline of 2007 JARPN II survey.

・Dedicated whale sighting surveys (SV)
Research

Sub-

ResearchResearcharea

periods
May 11
May 12-14
May 15- July 30
July 31
August 1

Days
1
3
77
1
1

Research ships and remarks

Departure from ShiogamatransitSighting survey
transit
Arrived Shiogama

KS2
KS2
KS2
KS2
KS2

7, 8, 9Total

7, 8, 9May 11- August 1

83

Sub-

ResearchResearcharea

periods

Days

7, 8, 9May 11-July 4
May 11
May 12
May 12
May 13-17
May 18- 25
May 26- June 10
June 11-15
June 16- July 3
July 4

55
1
1
5
8
16
5
18
1

YS1, YS2, K01, NM
YS1, YS2, K01
NM
YS1, YS2, K01
YS1, YS2, K01
YS1, YS2, K01, NM
YS1, YS2, K01, NM
YS1, YS2, K01, NM
YS1, YS2, K01, NM
YS1, YS2, K01, NM

7, 8, 98, 98, 9 *
9
9*
7,8
7,8*

July 5-August 18
July 5-8
July 9- 22
July 23-August 2
August 3-5
August 6-10
August 11-13
August 14-16
August 17
August 18

45
4
14
11
3
5
3
3
1
1

YS1, YS2, K01, NM, KK1
YS1, YS2, K01
YS1, YS2, K01, NM, KK1
YS1, YS2, K01, NM
YS1, YS2, K01, NM, KK1
YS1, YS2, K01
YS1, YS2, K01, NM, KK1
YS1, YS2, K01, NM
YS1, YS2, K01
NM

Total
7, 8, 9*: Cooperative survey on the prey species and whale sampling.

May 11-August 18

100

・Whale survey (SSV)
Research
Whale survey (first period)
Departure from Shimonoseki
Departure from Innoshimatransitpre-survey

7, 8
8
9
8
7

transit
Whale survey (second period)
pre-survey
Block 1
Block 2pre-survey
Block 3transit
Arrived Shimonoseki
Arrived Ishinomaki

Research ships and remarks

YS1= Yushin Maru, YS2= Yushin Maru No.2, K01= Kyo Maru No.1, NM= Nisshin Maru, KK1=Kaiko-Maru.

・Dedicated whale sighting & whale prey species surveys (TSV)Sub-

ResearchResearcharea

periods
July 4
July 5-6
July 7-September 4
September 5
September 6

Days
1
2
60
1
1

Total
7, 8, 9July 4- September 6*: including cooperative survey on the prey species and whale sampling. (See Appendix B).

65

Research
Departure from ShiogamatransitSighting & whale prey species survey*
transit
Arrived Kushiro

7, 8, 9

10

Research ships and remarks
KK1 (Kaiko-Maru )
KK1
KK1
KK1
KK1

Table 2. Searching distances made by the dedicated sighting vessel (SV), three sighting/sampling vessels (SSVs) and the
dedicated whale sighting and whale species surveys (TSV) in the 2007 JARPN II.

SV
Sub-area

Research
Dedicated sighting survey

7, 8, 9Total

7, 8, 9Searching distance (n.miles）

Research
periods

ASP

NSP

Combined

May 11- August 1

4,005.5

37.0

4,042.5

4,005.5

37.0

4,042.5

SSV
Sub-area

Research
periods

NSC

ASP

NSS

Combined

7, 8, 9May 11-July 44,923.0880.2

1,231.5

7,034.7

7

May 13-17

0.0

727.3

0.0

727.3

8

May 18- 25

22.8

0.0

583.6

606.4

9

May 26- June 10

1,608.3

152.9

388.9

2,150.1

8

June 11-15

1,194.3

0.0

8.7

1,203.0

7

June 16- July 3

2,097.6

0.0

250.3

2,347.9

Whale survey (second period)

7, 8, 9July 5-August 18

2,182.5

1,709.0490.2

4,381.7

pre-survey

8, 9July 5-8

0.0

183.4

0.0

183.4

8, 9 *

July 9- 22

973.4

359.8

139.7

1,472.9

9

July 23-August 2

756.7

0.0

294.2

1,050.9

Research
Whale survey (First period)
pre-survey

Block 1
Block 2pre-survey
Block 3
Total

Searching distance (n.miles）

9*

August 3-5

396.1

18.6

56.3

471.0

7,8

August 6-10

0.0

791.6

0.0

791.6

7,8*

August 11-13

56.3

355.6

0.0

411.9

7, 8, 9May 11-August 18

7,105.5

3,499.9

1,721.7

11,416.4*: Cooperative survey on the prey species and whale sampling.

TSV
Research・Dedicated whale sighting

Sub-area
7, 8, 9Research

Searching distance (n.miles）

periods

ASP

NSP

Combined

July 4- September 6

0.0

1,741.6

1,741.6

0.0

1,741.6

1,741.6& whale prey species surveys
Total

7, 8, 911

Table 3a. List of cetacean species and number of sightings (no. schools/no. individuals) were made by the SV in the2007 JARPN II.
ASP

OE

Primary

Total

Secondary

Secondary

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Common minke whale

8

8

1

1

0

0

8

8

1

1

9

9

Like minke whale

0

0

0

0

0

0

0

0

0

0

0

0

Blue whale

1

4

1

1

0

0

1

4

1

1

2

5

Fin whale

18

22

2

2

0

0

18

22

2

2

20

24

Cetacean species

Primary

SecondaryTotal

Sei whale

34

51

0

0

1

1

34

51

1

1

35

52

Bryde's whale

148

229

4

6

0

0

148

229

4

6

152

235

Humpback whale

8

12

0

0

0

0

8

12

0

0

8

12

Sperm whale

90

248

11

16

0

0

90

248

11

16

101

264

Unidentified large cetacean

12

12

26

37

1

1

12

12

27

38

39

50

Unidentified cetacean

13

13

2

2

0

0

13

13

2

2

15

15

Table 3b. List of cetacean species and number of sightings (no. schools/no. individuals) were made by the SSVs and the
NM in the 2007 JARPN II.
NSC
Primary

Cetacean species

NSS
SecondaryPrimary

ASP
SecondaryPrimary

OE
Secondary

Secondary

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Common minke whale

57

58

63

64

5

5

11

11

1

1

0

0

9

9

Like minke whale

4

4

10

10

1

1

0

0

0

0

0

0

1

1

Blue whale

8

10

1

1

4

5

0

0

1

1

0

0

0

0

Fin whale

21

27

0

0

3

3

2

2

7

10

0

0

0

0

Sei whale

155

293

62

103

15

22

21

31

34

83

1

1

10

15

Bryde's whale

34

44

21

31

6

9

9

10

175

261

10

14

5

7

Humpback whale

20

36

4

5

3

4

2

3

16

35

1

2

0

0

North Pacific right whale

0

0

0

0

1

1

0

0

0

0

0

0

0

0

Sperm whale

117

323

45

129

10

23

5

13

46

111

7

20

1

1

Unidentified large cetacean

13

14

76

114

4

4

20

23

3

3

16

21

5

5

Unidentified cetacean

37

39

15

15

5

5

3

3

2

2

0

0

1

1

Total
Primary

Cetacean species

Secondary

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Common minke whale

63

64

83

84

146

148

Like minke whale

5

5

11

11

16

16

Blue whale

13

16

1

1

14

17

Fin whale

31

40

2

2

33

42

Sei whale

204

398

94

150

298

548

Bryde's whale

215

314

45

62

260

376

Humpback whale

39

75

7

10

46

85

North Pacific right whale

1

1

0

0

1

1

Sperm whale

173

457

58

163

231

620

Unidentified large cetacean

20

21

117

163

137

184

Unidentified cetacean

44

46

19

19

63

65

12

Table 3c. List of cetacean species and number of sightings (no. schools/no. individuals) were made by the TSV in the2007 JARPN II.

NSP
Primary

Cetacean species

OE

Total

Secondary

SecondaryPrimary

Secondary

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Like minke whale

3

3

2

2

0

0

3

3

2

2

5

5

Blue whale

2

3

0

0

0

0

2

3

0

0

2

3

Fin whale

5

5

0

0

0

0

5

5

0

0

5

5

Sei whale

55

105

1

2

0

0

55

105

1

2

56

107

Bryde's whale

42

69

5

7

0

0

42

69

5

7

47

76

Sperm whale

59

86

1

1

0

0

59

86

1

1

60

87

Unidentified large cetacean

67

86

17

23

0

0

67

86

17

23

84

109

Table 3d. List of cetacean species and number of sightings (no. schools/no. individuals) were made by all vessels in the2007 JARPN II.
Total
Primary

Cetacean species

Secondary

Total

Sch.

Ind.

Sch.

Ind.

Sch.

Ind.

Common minke whale

71

72

84

85

155

157

Like minke whale

8

8

13

13

21

21

Blue whale

16

23

2

2

18

25

Fin whale

54

67

4

4

58

71

Sei whale

293

554

96

153

389

707

Bryde's whale

405

612

54

75

459

687

Humpback whale

47

87

7

10

54

97

North Pacific right whale

1

1

0

0

1

1

Sperm whale

322

791

70

180

392

971

Unidentified large cetacean

99

119

161

224

260

343

Unidentified cetacean

57

59

21

21

78

80

13

Table 4. Summary of whale sampling in the 2007 JARPN II survey.

Whale survey (First period)

Whale survey (second period)
Block 1

Total

Whale samples

Sub-area

PeriodCommon minke

Sei

Beyde'sSperm7, 8, 9May 11-July 4

100

69

5

2

8

May 18- 25

1

17

0

0

9

May 26- June 10

6

44

0

2

8

June 11-15

14

2

0

0

7

June 16- July 4

79

6

5

0

7, 8, 9July 5-August 18

0

31

45

1

8, 9 *

July 9- 22

0

18

28

1

9

July 23-August 2

0

8

0

0

Block 29*August 3-5

0

5

2

0

Block 37,8*August 11-13

0

0

15

0

7, 8, 9May 11-August 18

100

100

50

3

*: Cooperative survey on the prey species and whale sampling.

14

Table 5. Summary of biological data and samples collected during the 2007 JARPN II survey.
Common minke

Samples and data
Body length and sex
External body proportion
Photographic record and external character
Diatom film record
Standard measurements of blubber thickness (five points)
Detailed measurements of blubber thickness (eleven points)
Body weight
Body weight by parts
Blubber tissues for DNA study
Blubber, muscle, liver and kidney tissues for heavy metal analysis
Blubber, muscle, liver and kidney tissues for organochlorines analysis
Blubber, muscle tissues for ingredient analysis
Lung tissue for atmospheric analysis
Tissues for lipid analysis
Tissues for various analysis
Tissues for virus test
Mammary gland; lactation status, measurement and histological sample
Collection of spermaceti sample
Collection of maternal milk sample
Uterine horn; measurement and endometrium sample
Collection of ovary
Photographic record of foetus
Foetal sex (identified by visual observation)
Foetal length and weight
External measurements of foetus
Foetal blubber tissues for DNA study
Foetal tissues for various analysis
Foetal lens for age determination
Testis and epididymis; weight and histological sample
Collection of plasma sample
Collection of whole blood sample
Whole blood samples from umbilical cord
Plasma samples from umbilical cord
Stomach content, conventional record
Volume and weight of stomach content in each compartment
Stomach contents for feeding study
Record of external parasites
Collection of external parasites
Record of internal parasites
Collection of internal parasites
Earplug for age determination
Tympanic bulla for age determination
Maxillally teeth for age determination
Lens for age determination
Largest baleen plate for morphologic study and age determination
Baleen plate measurements (length and breadth)
Length of each baleen plate series
Vertebral epiphyses sample
Number of vertebrae
Number of ribs
Brain weight
Skull measurement (length and breadth)*1

including twins*2including a fetus of sex unidentified

15

Sei whale

Bryde's whale

Sperm whale

M

F

T

M

F

T

M

F

T

M

F

T

86
86
86
86
86
14
86
14
86
86
86
3
8
14
86
86
2
2
2
2
2
2
2
86
86
86
86
86
86
86
5
86
0
86
86
86
86
84
86
86
0
86
14
83

14
14
14
14
14
1
14
1
14
14
14
2
0
1
14
6
14
0
14
14
5
5
5
5
5
5
5
14
14
3
5
14
14
14
14
1
14
0
14
14
14
14
14
14
14
0
14
1
13

100
100
100
100
100
15
100
15
100
100
100
5
8
15
100
92
14
0
14
14
*1
7
*1
7
*1
7
*1
7
*1
7
*1
7
*1
7
86
100
100
3
5
100
100
100
100
6
100
0
100
100
100
100
98
100
100
0
100
15
96

54
54
54
54
54
13
54
13
54
54
54
2
10
14
54
54
15
15
15
15
15
14
14
54
54
54
54
54
54
54
5
54
3
54
54
54
54
54
54
54
13
54
12
52

46
46
46
46
46
13
46
13
46
46
46
2
0
13
46
25
46
0
46
46
10
10
10
10
10
9
9
46
46
15
22
46
46
46
46
7
46
6
46
46
46
46
46
46
46
13
46
13
42

100
100
100
100
100
26
100
26
100
100
100
4
10
27
100
79
46
0
46
46
25
25
25
25
25
23
23
54
100
100
15
22
100
100
100
100
12
100
9
100
100
100
100
100
100
100
26
100
25
94

23
23
23
23
23
6
23
6
23
23
23
1
8
6
23
23
4
4
4
4
4
3
3
23
23
23
23
23
23
23
3
23
2
23
23
23
23
23
23
23
6
23
6
21

27
27
27
27
27
7
27
7
27
27
27
3
0
7
27
15
27
1
27
27
10
10
10
10
10
10
10
27
27
11
13
27
27
27
27
3
27
5
27
27
27
27
27
27
27
7
27
7
26

50
50
50
50
50
13
50
13
50
50
50
4
8
13
50
38
27
1
27
27
*2
15
*2
15
*2
15
14
*2
15
13
13
23
50
50
11
13
50
50
50
50
6
50
7
50
50
50
50
50
50
50
13
50
13
47

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

3
3
3
3
3
3
3
3
3
3
3
3
2
3
3
0
3
3
1
3
3
0
0
0
0
0
0
0
3
3
0
0
3
3
3
3
1
3
3
3
3
3
3
2
3

3
3
3
3
3
3
3
3
3
3
3
3
2
3
3
0
3
3
1
3
3
0
0
0
0
0
0
0
0
3
3
0
0
3
3
3
3
1
3
3
3
3
3
3
2
3

Table 6a. Composition of sex and sexual maturity of common minke whales collected by the 2007 JARPN II survey.
Male

Sub-area

FemaleImm.

Mat.

Unknown

Total

Imm

Rest.

Preg.

Total

7

13

48

5

66

7

0

6

13

8

(16.5)
2(60.8)
10(6.3)
3(83.5)
15

(8.9)
0

(0.0)
0

(7.6)
0

9

(13.3)
1(66.7)
4(20.0)
0(100.0)
5

(0.0)
1

(0.0)
0

(16.7)(66.7)(0.0)(83.3)(16.7)(0.0)

Combined

Combined

Sex ratio

MaturityPregnancy(% males)Male

Femalerate*)

79

83.5

72.7

46.2

100.0

(16.5)
0(100.0)
15

100.0

66.7

0.0

0.0

(0.0)
0

(0.0)
1

(100.0)
6

83.3

80.0

0.0

0.0

(0.0)

(16.7)(100.0)
86.0

72.1

42.9

100.0

MaturityPregnancy

16

62

8

86

8

0

6

14

100

(16.0)(62.0)(8.0)(86.0)

(8.0)

(0.0)

(6.0)

(14.0)(100.0)*) Apparent pregnancy rate

Table 6b. Composition of sex and sexual maturity of sei whales collected by the 2007 JARPN II survey.
Sub-area
7
8
9Combined

Male

FemaleCombined

Imm.

Mat.

Total

Imm

Ovu

Rest.

Preg.

Lact.

Preg&Lact

Total

0
(0.0)
3

5
(83.3)
6

5(83.3)
91(16.7)
3

0
(0.0)
0

0
(0.0)
1

0
(0.0)
10

0
(0.0)
1

0
(0.0)
0

1
(16.7)
15

6(100.0)24(12.5)
18(25.7)
21(21.0)(25.0)
22(31.4)
33(33.0)(37.5)
40(57.1)
54(54.0)(12.5)
12(17.1)
16(16.0)

(0.0)
1
(1.4)
1
(1.0)

(4.2)
2
(2.9)
3
(3.0)

(41.7)
15(21.4)
25(25.0)

(4.2)
0
(0.0)
1
(1.0)

(0.0)
0
(0.0)
0
(0.0)

(62.5)
30(42.9)
46(46.0)(100.0)70(100.0)100(100.0)Sex ratio(% males)Male

Femalerate*)

83.3

100.0

0.0

-

37.5

66.7

80.0

83.3

57.1

55.0

60.0

83.3

54.0

61.1

65.2

83.3

*) Apparent pregnancy rate

Table 6c. Composition of sex and sexual maturity of Bryde’s whales collected by the 2007 JARPN II survey.
Sub-area
7
8
9Combined

Male

Female

Imm.

Mat.

Total

Imm

Ovu

Rest.

Preg.

Lact.

Preg&LactTotal

4(40.0)
6(20.0)
3(30.0)
13(26.0)

0(0.0)
8(26.7)
2(20.0)
10(20.0)

4(40.0)
14(46.7)
5(50.0)
23(46.0)

2(20.0)
2(6.7)
1(10.0)
5(10.0)

0
(0.0)
2
(6.7)
1
(10.0)
3(6.0)

2(20.0)
1
(3.3)
0
(0.0)
3
(6.0)

2
(20.0)
10(33.3)
3(30.0)
15(30.0)

0
(0.0)
1
(3.3)
0
(0.0)
1
(2.0)

0
(0.0)
0
(0.0)
0
(0.0)
0
(0.0)

6
(60.0)
16(53.3)
5(50.0)
27(54.0)*) Apparent pregnancy rate

16

Combined
10(100.0)30(100.0)10(100.0)50(100.0)MaturitySex ratio

Pregnancy(% males)Male

Femalerate*)

40.0

0.0

66.7

50.0

46.7

57.1

87.5

78.6

50.0

-

80.0

75.0

46.0

43.5

81.5

72.7

Table 7a. Statistics of body length (m) of common minke whale collected by the 2007 JARPN II survey.
Male

Sub area

Female

Mean

S.D.

Min.

Max.

n

Mean

S.D.

Min.

Max.

n

7

7.22

0.69

4.77

8.11

66

6.66

1.41

4.17

8.20

13

8

7.46

0.72

5.17

8.16

15

-

-

-

-

0

9

6.97

1.33

4.61

7.84

5

4.33

-

4.33

4.33

1

Combined

7.25

0.74

4.61

8.16

86

6.50

1.49

4.17

8.20

14

Table 7b. Statistics of body length (m) of sei whale collected by the 2007 JARPN II survey.
Male

Sub area

Female

Mean

S.D.

Min.

Max.

n

Mean

S.D.

Min.

Max.

n

7

13.69

0.54

13.09

14.37

5

11.83

-

11.83

11.83

1

8

13.25

0.57

12.66

14.41

9

13.97

1.12

11.46

15.19

15

9

13.05

0.96

11.18

14.85

40

13.84

1.11

10.71

15.51

30

Combined

13.14

0.88

11.18

14.85

54

13.84

1.13

10.71

15.51

46

Table 7c. Statistics of body length (m) of Bryde’s whale collected by the 2007 JARPN II survey.
Male

Sub area

Female

Mean

S.D.

Min.

Max.

n

Mean

S.D.

Min.

Max.

n

7

9.86

0.79

9.15

10.87

4

11.61

1.41

9.74

12.92

6

8

12.30

1.04

9.79

13.60

14

12.57

1.14

9.79

13.60

16

9

11.35

1.08

9.94

12.94

5

12.57

0.74

11.58

13.45

5

Combined

11.44

1.07

9.15

13.60

23

11.93

1.16

9.74

13.60

27

Table 7d. Statistics of body length (m) of sperm whale collected by the 2007 JARPN II survey.
Male

Sub area

Female

Mean

S.D.

Min.

Max.

n

Mean

S.D.

Min.

Max.

n

7

-

-

-

-

0

-

-

-

-

0

8

-

-

-

-

0

-

-

-

-

0

9

-

-

-

-

0

10.06

1.48

8.37

11.16

3

Combined

-

-

-

-

0

10.06

1.48

8.37

11.16

3

17

Table 8a. Prey species and stomach contents weight (1st. + 2nd. stomachs) found in stomach of common minke whales
sampled by the 2007 JARPN II surveys.
Common minke whale (Broken 4; Empty 6)
Prey species

N

Range of weigth (kg)

(Dominant)in the stomachs

9

7.7 - 105.6

Pacific saury11

10.3 - 77.0

Japanese anchovy63

7.6 - 196.2

Mackerels2

20.8 - 61.0

Walleye pollock

4

40.3 - 118.0

Boreal clubhook squid

1

48.9

Krill
Fish

Japanese sardine*-*: Minor prey species

Table 8b. Prey species and stomach contents weight (1st. + 2nd. stomachs) found in stomach of Sei whales sampled by
the 2007 JARPN II surveys.
Sei whale (Broken 3; Empty 26)
Prey species

Copepods

N

Range of weigth (kg)

(Dominant)in the stomachs

39

17.35 - 351.5

283.05 - 97.8

Pacific saury3

13.20 - 51.7

Japanese anchovy

11

24.35 - 321.7

Mackerels

16

22.85 - 885.3

Neocalanus spp.

Krill
Fish

Japanese sardine*-*: Minor prey species

Table 8c. Prey species and stomach contents weight (1st. + 2nd. stomachs) found in stomach of Bryde's whales sampled
by the 2007 JARPN II surveys.
Bryde's whale (Broken 1; Empty 19)
Prey species

N

Range of weigth (kg)

(Dominant)in the stomachs

1

348.0

Japanese anchovy

28

18.2 - 672.7

Mackerels

1

134.0

Krill
Fish

Japanese sardine*-*: Minor prey species

18

Table 9. Summary of biopsy skin sampling for blue, fin and humpback whales in the 2007 JARPN II survey.

WhalespeciesNumberTargeted

NumberNumberNumberofindividuals

of

of

of

shootshits

samplesexperiments

Effortsamplesample

per

per

(hr)

trial

hit

(A)

(B)

(C)

(D)

(E)

(F)

(E)/(C)(E)/(D)Blue whale

2

3

0

0

0

1:03

-

-

Fin whale

4

4

7

2

2

1:23

0.29

1.00

Humpback whale

2

3

11

1

1

2:01

0.09

1.00

Table 10. Summary of photo ID in the 2007 JARPN II survey.

WhalespeciesNumberTargetedofindividuals

experiments

Numberofphotos

(A)

(B)

(C)

Blue whale

8

10

93

Humpback whale

2

3

10

9N
7N

8N

7MI 7MO
7SI

7SO

8S

9S

Fig 1. Map showing the research area and strata of the JARPN II full-scale survey.

19

Fig. 2a. Track-line and primary search effort (thick line)covered by the dedicated sighting vessel (SV:KS2) andpositions of the sightings of common minke (circle), Bryde’s (diamond), sei (square) and sperm whales (triangle)
during survey of the 2007 JARPN II.

Fig. 2b. Track-line and primary search effort (thick line)covered by the dedicated sighting vessel (SV:KS2) andpositions of the sightings of blue (square), fin (triangle) and humpback (inverted triangle) whales during surveyof the 2007 JARPN II.

20

Fig. 3. Searching effort covered by the three sighting/sampling vessels (SSVs) during the 2007 JARPN II with theposition of sampled common minke (circle), Bryde’s (diamond), sei (square) and sperm (triangle) whales.
Three blocks 1, 2 and 3 show the cooperative survey on the prey species and whale sampling area.

21

Appendix A
Cruise report of the cetacean prey speices survey of JARPNII(offshore component) in 2007
HIROTO MURASE1, SHIROH YONEZAKI2, RYUICHI MATSUKURA3 AND SHIGEYUKI KAWAHARA2
1

The Institute of Cetacean Research, Toyomi-cho 4-5, Chuo-ku, Tokyo 104-0055, Japan
National Research Institute of Far Seas Fisheries, Orido 5-7-1, Shimizu-ku, Shizuoka 424-8633, Japan
3
Field Center for Northern Biosphere, Hokkaido University, Minato-cho 3-1-1, Hakodata, Hokkaido 041-8611, Japan
2

ABSTRCATA whale prey species survey was conducted concurrently with a whale sampling survey as a part of the offshore component of JARPNII in
2007. The primary objective of the concurrent study was estimation of prey selection of whales. Three survey blocks with zigzag tracklines
were set within the survey area of JARPNII. The survey was conducted from 4 July to 6 September. A trawler-type survey vessel, KaikoMaru (860 ton), equipped with the quantitative echo sounder dedicated to the prey survey. Kaiko-Maru also conducted cetacean sighing
survey while she steamed on the tracklines. The acoustic survey using a Simrad EK500 echo sounder with operating frequencies at 38 and
120 kHz was carried out to quantify pray abundance as well as to elucidate the distribution patterns. Species compositions of acousticalbackscatterings were identified using midwater trawl and plankton nets. In addition, trawls were towed at predetermined stations
independently from the acoustic survey. IKMT and NORPAC were used to collect zooplanktons. Midwater trawl, IKMT and NORPAC
were towed at 66, 12 and 62 stations, respectively. Oceanographic observations were conducted using CTD and XCTD at 57 and 16
stations respectively. Total surveyed distance of cetacean sighting survey was 1741.6 n.miles. Primary sightings of sei and Bryde’s whales
were 42 groups/69 individuals and 55 groups/105 individuals, respectively.

INTRODUCTION
The Japanese Whale Research Program under Special Permit in the North Pacific (JARPN) was conducted between
1994 and 1999. The main objective was to clarify the stock structure of common minke whales (Balaenoptera
acutorostrata) in the western North Pacific. As it proved that minke whales feed on a good deal of fisheries resources
such as Japanese anchovy (Engraulis japonicus) and Pacific saury (Cololabis saira) (Tamura and Fujise, 2002), thefeeding ecology was added in 1996 as a feasibility study. At the JARPN review meeting held in February 2000, theworkshop agreed that the sampling regime must be designed to allow for a more quantitative estimation of temporal andgeographical variation in diet, and recommended that acoustic and trawl surveys should be conducted cooperatively
with whale survey (IWC, 2001). In response to the recommendation, the government of Japan submitted the Research
Plan for Cetacean Studies in the Western North Pacific under Special Permit (JARPN II) (Feasibility Study Plan for2000 and 2001) to the 52nd IWC/SC (Government of Japan, 2000) The overall goal of JARPN II is to contribute to theconservation and sustainable use of marine living resources including whales in the western North Pacific, especiallywithin Japan’s EEZ. The priority in this second phase is on feeding ecology, involving the studies on prey consumption
by cetaceans, prey selection of cetaceans and ecosystem model. After the success in two feasibility studies, the study
was expanded to full scale in 2002 (Government of Japan 2002). Sei whale (Balaenoptera borealis) was added as target
cetacean species in addition to minke, Bryde’s (Balaenoptera edeni) and sperm (Physeter macrocephalus) whales in thefull scale study. The full scale study in 2007 was conducted in Sub-areas 7, 8 and 9, off the coast of eastern Honsyu,
Japan from July to September. The whale survey is conducted to collect diet data as well as other biological parametersof sei, Bryde’s, minke, and sperm whales, whereas the prey survey was conducted to collect data on prey species offormer three baleen whale species. This paper presented the cruise report of the prey species survey as a part of offshore
component of JARPNII in 2007.
MATERIALS AND METHOD
The area of the cooperative whale and prey surveys was in Sub-areas 7, 8 and 9 off the coast of eastern Honsyu, Japan(Fig. 1). Within the survey area, three blocks, Block 1, 2 and 3 were set considering the oceanographic conditions suchas positions of fronts and water masses as well as anticipated distribution pattern of the target whale species. In eachblock, a zigzag track line was set independently from whale survey. Waypoints were listed in Table 1. The research
vessel, Kaiko-maru (KK1, 860 GT), departed Shiogama port on 4 July, 2007 and returned Kushiro port on 6 September,2007. Details of itinerary were shown in Table 2. Prey distribution and abundance surveys using the quantitative echosounder, midwater trawl, Isaacs Kidd Midwater Trawl (IKMT) and NORPAC were conducted KK1. In addition to theprey survey, KK1 conducted cetacean sighting survey. During the daytime, KK1 steamed at about 10 knots along the22tracklines to conduct cetacean sighting and acoustic survey. Research hour was from an hour after sunrise to an hour
before sunset while the maximum research hours were set at 13 hours. Generally, the survey started at 5:00 and end at
18:00 at local time.
A quantitative echo sounder (Simrad EK500) with operating frequencies at 38 and 120 kHz was used on board
KK1 to acquire acoustic data. The transducers were hull-mounted at the depth of 4.3m from the surface. Calibrations
were carried out at off the coast of Shiogama on 27 June , 2007 using the copper sphere technique described in the
EK500 manual (Simrad, 1997). Acoustic data were recorded while the KK1 steamed on the tracklines. Acoustic data
were also recorded during net samplings.
The midwater trawl net was 86.3 m long with a mouth opening of ca. 900 m2 and a 6.0 m cod end with a 17.5 x
17.5 mm mesh inner. The sampling depth and, the height and width of the mouth of the net were monitored with Simrad
PI32 Catch Monitoring System. Towing speed of the trawl net was 4-5 knot. Surface and midwater trawl was towed at
predetermined and target trawl stations. Surface trawls were conducted using the midwater trawl net with the floats
attached the bridle so that the trawl could be towed at the surface. Surface trawl was designed for collecting mainly
Pacific saury. Target trawls were conducted to identify the species and size compositions of biological backscattering
detected by the quantitative echo sounder. Another type of trawling was also conducted at predetermined stations ineach block. The purpose of the predetermined trawls was to estimate the abundance and distribution patterns of
cephalopods and neustnic organisms such as Pacific saury that are difficult to detect by the echo sounder. Two different
depth layers were sampled at predetermined trawl stations; 0-30m (surface) and 0-100m (midwater). Midwater
predetermined trawl was towed for 10 minutes at each depth layer, 0-30 m, 30-60 m, and 60-100 m whereas surface
predetermined trawl was towed for 30 minutes. All samples were identified to the species as much as possible and wet
weight of each species was measured aboard the ship. For the major species, length of 100 individuals was measured to
examine their size composition. A part of samples were frozen for further analysis in the laboratory. In addition to the
trawl net, IKMT was used to identify the species and size compositions of macro and mesozooplanktons detected by thequantitative echo sounder. Mouth opening of the IKMT was about 3.7x3.1 m and mesh size of cod end was 1.9 mm. The
samples were preserved in 10 % formalin for species identification at the laboratory. A small plankton net, the North
Pacific standard net (NORPAC), equipped with flow meter was towed at most of trawl stations to estimate abundance ofcopepods. The mouth opening and mesh size of NORPAC are 45cm and 0.33mm, respectively. NORPAC was towed
from 150m to surface but it was towed various depth range in some cases to identify species compositions of acousticalbackscattering.
Water temperature and salinity profiles at sampling stations were recorded by Conductivity-Temperature-Depth
profiler (CTD, SBE-19 (KS2), Seabird, USA) and expendable CTD (XCTD, Tsurumi Seiki Co., Japan). CTD and
XCTD data were recorded from surface to 500m and from surface to 1000m, respectively. CTD was mainly used torecord oceanographic data while XCTD was used when the time of deployment was limited.
Cetacean sighting survey was conducted by KK1 while she steamed on the tracklines. Primary observers wereallocated to the top barrel (3 observers) and the upper bridge. (2 observers). Sighting survey was conducted in passing
mode though abeam closing was conducted if the sightings were baleen whales but the species was uncertain. Abeamclosing was conducted on sightings at a distance of 2n.miles perpendicular to trackline.
To calculate theoretical target strength (TS), body-density and sound speed through body of two copepods,
Neocalanus cristatus and N. plumchrus, were measured onboard KK1. Body-density and sound speed are crucial
parameters in theoretical TS models. Copepods were sampled either IKMT or NORPAC. Body-mass density wasmeasured using a density-bottle method. Body-mass density was determined by evaluating the buoyancy of eachcopepod sample via a series of 500ml plastic sample containers containing seawater-glycerol solution of different
density. The speed of sound through the copepod body was estimated by a time-average approach. The principle of thetime-average approach is based on the measurement of the time-of-flight of acoustic pulses through a uniform mixtureof water and marine organisms. Ratio between speed of sound through seawater and copepod body was estimated using
this method.
RESULTS AND DISCUSSION
Most of tracklines were surveyed by the quantitative echo sounder. Predetermined surface and midwater trawling was
conducted at 32 and 28 stations, respectively. Target trawling was conducted at 6 stations. Positions of surface andmidwater trawling were shown in Fig. 2. Summary of the results of trawling was shown in Table 3. Japanese anchovy
and Pacific saury were dominant among sampled species. IKMT was towed at 12 stations (Table 4, Fig.3,). NORPAC
was towed at 62 stations (Table 5, Fig. 4). CTD and XCTD casts were carried out 57 and 16 stations, respectively.
Surveyed distances of cetacean sighting survey in Blocks 1, 2, and 3 were 450.0, 761.1 and 530.5 n.miles, respectively.
About 50 % of planned surveyed distance was surveyed in each Block. Primary sightings of sei and Bryde’s whales
were 42 groups/69 individuals and 55 groups/105 individuals, respectively. Body-density and sound speed through body23

of copepods were measured at 3 and 4 stations, respectively. All recorded data will be used to estimate the preyselection of baleen whales (e.g. Murase et al., 2007).
ACKNOWLEDGMENT
Authors express gratitude to Captain Yoshinori Shinyashiki and the crews on Kaiko-Maru for their dedication tocollecting data. We also thank members of the Institute of Cetacean Research and National Research Institute of Far
Seas Fisheries who support this project.
REFERENCES
Government of Japan. 2002. Research plan for cetacean studies in the western North Pacific under Special Permit (JARPN II). Paper SC/54/O2
submitted to the 54th IWC Scientific Committee Meeting.
International Whaling Commission. 2001. Report of the workshop to review the Japanese whale research programme under special permit for North
Pacific minke whales. J. Cetacean Res. Manage. (Suppl.) 3:377-413.
Murase, H., Tamura, T., Kiwada, H., Fujise, Y., Watanabe, H., Ohizumi, H., Yonezaki, S., Okamura, H. and Kawahara, S. 2007. Prey selection ofcommon minke and Bryde’s whales in the western North Pacific in 2000 and 2001. Fish. Oceanog. 16:186-201.
Simrad. 1997. Simrad EK500 Scientific Echo Sounder Operation Manual P2170G. Simrad AS Horten, Norway.
Tamura, T. and Fujise, Y. 2002. Geographical and seasonal changes of the prey species of minke whale in the Northwestern Pacific. ICES J. Mar. Sci.
59:516-528.

24Appendix B
Oceanographic conditions in the survey area of offshore
compoent of JARPN II in the western North Pacific from Julyto September 2007
DENZO INAGAKE*, MAKOTO OKAZAKI*, HIROTO MURASE** and SHIROH YONEZAKI****National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648,
Japan**The Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo, Tokyo, 104-0055, Japan***

National Research Institute of Far Seas Fisheries, 5-7-1, Orido, Shimizu, Shizuoka, Shizuoka, 424-8633, Japan

Contact e-mail: ina@affrc.go.jp
ABSTRACTA prey species survey was conducted in July-September 2007 using Kaiko-Maru as a part of offshore component of JARPN
II. The survey covered from subarctic area to the adjacent area of the subtropical area around 150ﾟE, 157ﾟE and 165ﾟE wherecommon minke, Bryde’s and sei whales were found. During the survey, oceanographic observation with CTD and XCTD wasmade to make clear the environment of the prey. The survey area was located between the Kuroshio Extension and theSubarctic Front, as the water mass was characterized by the subarctic water, subtropical water and mixed water.

Introduction
A prey species survey was conducted in the offshore three blocks (around 150ﾟE, 157ﾟE and 165ﾟE) of the western
North Pacific in July-September 2007 using Kaiko-Maru in cooperation with the sampling survey by Nisshin-Maru(Fig. 1). Common minke, Bryde’s and sei whales were found in the survey blocks.
There are a lot of water masses and fronts in the western North Pacific. The Oyashio flows southwestward along
the Kuril Islands and turns eastward from the northern coast of Japan. The Kuroshio flows northward from the tropicalarea to Tohoku area east of Japan, and reaches near the Oyashio front. The Kuroshio turns eastward from the northerncoast of Japan, and the strong eastward flow is called the Kuroshio Extension. Both major current, the Kuroshio
Extension and the Oyashio, form Kuroshio-Oyashio Inter-frontal Zone. Water masses originated in the Kuroshio andthe Oyashio are mixed each other in this zone and form new water masses.
In the high sea of the North Pacific Ocean, there are Subarctic Front (temperature front defined by 4ﾟC) and theSubarctic Boundary (salinity front defined by 34.0psu) with a weak eastward flow. The Subarctic Front is south limit of
the subarctic water and the Subarctic Boundary is north limit of the tropical water. The area between these fronts iscalled the Transition Domain (Favorite et al. 1976).
Each water mass in the western North Pacific has its own ecosystem, like a Kuroshio ecosystem, an Oyashio
ecosystem, warm-core ring ecosystem, etc. So, we must make clear the oceanographic condition around whale’s preyto build up a marine ecosystem model in this area. In this paper, distributions of water masses and fronts in the survey
area will be described to make clear the environment of the prey of sei, Bryde’s and common minke whales.
Methods
Hydrographic observations with a conductivity-temperature-depth profiler (CTD; SBE 19) and expendable CTDs werecarried out from July 7 to September 4 in the Kuroshio-Oyashio Inter-frontal Zone using Kaiko-Maru. Salinity
correction for CTD data was not done using water sampling data.
Oceanic fronts and water masses are usually detected by subsurface temperature map, because they are obscure insea surface temperature distributions from summer to fall seasons and the Oyashio water spreads into the subsurface
layer (Table 1). The Kuroshio Extension is defined by the 14ﾟC isotherm at the depth of 200m (Kawai , 1969). The
warm water spread from Kuroshio Extension is defied by temperature more than 10ﾟC at the depth of 100 m. The first33

and the second Oyashio Intrusions are defined by temperature lass than 5ﾟC at the depth of 100 m (Murakami, 1994).
Subarctic front and the Subarctic Boundary is defined by 4ﾟC temperature front and 34.0psu salinity front, respectively(Favorite et al. 1976). We use these indices to know the distribution of water mass in the survey area.
Oceanographic conditions in the survey area
The upper panel in Fig. 2 shows the Temperature-Salinity diagrams in the western block. There is typical Kuroshio
water characterized by high salinity profile around 34.5 psu, especially in warm upper layer (over 10 ﾟ C). Oyashio
water characterized by cold profile less than 5 ﾟ C is shown in lower part of Fig. 2. The mixed water is distributed
between both of the Oyashio and the Kuroshio waters.
Figure 3 shows temperature and salinity maps at the depth of 100 m and 200 m. The cold water less than 5ﾟC at
100 m depth was distributed in a northern part of the survey area. The Subarctic Front (defined by 4ﾟC isotherm) was
observed from 41ﾟN, 150ﾟE to 44ﾟ-30’ N, 165ﾟE in Fig. 3 (left upper panel). In 100 m and 200 m salinity maps (lower
panels of Fig. 3), a salinity front around 34.0 psu is shown along 40ﾟN line in the middle part of the survey area. The
warmest temperature at the 200 m depth is observed at southwestern part of this area, and 14ﾟC isotherm, which is anindex of the Kuroshio Extension, is observed only this area.
Figure 4 shows the vertical sections of temperature, salinity and density anomaly along the cruise track of KaikoMaru between 156ﾟE-158ﾟE, which is a zigzag line. The Subarctic Water colder than 4ﾟC is observed in the northernarea, north of 43ﾟN, and 4ﾟC isotherm lies vertically from 50 m depth to 300 m depth around 43ﾟN. It indicates that
there is the subarctic front around 43ﾟN in this section. A surface low salinity water less than 33.5psu is also observedin the northern area, north of 43ﾟN. The high-salinity water greater than 34 psu, which is the index of the subarctic
boundary, is shown at a surface layer in the southern area, south of 40ﾟN. Around 40ﾟN in this section, isotherms
between 5ﾟC and 10ﾟC lie vertically and show an existence of a temperature front. At the southern part of this section,
bowl shape isotherms and isohalines were observed around 36ﾟN with subsurface mixed layer, which suggests that
there is the Kuroshio warm-core ring. The Kuroshio Extension is not appeared in this section.
Figure 5 shows temperature, salinity and density anomaly sections between 164ﾟE-166ﾟE. The Subarctic Water isobserved in the northern area, north of 41ﾟ30’N where is 4ﾟC isotherm (index of the subarctic front) running verticallyfrom 200 m to 500 m depth. The high-salinity water greater than 34 psu (index of the subarctic boundary) is shown at asurface layer in the southern area, south of 39ﾟ30’N. At the southern part of this section, bowl shape isotherms andisohalines were observed around 36ﾟN with subsurface mixed layer similar with Fig. 4, which also suggests that there is
the Kuroshio warm-core ring. Because isotherms around 35ﾟN are running vertically and 14ﾟC isotherm cross near thedepth of 200 m, the Kuroshio Extension is nearby 35ﾟN in this section.
Figure 6 shows temperature, salinity and density anomaly sections between 149ﾟE-151ﾟE. The Subarctic Water(colder than 4ﾟC) and 4ﾟC isotherm (index of the subarctic front) is observed around 40ﾟ30’N. The salinity front
around 34 psu (index of the subarctic boundary) is also shown around 40ﾟ30’N nearby the subarctic front. At thesouthern part of this section, bowl shape isotherms and isohalines were observed around 36ﾟ30’N with subsurface
mixed layer, which also suggests that there is the Kuroshio warm-core ring as Fig. 4 and 5. As there is high-salinity
water over 34.8 psu is observed around 35ﾟ30’N, isotherms around 35ﾟ45’N are running vertically and 14ﾟC isotherm
cross at the depth of 200 m around 35ﾟ45’N, the Kuroshio Extension flows at 35ﾟ45’N in this section.
These figures show that the survey area is located between the Kuroshio Extension and the Subarctic Front.

REFERENCES
Favorite, F., A. J. Dodimead and K. Nasu (1976): Oceanography of the subarctic Pacific region, 1960-71. Bull.
International North Pacific Fisheries Commission, 33, 187 pp.
Kawai, H. (1969): Statistical estimation of isotherms indicative of the Kuroshio axis, Deep-Sea Res., Suppl. to 16, 109115.
Murakami, M. (1994): On long-term variations in hydrographic conditions in the Tohoku area, Bull. Tohoku Natl. Fish.
Res. Inst., No. 56, 47-56 (in Japanese with English abstract).

34

Table 1. Extraction method from temperature map to determine the position of each water mass.

Target characteristics

Extraction method

Kuroshio Extension Axis

14℃ isotherm at 200 m

Warm-core ringTemperature front at 200 m

Oyashio front

5 ℃ isotherm at 100 m

Oyashio water

Area with T<5 ℃ at 100 m

Cold water

Area with 5℃<T<10 ℃ at 100 m

Warm water

Area with T>10 ℃ at 100 m and T<14 ℃ at 200 m

Subarctic Boundary

Salinity front defined by 34.0 psu

Subarctic Front

Temperature front defined by 4℃

Fig. 1. Station map observed by Kaiko-Maru in July 7 to 26 (Leg 1: middle panel), July 28 to August 21 (Leg 2: rightpanel) and August 24 to September 4 (Leg 3: left panel), 2007.

35

Fig. 2. Temperature-Salinity diagrams using CTD station data observed by Kaiko-Maru in July 7 to September 4, 2007.
Each thin line in this figure denotes a density line of sigma-t.

36

Fig. 3. Temperature (upper panels) and salinity (lower panels) maps at the depth of 100 m (left panels) and 200 m(right panels) observed by Kaiko-Maru in July 7 to September 4, 2007.

37

Fig. 4. Vertical sections of temperature (upper panel), salinity (middle panel) and density anomaly (lower panel)observed by Kaiko-Maru in July 7 to 26 along the cruise track of Leg 1 (middle part of Kaiko-Maru surveyarea).

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Fig. 5. Vertical sections of temperature (upper panel), salinity (middle panel) and density anomaly (lower panel)observed by Kaiko-Maru in July 28 to August 21 along the cruise track of Leg 2 (western part of Kaiko-Marusurvey area).

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Fig. 6. Vertical sections of temperature (upper panel), salinity (middle panel) and density anomaly (lower panel)observed by Kaiko-Maru in July 28 to August 21 along the cruise track of Leg 2 (western part of Kaiko-Marusurvey area).

40