SC/60/O6

SC/60/O6

Cruise report of the second phase of the Japanese Whale Research
Program under Special Permit in the Western North Pacific (JARPNII) in 2007 - Coastal component off Sanriku.
TAKEHARU BANDO1, HIDEHIRO KATO2, TOSHIYA KISHIRO3, MUTSUO GOTO1, GENTA YASUNAGA1,TERUO SAITO1, SHIGEO TABATA1, YUKA MORITA1, RYOSUKE OKAMOTO2, HIKARI MAEDA2, MIHOINAGAKI2, SYOKA NAGATSUKA2, TADASHI EBISUI1, KAZUYOSHI NAKAI1, AKIRA MATSUMOTO2,AKIHIRO GOKITA2, AND SHIGEYUKI KAWAHARA3
Contact e-mail:bando@cetacean.jp
The Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan.
Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-0075, Japan
3
National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa-ku, Yokohama,
Kanagawa, 236-8648, Japan1
2

ABSTRACTThe fourth survey of the JARPN II coastal component was conducted from 16 April to 31 May in2007, off Sanriku district, northeastern Japan (middle part of the sub-area 7), using four small-typewhaling catcher boats and one echo sounder trawl survey vessel. In the survey, sampling of common
minke whales was conducted in coastal waters mainly within 30 nautical miles from Ayukawa port
in the Sanriku district, and all animals collected were landed on the JARPN II research station
established by the port for biological examination. During the survey, a total of 7793.7 nautical miles(716.5 hours) was surveyed for whale sampling, the 166 schools (171 individuals) of common minke
whales were detected, and 57 animals were caught. Average body length of the animals was 6.25m(SD: 1.30, n=21) for males and 5.67m (SD: 1.16, n=36) for females. Dominant prey species foundfrom forestomach of animals were Japanese sand lance (Ammodytes personatus) and Japanese
anchovy (Engraulis japonicus) throughout survey period. Krill (Euphausia pacifica) was observed
from only one individual. Seasonal pattern of the dominant prey species through the survey period
was different from the past three coastal surveys off Sanriku. These results indicate that feeding
habit of common minke whales in coastal waters off Sanriku changes year by year.
KEYWORDS: COMMON MINKE WHALE; NORTH PACIFIC; COASTAL WATERS OF JAPAN;
FOOD/PREY; ECOSYSTEM; SCIENTIFIC PERMITS.

INTRODUCTION
After the two-year feasibility study in 2000-2001, the full-scale survey of the second phase of theJapanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II)
was started in 2002. The purpose of the program is, i) to evaluate the feeding ecology and ecosystem
studies, involving prey consumption by cetaceans, prey preferences of cetaceans and ecosystem
studies, ii) to monitor environmental pollutants in cetaceans and the marine ecosystem and iii) to
elucidate the stock structure of whales (Government of Japan, 2002a).
The JARPN (1994-1999) and the JARPN II feasibility studies (2000-2001) revealed that
common minke whales are widely distributed from offshore waters to coastal waters and feed on
various prey species such as Japanese anchovy, Pacific saury, and walleye pollock (Government ofJapan, 2002b; Tamura and Fujise, 2002). The coastal waters of Japan are also very important fishingground. Thus, it was thought that the coastal waters are also very important research area for the
full-scale JARPN II program. However, the Nisshin Maru research vessels can not be operated in thenear shore areas, because of their movement restrictions from shallow water depth, and many fishinggears and boats. Furthermore, the vessels can not work from late autumn to early spring because of
their practical availability. In order to cover the temporal and spatial gap of the vessels, sampling of1

SC/60/O6

common minke whales in the coastal waters using small-type whaling catcher boats was planned.
In the original JARPN II plan, the coastal component was presented as the two-year feasibility
study to examine the logistic aspects of the methodology (Government of Japan, 2002a). First
feasibility survey was carried out in the coastal waters off Kushiro in fall 2002 (Kishiro, et al., 2003)
and then the second feasibility survey was conducted in the coastal waters off Sanriku district inspring 2003 (Yoshida, et al., 2004). In each of the surveys, 50 common minke whales were caught.
From detailed examination of logistic aspects in the surveys, it was concluded that no substantial
problem occurred and that the coastal survey could be continued as a component of the JARPN II
using same kind of vessels (small-type whaling catcher boats) and methodology (Government ofJapan, 2004b, Kato, et al., 2004). However, re-calculation of required sample size from the survey
data suggested that the size should be modified to be at least 60 individuals in each area/season(Tamura, et al., 2004), and from the possible geographical and/or temporal variations of prey
consumption of the whales, the coastal surveys thought to be needed on a yearly bases in each local
area (Government of Japan, 2004a). The revised survey off Sanriku was carried out in spring 2005
(Yoshida, et al., 2006) and 2006 (Goto, et al., 2007).
In the present paper, we show results of the fourth survey carried out in coastal waters off theSanriku district, Japan, from 16 April to 31 May in 2007. This survey was authorized by theGovernment of Japan in compliance with Article VIII of the International Convention for the
Regulation of Whaling. The Institute of Cetacean Research (ICR) planned and conducted the survey
cooperated with National Research Institute of Far Seas Fisheries, Tokyo University of Marine
Science and Technology and Miyagi Prefecture Fisheries Research and Development Center.
MATERIALS AND METHODS
Research area
Research area was set in the same waters where the previous JARPN II coastal surveys off theSanriku district were conducted (Yoshida et. al, 2004; 2006; Goto et al., 2007). The district occupies
northeastern part of the Japanese main island, Honshu (see, Fig. 1). In coastal waters off the Sanriku
district, common minke whales were taken by the past land-based coastal whaling (Miyashita andHatanaka, 1997). The waters have been also very important fishing grounds. So, the waters were
thought to be suitable for the research area of the JARPN II, and thus the coastal surveys wereconducted in this area. The present research area was also set in the same waters: within 50 nautical
miles (mainly 30 n. miles) from the Ayukawa port in the Sanriku district (Fig. 1). The survey area isincluded in the middle part of the sub-area 7 established by the IWC (1994).
Research vessels and station
Whale sampling survey
Four small-type whaling catcher boats were used as sampling vessels: Taisho Maru No. 28(hereinafter referred as 28T; 47.3GT), Koei Maru No. 75 (75K; 46.0GT), Katsu Maru No.7 (7K;
32.0GT), and Sumitomo Maru No.31 (31S; 32.0GT). The whale sampling survey was conducted in aperiod from 16 April to 31 May, 2007. All the animals sampled were landed on the JARPN II
research station established by the Ayukawa port for biological examination.
Prey species survey
The Takuyo Maru (TAK, 120.0GT), the trawler-type research vessel, conducted the prey species
survey in research area set off northeast coast of Honshu from 9 to 27 April. The distribution andabundance of the prey species were investigated with the quantitative echo sounder (EK 500 and ER60) on board TAK. Acoustic data were acquired with operating frequency at 38, 120 and 200 kHz.
Species/size compositions of echo signs were identified by targeting mid-water trawling. Detail ofthe prey species surveys are shown in Appendix 1. The research vessel TAK also carried out
oceanographic observation using CTD and EPCS. Detail of the oceanographic observation are
shown in Appendix 2.
Sighting and sampling methods2

SC/60/O6

Sighting and sampling methods by whale sampling vessels were almost same in the past three
coastal surveys conducted off Ayukawa in 2003, 2005 and 2006 (Yoshida et al.: 2004; 2006, Goto etal.: 2007). The research head office was placed in the research station and operated the sampling
vessels during the survey. In order to avoid concentration of sampling effort, research area wasdivided into 3 small areas. The office determined searching area and routes of sampling vessels
everyday considering weather conditions, whale distribution and information on coastal fisheries.
A researcher was on board each of four sampling vessels, and recorded sighting and sampling
information, e.g., coordinates and time of common minke whales sighting and sampling made,weather conditions, and vessel activity. Sighting information was also recorded for other baleen
whales and sperm whales. Searching activity was conducted from top barrel and upper bridge bycrews and researchers. All common minke whales sighted were targeted for sampling, except
cow-calf pair. When a school consisted of plural animals, an individual was selected randomly fromthe school and then caught. Once the vessel sampled a whale, she returned to the Ayukawa port assoon as possible, to transport the animal to the research station. During the return cruise, even if
common minke whales were sighted, sampling was not conducted. At the port, animals taken were
lift up from the vessels by a crane, using a wire net and then carried to the station by a freight trailer.
At that time, body weight was measured with the truck scale.
Biological research for common minke whales collected
All the animals collected were examined biologically by researchers at the research station. Research
items of the biological examination are summarized in Table 4. These items are related to studies on
feeding ecology, stock structure, life history and pollutions.
RESULTS
Searching effort made by sampling vessels
Cruise tracks made by sampling vessels (28T, 75K, 7K and 31S) during the present survey are
shown in Fig. 2. The sampling vessels tried to cover research areas widely within 30 n. miles from
Ayukawa port. In offshore waters, however, searching activity was low because of changeable
weather condition and bigger waves for small sampling vessels. Consequently, searching effort wasconcentrated in Sendai Bay. Searching distance and time made by four sampling vessels are listed inTable 1. Here, searching distance and time are defined as distance and time recorded under searchingactivity conducted from top barrel of vessels. Total searching distance and time made by the four
vessels were 7793.7 n. miles and 716.5 hours, respectively.
Common minke whale sightings made by sampling vessels
Sighting positions of common minke whale schools made by the sampling vessels are shown in Fig.
3. All of common minke whale sightings were recorded in middle part of Sendai Bay. As shown in
Table 2, a total of 166 schools (171 individuals) of common minke whales was sighted. These were
149 primary sightings (153 animals) and 17 secondary sightings (18 animals). Of 166 schoolssighted, only 5 schools consisted of 2 individuals and others were solitary animals. No cow-calfpairs nor other large whale species were sighted.
Table 3 shows density index (SPUE: number of primary school sightings per one hour searching;
DI: number of primary school sightings per 100 n. miles searching) of common minke whales
recorded by the sampling vessels. Both SPUE and DI are highest during first half of May through theresearch period.
Sampling of common minke whales
A total of 57 common minke whales were taken for biological examination. In the sampling process,one common minke whale was struck and lost. Sighting positions of sampled individuals are shownin Fig. 4.
Sex ratio, body length and weight of animals caught
Research items of biological examination are summarized in Table 4, with number of data and3

SC/60/O6

samples obtained. The collected 57 animals consisted of 21 males and 36 females. Sex ratio of males
to all animals was 0.37.
Average body length was 6.25m (max=8.06, min=4.24, SD: 1.30) for males and 5.67m(max=8.80, min=4.05, SD=1.16) for females, respectively (Table 5). Frequency of body length ofcommon minke whale by sex was shown in Fig. 5. Average body weight was 3.08 tons (max=5.50,
min=1.05, SD=1.50) for males and 2.52 tons (max=8.35, min=0.91, SD=1.63) for females (Table 6).
Average body length of female was gradually increased during survey period from 5.46m in the first
period to 5.91m in third period but marked difference was not detected for male.
Composition of sexual maturity of animals collected is listed in Table 7. In males, 9 of 20
animals were sexually mature (45.0%), and 7 of 36 females attained sexual maturity (19.4%). Six
from seven mature females were pregnant and one female was pregnant and lactating
simultaneously.
Prey species of common minke whale found from forestomach
Following the same methods used in the JARPN II feasibility survey conducted in 2001 (Fujise, etal., 2002), stomach contents were weighted to the nearest 0.1 kg, by each of four chamber, in bothcases of including and excluding liquid contents. Then, small sample of forestomach contents wascollected and frozen for laboratory analysis.
Forestomach contents found from common minke whales during the present survey are listed inTable 8. Dominant prey species were adult sand lance (Ammodytes personatus) (69.4%, 34 from 49
animals) and Japanese anchovy (40.8%, 20 from 49 animals). Sand lance and Japanese anchovy
were detected throughout the survey period. Krill (Euphausia pacifica) was recorded from only one
animal in the third period.
The maximum weight of forestomach contents including liquid was 65.2kg, of which consisted
Japanese anchovy. This individual was female with body length of 7.91m and body weight of 4.93
tons. Forestomach contents weight was 1.32% of her body weight.
By-products of the whales
After biological examination, all the animals were processed according to the International
Convention for Regulation of Whaling, Article VIII. Total weight of productions including meat andblubber was 78.3 tons.
DISCUSSION
The present survey was the fourth coastal survey carried out in coastal waters off Sanriku district.
During the survey period, low atmospheric pressure often disturbed the research activities.
Furthermore, changeable weather condition and bigger waves obstructed searching activities ofsampling vessels in offshore waters. Nevertheless, almost all of planned sample size was collected in
Sendai Bay, where water depth is less than 100m and Nisshin Maru research vessels can not operate.
Dominant prey species of common minke whale found from forestomach were Japanese sandlance and Japanese anchovy throughout survey period. Krill was found in only one individual. Thisseasonal pattern of dominant prey species was different from past three coastal surveys off Sanriku.
In the 2003 coastal survey off Sanriku, dominant species changed with time (Yoshida, et al. 2004):
krill were dominant in the first period (74.8%), then the occurrence frequency reduced with time,and in the third period sand lance were found most frequently (92.2%). On the other hand, dominant
prey species was Japanese sand lance (45.0%) in the 2005 coastal survey off Sanriku. Sand lance
was detected throughout the survey. Krill and Japanese anchovy were also found, but their frequency
was much lower (6.7%) (Yoshida et al., 2006). In 2006, sand lance and Japanese anchovy were
dominant prey species but Japanese anchovy appeared only in later period of the survey. These
results indicate that feeding habit of common minke whales in coastal waters off Sanriku changes
year by year, probably from environmental factors, e.g., oceanographic conditions or prey species4SC/60/O6

distribution.
Sea surface water temperature during last winter was higher than ordinal years and some Japanese
anchovy overwintered in the bottom of Sendai Bay (Nagashima, personal communication). Highsurface water temperature, which was 1-2℃ higher than last year, was also recorded by prey species
survey conducted from 9 to 27 April and Japanese anchovy was detected by eco-sounder throughout
survey period (see Appendix 1). This suggests that diet composition of common minke whales in the
Sendai Bay reflects abundance of prey species. These results will contribute to elucidate prey
preference of common minke whales.
From the present survey, we could obtain valuable information including feeding ecology ofminke whales. To evaluate more precise values on food consumption of minke whales and to obtain
more information on interaction between the whales and coastal fisheries, continuation of studies areneeded.
ACKNOWLEDGMENTS
We acknowledge Mr. Hideki Moronuki, the Fisheries Agency of Japan, for his guidance andimplementation to the research. Crewmen of research vessels, staffs of the research station in
Ayukawa, and the Japan small-type whaling association helped us. We also thank all the members ofthe municipal office of Ishinomaki, the Ojika fisheries cooperative association, and Miyagi
prefectures office, for their kind assistance.
REFERENCES
Fujise, Y., Tamura, T., Bando, T., Watanabe, H., Kiwada, H., Otani, S., Kanda, N., Yasunaga, G.,
Mogoe, T., Konishi, K., Inamori, M., Shigemune, H. and Tohyama, D. 2002. Cruise report of thefeasibility study of the Japanese Whale Research Program under Special Permit in the western
North Pacific-Phase II (JARPN II) in 2001. Paper SC/54/O16 submitted to the 54th IWC ScientificCommittee, 51pp.
Goto, M., Kato, H., Zenitani, R., Yoshida, H., Saito, T., Tabata, S., Morita, Y., Sato, H., Okamoto,R., Maeda, H., Odagawa, A., Ebisui, T., Nakai, K., Matsumoto, A., Fujimori, S., Nishiwaki, S.
and Kawahara, S. 2007. Cruise report of the second phase of the Japanese Whale Research
Program under Special Permit in the Western North Pacific (JARPN II) in 2006- Coastal
component off Sanriku. Paper SC/59/O6 submitted to the 59th IWC scientific Committee, 34pp.
Government of Japan, 2002a. 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.
Government of Japan (Fujise, Y., Kawahara, S., Pastene, L.A. and Hatanaka, H. eds.), 2002b. Reportof 2000 and 2001 feasibility study of the Japanese Whale Research Program under Special Permit
in the western North Pacific-Phase II (JARPN II). Paper SC/54/O17 submitted to the 54th IWC
Scientific Committee, 202pp.
Government of Japan, 2004a. Revised research plan for cetacean studies in the western North Pacificunder special permit (JARPN II). Paper SC/56/O1 submitted to the 56th IWC Scientific Committee,
14pp.
Government of Japan (Fujise, Y., Tamura, T., Kato, H. and Kawahara, S. eds.), 2004b. Someconsiderations of the feasibility components of the JARPN II research plan. Paper SC/56/O2
submitted to the 56th IWC Scientific Committee, 36pp.
International Whaling Commission. 1994. Report of the Scientific Committee, Annex G. Report of
the Working Group on North Pacific Minke Whale management trials. Rep. int. Whal. Commn
44:120-44.
Kato, H., Kishiro, T., Yoshida, H. and Kawahara, S. 2004. Feasibility of coastal surveys in the
JARPN II, from the viewpoint of logistics. Appendix 1, pp4-12. In: Government of Japan (Fujise,Y., Tamura, T., Kato, H. and Kawahara, S. eds.), Some considerations of the feasibility
components of the JARPN II research plan. Paper SC/56/O2 submitted to the 56th IWC ScientificCommittee, 36pp.
Kishiro, T., Kato, H., Ohizumi, H., Yoshida, H., Saito, T., Isoda, T., Tabata, S., Sakakibara, M.,
Saino, S., Hara., T., Hayashi, T., Miyashita, T., Fukudome, K., Kiwada, H., and Kawahara, S.
5

SC/60/O6

2003. Report of the 2002 JARPN II survey in the western North Pacific. Part II: Coastal
component - Coastal Survey off Kushiro, northeast Japan. Paper SC/55/O8 submitted to the 55th
IWC Scientific Committee, 26pp.
Miyashita, T. and Hatanaka, H. 1997. A note on whaling grounds for the western North Pacificminke whale. Rep .int. Whal. Commn 47:539-542.
Tamura, T. and Fujise, Y. 2002. Geographical and seasonal changes of the prey species on minke
whale in the Northwestern Pacific. ICES Journal of Marine Science, 59:516-528.
Tamura, T., Hakamada, T., Konishi, K., Fujise, Y., Kishiro, T., Yoshida, H., Ohizumi, H. and Kato,
H. 2004. Recalculation of sample size of common minke whales in coastal areas required for
estimating consumption of various prey items based on results of JARPN II. Appendix 2, pp13-17.
In: Government of Japan (Fujise, Y., Tamura, T., Kato, H. and Kawahara, S. eds.), Someconsiderations of the feasibility components of the JARPN II research plan. Paper SC/56/O2
submitted to the 56th IWC Scientific Committee, 36pp. Paper SC/56/O16 submitted to the 56th
IWC Scientific Committee, 36pp.
Yoshida, H., Kato, H., Kishiro, T., Iwasaki, T., Miyashita, T., Ryono, T., Tabata, S., Sakakibara, M.,
Saino, S., Hara, T., Hayashi, T., Tomizawa, Y., Tamai, K., Okamoto, R., Fukuoka, M., Watanabe,H., Tsunekawa, M. and Kawahara, S. 2004. Report of the coastal survey on common minke
whales off Sanriku coast, northeast Japan: the Japanese whale research program under special
permit in the western North Pacific – Phase II (JARPN II) in 2003 (Part II) – Coastal component.
Paper SC/56/O14 submitted to the 56th IWC Scientific Committee, 31pp.
Yoshida, H., Kato, H., Kishiro, T., Iwasaki, T., Miyashita, T., Saito, T., Tabata, S., Morita, Y., Sato,
H., Okada, A., Tomizawa, Y., Saino, S., Kuroishi, H., Ebisui, T., Nakai, K., Nishiwaki, S. 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- Coastal component off
Sanriku. Paper SC/58/O9 submitted to the 58th IWC scientific Committee, 30pp.

6

SC/60/O6
39N

39N

40゜N

Ayukawa

36゜
NSendai Bay
138゜E

38N

142゜E

50 n.miles
100m

200m

38N
141E

141E

142E

142E

143E

Fig. 2. Cruise trucks made by four sampling vessels in the 2007 JARPNII coastal
survey off Sanriku.

Fig．1. Research area of the 2007 JARPNII coastal survey off Sanriku.

7

SC/60/O6

200m

200m

100m

100m

38° N

38° N

0

141° E

10

20km

0

142° E

141° E

Fig. 3. Sighting position of common minke whales made by sampling
vessels in the 2007 JARPNII coastal survey off Sanriku.

10

20km

142° E

Fig. 4. Sighting position of sampled common minke during the 2007 JARPNII coastal
survey off Sanriku.

8SC/60/O6

14
Male (n=21)
Female (n=36)

12

Number of animals

10
8
6
4
2

9.0-

8.5-9.0

8.0-8.5

7.5-8.0

7.0-7.5

6.5-7.0

6.0-6.5

5.5-6.0

5.0-5.5

4.5-5.0

4.0-4.5-4.0

0

Body length (m)Fig．5. Frequency of body length of common minke whales taken in the 2007 JARPNII coastal survey bysex.
25Male (n=21)
Female (n=36)

15

10

5

Body weight (t)

9

9.0-

8.0-9.0

7.0-8.0

6.0-7.0

5.0-6.0

4.0-5.0

3.0-4.0

2.0-3.0

1.0-2.00-1.0

Number of animals

20SC/60/O6

Fig．6. Frequency of body weight of common minke whales taken in the 2007 JARPNII coastal survey bysex.
Table 1. Searching days, hours, distances by four sampling vessels in the 2007 JARPN II coastal
surveys off Sanriku.
Sampling vessels*

Period

75K
9
55.0
590.4

07K
9
56.0
593.1

31S
9
55.1
598.7

Total

First period(16-30 April)

Days
Hours
Distances (n. mile)

28T
9
52.0
588.6

Second period(1-15 May)

Days
Hours
Distances (n. mile)

9
55.2
630.9

9
53.7
580.4

9
61.7
664.0

9
53.0
589.2

36
223.6
2464.5

Third period(16-31 May)

Days
Hours
Distances (n. mile)

11
71.5
805.2

11
69.6
724.6

11
73.0
759.1

11
60.8
669.5

44
274.9
2958.3

Total

Days
Hours
Distances (n. mile)

29
178.7
2024.729
178.3
1895.429
190.7
2016.229
168.8
1857.5116716.57793.736218.1
2370.9*: 28T; Taisho Maru No.28, 75K; Koei Maru No.75, 07K; Katsu Maru No.7, 31S; Sumitomo
Maru No.31.
Table 2. List of cetacean species and number of sightings made by four sampling vessels in the2007 JARPN II coastal surveys off Sanriku.

Common minke whale
Like minke whale

PrimarySch. Ind.
41
42
7
7

SecondarySch. Ind.
6
6
0
0

Total
Sch. Ind.
47
48
7
7

Second period(1-15 May)

Common minke whale
Like minke whale

51
6

52
6

2
0

2
0

53
6

54
6

Third period(16-31 May)

Common minke whale
Like minke whale
Unidentified whale

57
10
1

59
10
2

9
0
0

10
0
0

66
10
1

69
10
2

Total

Common minke whale
Like minke whale

149
23

153
23

17
0

18
0

166
23

171
23

PeriodSpecies

First period(16-30 April)10

SC/60/O6

Unidentified whale

1

11

2

0

0

1

2

SC/60/O6

Table 3. Density index of common minke whales by sampling vessels
in the 2007 JARPN II coastal survey off Sanriku.
PeriodSPUE*1

DI*2

First period (16-30 April)

0.19

1.77

Second period (1-15 May)

0.23

2.11

Third period (16-31 May)

0.21

1.99

Total

0.21

1.96

*1

: No. of primary school sightings per 1 hour searching.

*2: No. of primary school sightings per 100 n. miles searching.

Table 4. Summary of biological data and samples collected during the 2007 JARPN II coastal survey off Sanriku.

Number of animals
Male Female Total

Samples and data
Detailed measurements of blubber thickness (11 points)
Body length and sex
External body proportion
Photographic record and external character
Diatom film record
Body scar record
Measurements of blubber thickness (5 points)
Detailed measurements of blubber thickness (11 points)
Body weight
Body weight by parts
Skin tissues for DNA study
Muscle, liver, kidney, spleen, blubber, heart and ventral groove for various analysis
Urine for various analysis
Muscle, liver, kidney, and blubber for heavy metal analysis
Muscle, liver, kidney, and blubber for organochlorine analysis
Collection of blood plasma
Muscle and vertebra for lipid analysis
Mammary grand; lactation status, measurement and histological sample
Uterine horn; measurements and endometrium sample
Collection of Ovary
Photographic record of fetus
Foetal length and weight
External measurement of fetus
Muscle, liver, kidney, heart, blubber and skin tissues of fetus
Collection of fetus

12

21
21
21
21
21
21
2
21
2
21
21
8
21
21
20
2
2
2
2
2
0

36
36
36
36
36
36
0
36
0
36
36
0
36
36
34
0
36
36
36
3
3
3
3
0

57
57
57
57
57
57
2
57
2
57
57
8
57
57
54
2
36
36
36
6*
6*
5
5
1*

SC/60/O6

21
21
21
21
20
21
21
21
21
21
21
21
21
21
21
21

Testis and epididymis; weight and histological sample
Stomach contents, convenient record
Volume and weight of stomach content in each compartment
Observation of marine debris in stomach
Stomach contents for feeding study
Record of external parasites
Earplug for age determination
Tympanic bulla for age determination
Eye lens for age determination
Largest baleen plate for morphologic study and age determination
Baleen plate measurements (length and breadth)
Photographic record of baleen plate series
Length of baleen series
Vertebral epiphyses sample
Number of ribs
Skull measurement (length and breadth)

36
36
36
30
36
36
36
36
36
35
36
36
36
36
36

21
57
57
57
50
57
57
57
57
57
56
57
57
57
57
57

*: including a fetus of sex unidentified.

Table 5. Statistics of body length (m) of common minke whales collected during the 2007 JARPN II
coastal survey off Sanriku.
Male
FemalePeriodmean S.D. Min. Max. nmean S.D. Min. Max. n
First period (16-30 April)
6.26 0.95 5.09 7.41 3
5.46 1.15 4.33 7.99 7
Second period (1-15 May)

6.28

1.30

4.49

7.77

8

5.49

1.06

4.40

7.91

13

Third period (16-31 May)

6.23

1.40

4.24

8.06

10

5.91

1.18

4.05

8.80

16

Total

6.25

1.30

4.24

8.06

21

5.67

1.16

4.05

8.80

36

Table 6. Statistics of body weight (tons) of common minke whales collected during the 2007 JARPN II
coastal survey off Sanriku.

First period (16-30 April)Malemean S.D. Min. Max.
2.97 1.16 1.66 4.48

Second period (1-15 May)

3.13

1.58

1.11

Third period (16-31 May)

3.07

1.53

Total

3.08

1.50

Period13n3Femalemean S.D. Min. Max.
2.35 1.52 1.17 5.94

n
7

5.50

8

2.18

1.20

1.18

4.93

13

1.05

5.25

10

2.88

1.90

0.91

8.35

16

1.05

5.50

21

2.52

1.63

0.91

8.35

36

SC/60/O6

Table 7. Composition of sex and sexual maturity status of common minke whales collected by the2007 JARPN II coastal survey off Sanriku.
Male
PeriodIm M Uk Total

FemaleMaturity
(%)
0.33

7

Maturity
(%)
0.14

13

0.15

16

0.25

36

0.19

Imm. R P P&L Total

First period
2 1
0
3
6
0 1
0
(16-30 April)
Second period
4 4
0
8
0.50
11
1 0
1
(1-15 May)
Third period
5 4
1
10
0.44
12
0 4
0
(16-31 May)
Total
11 9
1
21
0.45
29
1 5
1
Im: Immature, M: Mature, R: Resting, P: Pregnant, P&L: Pregnant and lactating

Table 8. Prey species found in forestomach of common minke whales collected by the 2007 JARPN II
coastal survey off Sanriku.
Prey species
PeriodSamplesize

First period(16-30 April)

Sand lance(adult)Japaneseanchovy

Sand lance (adult) andJapanese anchovy

10
(%)

6
60.0

3
30.0

1
10.0

Sand lance(adult)and Krill0
0.0

Second period(1-15 May)

19
(%)

9
47.4

8
42.1

2
10.5

0
0.0

0
0.0

Third period(16-31 May)

20
(%)

12
60.0

3
15.0

3
15.0

1
5.0

1
5.0

Total

49*

27

14

6

1

1

(%)

55.1

28.6

12.2

2.0

2.0

*

: excluding animals with broken stomach by harpoon.

14

None
0
0.0

SC/60/O6

Appendix 1
2007 coastal prey species survey of JARPN II off Sanriku
Shiroh Yonezaki1, Hiroshi Nagashima2, Hiroto Murase3, Ryuichi Matsukura4, Kazunari Shiraishi2,
Kiyotaka Takahashi2 and Shigeyuki Kawahara1
1

National Research Institute of Far Seas Fisheries, 5-7-1 Orido, Shimizu-ku, Shizuoka 424-8633, Japan
Miyagi Prefecture Fisheries Research and Development Center, 97-6 Sodenohama, Watanoba,
Ishinomaki, Miyagi 986-2135, Japan
3
The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan
4
Graduate School of Environment Science, Hokkaido University, 3-1-1 Minato-cho, Hakodata, Hokkaido
041-8611, Japan
2

ABSTRACTA prey species survey was conducted in the coastal region off Sanriku, northeastern Japan, concurrently
with the coastal sampling survey for common minke whale during spring 2007 as a part of JARPN II
study. The objective of concurrent surveys was to estimate the prey preference (selection) of common
minke whale. While the sampling survey for common minke whale was conducted within 30 nautical
miles (max 50 nautical miles) from Ayukawa port in Miyagi prefecture, the prey species survey was
conducted in wider area at depths between 20 m and 200 m from 37º 40’ N to 38º 40’ N off Sanriku,
northeastern Japan. The survey area was divided into 7 blocks with depth and latitude. The
distribution and abundance of the prey species were investigated with the quantitative echosounder (EK500) on board Takuyo Maru (120 GT) steaming at 9 – 10 knots along the track lines during daytime.
Acoustic data were acquired with operating frequency at 38, 120 and 200 kHz. Species/size
compositions of echo signs were identified by targeting mid-water trawlings. As well as the last year,
the water temperature was high. Therefore, many schools of anchovy were distributed. Echo signs
identified as adult sand lance (> 10 cm in standard length) occurred at depths between 20 m and 60 m on
Block B and C. Many echo signs identified as juvenile sand lance occurred as smaller patches in the
mid-layer in the shallower area. Krill was frequently found at depths deeper than 70 m.
INTRODUCTION
The goal of JARPN II is to contribute to the conservation and sustainable use of marine living resources
including whales in the western North Pacific, especially within Japan’s EEZ (Government of Japan,
2002). The priority is put on feeding ecology and ecosystem studies, involving studies of prey
consumption by cetaceans, prey preference (selection) of cetaceans and ecosystem modeling. As it isdifficult to cover the coastal area, especially in spring and autumn, by the Nisshin Maru, the full-scale
JARPN II has a new coastal component, that is, the sampling survey for common minke whale bysmall-type whaling catcher boats. As in 2003, 2005, and 2006 surveys (Kawahara et al., 2004; Yonezaki
et al., 2006, 2007), a prey species survey was conducted in the coastal region off Sanriku northeasternJapan, concurrently with the coastal sampling survey for common minke whale during spring 2007. In
this document, the results of the 2007 prey species survey off Sanriku are presented.
MATERIALS AND METHODS
While the sampling survey of common minke whale was conducted in the coastal waters within the 30
nautical miles (max 50 nautical miles) from Ayukawa port in Miyagi prefecture, the prey species survey
was conducted in wider area at depths between 20 m and 200 m from 37º 40’ N to 38º 40’ N off Sanriku,
northeastern Japan, to elucidate the distribution and abundance of main prey species (Fig. 1). To avoid
the conflict with set nets in the coastal waters, the waters 10 miles from the coastal lines were excluded inprinciple. The survey area was divided into 7 blocks (A, B, C, D, E, F, and G) at depths of 40m/100m
and 37º 40’ N/37º 54’ N/38º 15’ N. Blocks E, F, and G south of 37º 54’ N are located off Fukushima15

SC/60/O6

prefecture. A zigzag track line was set to cover each block. The waypoints of planned track lines ineach block were shown in Table 1.
The prey species survey was conducted from April 9 to 27 in blocks A, B, C, D, E, F and G by
Takuyo Maru (Miyagi prefecture, 120 GT). The distribution and abundance of the prey species were
investigated with the quantitative echosounder (EK 500) steaming at about 9-10 knots along the tracklines. The survey was conducted during the daytime from an hour after sunrise to an hour before sunset.
Oceanographic observations were conducted with CTD-EPCS (Continuous Sea Surface Water Monitoring
System). With EPCS, temperature, salinity and chlorophyll in the surface water were measured every
minute. Preliminary sighting survey was made for marine mammals such as northern fur seals.
Acoustic data were acquired with Echoview Ver.3 (Sonar Data Co., Ltd.) with operating frequency at 38,
120 and 200 kHz. Calibrations were carried out at a depth around 30m in Ishinomaki Bay (April 92007) using the copper sphere technique described in EK 500 manual. Trawl sampling was conducted
to identify the species and size compositions of targeting echo signs. The trawl net had a mouth openingof 7 m width/3.5 m height and a 3 mm liner cod end. The depth and the height of the mouth of the net
were monitored with a net recorder. Towing speed of the trawl net was 2-4 knots. Catches of trawl
were identified to the species level and weighed aboard the vessel. For the major species, a sample of
100 animals was taken, and lengths and weights were measured. Scaled and standard lengths were used
to anchovy and adult/juvenile sand lance, respectively. Total length from the tip of the rostrum to theend of the telson was used for krill. Some frozen samples were taken for further analysis in thelaboratory.
RESULTS
The planned track lines were almost covered in the acoustic survey (95 %). A summary of the midwater
trawl operations, temperature by depth and catches was shown on Table 2. Targeting trawlings were made10 times and CTD observations were made at the trawling points and 26 waypoints. The oceanographic
conditions are described in Appendix 2 in the report.
Acoustic data were analyzed with Echoview Ver.3 at the laboratory and the results are as
follows. The surface water temperature in the survey area was between 8.2 ºC and 14.7 ºC based on EPCS.
The surface water temperature of survey area was slightly higher than last year (6.7 ºC - 13.9 ºC)(Yonezaki et al., 2007), and many schools of Japanese anchovy were occurred during the prey species
survey (Table 2). Echo signs identified as adult sand lance (> 10 cm in standard length) occurred at
depths between 20 m and 60 m in blocks B, C, E, and F. Especially, many echo signs identified as adultsand lance were found in blocks F off Fukushima prefecture. The echo signs on the echograms were in
the shape of patches on the bottom or sticks rising from the bottom. Juvenile sand lance could be
identified from the difference in average Sv values between 38 and 120 kHz. Many echo signs
identified as juvenile sand lance occurred in the shallower area of Sendai Bay (Blocks B and E). Mostof the echo signs were smaller patches, usually found in the mid-layer. Although the difference inaverage Sv values by frequency is similar to that of krill, juvenile sand lance could be identified based on
the distribution patterns and the size of the echo signs. Krill was frequently found at depths deeper than
70 m. In most cases the echo signs were large patches and in the shape of belts in the mid/bottom layers
or sticks rising from the bottom.
We have constructed a Bayesian assessment model on sand lance in Sendai Bay (Okamura etal., 2007). This result will contribute to the development of the model of which the accuracy is higher.
ACKNOWLEDGEMENT
A special thank is given to Captain H. Kimura, and crews of Takuyo Maru for their dedication incollecting data.
REFERENCES
Government of Japan. 2002. Research Plan for Cetacean Studies in the Western North Pacific underSpecial Permit (JARPN II). IWC/SC/54/O2 submitted to the 54th IWC Scientific Committee
Meeting, 115pp.
Kawahara, S., Watanabe, H., Ichihara, M., Suenaga, Y. and Katayama, M. 2004. 2003 prey species survey(coastal component) of JARPN II. Appendix 1, pp 15-20. In: Yoshida, H., Kato, H., Kishiro, T.,

16

SC/60/O6

Iwasaki, T., Miyashita, T., Ryono, T., Tabata, S., Sakakibara, M., Saino, S., Hara, T., Hayashi, T.,
Tomizawa, Y., Tamai, K., Okamoto, R., Fukuoka, M., Watanabe, H., Tsunekawa, M. and Kawahara,
S. 2004. Report of the coastal survey on common minke whales off Sanriku coast, northeast Japan:
the Japanese Whale Research Program under Special Permit in the western North Pacific – Phase II(JARPN II) in 2003 (Part II) – Coastal component. Paper SC/56/O14 submitted to the 56th IWC
Scientific Committee Meeting, 31 pp.
Okamura, H., Nagashima, H., and Yonezaki, S., 2007. A Bayesian assessment model of the effects ofconsumption by marine mammals on sandlances. IWC/SC/59/O14 submitted to the 59th IWC
Scientific Committee Meeting ,11pp.
Yonezaki, S., Nagashima, H., Murase, H., Nagaki, T., Shimizu, D., and Kawahara, S. 2006. 2005 coastal
prey species survey of JARPN II off Sanriku. Appendix 1, pp 16-22. In: Yoshida, H., Kato, H.,
Kishiro, T., Iwasaki, T., Miyashita, T., Saito, T., Tabata, S., Morita, Y., Sato, H., Okada, A.,
Tomizawa, Y., Saino, S., Kuroishi, H., Ebisui, T., Nakai, K., Nishiwaki, S., and Kawahara, S. 2005.
Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in
the Western North Pacific (JARPN II) in 2005- Coastal component off Sanriku. IWC/SC/58/O9
submitted to the 58th IWC Scientific Committee Meeting, 30 pp.
Yonezaki, S., Nagashima, H., Murase, H., Kohyama, K., Oshitani, S., Nemoto, K., Matsukura, R.,
Minami, K., and Kawahara, S. 2007. 2006 coastal prey species survey of JARPN II off
Sanriku-Johban. Appendix 1, pp 16-24. In: Goto, M., Kato, H., Zenitani, R., Yoshida, H., Saito, T.,
Tabata, S., Morita, Y., Sato, H., Okamoto, R., Maeda, H., Odagawa, A., Ebisui, T., Nakai, K.,
Matsumoto. A., Fujimori, S., Nishiwaki, S., and Kawahara, S. 2007. Cruise report of the second
phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific(JARPN II) in 2006- Coastal component off Sanriku. IWC/SC/59/O6 submitted to the 59th IWC
Scientific Committee Meeting, 34 pp.

17

SC/60/O6

Table 1. Waypoints of planned lines.
Block A
WP
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10

Latitude38 38 38 38 38 38 38 38 38 38 -

40.1
38.0
35.0
32.0
29.0
26.0
23.0
20.0
17.0
15.0

N
N
N
N
N
N
N
N
N
N

Longitude141- 46.7141- 36.1141- 50.9141- 35.3141- 50.4141- 36.6141- 50.6141- 36.0141- 50.0141- 40.8

E
E
E
E
E
E
E
E
E
E

Course
256
104
256
104
255
105
255
105
255
TOTAL

Distance
8.5
12.0
12.6
12.2
11.2
11.4
11.8
11.4
7.5
98.6

Latitude38 38 38 38 38 38 38 38 38 38 38 37 37 37 37 -

21.0
19.0
17.0
15.0
13.0
11.0
09.0
07.0
05.0
03.0
01.0
59.0
57.0
55.0
54.0

N
N
N
N
N
N
N
N
N
N
N
N
N
N
N

Longitude141- 16.2141- 24.5141- 09.2141- 19.2141- 01.6141- 15.6140- 58.7141- 16.2140- 57.5141- 14.6140- 56.8141- 13.8140- 58.6141- 12.2141- 06.1

E
E
E
E
E
E
E
E
E
E
E
E
E
E
E

Course
107
261
104
262
100
261
98
262
98
262
98
261
101
258
TOTAL

Distance
6.8
12.2
8.1
14.0
11.2
13.5
13.9
14.9
13.6
14.2
13.6
12.2
10.9
4.9
163.9

Latitude38 38 38 38 38 38 38 38 38 38 38 38 37 37 37 37 37 -

17.0
15.5
14.0
12.5
11.0
09.5
08.0
06.5
05.0
03.5
02.0
00.5
59.0
57.5
56.0
54.5
54.0

N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N

Longitude141- 24.0141- 19.5141- 29.6141- 18.2141- 31.3141- 16.4141- 28.3141- 16.1141- 27.1141- 14.5141- 26.1141- 14.3141- 25.2141- 13.6141- 24.6141- 12.2141- 16.3

E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E

Course
247
101
261
98
263
99
261
100
261
99
261
100
261
100
261
99
TOTAL

Distance
3.8
8.1
9.1
10.4
11.8
9.5
9.7
8.8
10.0
9.3
9.4
8.7
9.3
8.8
9.9
3.3
140.0

Block B
WP
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
B12
B13
B14
B15

Block C
WP
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17

18

SC/60/O6

Block D
WP
D1
D2
D3
D4
D5
D6
D7
D8
D9

Latitude38 38 38 38 38 38 37 37 37 -

15.0
13.0
10.0
07.0
04.0
01.0
58.0
55.0
53.9

N
N
N
N
N
N
N
N
N

Longitude141- 40.6141- 49.4141- 30.4141- 48.9141- 26.8141- 48.0141- 24.8141- 41.1141- 35.0

Course
106
259
102
260
100
261
103
258
TOTAL

Latitude
37
37
37
37
37
37
37
37
37
37
37
-

54.0
53.0
51.5
50.0
48.5
47.0
45.5
44.0
42.5
41.0
40.0

N
N
N
N
N
N
N
N
N
N
N

Longitude
141
141
141
141
141
141
141
141
141
141
141
-

08.3
00.0
12.8
02.3
12.0
02.0
08.6
02.7
10.1
02.4
07.1

E
E
E
E
E
E
E
E
E
E
E

Course
261
98
260
101
259
106
252
104
256
105
TOTAL

Distance
6.6
10.2
8.4
7.8
8.1
5.4
4.9
6.0
6.3
3.9
67.7

Latitude
37
37
37
37
37
37
37
37
-

54.0
52.0
50.0
48.0
46.0
44.0
42.0
40.0

N
N
N
N
N
N
N
N

Longitude
141
141
141
141
141
141
141
141
-

12.3
23.6
13.1
23.1
10.4
21.6
10.6
21.3

E
E
E
E
E
E
E
E

Course
103
256
104
259
103
257
103
TOTAL

Distance
9.1
8.5
8.2
10.2
9.1
8.9
8.7
62.8

Latitude
37
37
37
37
37
37
37
37
-

54.0
52.0
50.0
48.0
46.0
44.0
42.0
40.0

N
N
N
N
N
N
N
N

Longitude
141
141
141
141
141
141
141
141
-

24.4
39.9
23.1
38.2
22.7
37.3
21.4
35.9

E
E
E
E
E
E
E
E

Course
99
261
99
261
100
261
100
TOTAL

Distance
12.4
13.4
12.1
12.4
11.7
12.8
11.7
86.5

E
E
E
E
E
E
E
E
E

Distance
7.2
15.2
14.9
17.7
17.0
18.5
13.4
4.8
108.8

Block E
WP
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
E11

Block F
WP
F1
F2
F3
F4
F5
F6
F7
F8

Block G
WP
G1
G2
G3
G4
G5
G6
G7
G8

19

SC/60/O6

Table 2. A summary of the trawl sampling operations, temperature by depth and catches.

Depth temp.

StationDate
Time
LatitudeLongitude
Block
Surf. Temp.
10 m
20 m
30 m
40 m
50 m
75 m
100 m
125 m
Depth (m)Net depth (m)

St-1
4/11
7:29
38-07
141-16
B
8.90
8.86
8.84
8.66
8.35

St-2
4/11
9:41
38-05
140-58
B
9.70
9.06

St-3
4/12
5:56
37-56
140-59
B
9.62
9.66

St-4
4/12
10:31
37-56
141-23
C
9.29
8.98
8.74
8.53
8.38
8.02
6.81

St-5
4/18
14:42
38-04
141-28
D
9.28
8.93
8.89
8.88
8.87
8.82
8.10
8.11

St-6
4/23
7:51
38-17
141-14
B
10.0
9.88
8.78

St-7
4/23
10:40
37-58
141-01
B
10.67

St-8
4/25
5:57
37-54
141-12
F
10.02
9.81
9.12
8.55
8.52

41
22-27

19
12-19

18
9-18

80
75-80

102
90-100

26
15-25

22
10-20

40
20-30

Jelly fish

Juvenile

Juvenile

Adult

Krill (17)JapaneseJapaneseJapanese

sand

sand

sand

anchovyanchovyanchovy

lance

lance

lance

(110),(90),(120),

(54)

(58)

Krill

Juvenile

Adult

(18),

sand

sand

Juvenile

lance

lance

sand

(64)

(120)

Major species
caught,(Averagelength (mm))

lance
(42)

Catches (kg)

< 0.1

3.7

St-9
4/25
7:46
37-49
141-18
F
9.73
9.61
9.17
8.79
8.70
8.46

caught, (Average(120), Adult sandlength (mm))

lanceCatches (kg)

6.5

Depth temp.

StationDate
Time
LatitudeLongitude
Block
Surf. Temp.
10 m
20 m
30 m
40 m
50 m
75 m
100 m
125 m
150 m
Depth (m)Net depth (m)Major species

71
45-55
Japanese anchovy

4.6

0.8

St-10
4/26
13:46
38-28
141-46
A
9.12
9.14
8.73
8.67
8.59
8.30
7.98
7.35
7.29
6.28
162
150-160
Krill (18)

3.1

20

1.6

20.1

7.7

0.05

SC/60/O6

Kesen-numa
MIYAGI
38.40 N

Ayukawa
IshinomakiA

38.15 N

B

C

D
37.54 NSoma
FUKUSHIMA

E

F

G
37.40 N

Fig. 1. Survey area and blocks of prey species survey in 2007 off Sanriku.

21

SC/60/O6

Appendix 2
Oceanographic conditions in the coastal survey of JARPN II off
Sanriku, northeastern Japan, in April 2007
Denzo Inagake1, Makoto Okazaki1, Shiroh Yonezaki2, Hiroshi Nagashima3, and Shigeyuki
Kawahara2
1

National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama,
Kanagawa, 236-8648, Japan
2
National Research Institute of Far Seas Fisheries, 5-7-1, Orido, Shimizu, Shizuoka, Shizuoka,
424-8633, Japan
3
Miyagi Prefecture Fisheries technology Institute, 97-6, Sodenohama, Watanami, Ishinomaki,
Miyagi, 986-2135, Japan
Contact e-mail: ina@affrc.go.jp
ABSTRACTA prey species survey was conducted in the coastal region off Sanriku, northeastern Japan,
concurrently with the coastal sampling survey for common minke whales during spring 2007 as apart of JARPN II study. Oceanographic observations were conducted with CTD from 10 to 27 April
2007 by Takuyo-Maru. According to the CTD data at 33 stations, water masses in the survey area
have characteristics of the Cold water (5ºC < temperature < 10ºC at 100 m depth).
Introduction
The oceanographic condition at the Tohoku area, northeastern Japan, is one of the mostcomplicated areas in the world. In this area, there are a lot of fronts and water masses. The
Kuroshio flows northward along the coast of southern Japan to the southern part of the Tohoku areawith warm high-salinity water. The Oyashio flows southwestward along the Kuril Islands to thenorthern part of the Tohoku area with cold low-salinity water. The Kuroshio and the Oyashio flows
eastward from the Tohoku area, and the area between the Kuroshio and Oyashio was usually called
the Kuroshio-Oyashio Inter-frontal Zone or perturbed area. The Tsugaru warm water enters into
the Inter-frontal Zone through Tsugaru Strait and flows southward along the coast of Sanriku. And
also the warm-core ring is cut off from the Kuroshio extension into the Inter-frontal Zone. Eachwater mass is mixed with others, and make a new water mass. Oceanographic condition of thecoastal area off Sanriku is the most variable in the Tohoku area, because the Kuroshio, thewarm-core ring, the Oyashio, the Tsugaru warm water and other water arrive here by turns.
A prey species survey was conducted on board Takuyo-Maru (Miyagi prefecture, 120 GT) in the
coastal region off Sanriku, northeastern Japan, concurrently with the coastal sampling survey forcommon minke whales during spring 2007 as a part of JARPN II study. Oceanographic observations
were conducted with Conductivity Temperature Depth profiler (CTD) by Takuyo-Maru. In this paper,
we analyzed the CTD data to make clear the oceanic environment in the survey area.
Data and Methods
Hydrographic observations with CTD (SBE 19) were carried out at 33 stations from 10 to 27 April
2007 in the coastal area off Sanriku, northeast of Japan (Fig. 1). Salinity correction for CTD data
was not done using water sampling data.
Oceanic fronts and water masses are usually detected by subsurface temperature map (see Table 1),
because they are obscure in sea surface temperature distributions from summer to fall seasons andthe Oyashio water spreads into the subsurface layer. So, the oceanographic conditions in April 200722

SC/60/O6(Fig. 2) are detected by 100m and 200m temperature maps using the monthly mean subsurface
temperature in seas around Japan from NEAR-GOOS (the North-East Asian Regional-Global Ocean
Observing System) database.
Oceanographic conditions in the survey area
Figure 3 shows the Temperature-Salinity diagrams using CTD data. Almost all water mass inthe survey area have characteristics of the Cold water. A few stations show low-salinity water (lessthan 33.5 psu) in the shallow layer, which is mixed with the coastal water.
Figure 2 shows the schematic hydrographic map in April 2007. The northern limit of the Warmwater spreading from the Kuroshio Extension moves northward from March to November. The
position of the Warm water in April 2007 was at 39ºN on 146ºE line, which was a slightly northward
position from monthly mean location in April (38º40’N). Tsugaru warm water was obscurebecause it restricted near the coastal area (called as coastal mode) in April. The southern limit of
the first Oyashio Intrusion located around 39º30’N, 143ºE, which was a little northward position
from monthly mean location in April (38º30’N). All stations in the survey area were distributed in
the Cold water defined by 100 m temperature which is over 5ºC and less than 10ºC.
Figure 4 shows temperature and salinity maps at the depth of 90 m, observed by Takuyo-Maru.
Water of 8ºC to 9ºC and 33.7 to 33.8 psu were dominant at the depth of 90 m in Fig. 4. It meansthat the Cold water occupied in these survey area.
Figure 5 shows vertical sections of temperature and salinity. Cold low salinity water (8 to 10ºC
and less than 34 psu) was dominant at the shallow layer near the coast in Fig. 5. Temperature at thedepth of 100 m is around 8 ºC at the most offshore station in each section.
All of these figures show that all stations are distributed in the cold area, south of the Oyashio.
The surface layer on the shelf off Sanriku was occupied by coastal low-salinity water.
Acknowledgment
A special thank is given to Crews of Takuyo-Maru for their dedication in collecting data.
References
Kawai, H. (1969): Statistical estimation of isotherms indicative of the Kuroshio axis, Deep-Sea
Res., Suppl. to 16, 109-115.
Murakami, M. (1994): On long-term variations in hydrographic conditions in the Tohoku area, Bull.
Tohoku Natl. Fish. Res. Inst., 56, 47-56 (in Japanese with English abstract).

Table 1. Extraction method from temperature map to determine the position of each water massaccording to Kawai (1969) and Murakami (1994).
Target characteristics
Kuroshio Extension Axis
Warm-core ring
Oyashio front
Oyashio water
Cold water
Warm water

Extraction method
14 ºC isotherm at 200 m
Temperature front at 200 m
5ºC isotherm at 100 m
Area with T < 5ºC at 100 m
Area with 5ºC < T < 10ºC at 100 m
Area with T > 10ºC at 100 m and T < 14ºC at 200 m

23

SC/60/O6

Fig. 1.

Fig. 2.

Station map observed by Takuyo-Maru in April 10 to 27, 2007.

Schematic hydrographic map in Tohoku area, northwestern Pacific, in April 2007 with24

SC/60/O6

station map observed by Takuyo-Maru (▲) .

Fig. 3. Temperature-Salinity diagrams using CTD station data observe by Takuyo-Maru in April 10
to 27, 2007. Each thin line in this figure denotes a density line of sigma-t.

Fig.4.

Temperature (left panel) and salinity (right panel) maps at 90 m depth, observed by

Takuyo-Maru in 10 to 27 April 2007.

25

SC/60/O6

Fig.5. Temperature (top), salinity (middle) and density anomaly (bottom) sections along selected stations, observed by Takuyo-Maru in 11 to 27 April 2007.

26

SC/60/O6

27