SC/66b/SP

Cruise report of the second phase of the Japanese whale
research program under special permit in the western
North Pacific (JARPN II) in 2015 – (Part II) – coastal
component off Sanriku
Toshihiro Mogoe1, Nobuyuki Ito2, Tatsuya Isoda1, Tomio Miyashita3, Gen Nakamura4, Naoko Miyakawa4, Saeko
Kumagai2, Hitomi Sato2, Yuta Okitsu2, Hisoka Hiruda2, Nozomi Kobayashi4, Taiki Katsumata4, Kozue Ishida4,
Moe Takahashi4, Ayumi Hirose4, Masayoshi Ota4, Koichiro Kato4, Ryotaro Hayashi4, Kouhei Yoshii4 andHidehiro Kato4
1

The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan
Association for Community-Based Whaling, Hakata-Eki-Higashi, Hakata-ku, Fukuoka 812-0013, Japan
3
National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Yokohama, Kanagawa, 236-8648, Japan
4
Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-0075, Japan
Contact e-mail: mogoe@cetacean.jp
2

ABSTRACTAs part of the JARPN II in 2015, four small-type whaling catcher boats, Taisho Maru No.28, Koei Maru No.8,
Katsu Maru No.7 and Sumitomo Maru No.51 conducted the whale sampling survey in the coastal region of Japan.
This paper reports the results of the coastal component (off Sanriku) of the Japanese whale research program under
special permit in the western North Pacific (JARPN II) in 2015. The survey was carried out on the Pacific coastof Japan (the sub-area 7CS) from 10 April to 26 May 2015. The research was set in coastal waters within 50n.miles
from Ayukawa Port in Miyagi Prefecture in the Sanriku district of Japan using four small-type whaling catcher
boats as sampling vessels. During the survey, a total of 5,776n.miles (596 hours) was surveyed, a total of 31
sightings of common minke whales was made. The trial of biopsy sampling and faecal sampling for common
minke whales was conducted in this survey using the Larsen biopsy gun system. On April 5, 2015 Gunners andresearchers had a meeting for the experiment and treatment of the system. The trial of shooting was carried out.
During the survey, one sighting of common minke whale had been encountered during a total searching 54 hours
32 minutes. A trial for biopsy skin sampling was conducted. After one hour 36 minutes chasing, no samples werecollected because of the quick movement of target whale. A total of 19 animals were lethally sampled from 31
primary sightings of common minke whales. All sampled animals were landed at the land research station in
Ayukawa where biological examinations were carried out. Regarding dominant prey species found in theforestomach, most were classified as krill (44.4%), followed by adult sand lance (22.2%), Japanese sardine (22.2%)
and juvenile sand lance (11.1%). Among the four prey species observed in this survey, Japanese sardine were
continuously observed. In terms of body length, average body length of the sampled animals was 4.99m (SD=0.78)
for males, and 5.49m (SD=1.24) for females. A prey species survey was conducted in parallel and in the same time
period as the main survey. In April, backscatterings of juvenile sand lance and Japanese anchovy were observedin southern Sendai bay. In May, backscattering of krill was observed off the coast of Sendai bay. From the resultof prey species survey and stomach contents from sampled animals, distribution of the common minke whales inSanriku region was related to sand lance distribution.
KEYWORDS: BIOPSY SAMPLING; COMMON MINKE WHALE; FOOD/PREY; SCIENTIFIC PERMITSBACKGROUND
The full-scale survey of the JARPN II started in 2002, after conducting two-year feasibility studies in 2000 and2001 (GOJ, 2002). The objectives of the full-scale research are: i) to study on feeding ecology and ecosystem
studies, involving studies of prey consumption by cetaceans, prey preferences of cetaceans and ecosystemmodelling; ii) to monitor environmental pollutants; iii) to study on stock structure, particularly for minke whales.
Target species are common minke whale (Balaenoptera acutorostrata), Bryde’s whale (Balaenoptera edeni), sei
whale (Balaenoptera borealis) and sperm whale (Physeter macrocephalus). In the full JARPN II plan, the coastal
survey component was firstly implemented as a two-year feasibility study conducted in 2002 and 2003 (GOJ,
2004). Coastal research is conducted by small-type whaling catcher boats and has features that cover the temporaland spatial gap, which could not be covered by the Nisshin Maru unit. After the two years feasibility survey, thecoastal component of JARPN II was revised to be conducted twice a year in spring and autumn. The first revised1

survey was carried out at off Kushiro in autumn of 2004 (Kishiro et al., 2005). Target species of the coastal
component were set at 120 common minke whales (60 common minke whales to be sampled in each season). The
results of these coastal survey have revealed that common minke whales consume various prey species. In the off
Kushiro survey, krill (Euphausia pacifica), Japanese anchovy (Engraulis japonicus), Pacific saury (Cololabis
saira), walleye pollock (Theragra chalcogramma) and Japanese flying squid (Todarodes pacificus) wereconsumed by the common minke whales. On the other hand, krill (Euphausia pacifica), Japanese sand lance(Ammodytes personatus) and Japanese anchovy (Engraulis japonicus) were consumed by whales in the off Sanriku
area (Tamura et al., 2009). The findings of different prey species in a different year or places suggest the elasticity
of prey preference of common minke whales in the coastal area of Japan. The coastal component off Sanriku of
JARPN II in 2015 was carried out following the research plan of the earlier cruise which took place in the samewaters off Sanriku in 2014 (Mogoe et al., 2015). These surveys were mainly undertaken in order to obtain theinformation of feeding ecology of common minke whales which migrate through Sendai Bay.
RESEARCH METHODS
Research area
The research sector was set in the coastal waters off Sanriku, within the 50n.miles from the Ayukawa port (Figure1), which was same as the previous surveys (Mogoe et al., 2015). This sector is included in the middle part of the
sub area 7CS of the revised sub areas for the implementation review for Western North Pacific common minke
whales (IWC, 2012). The research area was further divided into 3 sectors. Because of logistical constraint and theaccident at the Fukushima nuclear power stations in 2011, the southern boundary line of the research area is set atthe administrative boundary between Miyagi and Fukushima Prefecture (due east of 37.54°N from land).
Research vessels, land station and research period
Four small-type whaling catcher boats, Taisho Maru No.28 (47.3GT), Koei Maru No.8 (32.0GT), Katsu Maru
No.7 (32.0GT) and Sumitomo Maru No.51 (30.0GT) conducted the survey for sampling. Miyashio (199.0GT)
conducted the prey species survey and collected oceanographic data for the research area in the same period. Allof the sampled whales were landed at the Ayukawa port. Biological surveys and sampling took place at the land
station. The research period was set for 47 days, from 10 April to 26 May 2015.
Searching and sampling methods
Searching and sampling methods were similar to the past coastal survey off Sanriku (Kishiro et al., 2016). The
research head office was placed in the research station and controlled the sampling vessels during the survey. To
avoid the concentration of the sampling location, the research head office arbitrarily determined the searching
sector and direction from the base point for each sampling vessel every day. The vessels continued to cruise andsearch along the predetermined direction from the base point until they arrived at 30n.miles and then freely cruisedin the waters within the research area. Sighting activities were carried out during the day and the vessels returned
to port every night. Searching effort were conducted within acceptable weather, visibility and sea conditions, by
the crew in the top barrel and upper bridge. In each vessel, one dedicated researcher was on board and recorded
the cruise tracks, searching time on effort, sea and weather conditions, and the species and the estimated numberof whales in the sighted schools. Target species for sighting record were all baleen whales, sperm whales and killer
whales. All common minke whales sighted were targeted for sampling, except for cow-calf pairs. When a sighting
consisted of more than one animal, the first targeted animal was selected following the random sampling digits.
50mm explosive harpoon guns equipped with penthrite grenades were used as the primary killing method. Once a
vessel caught a whale, it returned to the Ayukawa port to transport the animal to the research station. While
returning to the port, other common minke whales sighted were also targeted for sampling, if the situation allowed.
At the port, the sampled whale was lifted up from the vessel using wire nets and a crane, and transported to thestation by an 11 ton freight trailer.
Practicability survey for collection of biopsy and faecal samples
The practicability survey for collection of the skin biopsy and faecal samples was conducted using the four smalltype whaling catcher boats. The system for biopsy skin sampling was the Larsen biopsy gun. Large intestinecontents from three sampled whales were collected for genetic analysis of prey species identification. Observationof excretion was conducted for common minke whales targeted for lethal and biopsy sampling.
2

Biological research on common minke whales
All sampled whales were biologically examined by researchers at the research station. Research items of thebiological studies are summarised in Table 3. Body length and external proportions of the whale were measured
in the same manner as the offshore component of JARPN II. Body weights were measured using a crane scale.
Body parts and organ weights of each whale were measured by summing of body parts using an electronic hanging
scale. The stage of maturity was categorised according to the gonads. The maturity of the female was determinedby the presence of corpus luteum or corpus albicans in either ovary. In the case where no corpus luteum or corpus
albicans was observed in both ovaries, the female was categorized as immature. Conversely, if either corpus luteum
or corpus albicans was observed in ovaries, the female was categorized as sexually mature. The ‘mature’ male wasdefined preliminary based on the weight of one testis over 290g. The weight of stomach contents was measured
by the same methods used in the offshore component of the JARPN II. Stomach contents were weighed to thenearest 0.1kg for each of the four chambers including and excluding liquid (Fujise et al., 2002). For further
biological studies of feeding ecology, stock structure, life historical biology and pollutions, the data and samples
were collected from the captured whales. These included skin, tissue sample, eye lens, ear plug, and morphometricmeasurements.
Prey species survey
The prey species survey with oceanography were conducted using Miyashio. The acoustic data for prey species
were collected using a quantitative echosounder. Oceanographic data were recorded by CTD and EPCS. These
results are summarised in the Appendix.
RESULTS
Searching effort by sampling vessels
The cruise tracks of the sampling vessels during the research periods are shown in Figure 1. The survey was
conducted on 47 days, a total of 596 hours and 5,776.5n.miles of effort. Searching effort mainly covered the southwestern part of the whole research area. Table 1 shows an outline of the sighting activities. During the 47 days ofthe survey period, the sampling vessels conducted searching for only 23 days (48.9% of the predetermined days).
Out of 24 days of cancellation in the research cruise, the most frequent reason was unsuitable weather conditions,e.g., low atmospheric pressure and fog. The ratio of days when searching was conducted in this survey was thelowest compared to the former coastal component surveys.
Sightings and sampling of common minke whales
Figure 2 shows the distribution of sighted and sampled common minke whales by the sampling vessels. A total of
33 schools (33 individuals) of common minke whales, were sighted during the survey period. Density index ofcommon minke whales was calculated as 0.51 for DI (the number of primary sightings per 100n.miles searchingeffort) and 0.09 for SPUE (the number of primary sighting per 1 hour searching effort). Out of 31 schools (31individuals), were targeted for sampling and 19 individuals were sampled for biological research. Sampling
efficiency (the rate of successful sampling for targeted whales) was 0.61. In the sampling process, there was no
struck and lost animals.
Sighting of other large whales
Humpback whales and one unknown large whales were identified during the research period. Figure 3 shows thegeographical distribution of sighting position of humpback and unknown large whales. Table 2 shows the numberof sightings for these 4 species including common minke whales during the survey. Humpback whales were
distributed widely along the 100m depth contour line.
Practicability survey for collection of biopsy and faecal samples
Practicability survey for biopsy sampling and faecal sampling for common minke whales was carried out in thissurvey. As for biopsy sampling, the system for the sampling was the Larsen biopsy gun system. On 5 April 2015,
Gunners and researchers had a meeting for discussing the experiment, and training in the use of the Larsen biopsy
gun took place on 12 April (Figure 4). During this training, gunners and crew of small-type whaling catcher boats
had used a number of darts for the first time. During the non-lethal survey, one sighting of common minke whale
had been encountered during a total searching 54 hours 32 minutes. The trial for biopsy skin sampling was
conducted on this whale. After one hour 36 minutes chasing, no samples were collected because of the quick
movement of target whale.
3Biological research on common minke whales
Sex ratio, body length and maturity of common minke whales caught
Table 5 summarises the reproductive status of the sampled whales. Sampled whales consisted of a total of 19
whales; 9 females and 10 males. Body length of sampled whales is summarized in Table 4. Average body lengthof the whales was 4.99m (min=4.22m, max=6.56m, SD=0.78m) for males, and 5.49m (min=4.10m, max=8.05m,
SD=1.24m) for females. Immature whales ranged from 4.10m to 6.56m (4.22-6.56m for males, 4.10- 5.58m forfemales). No matured male animals were sampled. Mature whales ranged from 6.82 and 8.05m (female only).
Mean body length of female and male sampled in the first half of the research period (10 Apr–3 May) were 5.33m(n=7) and 4.62m (n=8), respectively. In the second half period (4 May–26 May), male and female were 6.82m and5.85m, respectively.
Prey species of common minke whale found in the stomach
The weight of stomach contents including liquid in forestomach ranged from between 0.0kg and 47.3kg, andaverage weight was 13.8kg (0.54% of mean body weight). Table 6 provides the composition of the dominant preyspecies obtained from forestomach contents in common minke whales. Three prey species were confirmed in thestomach contents of 18 individuals from 19 samples, and dominant prey species were krill (44.4%), followed byadult sand lance (22.2%), Japanese sardine (22.2%) and juvenile sand lance (11.1%).
Observation of marine debris
Marine debris was detected from the stomach of 3 mature animals. Ingested debris were pieces of wood and plastics.
One whale entanglement in fishing gear of the upper jaw was recognized by observation of body surface from all
sampled animals.
DISCUSSION
The JARPN II coastal component off Sanriku in the spring season in 2015 was conducted using the small-typewhaling catcher boats. This report provides continuous data of biological study in the coastal region off Sanriku.
The sampling vessels conducted the research for 23 days (48.9%) out of 47 days of the total survey period. The
ratio of research days was the lowest in those of the off Sanriku surveys so far. On the whole, the poor weather
conditions such as strong winds or poor visibility reduced sighting efforts. Although the composition anddistribution of whale species were similar to the previous survey (Mogoe, et al., 2015), a low value of the DI for
common minke whales was observed. Even though the DI was not so high, a dense distribution area of common
minke whales was formed in the Sendai Bay as in the past surveys. Since all vessels investigated the same area
every day, the sighting record probably includes some duplicated sightings.
A practicability survey for collection of biopsy and faecal samples for common minke whales was conducted. No
sample was collected because of low density and few opportunity of a trial, although shooting training using theLarson gun was conducted. During the survey, effort was made to collect the samples through 54 hours 32 minutes
searching. One sighting of common minke whale had been encountered however, after 1 hour 35 minutes 45
seconds chasing, no sample collected because of the quick movement of target whale.
Figure 5 shows the composition of prey species of common minke whales off Sanriku during the seasons 2003–
2015. Sand lance is an important food item of common minke whales off Sanriku. The rate of occurrence of krill
and anchovy changed, although sand lance remained the dominant prey species. In recent years, juvenile sandlance (less than 10cm) newly appeared as prey species of common minke whales. Japanese sardine and mackerels
were found as prey species of common minke whales in early May (second half period of this survey). Both species
were dominant prey species of common minke whales in the areas around Japan during the commercial whaling
period from the 1960s to the late 1980s (Kasamatsu and Tanaka, 1992). The recent possible change of the preyspecies found in the stomachs of common minke whales suggested that this could have influenced to the
distribution of common minke whales in the Sanriku district.
As for other large whales sighted in this research, humpback whales were sighted in the research area. The total
number of sightings in the research area (46 schools 65 individuals) was twice that sighted for common minke
whales (33 schools 33 individuals) in this survey. Humpback whales sightings have increased over last year’s
survey (Mogoe et al., 2015; 2014: 42 schools 50 individuals). Krill was the most numerous large prey species forcommon minke whales in a first half period of 2015 survey and humpback whales were sighted in the same period
in parallel with common minke whale sightings. The 100m contour line was same as the krill fishing area in thisregion. Therefore, it may be possible to explain that krill was a prey species for these two whale species and that
this might effect the distribution of two species. One minke whale sample was attacked and partly eaten by killer
whales during the capture at the small-type whaling catcher boat. As a result, some biological data could not be
obtained for this individual.
4The eleventh survey off Sanriku district was conducted from 10 April to 26 May 2015. During the 47 day survey
period, a total of 596 hours and 5,776n.miles of effort, 31 schools of common minke whales were made by four
small-type whaling catcher boats. Thirty-one schools of common minke whales were sighted. A total of 19 whales
were caught. Average body length of the sampled animals was 5.49m (SD=1.24, n=9) for females and 4.99m(SD=0.78, n=10) for males (sex ratio: 0.53 of male). Dominant prey species were krill (44.4%), followed by adultsand lance (22.2%), Japanese sardine (22.2%) and juvenile sand lance (11.1%). This report provided the continued
data of biological and ecological information on common minke whales in the off Sanriku region.
ACKNOWLEDGEMENTS
The authors express their gratitude to Luis A. Pastene (ICR), Tsutomu Tamura (ICR), Genta Yasunaga (ICR),
Tomio Miyashita (NIFS), Toshiya Kishiro, Yukito Narisawa (FAJ), Shinichi Tashiro (FAJ), Ishinomaki city
official and Miyagi prefectural government official for their guidance and implementation of the research. The
authors also would like to express our sincere thanks to the crew members of the research vessels and staff of theland station. With the sudden death in October 2015 of Keiichi Endo, managing director of the whaling company
in Ayukawa, the whale researchers lost their lifelong mentor. We send grateful and warm thoughts to his family
and the Japan small-type whaling association.
REFERENCE
Government of Japan. 2002. 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, June 2002 (unpublished). 115pp.
Government of Japan. 2004. Revised research plan for cetacean studies in the western North Pacific under special
permit (JARPN II). Paper SC/56/O1 presented to the IWC Scientific Committee, July 2004 (unpublished).
14pp.
International Whaling Commission. 2012. Report of the first RMP intersessional workshop for western North
pacific common minke whales. J. Cetacean Res. Manage. (Suppl.) 13: 413–59.
Kasamatsu, F. and Tanaka, S. 1992. Annual changes in prey species of minke whales taken off Japan 1948-87.
Nippon Suisan Gakkaishi 58(4): 637–51.
Kato, H. 1992. Body length, reproduction and stock separation of minke whales off northern Japan. Rep. int. Whal.
Commn. 42: 443–53.
Kishiro, T., Kato, H., Yoshida, H., Miyashita, T., Ryono, T., Tabata, S., Okamoto, R., Yasui, K., Sato, H., Morita,
Y., Saino, S., Hara, T., Ebisui, T., Kuroishi, H., Nishiwaki, S., and Kawahara, S. 2005. Cruise Report of thecoastal survey on common minke whales off Kushiro, northeast Japan: the 2004 JARPN II survey (Part II) Coastal component. Paper SC/57/O4 presented to the IWC Scientific Committee, June 2005 (unpublished).
37pp.
Kishiro, T., Yoshida, H., Yasunaga, G., Bando, T., Mogoe, T. and Kato, H. 2016. Methodology and survey
procedure under the JARPN II – coastal component of Sanriku and Kushiro- during 2008 to 2014, with special
emphasis on whale sampling procedures. Paper SC/F16/JR3 presented to the JARPN II Review Workshop,
February 2016. (unpublished). 18pp.
Mogoe, T., Bando, T., Ito, N., Nakamura, G., Hiruda, H., Oikawa, H., Isoda1, T., Kumagai, S., Sato, H., Sakamoto,N., Miyakawa, N., Takahashi, M., Fukumoto, A., Ota, M., Furuyama, Y., Hirose, A., Kato, K., Hayashi, R.,
Yoshii, K., Yoshida, H. and Kato H. 2015. Cruise Report of the Second Phase of the Japanese Whale Research
Program under Special Permit in the western North Pacific (JARPNII) in 2014 - Coastal component off
Sanriku. Paper SC/66a/SP5 presented to the IWC Scientific Committee, June 2015 (unpublished). 16pp.
Tamura, T., Konishi, K., Goto, M., Bando, T., Kishiro, T., Yoshida, H., Okamoto, R. and Kato, H. 2009. Prey
consumption and feeding habits of common minke whales in coastal areas off Sanriku and Kushiro. Paper
SC/J09/JR9 presented to the Expert Workshop to Review Results of JARPN II, January 2009 (unpublished).
18pp.
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 presented to the IWC ScientificCommittee, July 2004 (unpublished). 31pp.
5

TABLES AND FIGURES
Table 1
Summary of searching effort (hours and distances) conducted during the 2015 JARPN II coastal component
off Sanriku.
Sampling vessels

Days
Hours
Distance(n.miles)

Total

28T

08K

07K

51S

22
158:51:37
1,590.3

22
141:27:51
1,383.7

23
135:44:10
1,327.1

22
160:19:43
1,475.4

596:23:21
5,776.5

Table 2
Summary of whale sightings conducted by sampling vessels in the research area.
SpeciesPrimary

Secondary

Total

School Individuals

School Individuals

School IndividualsFirst half period (10 Apr–3 May)
Common minke whale
Like minke whale
Fin whale
Humpback whale
Killer whale
Unknown large whale

26
18
0
40
5
7

26
18
0
57
14
7

0
0
0
0
2
0

0
0
0
0
11
0

26
18
0
40
7
7

26
18
0
57
25
7

Second half period (4 May–26 May)
Common minke whale
Like minke whale
Fin whale
Humpback whale
Killer whale
Unknown large whale

5
6
0
5
4
3

5
6
0
7
10
3

2
2
0
1
0
0

2
2
0
1
0
0

7
8
0
6
4
3

7
8
0
8
10
3

Total
Common minke whale
Like minke whale
Fin whale
Humpback whale
Killer whale
Unknown large whale

31
6
0
45
9
10

31
6
0
64
24
10

2
2
0
1
2
0

2
2
0
1
11
0

33
8
0
46
11
10

33
8
0
65
35
10

Table 3
Summary of biological data and samples collected in the 2015 JARPN II coastal survey off Sanriku.
Samples and data

Number of animals

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)
Whole body weight
Body weight by parts
Skin tissues for DNA study

6

Female

Male

Total

9
9
9
9
9
9
1
9
1
9

10
10
10
10
10
10
0
10
0
10

19
19
19
19
19
19
1
19
1
19

Table 3
Continued.
Samples and data

Number of animals
Female

Male

Total

9
1
9
9
8
9
9
9
9
0
0
0
0
0
0
0
‒
‒
9
9
9
1
2
9
8
9
0
0
9
9
9
2
9
8
5
9
2
4
9
5
9
4

10
3
10
10
8
10
‒
‒
‒
‒
‒
‒
‒
‒
‒
‒
10
5
10
10
10
6
1
10
8
10
0
1
10
10
10
2
10
10
1
9
2
4
9
3
10
2

19
4
19
19
16
19
9
9
9
0
0
0
0
0
0
0
10
5
19
19
19
7
3
19
18
19
0
1
19
19
19
4
19
18
6
18
4
8
18
8
19
6

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 gland; lactation status, measurement and histological sample
Uterine horn; measurements and endometrium sample
Collection of Ovary
Photographic record of foetus
Foetal length and weight
Skin tissues for DNA study of foetus
External measurement of foetus
Muscle, liver, kidney, heart, blubber and skin tissues of foetus
Eye lens of foetus for age determination
Collection of foetus
Testis and epididymis; weight and histological sample
Testis for examination of gene expression
Stomach contents, convenient record
Volume and weight of stomach content in each compartment
Observation of marine debris in stomach
Collection of stomach contents for feeding study
Stomach wall for digestion study
Record of external parasites
Earplug for age determination
Eye lens for age determination
Tympanic bulla for age determination
Largest baleen plate for morphologic study and age determination
Baleen plate measurements (length and breadth)
Photographic record of baleen plates series
Length of baleen series
Vertebral epiphyses sample
Number of ribs
Skull measurement (length and breadth)
Skull measurement (detail)Measurement of the skull around nasal bone
Content of large intestine
Measurement and sampling of pelvic bone
External measurement of nostril
Collection of diatoms on the skin
Measurement of flipper white patch
Tissues for cell culture

Table 4
Mean body length of common minke whales sampled in 2015 JARPN II coastal component off Sanriku.
PeriodMale

Female

Mean

SD

Min

Max

N

Mean

SD

Min

Max

N

First half period (10 Apr–3 May)
Second half period (4 May–26 May)

4.62
5.85

0.38
0.86

4.22
4.90

4.90
6.56

7
3

5.33
6.82

1.21
NA

4.10
NA

8.05
NA

8
1

Total

4.99

0.78

4.22

6.56

10

5.49

1.24

4.10

8.05

9

7

Table 5
Reproductive status of common minke whales sampled in 2015 JARPN II coastal component off Sanriku.
PeriodMale
Immature Mature

FemaleTotal

Maturity(%)

Immature Mature(Preg)Total

Sex ratio
Pregnancy Maturity(%)(%)(% males)First half period(10 Apr–3 May)
Second half period(4 May–26 May)

7

0

7

0.0

7

1 (0)

8

0.0

12.5

46.7

3

0

3

0.0

0

1 (0)

1

0.0

100

75.0

Total

10

0

10

0.0

7

2 (0)

9

0.0

22.2

52.6

Table 6Frequency appearance of dominant prey species found in forestomach contents of common minke whales
sampled by the 2015 JARPN II coastal component off Sanriku*.
Krill

Sendai bay
Other area

Sand lance

Japanese sardine

Total

JuvenileAdult

6 (44.4%)
2 (11.1%)

2 (11.1%)
0 (0.0%)4 (22.2%)
0 (0.0%)0 (0.0%)4 (22.2%)

12 (66.7%)
6 (33.3%)

8 (44.4%)

2 (11.1%)

4 (22.2%)

4 (22.2%)

18 (100%)*: Excluding one animal with an empty stomach.

Figure 1. Geographical location of the research area and cruise track-lines of four sampling vessels in 2015
JARPN II coastal component off Sanriku.
8Figure 2. Geographical distribution of sighting position of common minke whales made by sampling vessels in2015 JARPN II coastal component off Sanriku. Closed circle: sighting and sampling school; open circle: only
sighting school. Each plot is based on the position of sighting school.

Figure 3. Geographical distribution of sighting position of humpback and unknown large whales sighted bysampling vessels in 2015 JARPN II coastal component off Sanriku. Closed triangle: humpback whale; open
square: unknown large whales. The size of the plot means school size (1 to 3 individuals).
9Figure 4.
Training of shooting of the Larsen biopsy gun. The styrene foam was used for dummy target
predetermined shooting distance.

100

Percentage

80
60
40
20
0
2003

2005

2006
2007
Sand lance
Krill

2008
2009
2010
Japanese anchovy
Japanese sardine

2012
2013
Mackerels

2014

2015

Figure 5. The yearly composition of dominant prey species which were found in the forestomach of common
minke whales in JARPN II coastal component off Sanriku during the seasons 2003–2015 (percentage of thefrequency appearance). Individuals which have broken forestomach by a harpoon or have empty forestomach
were excluded from the analysis.

10

APPENDIX
Coastal prey species survey of JARPN II off Sanriku in 2015
Mitsuhiro Saeki1, Soumei Gamge1, Keiichi Onodera1, Tsutomu Tamura2 and Toshihiro Mogoe2
1

Miyagi Prefecture Fisheries Technology Institute, 97-6 Sodenohama, Watanoha, Ishinomaki, Miyagi 986-2135,
Japan
2
The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan
ABSTRACTA prey species survey was conducted in the coastal region off Sanriku, northeastern Japan in spring 2015 as a partof JARPNII coastal component off Sanriku. The survey was conducted concurrently with a sampling survey ofcommon minke whales. The survey was conducted on April 23 and 24 and May 15 and 22. Four stratified blocks
were surveyed in April (B, C Survey Blocks) and the two blocks (A,D Survey Blocks) were surveyed in May.
Zigzag track-lines were set in the blocks. A trawler type R/V, “MIYASHIO”, conducted the survey. Acoustic data
were recorded continuously along track-lines by a quantitative echosounder. Samplings using a midwater trawl
net were conducted at two stations to identify species and body size compositions of acoustic backscatterings.
Vertical oceanographic conditions were recorded at 15 stations by using a CTD. Subsurface oceanographic
conditions were recorded continuously along track-lines.
INTRODUCTION
JARPN II is designs to contribute to conservation and sustainable use of marine living resources including whalesin the western North Pacific, especially within Japan’s EEZ (Government of Japan, 2002). One of the major
objectives of JARPNII is to study feeding ecology of cetaceans and ecosystem studies, involving studies of prey
consumption by cetaceans, prey preference of cetaceans and ecosystem modelling. To accomplish the goal, asampling survey of common minke whales (Balaenoptera acutorostrata) and a survey to estimate biomass of theirprey species have been conducted concurrently off Sanriku as a component of JARPN II since 2003 except for2011 with the Great East Japan Earthquake. This document presents the results of the prey species survey off
Sanriku in 2015.
SURVEY METHODS
While the sampling survey of minke whales was conducted in the coastal waters within the 50n.miles (mainly
within 30n.miles) from Ayukawa, Miyagi prefecture, Japan, the prey species survey was conducted in a wider area
at bottom depths between 20 m and 200 m from 37º 54’ N to 38º 40’ N off Sanriku, north-eastern Japan, to elucidate
the distribution and abundance of main prey species. Seven survey blocks (A-G) have been set within the survey
area since 2005 for the purpose of biomass estimation of prey species based on a stratified random sampling
method using echosounder data (Figure 1). Stratification of blocks was based on bottom depth (20, 40, 100, and200m) and the boundary between Miyagi and Fukushima prefecture. Because of logistical constraint and the
Fukushima nuclear accident, only 2 blocks (B, C) were surveyed in April and 2 blocks (A, D) were surveyed in
May in 2015(Figure 1). A zigzag track-line was set in each block. The waypoints of planned track-lines in eachblock are shown in Table 1.
The survey was conducted on April 23 and 24 and May 15 and 22. The survey was conducted during the daytime
from an hour after sunrise to an hour before sunset. Acoustic, trawl, and oceanographic surveys were conductedusing a trawler-type R/V, “MIYASHIO” (Miyagi prefecture, 199 GT). Data of distribution and abundance of theprey species were recorded by a quantitative echosounder, EK60 (Simrad, Norway) with operating frequency at
38, 120 and 200 kHz. The RV steamed at 9-10 knots along the track-lines. Acoustic data were stored with the aidof software, Echoview (Sonar Data, Australia). Calibration was carried out in the survey area on 17 April and on
14 May using the copper sphere technique described in EK 60 manual. Vertical oceanographic observations wereconducted with CTD. Subsurface (approximately 5m water depth) temperature, salinity and chlorophyll-a wererecorded every minute (in time) along the track-lines.
Trawl sampling was conducted to identify the species and size compositions of targeting echosigns. The trawl net
had a mouth opening of 7 m (width) by 3.5 m (height) and a 3 mm liner cod end. The depth and the height of themouth of the net were monitored with a net recorder. The towing speed of the trawl net was 2-4 knots. Catches
were identified to the species level and weighed aboard the vessel. For the major species, 39 Japanese anchovy
11and 5 adult sand lances and about 500 grams juvenile sand lance were taken, and lengths and weights were
measured. Scale and standard lengths were used to Japanese anchovy (Engraulis japonicus) and sand lance (adultand juvenile, Ammodytes personatus), respectively. Some samples were frozen for further analysis in thelaboratory.
RESULTS
The planned track-lines were almost surveyed by the quantitative echosounder. The trawl was towed at two stations.
A summary of the midwater trawl samples is shown in Table 2. CTD casts were conducted at 15 stations. In April,backscatterings of juvenile sand lance and Japanese anchovy were observed in southern Sendai bay. In May,
backscatterings of krill were observed off the coast of Sendai bay. Detailed analysis will be conducted in thelaboratory and the results will be presented in the near future.
ACKNOWLEDGEMENTS
We would like to thank the captain of R/V “MIYASHIO”, Mr. Tatsuo Kanomata, and his crew who assisted us tocollect a valuable data set. This survey was supported by the Fisheries Agency of Japan and Miyagi Prefecture.
We thank these institutions for their support.
REFERENCES
Government of Japan. 2002. 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, June 2002 (unpublished). 115pp.
TABLES AND FIGURES
Table 1
Waypoints and planned lines.
Block A
Waypoint
A1
A2
A3
A4
A5

Latitude
38
38
38
38
38

-

Longitude
15.0
20.0
26.5
37.0
40.0

N
N
N
N
N

141
141
141
141
141

-

50.5
38.0
50.0
42.5
51.0

E
E
E
E
E

Course (degree)

Distance (n.mile)

297°
055°
331°
066°
-

11.0
11.4
12.0
7.3
Total

41.7

Block B
Waypoint
B1
B2
B3
B4
B5
B6
B7

Latitude
37
37
38
38
38
38
38

-

Longitude
54.0
59.0
03.0
09.0
13.0
17.0
21.5

N
N
N
N
N
N
N

141
141
141
141
141
141
141

-

00.5
13.0
00.0
15.5
05.0
20.0
20.5

E
E
E
E
E
E
E

Course (degree)

Distance (n.mile)

063°
291°
064°
296°
071°
332°
-

11.1
11.0
13.6
9.2
12.5
5.1
Total

12

62.5

Table 1
Continued.
Block C
Waypoint

Latitude

C1
C2
C3
C4
C5
C6
C7

38
38
38
38
38
37
37

-

Longitude
15.5
13.5
10.0
06.0
59.0
59.0
54.0

N
N
N
N
N
N
N

141
141
141
141
141
141
141

-

33.0
35.0
22.0
26.0
15.0
23.0
14.0

E
E
E
E
E
E
E

Course (degree)

Distance (n.mile)

142°
251°
142°
245°
115°
235°
-

2.5
10.8
5.1
9.5
7.0
8.7
Total

43.6

Block D
Waypoint

Latitude

D1
D2
D3
D4
D5

38
38
38
37
37

-

Longitude
15.0
11.0
05.0
58.0
54.0

N
N
N
N
N

141
141
141
141
141

-

51.0
35.0
50.0
28.0
40.5

E
E
E
E
E

Course (degree)

Distance (n.mile)

252°
117°
248°
112°
-

13.2
13.2
18.7
10.6
Total

Table 2A summary of the trawl sampling.
St-1

St-2

Block

C

B

Date

23 Apr.

23 Apr.

Time

10:23

14:03

Latitude38-02N

37-55NLongitude141-16E

141-03E

0m

10.6

11.3

10 m

9.17

9.65

20 m

8.28

7.38

30 m

7.66

Temp (°C) by depth

Station

40 m
50 m
75 m
100 m
Bottom
(m)

7.03
(38m)

7.29
(20m)

Trawl sampling
depth (m)

10-25

10-20

Major sampled species

Sand lance(juvenile)

Sand lance(adult andjuvenile)
Japanese anchovy
Sea sponge

13

55.7

Figure 1. Survey blocks and planned track-lines in 2015.

14