SC/F16/JR23

Decadal change of feeding ecology in sei, Bryde’s andcommon minke whales in the offshore of the Western
North Pacific
KENJI KONISHI, TATSUYA ISODA AND TSUTOMU TAMURA
Institute of Cetacean Research, 4-5, Toyomi-cho, Cho-ku, Tokyo, 104-0055, Japan
Contact e-mail:konishi@cetacean.jp

ABSTRACT
Stomach contents from sei, Bryde’s and common minke whales sampled by JARPNII cruises in May-October during 2000-2013(2002-2015 for sei whale) off the Pacific coast of Japan were used to examine yearly trend in prey composition. Stomach content
analysis showed that the three whale species are highly dependent on small pelagic fish, in addition to planktonic crustaceans. Thechange of prey compositions in sei whales among years drastically changed from Japanese anchovy in the early 2000s to Japanesesardine in 2014 and 2015, while Neocalanus copepod steadily occurred throughout the years. This decreasing Japanese anchovy
synchronized with the catch record of Pacific stocks in Japanese fisheries. Furthermore sea water temperature and school size weredifferent by prey species. Bryde’s whale has a more simple prey composition, mostly of Japanese anchovy and euphausiid, andwere highly variable among years with no remarkable change during 2000-2013. Prey composition in common minke whales
offshore (east of 146°E) showed Japanese anchovy and Pacific saury are the majority species, but the composition differs among
years. Japanese anchovy used to be consumed by minke whales around 40°N, but euphausiid was consumed in recent years. These
results suggesting a decrease in the amount of Japanese anchovy transported offshore is an important factor to determine thecomposition of the three baleen whales in the JARPNII study area.
KEYWORDS: SEI WHALES, BRYDE’S WHALES, MINKE WHALES, FEEDING ECOLOGY, JARPNII, NORTH PACIFICINTRODUCTION
Offshore of the JARPNII research area is a unique environment under the effect of both cold Oyashio Current andwarm Kuroshio Current and this transition region covers most of the JARPNII research area. Eggs and larvae ofpelagic fish, such as Japanese anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus) aretransported by the Kuroshio Current to offshore (Itoh et al. 2009; Okunishi et al., 2011) and these fish are an
important food item for baleen whales, in addition to crustaceans. Feeding of Sei (Balaenoptera borealis), Bryde’s(B.edeni) and common minke (B. acutorostrata) whales sampled in JARPNII in this area were reported by theauthors (Konishi et al.. 2009). Mackerels (genus Scomber) are also found in the stomachs of baleen whales fromJARPNII study in this offshore area. Because these pelagic fish are also commercially important, there are manystudies in catch history (Yatsu et al., 2005; Yonezaki et al., 2014), optimal environment (Takasuka et al., 2007;2008) and transportation to offshore (Ihoh et al., 2007; 2009; 2011). These studies all suggest that the synchronizedexchange of favourable environment between Japanese sardine and anchovy caused by climate change, which canbe defined by Pacific Decadal Oscillation (PDO) (Mantua and Hare, 2002). In the early 2000s, when sampling ofsei and Bryde’s whales started in the JARPNII, the sardine population had already collapsed and the anchovy catch
had increased (Yatsu et al., 2005; Takasuka et al., 2008; Itoh et al., 2009). The prey of sei, Bryde’s and common
minke whales also showed abundant Japanese anchovy in the stomach, with rare findings of Japanese sardine.
Since PDO fluctuations occur in scale from 15-25 years and 50-70 years (Mantua and Hare, 2002) and continuous
sampling in the JARPNII for more than a decade is long enough to explore changes in the feeding habits of sei,
Bryde’s and common minke whales. Actually, obvious prey changes in sei whales have been observed on board.
The main purpose of this study is to observe the decadal change of feeding habits of sei, Bryde’s and common
minke whales with a general summary by pooling data from all survey years.

METHODS
For the study of basic feeding habits and its decadal change, we used stomach content information from sampled
sei, Bryde’s and common minke whales with water temperature and position of those whales captured in
JARPNII. To show recent changes of stomach contents, we have included data from 2002 to 2015 for sei whales

1SC/F16/JR23

and from 2000 to 2013 for Bryde’s whale. Common minke whales are common across Japan’s coastal area tooffshore areas, and whales have been sampled in different regions and components. Therefore, we used datafrom 2000 to 2013 at east of 146°E to exclude the effects of prey species specific to near and above thecontinental shelf and to see change of prey species in offshore areas. The feeding of common minke whales isreported in Tamura et al. (2016: SC/F16/JR17). Sampling of whales and stomach content treatment was
described in Tamura et al. (2016:SC/F16/JR15). In the analyses, comparison of surface water temperaturesampled between different prey items, prey composition change with school size and distribution of main preyspecies fed on by sei whales were described in addition to the prey composition change with years.

RESULTSSei whale

Sei whales were sampled mostly from east of 150°E and south of 46°N (Figure 1), between north of theKurosho extension and just north of the Subarctic Front (see Appendix 3 and Okazaki et al., 2016:
SC/F16/JR5). The main prey species are Neocalanus copepod, euphausiids, Japanese anchovy Engraulisjaponicus, Mackerels (Scomber japonicus and S. australasicus) and Japanese sardine Sardinops
melanosticus. Pacific saury Cololabis saira and minimal armhook squid Berryteuthis anonychus were also
found in far eastern areas. Sei whales were pooled by each main prey species, and surface watertemperature where whales were sampled were compared (Figure 2). This result suggests that watertemperature where sei whales feed is related to prey species, and feeding of whales on Japanese anchovy
and mackerel occur at higher temperatures than copepods and Japanese sardines. The prey composition in
occurrence grouped by school size was shown in Figure 3, showing a ratio of copepods likely to be higher
in large school sizes. Geographical positions where prey species were fed on by sei whales are illustrated in
Figure 4, showing Japanese anchovy and copepods are eaten through wide longitudinal areas whilemackerels and euphausiid are fed on in a rather small range. The positions where Japanese sardine was fed
on is the most eastern in the survey area overlapping the position of Japanese anchovy and copepod,
however those data are from only two years and do not represent the whole distribution. Figure 5 shows atrend of prey composition in the stomach of sei whales sampled during 2002-2015. In the 2000s Japanese
anchovy, copepod and euphausiid are major components with few exception in 2005 and 2008. In the years
after 2010, mackerels became one of the major prey, which coincided with a decreasing ratio of Japanese
anchovy. In the 2014 and 2015 survey years, Japanese sardine was found to be the most dominant prey in2015 while no Japanese anchovy was confirmed in the stomachs of sei whales. In this year the ration of
copepods are also lowest since 2012.
Bryde’s whale

Sampling positions of Bryde’s whales during 2000-2013 is shown in Figure 6. These positions are locatedrather south of those in sei whale, and a concentration is seen around 145°E to 150°E. Bryde’s whale has
more simple prey composition by Japanese anchovy and euphausiid as main prey species. The comparisonof Surface water temperature where whales were sampled were pooled by prey species and compared(Figure 7). Overall the temperatures are higher than that of sei whales and we did not find any difference oftemperature among prey species. School size of Bryde’s whales is relatively smaller than that of sei whales(Figure 8). However the sample size in a school size of four is one and is difficult to find the feature.
Geographical positions of prey species fed on by Bryde’s whales are drawn in Figure 9. Japanese anchovy
was found in a wide longitudinal range and almost covers the entire area where whales were sampled. The
number of whales that fed on mackerel is small, however high concentrations were found between 115°E to
160°E. In the case of euphausiids, there is a highly concentrated area where Bryde’s whales feed with somesmaller spots in the eastern area. The yearly trend of stomach contents in Bryde’s whales is shown in
Figure 10. The prey composition consists of two species, i.e. euphausiid and Japanese anchovy, andoceanic lightfish Vinciguerria nimbaria and mackerels were found occasionally. The composition of two
main prey species is highly variable among years, and there is no obvious decadal change in the preycomposition of Bryde’s whales during 2000 to 2013. The higher occurrence of euphausiids is unique for
Bryde’s whale.
Common minke whale2SC/F16/JR23

Prey of common minke whales highly depends on Pacific saury and occurs rather north of sei whales. Preycomposition in common minke whales offshore (east of 150°E) showed Japanese anchovy and Pacificsaury are the majority species but the composition differs among years. Unlike sei whales, minke whales do
not depend on copepods. Because the sampling area and sample size do not have consistency among years
in offshore areas, samples were pooled into three terms (2000-2003, 2004-2007 and 2008-2013) and plottedon maps for comparison (Figures 11, 12 and 13). North of the survey area at north of 43°N, Pacific saury is
the dominant prey species in all terms with some occasional occurrences of minimal armhook squid(Berryteuthis anonychus) and Pacific Pomfret (Brama japonica) in most eastern regions. In the years of
2002-2003 and 2004-2007, Japanese anchovy were fed on by minke whales around 40°N while only a few
were eaten in the year of 2008-2013. Instead, euphausiid was eaten at this area.

DISCUSSION
This study showed general feeding habits and those decadal changes for sei, Bryde’s and common minke whales.
Japanese anchovy and mackerels are fed on by sei whales at similar latitudinal and longitudinal areas, but withwarmer water temperatures for Japanese anchovy. This difference may be caused by local distributional differences
depending on prey species. Sei whales make a larger school size when it feeds on copepods, probably suggesting
the sei whale has a function to maximise food intake. In Bryde’s whale, euphausiid is a major prey species in
addition to Japanese anchovy. From the geographical plots for each prey species, areas that Japanese anchovy andeuphausiid were fed on have differences, i.e. Japanese anchovy and euphausiid were found from near the Japanese
coast to 170°E, however, euphausiid was mostly found at south of 38°N at east of 150°E. This suggests that thefeeding habits of Bryde’s whales differ in relation to longitudinal sector and have intensive feeding on euphausiid
between 145°E to 150°E. Common minke whales showed clear differences with other baleen whales withoccurrences at higher latitude to ca. 48°N and dependency on Pacific saury.
The results of prey composition changes with years showed that a remarkable prey shift has occurred in sei whales
since 2002 to 2015, especially a decline of Japanese anchovy occurrence and incidence of Japanese sardines in thelast two years. These changes in Japanese anchovy and sardines coincided with stock abundance estimates of thetwo fish species (well described by Kishiro et al. as Appendix 3 in Tamura et al., 2016:SC/F16/JR17). There wasalso some variation in the composition, such as no or few occurrence of Japanese anchovy in the early 2000s (2005,
2007 and 2008) and occurrence of mackerels. In Bryde’s whales, there was not a clear prey change, probably
because of the simple prey composition, and euphausiid was sometimes the highest occurrence throughout theperiod (2000-2013).
Although both sei, Bryde’s and common minke whale distribute throughout the Pacific with a similar latitudinalband (see Jefferson, et al., 1993), the high availability of pelagic fish in the JARPNII study area is unique.
Therefore, the amount of eggs and juveniles of pelagic fishes transported from the south coastal area and survivaland growth seems to reflect the prey composition of the baleen whale species.
In this study, data from the same survey season were pooled. However, prey distribution, physical environment
and movement of whales is likely to have a dynamic linkage, therefore feeding information with a shorter timescale was shown in Appendix 1. This is just an example from one month, but this kind of information will be
helpful to create a scenario for whale behaviour on a large scale in future studies.

ACKNOWLEDGEMENT
We would like to thank all researchers and crew involved in the JARPN and JARPNII surveys.

References
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50°N

45°N

40°N

35°N

140°E

150°E

160°E

170°E

Figure 1. Sighting position of sei whale sampled in JARPNII cruise (2002-2015).

Tukey Contrast test
Copepods - Anchovy <0.001 ***Euphausiids - Anchovy 0.0298 *Mackerel - Anchovy 0.9961
Sardine - Anchovy <0.001 ***Euphausiids - Copepods <0.001 ***Mackerel - Copepods <0.001 ***Sardine - Copepods 1.0000
Mackerel - Euphausiids 0.2348
Sardine - Euphausiids 0.0262 *Sardine - Mackerel <0.001 ***Figure 2. Relationship between prey species and sea surface temperature where sei whales were caught.

Figure 3. Relationship between school size and prey composition in sei whale.

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Mean foresto. weight (kg)

Mean foresto. weight (kg)

Sei_FirstS_0215

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115 - 172173 - 354

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40°N

40°N

35°N

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140°E

150°E

Mean foresto. weight (kg)
170°E140°E

160°E

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45°N

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40°N

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150°E

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0
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40°N

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Figure 4. Distribution of prey species fed by sei whales sampled in JARPNII cruise (2002-2015). Mean stomach content weight(kg) by 0.5 degree mesh are illustrated. (upper left Japanese anchovy; upper right copepod; middle left mackerels; middle righteuphausiids; bottom Japanese sardine )6

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Figure 5. Trend of prey composition in the stomach contents of sei whales during 2002-2015.

50°N

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150°E

160°E

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Figure 6. Sighting position of Bryde’s whale sampled in JARPNII cruise (2000-2013).

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Figure 7. Relationship between prey species and sea surface temperature where Bryde’s whales were caught.

Figure 8. Relationship between school size and prey composition in Bryde’s whale.

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Figure 9. Distribution of prey species fed by Bryde’s whales sampled in JARPNII cruise (2000-2013). Mean stomach content
weight (kg) per 0.5 degree mesh are illustrated. (upper Japanese anchovy; middle mackerels; bottom euphausiids )9

SC/F16/JR23

Figure 10. Trend of prey composition in the stomach contents of Bryde’s whales during 2000-2013.

50° N

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!
( !
!
(
!
Saury
(
!
(
(!
AnchovySaury
( !
!
Saury
Saury
SaurySaury !
(Saury
(!
(
!
(
!
Saury
Saury
SaurySaury
(!
!
(
(
!
(
!
SaurySaury(Euphausiids!

(!
Euphausiids(!

Anchovy(!

(!

Copepods(!

(!

Copepods( Saury Anchovy
!
(
!
Saury
(
!
(!
!
(
!
(Saury(!
(!
(!
SaurySaury(!

Copepods

Anchovy

EuphausiidsCopepods
(!
!
(
!
(
oceanic lightfish( Euphausiids!

Anchovy
Mackerel(!

Anchovy(!

(!

Euphausiids

35° N

150° E

160° E

170° E

Figure 13. The distribution of prey species fed by common minke whale at east of 146°E during 20082013.

11

SC/F16/JR23

Appendix. 1.
Potential dataset for analyses in feeding ecology: Prey
species with whale density and environmental factors
in the western North Pacific
What factor works in the decision process of prey item for a predator is great concern, however datasometimes need to be pooled in feeding ecology of whales because of the small sample size. Therefore
pooled data through survey season were used for trend of prey composition in the main part of thisdocument. However feeding habits in a short time period with environmental factor is maybe preferable fordirect interpretation between prey species and environmental factors. This information will be helpful to
conduct analyses by integrated dataset from whale sampling, sighting survey and physical environment.
To explore specific feature of prey species in relation to environment with entire survey area but limited
time period (a month) as preliminary analyses by overlaying information on a map and “July” was chosenbecause of available data from every year. When overlaying environmental data with stomach content result,
we used sighting and effort data from sighting and sampling vessel (SSV) and sighting vessels (SV) to
calculate whale density. Sighting survey procedure is described in Matsuoka et al. (2016: JR/F16/JR2). To
examine the spatial and temporal variation of whale diets in relation to monthly Chlorophyll a concentration
with whale density patterns, Chlorophyll a concentration by 4-km mesh data ware obtained by level-3 data
products by NASA Ocean Biology (Sea WiFS) on the satellite images of SST (Aqua MODIS) obtained
from Ocean Color Web (NASA Ocean Biology). Then all density and satellite information were averaged
with 0.5 by 0.5 degree mesh by ArcGIS 10.2.1 (Esri Inc.), and all plotted for each year (Figure 1). As
supplemental information, sighting efforts in July, positions of oceanic fronts are included in Figure 2. To
draw oceanographic fronts, sea surface height data were obtained by AVISO webpage. The altimeterproducts were produced by Ssalto/Duacs and distributed by Aviso, with support from Cnes
(http://www.aviso.altimetry.fr/duacs/). To examine positions of oceanic fronts in JARPNII study area, Argo
data were used for salinity and temperature profile. These data were collected and made freely available by
the International Argo Program and the national programs that contribute to it. (http://www.argo.ucsd.edu,
http://argo.jcommops.org). The Argo Program is part of the Global Ocean Observing System. The locationof oceanographic fronts were shown in Figure 3.

REFERENCE
Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis. NOAA
Technical Memorandum NESDIS NGDC-24. National Geophysical Data Center, NOAA. doi:10.7289/V5C8276M [2015 Nov.].
Favorite, F., Dodimead, A. J., & Nasu, K. 1976. Oceanography of the subarctic Pacific region, 1960-71. International North PacificFisheries Comission, Bulletin N, 187.
Kida, S., Mitsudera, H., Aoki, S., Guo, X., Ito, S., Kobashi, F., Komori, N., Kubokawa, A., Miyama, T., Morie, R., Nakamura, H.,
Nakamura, T., Nakano, H., Nishigaki, H., Nonaka, M., Sasaki, H., Sasaki, Y.N., Suga, T., Sugimonot, S., Taguchi, B., Takaya, K.,
Tozuka, T., Tsujino, H. and Usui, N. 2015. Oceanic fronts and jets around Japan: a review. Journal of Oceanography.
doi:10.1007/s10872-015-0283-7
NASA Ocean Biology (OB): Sea WiFS and MODIS-Aqua Ocean Color Data; NASA Goddard Space Flight Center, Ocean Ecology
Laboratory, Ocean Biology Processing Group. http://dx.doi.org/10.5067/AQUA/MODIS_OC.2014.0 Accessed on 11/26/2015.

12

SC/F16/JR23

55°N

Chlorophyll aconcentration(mg/m3)

Densiy Index (indivisuals per n.mile)
1.2

MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
0.3

Anchovy40°N

0.4 - 0.3

Anchovy Anchovy

CopepodsCopepods
Copepods

0.4

Anchovy

0.5

Euphausiids Euphausiids
Euphausiids

0.6 - 0.5
0.6 - 0.7
Anchovy

Anchovy

0.8
0.9 - 1.1

EuphausiidsEuphausiids
EuphausiidsEuphausiids

35°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

0.32

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2

Copepods

0.3
Anchovy

0.4 - 0.3

Saury

40°N

0.4

Anchovy

Anchovy

Anchovy
Anchovy
Anchovy

0.5
NC

0.6 - 0.5
0.6 - 0.7
0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

140°E

150°E

160°E

170°E

Figure 1. Position, density and prey information of sei, Bryde’s and common minke whales in JARPNII 2002-2013 with
5by5 degree meshed average Chlorophyll a concentration.in July. Whale Density (DI) was calculated from both (SV and
SSV) with efforts per mesh over 5 n.miles and original Chlorophyll a is satellite (NASA Ocean Biology (OB). Seaviewing Wide Field-of-view Sensor (SeaWiFS) Ocean Color Data). (upper: 2002, middle:2003 and bottom:2004 survey
years in July). Prey label of “NC” means no content in the stomach.
13

SC/F16/JR23

55°N

Chlorophyll aconcentration(mg/m3)

Densiy Index (indivisuals per n.mile)
0.38

MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

Copepods

Euphausiids

0.3 - 0.2
0.3 - 0.2

Euphausiids

0.3
0.4 - 0.3

EuphausiidsNC
Euphausiids
Copepods

0.4

40°N

0.5
0.6 - 0.5
0.6 - 0.7
0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

1.9

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N
NC
Anchovy

0.3 - 0.2

Saury
NC
Anchovy

0.3 - 0.2

NC

0.3

SaurySaury

0.4 - 0.3

NC
Anchovy NC Anchovy
Euphausiids NC
Euphausiids NC
Euphausiids Anchovy

40°N

0.4
0.5
0.6 - 0.5

EuphausiidsEuphausiids
NC Anchovy
EuphausiidsAnchovy
Anchovy

Anchovy Anchovy
Anchovy

0.6 - 0.7
0.8Euphausiids
Anchovy

Euphausiids

0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

0.66

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2

Saury
NC

Saury

NC

Saury

NC

0.3

CopepodsNC

40°N
NC
Anchovy

Anchovy

0.3 - 0.2

0.4 - 0.3

Anchovy

0.4

Anchovy
Anchovy

0.5
0.6 - 0.5

Anchovy

0.6 - 0.7
0.8

35°N

0.9 - 1.1

Anchovy Anchovy

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

140°E

150°E

160°E

170°E

Figure 1. continued. (upper: 2005, middle:2006 and bottom:2007 survey years in July)

14

SC/F16/JR23

55°N

Chlorophyll aconcentration(mg/m3)

Densiy Index (indivisuals per n.mile)
0.86

MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
CopepodsNC

Copepods
Copepods
Copepods Copepods
NC

Copepods

0.3 - 0.2
0.3

Copepods
Copepods

40°N

0.4 - 0.3

Anchovy
Copepods

0.4

Anchovy

Euphausiids

Anchovy

0.5

Anchovy
Anchovy

Anchovy
Anchovy
Anchovy
Euphausiids

Anchovy

0.6 - 0.5

Euphausiids

0.6 - 0.7

Anchovy
OceanicLightfish
Euphausiids

0.8

Anchovy

0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

170°E

Densiy Index (indivisuals per n.mile)

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

5.000000e+307

0.0
code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
AnchovyAnchovy
MackerelMackerel

0.3
Anchovy

0.4 - 0.3

NC
NC NC Anchovy AnchovyNC
Anchovy Anchovy

40°N

0.4

NC

0.5
0.6 - 0.5
0.6 - 0.7
0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

0.62

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
CopepodsSaury
Copepods

NCNC

Copepods

Copepods

NCNC

0.3
0.4 - 0.3
0.4

40°N

0.5

Anchovy

0.6 - 0.5
0.6 - 0.7

Anchovy
Anchovy
Anchovy

0.8
Anchovy Anchovy

35°N

0.9 - 1.1
1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

140°E

150°E

160°E

170°E

Figure 1. continued. (upper: 2008, middle:2009 and bottom:2010 survey years in July)

15

SC/F16/JR23

55°N

Chlorophyll aconcentration(mg/m3)

Densiy Index (indivisuals per n.mile)
0.78

MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
0.3
Euphausiids

40°N

0.4 - 0.3

Saury
Euphausiids

Copepods
Anchovy

Anchovy

Anchovy

Euphausiids

Euphausiids
Euphausiids
Anchovy

0.4

Saury NC

0.5

Anchovy

0.6 - 0.5
0.6 - 0.7

Anchovy
Anchovy

0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

1.9

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
NC
Saury

MackerelMackerel NC

Mackerel NC

Copepods

Anchovy
Euphausiids

Anchovy
Anchovy

Anchovy NC

0.4 - 0.3
0.4

Anchovy Saury
Copepods
Anchovy

40°N

0.3

Saury

Saury CopepodsNC

Anchovy Anchovy

0.5

Anchovy

0.6 - 0.5
0.6 - 0.7
0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

55°N

140°E

150°E

160°E

Densiy Index (indivisuals per n.mile)

170°E

0.092

Chlorophyll aconcentration(mg/m3)
MEAN_GRID_

code3

0.0

code4

0.1

50°N

0.2 - 0.1
0.2 - 0.1
0.2 - 0.1
0.2
0.3 - 0.2

45°N

0.3 - 0.2
0.3 - 0.2
0.3
0.4 - 0.3
0.4

40°N

0.5
0.6 - 0.5
0.6 - 0.7
0.8
0.9 - 1.135°N

1.2 - 1.8
1.9 - 2.9
3.0 - 5.0

140°E

150°E

160°E

170°E

Figure 1. continued. (upper: 2011, middle:2012 and bottom:2013 survey years in July)

16

SC/F16/JR23

Figure 2. Sighting efforts of sighting vessel (SV) and sighting and sampling vessel (SSV) for each JARPNII survey cruisefor each year in July.

17

SC/F16/JR23

Figure 2. continued.

18

SC/F16/JR23

Figure 3. Geographical locations of oceanic fronts at western North Pacific in July during 2001-2013. Original data were Argo float(JAMSTEC) Upper left: 1) Subarctic Front: 4C isotherm at 100m depth (Argo data from JAMSTEC), Upper right: Subarctic
boundary: salinity of 34 psu at near surface (Argo data from JAMSTEC), bottom left: 3) Kuroshio extension norther branch, bottom
right: 4) Kuroshio extension from sea surface height: (AVISO absolute dynamic topography derived from sea surface heightmeasured by several satellites, AVISO, France, http://www.aviso.altimetry.fr) eddies area also drawn. Detail of oceanographic
feature in JARPN I during2000 to 2013 is well described in Okazaki et al. (2016: SC/F16/JR5). Definition of boundary wasdescribed in Kida et al. (2015).

REFERENCES
Kida S, Mitsudera H, Aoki S, et al., 2015. Oceanic fronts and jets around Japan: a review. J Oceanogr. doi: 10.1007/s10872-015-0283-7
Okazaki, M., Masujima, M., Murase, H. and Morinaga, K. 2016. Oceanographic conditions in the JARPNII survey area from 2000 to 2013 using FRA-ROMS data.
SC/F16/JR5 presented to the JARPNII special permit expert panel review workshop, Tokyo, February 2016 (unpublished) .

19