SC/D06/J23

Interactions between oceanography, krill and baleen whales in
the Ross Sea and Adjacent Waters: An overview of
Kaiyo Maru-JARPA joint survey in 2004/05
Naganobu, M.1, S. Nishiwaki2, H. Yasuma3, R. Matsukura3, Y. Takao4, K. Taki1, T. Hayashi1,
Y. Watanabe5, T. Yabuki6, Y. Yoda7, Y. Noiri8, M. Kuga9, K. Yoshikawa10, N. Kokubun11, H.
Murase2, K. Matsuoka2, and K. Ito12
1

National Research Institute of Far Sea Fisheries, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa,236-8648 Japan
2
Institute of Cetacean Research, 4-5 Toyomi, Chuo-ku, Tokyo 104-0055, Japan
3
Hokkaido University, 3-1-1 Minatocho, Hakodate 041-8611, Japan
4
National Research Institute of Fisheries Engineering, 7620-7 Hasaki, kamisu, Ibaraki, 314-0408, Japan
5
Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-8477, Japan
6
Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
7
Offshore Operation Co., Ltd., 1-8-7 Motoasakusa, Taitou-ku, Tokyo, 111-0041 Japan
8
Marine Works Japan Ltd., 3173-25 Shouwamachi, Kanazawa-ku, Yokohama, kanagawa, 236-0011 Japan
9
Weathernews Inc., 1-3 Nakase, Mihama-ku, Chiba, 261-0023 Japan
10
The University of Tokyo, 1-1-1 Yayoi, Bunkyou-ku, Tokyo, 113-8657 Japan
11
National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo, 173-8515 Japan
12
Environmental Simulation Laboratory, 2-4-1 Arajyuku-cho, Kawagoe, Saitama, 350-1124 Japan

Abstract
A joint survey of the R/V Kaiyo Maru and the Japanese Whale Research Program under Special
Permit in the Antarctic (JARPA) was carried out to study an interaction between oceanography asenvironmental condition, distribution of krill as prey and baleen whales as predators in the Ross Sea
and its adjacent waters, Antarctica, in austral summer of 2004/05. Results indicated closeinteractions between the oceanography, krill and baleen whales. The oceanography of the surface
layer was summarized as an oceanographic environmental index that integrated temperature meanfrom 0 to 200 m in depth (ITEM-200). Distribution of ITEM-200 was used as backgroundinformation for comparing with distribution patterns of each species. Antarctic krill mainly
distributed in the Antarctic Surface Water (ASW) area (ITEM-200 = 0 to -1oC) and extended in the
Shelf Water (SW) area (less than -1oC). Ice krill clearly distributed in SW but not ASW.
Humpback whales mainly distributed in the Antarctic Circumpolar Current (ACC) waters with highdensity around 0oC near the Southern Boundary of ACC and slightly extended in ASW. Antarctic
minke whales mainly distributed in ASW and SW with high density around -1 oC in a continental
shelf slope frontal zone. The interaction between distributions of krill and baleen whales with
ITEM-200 could give the quantitative information to identify the boundary of distribution of
Antarctic krill and ice krill for biomass estimation using acoustic data in the surveys. We finallysummarized a conceptual model of interaction between oceanography relating water mass andcirculation pattern of the oceanic surface layer with ITEM-200, the distribution and abundance ofkrill and baleen whales.

11. Introduction
The study here is of interactions between oceanography, krill and baleen whales in the Ross Sea
and its adjacent waters with a joint survey the R/V Kaiyo Maru and the Japanese Whale Research
Program under Special Permit in the Antarctic (JARPA).in the 2004/05 austral summer season.
As the background of the present study, there was a cooperated survey between the Kaiyo Maru
and JARPA. JARPA was conducted every year from 1987/88 to 2004/05 in the Area III-IV-V-VI
in the waters off east Antarctica and the Ross Sea collecting data of sighting and biologicalsampling for whales with basic oceanographic and acoustic measurement (Hatanaka et al., 2006;
Nishiwaki et al., 2006). On the other hand, the Kaiyo Maru has many experiences on a
krill-centric ecosystem survey with physical, chemical, biological and acoustic measurement in the
Antarctic Ocean. JARPA has advantage of collecting whale data. In the same manner, the Kaiyo
Maru has advantage of collecting oceanographical and krill biological/acoustic data. It is very
valuable to study interaction of oceanography as environment structure, krill as prey species andbaleen whales as predators through both field surveys. Hence, the joint survey with mutual
strengthening was simultaneously occurred in the same area (the Area V-VI) of the Ross Sea andadjacent waters during the same period in 2004/05 (Naganobu et al., 2005; Nishiwaki et al., 2005;
Anymous, 2006).
As survey instrument and methodology have remarkably developed in recent years, we canobtain various quantity data individually for targeting subjects such as satellite, oceanography, krill
biological sampling, acoustic measurement and whales in our survey compared with the past aroundtwo decades. Antarctic krill is a key species of Antarctic marine ecosystem. Comprehensive
study of krill has been developing remarkably in recent year due to the advanced survey
methodology (e.g., Nicol ed., 2000; Watkins et al. eds. 2004). Analysis on interaction ofoceanography and krill became minutely and clearly more and more. Especially, importance of
the Southern Boundary of Antarctic Circumpolar Current (SBACC)(Orsi et al., 1995) was indicatedfor the interaction of oceanography and Antarctic krill (Nicol et al., 2000; Brandon et al., 2004;
Hewitt et al., 2004) in the recent years.
SBACC, however, is a front line. Although it is very useful to know variability of krill
distribution influenced by oceanographic dynamics, it is hard to analyze additional species of ice
krill and whales in regional and/or meso-scale like our study using the concept of SBACC only.
Then, we introduced an Integrated TEMperature mean from 0 to 200 m (ITME-200) as an
oceanographic environmental index. ITEM-200 could conveniently represent the stratified watermass of the surface layer with high primary production and living krill in the Antarctic Ocean.
Water temperature also is basically regarded as one of the most basic environmental indicators for
oceanographic structure and also marine living organisms.
Naganobu and Hirano (1982, 1986) had already provided a basic concept of an integrated
temperature mean from 0 to 200 m as an environmental index (namely Q 200) in conjunction with
distribution of Antarctic krill. Although data obtained from past discontinuous verticalobservations were hard to calculate detailed structures in the narrow range of temperature such as
the cold Antarctic Ocean, modern continuous CTD and XCTD could provide close temperature data.
Recently, Hosie et al. (2000) used integrated temperature mean (0-200 m) as the backgroundoceanographic condition to compare macro-zooplankton community structure Antarctica(80-150oE). Naganobu et al. (1995) and Thiele et al. (2000) also used the integrated temperaturemean with distribution of whales. Here, we employed ITEM-200 (changed a term from Q 200) as
an oceanographic environmental index to analysis interaction between oceanography, krill andbaleen whales.
As a result, oceanographic conditions generally indicated three water types; the Antarctic
Circumpolar Current (ACC) waters over ITEM-200 = 0 oC, the Antarctic Surface Water (ASW)
between 0 and -1 oC and the Self Water (SW) below -1 oC. ITEM-200 indicated the effective
environmental index summarized background information of oceanographic conditions. Antarctic2

krill mainly distributed in ASW and extended in SW. Ice krill clearly distributed in SW but not
ASW. Humpback whales mainly distributed ACC with high density around 0 oC and slightly
extended in ASW. Antarctic minke whales mainly distributed in ASW and SW with high density
around -1 oC. Other baleen whales (fin and blue) also were individually arranged with ITEM-200.
From our results, we showed a conceptual model of interaction between oceanography relatingwater mass and circulation pattern of the oceanic surface layer with ITEM-200, the distribution andabundance of krill (Antarctic krill and ice krill) and baleen whales (Antarctic minke whale andhumpback whale).

2. Methods
2.1 Kaiyo Maru survey
The survey area was bounded on the west and east by 160oE and 160oW and the north of 60oS
and south of around 78oS where the ship entered waters in front of the Ross Ice Shelf (Figure 1).
Bottom topography in the waters off the Ross Sea was deeper than 1000 m and until around 4000m.
Bottom topography of the Ross Sea indicated shallower than 1000 and until around 400 m as a
typical continental shelf (Figure 2).
The R/V Kaiyo Maru (2,630GT, Fisheries Agency of Japan) is a 93 m long flush-decked stern
trawler, which has capability of many kinds of oceanographic, biological, acoustic survey andothers. As she is not an icebreaker, her navigation was directly limited in the waters of sea ice. The
ship entered into the Antarctic Circle (55oS) on 24 December 2004 and went out on 26 February
2005. Then she carried over the survey south of 60oS during 26 December 2004 and 24 February2005 inquiring into the sate of sea ice. The main survey areas were the Ross Sea and its adjacentwaters between 165oE and 165oW straddling the longitude 180o south of 60oS, Antarctica (Figures 2
and 3). Transect lines along 165oE, 175oE, 180o, 175oW, 170oW and 165oW were investigated tocover hot spots where suggest high concentrated krill and whales such as the Scott Seamounts
Island, the Balleny Islands, the shelf off the Victoria Land and the almost whole of the Ross Sea.
The 175oE and 170oW lines, especially, were surveyed in detail from the surface to near the sea
bottom from 60oS to the edge of the Ross Ice Shelf on physical, chemical and biologicalparameters.
As we predicted that there would be a heavy distribution of sea ice in the Ross Sea at theplanning stage, we limited to three transect lines such as 165oE, 175oE and 180o. The sea ice,
however, melted in the almost whole of the Ross Sea during the survey period. Accordingly, thesurvey area was extended to the whole of the Ross Sea with additional transect lines such as 175oW,
170oW and 165oW with decision of the scene in consideration of the sea ice condition (Figures 3
and 4).
The survey items were as the following.
(a) Oceanographic Observation
CTD, XCTD, XBT and ADCP were used to investigate the structure of water mass
characteristics and circulation features. Stratified samples of water were made to investigate thespatial distribution of nutrient, chlorophyll a, phytoplankton and micro-zooplankton.
(b) Biological Sampling
Zooplankton, krill, micro-nekton and fishes, which are important preys for whales, werecollected using the multiple rectangular mid-water trawl (RMT(1+8)M) and other nets toinvestigate their horizontal/vertical distribution and abundance.
(c) Acoustic Survey
The multiple-frequency echo-sounder (Simrad EK-500) were used to investigate the
distribution and abundance of krill and other prey species. The acoustic survey was carried out
not along only the main transect lines but also the local grid transactions of the hot spots whichhigh concentrated krill were expected.
3

(d) Sighting Survey
The sighting surveys were conducted to investigate the distribution, abundance and ice-habitat
use of predators such as penguins, flying birds.
2.2 JARPA survey
The area for JARPA survey in 2004/05 was composed of the western part of IWC Area VI(Area VIW, 170oW-145oW) and the entire Area V (130oE-170oW) in the area between south of
60oS and the ice edge line from 7 December 2004 to 8 March 2005. One sighting vessel (SV), threesighting/sampling vessels (SSVs) and one research base ship were engaged in the research.
Kyoshin Maru No.2 (SV, 372GT) was dedicated to sighting survey and most of all experiments
were conducted by this ship. Three sighting/sampling vessels (SSVs), Yushin Maru (720GT),
Yushin Maru No.2 (747GT) and Kyo Maru No.1 (812.08GT) were engaged in sighting andsampling surveys. Nisshin Maru (8,030GT) served as a research base on which all biologicalexaminations of collected samples were conducted.
Total searching distance of one SV and three SSVs was 18,712.0 n.miles. Out of 1,049 schools(3,045 individuals) in the primary sightings of Antarctic minke whales by SSVs, 487 schools (1,167
individuals) were targeted for sampling. A total of 440 individuals were sampled. The survey
included (a) experiments for whales (sighting distance and angle experiment, photo-identification
experiment and biopsy sampling), (b) oceanographic and acoustic survey (EPCS, XCTD, CTD anda scientific echo sounder EK-500) and (c) biological research. The analysis of this paper used thedata on density index of baleen whales by the sightings and sex and reproductive status of sampled
Antarctic minke whales in order to combine with the Kaiyo Maru’s data.
2.3 Satellite information
In order to take a synoptic view of the Ross Sea waters during the survey period, satellite
information was summarized on the following items;(a) the distribution of sea ice edges between 31 January 2004, 24 and 31 January 2005 (arranged
by Weather and Marine Consultant Inc.),(b) a satellite sea image on 30 January 2005 from www.polar.org/sat_image/,(c) sea surface temperature by a satellite image on 20 February 2005 (AMSR-E,
http://www.remss.com).
(d) sea surface height by a satellite image from OPEX/POSEIDON(T/P), Geosat
Follow-On(GFO) and ERS-2 altimeter data on 20 February 2005, and(e) monthly mean of oceanic chlorophyll concentration (mg / m3) during February 2005 by
SeaWiFS data from Ocean Color Website, http://oceancolor.gsfc.nasa.gov/.
2.4 Introducing of an integrated temperature index and GIS
The purpose of the present study was to find an oceanographic condition, distribution of krill as
prey, and baleen whales as predators, and to examine interactions between those. We introduced
Integrated TEMperature mean from 0 to 200 m in depth Z (ITME-200) as an oceanographic
environmental index,
ITEM-200 = 1/200 ∫2000(temperature)dz .

The reasons why ITEM-200 was introduced were as follow. Water temperature is basicallyregarded as one of the most basic environmental indicators for oceanographic structure and also
marine living organisms. ITEM-200 could conveniently represent the stratified water mass of thesurface layer constituting of the Antarctic Surface Water, the Warm Deep Water and the Shelf
Water in the survey waters during austral summer season for discussing with biological distribution.
Naganobu and Hirano (1982, 1986) had already instituted the basic concept of integrated
temperature mean from 0 to 200 m as an environmental index (namely Q 200) in conjunction with
distribution of Antarctic krill. Although their papers were described shortly, those comprised key
4

results in the regional and whole scale of the Antarctic Ocean. They expressed that the use of theindex should be understood not only absolute value but also gradient of its distribution pattern,
noticing seasonal change of the surface layer in the Antarctic Ocean (Rintoul et al. 1997; Sokolov
and Rintoul, 2003). Data obtained from discontinuous vertical observations in the past years were
hard to calculate detailed structures in the narrow range of temperature in the cold Antarctic Ocean.
However, the present survey obtained oceanographic detailed data by modern methodology canprovide closer analyses on relationships between ITEM-200 and Antarctic minke whales comparedwith Naganobu et al. (1995) examined in the past.
Accordingly, we introduced ITEM-200 as the oceanographic environmental index to investigate
interaction between krill and baleen whales with oceanographic structure integrating detailed
various data by our survey in this time. In the recent years, Hosie et al. (2000) applied an
integrated temperature mean from 0 to 200 m as background of oceanographic structure in
conjunction with distribution of Antarctic krill and other zooplanktons and Thiele et al. (2000) also
used the integrated index for cetacean distribution off east Antarctica (80-150oE).
In addition, we mainly used a computer software of Geographical Information System, “Marine
Explore, Version 4.3”, produced by Environmental Simulation Laboratory Inc. for unified mappingand overlaying analyses of the present study.

3. Results
3.1 Oceanographic environment
3.1.1 Satellite information
Satellite information is helpful to know the background of oceanographic environment such assea ice, sea surface temperature, current and phytoplankton in the field survey area. The satellite
information in the Antarctic Ocean is very effective because the existing of sea ice and icebergs
interrupts survey activities by a ship. In particularly, sea ice in the Ross Sea varies not only
seasonal but also yearly condition. We actually changed the survey plan from an original narrow
area along 175oE to a whole area in the Ross Sea because of the large melting of sea ice.
Figure 3a shows the comparison of the distribution of sea ice edges in the Ross Sea area
between 31 January 2004, 24 and 31 January 2005. The figure indicated that the sea ice during thesurvey in 2005 melted larger than the last year on the same day, 31 January. Although there was asmall open sea along 175oE south of 72-25oS in 2004, the open sea extended over the whole Ross
Sea. On the other hand, the sea ice edge on 31 January has changed regionally compared with 24
one week ago. Figure 3b shows a satellite image on the Ross Sea on 30 January 2005. The sea
ice almost melted in the whole Ross Sea north of the Ross Ice Shelf but huge icebergs remained in
the southwest area. The sea ice remarkably varied during the short period in such way and directly
affected our non-icebreaker ship’s activities.
Figure 3c shows sea surface temperature by a satellite image on the Ross Sea on 20 February
2005. The sea ice almost melted in the whole Ross Sea north of the Ross Ice Shelf. There wasthermal zonation from the northern warmer north water to the southern cold water. High gradientof thermal zonation distributed during 60oS and 65oS around the frontal zone of the Southernboundary of the Antarctic Circumpolar Current. In the Ross Sea, the western waters were warmer
than the eastern waters on the whole except the costal waters along the eastern continent.
Figure 3d shows sea surface height by a satellite image from OPEX/POSEIDON(T/P) on 20
February 2005. Flow indicated large pattern the areas between 150oE-160oE, 165oE-175oE and
175oW-140oW in the coastal and shelf slope waters rather than the offshore. The shelf slope
waters during 175oW-165oW indicated a clockwise strong eddy which suggested upwelling. The
anticlockwise eddies which suggested down-welling were distributed south of the clockwise eddy.
These turbulent flow waters might contribute primary production.
5

Figure 3e shows monthly mean of oceanic chlorophyll concentration (mg / m3) during February2005 by SeaWiFS data. The figure was integrated the fragments of data in the un-clouds during
February. The high chlorophyll concentration distributed around the waters of 70oS south of 65oS
where roughly coincided with the Southern Boundary of ACC and the shelf slope. The figuresuggested macro distribution of phytoplankton during the survey period. oC
3.1.2 Oceanographic structure
Vertical distribution
Figure 4a shows vertical section of temperature from the surface to near bottom, the deepest
4000 m from 60oS to the Ross Ice Shelf located at around 78oS along 175oE. The upper layer
between 0 and 500 m was enlarged on scale compared with the downward layer below 500 m. An
upper graph of the figure 4a shows the mean of mean from 0 to 200 m (ITEM-200) as anenvironmental index.
Considering from existing general knowledge, main water masses appeared in the present
survey were generalized as follows: (i) the Antarctic Surface Water (ASW); this water mass isclassified to the Summer Water over seasonal thermocline and the Winter Water indicating underthe value of 0 oC, (ii) the Warm Deep Water (WDW); this water shows high temperature andsalinity maximum indicating below the above ASW, and (iii) the Shelf Water (SW); this water is
especially called in the case that ASW exists from the surface to near the bottom on the Antarctic
continental shelf such as the Ross Sea.
In order to examine relationships between water masses and biological distribution we used
ITEM-200 as environmental index as mentioned in the methods section. ITEM-200 can simply
summarize stratified water masses. The upper graph of Figure 4a shows ITEM-200 calculated
adjusting the lower figure. The graph indicated a north-south gradient of the upper layer
temperature.
The around 3 oC line calculated from the warmer water in the Antarctic Circumpolar Current
during 60-62oS abruptly dropped down to 64oS. This dropping line coincided with the so-called
Southern Boundary of the Antarctic Circumpolar Current (SBACC) identified by Orsi et al. (1995).
The line during 64-70oS indicating the thick ASW (0-150 m) and its lower WDW (150-200 m)
stayed between approximately 0 and -1 oC. The line south of 70oS dropped less than -1 oC withincreasing the thick of ASW except the so-called Antarctic Divergence around 72-10oS whereindicated upwelling of WDW. SW above the continent shelf South of 73oS showed approximately-1 oC and/or less than -1 oC. ITEM-200 on the continental shelf indicated relatively warmer
because of thicker summer surface water above the seasonal thermocline and intrusion of WDW
into the continental shelf waters.
Figure 4b and 4c shows vertical sections f salinity and density respectively from the surface tonear bottom between 60oS and the Ross Ice Shelf along 175oE as well as temperature. Steep north–south gradients of salinity and density distributed during 63-65oS. Lower salinity less than
33.8psu and lower density less than 27.2 distributed during 66-70oS because of probably ice melting
water. Higher salinity than 34.2psu and higher density than 27.6 indicated in the surface layer(0-100 m) at the Antarctic Divergence zone during 71-30oS and 73oS. High salinity and density
suggested strong upwelling of WDW. In the Ross Sea there was also higher salinity and density
suggesting upwelling to the surface layer during 75-76oS. High salinity than 34.7psu and density
than 27.9 existed on the shelf bottom.
Figure 4d shows vertical section of geostrophic current from the surface to referenced level
depths (1000 db and 400 db) between 60oS and the Ross Ice Shelf along 175oE. On the whole,slow eastward flow and westward flow less than 2cm/sec distributed alternated along thenorth-south line except strong eastward flow (a maximum core 13cm/sec) estimated during 61-65oS.
The relatively strong eastward flow showed along the continental slope at the Antarctic Divergencezone during 71-30oS and 73oS.

6

Horizontal distribution
Figure 5 shows horizontal distribution of ITEM-200 as the environmental index in the wholesurvey waters. A pattern of north-south thermal zonation indicated from a warm isopleth of 8 oC
along 55oS to a cold isopleth of -1.5 oC on the continental shelf with meander. The thermal zonation
during 8 oC and 0 oC indicated steep a north-south gradient. The zonation south of 0 oC indicated agentle gradient. The tongue-like water along 175oW indicated southward advection and cold water
during 175oE-180o remained northward during the 0 oC and -1 oC isopleth with meander. On theRoss continental shelf, the cold core water less than -1.5 oC distributed to the east and relatively
warmer to the west. This distribution figure of ITEM-200 would be used as the basic
environmental index for considering various biological distributions.
The ITEM-200 integrated water temperature columns would be reflected flow patterns roughly.
To add flow information makes the actual use of ITEM-200 more clear. Figure 6a shows
geopotential anomaly at 10 db level relative to 1000 db with the bottom topography in the waters
deeper than 1000 m. Figure 6b also shows geopotential anomaly at 10 db level relative to 400 db
with the bottom topography in the shallow continental shelf waters.
A steep gradient of eastward isopleths north of 65oS in Figure 6a indicated strong current in the
Antarctic Circumpolar Current (ACC). A gentle gradient of southward isopleths south of 65oS
suggested sluggish movement of the thick ASW to the south. Distribution pattern of isopleths in
Figure 6b suggested southward advection of the oceanic waters and clockwise circulation of water.
Clockwise eddies also suggested upwelling of deeper water. These flow patterns might affect large
melting of sea ice in the waters in the survey year.
3.2 Marine biological gradients
3.2.1 Primary production
Figures 7a, 7b and 7c show vertical section of total chlorophyll a from the surface to 200 m
along 180o, 175oE and 170oW respectively. Along 180o, relative high chlorophyll a (1.0-2.5 ㎍L-1)
appeared shallower than 50 m south of 64oS and the maximum near the waters of sea ice edge.
Along 175E, relative high chlorophyll a (1.0-2.0 ㎍L-1) appeared shallower than 40 m from 63-30oS
to 68oS, and around 74oS where roughly coincided with the melting waters of sea ice. Along
170oW in the Ross continental shelf, relative high chlorophyll a (1.0 ㎍L-1 and up) appeared as
patchy distribution shallower than approximately 50 m from 63-30oS to 68oS, and around 74oS near
the Ross Ice Shelf.
Figure 8 shows horizontal distribution of integrated chlorophyll a (mg m-2) from the surface to
200 m in the whole survey area with ITEM-200. Although there was a time lag during the surveyoperiod, on the whole, relative high chlorophyll a appeared in the waters of ITEM-200 = 0 C whereroughly coincided with SBACC and the melting marginal waters of sea ice. In the Ross continental shelf,
chlorophyll a along 170oW showed higher compared with 175oE. The differences between the westernoowaters (170 W) and the eastern waters (175 E) might depend on the melting timing of sea ice and water
circulation.

3.2.2 Krill abundance
There is little information of krill abundance in the Ross Sea except Azzali and Kalinowski(2000) that was limited in the regional scale. Figure 9 shows distribution density of krill (E.
superba and E. crystallorophias)(g/m2) in the whole survey waters by Kaiyo Maru. The samples
from Kaiyo Maru’s RMT and stomach contents of Antarctic minke whales indicated that two
euphausiid species, E. superba and E. crystallorophias showed different distribution patterns in thesurvey waters. E. superba distributed in the oceanic waters north of the -1°C isopleth of
ITEM-200 where nearly coincided with the deeper depth than 1000 m of the bottom topography.
E. crystallorophias distributed on the continental shelf region south of the -1°C isopleth of
ITEM-200 where coincided with shallower depth than 1000 m. Based on their distribution
patterns, the survey area was divided into two strata to estimate the biomasses of two species.
7Kaiyo Maru conducted the echo sounder survey using EK500 (Simrad). In the study, thedifference between the mean volume backscattering strength (ΔMVBS) of 120 and 38 kHz fell
between 2 and 16 dB was classified as krill. Details of the acoustic survey were described in
Murase et al. (2006). Figure 9 showed that high density of E. superba was observed in thenorthwestern waters in the survey area. E. crystallorophias tended to distribute at small clockwise
eddies suggested upwelling and near the ice shelf. Biomass densities of E. superba and E.
crystallorophias estimated were 5.36±7.45 g/m2 and 3.44±1.96 g/m2, respectively. The biomassesof E. superba and E. crystallorophias in the present study were estimated as 2.04 (CV = 0.44) and1.26 (CV = 0.21) million ton, respectively (Murase et al. 2006).
3.3 Interactions between the oceanography, krill and whales
3.3.1 Oceanography - krill
Figure 10a shows distribution of Antarctic krill (Euphausia superba) in routine trawls (0-200 m)
with ITEM-200. Although appearance frequency of E. superba by routine trawls was 36% in thewhole survey scale, it was 100% in the waters between the 0 oC and -1 oC isopleths of ITEM-200
except one station in the waters of the -1.5 oC isopleth in the Ross continental shelf. High densityof E. superba sampled coincided with steep north-south gradients of 0 the 0 oC and -1 oC isopleths
respectively. The steep north-south gradients of the 0 oC and -1 oC isopleths might understand as
the Southern Boundary of ACC and a general continental slope front respectively.
Figure 10b shows distribution of ice krill (Euphausia crystallorophias) in routine trawls (0-200m) with ITEM-200. Appearances of E. crystallorophias sampled only limited in the waters lower
than -1 oC in the Ross continental shelf. E. crystallorophias was distributed all around in thecontinental shelf waters except all 3 sampling sites during 73-75oS along 170oW. Maximum
density appeared near the Ross Ice Shelf at 78-30oS in the southeast part. On the other hand, noappearances were in the warmer waters north of the -1 oC isopleth.
Figure 10c shows appearances of Antarctic krill (E. superba) by trawls below 200 m with
ITEM-200. As each trawling site differenced a sampling depth, it was difficult to compare witheach proportion of caught density. However, appearance and/or non-appearance of caught species
have meaningful knowledge. E. superba appeared at most sampling sites in the continental shelfwaters except the site near the Ice Shelf along 170oW. This result pointed up the difference fromthe routine trawls (0-200 m) (Figure 10a) indicated only one appearance site. Non-appearances
south 74oS long 175oW coincided with the result of the routine trawls. This result suggested
non-distribution of E. superba in the southwestern waters in the Ross Sea.
Figure 10d shows appearance s of ice krill (E. crystallorophias) by trawls below 200 m with
ITEM-200. This result of appearance was common to the routine trawls (Figure 10b).
Appearances of E. crystallorophias limited south of the -1 oC isopleth and existed in the westernwaters along 175E. Non-appearance was north of the -1 oC isopleth. Geographical distributionof E. crystallorophias spread throughout the Ross continental shelf waters.
3.3.2 Oceanography - whales
Figure 11a shows distribution density of Antarctic minke whales (Balaenoptera bonaerensis)(number of schools sighted per 100 n. miles) with ITEM-200. The distribution of Antarctic minke
whales ranged through south of the 1 oC isopleth. Relative high density index of Antarctic minke
whales concentrated at the steep gradient around the 0 oC and south of the -1 oC isopleths. In
addition, the density index indicated higher in the tongue-shaped southward advection along 175oW
between 0 and -1 oC and the tongue-shaped northward advection along 170oW. The relative highdensity coincided with the tongue-shaped advection with north-south meander. High density
indexes especially concentrated in the waters with eddies around 75oS along 170oW.
Figure 11b shows distribution density of Antarctic minke whales (number of individuals sighted
per 100 n. miles) with ITEM-200. Although the distribution of individual density indices basicallywas the same pattern as school density, individual density remarkably indicated high in the8tongue-shaped northward advection. The relative high density distributed in the tongue-shaped
southward advection suggested that the whale migrated to the southern colder shelf water indicatedits high density.
Figure 11c: Positions of sampled Antarctic minke whales by sex and reproductive status
with ITEM-200. There was difference of distribution between males and females. Mature
males concentrated around and north of the -1 oC except several positions in the self waters.
No immature males were sampled. Mature females distributed thorough the whole waters
sampled and relatively concentrated in the shelf waters. Immature females mainly distributedin the waters around and north of the -1 oC except two positions near the continent and ice shelf.
Differences of distribution between sex and reproductive status were recognized depending on
the condition of waters.
Figure 11d shows distribution density of humpback whales (Megaptera novaeangliae) (numberof schools sighted per 100 n. miles) with ITEM-200. The distribution of humpback whale clearlyranged through north of the 0.6 oC isopleth. The high density indexes concentrated at the frontal
zone around the 0.5 oC isopleth. There are no appearance of humpback whales in the relative
colder waters south of the 0.6 oC isopleth.
Figure 11e shows distribution density of fin whale (Balaenoptera physalus) (number of schoolssighted per 100 n. miles) with ITEM-200. The distribution of fin whales ranged north of thearound 0 oC isopleth and especially indicated higher at around 61oS and 170oE. Although one
exemption appeared at around 70oS and 175oE, this suggested that fin whales migrated in the
tongue-shaped southward advection along 175oE. Although the distribution of fin whales wasvery similar to humpback whales in latitudinal zone, both distributions slightly differed from eachother in longitudinal direction.
Figure 11f shows distribution density of blue whale (Balaenoptera musculus) (number ofschools sighted per 100 n. miles) with ITEM-200. Although only 3 appearance sites of bulue
whales were observed, the appearance stopped at the -1 oC isopleth. Both of one appearance site at
the 0 oC and 2 sites at the -1 oC were distributed in the waters of tongue-shaped southward advection.
This suggested that blue whales migrated in the tongue-shaped southward advection along 175oW.

4. Discussion
The purpose of the work was to find an oceanographic condition, distribution of krill as prey,and baleen whales as predators, and to examine interactions between those. The results indicatedclose interactions between the oceanographic condition, krill and whales. The oceanographic
condition of the surface layer was summarized as ITEM-200. Distribution of ITEM-200D wasused as background information for comparing with distribution patterns of each species.
Figure 12 shows conceptual model relating water mass and circulation pattern of the oceanic
surface layer with ITEM-200, the distribution and abundance of krill (Antarctic krill and ice krill)and baleen whales. (Antarctic minke whale and humpback whale). Abbreviations indicate as thefollows. ACC; the Antarctic circumpolar current, ASW; the Antarctic surface water, SW; theshelf water, SBACC; the southern boundary of ACC, ANK; Antarctic krill, ICK; ice krill, MIW;
Antarctic minke whale , and HUW; humpback whale. Each line in the map indicates the Southernboundary of Antarctic Circumpolar Current (SBACC) (from Orsi et al. 1995) and ITEM-200 = 0
and -1 oC. A 1000 m shows the bottom line. Arrows show flow patterns.
Figure 12 summarized the result of interactions between oceanographic conditions, krill andbaleen whales through the present survey. The oceanographic conditions generally indicated threewater types; ACC waters over ITEM-200 = 0 oC, ASW between 0 and -1 oC and SW below -1 oC.
An Eastward Arrow indicated strong eastward flow in ACC. Southward arrows suggested
southward flows in ACC and ASW. Clockwise and anticlockwise arrow suggested eddies withupwelling and down-welling in SW. ITEM-200 isopleths indicated north-south meandering shape.
9We also refer to recent oceanography results (e.g., Picco et al., 2000; Russo, 2000). We discuss
the results of the interaction between oceanographic conditions, krill and baleen whales from thefollowing viewpoints.
Firstly, ITEM-200 was considered as the effective environmental index that was summarizedbackground information of oceanographic conditions. Antarctic krill mainly distributed in ASW
and extended in SW. Ice krill clearly distributed in SW but not ASW. Overlap between
Antarctic krill and ice krill was shown in the shifting waters from ASW to SW around -1 oC.
Humpback whales mainly distributed ACC with high density around 0 oC and slightly extended in
ASW. Antarctic minke whales mainly distributed in ASW and SW with high density around -1 oC.
Overlap between humpback whales and Antarctic minke whales was in the shifting waters from
ACC to ASW around 0 oC.
Secondly, ITEM-200 would be used as a quantitative environmental index for the past relative
analyses. Murase et al. (2002) showed the relationships between distributions of krill and baleen
whales in the Indian sector of the Antarctic Ocean. Matsuoka et al. (2003, 2006) indicated thesegregation of humpback whales around the waters of SBACC and Antarctic minke whales aroundthe waters of ice-edge and over the continental shelf slope. The relationships between distributionof krill, whales and ITEM-200 could give the quantitative information adding to their result.
Murase et al. (2006) used ITEM-200 to identify the boundary of distribution of Antarctic krill andice krill for biomass estimation using acoustic data in our surveys. A stomach content study ofbaleen whales is a key approach for understanding the interaction of krill as prey and Antarctic
minke whales as predators (Ichii, 1990; Ichii et al., 1998). Tamura et al. (2006) effectively used
ITEM-200 as environmental index to compare stomach content of sampled Antarctic minke whales
and net sampling in the local waters in our surveys. On the other hand, Reilly et al. (2004) studiedbaleen whales on biomass and energy transfer through a biological oceanography survey in theSouth Atlantic sector of the Antarctic Ocean. It is interested in applying our approach to the otherwaters.
Thirdly, the essential interaction between ITEM-200 as environmental index, krill as preys andbaleen whales as predators would apply to other Antarctic waters. Hosie et al. (2000) and Thiele
et al. (2000) used integrated temperature mean (0-200 m) as the background oceanographic
condition to compare macro-zooplankton community structure and whales off east Antarctica(80-150oE) respectively. Although their result basically coincided with the Ross Sea survey’s
one, .there was a difference of regional feature. The space (ASW) during 0 and -1 oC off the Ross
Sea was four times as wide as east Antarctica. This oceanographic condition reflected biologicaldistribution of krill and whales.
On the other hand, Nicol et al. (2000) and Chiba et al. (2000) emphasized the importance of
SBACC and the Antarctic Divergence respectively in structuring Antarctic marine ecosystems offeast Antarctica (Wakatsuchi et al. 1994),.
Murase et al. (2006) examined influential
environmental factors of distribution patterns of Antarctic minke whales and suggested response to
krill. These approaches suggest interesting discussion connected with ITEM-200, krill and baleen
whales.
Fourthly, using the data of the joint surveys of Kaiyo Maru and JARPA, we overviewed various
aspects and indicated the geo-ecological interaction between oceanography through ITEM-200, krill
and baleen whales in the survey area. Doses the results apply to other Antarctic waters?
Although there would be a regional feature in the waters, the ecological interaction would becommon in the whole Antarctic Ocean. Naganobu and Hirano (1982, 1986) had already tried
geographical overlay between ITEM-200 and Antarctic krill in the regional and whole Antarctic
Ocean and indicated the similar structure as this time result, although un-sufficient data comparedwith recent survey data. Nicol (2000) edited a multidisciplinary survey of the waters off east
Antarctica. Watkins et al. (2004) also edited a multinational, multi-ship biological oceanography
survey of the Atlantic sector or the Southern Ocean. These two multidisciplinary results suggested
the common interaction between the results in the present study and the circumpolar scale. In
10addition, continuing JARPA surveys (Nishiwaki et al. (2006)) would contribute to submit sufficientwhale data. In the future, detailed analysis in regional and whole scale is required forcomprehensive understanding of the interaction between oceanography, krill and whales.
Finally, relationships between oceanography and krill distribution is a recurrent problem. Marr
(1956, 1962) and Mackintosh (1972, 1973) were certainly classical and original papers indicating
the relationships between krill distribution and water mass and current in the regional and whole
Antarctic Ocean scale using Discovery Committee’s large data since the 1930s. Deacon and
Baker (1980) indicated importance of stratified Antarctic Surface Water and Warm Deep Water for
krill distribution as an idea. Continuously, Naganobu and Hirano (1982, 1986) introduced theconcept of integrated temperature mean as oceanographic environmental index. Amos (1984) andMiller and Hampton (1989) contributed to advance the relationships in large scale of the Southern
Ocean. Recently, Nicol et al. (2000) dynamically indicated well the relationships using theconcept of SBACC. In these accumulated knowledge, ITEM-200 in the present study may
contribute as a synthesized index of oceanographic structure with biological and ecologicalgradients like a concept of bioregionalsation. Further study is required in conjunction withenvironmental, biological and ecological distribution/gradients for understanding of the Ross Sea
Ecology (Faranda et al., 2000; Pinkerton et al., 2006).
On the other hand, it is important to analyze not only interaction but also variability ofoceanography, krill and whales in the recent years. There are many oceanographic papers onvariability in the JARPA survey waters (Yabuki 2006, Watanabe et al. 2006) and variability of the
Antarctic/Southern Ocean scale (e.g., White et al. 1996; Gille, 2002; Aoki et al., 2005). Especially,
freshening of the Antarctic Bottom Water in the Ross Sea (Jacobs et al. 2002) and warming in the
Antarctic Peninsula waters (Marshall et al. 2006) should be noted. On the other hand, there arebiological papers on change of Antarctic krill (Siegel and Loeb 1995; Loeb et al. 1997; Naganobu
et al. 1999 and Atkinson et al. 2004) including predators such as birds (Croxall et al. 2002) andwhales (Fujise et al., 2006). To study correlation with these variability papers in the future, weconcentrated synoptic interaction between oceanography, krill and whales in this paper. It isneeded to find the interaction as basic structure for understanding of ecological variability.

5. Conclusions
A joint survey of the R/V Kaiyo Maru and the Japanese Whale Research Program under Special
Permit in the Antarctic (JARPA) was carried out to study the interaction between an oceanographic
condition, distribution of krill as prey, and baleen whales as predators in the Ross Sea and its
adjacent waters, Antarctica in austral summer of 2004/05.
The results indicated close interactions between the oceanographic condition, krill and whales.
The oceanographic condition of the surface layer was summarized as the oceanographic
environmental index ITEM-200. Distribution of ITEM-200 was used as background information
for comparing with distribution patterns of each species. Antarctic krill distributed mainly in the
Antarctic Surface Water (ASW) area (ITEM-200 = 0 to -1 oC) and extended in the Shelf Water(SW) area (less than -1 oC) Ice krill clearly distributed in SW but not ASW. Overlap between
Antarctic krill and ice krill was shown in the shifting waters from ASW to SW around -1 oC.
Humpback whales mainly distributed in the Antarctic Circumpolar Current (ACC) waters with highdensity around 0 oC near Southern Boundary of ACC and slightly extended in ASW. Antarctic
minke whales mainly distributed in ASW and SW with high density around -1 oC in a continental
shelf slope frontal zone. Overlap between humpback whales and Antarctic minke whales were in
the shifting waters from ACC to ASW around 0 oC. The interaction between distribution of krill,whales and ITEM-200 could give the quantitative information to identify the boundary of
distribution of Antarctic krill and ice krill for biomass estimation using acoustic data in the surveys.
We finally summarized a conceptual model of interaction between oceanography relating water11

mass and circulation pattern of the oceanic surface layer with ITEM-200, the distribution andabundance of krill and baleen whales.

Acknowledgements
The authors would like to thank the captain J. Doi and all the crew of the R/V Kaiyo Maruand the captain D. Tohyama and all the crew of the Nissin Maru fleet supporting the surveys in theRoss Sea waters. We thank to Messrs. K. Korenaga, T. Usami, K. Iwasaki, and Mses. M. Shinkai
and A. Matsumoto for their contribution supported the Kaiyo Maru survey. We thank Drs. S.
Kawahara, S. Sawamoto, K. Furuya, T. Suga, K. Miyashita, K. Kuma, K. Iida, T. Ishimaru, and T.
Iwami for their professional supports. We are indebted to the staffs involved of National ResearchInstitute of Far Sea Fisheries and Institute of Cetacean Research. We are grateful to theGovernment of Japan provided regulative and financial support for the research. We also wish to
thank the members of the Scientific Committee for the Conservation of Antarctic Marine Living
Resources for their helpful suggestion.

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15

Figure 1: Transect lines and stations by research items of the R/V Kaiyo Maru during 26 December 2004 and 24
February 2005.
160°
E
60°
S

170°
E

170°
W

180°

160°
W
60°
S

65°
S

65°
S
3000m

3000m
3500m
3500m

4000m

2500m

70°
S

70°
S

ANTARCTICA

4000m

3500m

2500m
3000m

2000m

400m

75°
S

75°
S

1500m
1000m

500m

400m

500m

Ross Ice Shelf

160°
E

170°
E

Bottom Topography (m)

180°

170°
W

160°
W

Figure 2: Bottom topography off and of the Ross Sea.

16

Figure 3a: Comparison of the distribution of sea ice edges in the Ross Sea area between 31 January 2004 (red line),24 (blue line) and 31 (black line) January 2005. The sea ice during the survey in 2005 melted larger than the lastyear on the same day. The sea ice edge on 31 January has changed regionally compared with 24 one week ago.

Figure 3b: A satellite image on the Ross Sea on 30 January 2005. The sea ice almost melted in the whole Ross Sea
north of the Ross Ice Shelf. from www.polar.org/sat_image/.

17

120‹E

150‹

180‹

150‹

120‹

90‹
10

60‹S

5

70‹

0
-2

80‹
Figure 3c: Sea surface temperature by a satellite image on the Ross Sea on 20 February 2005. The sea ice almost
melted in the whole Ross Sea north of the Ross Ice Shelf.

150‹E

160‹

170‹

180‹

170‹

160‹

150‹

140‹

60‹S
100
50

65‹
0
-50
-100
-150

70‹

cm

75‹

100cm/sec

Figure 3d: Sea surface height by a satellite image from OPEX/POSEIDON(T/P), Geosat Follow-On(GFO) andERS-2 altimeter data on 20 February 2005.

18

120‹E

150‹

180‹

150‹

120‹

90‹
100

60‹S
10

70‹

1

0.1

0.01

80‹
Figure 3e: Monthly mean of oceanic chlorophyll concentration (mg / m3) during February 2005 by SeaWiFS datafrom Ocean Color Website, http://oceancolor.gsfc.nasa.gov/.

19

C)
ITEM-200 ( °

4
3
2
1
0
-1
-2
60

62

64

60°
S

66

68
70
Latitude72

74

Latitude
70°
S

65°
S

76

78 ( S )
°

75°
S

78°
S
0

-0.5

3.5

-1

-1.5

100

-0.5

3

-1

0

-1.5

0.5

200

2

2.5

1

2.5

-1.5

1.5

1.5

300
3

Depth

400
0

3

500

-1

-1

0

0

3

1000

CTD

1

XCTD
2000

0.5

Temperature (°C)°
ALONG 175 E
3 - 27 JAN. 2005
R/V KAIYO MARU

3000

4000
-2

0

2

4°
C

Figure 4a: Vertical section of temperature from the surface to near bottom between and the Ross Ice Shelf along
175E. An upper graph shows the mean of integrated temperature between the surface (0) and 200 m as anenvironmental index (ITEM-200) introduced by Naganobu and Hirano (1982). SBACC: the Southern Boundary of
the Antarctic Circumpolar Current.

20

60°
S

Latitude
70°
S

65°
S

34.0

33.8

34.0

33.4 33.6

33.8
34.0

75°
S
34.2

78°
S

34.6

34.2

100

34.4

34.4
34.6
34.0

200

34.7

300

34.6

34.2
34.7

400
Depth

34.0

33.8
34.0
34.2

34.4 34.6
34.7

500
CTD

1000

XCTD
2000
34.7

Salinity ( psu )ALONG 175°E
3 - 27 JAN. 2005
R/V KAIYO MARU

3000

4000
33.2

34.0

34.8

(psu)

o

Figure 4b: Vertical section of salinity from the surface to near bottom between 60 S and the Ross Ice Shelf alongo
175 E.
60°
S

Latitude
70°
S

65°
S
27.0

27.4

27.2

27.0

100

75°
S

27.4

78°
S

27.8
27.6

27.6

27.6
27.2

200

300

27.9

27.9
27.8

Depth

400

27.4

500
1000

27.6

CTD
XCTD

2000

27.8

Density (sigma-t, kg/m 3 )ALONG 175 E °3 - 27 JAN. 2005
R/V KAIYO MARU

3000

4000
26.6

27.0

27.4

27.8
(kg/m3)oFigure 4c: Vertical section of density from the surface to near bottom between 60 S and the Ross Ice Shelf alongo
175 E.

21

Figure 4d: Vertical section of geostrophic current from the surface to referenced level depths (1000 db and 400oodb) between 60 S and the Ross Ice Shelf along 175 E. Positive values indicate the eastward velocity and negative
westward.

22

160°
E

55°
S

170°
E

8

180°

170°
W

160°
W

7
6
5
4

60°
S

3
3

2
1

65°
S

0.5
0
-0.5

70°
S

-1

75°
S

-1.5

80°
S

-2 0

2

4 6

8 10 ( °C)

Figure 5: Horizontal distribution of integrated temperature (0-200 m) （ITEM-200）. Bullets (•) indicate theobserved sites.

23160°E
60°S 3000m

170°E

180°

170°W

160°W
60°S

0.70
0.60
3000m

0.50

65°S

65°S
0.33

0.40
0.35

70°S

70°S

500m

75°S

75°S

3000m
1000m
500m

1000m

160°E

170°E

180°

170°W

160°W

Figure 6a: Geopotential anomaly (m2s-2) at 10 db level relative to 1000 db with the bottom topography. Bullet (•)
indicates the observed sites.
165°E
70°S

170°E

175°E

180°

175°W

170°W

165°W

160°W

500m

71°S

155°W
70°S
71°S

1000m

72°S

72°S
1000m
400m

73°S

400m

74°S
500m

75°S

73°S

500m

500m

400m

74°S
1.4

75°S

1000m

1.2

76°S

1.6

1.4

500m

77°S

76°S

1.8

1.0

1.6

500m

77°S
1.6

1.4

78°S

400m

78°S

1.8
2.0

79°S
165°E

500m

170°E

175°E

180°

175°W

170°W

165°W

160°W

79°S
155°W

Figure 6b: Geopotential anomaly (m2s-2) at 10 db level relative to 400 db with the bottom topography. Bullet (•)
indicates the observed sites.

24

160°E
60°S

170°

180°

170°

160°
ITEM-200
4

65°

2

0

0

70°

-2

-1

E. superba
300

75°

150
10

E. crystallorophias
100
50
10

80°

Figure 9a: Distribution and density (g/m^2) of krill; E. superba and E. crystallorophias by the acoustic survey
with ITEM-200.

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°
E. superba
10
5
1

80°
Figure 10a： Distribution of Antarctic krill (Euphausia superba) in routine trawls with ITEM-200. Abundancecircles are proportional in area to density (individuals 1000 m-3). × sampling sites where no specimens where
were caught.
27

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°
E. crystallorophias
100
50
10

80°

Figure 10b： Figure 12a： Distribution of ice krill (Euphausia crystallorophias) in routine trawls with ITEM-200.
Abundance circles are proportional in area to density (individuals 1000 m-3). ×sampling sites where no
specimens where were caught.
160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°

80°

Figure 10c： Appearance s of Antarctic krill (Euphausia superba) below 200 m with ITEM-200. Abundancecircles are proportional in area to density (individuals 1000 m-3). ×sampling sites where no specimens where
were caught.

28

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°

80°

Figure 10d： Appearance s of ice krill (Euphausia crystallorophias) below 200 m with ITEM-200. Abundancecircles are proportional in area to density (individuals 1000 m-3). ×sampling sites where no specimens where
were caught.
160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°

Minke whale (schools)
1
0.7
0.3

80°

Figure 11a: Distribution of Antarctic minke whale (Balaenoptera bonaerensis) with ITEM-200. Abundancecircles are proportional in area to density (number of schools sighted per 100 n. miles). A black mark (・) indicatesnaught.

29

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°

Minke whale (individuals)
5
3
1

80°
Figure 11b: Distribution of Antarctic minke whale (Balaenoptera bonaerensis) with ITEM-200. Abundancecircles are proportional in area to density (number of individuals sighted per 100 n. miles). A black mark (・)indicates naught.

160°E
60°S

170°

180°

170°

160°

65°

70°

0

Minke whale-1♂ Immature

75°♂ Mature♀ Immature♀ Mature

80°
Figure 11c: Positions of sampled Antarctic minke whales by sex and reproductive status with ITEM-200.

30

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°
Humpback whale
0.7
0.5
0.2

80°

Figure 11d: Distribution of humpback whale (Megaptera novaeangliae) with ITEM-200. Abundance circles areproportional in area to density (number of individuals sighted per 100 n. miles). A black mark (・) indicatesnaught.

160°E
60°S

170°

180°

170°

160°

65°

70°

0

-1

75°

Fin whales
1
0.5
0.2

80°
Figure 11e: Distribution of fin whale (Balaenoptera physalus) with ITEM-200. Abundance circles areproportional in area to density (number of individuals sighted per 100 n. miles). A black mark (・) indicatesnaught.

31

160°E
60°S

170°

180°

170°

160°

65°

0

70°

-1

75°

Blue whales
0.03
0.02
0.01

80°
Figure 11f: Distribution of blue whale (Balaenoptera musculus) with ITEM-200. Abundance circles areproportional in area to density (number of individuals sighted per 100 n. m individuals iles). A black mark (・)indicates naught.

32

160 E
60 S

170 E

180

170 W

ACC

160 W

C
SBA

C
HUW

65 S

ASW
70 S

ANK

MIW

0

ANTARCTICA

-1

75 S

ICK

SW
1000m

Ross Ice Shelf

Figure 12: Conceptual model relating water mass and circulation pattern of the oceanic surface layer, thedistribution and abundance of krill and baleen whales. Each line in the map indicates the Southern boundary (ofAntarctic Circumpolar Current) and ITEM-200 = 0 and -1 (oC). A 1000 m bottom line is shown.
ACC: Antarctic Circumpolar Current. ASW: Antarctic Surface Water. SW: Shelf Water. SBACC: Southern
Boundary of ACC (Orsi et al., 1995). ANK: Antarctic krill. ICK: Ice krill. MIW: Antarctic Minke Whale. HUW:
Humpback Whale.

33