105Abundance Increases of Large Baleen Whales in the Antarctic
based on the Sighting Survey during
Japanese Whale Research Program (JARPA)
Koji MATSUOKA*, Takashi HAKAMADA, Hiroshi KIWADA,
Hiroto MURASE and Shigetoshi NISHIWAKIThe Institute of Cetacean Research,
4-5, Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan*e-mail: matsuoka@cetacean.jp*author for correspondence

Abstract
The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) was
designed as a large-scale, long-term monitoring program using line transect surveys. These have been
carried out in a consistent way during the austral summer every other year in the IWC (International
Whaling Commission) baleen whale management Areas IV (70°E-130°E) and V (130°E-170°W) sincethe 1987/88 season. The current research area was set in the half of the Antarctic areas located between
35 °E and 145°W in the waters south of 60°S. Major cetacean species sighted in this area were Antarctic
minke (Balaenoptera bonaerensis), humpback (Megaptera novaeangliae), fin (Balaenoptera physalus)
and blue (Balaenoptera musculus intermedia) whales. A ‘shift in baleen whale dominance’ from Antarctic minke to humpback whales, was observed in Area IV since the 1997/98 season. In the 1989/90 season, Antarctic minke biomass (382,000 tons) was higher than that of humpback whales (139,000 tons),
but after 15 years, the biomass of humpback (841,000 tons) increased to more than twice that of Antarctic minke (335,000 tons). Habitat expansion of humpback and fin whales were also observed in Area IV
from the first half (1989/90-1996/97) to the latter half of the surveys (1997/98-2003/04). At this moment,
the abundance of Antarctic minke whales is stable in Area IV, but increases in abundance and habitat
expansion of humpback and fin whales may lead to their competition with Antarctic minke whales.
Yearly changes in some biological features also suggest this ‘event’. Further monitoring surveys will be
required in order to improve baleen whale management in the Antarctic Ocean.
Key words: abundance estimate, Antarctic Ocean, IWC, JARPA, survey vessel, whales

1. Introduction
In 1904, commercial whaling began in the Antarctic. Initially, the whaling targeted mainly humpback
whales, which are slow swimmers. Later, target species shifted to the blue, fin, sei and Antarctic minke
whales one after another as the target whale stocks
were reduced. Whaling of humpback, blue and fin in
the Antarctic was banned in 1963, 1964 and 1974,
respectively (Fig.1).
The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) was designed asa large-scale, long-term monitoring line transect survey. It has been carried out in a consistent way every
other year in Areas IV and V since the 1987/88 season
during the austral summer season. After a season offeasibility research (1987/88 in Area IV and 1988/89
Global Environmental Research9(2)/2005: 105-115
printed in Japanin Area V), full-scale research has been conductedsince the 1989/90 season. Also, additional surveys
were conducted once a year alternately in the easternpart of Area III (IIIE) and the western part of Area VI(VIW) to investigate the stock of Antarctic minke
whales from the 1995/96 season. The sighting procedures followed the method used in the IWC/IDCR(International Whaling Commission/ International
Decade for Cetacean Research) and SOWER (Southern Ocean Whale and Ecosystem Research) cruises asmuch as possible. In the research areas, the Antarctic
minke whale was the dominantly sighted species
through the surveys from the 1987/88 to the 2002/03
seasons. Major cetacean species sighted in this area
were Antarctic minke, humpback, fin and blue whales(Fig.2a-2d). The latest abundance estimates of these
species based on the JARPA were presented to the©2005 AIRIES106

K. MATSUOKA et al.

Fig. 1 Total biomass of harvested large baleen whales in the Antarctic since 1904.

(a)

(b)

(c)

(d)

Fig. 2 Photogaraphs of the whales in the Antarctic. (a) Antarctic minke whales, (b) humpback whales,(c) fin whales, (d) blue whales.

JARPA review meeting called by the Goverenment ofJapan, Tokyo, 18-20 January 2005. An abundance ofAntarctic minke whale was reported by Hakamada etal. (2005), and abundance of humpback, fin and blue
whales was reported by Matsuoka et al. (2005) at thismeeting.

2. Surveys and Data Collection
2.1 Research area covered
The research area was set based on the IWC Antarctic Areas for baleen whale species (except Bryde’s
whale). The area from south of 60°S to the ice-edge in
the Areas IIIE (35°E-70°E), IV (70°E-130°E), V(130°E-170°W) and VIW (170°W -145°W) comprised
for the JARPA research area (Fig. 3). Each Area of IV
and V was divided into two sectors (western sector
and eastern sector). Each sector was also divided into
two strata (northern and southern strata), the 60°S
latitude line to the line of 45 n.miles from the ice-edge(northern stratum), and the ice-edge to 45 n.miles

Fig. 3 Research area of the JARPA (red colored),in the IWC Antarctic Areas for the
management of baleen whale species(except Bryde’s whale).

Abundance of Large Baleen Whales based on the Sighting Survey in JARPA

from the ice-edge line (southern stratum) except for
the Prydz Bay and the Ross Sea regions. The Prydz
Bay region was defined as south of 66°S and the Ross
Sea was defined as south of 69°S. As an exception, in
the 1999/2000 and 2001/02 seasons, the northernboundary of the research area was set at 58°S in Area
III east from a strategic view point regarding Antarctic
minke distribution. There were no stratifications ofAreas IIIE and VIW. Details of the sighting procedures are given in the review of the sighting survey in
the JARPA (Nishiwaki et al., 2005).

107

2.2 Design of the trackline
A sawtooth type trackline was applied to provide
for a wider area of coverage. The starting point of thesawtooth trackline was randomly selected from
1 n.mile intervals along the longitudinal lines (Fig. 4a).
The trackline legs were systematically set on theice-edge and on the locus of 45 n.miles from theice-edge in the southern strata, and 45 n.miles fromthe 60°S latitude line in the northern strata.

(a)

(b)

(c)

(e)

(d)

(f)
(g)

(h)

(i)

Fig. 4 Design of the trackline and photogaraphs of the research vessels of the JARPA. (a) Trackline model diagram in the researcharea. The trackline was romdomly and systematically set in the research area. Blue colored area shows ice edge line.
(b) Kyo-Maru No.1, (c) Toshi-Maru No.25, (d) Toshi-Maru No.18, (e) Kyosin-Maru No.2, (f) Yusin-Maru, (g) Yusin-Maru
No.2., (h) primary observer in the top barrel, (i) Blow of large school of Antarctic minke whales.

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K. MATSUOKA et al.

2.3 Research vessels and method of searchingwhales
A total of six sighting survey vessels equippedwith sighting platforms (top barrel and upper bridge)
were engaged in the previous cruises (Fig. 4b-4g).
Kyo-Maru No.1 (812 tons) and Toshi-Maru No.25(740 tons) operated for the surveys from 1987/88 to
1997/1998. Toshi-Maru No.18 (812 tons) also operated for the surveys from 1989/90 to 1997/1998.
Kyosin-Maru No.2 (372 tons) has been engaged sincethe 1995/96 survey. Yusin-Maru (720 tons) operated

for the 1998/1999 survey as a replacement for
Toshi-Maru No.18. Yusin-Maru No.2 (747 tons) operated from the 2001/2002 survey as a replacement for
Toshi-Maru No.25. Three primary observers searchedfrom the top barrel and three primary observers, fromthe upper bridge (Fig. 4h & 4i). Sighting surveys wereconducted under definite weather conditions (forexample, when the wind speed was 20 knots or less inthe northern strata and 25 knots or less in the southern
strata) and the whole research area was covered in a
mainly pre-determined zigzag search pattern for whale
density estimates. The distribution of the searchingefforts in JARPA1987/88-2003/04 seasons, including
the middle latitude transit sighting survey, is shown in
Fig. 5.

3. Distribution and Abundance of Major
Baleen Whales in the JARPA Research
Area

Fig. 5 Distribution of the searching efforts (nautical
miles) in the JARPA-1987/88-2003/04 seasons.
Includes middle latitude transit sighting surveys.

Fig. 6The distribution of major whale species sighted in
the research area is shown in Fig. 6. The abundance ofAntarctic minke whales was estimated by Hakamada
et al. (2005). the abundance of other baleen whales
was estimated by Matsuoka et al. (2005). Table 1
summarizes current abundance estimates of Antarctic
minke (Eastern Indian Ocean Stock and WesternSouth Pacific Stock), humpback, (Western Australian
Stock and Eastern Australian Stock), fin (Indian
Ocean Stock and Western South Pacific Stock ) and

(a)

(b)

(c)

(d)

Map of the Density Index (number of primary sightings of whales / 100 n.mile) of whales during the JARPA-1987/88-2003/04 seasons by 1°×1°square. (a) Antarctic minke whale, (b) humpback whales, (c) fin whales, (d)blue whales.

Abundance of Large Baleen Whales based on the Sighting Survey in JARPA

blue whales based on the most recent stock boundariesof these species (Pastene et al., 2005a & 2005b).
3.1 Antarctic minke whale
Antarctic minke whales were widely distributed in
the northern and southern strata. They also tended tooccur more in the southern strata than in the northern
strata. High density areas were observed in the southern strata, specially the Ross Sea and Prydz Bay(Fig. 6a).
Eastern Indian Ocean Stock: 35°E-165°E
For this stock, because abundance estimates in
Area IIIE are available only from the JARPA survey inthe 1995/96 season, the abundance of this stock was
estimated from the 1995/96 to the 2003/04 seasons.
Table 2 and Fig. 7 show abundance and biomass esti-

109

mates of this stock in the research area (south of 60°S,
35°E-165°E). The abundance of this stock was stablebetween the 1995/96 and 2003/04 seasons.
Western South Pacific Stock: 165°E-145°W
For this stock, because abundance estimates in
Area VIW are available only from the JARPA survey
in the 1996/97 season, the aabundance of this stock
was estimated from the 1996/97 to the 2002/03 seasons. Table 2 and Fig. 7 show abundance and biomass
estimates of this stock in the research area (south of
60°S, 165°E-145°W).
3.2 Humpback whales
Western Australian Stock: 70°E-130°E
Humpback whales were concentrated between 90°
and 120°E in the northern and southern strata, andTable 1 Recent abundance estimates (P) of Antarctic minke, humpback, fin and blue whales for each stockusing JARPA 2002/03 and 2003/04 data (south of 60oS). For humpback and fin whales, average oflatest two seasons abundance was used. The g (0) is assumed to be 1. Average body weights used forthe biomass, were 7, 26.5, 48 and, 83 tons for Antarctic minke, humpback, fin and blue whales,
respectively.

Table 2 Abundance estimates (P) of Antarctic minke whales (Eastern Indian Ocean Stock and Western South
Pacific Stock) between 1995/96 and 2003/04 seasons (south of 60°S). The g (0) is assumed to be 1. The
avarage weight of this species was seven tons for the biomass.

Eastern Indian Ocean Stock
Season1995/96
1997/98
1999/2000
2001/02
2003/04

P
82,975
124,301
128,110228,349
128,695

CV
0.165
0.187
0.227
0.142
0.248

Biomass
580,825
870,107896,770
1,598,444
900,864

Western South Pacific Stock
Season1996/97
1998/99
2000/01
2002/03
2004/05P
156,323
82,489179,417
95,116
-

CV
0.267
0.219
0.197
0.168
-

Biomass
1,094,261
577,423
1,255,919
665,812-Fig. 7 Abundance estimates (south of 60°S) of Antarctic minke whales (Left side: Eastern Indian Ocean Stock: 35°E-165°E;
right side: Western South Pacific Stock: 165°E-145°W) in the research area. Vertical lines show standard errors.

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K. MATSUOKA et al.

were widely dispersed in the other parts of Area IV(Fig. 6b). A comparison of the distribution pattern
between the first half of JARPA (1989/90-1996/97)
and the latter half (1997/98-2003/04) shows an increase in the number of sightings in Area IV between
90° and 120°E by the three sighting vessels (Fig. 8),
and that the area of concentration of this species was
expanding to the southern and eastern strata year by
year. The average latitude of the area of concentration
was 60°30’S in the first half, and 62°30’S in the latter
half of JARPA (Fig. 9).
The catching of humpback whales in the Antarctic
was banned in 1963. Bannister (1994) reported a total
population size of some 3,000 whales off Shark Bay,Western Australia, based on the results fromcomparison of the 1991 sighting rate with those of a1963 commercial aerial spotter. In the late 1990s,
analyses of coastal aerial surveys estimated8,000-14,000 whales (a rate of increase of 10.2±4.6%)
off Western Australia (Bannister & Hedley, 2001). The
abundance using IWC/SOWER data for the part ofArea IV (80°-130°E) in 1998/99 was estimated at
17,300 (CV=0.17) whales (Matsuoka et al., 2003a). At
the start of JARPA, the abundance of this stock was
only 5,230 (CV=0.30) (1989/90 season), but current
the abundance of this stock was estimated at 31,750(CV=0.11) in the 2003/04 season (Table 3 and Fig.10).
The recent abundance (average of 2001/02 and2003/04) has been 32,380 (CV=0.08). The rate of
Increase of this stock in the feeding ground (south of60°S) was estimated at 16.2±6.4%, so recent habitat

extension of this stock may be the cause of this highestimate (Matsuoka et al., 2005). As a result of stock
assessment, near complete recoveries to pristine levels
are suggested in some ten years for this stock(Johnston & Butterworth, 2005).
Eastern Australian Stock: 130°E-170°W
The Eastern Australian Stock in Area V tended tooccur in the eastern part of Area V, except for the Ross
sea. They were distributed clearly along the Pacific
Antarctic ridge where the southern boundary of the
Antarctic Circumpolar Current was observed(Matsuoka et al., 2003b). Table 3 shows abundanceetimates for this stock. Yearly fluctuations of abundance estimate were observed for this stock (Fig. 10),because large sea ice fluctuations were observed inthis Area (Zwally et al., 2002), especially the northernpart of the Ross Sea.
There are several reports on abundance estimatesof humpback whales in the late 1990s off Eastern
Australia and Antarctic Area V. The estimate of East
Australian humpback whales, using a land-based survey was 3,185 (s.e.=208) whales in 1996 (Brown et al.,1997). The estimate in Antarctic Area V in the
1991/92 season using IWC/IDCR data was 2,104
whales (CV=0.52) (Brown & Butterworth, 1999).
Recent JARPA estimates (average of 2000/01 and2002/03) have been 3,728 (CV=0.15) whales, which
are consistent as the rate of increasie has been assumed to be some 10%. As a result of stock assessment, near complete recoveries to pristine levels aresuggested in some 15-20 years for the currently more

Fig. 8 Comparison of the distribution plot (primary sightings) pattern for humpback whales between the first halfof the surveys (left: 1989/90-1996/97) and the latter half of the surveys (right: 1997/98-2003/04) by threevessels. The number of sightings increased in the Area IV between 90°and 120°E.

Fig. 9 Comparison of the latitudinal density index (number of primary sightings of whales/100 n.mile) for
humpback whales between the first half of JARPA (left: 1989/90-1996/97) and the latter half of JARPA(right: 1997/98-2003/04) by three vessels. The average latitude was 60°30’S in the first half of the surveys,
and was 62°30’S in the latter half of the surveys.

Abundance of Large Baleen Whales based on the Sighting Survey in JARPA

depleted Eeatern Australian Stock (Johnston & Butterworth, 2005).
3.3 Fin whales
Abundance of this species in whole Antarctic
waters based on IWC/IDCR and the Japanese Scouting Vessels (JSV) was estimated at 18,000 (CV=0.47)
south of 30°S (Butterworth et al., 1994). Recent eachcircumpolar abundance estimate of this species increased in the whole area south of 60°S based on the
IWC/IDCR-SOWER were 2,100 (CV=0.36), 2,100(CV=0.45) and 5,500 (CV=0.53) whales in the first(total of the 1978/79-1983/84), second (total of the
1985/86-1990/91) and third circumpolar (total of the
1991/92-1997/98) series, respectively (Branch &Butterworth, 2001). For the half of the Antarctic area
(south of 60°S, 35°E -145°W), latest abundance (totalof the JARPA-2001/02 and 2002/03) of this species
were estimated 10,078 (CV=0.20) whales (Matsuoka
et al., 2005).
Indian Ocean Stock: 35°E-130°E
The Indian Ocean Stock of this species was widelydistributed in the Areas IIIE and IV, and they tended tobe distributed more in Area IIIE than in Area IV. They
were widely dispersed and also rarely found within
Prydz Bay (Fig. 6c). Comparison of the distribution
pattern during the first half of JARPA (1989/90-1995/96) and the latter half (1996/97-2003/04), shows thatfin whales have appeared more frequently in thewestern part of Area IV in recent years (Fig. 11).
No abundance estimation of this stock from sightings data was reported. The recent abundance (averageof 2001/02 and 2003/04) has been estimated at 8,621(CV=0.19) for south of 60°S (Table 4 and Fig. 12).

Table 3 Abundance estimates (P) of humpback whales for the Western Australian Stock and Eastern
Australian Stock (both south of 60°S), between 1989/90 and 2003/04. Average weight of this species
was 26.5 tons for the biomass.

Western Australian Stock111

Eastern Australian Stock

Fig. 10 Abundance estimates of humpback whales (south of 60°S) between the 1989/90 and 2003/2004 seasons (over15 years) in relation to Table 3. Vertical lines show standard errors. Left side: Western Australian Stock, rightside: Eastern Australian Stock. Vertical lines show standard errors.

Fig. 11 Comparison of the distribution plot (primary sightings) pattern for fin whales between the first half of thesurveys (left: 1989/90-1996/97) and latter of the surveys (right: 1997/98-2003/04) by three vessels. The
number of sightings increased in the Area IV between 70°and 100°E.

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K. MATSUOKA et al.

Because they are mainly distributed in the area northof 60°S (Kasamatsu, 1993), large yearly fluctuationsin the area south of 60°S in Areas IIIE and IV might
be attributable to such a distribution. For an abundance estimation of the whole Indian Ocean Stock, it
is possible to extrapolate the current abundance to thenorth of 60°S using Japanese scouting vessel (JSV)data (Miyashita et al., 1995). Extrapolated abundance
which weighted by the JSV data (sighting rate (number of whales by 10,000 n.miles) of 5°×5° square)collected in January and February during 1965 to1987
was estimated to be 31,000 whales (CV=0.26) for thisstock (south of 40°S, 35°E-130°E), from the results of
the JARPA-2003/04 data (Matsuoka et al., 2005).
Western South Pacific Stock : 130°E-145°W
For this stock of this species in the area south of
60°S, the recent abundance (average of 2000/01 and2002/03) has been estimated at 4,691 (CV=0.17)(Table 4 & Fig. 12). For the whole Western Pacific
Stock abundance estimation, as same as the Indian
Ocean Stock, the extraporated abundance in January
and February with consideration of seasonal distribution changes of this species was estimated to be
16,000 whales (CV=0.29) for this stock (south of 40°S,
130°E-145°W), from the results of the JARPA-2002/
03 data (Matsuoka et al., 2005) .

3.4 Blue whales (35°E-145°W)
There is no stock information on blue whales in the
JARPA research area. Initially, there were as many as
200,000 blue whales in the whole Antarctic as calculated by a logistic model, but their number was greatly
reduced by over-hunting, and their take was banned in
1964. After forty years, however, they still small number less than 2,000 whales, and they are increase at amean rate of 7.3% per annum (1.4%-11.6%) between
1968 and 2001 (Branch et al., 2004).
In the JARPA research area, blue whales wererarely encountered by the surveys, though they were
widely distributed in the research area. They wereusually found in Area IIIE and Area VE (Fig. 6d). In
Area IV, the number of sightings of this species increased in the latter half of JARPA (Fig. 13). Abundance of this species south of 60°S, 35°E-145°W was
900 (CI: 500-1,600) in the 1999/2000 + 2000/01 seasons and 500 whales (CI: 300-1,000) in the 2001/02 +2002/03 seasons (Table 5). They still number less than
1,000 (biomass: less than 8,000 tons) in the JARPA
research area. Also, the number of survey years is still
too small to detect any precise yearly trend. Further
surveys will be necessary for improving the precisionof estimates of the annual rate of increase in the feeding ground.

Table 4 Abundance estimates (P) of fin whales (south of 60°S) for the Indian Ocean Stock and Western South
Pacific Stock, between 1989/90 and 2003/04. The avarage weight of this species was 48 tons for thebiomass.

Indian Ocean Stock

Western South Pacific Stock

Abundance estimation

15,000

Fin whale
Pacific ocean stock(South of 60S, 130E-145W)
10,0005,000

02004/05

2002/03

2000/01

1998/99

1996/97

SeasonsFig. 12 Abundance estimates of fin whales (Indian Ocean stock: south of 60°S, 35°E-130°E) between the 1989/90
and 2003/2004 seasons (over 15 years) in relation to Table 4. Vertical lines show standard errors.

Abundance of Large Baleen Whales based on the Sighting Survey in JARPA

113

Fig. 13 Comparison of the distribution plot (primary sightings) pattern for blue whales between the first half ofsurveys (left: 1989/90 -1996/97) and the latter of the surveys (right: 1997/98-2003/04) by three vessels.
The number of sightings were increased in the Area IV.

Table 5 Abundance estimates (P) of fin whales (south of 60°S) for the Indian Ocean Stock and Western South
Pacific Stock, between 1989/90 and 2003/04. The avarage weight of this species was 83 tons for thebiomass.
Blue
Seasons
1989/90 + 1990/91
1991/92+ 1992/93
1993/94+ 1994/95
1995/96+ 1996/97
1997/98+ 1998/99
1999/00+ 2000/01
2001/02+ 2002/03
2003/04+ 2004/05

Area
IIIE
P
293
248
352
80
540

CV
0.43
0.49
0.59
0.62
0.34

Area
IV
P
65
17
64
6
153
218
295
92

CV
0.48
1.08
0.62
0.94
0.61
0.40
0.44
0.72

4. Habitat Expansion of Humpback Whales
in Area IV
Present abundance estimates of humpback whales
in Area IV have increased year by year especially after
the 1997/98 season (Fig. 10). After the 1997/98 season,
humpback whales tended to increase in the southernand eastern strata year by year (Figs. 8 and 9). These
distribution changes suggested that humpback whale
populations are recovering and expanding their distributions to the south and east in the feeding grounds
year by year. Further, according to oceanographic research, the southern boundary of the Antarctic Circumpolar Current (SB-ACC) in the research area
moved south year by year from 1997/98 to 2001/02(Watanabe et al., 2005). It is known that the distribution of humpback whales related to the SB-ACC(Matsuoka et al., 2003b), and it is reasonable to support a view that the habitat shifted from north of 60°S
to the south, related to the SB-ACC movement to thesouthern region. It is also reasonable to support a viewthat the present estimated rate of increase of 16.2%
may include two phenomena, their ‘real rate of population increase’ and the ‘effect of habitat expansion’.
Further enviromental analyses such as satellite information and oceanographic data will be required inorder to interpret ‘habitat expansion’ more precisely inthe feeding grounds.

Area
V
P
205
231
275
7
221
294
142
-

CV
1.01
0.67
0.64
0.75
2.07
0.49
0.53
-

Area
VIW
P
58
0
0
28
-

Total
CV
0.45
0.94
-

P
270
248
339
364
622
864
545
-

CV Biomass(ton)
0.78
22,4100.63
20,5840.53
28,1370.35
30,2120.78
51,6260.31
71,7120.29
45,235-

5. A ‘Shift in Baleen Whale Dominance’from Antarctic Minke to Humpback
Whales in Area IV
The biomasses of Anratcic minke, humpback, fin
and blue whales in Area IV are shown in Fig. 14. A‘Shift in baleen whale dominance’ from Antarctic
minke to humpback whales was observed in this Area
since the 1997/98 season. In the 1989/90 season, thebiomass of Antarctic minke was higher (382,000 tons)
than that of humpback whales (139,000 tons), andafter 15 years, in the 2003/04 season, the biomass of
humpback (841,000 tons) was twice that of Antarctic
minke (335,000 tons). An increase in fin whales wasobserved in Areas IIIE and IV. In the 1989/90 season,
the biomass of fin whales was 5,000 tons, and after 15
years, in the 2003/04 season, the biomass of fin
whales was 67,000 tons, an increase of over ten times(20% of Antarctic minke biomass). The abundance ofAntarctic minke whales is stable in Areas IV and V(Hakamada et al., 2005), but a decrease in blubber
thickness in Area IV was observed (Konishi & Tamura,2005), and a decreasing trend in stomach content
weights of matured minke whales was also observedin Area IV since the 1987/88 season using JARPA
biological data (Tamura & Konishi, 2005). It is also
reasonable to support a view that the increase andhabitat expansion of humpback and fin whales in Area
IV may lead to their competition with Antarctic minke
whales. On the other hand, the Antarctic minke whale
was still the dominant species in Area V (Fig.15).

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Fig. 14

K. MATSUOKA et al.

Biomass of Antarctic minke, humpback, fin andblue whales in Area IV (south of 60°S) surveyed
during January to February, between the 1989/90
and 2003/2004 seasons (over 15 years). A ‘shift inbaleen whale dominance’ from Antarctic minke to
humpback whales was observed since the 1997/98
season (arrows).

Further mornitaring surveys will be required in orderto understand Antarctic marine ecosystem and to improve baleen whale management in the Antarctic
Ocean.

6. Monitoring Whale Populations
In the Antarctic Ocean, catching of southern right,
humpback, blue, fin and sei whales was prohibited in
1932, 1963, 1964, 1976 and 1978, respectively.
Seventy years have passed already since the southern
right whale was protected, and more than 40 years
have passed since humpback whale and blue whale
have been protected. In coastal waters of south
America, South Africa and the east and west coast ofAustralia, significant recovery of southern right whale
and humpback whales has been reported recentry inthese breeding areas. On the other hand, informationon the present status of pelagic species, such as blue,
fin and sei whales is limitted. The IWC/IDCRSOWER cruises, however, are insufficient for monitoring the marine ecosystem, as survey covers thesame area less than once in every six years. In thissituation, JARPA have been monitoring baleen whale
species populations by large-scale, long-term linetransect surveys for over 15 years in Areas IV and V.
The number of survey years is still too small to detect
precise yearly trends in whales populations. Further
monitoring surveys will be required for baleen whale
management in the Antarctic Ocean.

Acknowledgements
We wish to express our gratitude to all researchers,
the Captain and crewmembers who have contributed
to these JARPA surveys in the Antarctic. We also
thank to Drs. Seiji Ohsumi, Hiroshi Hatanaka andYoshihiro Fujise of the Institute of Cetacean Research,and Drs. Hidehiro Kato, Tomio Miyashita of the
National Research Institute of Far Seas Fisheries

Fig. 15 Biomass of Antarctic minke, humpback, fin and blue
whales in Area V (south of 60°S) surveyed during
January to February, between the 1990/91 and2002/2003 seasons (over 13 years).

(NRIFSF) and anonymous reviewer for their valuablesuggestions and comments for this paper. Figure 2d
was provided by Kyodo Senpak Kaisha, Ltd. We also
thank Mr. Atsushi Wada, Ms. Shoko Ohkawa and Dr.
Kazuhiro Ohshima for their assistance with this paper.
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(Received 11 May 2005, Accepted 1 July 2005)