SC/D06/J21

Results of the cetacean prey survey using a quantitative echosounder in JARPA from 1998/99 to 2004/2005
HIROTO MURASE, HIROSHI KIWADA, KOJI MATSUOKA, SHIGETOSHI NISHIWAKIThe Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan
ABSTRACT
Krill biomass estimation surveys using a quantitative echo sounder have been conducted in JARPA since
1998/99 season to achieve one of the main objectives of JARPA which is elucidation of the role of whales in
the Antarctic marine ecosystem. The survey was conducted concurrently with cetacean survey. Similar biomass
estimates were obtained in Area IV in the 1999/2000 (34.2 million t) and 2001/2002 (34.1 million t) seasons. In
Area V, biomass in the 2000/2001 (20.7 million t) and in the 2002/2003 (22.6 million t) seasons were similar
but biomass in 1998/1999 (29.7 million t) was higher than the other two years. Higher biomass in 1998/99
could be explained by seasonal effect and area coverage differences. Biomass density in each stratum as well
as overall biomass (7.0 million t) in Area V were low in 2004/2005 even if no krill biomass estimate in NorthWest stratum because of prevailing poor weather conditions for acoustic survey was taken account. Biomass in
Area IV was higher than Area V. There was a unique opportunity to compare the biomass estimate from two
independent vessels in the Ross Sea region in 2004/2005. One vessel, Kaiyo Maru, conducted standardized
krill biomass estimation survey adopted by CCAMLR using both RMT net sampling and acoustic survey while
the other vessel, Kyoshin Maru #2, only conducted acoustic survey as in previous JARPA cruises. The resultsof biomass estimates from two vessels were comparable. The result suggested that biomass estimations inprevious JARPA cruises which thoroughly relied on acoustic were reliable. Because krill biomass surveys in
the whole of Area IV and Area V were rarely conducted in the past, krill data collected by JARPA were quite
important to understand krill-baleen whale relationships in the Antarctic.

INTRODUCTION
It is well known that krill is the key species in the Antarctic marine ecosystem because krill is amajor link in the transfer of energy from primary producers to larger organisms such as baleen
whales (Laws, 1985; Murphy et al., 1988). Krill have been known as the major food source ofbaleen whales in the Antarctic (Kawamura, 1994). “Krill surplus” caused by intensive commercial
harvesting of large whales, blue (B. musculus), fin (B. physalus) and humpback whales (Megaptera
novaeangliae), has been central theorem of the Antarctic ecosystem study. “Krill surplus” resulted
in increasing in amount of available food to other krill feeders such as Antarctic minke whales (B.
bonaerensis) (Laws, 1977). But it appears that the situation is changed in recent years. After the banof commercial whaling of large whales in 1987, it was reported that abundance of those species
increased in recent years. For example, abundance of blue whales increase 8% per year at thecircumpolar level (Branch et al., 2004) though the abundance was still low comparing with preexploitation population size. Some stocks of humpback whales in southern hemisphere have been
showed remarkable recovery even to near pre-exploitation level (Johnston and Butterworth, 2004).
To test the magnitude of interaction, preliminarily baleen whales-krill interaction model wasdeveloped but the interpretation was limited at this moment because of paucity of information
including biomass estimation of krill (Mori and Butterworth, 2006). Krill density showed both shortand long term changes. In short term, krill density showed large year to year fluctuation at decadalscale in response to environmental variability such as sea ice extent and oceanographic conditions(e.g. Pakhomov, 2000; Hewitt and Demer, 2003). It was reported that krill density have showedstatistically significant decreasing trend in the southwest Atlantic since 1976 (Atkinson et al. 2004)
though the magnitude of decrease should be studied further to draw the conclusion because wide
varieties of net types were used in the analysis. Given the krill density change information, krill
biomass survey should be conducted regularly in the same region. To assess the magnitude ofinterspecific competition among baleen whales for krill and the consequences of the competition
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quantitatively, conducting concurrent cetacean and krill survey is critical.
The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA)
provided unique opportunity to conduct the concurrent cetacean and krill survey. JARPA has been
conducted during the austral summer every year since the 1987/1988 season. One of the primaryobjectives of the JARPA is “Elucidation of the role of whales in the Antarctic marine ecosystemthrough the study of whale feeding ecology”. The JARPA interim review meeting took place in May,
1997. In the meeting, it was pointed out that concurrent studies on the distribution and abundance of
prey species was required to achieve the objective. In response to the comments, echo soundersurvey to examine distribution and abundance of krill has been conducted concurrently withcetacean survey since 1998/99 season. Krill distribution data will be linked with distribution
patterns of baleen whales whereas krill abundance data will allow us to examine the magnitude of
the interspecific relationship among baleen whales for krill. The preliminary report of the echosounder surveys of krill that were conducted in 1998/1999 and in 1999/2000 were reported to theInternational Whaling Commission (IWC)/Scientific Committee (SC) as SC/52/E5 (Murase et al.,2000) and published in scientific journal (Murase et al., 2002). This paper presents the echo soundersurvey methodology and the results of biomass estimation of krill in JARPA from 1998/99 to
2004/2005. In addition, the results of the comparison of two krill biomass estimates in the Ross Sea
region in 2004/2005 using two independent echo sounder data from two vessels were briefly
discussed.
MATERIALS AND METHODS
Survey area
Two baleen whale management area defined by the International Whaling Commission (IWC), Area
IV (70°E-130°E) and Area V (130°E-170°W), were surveyed alternative years. The areas between
south of 60°S and the ice edge line were surveyed. Each area was further divided into two, east andwest, at 100°E in Area IV and at 165°E in Area V. Each sector further divided into two strata, north(between the 60°S latitude line to the line of 45 n.miles from ice edge) and south (between the lineof 45 n.miles from ice edge and ice edge). Exceptions were the Prydz Bay region (south of 66°S
between 70°E and 80°E) and the Ross Sea region (South of 69°S between 165°E and 170°W). The
Ross Sea region was defined as south-east stratum of Area V whereas the Prydz Bay region was
called as it was. In addition to two Areas, eastern part of Area III and western part of Area VI werealso surveyed alternative years. No specific stratification was set in those Areas. Following
acronyms were used to describe strata name;
III-E-F
III-E-S
IV(or V)-NE
IV(or V)-NW
IV(or V)-SW
IV(or V)-SE
IV-PB
VI-W-F
VI-W-S

Eastern half of Area III, first period
Eastern half of Area III, second period
North-East stratum in Area IV (or V)
North-West stratum in Area IV (or V)
South-West stratum in Area IV (or V)
North-East stratum in Area IV (or V)
Prydz Bay region in Area IV
Western half of Area VI, first period
Western half of Area VI, second period

Timing of surveys
Surveys were conducted during austral summer (December-March). Detailed survey dates weresummarized in Table 1 and 2.

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Trackline designs
Sawtooth type zigzag lines were used in each survey. Details of the trackline designs were reviewed
in Nishiwaki et al. (2006).
Survey vessel
The cetacean sighting vessel, Kyoshinmaru No.2 (KS2, 368 GT) was engaged in the sighting surveyof cetaceans as well as echo sounder and oceanographic surveys. The nominal steaming speed of
SV on the track line was 10.5 knots.
Data acquisition and storage system
An EK500 scientific echo sounder (Simrad, Norway) with software version 5.30 operating
frequency at 38 and 120 kHz on board Kyoshin-maru No.2 was used to collect data for the acoustic
survey from 1998/99 to 2003/04. The transducers were hull-mounted at the depth of 4.3 m from thesurface. Each transducer was covered with a 40 mm polycarbonate acoustic window to minimize
the damage on the transducer surface from contacting sea ice. The hydraulic oil filled the space
between the transducer surfaces and the acoustic windows. Data were recorded with the aid of a
BI500 post processing system (Simrad, Norway) from 1998/99 to 2004/05.
Data analysis system
BI500 was used for the data analysis in 1998/99 and in 1999/2000. Echoview version 3.00.74.01(SonarData Pty Ltd, Australia) was used from 2000/01 to 2004/05. Major function of Echoview wassame as BI500 but it allowed more detailed analysis than BI500. Echoview was software operated
under the Microsoft Windows. Echoview was capable to analyze BI500 data file.
Calibrations
The copper sphere technique that described in EK 500 operation manual (Simrad, 1997) wasapplied for the calibrations. Calibrations were conducted in Antarctic water every year. In 2002/03
and 2003/04, calibrations were attempted but the results weren’t applied to the analysis because
those were conducted in unsuitable conditions for calibration. For those years, the result of thecalibration in 2001/02 was applied for analysis.
Data recording methodology
The survey was conduced during diurnal hours from an hour after sunrise to an hour before sunset.
Maximum survey time per day was 12 hours. Data were recorded continuously while the vessel
steamed on predetermined trackline. The data were not used in the analysis when the vessels
deviated from the trackline such as during cetacean species confirmation.
Data analysis methodology
We applied the acoustic data analysis described by Hewitt and Demer (1993) and Demer and Hewitt(1995). The following procedures came from those papers. Mean backscattering area per square n.
mile of survey transect (sA) attributed to krill for every 1 n. mile of survey transect over 10 to 250 m
depth was calculated by following formula;s A = 4πr021852 2

r2 = 250m2∫r =10 sV dr ( n.mi 2 )1where, r is depth from the surface, r0 = 1m representing the reference range for backscatteringstrength and sV = 0 if 10 log (sV) ≦ -80dB, because threshold backscattering was set at –80dB.
Because direct sampling method (e.g. net sampling) to identify species was not available, thedifference between the mean volume backscattering strength (ΔMVBS) of 120 and 38 kHz fell
between 2 and 16 dB is classified as krill (Hewitt et al., 2004). Because BI500 didn’t have3

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capability to calculate ΔMVBS, the differences were visually identified using the echogram in
1998/99 and 1999/2000. For the lest of year, ΔMVBS was calculated quantitatively using Echoview.
Krill backscattering cross section area (σ) was calculated with the following formula based on krill
target strength described by Greene et al. (1991):
σ = 4πro210−12.745 l 3.485

where, l was standard length of krill. Krill wet weight (w) was calculated with the following
formula based on Siegel (1986):
w = 0.00193l 3.325 .
Average area krill biomass density ( p ) was calculated as follows;wρ = S A = 0.249l −0.16 S A .
σThen, frequency distribution of euphausiids standard length ( f i ) was applied to the following
formula;ρ = 0.249

n∑ fi (li )−0.16 S A .
i =1

Because minor variation in the frequency distribution of krill length did not affect the krill biomass
estimate, a combined distribution data based on Loeb and Siegel (1992) was used (Demer and
Hewitt, 1995) as follows;n∑ f i (li ) −0.16 ≅ 0.562 .
i =1With this formula mean krill biomass of each transect in each stratum was calculated. Following
procedures were adopted from Jolly and Hampton (1990). Weighted mean of SA of each block was;Nk

∑ S Aki (nk i )S Ak = i =1 N

∑ nk ik

i =1where, S Ak = mean SA in kth block, N k = number of transects in kth block, S Aki = mean SA on the ithtransect in kth block and nk i = number of 1 n. mile averaging intervals on the ith transect in kth
block. In this formula, each transect was regarded as a single biomass density sample. Thenvariance of S Ak was calculated with the formula (Jolly and Hampton, 1990);
Nk

Var ( S Ak ) =∑ (S Ak i − S Ak )2 nk i 2

N k i =1
Nk −1

⎞
⎛ Nk
⎜ n ⎟
ki ⎟
⎜
⎠
⎝ i =1

2∑

S A was converted to p using above motioned formula. Biomass was estimated as;
Bk = Ak ρ kwhere, Bk is density biomass in kth block and Ak is area of kth block. Variance of Bk was calculatedwith following formula;var(Bk ) = Ak 2 var(ρ k ) .
Coefficient of variation of Bk was calculated as;
BB

var(Bk )CV ( Bk ) =Bk

Biomass (B0) in each Area was calculated as;
B0 =N∑ Bk .
k =1

Overall survey variance of B0 was;4.

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Var ( B0 ) =N∑ var(Bk ) .
k =1

Coefficient of variation of B0 was calculated as;
B

Var ( B0 )CV ( B0 ) =B0.

Krill biomass estimation in Kaiyo Maru – JARPA joint survey
Kaiyo Maru–JARPA joint survey in the Ross Sea (south of 69°S) in 2004/05 was designed as multidisciplinary study combining the cetacean, krill and oceanographic studies. In the joint survey, twovessels, Kaiyo Maru (2,630 GT) and KS2, conducted krill biomass surveys using the EK500. In
addition to echo sounder survey, Kaiyo Maru also conducted net sampling using a Rectangular
Midwater Trawl with 1m2 and 8m2 mouth opening (RMT8+1) for sampling of krill. Details of thekrill biomass estimation methods in Kaiyo Maru-JARPA joint survey were described in Murase et al.
(2006).

RESULTS
Krill biomass in each stratum in Area IV and eastern part of Area III
Surveys were conducted in Area IV and eastern part of Area III in 1999/2000 and 2001/2002. Nodata was available for analysis in 2003/2004. Density and biomass in each stratum in each year
were summarized in Table 1. Distribution patterns were shown in Fig. 1. Timings of surveys were
almost same for two years. Density and biomass in IV-SW in 2001/2002 were remarkably higher
than 1999/2000. It should be noted that survey effort in Northern strata in Area IV in 2001/2002
was lower than that of in 1999/2000 because of poor weather conditions for the echo sounder survey.
Krill biomass in each stratum in Area V and western part of Area VI
Surveys were conducted in Area V and western part of Area VI in 1998/1999, 2000/2001,
2002/2003 and 2004/2005. Density and biomass in each stratum in each year were summarized inTable 2. Distribution patterns were shown in Fig. 2. Timing of survey in 1998/1999 was different
from other years. Because the mouth of the Ross Sea was closed in 1998/1999, the Ross Sea region
was not surveyed. In addition, V-NE was not surveyed as well.
Krill biomass estimation by Area
Results of biomass estimation of krill by area by year were summarized in Table 3. Overall, year toyear differences of biomass estimations and CVs were small except 1998/1999 and 2004/05, thougheach stratum in each area showed year to year biomass and CV variations. It should be noted thatthe survey timing and coverage in Area V in 1998/1999 were different from other years. Estimatedbiomass in Area V were low in 2004/2005 even if no krill biomass estimate in North-West becauseof prevailing poor weather conditions for acoustic survey was taken account.
Krill biomass estimation in Kaiyo Maru – JARPA joint survey
Following results were described in Murase et al. (2006). Biomass densities of Eupahsia. superba
with 95% CI estimated using Kaiyo Maru and KS2 data were 5.36±7.45 and 2.64±2.35 g/m2,
respectively. Biomass densities of E. crystallorophias with 95% CI estimated using Kaiyo Maru andKS2 data were 3.44±1.96 and 1.56±0.89 g/m2, respectively. Because there was no significant
difference between the biomass density estimates from both vessels, two data sets were combined toestimate the biomass. The biomasses of E. superba and E. crystallorophias in this study were5

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estimated as 1.46 (CV=0.32) and 0.82 (CV=0.18) million t, respectively (Table 1). Total krill (E.
superba + E. crystallorophias) biomass was 3.1 million t (CV=0.22).
DISCUSSION
The position of the Southern Boundary of the Antarctic Circumpolar Current (SB-ACC) in
2001/2002 shifted to south in comparison with that in 1999/2000 (Watanabe et al., 2006). The SBACC was corresponded to high primary production and hence to distribution of whales (Tynan,1998). It was postulated that krill would be coastally constrained when the position of the SB-ACC
shows southerly shift (Nicol et al., 2000(a)). Higher density and biomass in VI-SW in 2001/02 thanin 1999/2000 could be related to the southerly shift in position of the SB-ACC. This is the first time
to confirm the hypothesis proposed by Nicol et al. (2000(a)) in this region. Few echo soundersurveys were conducted between 35°E to 170°W in the past except the Prydz Bay region. Survey of
distribution and abundance between 80°E and 150°E from south of 63°S to ice edge was conductedby Australian research vessel in 1995/96 austral summer (Pauly et al. 1997). They reported krill
densities of 5.5 g/m2, 6.7 g/m2, 4.2 g/m2 and 9.2 g/m2, in whole survey area, west area (80°E-115°E),
east area (115°E-150°E) and shelf break area, respectively. Those densities were significantly lower
than those reported in this paper, though it was difficult to compare the two results directly because
survey coverage, design and timing were totally different from each other. Quite significant interannual variability of biomass densities caused by environmental factors were reported in the
Cooperation Sea (50°E-85°E) (Pakhomov, 2000) and in the South Shetland Islands region (Hewitt
and Demer, 2003). Such inter-annual variability could explain the differences but frequent surveys
in this area should be conducted in future to clarify the existence of the inter-annual variability andthe causes of variability. Azzali et al. (2006) postulated that the distribution pattern of E. superba
and E. crystallorophias shifted to north as the ice edge moved to northward in austral summer but
the magnitude of movement was more significant for E. superba. As the results, density of E.
superba in January 2000 was low by comparison with November in 1994 and December in 1994
and 1997 though one need caution of the interpretation because of methodological differencesamong those surveys (Azzali et al., 2006). Our surveys in the Ross Sea were mainly conducted in
January. It seemed that there was general agreement between our results and the hypothesis
proposed by Azzali et al. (2006). Though this survey could not have biomass estimates for each krill
species, densities of krill were similar to the value in January in Azzali et al. (2006) while biomass
estimates were in the comparative range regardless of month. Even if densities were low in January,
surveyed area in January was generally large as the result of sea ice retreat. Dispersal response of
krill distribution to seasonal sea ice retreat in the Ross Sea should be studied further in the future
cruises.
It should be noted that highest biomass recorded in Area V in 1998/1999 especially in V-NW
and V-SW. In 1998/99, those two strata were surveyed earlier about a month than latter two years(2000/2001 and 2002/2003). V-NW and V-SW were surveyed in mid January to mid February in
1998/1999 while they were surveyed in mid February to at beginning of March in latter two years.
Intra-annual variability in krill abundance was reported around South Georgia (Brierley, et al.,2002). They reported that krill abundance late (March) austral summer was significantly lower thanthat in January. Such intra-annual variability of krill abundance could explain the abundance
difference among three survey years in V-NW and in V-SW. Effect of intra-annual variability ofkrill abundance should be considered in data from III-E and VI-W where surveys were conducted ineither December or March. The reasons of the seasonal differences of krill biomass could be either
or combination of 1) onshore migration of krill in autumn to winter (Siegel et al., 1997) and 2)
depletion of krill by predators (Brierley et al. 2002).
There were two main categories of limitations to interpret the result of this analysis. First
category of limitation was applied to acoustic survey of krill in general. Those general limitations
were 1) background krill which could not be detected by echo sounder because of low density, 2)

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krill refuge which meant that krill could distribute where the survey vessel could not enter such as
under sea ice and 3) surface krill which meant that krill could distribute shallower than thetransducers (Nicol et al., 2000(b)). Those three general limitations of abundance estimation of krill
using echo sounder would contribute to underestimation of krill biomass. The other category oflimitation was applied specifically to this analysis. Though krill identification using ΔMVBS
between 120 kHz and 38 kHz have been well established, there was some uncertainty associatedspecies identification of mark on echogram because no net sampling was conducted in the surveys
presented here. Along with this, there was no in-situ length frequency and weight data of krill toconvert acoustic backscattering to biomass except the Ross Sea in 2004/2005. The results ofcomparison of biomass between Kaiyo Maru and KS2 suggested that data from two vessels werecomparable. Murase et al. (2006) suggested that krill distributions and the length frequency data forthe purpose of acoustical biomass estimation could be obtained from stomach contents of Antarctic
minke whales. The results of this paper could be updated using krill distributions and the length
frequency data from stomach contents of Antarctic minke whales. Calibration of echo sounder isvery important because subtle parameter setting change will results in large effect on biomass
estimation of krill. Because there was no calibration result in 2002/03, interpretation of the result inthat year may need caution. Demer and Conti (2005) proposed the new TS for E. supreba using
Stochastic Distorted-Wave Born-Approximation (DSDWBA) model. If the new TS applied to our
results, krill biomass would be 2.5 times higher than the current estimates. Methods of TS
estimation would also introduce bias to the biomass estimates.
Over all, the results presented here provided general distribution and biomass patterns ofkrill in the survey area. Following points should be considered to improve the echo sounder survey
in future: 1) survey should be conducted in peak abundance season of krill (January and February)
to minimize seasonal effect on abundance estimation, 2) survey should be conducted in same area insame survey timing to interpret yearly changes, 3) target net sampling should be conducted to
identify species compositions of marks detected by the echo sounder so that appropriate amount ofbackscattering can allocate to krill and 4) calibration must be conducted every year to set
appropriate parameters in the echo sounder.
ACKNOWLEDGEMENT
Authors express thank you to the crews and the researchers who dedicated to collect data in harshenvironmental condition in the Antarctic. Special thanks were given to Ms. Shoko Ohkawa and Ms.
Tomoko Hasegawa who supported the handling of huge amount of echo sounder data. We also
thank Drs. Hiroshi Hatanaka, Seiji Ohsumi and other colleagues at the Institute of Cetacean
Research who made critical comments to improve this manuscript.
REFERENCES

Azzali, M., Leonori, I., De Felice, A. and Russo, A. 2006. Spatial-temporal relationships between
two euphausiid species in the Ross Sea. Chem. Ecol. (Suppl.) 22:219-233.
Atkinson, A, Siegel, V., Pakhomov, E. and Rothery, P. 2004. Long-term decline in krill stock andincrease in salps within the Southern Ocean. Science 432:100-103.
Brierley, A. S., Goss, C., Grant, S. A., Watkins, J. L., Reid, K., Belchier, M., Everson, I., Jessop, M.
J., Afanasyev, V. and Robst, J. 2002. Significant intra-annual variability in krill distribution
and abundance at south Georgia revealed by multiple acoustic surveys during 2000/01.
CCAMLR Sci. 9:71-82.
Branch, T. A., Matsuoka, K. and Miyashita, T. 2004.Evidence for increases in Antarctic blue whales
based on Bayesian modeling. Mar. Mamm. Sci. 20:726-754.
Demer, D. A. and Hewitt, R. P. 1995. Bias in acoustic biomass estimates of Euphausia superba due
to diurnal vertical migration. Deep-sea Res. 42:455-475.
Demer, D. A. and Conti, S. G. 2005. New target-strength model indicates more krill in the Southern
Ocean. ICES J. Mar. Sci. 62:25-32.
7

SC/D06/J21

Greene, C. H., Stanton, T. K., Wiebe, P. H. and McClatchie, S. 1991. Acoustic estimates of Antarctic
krill. Nature 349: 110.
Hewitt, R. P. and Demer, D. A. 1993. Dispersion and abundance of Antarctic krill in the vicinity of
Elephant Island in the 1992 austral summer. Mar. Ecol. Prog. Ser. 99: 29-39.
Hewitt, R. P. and Demer, D. A. 2003. An 8-year cycle in krill biomass density inferred fromacoustic surveys conducted in the vicinity of the South Shetland Islands during the australsummers of 1991-1992 through 2001-2002. Aquat. Living . Res. 16:205-213.
Hewitt, R. P., Watkins, J., Naganobu, M., Sushin, V., Brierley, A. S., Demer, D., Kasatkina, S.,
Takao, Y., Goss, C., Malyshko, A., Brandon, M., Kawaguchi, S., Siegel, V., Trathan, P.,
Emery, J., Everson, I., Miller, D. 2004. Biomass of Antarctic krill in the Scotia Sea inJanuary/February 2000 and its use in revising an estimate of precautionary yield. Deep Sea
Res. II 51:1215-1236.
Johnston, S. J. and Butterworth, D. S. 2004. Updated age-aggregated production modellingassessments of the Southern Hemisphere humpback whale breeding stocks A and C. Paper
SC/56/SH20 presented to 56th Scientific Committee, June 2004 (unpublished). 21pp.
[available from IWC]
Jolly, G. M. and Hampton, I. 1990. A stratified random transect design for acoustic surveys of fishstock. Can. J. Fish. Aquat. Sci. 47: 1282-1291.
Kawamura, A. 1994. A review of baleen whale feeding in the Southern Ocean. Rep. Int. Whal.
Commn. 44: 261-271.
Laws, R. M. 1985. The ecology of the Southern Ocean. Am. Sci. 73: 26-40.
Laws, R. M. 1977. Seals and whales of the southern ocean. Philos. Trans. R. Soc. Lond. (B Biol.
Sci.) 279: 81-96.
Loeb, V. and Siegel, V. 1992. AMLR Program; krill stock structure in the Elephant Island area,
January –March, 1992. U. S. Antarct. J. 214-216.
Mori, M. and Butterworth, D. S. 2006. A first step towards modelling the krill-predator dynamics of
the Antarctic ecosystem. CCAMLR Sci. 13:217-277.
Murase, H., Matsuoka, K., Ichii, T. and Nishiwaki, S. 2000. Relationship between the distribution of
euphausiids and baleen whales in the Antarctic examined using JARPA data. Paper
SC/52/E5 presented to the 52th IWC Scientific Committee, June 2000 (unpublished). 18pp.
[available from IWC]
Murase, H., Matsuoka, K., Ichii, T. and Nishiwaki, S.2002. Relationship between the distribution of
euphausiids and baleen whales in the Antarctic (35°E-145°W). Polar Biol. 25:135-145.
Murase, H., Tamura, T., Matsuoka, K., Nishiwaki, S., Yasuma, H., Matsukura, R., Yabuki, T, Takao,Y., Taki, K., Hayashi, T. and Naganobu, M. 2006. Distribution patterns and biomasses ofAntarctic krill (Euphausia superba) and ice krill (E. crystallorophias) with referece to
Antarctic minke whales in the Ross Sea in 2004/05 using Kaiyo Maru-JARPA joint survey
data. Paper SC/D06/J24 presented to the JARPA Review Meeting, December 2006
(unpublished).
Murphy, E. J., Morris, D. J., Watkins, J. L. and Priddle, J. 1988. Scales of interaction between
Antarctic krill and the environment. In Sahrhage, D. ed.: Springer-Verlag, Berlin. 120-130.
Nicol, S. Constable, A. J. and Pauly, T. 2000 (a). Estimates of circumpolar abundance of Antarctic
krill based on recent acoustic density measurement. CCAMLR Sci. 7:87-99.
Nicol, S., Pauly, T., Bindoff, N. L., Weight, S., Thiele, D., Hosie, G. W., Strutton, P. G. and Woehler,
E. 2000(b). Ocean circulation off east Antarctica affects ecosystem structure and sea-ice
extent. Nature 406: 504-507.
Nishiwaki, S., Ishikawa, H. and Fujise, Y. 2006. Review of general methodology and survey
procedure under the JARPA. Paper SC/D01/J2 presented to the JARPA Review Meeting,
December 2006 (unpublished).

8

SC/D06/J21
Pakhomov, E. A. 2000. Demography and life cycle of Antarctic krill, Euphausia superba, in the
Indian sector of the Southern Ocean: long-term comparison between coastal and open-ocean
regions. Can. J. Fish. Aquat. Sci. 57(Suppl. 3):68-90.
Pauly, T., Nicol, S, Higginbottom, I, Hosie, G and Kitchener, J. 2000. Distribtuion and abundance ofAntarctic krill (Euphusia superba) off east Antarctica (80-150°E) during the Australsummer of 1995/96. Deep-Sea Res. Part II 47:2465-2488.
Siegel, V. 1986. Structure and composition of the Antarctic krill stock in the Bransfield Strait(Antarctic Peninsula) during Second International BIOMASS Experiment (SIBEX). Arch.
Fishc. Wiss. 37: 51-72.
Siegel, V., de la Mare, W. and Loeb, V. 1997. Long term monitoring of krill recruitment andabundance of indices in the Elephant Island area (Antarctic Peninsula). CCAMLR Sci. 4:1935.
Simrad. 1997. Simrad EK500 Scientific Echo Sounder Operation Manual P2170G. Simrad AS
Horten, Norway.
Tynan, T. C. Ecological imporatance of the Southern Boundary of the Antarctic Circumpolar
Current. Nature 392:708-710.
Watanabe, T., Yabuki, T., Suga, T., Hanawa, K., Matsuoka, K. and Kiwada, H. 2006. Results ofoceanographic analyses conducted under JARPA and possible evidence of environmental
changes. Paper SC/D01/J30 presented to the JARPA Review Meeting, December 2006
(unpublished).

9SC/D06/J21

Table 1. Density and biomass of krill in each stratum in Area IV and eastern part of Area III in
1999/2000 and 2001/2002
Year
1999/2000
2001/2002
1999/2000
2001/2002
1999/2000
2001/2002
1999/2000
2001/2002
1999/2000
2001/2002
1999/2000
2001/2002
1999/2000
2001/2002

Stratum
III-E-F
IV-NE
IV-NW
IV-PB
IV-SE
IV-SW
III-E-S

Date
12/5/99-12/26/99
11/29/01-12/24/01
12/27/99-1/11/00
12/25/01-1/8/02
1/11/00-1/26/00
1/9/02-1/25/02
1/28/00-2/18/00
1/26/02-2/8/02
2/18/00-2/29/00
3/6/00-3/9/00
2/10/02-2/21-02
3/1/00-3/6/00
2/22/02-2/27-02
2/28/02-3/8-02

Surveyed
area(n.mile^2)352,919
355,477
226,222247,657
203,752
223,617
22,04728,570Mean
desnsity
2(g/m )
13.2
34.5
20.3
14.2
19.0
18.3
16.7
13.7

Biomass(million t)
16.0
42.1
15.7
12.1
13.3
14.0
1.3
1.3

CV (%)

13
8
5
2
5
5
15
17

Surveyeddistance(n.miles)
1,749
1,116
1,117
165
1,257
582
1,061
1,092

17

926

33,332

16.3

1.9

28.9

14
4
3
3

975
428
432
300

33,781
43,12530,837389,700

20.3
13.7
41.0
56.8

2.3
2.0
4.3
75.9

27.7
21.8
15.9
57.8

Number oftransects

10

29.9
30.2
33.7
50.9
54.1
49.3
22.6
44.0

SC/D06/J21
Table 2. Density and biomass of krill in each stratum in Area V and western part of Area VI from1998/1999 to 2002/2003.

Year
1998/1999
2000/2001
2002/2003
2004/2005
1998/1999
2000/2001
2002/2003
2004/2005
1998/1999
2000/2001
2002/2003
2004/2005
1998/1999
2000/2001
2002/2003
2004/2005
1998/1999
2000/2001
2002/2003
2004/2005
1998/1999
2000/2001
2002/2003
2004/2005

Stratum

VI-W-F

V-NE

V-NW

V-SW

V-SE

VI-W-S

Date
12/11/00-12/31/00
12/3/02-12/30/02
12/7/04-12/23/04
1/1/01-1/23/01
1/5/03-1/25/03
12/26/04-1/5/05
1/14/99-2/2/99
2/10/01-2/23/01
2/11/03-2/20/03
3/5/03-3/7/03
2/3/99-2/21/99
2/25/01-3/19/01
2/21/03-3/5/03
2/27/05-3/7/05
2/22/99-3/13/99
1/24/01-2/9/01
1/27/03-2/9/03
1/16/05-2/13/05
3/14/99-3/28/99-

Surveyed
area(n.mile^2)289,954308,374
278,538
348,548
345,010336,138
314,710
270,666mean
desnsity
2(g/m )
3.4
1.5
0.5
11.6
5.7
3.2
21.7
1.3

Biomass(million t)
3.4
1.6
0.4
13.9
6.8
3.6
23.4
1.2

CV (%)

5
14
10
5
9
6
5
4

Surveyeddistance(n.miles)
658
1,810
736
896
1,329
471
1,405
565

5

805

266,896

10.1

9.3

25.4

17
13
5
5
13
15
10
12
12
-

1,152
857
377
272
541
1,401
775
1,448
590
-

48,36180,50379,07251,44924,795
148,831
68,928212,214287,627
-

25.3
8.6
16.8
5.9
24.7
6.5
8.3
3.2
0.2
-

4.2
2.4
4.6
1.0
2.1
3.3
2.0
2.4
0.2
-

33.5
49.4
20.0
49.0
36.0
30.5
27.8
28.2
67.0
-

Number oftransects

11

60.6
34.2
38.6
27.4
27.3
37.0
20.0
19.4

SC/D06/J21

Table 3. Estimated biomass of krill in Area IV and V from 1998/1999 to 2004/2005.

Area

IV

V

Year

Surveyedarea
2(n.mile )Numberoftranscts

Surveyeddistance(n.mile)Biomass(Million t)

CV (%)

1999/2000
2001/2002
1998/1999
2000/2001
2002/2003
2004/2005

528,477
564,463
387,867
848,548759,906
599,801

59
52
35
37
29
23

4,789
3,246
3,098
3,719
3,286
2,191

34.2
34.1
29.7
20.7
22.6
7.0

26.2
27.3
16.6
19.8
14.1
22.6

12

Note

No survey in NE

No survey in NW

SC/D06/J21
Table 4. Density and biomass of E. superba and E. crystallorophias in the Ross Sea in 2005 (from Mureae et al. 2006).

2

Weighted mean ρ (g/m )2
Surveyed area (n.mile )Biomass (million t)
CV (million t)

Kaiyo
Maru
5.4
2.04
0.44

E. superba
KyoshinMaru #2
2.6
110792
1.00
0.36

Total
3.9
1.46
0.32

13

E. crystallorophias
Kaiyo Kyoshin
Total
Maru Maru #2
3.4
1.6
2.2
106800
1.26
0.57
0.82
0.21
0.26
0.18

Gross Total
3.1
2175922.28
0.22

SC/D06/J21

1999/2000

2001/2002

Fig. 1. Distributions and densities of krill in Area IV and eastern part of Area III in 1999/2000 and
2001/2002. Densities were shown as mean backscattering area per square n. mile of survey transect(SA) in square root scale. Bottom depth contour lines:▬ (500m), ▬ (1000m), ▬ (1500m) and ▬(2000m). Ice edge line: ▬.

14

SC/D06/J21

1998/1999

2002/2003

2000/2001

2004/2005

Fig. 2. Distributions and densities of krill in Area V and western part of Area VI from 1998/1999 to
2004/2005. Densities were shown as mean backscattering area per square n. mile of survey transect(SA) in square root scale. Bottom depth contour lines:▬ (500m), ▬ (1000m), ▬ (1500m) and ▬(2000m). Ice edge line: ▬.

15