SC/J09/JR23

Temporal trends and factors affecting mercury levels incommon minke, Bryde’s and sei whales and their prey species
in the western North Pacific
GENTA YASUNAGA AND YOSHIHIRO FUJISEThe Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan.
Contact e-mail: yasunaga@cetacean.jp

ABSTRACTTo examine accumulation features and yearly changes of total Hg in the western North Pacific, total Hg levels insamples from zooplankton (krill Euphausia pacifica; copepods Neocalanus spp. and Calanus sp. ), pelagic fishes(Japanese anchovy Engraulis japonicus; Pacific saury Cololabis saira; walleye pollock Theragra chalcogramma;
mackerels; Pacific pomfret) and baleen whales (common minke whales Balaenoptera acutorostrata; Bryde’s whales B.
edeni; sei whales B. borealis), were measured. Total Hg levels in krill and copepods were in the range <0.001-0.013 and0.003-0.010 ppm dry wt., respectively. Total Hg levels in the pelagic fishes were in the order: Pacific pomfret(0.232±0.027 ppm wet wt.) > walleye pollock (0.045) ≥Pacific saury (0.039±0.016) ≒ Japanese anchovy (adult)(0.037±0.025) > Japanese anchovy (larval fish) (0.005±0.003). Total Hg levels in muscle samples of mature baleen
whales were in the order: common minke whales (0.22±0.07) > sei whales (0.052 ±0.009) ≒ Bryde’s whales(0.046±0.008). Yearly changes of total Hg levels in zooplankton and pelagic fishes were not observed in the period
1995-2007. Apart from common minke whales from sub-area 9, significant yearly changes of total Hg levels in whales,
were not observed. Results of a multiple linear regression analysis showed that variation of Hg levels in common minke
whales from sub-area 9 was affected by sampling year and sampling region. Some considerations with mercury levels
in prey species and prey composition suggest that these changes of Hg levels in sub-area 9 reflect change in food habitat
rather than the changes in accumulation levels of Hg in the environment in the period considered. Therefore changes infood habitat of whales are important for predicting changes of Hg levels in both baleen whales and their environment.
KEYWORDS: COMMON MINKE WHALE; BRYDE’S WHALE; SEI WHALE; NORTH PACIFIC; MERCURY;TEMPORAL TREND, SPATIAL TRENDINTRODUCTION
Pollutants accumulate through the food chain in a marine ecosystem. Because cetaceans are located at the top of thefood chain they are frequently used for monitoring the pollutants in the marine environment (Sanpera et al., 1993;
Borrell and Reijnders, 1999). Further cetaceans are mobile and long-lived animals, and these characteristics mean thatpollutants can be monitored in wide areas and integrated in some way over time..
In JARPN II, surveys were designed so that quantitative behaviour and fate of the pollutants in the marine environment
can be monitored. The present study examines levels and temporal changes of total Hg in the western North Pacific,
through the analysis of top predators such as whales and whale’s prey species such as zooplankton and fishes collectedfrom their stomachs. The analysis of this pollutant in both predators and prey species is important as the level of Hg in
predators reflect in part their feeding habit. To understand the pattern of accumulation of Hg in whales it is important toconsider some biological information such as sex and sexual maturity. Such information is considered in this study.
This study examines level and temporal changes of Hg levels in two zooplanktons, six pelagic fishes species and threebaleen whale species. For the later group sex and sexual maturity information obtained during JARPN II surveys is
considered to assist in the interpretation of factors affecting Hg levels

1

MATERIALS AND METHODS
Samples and sampling method
Zooplanktons (krill and copepods) were collected by JARPN II researchers from the forestomach of common minke,
Bryde’s and sei whales from sub-areas 7, 8 and 9 in the surveys conducted in the period from 1994 to 2007. Table 1
shows the sample sizes and moisture content of the planktons sampled, by species and survey. The plankton samples
were frozen and shipped to the laboratory and stored at -20˚C until chemical analysis.
Pelagic fishes (Japanese anchovy; Pacific saury; walleye pollock; Mackerels; and Pacific pomfret) were collected by
JARPN II researchers from the forestomach of common minke, Bryde’s and sei whales from sub-areas 7, 8 and 9 in thesurveys conducted in the period from 1994 to 2007. Table 2 shows the sample sizes and moisture content of the fishes
sampled, by species and survey. The fish samples were frozen and shipped to the laboratory and stored at -20˚C until
chemical analysis.
Muscle tissues from the common minke whales (Okhotsk Sea-West Pacific stock) from sub-areas 7, 8 and 9 (offshore
component of JARPN II), off-Sanriku and off-Kushiro (coastal component of JARPN II), Bryde’s whales from subareas 8 and 9 and sei whales from sub-area 9 were collected by JARPN II researchers in the surveys conducted in the
period from 1994 to 2007. The muscle tissues were excised from the medial region part of the body. Tables 3 and 4
show the sample sizes, maturity stage and body length of male animals, by species, sub-area and survey. The muscle
samples were frozen and shipped to the laboratory and stored at -20˚C until chemical analysis. In this study weconsidered information on the body length and maturity status of male whales. Males of minke, Bryde's and sei whales
were defined as sexually mature by testis weight (larger side) of more than 290g, 560g and 1,090g, respectively (Bandoet al., unpublished data). Only minke whales from the Okhotsk Sea-West Pacific stock as identified by the
microsatellite analysis (Kanda et al., 2009), were used.

Laboratory analysis
In the laboratory the whole body of zooplanktons and fishes were rinsed with milli-Q water, weigthed, dried for 12 hr.
at 80˚C and reweigthed. The samples were homogenized using electrical blender and an agate motar. The muscle
samples were stripped externally to avoid contamination and then homogenized using electrical blender.
For total Hg analysis, the homogenate samples (100 to 150 mg) were set on a ceramic boat and were subjected to Coldvapor atomic absorption spectrometry with Heat-vaporization, gold amalgamation method (Nippon Instruments Co.,
MA-2000). Accuracy and precision of the methods were confirmed using standard materials, DORM-2 (NRCC: muscleof dogfish).
Statistical analysis
The yearly trend of total Hg levels in zooplanktons, fishes and whales were assessed by Ordinal Regression test
(Polytomous Universal Model: PLUM). Furthermore, in order to examine the yearly trend of total Hg levels in thecontext of other factors in whales, multiple linear regression analyses, were conducted (Zar, 1999). The following
independent variables: “sampling year” , “sampling date (1 May = day 1)”, “sampling latitude”, “sampling longitude”,“body length” and “blubber thickness”, were allowed, and all parameters were normalized. Temporal differences
between JARPN and JARPN II in muscular total Hg levels of immature common minke whales were tested by
ANCOVA with body length as covariate, and all parameters were normalized. A p value of less than 0.05 was used as acriterion on statistical significance in all tests. These statistical analyses were executed by SPSS ver.11 for Windows(SPSS Co. Ltd.).
RESULTS AND DISCUSSION
Zooplankton
Total Hg levels in krill and copepods from the western North Pacific exhibited ranges from <0.001-0.013 and 0.0030.010 ppm dry wt., respectively (Table 1). Total Hg levels in zooplanktons, krill and copepods fed by common minke,
Bryde’s and sei whales were similar. Plots of total Hg levels in krill during 1994 and 2006 against their sampling year
were shown in Figure.1. No significant trend in total Hg levels in krill was observed for the period 1994-2006 (Table 5).
The result suggests that total Hg level in low trophic organisms is stable.

Pelagic fish
Table 2 shows the total Hg levels in the Japanese anchovy (adult), Japanese anchovy (larval fish), Pacific saury, walleye
pollock, mackerels and Pacific pomfret. The total Hg levels in fish were in the order: Pacific pomfret (0.232±0.027
ppm wet wt.) > walleye pollock (0.045 ppm wet wt.) ≥ Pacific saury (0.039±0.016) ≒Japanese anchovy (adult) (0.037±0.025) > Japanese anchovy (larval fish) (0.005±0.003). Total Hg levels in Japanese anchovy (larval fish) weresimilar to those of the zooplanktons. Plots of total Hg levels against the sampling years in the Japanese anchovy (adult)
2

SC/J09/JR23
and Pacific saury for the period 1995-2007 were shown in Figures 2 and 3. No significant trend in total Hg levels inJapanese anchovy (adult) was observed for the period 1995-2007 (Table 6). However, The total Hg level in Pacificsaury showed significant differences in the period from 1995 to 2007 (Table 7). Furthermore, a multiple regression
analysis was done to determine the extent of effect of individual factors such as sampling year, body length, season andsampling location (longitude and latitude). Only body length were significantly selected (Table 8). This result suggestthat total Hg levels in pelagic fishes from western North Pacific in the study period is stable.

Baleen whale
Tables 3 and 4 show the total Hg levels in common mike whales and Bryde’s/sei whales, respectively. Total Hg levels
were in the order: common minke whales (0.22±0.07 ppm wet wt.) > sei whales (0.052 ±0.009) ≒Bryde’s whales(0.046±0.008). Differences in feeding habitat among whale species and trophic levels of preys might be one of thereasons for such differences. It is known that common minke whales selectively feed on relatively higher trophic
organisms, mainly pelagic fish such as Pacific saury and Japanese anchovy (Tamura et al., 2002), which are different
from the prey items of Bryde’s and sei whales, which feed mainly on krill and copepod (Tamura et al., 2002; Tamura etal., 2009).
Plots of total Hg levels against their sampling year is shown for common minke (Figures 4-8 for different sub-areas),
Bryde’s (Figure 9) and sei (Figure 10) whales during 1994 and 2007. Tables 9, 10 and 11, 12 and 13 show the results of
the regression test for common minke whales in sub-areas 7, 8 and 9 (offshore component), Kushiro, Sanriku (coastal
component), respectively. Tables 14 and 15 show these results for Bryde’s (sub-areas 8 and 9) and sei (sub-area 9)
whales, respectively.
In minke whales from sub-area 7 and Sanriku, Bryde’s whales from sub-areas 8 and 9 and sei whales from sub-area 9
the Hg levels were not significantly correlated with sampling year. However Hg levels in minke whales from sub-areas
8 and 9 were correlated negatively with sampling year and those from Kushiro were correlated positively with samplingyear.
To examine the factors affecting total Hg levels trends in common minke whales, multiple regression linear analyses
were conducted. For minke whales in sub-areas 8 and 9 two periods were considered: 1994-2007 and 2000-2007. Thiswas done because the trend of Hg levels appear to change around year 2000 (Figures 5 and 6).
The results for minke whales in sub-areas 8, 9 and Kushiro are shown in Tables 16, 17 and 18, respectively. In sub-area
8 (period 2000-2007) and Kushiro, no significant correlation with the parameters was found. However, in sub-areas
8 (period 1994-2007) and 9 (both periods) significant correlation was found for the following parameters: blubber
for sub-area 8; year (-), date (-) and latitude (+) for sub-area 9 (1994-2007); year (+) and longitude (-) for sub-area
9 (2000-2007).
These results suggest that total Hg levels in muscles of three baleen whales in are stable except in the case of common
minke whales from sub-area 9. In this case a decreasing trend was observed in a JARPN period (1994-1999) while thatan increasing trend was observed in the JARPN II period (2000-2007).
The total Hg level in immature common minke whales from sub-areas7, 8 and 9 were compared between JARPN(1994-1999) and JARPN II (2000-2007). To take into account the age-related accumumulation, plots of total Hgconcentrations and body length were made (Figure 11). The results of the ANCOVA for Hg levels in immaturecommon minke whales between JARPN and JARPN II periods are shown in Table 19, for coastal (sub-area 7) and
offshore (sub-areas 8 and 9) regions. The slopes of the linear regression curves were significant different in thecase of sub-areas 8 and 9 (p<0.05, Fig. 11b). In the case of sub-area 7 not significant differences were found. Thisfinding coincide with the results of mature minke whales that total Hg levels in offshore minke whales weresignificantly decreased between two periods, while those from coastal region did not showed any yearly trend.

Multiple regression analyses for mature common minke whales from sub-area 9 selected parameters, such as
sampling latitude and longitude. It has been reported that common minke whales locally feed Pacific pomfret in
sub-area 9 (Tamura et al., 1998) and minimal armhook squid in north-eastern of sub-area 9 (Konishi and Tamura,2007), while they considerably feed Japanese anchovy, Pacific saury and krill (Tamura et al., 2009). Total Hglevels in these mesopelagic fishes, such as Pacific pomfret (Hg: 0.215 - 0.264 ppm wet wt.) were higher thanthose in pelagic fishes, such as Japanese anchovy (Hg: 0.009 - 0.064) and Pacific saury (Hg: 0.009 - 0.064), andzooplanktons (Hg: <0.001 - 0.013). Consequently, yearly change of total Hg levels in common minke whales
from sub-area 9 might be affected by change of the food habitat rather than the difference in background levels of
Hg in the western North Pacific in the period.

3

REFERENCES
Borrell, A. and Reijnders, P.J.H. 1999. Summary of temporal trends in pollutant levels observed in marine mammals. J.
Cetacean Res. Manage., (Special Issue 1), 149-155.
Kanda, N., Goto, M., Kishiro, T., Yoshida, H., Kato, H. and Pastene, L.A. 2009. Individual identification and mixing of
the J and O stocks around Japanese waters examined by microsatellite analysis. Paper SC/J09/JR26. presented to the
JARPN II Review Workshop, Tokyo, January 2009 (unpublished). 9pp.
Konishi, K. and Tamura, T. 2007. Occurrence of the minimal armhook squids Berryteuthis anonychus(Cephalopoda:Gonatidae) in the stomachs of common minke whales Balaenoptera acutorostrata in the western North
Pacific. Fisheries Science 73:1208-10.
Sanpera, C., Capelli, R., Minganti, V. and Jover, L. 1993. Total and organic mercury in North Atlantic fin whales. Mar.
Pollut. Bull. 26:135-139.

Tamura, T., Fujise, Y. and Shimazaki, K. 1998. Diet of minke whales Balaenoptera acutorostrata in the
Northernwestern part of the North Pacific in summer, 1994 and 1995. Fisheries Science 64:71-76.
Tamura, T. and Fujise, Y. 2002. Geographical and seasonal changes of the prey species of minke whale in the
Northwestern Pacific. ICES J. Mar. Sci. 59:516-528.
Tamura, T., Konishi, K., Isoda, T., Okamoto, R. and Bando, T. 2009. Prey consumption and feeding habits of common
minke, sei and Bryde’s whales in the western North Pacific. Paper SC/J09/JR16 presented to the JARPN II Review
Workshop, Tokyo, January 2009 (unpublished). 36pp.

4

SC/J09/JR23
Table 1. Total Hg concentrations, moisture contents and sampling data of krill and copepods in stomach contents of baleen whales taken fromJARPN and JARPN II researches during a period from 1994 to 2007.
Hg (ppm wet wt)
Hg (ppm dry wt)
Moisture content (%)
Species
Tissue
Year
n*
Area
0.008
0.048
84
Krill
whole
1994
2
9
body
(2Mi)
( 0.006 - 0.010 ) ( 0.044 - 0.053 ) (81 - 86
)
1996
5
7, 8
0.004 ± 0.003
0.032 ± 0.023
85 ± 3(5Mi)( 0.002 - 0.009 ) ( 0.016 - 0.069 ) (81 - 88)2002
4
90.004 ± 0.001
0.027 ± 0.009
85 ± 2(1Mi, 3Se)
( <0.001 - 0.005 ) ( <0.001 - 0.037 ) (83 - 87
)
2005
3
7, 8
0.003 ± 0.003
0.017 ± 0.014
84 ± 2(2Se, 1Br)
( 0.001 - 0.006 ) ( 0.007 - 0.033 ) (82 - 86)2006
5
90.007 ± 0.005
0.038 ± 0.022
84 ± 3(5Br)( 0.003 - 0.013 ) ( 0.019 - 0.069 ) (81 - 87)
total
19
7, 8, 90.005 ± 0.003
0.030 ± 0.019
85 ± 2(8Mi, 5Se, 6Br)
( 0.001 - 0.013 ) ( 0.007 - 0.069 ) (81 - 88)
Copepods
whole
2007
5
9
0.005 ± 0.003
0.047 ± 0.024
88 ± 2body(5Se)( 0.003 - 0.010 ) ( 0.021 - 0.081 ) (87 - 91)*: Whale species (Mi: common minke whale, Se: Sei whale, Br: Bryde's whale) and numbers are shown in parentheses.

Table 2. Hg concentrations, moisture contents and sampling data of Japanese anchovy, Pacific saury, walleye pollock, marckerels and Pacific pomfret and instomach contents of baleen whales taken from JARPN and JARPN II researches during a period from 1994 to 2007.
Body length (mm)Hg (ppm wet wt)
Hg (ppm dry wt)
Moisture content (%)
Species
Tissue Yearn*
Area
Japanese anchovy whole1995
39
139 ± 70.068 ± 0.008±±(adult)body(3Mi)( 131 - 145) ( 0.058 - 0.072 ) () ()
121 ± 30.069 ± 0.015
0.233 ± 0.068
70 ± 3
2003
4
8
(4Mi)
( 119 - 125) ( 0.052 - 0.088 ) ( 0.170 - 0.320 ) (65 - 73)2004
3
9119 ± 100.022 ± 0.005
0.070 ± 0.013
69 ± 2(1Se, 2Br)
( 110 - 130) ( 0.018 - 0.028 ) ( 0.062 - 0.085 ) (67 - 71)2006
5
9108 ± 50.011 ± 0.002
0.034 ± 0.007
69 ± 4(4Se, 1Br)
( 100 - 115) ( 0.008 - 0.015 ) ( 0.026 - 0.043 ) (64 - 75
)
2007
5
7, 8
122 ± 130.045 ± 0.022
0.153 ± 0.067
72 ± 3(4Mi, 1Br)
( 101 - 133) ( 0.011 - 0.071 ) ( 0.046 - 0.230 ) (69 - 76)
total
20
7, 8, 9123 ± 110.037 ± 0.025
0.122 ± 0.091
70 ± 3(11Mi, 5Se, 4Br)
( 100 - 145) ( 0.008 - 0.088 ) ( 0.026 - 0.320 ) (64 - 76)
Japanese anchovy whole
2002
4
7, 8
51 ± 80.004 ± 0.001
0.021 ± 0.004
79 ± 1(larval fish)
body
(4Br)
(
42 - 62) ( 0.004 - 0.005 ) ( 0.018 - 0.025 ) (78 - 79
)
2004
2
9
53 ±
0.007 ±
0.032 ±
79 ±(1Se, 1Br)(
33 - 126) ( 0.003 - 0.010 ) ( 0.017 - 0.046 ) (78 - 81)
total
6
7, 8, 952 ± 150.005 ± 0.003
0.025 ± 0.011
79 ± 1(1Se, 5Br)(
33 - 74) ( 0.003 - 0.010 ) ( 0.017 - 0.046 ) (78 - 81)
Pacific saury
whole
1995
9
9
270 ± 410.039 ± 0.015
±
±
body
(9Mi)
( 200 - 310) ( 0.017 - 0.058 ) (
) (
)
1996
4
8
248 ± 55
0.028 ± 0.020
±
±
(4Mi)
( 195 - 315) ( 0.014 - 0.058 ) (
) (
)
2002
5
9
279 ± 450.035 ± 0.014
0.075 ± 0.026
55 ± 10(4Mi, 1Se)
( 200 - 310) ( 0.011 - 0.045 ) ( 0.037 - 0.100 ) (42 - 70)300 ± 112003
5
90.050 ± 0.004
0.118 ± 0.021
57 ± 5(4Mi, 1Se)
( 282 - 313) ( 0.043 - 0.053 ) ( 0.092 - 0.140 ) (51 - 63)2004
59285 ± 26
0.032 ± 0.014
0.071 ± 0.023
57 ± 6(5Mi)( 248 - 308) ( 0.017 - 0.048 ) ( 0.044 - 0.092 ) (48 - 63
)
2005
5
8, 9
296 ± 90.054 ± 0.009
0.134 ± 0.033
59 ± 4(2Mi, 3Se)
( 283 - 309) ( 0.044 - 0.064 ) ( 0.100 - 0.170 ) (54 - 66)2006
59290 ± 140.042 ± 0.013
0.096 ± 0.036
55 ± 6(5Mi)( 272 - 307) ( 0.023 - 0.055 ) ( 0.057 - 0.150 ) (48 - 63)2007
3
9272 ± 36
0.028 ± 0.026
0.082 ± 0.077
67 ± 1(1Mi, 2Se)
( 231 - 300) ( 0.009 - 0.058 ) ( 0.027 - 0.170 ) (66 - 67
)
total
41
8, 9
282 ± 33
0.038 ± 0.015
0.097 ± 0.039
58 ± 7(34Mi, 7Se)
( 195 - 325) ( 0.009 - 0.064 ) ( 0.027 - 0.170 ) (42 - 70)
Mackerels
whole
1996
5
7
192 ± 160.020 ± 0.002
±
±
body
(5Mi)
( 170 - 215) ( 0.018 - 0.023 ) () ()
Pacific pomfret
whole
1994
3
9
420 ± 180.232 ± 0.027
±
±
body
(3Mi)
( 405 - 440) ( 0.215 - 0.264 ) () ()
Walleye pollock whole
1996
2
7
504 ±
0.045 ±
±
±
body
(2Mi)
( 485 - 522) ( 0.038 - 0.051 ) () ()*: Whale species (Mi: common minke whale, Se: Sei whale, Br: Bryde's whale) and numbers are shown in parentheses.

5Table 3. Biological data and musclar mercury levels of common minke whales (males) from western North
Pacific during a period from 1994 to 2007.
musclar Hgbody length
blubber thicknessnsubareayear
matuarity(cm)(ppm wet wt.)(m)
0.22 ± 0.05 ）
1996
18 (
7.34 ± 0.31 ） (3.1 ± 0.4
7
mature）(0.20 ± 0.05 ）39 (7.45 ± 0.34 ） (2.6 ± 0.4
1998
mature）(0.19 ± 0.04 ）32 (7.38 ± 0.29 ） (3.6 ± 0.8
1999
mature）(0.23 ± 0.02 ）5 (7.19 ± 0.23 ） (3.1 ± 0.3
2000
mature）(7.44 ± 0.32 ） (2.4 ± 0.5
0.21 ± 0.04 ）
27 (
2001
mature）(0.22 ± 0.03 ）34 (7.52 ± 0.27 ） (3.7 ± 0.7
2002
mature）(11 (7.41 ± 0.39 ） (2003
2.4 ± 0.5
0.19 ± 0.08 ）mature）(0.22 ± 0.02 ）7 (7.46 ± 0.32 ） (4.0 ± 0.6
2004
mature）(7.50 ± 0.31 ） (
2005
19 (
3.2 ± 0.9
0.27 ± 0.04 ）mature）(15 (2006
7.40 ± 0.40 ） (2.3 ± 0.4
0.22 ± 0.05 ）mature）(44 (3.0 ± 0.7
0.23 ± 0.04 ）7.48 ± 0.26 ） (2007
mature
）(
8
1996
10 (
7.40 ± 0.45 ） (2.7 ± 0.5
0.24 ± 0.06 ）mature）(1997
7.44 ± 0.36 ） (3.5 ± 0.6
26 (0.27 ± 0.06 ）mature）(1998
30 (0.23 ± 0.05 ）7.53 ± 0.25 ） (2.6 ± 0.4
mature）(2001
14 (7.74 ± 0.36 ） (2.4 ± 0.3
0.21 ± 0.04 ）mature）(2002
5 (7.71 ± 0.21 ） (3.2 ± 0.6
0.20 ± 0.11 ）mature）(7.52 ± 0.23 ） (2.4 ± 0.4
0.18 ± 0.06 ）
2003
25 (
mature）(2006
27 (7.52 ± 0.24 ） (2.8 ± 0.6
0.21 ± 0.05 ）mature）(2007
12 (7.55 ± 0.35 ） (2.3 ± 0.5
0.22 ± 0.05 ）mature）(7.46 ± 0.31 ） (
1994
9
17 (
3.5 ± 0.7
0.35 ± 0.17 ）mature）(74 (0.27 ± 0.06 ）7.43 ± 0.34 ） (1995
3.1 ± 0.5
mature）(199740 (7.38 ± 0.37 ） (3.1 ± 0.5
0.24 ± 0.11 ）mature）(2000
11 (7.47 ± 0.26 ） (2.6 ± 0.5
0.16 ± 0.03 ）mature）(2001
19 (7.68 ± 0.30 ） (2.5 ± 0.4
0.19 ± 0.05 ）mature）(20 (7.54 ± 0.21 ） (3.0 ± 0.6
0.21 ± 0.05 ）2002
mature）(2003
28 (7.50 ± 0.32 ） (2.9 ± 0.6
0.18 ± 0.05 ）mature）(2004
50 (7.47 ± 0.21 ） (3.9 ± 0.7
0.20 ± 0.07 ）mature）(2005
28 (7.48 ± 0.32 ） (3.4 ± 0.6
0.17 ± 0.05 ）mature）(7.56 ± 0.30 ） (3.4 ± 0.6
0.28 ± 0.08 ）
2006
16 (
mature）(7.56 ± 0.20 ） (2.2 ± 0.3
0.18 ± 0.09 ）2007
4 (mature）(0.21 ± 0.06 ）14 (7.22 ± 0.34 ） (2002
Kushiromature
±
）(
2004
24 (
7.40 ± 0.28 ） (0.19 ± 0.03 ）mature
±
）(
2005
25 (
0.25 ± 0.05 ）7.44 ± 0.32 ） (mature±）(0.22 ± 0.03 ）
2006
10 (
7.50 ± 0.30 ） (mature±）(0.23 ± 0.04 ）11 (7.45 ± 0.25 ） (2007
mature±）(0.18 ± 0.04 ）7.15 ± 0.35 ） (7 (2003
Sanrikumature
±
）(
2005
3 (
7.27 ± 0.13 ） (0.29 ± 0.02 ）mature±）(2006
0.20 ± 0.05 ）8 (7.22 ± 0.32 ） (mature±）(7.44 ± 0.24 ） (0.23 ± 0.05 ）9 (2007
mature±）(821 (7.46 ± 0.31 ） (3.0 ± 0.7
0.22 ± 0.07 ）total 1994-2007 mature）(
2.8 ± 0.8
0.15 ± 0.03 ）7
5.64 ± 0.49 ） (1996-1999 immature 17 (）(
2.6 ± 0.5
0.14 ± 0.07 ）5.72 ± 0.76 ） (2000-2007 immature 51 (）(
6.21 ± 0.71 ） (88 (
2.5 ± 0.3
0.18 ± 0.06 ）1996-1998 immature）(
2.4 ± 0.6
5.74 ± 0.72 ） (0.08 ± 0.05 ）2003-2007 immature 12 (）(
0.17 ± 0.07 ）6.05 ± 0.52 ） (2.9 ± 0.6
9
1994-1997 immature 13 (）(
5.56 ± 0.87 ） (2.7 ± 0.5
0.10 ± 0.09 ）2000-2007 immature 14 (）(
0.12 ± 0.06 ）5.65 ± 0.64 ） (Kushiro 2002-2007 immature 46 (±）(
0.11 ± 0.05 ）5.56 ± 0.72 ） (Sanriku 2003-2007 immature 29 (±）(
5.71 ± 0.70 ） (2.7 ± 0.6
0.13 ± 0.07 ）total 1994-2007 immature 190 (）(

Table 4 Biological data and musclar mercury levels of Bryde's and sei whales (males) from western
North Pacific during a period from 2002 to2007.
musclar Hgbody lengthnspeciessubareayear
matuarity(m)(ppm wet wt.)
82002
5 ( 12.67 ± 0.43 ） ( 0.051 ± 0.008
Bryde's whale
mature8, 9
2004
5 ( 12.59 ± 0.36 ） ( 0.045 ± 0.008
mature82006
5 ( 12.36 ± 0.47 ） ( 0.040 ± 0.009
mature8, 9
2007
5 ( 12.63 ± 0.35 ） ( 0.049 ± 0.008
mature20 ( 12.56 ± 0.39 ） ( 0.046 ± 0.008
total
2002-2007
mature92002
5 ( 13.60 ± 0.16 ） ( 0.050 ± 0.012
Sei whale
mature92003
5 ( 13.80 ± 0.43 ） ( 0.057 ± 0.007
mature92004
5 ( 13.61 ± 0.04 ） ( 0.050 ± 0.009
mature92005
5 ( 13.54 ± 0.38 ） ( 0.049 ± 0.011
mature92006
5 ( 13.84 ± 0.51 ） ( 0.052 ± 0.006
mature92007
5 ( 13.92 ± 0.08 ） ( 0.058 ± 0.010
mature30 ( 13.72 ± 0.33 ） ( 0.052 ± 0.009
total
2002-2007
mature

6

）
）
）
）
）
）
）
）
）
）
）
）

SC/J09/JR23
Table 5. Results of Yealy trend of total Hg levels in krill during 1994 and 2006 fromwestern North Pacific by the PLUM - Ordinal regression test.
PearsonDeviance

Chi-Square
39.37
36.11

df
45
45

Sig.
0.709
0.825

Table 6. Results of Yealy trend of total Hg levels in Japanese anchovy during 1995
and 2007 from western North Pacific by the PLUM - Ordinal regression test.
PearsonDeviance

Chi-Square
47.39
32.06

df
64
64

Sig.
0.94
1.000

Table 7. Results of Yealy trend of total Hg levels in Pacific saury during 1995 and2007 from western North Pacific by the PLUM - Ordinal regression test.

PearsonDeviance

Chi-Square
226.42108.44

df
182
182

Sig.
0.014
1.000

Table 8 Results of multiple linear regression analyses with "total Hg levels in Pacific saury"as the dependent variable.
a) Model of regression
R
Model
1
0.800

R2
0.640

R2'
0.589

b) Analysis of Variance TableModel
Sum of Squares
26.998Regression
15.189Residual
42.188
Total

DF
5
35
40

Mean Square
5.400
0.434

F value
12.442

P value
0.000c) Variables
Model
Constant
year
date
latitudelongitude
body length

SE
0.104
0.125
0.252
0.257
0.118
0.113

B'

T
-0.025-0.075-0.804-0.2970.675
6.467

P value
0.980
0.455
0.427
0.768
0.504
0.000

B
-2.63E-03-9.41E-02-0.203-7.64E-02
7.95E-02
0.730-0.088-0.187-0.070
0.075
0.735

7

Table 9. Results of Yealy trend of total Hg levels in common minke whales (mature,
O stock) during 1996 and 2007 from western North Pacific sub-area 7 by the PLUM
- Ordinal regression test.
PearsonDeviance

Chi-Square810.35508.68

df
820
820

Sig.
0.588
1.000

Table 10. Results of Yealy trend of total Hg levels in common minke whales(mature, O stock) during 1996 and 2007 from western North Pacific sub-area 8 by
the PLUM - Ordinal regression test.
PearsonDeviance

Chi-Square693.21404.36

df
630
630

Sig.
0.041
1.000

Table 11. Results of Yealy trend of total Hg levels in common minke whales(mature, O stock) during 1994 and 2007 from western North Pacific sub-area 9 by
the PLUM - Ordinal regression test.
PearsonDeviance

Chi-Square
1994.78748.83

df
1590
1590

Sig.
0.000
1.000

Table 12. Results of Yealy trend of total Hg levels in common minke whales(mature, O stock) during 2002 and 2007 from off Kushiro by the PLUM - Ordinal
regression test.
Sig.
Chi-Squaredf
184.20124
0.000
Pearson119.73124
0.592
Deviance
Table 13. Results of Yealy trend of total Hg levels in common minke whales(mature, O stock) during 2003 and 2007 from off Sanriku by the PLUM - Ordinal
regression test.
PearsonDeviance

Chi-Square
29.73
30.17

df
42
42

Sig.
0.922
0.913

Table 14. Results of Yealy trend of total Hg levels in Bryde's whales (mature)
during 2002 and 2007 from western North Pacific sub-area 8, 9 by the PLUM Ordinal regression test.
PearsonDeviance

Chi-Square
50.64
46.196

df
39
39

Sig.
0.100
0.199

Table 15. Results of Yealy trend of total Hg levels in sei whales (mature) during
2002 and 2007 from western North Pacific sub-area 9 by the PLUM - Ordinal
regression test.
PearsonDeviance

Chi-Square
123.18
88.98

df
100
100

Sig.
0.058
0.777

8

SC/J09/JR23
Table 16 Results of multiple linear regression analyses with "total Hg levels in muscles ofcommon minke whales from sub-areas 8" as the dependent variable.
a) 1994-2007
Model of regression
R
Model
R2
R2'
1
0.386
0.149
0.113
Analysis of Variance TableModel
Sum of Squares
22.029Regression
125.971
Residual
148.000
Total

DF
6
142
148

Mean Square
3.672
0.887

F value
4.139

P value
0.001

Variables
B
Model
Constant-7.324E-10
year-0.195date-5.031E-02
latitude7.348E-02
longitude-8.814E-02
0.132
body length
0.245
blubber thickness

SE
0.077
0.107
0.217
0.221
0.104
0.080
0.086

B'
-0.195-0.0500.073-0.088
0.132
0.245

T
0.000
-1.822-0.2320.332-0.851
1.645
2.867

P value
1.000
0.071
0.817
0.740
0.396
0.102
0.005

b) 2000-2007
Model of regression
R
Model
1
0.369

R2
0.136

R2'
0.068

Analysis of Variance TableModel
Sum of Squares
10.148Regression
64.256
Residual
74.404
Total

DF
6
76
82

Mean Square
1.691
0.845

F value2

P value
0.076

Table 17 Results of multiple linear regression analyses with "total Hg levels in muscles ofcommon minke whales from sub-areas 9" as the dependent variable.
a) 1994-2007
Model of regression
R
Model
R2
R2'
1
0.444
0.197
0.181
Analysis of Variance TableModel
Sum of Squares
60.315Regression
245.685
Residual
306.000
Total

DF
6
300
306

Mean Square
10.0530.819

F value
12.275

P value
0.000

Variables
B
Model
Constant
2.92E-03-0.399year
date-0.363latitude3.450E-01
longitude-6.219E-02
body length6.905E-02
blubber thickness 9.920E-02

SE
0.052
0.053
0.112
0.112
0.054
0.053
0.053

B'
-0.3993630500.345-0.062
0.069
0.105

T
0.057
-7.482-3.2523.088-1.1601.310
1.882

P value
0.955
0.000
0.001
0.002
0.247
0.191
0.061

Model of regression
R
Model
1
0.350

R2
0.122

R2'
0.091

Analysis of Variance TableModel
Sum of Squares
11.052
Regression
79.395Residual
90.447
Total

DF
6
169
175

Mean Square
1.842
0.470

F value
3.921

P value
0.001

Variables
B
Model
Constant-0.835
0.535
year
date
-8.517E-04
latitude8.750E-02
longitude-0.203
body length
2.528E-02
blubber thickness 2.179E-03

SE
0.147
0.153
0.118
0.118
0.053
0.059
0.053

B'

T
-5.681
3.486-0.0070.743-3.8170.428
0.041

P value
0.000
0.001
0.994
0.458
0.000
0.669
0.967

b) 2000-2007

0.307-0.001
0.092-0.3020.031
0.004

Table 18 Results of multiple linear regression analyses with "total Hg levels in muscles ofcommon minke whales from off-Kushiro" as the dependent variable.
a) 2002-2007
Model of regression
R
Model
R2
R2'
1
0.357
0.127
0.059
Analysis of Variance TableModel
Sum of Squares
10.547
Regression
72.419Residual
82.966
Total

DF
6
77
83

Mean Square
1.758
0.941

F value
1.869

P value
0.097

9

Table 18 Results of ANCOVA comparisons of musclar total Hg levels in immature of common minke whales between JARPN (19941999) and JARPN II (2000-2007) from sub-area 7 and sub-areas 8 and 9.
a) sub-are 7 N : 1994-1999 (17 ), 2000-2007 (51 )Test of effects between subjects
Sum of square
DF(Type III)
Modified model
37.5053
Constant
0.175
1Research period
0.930
1
Body length
9.254
1
Error
29.49564Sum67.00068Sum'67.00067

Mean Square

F value

P value

12.502
0.175
0.930
9.254
0.461

27.1260.381
2.018
20.079

0.000
0.539
0.16
0.000

F value

P value

33.551
0.021
12.59652.790

0.000
0.886
0.001
0.000

b) sub-are 8 & 9 N : 1994-1999 (21 ), 2000-2007 (26 )Test of effects between subjects
Sum of squareDF
Mean Square(Type III)
Modified model
31.53
3
10.51
Constant
6.53E-03
1
6.53E-03
Research period
3.946
1
3.946
Body length
16.5371
16.537
Error
13.47
43
0.313
Sum
45.00047
Sum'45.00046

10Noncentral
parameter
81.3790.381
2.018
20.079Observed
Statystical
1.000
0.093
0.288
0.993

Noncentral
parameter
100.653
0.021
12.59652.790Observed
Statystical
1.000
0.052
0.934
1.000

SC/J09/JR23

Hg ppm dry wt

0.100
0.075
0.050
0.025
0.000
1993

1995

1997

1999

2001

2003

2005

2007

2004

2006

2008

2006

2008

Year
Fig. 1 Hg concentration (ppm dry wt) of krill (whole body)Hg ppm wet wt

0.100
0.075
0.050
0.025
0.000
1994

1996

1998

2000

2002

Year
Fig. 2 Hg concentration (ppm wet wt) of Japanese anchovy (mature, wholebody

Hg ppm wet wt

0.100
0.075
0.050
0.025
0.000
1994

1996

1998

2000

2002

Year
Fig. 3 Hg concentration (ppm wet wt) of Pacific saury (whole body)

11

2004

0.5
0.4

0.75

Hg (ppm wet wt.)

Hg (ppm wet wt.)

1.00

0.50
0.25

0.3
0.2
0.1

0.00

0
1993

1998

2003

2008

1995

year
Fig. 4. Hg concentration in muscles of common minke whales (O stock, maturemale) taken from sub-area 7 on western North Pacific.

1997

1999

2001

2003

2005

2007

year
Fig. 5. Hg concentration in muscles of common minke whales (Ostock, mature male) taken from sub-area 8 on western North Pacific.
0.5

1.00
Hg (ppm wet wt.)

Hg (ppm wet wt.)

0.4
0.75
0.50
0.25

1993

1998

2003

0.1

2001

2008

0.1

0.4

0.08
Hg (ppm wet wt.)

0.5

0.3
0.2
0.1

2002

2003

2004

2005

2006

2004

2005

2006

2007

0.06
0.04
0.02

2001

2007

0.1
0.08
0.06
0.04
0.02
0
2002

2003

2004

2005

2006

2002

2003

2004

2005

2006

2007

year
Fig. 9. Hg concentration in muscles of Bryde's whales (mature male)taken from sab-areas 8 and 9 in the western North Pacific.

year
Fig. 8. Hg concentration in muscles of common minke whales (Ostock, mature male) taken from off Sanriku in western North Pacific.

2001

2003

0

0.0
2001

2002

year
Fig. 7. Hg concentration in muscles of common minke whales (Ostock, mature male) taken from off Kushiro on western North Pacific.

year
Fig. 6. Hg concentration in muscles of common minke whales (O stock, maturemale) taken from sub-area 9 on western North Pacific.

Hg (ppm wet wt.)

0.2

0

0.00

Hg (ppm wet wt.)

0.3

2007

2008

year
Fig. 10. Hg concentration in muscles of sei whales (mature male) takenfrom sab-area 9 in the western North Pacific.

12

2008

13

Muscular Hg concentration (ppm wet wt.)

Body length (m)Body length (m)Sub-area 、8, 9○: 2000-2007()●: 1994-1999()

Fig.11 Relationships between muscular Hg concentrations (ppm wet wt. )and body length (m) in common minke whales in
sub-areas 7 and 9 during 1994 and 2007.

Sub-area 7

SC/J09/JR23