SC/J09/JR25

Accumulation features of total and methyl mercury andselenium in tissues of common minke, Bryde’s and sperm
whales from 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 the inter-species difference of sensitivity to mercury toxicity in whales, total mercury (T-Hg), methyl
mercury (MeHg) and selenium (Se) levels in the liver, kidneys and muscle of three whales (common minke whales
Balaenoptera acutorostrata; Bryde’s whales B. edeni; sperm whales Physeter. macrocephalus) were measured. T-Hg
and MeHg were higher in the order of sperm whale > common minke whale > Bryde’s whale, and their Se levels werehigher in the order of sperm whale > Bryde’s whale > common minke whale. The order of the T-Hg and Se levels in
the tissues of the common minke and Bryde’s whales was kidneys > liver > muscle, and that of MeHg was liver >muscle > kidneys. The order of the T-Hg and Se levels in the tissues of sperm whales was liver > kidneys > muscle.
MeHg in the animal body is preferentially distributed in the liver and kidneys containing abundant metal binding
proteins such as metallothioneins. The Se concentrations in the liver of marine mammals are correlated with the total
mercury concentrations. MeHg/T-Hg (%) in the liver and kidneys of sperm whales were higher than those of the baleen
whales in the same total Hg levels, while MeHg/T-Hg (%) vary inversely with T-Hg concentrations in the liver andkidneys of sperm, common minke and Bryde’s whales. Accumulation of high concentrations of inorganic Hg in theliver and kidneys were probably due to a difference of demethylation ability. These results indicate the potential
usefulness of assessment of Hg toxicity in large whales.
KEYWORDS: COMMON MINKE WHALE; BRYDE’S WHALE; SPERM WHALE; NORTH PACIFIC;MERCURY; SELENIUM; BIOACCUMULATIONINTRODUCTION
At the IWC 44th Annual Meeting, the Commission endorsed the plans of the Scientific Committee to pursue studies onenvironmental changes and their impacts on cetaceans (IWC Resolution 1994/13). The second objective of the JARPN
II research plan is “monitoring environmental pollutants in cetaceans and the marine ecosystem” and a part of thisobjective involved examining the “Relationship between chemical pollutants and cetacean health”. Metabolic capacity
to handle organochlorines in cetaceans depends on the species. (Tanabe et al., 1988; Neathery and Miller, 1975). It isessential to clarify the species specific sensitivity of the chemical substances to assess their impact for the wildlife.
Methyl mercury is one of most harmful chemical for cetaceans due to its highly-absorptibity and adverse function inmarine ecosystems. Mercury is mainly released as elemental Hg on land by natural sources, such as volcanic activities
and weathering, and anthropogenic sources, such as thermal power plant and several mining activities. Once released
elemental Hg is transferred to pelagic ocean and so is distributed to pelagic surface water in according to gas-liquidchange. In pelagic ocean, elemental Hg is converted to methyl Hg and it is moderately bioconcentrated in animals ofhigh trophic level such as cetaceans through the food chain. Therefore mercury is one of the most risky chemicals forcetaceans in the ocean.
Mercury was positively associated with selenium (molar ratio 1:1) in cetaceans (Koeman et al., 1973). Mercury isconcentrated in the liver of cetacean and is mostly consisted in inorganic Hg especially among individual contained
higher Hg levels (Pelletier et al., 1985, Itano et al., 1985). It is known that interaction between Hg and Se (Augier et al.,1993), and demethylation of methyl Hg are important detoxification process of MeHg (Wargemann et al., 1997) incetaceans, considering that these would be several processes (Palmisano et al., 1995).
Few studies have examined inter and intra species differences of interaction among methyl Hg, inorganic Hg and Se
with several trophic levels cetaceans, while there are much of the reports related methyl Hg detoxification processes. In
this study, accumulation feature of mercury , toxic element, and selenium , antagonist, are clarified, and inter-species
difference of sensitivity to mercury toxicity are examined. We provide ecotoxicological information related with MeHg
risk for free-ranging whales in the western North Pacific.

1

MATERIALS AND METHODS
Samples and sampling method
Liver, kidneys and muscle tissues from the common minke whales from sub-areas 7 and 9, Bryde’s whales from subarea 7, and sperm whales from sub-area 7 were collected by JARPN II researchers in the 2000 surveys (Fig. 1). Table 1
shows the sample sizes and body length of the whales sampled, by species, sex and sub-area. The tissue samples werefrozen and shipped to the laboratory and stored -20˚C until chemical analysis. In order to understand the pattern ofaccumulation of pollutants in cetaceans, it is essential to consider some biological information from whales. In thisstudy we considered information on the body length and sex of whales. The tissues of all specimens were excised fromthe medial region of body.

Laboratory analysis
The tissue samples were sent to the Miura Institute of Environmental Science (Ehime, Japan) for T-Hg, MeHg and Se
analyses. Tissue samples were digested in microwave (Milestone General: MLS1200mega) using nitric acid in a PTFE
vessel. T-Hg concentrations were determined by cold vapor / atomic absorption spectrometry (Nippon Instruments Co.
RA-2A), Se concentrations were determined by absorption spectrophotometry (Beckman Co., DU-650), and MeHg
concentrations were determined by GC-ECD (Hewlett Packard Co. Ltd., 5890 Series II) according to Westöö method(Westöö, 1968). Concentrations were given on wet weight basis. Accuracy and precision of the methods wereconfirmed using bovine liver (BCR-CRM No. 185).

Statistical analysis
The correlations between chemical and biological parameters were assessed by Spearmann rank test (Zar, 1999). Thesestatistical analyses were executed by SPSS ver.11 for Windows (SPSS Co. Ltd.).
RESULTS AND DISCUSSION
Accumulation status
Tables 2a-c show the concentrations of total Hg, methyl Hg and Se, molar ratio of T-Hg / Se and MeHg / Se andpercentage of MeHg / T-Hg in the liver, kidneys and muscle of minke, Bryde’s and sperm whales from the western
North Pacific. T-Hg and MeHg levels in the liver, kidneys and muscle were higher in the order of sperm whale > minke
whale > Bryde’s whale, and their Se levels were higher in the order of sperm whale > Bryde’s whale > minke whale.
The order of the T-Hg and Se levels in the tissues of the minke and Bryde’s whales was kidneys > liver > muscle, andthat of MeHg was liver > muscle > kidneys. The order of the T-Hg and Se levels in the tissues of sperm whales wasliver > kidneys > muscle. MeHg in the animal body is preferentially distributed in the liver and kidneys containing
abundant metal binding proteins such as metallothionein (Wagemann et al., 1984). The Se concentrations in the liver ofmarine mammals are correlated with the T-Hg concentrations (Koeman et al., 1973). Our results are accordance withprevious studies.

Relationships among T-Hg, MeHg and Se
Plots of relationships MeHg against T-Hg concentrations in liver, kidneys and muscle of minke, Bryde’s and sperm
whales are shown in Fig. 2. The concentrations of MeHg lineally increased with T-Hg in kidneys and muscle. The
inclinations of minke and Bryde’s whales were higher than that of sperm whales in the plot of liver. This indicated thatthe livers of sperm whales contained higher inorganic Hg than those of the other baleen whales.
Plots of relationships Se against T-Hg concentrations in liver, kidneys and muscle of minke, Bryde’s and sperm whales
are shown in Fig. 3. In only liver of sperm whales Se and T-Hg molar ratio is approximately 1:1, while no relation wasobserved in those of the others. Se was strongly induced in the case of higher Hg existence, while concentrations of Se,
one of essential elements, in the tissue and organs were not relatively affected by several varying environments due tohomeostasis. On the other hand, renal Se of sperm whales was clearly induced with MeHg rather than those of liver (Fig.
4). Therefore, Se mainly detoxification inorganic Hg in liver and MeHg in kidneys for sperm whales.

Relationships between T-Hg/MeHg and body length
To examine the relationships between demethylation of MeHg in the organ and growth, plots of MeHg/T-Hg (%)
against body length (m) are shown Fig. 5. Correlation of MeHg/T-Hg (%) and body length were significantly negativein kidneys of male of common mike whales and in liver of male and female of Bryde’s whales (p<0.05). This result is
attributed to difference of biological half-life of inorganic Hg and MeHg in whale body.

2

SC/J09/JR25

Relationships between MeHg/T-Hg and T-Hg
Plots of relationships MeHg/T-Hg (%) against T-Hg concentrations in liver, kidneys and muscle of minke, Bryde’s andsperm whales are shown in Fig. 6. MeHg/T-Hg were clearly decreased with T-Hg concentrations in liver and kidneys of
all whales. And also, these curve is distinguished in each whales. MeHg/THg (%) in the liver and kidneys of sperm
whales were higher than those of the baleen whales in the same total Hg levels, while methyl Hg/total Hg (%) vary
inversely with THg concentrations in the liver and kidneys of sperm, minke and Bryde’s whales. Accumulation of highconcentrations of inorganic Hg in the liver and kidneys were probably due to a difference of demethylation ability.
Considering the biological half-life of Hg (approximately two or three hundred days), if a different accumulation levelof Hg was observed between two groups, this suggests that they ate the different prey species and/or their feeding area
are different.
CONCLUSION
In al the species, lower percentages of MeHg to T-Hg levels and positive correlations between T-Hg and Se wereobserved. Demethylation process and interaction with Se play pivotal role in detoxification Hg in large baleen whales.
The Se concentrations in the liver of marine mammals are correlated with the total mercury concentrations. MeHg/THg (%) in the liver and kidneys of sperm whales were higher than those of the baleen whales in the same total Hg levels,
while MeHg/T-Hg (%) vary inversely with T-Hg concentrations in the liver and kidneys of sperm, minke and Bryde’s
whales. Accumulation of high concentrations of inorganic Hg in the liver and kidneys were probably due to a differenceof demethylation ability. These results indicate the potential usefulness of assessment of Hg toxicity to large whales.
REFERENCES
Augier, H., Benkoel, L., Chamlian, A., Park, W. K. and Ronneau, C. 1993. Mercury, zinc and selenium
bioaccumulation in tissues and organs of Mediterranean striped dolphins Stenella coeruleoalba meyen. Toxicologicalresult of their interaction. Cell. Mol. Biol., 39, 621-634.
International Whaling Commission. 1994. Chairman’s Report of the Forty-Fifth Annual Meeting, Appendix 12.
Resolution on research on the environment and whale stock. Rep. int. Whal. Commn. 44:35.
Itano, K., Kawai, S. and Tatsukawa, R. 1985. Distribution of mercury and selenium in muscle of striped dolphins.
Bulletin of the Japanese Society of Scientific Fisheries, 51, 1129-1131.
Koeman, J. H., Peeters, W. H. M., Koudstaal-Hol, C. H. M., Tjioe, P. S. and de Goeij, J. J. M. 1973. Mercury-selenium
correlations in marine mammals. Nature, 245, 385-386.
Neathery, M.W. Miller, W.J. 1975. Metabolism and toxicity of cadmium, mercury, and lead in animals: a review. J.
Dairy Sci. 58:1767-81.
Palmisano, F., Cardellicchio, N. and Zambonin, P. G. 1995. Speciation of mercury in dolphin liver: A two-stage
mechanism for the demethylation accumulation process and role of selenium. Marine Environmental Research, 40, 109121.
Pelletier, E. 1985. Mercury-selenium interactions in aquatic organisms: a review, Mar. Environ. Res., 18, 111-132.
Tanabe, S., Watanabe, S., Kan, H. and Tatsukawa, R. 1988. Capacity and mode of PCB metabolism in small cetaceans.
Marine Mammal Science 4:103-124.
Wagemann, R., Hunt, R. and Klaverkamp, J.F. 1984. Subcellular distribution of heavy metals in liver and kidney of anurwhal whale (Monodon monoceros): an evaluation for the presence of metallothionein. Comp. Biochem. Physiol.,
78C: 301-307.
Wagemann, R., Trebacz, E., Hunt, R. and Boila, G. 1997. Percent methylmercury and organic mercury in tissues ofmarine mammals and fish using different experimental and calculation methods. Environ. Toxicol. Chem., 16, 18591866.
Westöö. 1968. Determination of methylmercury salts in various kinds of biological material. Determination of
methylmercury compounds in foodstuffs I. Methylmercury compounds in Fish, idnetification and determination. Acta
Chemica Scandinavica 20:2131-2137.
Zar, J. H. 1999. Biostatistical analysis, 4th ed., Prentice Hall, New Jersey, USA, 663pp.

3

Table 1. Details of common minke, Bryde's and sperm whales analyzed.
Species (Academic name )SexArea (n )Body length* (m)common minke whale
males
sub-area 7 (19) 6.66 (4.70-7.82)(Balaenoptera acutorostrata )sub-area 9 (16) 7.31 (4.71-7.75)
females
sub-area 7 (5)7.67 (7.17-8.52)
Bryde's whale
males
sub-area 7 (21) 12.02 (10.28-13.22)(Balaenoptera edeni )females sub-area 7 (22) 12.39 (8.54-14.11)
sperm whale
males
sub-area 7 (3) 10.95 (8.82-12.77)(Physeter macrocephalus )females
sub-area 7 (2) 9.89 (8.17-11.61)*: Nmubers represent average values (ranges) of body length

4

SC/J09/JR25

Table 2a. To tal Hg , methyl Hg and Se levels (mean and range, μg/g wet), ratio of both Hg to Se (mean and range, molar ratio) and percentage of methyl tototal Hg (mean and range, %) in the liver of minke, Bryde's and sperm whales.
Species
Sex
Area (n )total Hg
methyl Hg
Se
tot al Hg/ Se
methyl Hg/Se methyl/total Hg
common minke whal males sub -area 7 (19)
0.48
0.16
1.5
0.13
0.044
34
(0.12-0.80)(0.051-0.40)(0.99-2.2)(0.041-0.25)(0.016-0.12)(9.7-50)
sub -area 9 (16)
0.42
0.12
1.4
0.12
0.034
29
(0.035 -0.75)(0.012-0.26)(0.92-1.7)(0.015-0.20)(0.005-0.080)(17-40)females sub-area 7 (5)
0.52
0.16
1.5
0.14
0.041
30
(0.46-0.60)(0.072-0.20)(1.5-1.6)(0.12-0.16)(0.019-0.054)(16-41)
total
0.46
0.14
1.4
0.13
0.040
31
(0.035 -0.80)(0.012-0.40)(0.92-2.2)(0.015-0.25)(0.005-0.12)(9.7-50)
Bryde's whale
males sub -area 7 (21)
0.16
0.037
1.5
0.040
0.010
28
(0.056 -0.35)(0.022-0.072)(1.1-2.3)(0.017-0.073)(0.006-0.022)(9.5-51)
females sub -area 7 (22)
0.20
0.045
1.6
0.049
0.011
28
(0.020 -0.49)(0.014-0.11)(0.60-3.0)(0.013-0.14)(0.007-0.021)(9.2-72)
total
0.18
0.041
1.5
0.045
0.011
28
(0.020 -0.49)(0.014-0.11)(0.60-3.0)(0.013-0.14)(0.006-0.022)(9.2-72)
sperm whale
males sub-area 7 (3)
25
1.2
11
0.83
0.064
8.3
(4.3-39)(0.69-1.6)(2.3-1 9)(0.72-0.93)(0.033-0.12)(4.0-16)
females sub-area 7 (2)
68
0.80
27
0.77
0.044
7.9
(3.6-130)(0.53-1.1)(2.6-5 2)(0.54-1.0)(0.008-0.081)(0.80-15)
total
42
1.1
18
0.80
0.056
8.1
(3.6-130)(0.53-1.6)(2.3-5 2)(0.54-1.0)(0.008-0.12)(0.80-16)
Table 2b. Total Hg , methyl Hg and Se levels (mean and range, μg/g wet), ratio of both Hg to Se (mean and range, molar ratio) and p ercentage of methyl tototal Hg (mean and range, %) in the kidneys of minke, Bryd e's and sperm whales.
Species
Sex
Area (n )total Hg
methyl Hg
Se
tot al Hg/ Se
methyl Hg/Se methyl/total Hg
common minke whal males sub -area 7 (19)
0.64
0.047
1.6
0.16
0.012
11
(0.068-1.3)(0.019-0.080)(1.0-2.2)(0.017-0.43)(0.005-0.019)(4.1-29)
sub -area 9 (16)
0.67
0.028
1.6
0.17
0.007
5.0
(0.026-1.0)(0.004-0.043)(1.1-2.8)(0.006-0.24)(0.001-0.013)(2.4-14)
females sub-area 7 (5)
0.67
0.048
1.5
0.18
0.013
7.2
(0.61-0.73)(0.037-0.057)(0.97-1.9)(0.13-0.26)(0.009-0.018)(5.6-9.2)
total
0.66
0.040
1.6
0.17
0.010
7.9
(0.026-1.3)(0.004-0.080)(0.97-2.8)(0.006-0.43)(0.001-0.019)(2.4-29)
Bryde's whale
males sub -area 7 (21)
0.23
0.008
2.2
0.040
0.002
5.4
(0.031 -0.41)(0.005-0.013)(1.5-2.9)(0.006-0.087)(0.001-0.002)(2.0-33)
females sub -area 7 (22)
0.24
0.010
2.1
0.044
0.002
5.2
(0.014 -0.60)(0.001-0.019)(1.6-3.5)(0.003-0.10)(0.0002-0.003)(1.9-14)
total
0.23
0.009
2.2
0.042
0.002
5.3
(0.014 -0.60)(0.001-0.019)(1.5-3.5)(0.003-0.10)(0.0002-0.003)(1.9-33)
sperm whale
males sub-area 7 (3)
3.0
0.43
4.0
0.31
0.042
15
(2.2-3.8)(0.29-0.51)(3.0-4.8)(0.21-0.40)(0.037-0.047)(9.4-22)
females sub-area 7 (2)
3.4
0.35
3.6
0.38
0.040
11
(2.7-4.2)(0.33-0.38)(3.1-4.0)(0.34-0.41)(0.032-0.049)(7.7-14)
total
3.2
0.40
3.8
0.34
0.041
13
(2.2-4.2)(0.29-0.51)(3.0-4.8)(0.21-0.41)(0.032-0.049)(7.7-22)
Table 2c. To tal Hg , methyl Hg and Se levels (mean and range, μg/g wet), ratio of both Hg to Se (mean and range, molar ratio) and percentage of methyl tototal Hg (mean and range, %) in the muscle of minke, Bryde's and sperm whales.
Species
Sex
Area (n )total Hg
methyl Hg
Se
tot al Hg/ Se
methyl Hg/Se methyl/total Hg
common minke whal males sub -area 7 (19)
0.20
0.12
0.80(n =14)
0.11(n =14)
0.071(n =14)
61
(0.064 -0.31)(0.045-0.19)(<0.5-1.3)(0 .030->0.18)(0.0 21->0 .12)
(34-84)sub -area 9 (16)
0.15
0.094
0.75(n =12)
0.081(n =12)
0.051(n =12)65
(0.018 -0.19)(0.017-0.12)(<0.5-1.2)(0 .012->0.15) (0.012->0.091)(41-96)females sub-area 7 (5)
0.24
0.15
0.86
0.11
0.073
64
(0.20-0.27)(0.11-0.19)(0.61-1.1)(0.079-0.17)(0.051-0.11)(55-72)
total
0.19
0.12
0.79(n =31)
0.10(n =31)
0.063(n =31)
63
(0.018 -0.31)(0.017-0.19)(<0.5-1.3)(0 .012->0.18)(0.0 12->0 .12)
(34-96)
Bryde's whale
males sub -area 7 (21)
0.052
0.023
0.88(n =18)
0.026(n =18)
0.011(n =18)
44
(0.028 -0.10)(0.011-0.029)(<0.50-2.4)(0.009->0.048) (0.003->0.023)(26-56)females sub -area 7 (22)
0.054
0.027
0.89(n =19)
0.026(n =19)
0.013(n =19)49
(0.004-0.072)(0.001-0.037)(<0.50-2.0)(0.003->0.053) (0.00 04->0 .029)(15-61)
total
0.053
0.025
0.89(n =37)
0.026(n =37)
0.012(n =37)
47
(0.004 -0.10)(0.001-0.037)(<0.50-2.4)(0.003->0.053) (0.00 04->0 .029)(15-61)
sperm whale
males sub-area 7 (3)
1.5
0.76
1.0
0.63
0.32
50
(0.86 -2.1)(0.45-1.1)(0.60-1.6)(0.41-0.93)(0.18-0.49)(44-53)females sub-area 7 (2)
1.4
0.60
0.81
0.68
0.31
46
(0.91 -1.9)(0.50-0.71)(0.57-1.1)(0.63-0.72)(0.27-0.35)(37-55)
total
1.5
0.70
0.94
0.65
0.32
48
(0.86 -2.1)(0.45-1.1)(0.57-1.6)(0.41-0.93)(0.18-0.49)(37-55)5

Table 3 Significant differences between sexes of common minke and Bryde's whales with two-tailed Mann-Whitney test.
nTHg
Common minke whale

26M4F

Bryde's whale

15M16F

Liver
MeHg

Se

THg

*
F>M

Kidneys
MeHg

Se

*
F>M

THg
*
F>M

Muscle
MeHg

Se

**
F>M

*: p<0.05, **: p<0.01, ***: p<0.001

50˚N

45˚

40˚

Subarea-7

Subarea-8

Subarea-9

35˚

140˚

150˚

160˚

170˚E

Figure 1. Subareas surveyed by the 2000 JARPN II cruise. Subareas based on IWC (1994), excluding the EEZ of Russia.

6

SC/J09/JR25

MeHg concentration (μg/g wet wt)

A) Liver1.8
Minke male

1.6

Minke female

1.4

Bride's male
Bride's female

1.2

Sperm male

1

Sperm female

0.8
0.6
0.4
0.2
0
0

10

20
30
40
THg concentration (μg/g wet wt)

5060B) Kidney
0.6
MeHg concentration (μg/g wet wt)

Minke male
Minke female

0.5

Bride's male
Bride's female

0.4

Sperm male
Sperm female

0.3
0.2
0.1
0
0

1

2
3
THg concentration (μg/g wet wt)

45C) Muscle
1.2
MeHg concentration (μg/g wet wt)

Minke male
Minke female

1

Bride's male
Bride's female

0.8

Sperm male
Sperm female

0.6
0.4
0.2
0
0.0

0.5

1.0
1.5
THg concentration (μg/g wet wt)

2.0

2.5

Fig. 2 Relationship between Total Hg and Methyl Hg concentrations in the A) liver, B) kidney and C) muscle ofcommon minke, Bryde's and sperm whales collected from western North Pacific7A) LiverSe concentration (μg/g wet wt)

60
Minke male

1: 1 morlar ratio

Minke female

50

Bride's male
Bride's female

40

Sperm male
Sperm female

30
20
10
0

20

40
60
80
100
THg concentration (μg/g wet wt)

120

140

B) Kidney
Se concentration (μg/g wet wt)

5.0
Minke male

4.5

Minke female

4.0

Bride's male

3.5

Bride's female
Sperm male

3.0

Sperm female

2.5
2.0
1.5
1.0
0.5
0

1

2
3
THg concentration (μg/g wet wt)

45C) Muscle
3.0
Se concentration (μg/g wet wt)

Minke male
Minke female

2.5

Bride's male
Bride's female

2.0

Sperm male
Sperm female

1.5
1.0
0.5
0.000

0.500

1.000
1.500
THg concentration (μg/g wet wt)

2.000

2.500

.
Fig. 3 Relationship between Total Hg and Se concentrations in the A) liver, B) kidney and C) muscle of minke, Bryde's
and sperm whales collected from western North Pacific.

8

SC/J09/JR25

A) Liver60.0
Se concentration (μg/g wet wt)

Minke male
Minke female

50.0

Bride's male
Bride's female

40.0

Sperm male
Sperm female

30.0
20.0
10.0
1.5
0.5
1
MeHg concentration (μg/g wet wt)

02B) Kidney
Se concentration (μg/g wet wt)

5.0
Minke male

4.5

Minke female

4.0

Bride's male

3.5

Bride's female
Sperm male

3.0

Sperm female

2.5
2.0
1.5
1.0
0.5
0

0.1

0.4
0.2
0.3
MeHg concentration (μg/g wet wt)

0.5

0.6

C) Muscle
3.0
Se concentration (μg/g wet wt)

Minke male
Minke female

2.5

Bride's male
Bride's female

2.0

Sperm male
Sperm female

1.5
1.0
0.5
0

0.2

0.4
0.6
0.8
MeHg concentration (μg/g wet wt)

1

1.2

Fig. 4 Relationship between Methyl Hg and Se concentrations in the A) liver, B) kidney C) muscle of common minke,
Bryde's and sperm whales collected from western North Pacific.

9A) Liver
80
Minke male

70

Minke female
Bride's male

MeHg/THg (%)

60

Bride's female
Sperm male

50

Sperm female

40
30
20
10
0
0.000

2.000

4.000

6.000
8.000
10.000Body length (m)12.00014.00016.000B) Kidney
35
Minke male
Minke female

30

Bride's male
Bride's female

Me Hg/THg (%)

25

Sperm male
Sperm female

20
15
10
5
0
0.000

2.000

4.000

6.000
8.000 10.000
Body length (m)12.00014.00016.000C) Muscle
120
Minke male
Minke female

100

Bride's male

MeHg/THg (%)

Bride's female

80

Sperm male
Sperm female

60
40
20
0
0.000

2.000

4.000

6.000
8.000 10.000
Body length (m)12.00014.00016.000Fig. 5 Relationship between body length (m) and MeHg/THg (%) in the A) liver, B) kidney and C) muscle of minke,
Bride's and sperm whales collected from western North Pacific.

10

SC/J09/JR25

A) Liver100
Minke male
Minke female

80

Bryde's male

MeHg/THg (%)

Bryde's female
Sperm male

60

Sperm female

40

20

0
0.0

0.1

1.0
10.0
THg concentration (μg/g wet wt)

100.0B) Kidney
50
Minke male
Minke female

40

Bryde's male

Me Hg/THg (%)

Bryde's female
Sperm male

30

Sperm female

20

10

0
-

1.0

2.0
3.0
THg concentration (μg/g wet wt)

4.0

5.0

C) Muscle
100
Minke male

MeHg/THg (%)

90

Minke female

80

Bride's male

70

Bride's female
Sperm male

60

Sperm female

50
40
30
20
10
0
-

0.5

1.0
1.5
THg concentration (μg/g wet wt)

2.0

2.5

Fig. 6 Relationship between THg concentrations and MeHg/THg (%) in the A) liver, B) C) muscle of common minke,
Bryde's and sperm whales collected from western North Pacific.

11