SC/F16/JR30

Temporal trend of Total Hg levels in three baleen whale
species based on JARPNII data for the period 1994-2014
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 yearly changes of total mercury (Hg) in the western North Pacific, total Hg concentrations inmuscle from common minke whale (Balaenoptera acutorostrata), sei (B. borealis) and Bryde’s (B. edeni)
whales, were measured. Averages and standard deviations of total Hg concentrations in samples of mature
males of O stock of common minke whales from sub-area 7, off Kushiro, off Sanriku, subareas 8 and 9 were0.22±0.05, 0.22±0.05, 0.22±0.06, 0.22±0.06 and 0.24±0.10, ppm wet wt., respectively. And those of sei whales
from sub-area 9 and Bryde’s whales from sub-areas 8 and 9 were 0.044±0.013 and 0.044±0.013 ppm wet wt.,
respectively. Multiple linear regression analysis was carried out and included adjustment for confounders,sampling years, sampling longitude, sampling latitude, sampling date, body length, blubber thickness and main
prey item. Total Hg concentrations in the common minke whales from sub-area 7 were significantly associatedwith deficits in sampling year and main prey item, and those from sub-area 9 were significantly associatedwith deficits in sampling year, latitude and main prey item. Main prey items would have an effect on total Hgconcentrations in the common minke whales from sub-areas 7 and 9. These findings suggest that yearlychanges of total Hg in common minke whales from the western North Pacific could be affected by changes of
their pray items.

KEYWORDS: COMMON MINKE WHALE; SEI WHALE; BRYDE’S WHALE; NORTH PACIFIC;TOTAL MERCURY; MONITORINGINTRODUCTION
Pollutants accumulate through the food chain in the 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 JARPNII, surveys were designed so that quantitative behavior and fate of the pollutants in the marine environment
can be monitored. The present study examines three concentrations and temporal changes of total Hg in three top
predator species (baleen whales) in the western North Pacific. The analysis of this pollutant in both predators and preyspecies is important as the concentration of Hg in predators reflect in part their feeding habits. To understand the patternof accumulation of Hg in whales it is important to consider some biological information such as sex and sexual maturity.
Such information is considered in this study.
In the 2009 review workshop, Yasunaga and Fujise (2009) presented a study on yearly changes of mercury
concentrations in muscle samples of common minke (Balaenoptera acutorostrata), sei (B. borealis) and Bryde’s (B.
edeni) whales and their prey items from the western North Pacific using JARPN and JARPNII samples during 19942007. Yearly changes of total Hg concentrations in zooplankton and pelagic fishes were not observed in the period
1994-2007. Apart from minke whales from sub-area 9, significant yearly changes of concentrations in whales were notobserved. For minke whales in sub-area 9, total Hg concentrations decreased from 1994 to 1999 but increased from2000 to 2007. Results of a multiple linear regression analysis suggested that changes of Hg concentrations in sub-area 9
reflect changes in food habitats of minke whale rather than changes in accumulation concentrations in the environment.
This study examines concentrations and temporal changes of Hg concentrations in mature males of three baleen whale
species. Body length, blubber thickness, stomach content and sexual maturity information obtained during JARPN and
JARPNII surveys is considered to assist in the interpretation of factors affecting total Hg concentrations.

1

MATERIALS AND METHODS
Samples
Muscle tissues from the minke whales (Okhotsk Sea-West Pacific stock) from sub-area 7, off Kushiro, off Sanriku,
subareas 8 and 9, sei whales from sub-area 9 and Bryde’s whales from sub-areas 8 and 9 were collected by JARPNII
researchers in the surveys conducted in the period from 1994 to 2014 (Fig. 1). Biological data such as body length andblubber thickness and tissue samples were collected on board the Nisshin Maru (Table 1). The muscle tissues were
excised from the medial region part of the body, frozen and shipped to the laboratory and stored at -20˚C until chemical
analysis. The forestomach contents have proved sufficient for determination of the common minke whale diet in the
Northeast Atlantic (Lindstrøm et al., 1997). The prey composition between forestomach and fundus were very similar inthis study. Therefore, this study was based on contents from forestomach.
Tables 3 and 4 show the sample sizes, maturity stage and body length of male animals, by species, sub-area and survey.
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 (Bando et al., unpublished data). Only minke whales from the Okhotsk Sea-West
Pacific stock (O-stock) as identified by the microsatellite analysis (Kanda et al., 2009), were used.

Laboratory analysis
The muscle samples were stripped externally to avoid contamination. For total Hg analysis, the samples were set on aceramic boat and were subjected to cold-vapor atomic absorption spectrometry with heat-vaporization, gold
amalgamation method (Nippon Instruments Co., MA-3000). Triplicate analysis was performed on each sample, toincrease the accuracy of the determination. Accuracy and precision of the methods were confirmed using standard
materials, DORM-3 (NRCC, muscle of dogfish).
Total Hg concentrations in prey items in SC/J09/JR23 of the 2007 JARPNII review (Yasunaga and Fujsie, 2007), wereused because most of the samples for this study until 2011 were lost after the 2011 earthquake and tsunami (see IWC,
2012).

Statistical analysis
The yearly changes of total Hg concentrations in whales were assessed by multiple linear regression in the context ofother factors (R Development Core Team, 2006). The following independent variables: “sampling year”, “samplingdate”, “sampling latitude”, “sampling longitude”, “body length”, “blubber thickness” and “main prey item” wereallowed, and all parameters except for main prey item were logarithmic transformed. Categorical parameters of main
prey items used in the analyses were the following: sub-area 7 of minke whale (Japanese anchovy: Engraulis japonicus,
Euphausiids, Japanese flying squid: Todarodes pacificus, mackerel: Scomber japonicus, Japanese sardine: Sardinops
melanostictus, Pacific saury: Cololabis saira and Walleye Pollock: Theragra chalcogramma); off Kushiro and off
Sanriku of common minke whale (None); sub-area 8 of minke whale (anchovy, Copepods, Euphausiids, Japanese flying
squid, mackerel and Pacific saury); sub-area 9 of minke whale (anchovy, Atka mackerel: Pleurogrammus
monopterygius, Copepods, Euphausiids, mackerel, armhook squid: Berryteuthis anonychus, oceanic lightfish:
Vinciguerria nimbaria, Pacific pomfret: Brama japonica, Salomonids, Pacific saury); sub-area 9 of sei whale (Japanese
anchovy, Copepods, Euphausiids, mackerel, armhook squid, Japanese sardine and Pacific saury); sub-areas 8 and 9 of
Bryde’s whale (Japanese anchovy, Euphausiids and mackerel). A p value of less than 0.05 was considered to indicate
statistical significance in all tests. The statistical analyses were performed using the free software R, version 3.2.0.

RESULTS
Tables 1-3 show the total Hg concentrations in minke, sei and Bryde’s whales, respectively. Averages and standard
deviations of total Hg concentrations in muscle samples of mature males of O stock-minke whales from sub-area 7, off
Kushiro, off Sanriku, subareas 8 and 9, sei whales from sub-area 9 were 0.22±0.05, 0.22±0.05, 0.22±0.06 and 0.22±0.06,
0.24±0.10, ppm wet wt., respectively. And those of sei whales from sub-area 9 and Bryde’s whales from sub-areas 8
and 9 were 0.044±0.013 and 0.044±0.013 ppm wet wt., respectively. Plots of total Hg concentrations against theirsampling year are shown for common minke (Figs. 2a-2e for different sub-areas), sei (Fig. 2f) and Bryde’s (Fig. 2g)
whales during 1994 and 2014.
To examine the factors affecting total Hg concentrations in minke, sei and Bryde’s whales, multiple linear regression
analyses were conducted. The results for minke whales in sub-area 7, off Kushiro, off Sanriku, subareas 8 and 9, sei
whales in sub-area 9 and Bryde’s whales in sub-areas 8 and 9 are shown in Tables 4, 5, 6, 7, 8, 9 and 10, respectively.
Regression models were significant for all cases. In minke whales from sub-areas 7 and 9, and sei whales from sub-area
9, total Hg concentrations were significantly associated with sampling year (Tables 4, 6 and 9).
2

SC/F16/JR30

DISCUSSIONIn sub-area 7, total Hg concentrations in minke whales (period 1996-2012), a significant association was found foryear (+) and main prey items (Table 4). Total Hg concentrations in muscle of minke whale observed from eachmain prey item in stomach and total Hg concentrations in whole body of the prey items from the same areas areshown in Table 11. Total Hg concentrations in minke whales having mackerel in stomach were the highest andthose having sardine in stomach were the lowest among minke whales from sub-area 7, whereas those for otherprey items had similar concentrations. The number of minke whales having mackerel and sardine in their stomach
were only one and two whales, respectively. These results indicate that total Hg concentrations of minke whales
from sub-area 7 may be less affected by total Hg in the food items.
In sub-area 9, total Hg concentrations in minke whales (period 1996-2012), significant association was found foryear (-), latitude (+) and main pray items (Table 6). Total Hg concentrations in muscle of minke whale for eachmain prey item in stomach and total Hg concentrations in the prey items from sub-area 9 are shown in Table 12.
Total Hg concentrations in minke whales having Pacific pomfret in stomach were the highest among minke
whales from sub-area 9, and total Hg concentrations in Pacific pomfret were one or two orders of magnitude
higher than those in the other prey items. Also total Hg concentrations in minke whales having zooplankton suchas copepods and euphausiids were lower than the others. Total Hg concentrations in the zooplankton were one or
two orders of magnitude lower than those in the other prey items. Furthermore, yearly changes were observed infood items of the minke whales in the same period (Konishi et al., 2016). These results indicate that changes of Hg
concentrations in sub-area 9 reflect changes in food habitat of minke whale rather than changes of background levels of
total Hg in the marine environment.
In sub-area 9, total Hg concentrations in sei whales (period 2002-2014), a significant association was found for year(-), body length (+) and main prey items (Table 9). Total Hg concentrations in muscle of each sei whale having
the same main prey items in stomach and total Hg concentrations in the prey items from the same areas arecompared in Table 13. Total Hg concentrations in minke whales having anchovy and sardine in stomach wereslightly higher than the other two whale species from sub-area 9. These results indicate that Total Hgconcentrations of sei whales from sub-area 9 may be less affected by Total Hg in the food items.
The Hg concentrations observed in muscle of minke whales in off Kushiro and off Sanriku, sub-area 8 and Bryde’s
whales in sub-areas 8 and 9 were relatively stable in the western North Pacific during the research periods. On the other
hand, yearly changes of total Hg in muscle of minke whales from sub-areas 7 and 9, and sei whales from sub-area 9
were observed in order to change of their food items. Total Hg concentrations in surface water of the North Pacific havenot changed since the 1980’s (Laurier et al., 2004; Sunderland et al., 2010). Consequently, yearly trend of total Hg insea surface water and the baleen whales from the North Pacific remained stable for the research period, whileanthropogenic Hg emission in Asia have risen steadily over the past several decades (UNEP, 2013).

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.
International Whaling Commission. 2012. Report of the Scientific Committee. Annex P1. Effect of the March 11thearthquake and tsunami on JARPAII/JARPNII data and samples. J. Cetacean Res. Manage. (Suppl.) 13:308-9.
Kanda et al. 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 JARPNII Review Workshop, Tokyo, January 2009
(unpublished). 9pp.
Laurier, F., Mason, R.P., Gill, G. and Whalin, L. 2004. Mercury distribution in the North Pacific Ocean: 20 years ofobservations. Mar. Chem. 90:3-19.
Lindstrøm, U., Haug, T. and Nilssen, K.T. 1997. Diet studies based on contents from two separate stomach content
compartments of northeast Atlantic common minke whales Balaenoptera acutorostrata. Sarsia 82:63-68.
Ministry of Health, Labour and Welfare. 2005. Survey results of mercury levels in fisheries.
http://www.mhlw.go.jp/topics/bukyoku/iyaku/syoku-anzen/suigin/dl/050812-105.pdf#search='%E9%AD%9A%E4%BB%8B%E9%A1%9E%E3%81%AB%E5%90%AB%E3%81%BE%E3%8
2%8C%E3%82%8B%E6%B0%B4%E9%8A%80%E3%81%AE%E8%AA%BF%E6%9F%BB%E7%B5%90%E6%9E%9C%EF%BC%88%E3%81%BE%E3%81%A8%E3%82%81%EF%BC%89'

3

R Development Core Team 2006. R: A language and environment for statistical computing. R Foundation for StatisticalComputing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org.
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.
Sunderland, E.M., Krabbenhoft, D.P., Moreau, J.W., Strode, S.A. and Landing, W.M. 2009. Mercury sources,
distribution, and bioavailability in the North Pacific Ocean: Insights from data and models. Global Biogeochem.
Cycles 23:GB2010.
UNEP. 2013. Global Mercury Assessment 2013: Sources, emissions, releases, and environmental transport. Pp42.
http://www.unep.org/publications/contents/pub_details_search.asp?ID=6282
Yasunaga, G. and Fujise, Y. 2009. Temporal trends and factors affecting mercury levels in common minke, Bryde’s andsei whales and their prey species in the western North Pacific. Paper SC/J09/JR23 presented to the JARPNII
Review Workshop, Tokyo, January 2009 (unpublished). 14pp.

4

SC/F16/JR30
Table 1. Biological data and total mercury concentrations in muscle of common minke whales (males) from western
North Pacific during 1994 and 2014
subarea
7

year

1996
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2009
2011
2012
total
Kushiro
2002
2004
2005
2006
2007
2008
2009
2010
2011spring
2011autumn
2012
2013
2014
total
Sanriku
2003
2005
2006
2007
2008
2009
2010
2012
2013
2014
total

maturitynmaturematurematurematurematurematurematurematurematurematurematurematurematuremature

18
35
31
6
27
33
11
6
17
16
41
11
23
19
294
14
23
25
10
14
5
6
3
4
10
5
23
10
152
8
3
6
10
3
1
5
2
2
2
42

maturematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematurematuremature

(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(

body length(m)7.36 ± 0.28
7.50 ± 0.27
7.41 ± 0.29
7.30 ± 0.25
7.45 ± 0.31
7.52 ± 0.27
7.42 ± 0.40
7.56 ± 0.21
7.51 ± 0.23
7.39 ± 0.39
7.47 ± 0.26
7.71 ± 0.26
7.47 ± 0.34
7.37 ± 0.34
7.46 ± 0.30
7.22 ± 0.34
7.43 ± 0.24
7.44 ± 0.32
7.52 ± 0.29
7.33 ± 0.59
7.26 ± 0.21
7.54 ± 0.37
7.49 ± 0.21
7.40 ± 0.41
7.26 ± 0.37
7.48 ± 0.21
7.33 ± 0.35
7.33 ± 0.28
7.38 ± 0.35
7.10 ± 0.35
7.27 ± 0.13
7.24 ± 0.32
7.50 ± 0.30
7.49 ± 0.32
6.85 ±
7.32 ± 0.24
7.31 ±
7.52 ±
7.38 ± 0.39
7.32 ± 0.32

blubber thickness(cm)） (3.1 ± 0.4） (） (2.6 ± 0.4） (） (3.6 ± 0.8） (） (3.6 ± 1.0） (） (2.4 ± 0.5） (） (3.7 ± 0.8） (） (2.4 ± 0.5） (） (4.1 ± 0.6
） (） (3.3 ± 0.9） (） (2.4 ± 0.7
） (） (3.0 ± 0.7） (） (3.2 ± 0.7） (） (3.5 ± 0.6） (） (2.6 ± 0.4） (） (3.1 ± 0.8） (） (4.3 ± 1.0
） (） (4.2 ± 0.6） (） (3.5 ± 0.6） (） (4.4 ± 0.8） (） (4.1 ± 0.8） (） (4.3 ± 1.0
） (） (4.3 ± 0.4） (） (3.8 ± 0.4） (） (3.2 ± 0.6） (） (4.4 ± 1.0） (） (5.0 ± 0.7） (） (5.0 ± 0.9） (） (5.0 ± 0.8） (） (4.3 ± 0.9） (） (2.9 ± 0.5） (） (2.5 ± 0.3） (） (2.8 ± 0.2） (） (2.5 ± 0.4） (） (3.2 ± 0.3
） (
） (
2.8 ±
） (
） (
3.1 ± 0.6
） (
） (
3.4 ±
） (
） (
3.5 ±
） (
） (
2.7 ± 0.3
） (
(
2.8
±
0.5
）
） (

5

muscular Hg(ppm wet wt.)
0.23 ± 0.05
0.20 ± 0.05
0.20 ± 0.04
0.24 ± 0.04
0.21 ± 0.04
0.22 ± 0.03
0.20 ± 0.07
0.22 ± 0.02
0.27 ± 0.04
0.22 ± 0.05
0.23 ± 0.04
0.21 ± 0.06
0.25 ± 0.05
0.24 ± 0.08
0.22 ± 0.05
0.21 ± 0.06
0.20 ± 0.03
0.25 ± 0.05
0.22 ± 0.03
0.23 ± 0.06
0.25 ± 0.01
0.21 ± 0.07
0.23 ± 0.02
0.24 ± 0.03
0.23 ± 0.02
0.21 ± 0.06
0.19 ± 0.04
0.21 ± 0.09
0.22 ± 0.05
0.18 ± 0.04
0.29 ± 0.02
0.19 ± 0.05
0.25 ± 0.08
0.19 ± 0.03
0.21 ±
0.20 ± 0.05
0.18 ±
0.30 ±
0.31 ± 0.04
0.22 ± 0.06

）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）

Table 1. Continued
subareayear

maturity

n

8

1996
1997
1998
2001
2002
2003
2005
2006
2007
2008
2009
total
1994
1995
1997
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2013
total

maturematurematurematurematurematurematurematurematurematuremature

11
26
28
13
5
27
2
24
10
3
6
155
16
68
39
12
19
21
28
50
25
16
4
36
5
9
3
351

9

maturematurematurematurematurematurematurematurematurematurematurematurematurematuremature

(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(

body length(m)7.44 ± 0.33
7.44 ± 0.36
7.54 ± 0.25
7.78 ± 0.34
7.71 ± 0.21
7.50 ± 0.24
7.54 ±
7.51 ± 0.26
7.55 ± 0.26
7.52 ± 0.05
7.23 ± 0.34
7.52 ± 0.30
7.42 ± 0.27
7.45 ± 0.31
7.41 ± 0.32
7.51 ± 0.23
7.69 ± 0.29
7.55 ± 0.21
7.50 ± 0.32
7.47 ± 0.21
7.49 ± 0.29
7.56 ± 0.30
7.56 ± 0.20
7.45 ± 0.26
7.41 ± 0.41
7.66 ± 0.23
7.59 ± 0.22
7.49 ± 0.28

blubber thickness
(cm)
） (
） (
2.6 ± 0.5） (） (3.5 ± 0.6） (） (2.6 ± 0.4） (） (2.3 ± 0.4） (） (3.2 ± 0.6） (） (2.4 ± 0.4
） (
） (
2.2 ±
） (
） (
2.9 ± 0.6） (） (2.3 ± 0.4） (） (2.7 ± 0.4） (） (3.2 ± 0.6） (） (2.8 ± 0.6） (） (3.5 ± 0.7） (） (3.1 ± 0.5） (） (3.1 ± 0.5） (） (2.6 ± 0.5） (） (2.5 ± 0.4） (2.9 ± 0.6
） (
） (
） (
2.9 ± 0.6） (） (3.9 ± 0.7） (） (3.5 ± 0.6） (） (3.4 ± 0.6
） (） (2.2 ± 0.3） (） (3.1 ± 0.7
） (） (3.0 ± 0.8） (） (3.2 ± 0.5） (） (4.0 ± 1.3
3.2 ± 0.7
） (
） (

6

muscular Hg(ppm wet wt.)
0.25 ± 0.04
0.27 ± 0.06
0.23 ± 0.05
0.21 ± 0.05
0.20 ± 0.11
0.18 ± 0.06
0.16 ±
0.21 ± 0.05
0.22 ± 0.06
0.23 ± 0.02
0.20 ± 0.06
0.22 ± 0.06
0.36 ± 0.16
0.27 ± 0.06
0.25 ± 0.11
0.16 ± 0.03
0.19 ± 0.05
0.20 ± 0.05
0.18 ± 0.05
0.20 ± 0.07
0.17 ± 0.05
0.28 ± 0.08
0.18 ± 0.09
0.30 ± 0.15
0.19 ± 0.06
0.22 ± 0.03
0.19 ± 0.06
0.24 ± 0.10

）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）
）

SC/F16/JR30
Table 2. Biological data and mercury concentrations in muscle of sei whales (males) from western North Pacific during
2002 and 2014
subareayear

matuarity

n

9

2002
2003
2004
2005
2006
2007
2011
2012
2013
2014
2002-2014

maturematurematurematurematurematurematurematurematurematuremature

5
5
5
5
5
5
15
21
26
21
113

total

(
(
(
(
(
(
(
(
(
(
(

body length(m)
13.60 ± 0.16
13.80 ± 0.43
13.61 ± 0.04
13.54 ± 0.38
13.84 ± 0.51
13.92 ± 0.08
13.82 ± 0.42
13.74 ± 0.45
13.76 ± 0.50
13.80 ± 0.36
13.76 ± 0.41

blubber thickness
(cm)
） (
） (
4.7 ± 0.5） (） (4.7 ± 0.7） (4.1 ± 0.6
） (
） (
） (
4.8 ± 0.6） (） (4.9 ± 0.6） (） (5.8 ± 0.7） (） (4.8 ± 0.8） (5.0 ± 0.5
） (
） (
） (
5.6 ± 0.8） (） (4.8 ± 0.5） (） (5.0 ± 0.8

musclar Hg(ppm wet wt.)
0.050 ± 0.012
0.057 ± 0.007
0.050 ± 0.009
0.049 ± 0.011
0.052 ± 0.006
0.058 ± 0.010
0.039 ± 0.009
0.030 ± 0.011
0.040 ± 0.009
0.053 ± 0.009
0.044 ± 0.013

）
）
）
）
）
）
）
）
）
）
）

Table 3. Biological data and mercury concentrations in muscle of Bryde's whales (males) from western North Pacificduring 2002 and 2014
subareayear

matuarity

n

8, 9

2002
2004
2006
2007
2011
2012
2013
2002-2013

maturematurematurematurematurematurematuremature

5
5
5
5
3
6
9
38

total

(
(
(
(
(
(
(
(

body length(m)
12.67 ± 0.43
12.59 ± 0.36
12.36 ± 0.47
12.63 ± 0.35
12.31 ± 0.27
12.85 ± 0.48
12.79 ± 0.38
12.64 ± 0.41

blubber thickness
(cm)
） (
） (
4.5 ± 0.6） (） (4.4 ± 0.7） (） (4.5 ± 0.5） (） (3.9 ± 0.7） (） (3.6 ± 0.5） (） (4.8 ± 1.0
） (） (4.7 ± 0.8） (） (4.4 ± 0.8

Table 4. Results of multiple linear regression analysis with "total Hg levels in muscle of common minke
whales from subarea 7" as the dependent variable.
a) Model of regression
1

R2
0.981

R2 '
0.980

b) Analysis of Variance Table
Model
Regression
Residual

DF
274
274

SE
0.221

B
25.722-0.0920.072-0.078-0.0480.037-196.550-196.477-196.483-196.176-196.835-196.460-196.428

SE
6.801
0.220
0.061
0.529
0.427
0.042
52.93452.92952.92252.94652.95152.92152.934Model

F value1068

P value<0.001

T
3.78
-0.42
1.19
-0.15
-0.11
0.88
-3.71
-3.71
-3.71
-3.71
-3.72
-3.71
-3.71

P value<0.001
0.676
0.236
0.884
0.911
0.378
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

c) Variables
Model
Year
Body length
Blubber thickness
longitude
latitude
Date
MainPrey_Anchovy
MainPrey_Euphausiids
MainPrey_JFSquid
MainPrey_Mackerel
MainPrey_Sardine
MainPrey_Saury
MainPrey_WalleyePollock

7

musclar Hg(ppm wet wt.)
0.051 ± 0.008
0.045 ± 0.008
0.040 ± 0.011
0.049 ± 0.008
0.022 ± 0.005
0.046 ± 0.019
0.047 ± 0.010
0.044 ± 0.013

）
）
）
）
）
）
）
）

Table 5. Results of multiple linear regression analysis with "total Hg levels in muscle of common minke
whales from off Kushiro" as the dependent variable.
a) Model of regression
1

R2
0.975

R2 '
0.974

b) Analysis of Variance Table
Model
Regression
Residual

DF
146
146

SE
0.255

B
2.989
0.874
-0.3680.932-5.895
0.136

SE
7.420
0.427
0.096
8.143
12.355
0.216

Model

F value
950.7

P value<0.001

T
0.40
2.05
-3.82
0.11
-0.48
0.63

P value
0.688<0.05<0.001
0.909
0.634
0.532

c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date

Table 6. Results of multiple linear regression analysis with "total Hg levels in muscle of common minke
whales from off Sanriku" as the dependent variable.
a) Model of regression
1

R2
0.975

R2 '
0.971

b) Analysis of Variance Table
Model
Regression
Residual

DF
36
36

SE
0.269

B
24.639-0.031-0.46122.444-54.886
1.111

SE
32.7540.028
0.280
18.75857.835
0.475

Model

F value
233.7

P value<0.001

T
0.75
-1.12
-1.65
1.20
-0.95
2.34

P value
0.457
0.272
0.109
0.239
0.349
<0.05

c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date

Table 7. Results of multiple linear regression analysis with "total Hg levels in muscle of common minke
whales from subarea 8" as the dependent variable.
a) Model of regression
1

R2
0.968

R2 '
0.965

b) Analysis of Variance Table
Model
Regression
Residual

DF
140
140

SE
0.298

B
-23.423
0.911
0.358
0.253
-6.367-0.066205.475
205.482
205.412205.444205.822205.660

SE
14.788
0.623
0.122
1.389
2.648
0.523
107.118
107.134
107.133
107.134
107.145
107.109

Model

F value
348.7

P value<0.001

T
-1.58
1.46
2.94
0.18
-2.41
-0.13
1.92
1.92
1.92
1.92
1.92
1.92

P value
0.115
0.146
<0.01
0.856
<0.05
0.900
0.057
0.057
0.057
0.057
0.057
0.057

c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date
MainPrey_Anchovy
MainPrey_Copepods
MainPrey_Euphausiids
MainPrey_JFSquid
MainPrey_Mackerel
MainPrey_Saury

8SC/F16/JR30
Table 8. Results of multiple linear regression analysis with "total Hg levels in muscle of common minke
whales from subarea 9" as the dependent variable.
a) Model of regression
1

R2
0.956

R2 '
0.954

b) Analysis of Variance Table
Model
Regression
Residual

DF
331
331

SE
0.338

B
-38.440
0.419
0.168
2.349
-0.122-1.485284.248283.767
284.147
284.118
284.285283.987
283.768
284.941284.422284.391

SE
7.845
0.492
0.089
0.666
0.947
0.291
59.44059.45559.46759.44459.48059.45459.47759.45459.42359.446Model

F value
446.2

P value<0.001

T
-4.90
0.85
1.88
3.53
-0.13
-5.10
4.78
4.77
4.78
4.78
4.78
4.78
4.77
4.79
4.79
4.78

P value<0.001
0.395
0.061<0.001
0.897<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date
MainPrey_Anchovy
MainPrey_AtkaMackerel
MainPrey_Copepods
MainPrey_Euphausiids
MainPrey_Mackerel
MainPrey_Min.arm squid
MainPrey_OceanicLightfish
MainPrey_PacificPomfret
MainPrey_Salmonids
MainPrey_Saury

Table 9. Results of multiple linear regression analysis with "total Hg levels in muscle of sei whales fromsubarea 9" as the dependent variable.
a) Model of regression
1

R2
0.991

R2 '
0.989

b) Analysis of Variance Table
Model
Regression
Residual

DF
76
76

SE
0.330

B
-58.878
2.777
0.046
0.394
-2.826-0.452451.250451.053450.978451.224451.305451.469
451.034SE
23.932
1.298
0.263
1.183
1.626
0.542
182.421182.466
182.411
182.484
182.482
182.478
182.468

Model

F value
640

P value<0.001

T
-2.46
2.14
0.18
0.33
-1.74
-0.83
2.47
2.47
2.47
2.47
2.47
2.47
2.47

P value
<0.05
<0.05
0.861
0.740
0.086
0.407
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05

c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date
MainPrey_Anchovy
MainPrey_Copepods
MainPrey_Euphausiids
MainPrey_Mackerel
MainPrey_Min.arm squid
MainPrey_Sardine
MainPrey_Saury

9

Table 10. Results of multiple linear regression analysis with "total Hg levels in muscle of Bryde's
whales from subareas 8 and 9" as the dependent variable.
a) Model of regression
1

R2
0.996

R2 '
0.994

b) Analysis of Variance Table
Model
Regression
Residual

DF
20
20

SE
0.236

B
-51.096
3.656
0.299-2.9786.070
1.030
353.841353.823353.812SE
32.449
1.698
0.307
1.708
4.352
0.642
237.095
237.142237.076Model

F value
556.8

P value<0.001

T
-1.58
2.15
0.97
-1.74
1.40
1.60
1.49
1.49
1.49

P value
0.131
<0.05
0.342
0.097
0.178
0.124
0.151
0.151
0.151

c) Variables
Model
Year
Body length
Blubber thickness
latitudelongitude
Date
MainPrey_Anchovy
MainPrey_Euphausiids
MainPrey_Mackerel

10Euphausiids

JFSquid

M ackerel

SardineSaury
26

0.23 ± 0.043 ) (
28

41*

2*

)

0.24 ± 0.056 )WalleyePollock) ( 0.038 ± 0.015 ) ( 0.045 ±)(Atka M ackerel

Copepods

Euphausiids

M ackerel

M AFSquid

11

Euphausiids

M ackerel

11
48
9
9
n
whole of prey spp. Ave.±SD ( 0.037 ± 0.025 ) ( 0.005 ± 0.003 ) ( 0.005 ± 0.003 ) ( 0.020 ± 0.002 ) (
5*
20*
5*
19*
n
*: Yasunaga and Fujise (2009); **: Ministry of Health, Labour and Welfare (2005)

Muscle of whales

Copepods

M in.arm squid

Sardine366**) ( 0.018 ±2

Ave.±SD ( 0.049 ± 0.013 ) ( 0.043 ± 0.014 ) ( 0.045 ± 0.016 ) ( 0.045 ± 0.016 ) ( 0.040 ± 0.005 ) ( 0.052 ±Anchovy41*) ( 0.038 ± 0.015 )7) ( 0.041 ± 0.015 )Saury

Table 13. Comparison between muscular Hg levels in sei whales per main prey items observed from subarea 9 and the whole body Hg levelsin the prey items from the western North Pacific)()(

Oceanic Lightfish) ( 0.17 ± 0.07 ) ( 0.18 ± 0.09 ) ( 0.19 ± 0.04 ) ( 0.19 ± 0.12 ) ( 0.11 ±Muscle of whales Ave.±SD ( 0.22 ± 0.10 ) ( 0.13 ±
83
1
6
15
3
5
1
n
±
)(
±
) ( 0.005 ± 0.003 ) ( 0.005 ± 0.003 ) ( 0.020 ± 0.002 ) (whole of prey spp. Ave.±SD ( 0.037 ± 0.025 ) ( 0.086 ±
61**
20*
5*
19*
5*
n
*: Yasunaga and Fujise (2009); **: Ministry of Health, Labour and Welfare (2005)

Anchovy3*

0.23 ±

6)(

Salmonids
50.32 ± 0.08

41**

0.03 ) ( 0.027 ±0.44 ± 0.26

Pacific Pomfret

Saury
257

0.24 ± 0.09)

41*

) ( 0.038 ± 0.015 ))(Table 12. Comparison between muscular Hg levels in common minke whales per main prey items observed from subarea 9 and the whole body Hg levels in the prey items from the western
North Pacific) ( 0.17 ±Muscle of whales Ave.±SD ( 0.21 ± 0.051 ) ( 0.22 ± 0.049 ) ( 0.22 ± 0.03 ) ( 0.33 ±
238
33
8
1
2
n
) ( 0.020 ± 0.002 ) ( 0.018 ±whole of prey spp. Ave.±SD ( 0.037 ± 0.025 ) ( 0.005 ± 0.003 ) ( 0.058 ±
57**
66**
20*
19*
5*
n
*: Yasunaga and Fujise (2009); **: Ministry of Health, Labour and Welfare (2005)

Anchovy

Table 11. Comparison between muscular Hg levels in common minke whales per main prey items observed from subarea 7 and the wholebody Hg levels in the prey items from the western North Pacific

SC/F16/JR30

Off Kushiro

Off Sanriku

Figure 1. Sub-areas surveyed by the JARPNII research. Sub-areas based on IWC (1994), excluding the EEZ of Russia
Hg concentrations in muscle (ppm wet)mature male of common minke whale, sub-area 7
0.50
0.40
0.30
0.20
0.10
0.00

1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014
year

Figure 2a. Yearly change of Total Hg concentrations in muscle of common minke whales (mature males, O-stock) in
sub-area 7 during the period 1996-2012

Hg concentrations in muscle (ppm wet)mature male of common minke whale, Kushiro
0.50
0.40
0.30
0.20
0.10
0.00

2002

2004

2006

2008
year

2010

2012

2014

Figure 2b. Yearly change of Total Hg concentrations in muscle of common minke whales (mature males, O-stock) in
off Kushiro during the period 2002-2014

12

SC/F16/JR30

Hg concentrations in muscle (ppm wet)mature male of common minke whale, Sanriku
0.50
0.40
0.30
0.20
0.10
0.00

2002

2004

2006

2008
year

2010

2012

2014

Figure 2c. Yearly change of Total Hg concentrations in muscle of common minke whales (mature males, O-stock) in
off Sanriku during the period 2002-2014

Hg concentrations in muscle (ppm wet)mature male of common minke whale, sub-area 8
0.50
0.40
0.30
0.20
0.10
0.00

1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014
year

Figure 2d. Yearly change of Total Hg concentrations in muscle of common minke whales (mature males, O-stock) in
sub-area 8 during the period 1996-2009

Hg concentrations in muscle (ppm wet)mature male of common minke whale, sub-area 9
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00

1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014
year

Figure 2e. Yearly change of Total Hg concentrations in muscle of common minke whales (mature males, O-stock) in
sub-area 9 during the period 1994-201313

Hg concentrations in muscle (ppm wet)mature male of sei whale, sub-area 9
0.20
0.15
0.10
0.05
0.00

2002

2004

2006

2008
year

2010

2012

2014

Figure 2f. Yearly change of Total Hg concentrations in muscle of sei whales (mature males) in sub-area 9 during theperiod 2002-2014

Hg concentrations in muscle (ppm wet)mature male of Bryde's whale, sub-area 8, 9
0.20
0.15
0.10
0.05
0.00

2002

2004

2006

2008
year

2010

2012

2014

Figure 2g. Yearly change of Total Hg concentrations in muscle of Bryde’s whales (mature males) in sub-areas 8 and 9
during the period 2002-201314