SC/F16/JR46

Genetic analyses based on mtDNA control region sequencing
and microsatellite DNA confirmed the occurrence of a single
stock of sei whales in oceanic regions of the North Pacific
Luis A. Pastene1, Mutsuo Goto1 Mioko Taguchi2 and Toshihide Kitakado3
1

Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan
Okitsunaka-cho 1347-3-302, Shimizu-ku, Shizuoka-shi, Shizuoka 424-0204, Japan
3
Tokyo University of Marine Science and Technology, 1-5-7 Konan, Minato-ku, Tokyo 108-0075, Japan
2

ABSTRACT
A total of 1,554 sei whales were examined genetically (mtDNA control region sequencing, 487bp andmicrosatellite DNA at 17 loci) to investigate population genetic structure of this species in the North
Pacific. Samples were available from different sources, JARPNII (catches) (2002-2014), POWER(biopsy) (2010-2012) and past commercial (catches) (1972-73). For the heterogeneity test two
longitudinal sectors were defined in the North Pacific: Western and Eastern at 180°, which covered thisocean basin widely from approximately 145°E to 135°W. No significant spatial genetic heterogeneity was
found by the two genetic markers. A phylogenetic tree of 82 mtDNA haplotypes showed several clusters,
but none was supported by high bootstrap values. Whales from both Western and Eastern sectors were
widely distributed through the clusters. Taken as a whole, the genetic information in this study is
consistent with the view that the oceanic regions of the North Pacific is occupied by a single stock of sei
whale.
INTRODUCTION
The most comprehensive studies conducted so far with regard to the stock structure of the North Pacificsei whales were those presented at the previous JARPNII Review workshop in 2009 (Kanda et al. 2009)
as well as those presented at more recent IWC/SC meeting (Kanda et al. 2013). These studies, using
multiple sets of microsatellite DNA loci and mtDNA markers, examined sei whales samples collectedfrom almost the entire range of North Pacific.
Kanda et al. (2009), on the one hand, analyzed genetic variation at 17 microsatellite DNA loci and 487bp
of mitochondrial DNA (mtDNA) control region sequences in the JARPNII samples (n=489) from 2002 to2007 in the area between 143°E and 170°E as well as in the commercial whaling samples (n=301) from1972 and 1973 conducted in the area between 165°E and 139°W. The results indicated no evidence ofsignificant genetic differences within as well as between the JARPNII and commercial whaling samples.
Both females and males showed same pattern of the stock structure. Sequencing and phylogenetic
analysis of the mtDNA control region also showed no evidence of the genetic heterogeneity in the
JARPNII samples as well as no spatially or temporally unique phylogenetic clusters.
Kanda et al. (2013), on the other hand, examined genetic variations at 14 microsatellite DNA loci in the
North Pacific sei whale using biopsy samples obtained from the IWC/POWER (International Whaling
Commission/Pacific Ocean Whale and Ecosystem Research; hereafter POWER) surveys that covered the
173°E - 172°W area of the central North Pacific in 2010 (n=13), 170°W - 150°W area of the central
North Pacific in 2011 (n=29), and 150°W - 135°W area of the eastern North Pacific in 2012 (n=35), andthese obtained data was analyzed with those in Kanda et al. (2009). This study allowed the authors to
examine temporal (40 years apart between the POWER and commercial whaling data) and spatial (143°E
to 135°W area divided into western, central and eastern) genetic differences of the North Pacific sei
whales. Similarly to Kanda et al. (2009), the results showed no evidence of the temporal genetic
differences between the recent POWER and past commercial whaling samples collected from the same
area and no evidence of the spatial genetic differences among the western, central and eastern samples.

1One drawback to these two studies was that there was no direct comparison among samples collected at
the same time of the year from the different areas over the North Pacific. Considering that sei whales
conduct seasonal migration from their breeding ground to feeding ground every year, development ofstock structure hypothesis should test the genetic differentiation in the samples collected in the same yearthat eliminate temporal negative biases. If no genetic difference is found, it should strongly indicate noevidence of multiple stocks in the area. Kanda et al. (2015a) (SC/F16/JR47) looked at genetic variation at
the microsatellite DNA loci to analyze the JARPNII and POWER samples collected from the same timeof years in 2010, 2011 and 2012, respectively. Again the study failed to demonstrate evidence of multiple
stocks of sei whales in the North Pacific.
The in-depth assessment of North Pacific sei whale started at the 2015 IWC SC meeting. The IWC SC
agreed to proceed with two initial alternative stock structure hypotheses: i) a single stock in the entire
North Pacific as proposed by Kanda et al. (2015a;b), based on several pieces of evidences included thegenetics; and ii) a five-stock hypothesis proposed in Mizroch (2015), based mainly on the interpretationof mark-recapture data: Japan coastal; North Pacific pelagic; Aleutian Islands and Gulf of Alaska; eastern
North Pacific migratory; and Southern North American coastal stock (coastal California) (IWC, 2015).
The IWC SC agreed that discriminating between these two hypotheses is difficult in the absence ofgenetic data from the potentially extirpated stocks, and thus both hypotheses are plausible (IWC, 2015).
The IWC SC agreed that the oceanic regions of the North Pacific are composed by a single stock (IWC,2015).
In this study the total samples obtained by the surveys of JARPNII between 2002 and 2014,
IWC/POWER in 2010-2012 and from past commercial whaling in 1972 and 1973 are analyzed to further
examine the spatial population genetic structure of sei whale in the North Pacific, in particular to examine
the plausibility of the ‘North Pacific pelagic’ stock.
MATERIALS AND METHODS
Samples
JARPNII samples (n=1174) of sei whales obtained from 2002 to 2014 were collected from the western
North Pacific (Table 1 and Figure 1). Although sampling dates and locations of the surveys slightly
differed year by year depending on the sampling plan of a given year, samples were taken in the in thenorthwestern North Pacific in the range 35°05’N-49°35’N, and 143°19’E-169°58’E.
Skin biopsy samples of sei whales were obtained during the POWER surveys. POWER survey covered
the area north of 40°N from 173°E to 172°W in 2010 (10POWER), from 170°W to 150°W in 2011(11POWER), and from 150°W to 135°W in 2012 (12POWER) (Matsuoka et al., 2011, 2012, 2013). A
total of 78 POWER biopsy samples were used (Table 1 and Figure 1).
A total of 302 genetic samples from past commercial whaling in 1972 and 1973 were included in theanalyses. Individual samples were captured in the sector comprised approximately between 165°E and139°W (Table 1 and Figure 1).
DNA extraction
The IWC guidelines for DNA data quality (IWC, 2009) were followed as much as possible (see Kanda etal., 2014).
Total DNA from each of the whales was extracted from 0.05 g of skin tissue in the JARPNII samples,skin biopsy in the POWER samples and from blood tissues in the commercial samples using the protocol
of Sambrook et al. (1989). Extracted DNA was stored in TE buffer (10 mM Tris-HCl, 1 mM EDTA, pH
8.0).
Microsatellite analysis
Genetic variation at microsatellite loci were analyzed using 17 sets of primers, none of which was
designed specifically from sei whales: EV1, EV14, EV21, EV94, EV104 (Valsecchi and Amos, 1996),
GT011 (Bérubé et al., 1998), GT23, GT211, GT271, GT310, GT575 (Bérubé et al., 2000), GATA28,

2

GATA53, GATA98, GATA417, GGAA520 (Palsbøll et al., 1997), and DlrFCB17 (Buchanan et al.,1996). Primer sequences and PCR cycling profiles generally followed those of the original authors.
PCR amplifications were performed in 15l reaction mixtures containing 10-100ng of DNA, 5 pmole ofeach primer, 0.625 units of Ex Taq DNA polymerase (Takara Shuzo), and 2mM of each dNTP, and 10x
reaction buffer containing 20mM MgCl2 (Takara Shuzo). Amplified products with internal size standard(GENESCAN400HD, Applied Biosystems Japan) were run on a 6% polyacrylamide denaturating gel(Long Ranger) using BaseStation100 DNA fragment analyzer (Bio-Rad). Although alleles werevisualized using Cartographer software specifically designed for the BaseStation, allelic sizes were
determined manually in relation to the internal size standard and sei whale’s DNA of known size thatwere rerun on each gel.
Data analysis
Levels of polymorphisms
The number of alleles per locus, expected heterozygosity per locus and inbreeding coefficient wascalculated using FSTAT 2.9.3 (Goudet, 1995). Statistical tests for the deviations from expected HardyWeinberg genotypic proportions were conducted using GENEPOP 4.0 (Rousset, 2008).
Homogeneity test
In order to detect genetic differences, conventional hypothesis testing procedure was conducted using
heterogeneity test in frequencies of the microsatellite alleles among sectors. Null hypothesis to be tested
was if the samples came from a genetically same group of sei whales. If statistically significant allele
frequency differences exist, then it could indicate these samples came from genetically different stocks ofsei whales. Probability test (or Fisher’s exact test) implemented in GENEPOP 4.0 (Rousset, 2008) wasused to conduct the heterogeneity test. Statistical significance was determined using the chi-square value
obtained from summing the negative logarithm of p-values over the 17 microsatellite loci (Sokal andRohlf, 1995). The False Discovery Rate (FDR) approach (Benjamini and Yekutieli, 2001) was used for
adjustment of p-value in case of multiple comparisons. FST was calculated using FSTAT 2.9.3 (Goudet,
1995).
Mitochondrial DNA
Sequencing analysis of the 487bp control region of mtDNA was conducted using the primers light-strand
MT4 (Árnason et al., 1993) and heavy-strand P2 (5'-GAAGAGGGATCCCTGCCAAGCGG-3'; Hori etal., unpublished). PCR products were purified by MicroSpin S-400HR columns (Pharmacia Biotech).
Cycle sequencing was performed with the same primers, using BigDye terminator cycle sequence Kit(Applied Biosystems, Inc). The cycle sequencing products were purified by AutoSeq G-50 spin Columns(Pharmacia Biotech). The labeled sequencing fragments were resolved by electrophoresis through a 5%
denaturing polyacrylamide matrix on an ABI 377 or ABI3100 Automated DNA Sequencer (Applied
Biosystems, Inc), following the protocols of the manufacture. For each sample both strands weresequenced.
Data analysis
Level of polymorphisms
The number of haplotypes and haplotype diversity were calculated following Nei (1987). The nucleotide
diversity (Nei, 1987: equation 10.5) and its standard error for population sampling and stochastic
processes were calculated from the pair-wise differences between the mtDNA sequences using theKimura’s 2- parameter adjustment (Kimura, 1980).
Homogeneity test
Conventional hypothesis testing procedure was conducted using heterogeneity test in mtDNA haplotype
frequencies among the samples. The randomized chi-square Test of Independence (Roff and Bentzen,
1989) and the conventional FST were used to investigate the spatial differentiation of mtDNA variation. In
each test a total of 10,000 permutations of the original data were performed. Tests were conducted for all
samples combined as well for males and females separately. A p-value smaller than 0.05 was used as acriterion to reject the null hypothesis of panmixia. The FDR approach was used for adjustment of p-value
in case of multiple comparisons. FST for mtDNA was calculated based on the analysis of molecularvariance (AMOVA) (Excoffier et al., 1992).

3Phylogenetic analyses
The genealogy of the mtDNA haplotypes was estimated using the Neighbor-Joining method (Saitou andNei 1987) as implemented in the program PHYLIP (Felsenstein 1993). Genetic distances among
haplotypes were estimated using the program DNADIST of PHYLIP, based on Kimura’s 2-parametermodel (Kimura 1980). A transition-transversion ratio of 5:1was used. The genealogy was rooted using thehomologous sequence from Bryde’s and Omura’s whales. To estimate support for each node a total of
1,000 bootstrap simulations were conducted and the majority-rule consensus genealogy estimated.
RESULTS
Microsatellites
Level of polymorphisms
All 17 loci analyzed were polymorphic (Table 2). The total number of alleles per locus ranged from threeat the GATA53 to 23 at the EV14 with an average of 9.71. Expected heterozygosity at each of the lociranged from 0.14 at GT271 to 0.87 at DlrFCB with an average of 0.64. No significant departure from theexpected Hardy-Weinberg genotypic proportions was found.
Homogeneity test
No significant genetic heterogeneity was found between Western and Eastern sectors for each locus aswell for all loci combined. Results were the same for male, female and both sexes combined (Table 3).
Mitochondrial DNA
Level of polymorphism
Levels of mtDNA diversity were relatively high in the North Pacific sei whale (Table 4).
Homogeneity test
No significant genetic heterogeneity was found between Western and Eastern sectors. Results were thesame for male, female and both sexes combined (Table 5).
DISCUSSION
As informed earlier the in-depth assessment of North Pacific sei whale started at the 2015 IWC SC with
two initial alternative stock structure hypotheses: i) a single stock in the entire North Pacific as proposedby Kanda et al. (2015a;b), based on several pieces of evidences included the genetics; and ii) a five-stock
hypothesis proposed in Mizroch (2015), based mainly on the interpretation of mark-recapture data: Japan
coastal; North Pacific pelagic; Aleutian Islands and Gulf of Alaska; eastern North Pacific migratory; andSouthern North American coastal stock (coastal California) (IWC, 2015). As noted earlier the IWC SC
agreed that discriminating between these two hypotheses is difficult in the absence of genetic data fromthe potentially extirpated stocks, and thus both hypotheses are plausible (IWC, 2015).
The main purpose of this study was to examine genetically all the available genetic samples of the sei
whale in the North Pacific in order to confirm the hypothesis of a single stock in the oceanic regions of
the North Pacific (the ‘North Pacific pelagic’ in the second stock structure hypothesis indicated above).
As noted by the IWC SC it is not possible to check the plausibility of other putative stocks under thesecond hypothesis using genetics analyses because no genetic samples are available from the regions
where these putative stocks are proposed.
Results of the present analysis are in agreement with previous genetic analyses based on smaller sample
sizes (Kanda et al., 2009; 2015a: SC/F16/JR47). Kanda et al. (2015b: SC/F16/JR48) analyzed all nongenetic evidences that were consistent with the single stock in oceanic regions. In fact, the genetic andnon-genetic evidences summarized by Kanda et al. (2015b: SC/F16/JR48) were more consistent with thefirst hypothesis above, a single stock of sei whales in the whole North Pacific.
It is considered that the evidences for proposing the second stock structure hypothesis (five stocks) are
weak and that the IWC SC should evaluate objectively the plausibility of the additional putative stock
other than the ‘North Pacific pelagic’.

4

ACKNOWLEDGEMENTS
We gratefully acknowledge the researchers and crew members that participated in JARPN/JARPNII and
IWC/POWER surveys for the collection of genetic samples of the sei whale. We thank H. Oikawa and S.
Azumi (ICR) who collaborated in the process of DNA extraction. We also thank N. Kanda (JANUSJapan) for preparing the microsatellite data set used in this study.
REFERENCES
Árnason, Ú., Gullberg, A. and Widegten, B. 1993. Cetacean mitochondrial DNA control region:
Sequences of all extant baleen whales and two sperm whale species. Mol. Biol. Evol., 10, 960-970.
Benjamini, Y. and Yekutieli, D. 2001. The control of the false discovery rate in multiple testing under
dependency. The Annals of Statistics. 29, No. 4, 1165–1188
Bérubé, M., Aguilar, A., Dendanto, D., Larsen, F., Notarbartolo-di-Sciara, G., Sears, R., Sigurjónsson, J.,
Urban-Ramirez, J., and Palsbøll, P.J. 1998. Population genetic structure of North Atlantic,
Mediterranean Sea and Sea of Cortez fin whales, Balaenoptera physalus (Linnaeus, 1758); analysisof mitochondrial and nuclear loci. Mol. Ecol. 7:585-599.
Bérubé, M., Jørgensen, H., Mcewing, R., and Palsbøll, P.J. 2000. Polymorphic di-nucleotide
microsatellite loci isolated from the humpback whale, Megaptera novaeanglliae. Mol. Ecol. 9:21812183.
Buchanan, F.C., Friesen, M.K., Littlejohn, R.P., and Clayton, J.A. 1996. Microsatellites from beluga
whale Delphinapterus leucas. Mol. Ecol. 5:571-575.
Excoffier, L., Smouse, P.E. and Quattro, J.M. 1992. Analysis of molecular variance inferred from metricdistances among DNA haplotypes: application to human mitochondrial DNA restriction data.
Genetics 131: 479-491
Felsenstein, J. 1993. PHYLIP (Phylogeny Inference Package) 3.5c. University of Washington, Seattle,
USA.
Goudet, J. 1995. FSTAT, version 1.2: a computer program to calculate F-statistics. J. Hered. 86:485-486.
International Whaling Commission. 2009. Report of the Scientific Committee. Annex I. Report of theworking group on stock definition. Appendix 2. Guidelines for DNA data quality control for genetic
studies relevant to IWC management advice. J. Cetacean Res. Manage. (Suppl.) 11:252-256.
International Whaling Commission. 2015. Report of the Scientific Committee, Annex G. Report of the
Sub-Committee on In-Depth Assessments. J. Cetacean Res. Manage. 16 (suppl.): 176-195.
Kanda, N., Goto, M., Yoshida, H., and Pastene, L.A. 2009. Stock structure of sei whales in the North
Pacific as revealed by microsatellites and mitochondrial DNA analyses. Paper SC/J09/JR32 presented
to the JARPN II Review Workshop, Tokyo, January 2009 (unpublished).
Kanda, N., Matsuoka, N., Yoshida, H. and Pastene, L. A. 2013. Microsatellite DNA analysis of sei
whales obtained from the 2010-2012 IWC-POWER. Paper SC/65a/IA05 presented to IWC ScientificCommittee, Jeju Island, Republic Korea, June 2013, (unpublished) 6pp.
Kanda, N., Goto, M., Oikawa, H. and Pastene, L.A. 2014. Update of note on sampling and laboratory
procedure protocols of the genetic work at the Institute of Cetacean Research (SC/65b/J27Rev).
Paper SC/65b/DNA01 presented to the IWC Scientific Committee, Bled, Slovenia, May 2014
(unpublished). 6pp.
Kanda, N., Matsuoka, K., Goto, M. and Pastene, L.A. 2015a. Genetic study on JARPNII and IWCPOWER samples of sei whales collected widely from the North Pacific at the same time of the year.
Paper SC/66a/IA8 presented to the IWC Scientific Committee, San Diego, May 2015 (unpublished).
8pp.
Kanda, N., Bando, T., Matsuoka, K., Murase, H., Kishiro, T., Pastene, L.A. and Ohsumi, S. 2015b. A
review of the genetic and non-genetic information provides support for a hypothesis of a single
stock of sei whales in the North Pacific. Paper SC/66a/IA9 presented to the IWC ScientificCommittee, San Diego, May 2015 (unpublished). 17pp.
Kimura, M. 1980. A simple method for estimating evolutionary rates of base substitutions throughcomparative studies of nucleotide sequences. J. Mol. Evol. 16: 111-120.
Matsuoka, K., Hakala, S., Kim, H.Y., Aki, M., and Shinyashiki, Y. 2011. Cruise report for the 2010
IWC/Japan joint cetacean sighting survey in the North Pacific. Paper SC/63/O5 presented to the IWC
Scientific Committee May 2011, Tromso, Norway (unpublished).

5Matsuoka, K., Mizroch, S. and Komiya, H. 2012. Cruise report of the 2011 IWC-Pacific Ocean Whaleand Ecosystem Research (IWC-POWER). Paper SC/64/IA5 presented to IWC Scientific Committee,
June 2012, Panama City, Panama (unpublished) 27pp.
Matsuoka, K., Mizroch, S., An, Y.-R., Kumagai, S. and Hirose, K. 2013. Cruise report of the 2012 IWCPacific Ocean Whale and Ecosystem Research (IWC-POWER). Paper SC/65a/IAXX presented to
the 65th IWC Scientific Committee, June 2013 (unpublished).
Mizroch, S.A., Conn, P.B. and AND Rice, D.W. 2015. The mysterious sei whale: Its distribution,
movements and population decline in the North Pacific revealed by whaling data and recoveries ofDiscovery-type marks. Paper SC/66a/IA14 presented to the IWC Scientific Committee, San Diego,
May 2015 (unpublished). 112pp.
Nei, M. 1987. Molecular Evolutionary Genetics. Columbia University Press, New York.
Palsbøll, P.J., Bérubé, M., Larsen, A.H., and Jørgensen, H. 1997. Primers for the amplification of tri-and
tetramer microsatellite loci in baleen whales. Mol. Ecol. 6:893-895.
Roff, D.A., and Bentzen, P. 1989. The statistical analysis of mtDNA polymorphisms: χ 2 and the problem
of small samples. Mol. Biol. Evol., 6, 539-545
Rousset, F. 2008. Genepop'007: a complete re-implementation of the genepop software for Windows andLinux. Molec. Ecol. Resources 8:103-106.
Saitou, N. and Nei, M. 1987. The neighbor-joining method: a new method for reconstructing phylogenetic
trees. Mol. Biol. Evol. 4(4):406-25.
Sambrook, J., Fritsch, E.F., and Maniatis, T. 1989. Molecular cloning: A laboratory manual. 2nd Ed.,
Cold Spring Harbor, NY: Cold Spring Harbor Laboratory.
Sokal, R.R., and Rohlf, F.J. 1995. Biometry: the Principles of Statistics in Biological Research.
Freeman and Company, New York.
Valsecchi, E., and Amos, W. 1996. Microsatellite markers for the study of cetacean populations. Mol.
Ecol. 5:151-156.

6

Table 1. Sample sizes of sei whales used in the present study for the microsatellite and mtDNA (figuresin parenthesis) analyses, by longitudinal sector, sex, and source of samples. Only the samples genotyped
for the complete microsatellite loci set were included in the analysis. Western and Eastern sectors weredivided at 180°.
Data source
JARPNII
POWER
Commercial

Sex

SectorWestern
551 (551)
623 (622)
1 (1)
1 (1)
88 (87)92 (88)1356 (1350)

Male
FemaleMale
FemaleMale
Female

Total

Total
Eastern

36 (36)40 (39)67 (71)55 (57)198 (203)551 (551)
623 (622)
37 (37)41 (40)155 (158)
147 (145)
1554 (1553)

Table 2. The number of alleles (A), expected heterozygosity (He), test results for expected HardyWeinberg genotypic proportion (HW) and inbreeding coefficient (FIS) in North Pacific sei whale, at 17
microsatellite loci.
Microsatellite loci

A

EV21

6

GGAA52

HE

HW

FIS

0,65

0,714

-0,008

9

0,80

0,871

0,015

GATA98

7

0,74

0,228

0,009

GT211

6

0,31

0,020

0,010

EV14

23

0,86

0,422

0,005

GATA53

3

0,49

0,816

0,011

EV1

17

0,84

0,750

0,016

EV94

8

0,69

0,520

-0,030

GT23

14

0,60

0,674

0,026

GT575

6

0,59

0,561

0,032

GATA41

9

0,78

0,771

0,010

GT310

5

0,49

0,574

-0,032

EV104

10

0,72

0,839

-0,008GATA28

11

0,81

0,858

0,011

GT271

4

0,14

0,727

0,004

GT011

6

0,45

0,920

0,008

DlrFCB

21

0,87

0,471

0,007

Average

9,71

0,64

0,939

0,005

7

Table 3. Results of the heterogeneity test for sei whales between Western and Eastern longitudinal
sectors, by sex and locus.
Both sex combined
Male
FemaleMicrosatellite lociP -values
F ST
P -values
F ST
P -values
F ST
EV21
0,221
0,001
0,072
0,001
0,930
-0,002GGAA5200,759-0,001
0,834-0,001
0,831-0,001
GATA980,774-0,001
0,543
0,000
0,932
-0,003GT211
0,394-0,001
0,739-0,001
0,416-0,001EV14
0,623-0,001
0,607-0,0040,723-0,001
GATA530,798-0,001
0,772-0,0020,897-0,003EV1
0,100-0,001
0,088
0,000
0,026
-0,001
EV94
0,638
0,001
0,353
0,004
0,981
-0,002GT23
0,673-0,001
0,430
0,001
0,140
-0,002GT575
0,182-0,001
0,175
0,000
0,245
0,005
GATA417
0,329
0,000
0,359
-0,0040,511-0,001
GT310
0,144
0,000
0,216
0,000
0,795
-0,002
EV104
0,223
0,002
0,707
-0,001
0,092
0,003
GATA28
0,130
0,000
0,407
-0,001
0,199
0,000
GT271
0,829
-0,001
0,749-0,001
0,820-0,003GT011
0,456-0,001
0,805-0,0020,263-0,002
DlrFCB17
0,181
0,000
0,067
0,000
0,331
-0,001
Overall
0,393
0,000
0,415
-0,001
0,543-0,001

Table 4. Results of mtDNA diversity for North Pacific sei whale.
Number of haplotypes
Nucleotide diversity (SE)82
0.00794 (0.00008)

Haplotype diversity
0.9275

Table 5. Results of the mtDNA heterogeneity test between Western and Eastern sectors, by sex.
Western × EasternChi-square p-value

Sex combined
0.1071Male
0.3549Female0.0991

Sex combined
0.00028

8

FST
Male
-0.00021

Female0.00111

130E

140E

150E

160E

170E

180E

170W

160W

150W

140W

130W

55N

55N

45N

45N

35N

35N

25N
130E

140E

150E

160E

170E

180E

170W

160W

150W

140W

25N
130W

Figure 1. Sampling locations of sei whales used in the present genetic study. Blue: JARPNII samples;
Red: past commercial whaling samples; Green: IWC/POWER samples. For the statistical analyses
samples were arbitrarily divided into two sectors: Western and Eastern at 180°.

9

Figure 2. Phylogenetic relationships among North Pacific sei whale mtDNA haplotypes and frequenciesof haplotypes in two longitudinal sectors.

10