Beacham et al. : Population structure of Oncorhynchus gorbuscha in British Columbia and Washington, determined with microsatellites 
245 
Figure 1 
Map of British Columbia and northern Washington coasts indicating the general geographic regions 
where pink salmon (Oncorhynchus gorbuscha) from 146 odd-year and 116 even-year populations 
were surveyed, with the regions listed in Table 2. The regions depicted in the figure are the fol- 
lowing: 1 Washington; 2 lower Fraser River; 3 upper Fraser River; 4 east coast Vancouver Island 
(ECVI); 5 southern British Columbia; 6 central coast; 7 Skeena River; 8 north coast; and 9 Queen 
Charlotte Islands. In 6 of these regions (ECVI, southern British Columbia mainland, central coast, 
Skeena River, north coast, Queen Charlotte Islands), pink salmon spawn in both even and odd 
years. Because 6 regions have both broodlines present, the map encompasses 12 regional groups of 
populations when even and odd populations are separated. The other 3 regional groups (upper and 
lower Fraser River, and Washington) have pink salmon only in odd years. This summary accounts 
for the 15 regional groups outlined in Table 2. 
genetic distances among all populations. An unrooted 
neighbor-joining tree based upon CSE was generated 
with NJPLOT (Perriere and Gouy, 1996). Bootstrap 
support for the major nodes in the tree was evalu- 
ated with the CONSENSE program from PHYLIP 
based upon 500 replicate trees (Felsenstein, 1993). 
The distribution of genetic variation in pink salmon 
was evaluated with a gene diversity analysis with 
the analysis structured between broodlines, among 
regions within broodlines, and among populations 
within regions. The analysis was conducted with GDA, 
which will support a maximum of three nested levels 
of variation in addition to the error mean square. All 
populations outlined in Table 2 were included in the 
analysis. Allele frequencies for all location samples 
surveyed in this study are available at the Molecular 
Genetics Laboratory website http://www.pac.dfo-mpo. 
gc.ca/science/facilities-installations/pbs-sbp/mgl-lgm/ 
data-donnees/index-eng.htm . 
Results 
Variation within populations 
Variation was displayed in the number of observed 
alleles at the 16 microsatellite loci surveyed in the 
study. The fewest number of alleles was observed at 
Ots7e (12 alleles odd-year broodline, 13 alleles even- 
year broodline), and the greatest number of alleles 
was observed at OkilO (85 alleles odd-year broodline, 
83 alleles even-year broodline) (Table 3). Heterozy- 
gosities were generally above 90%, with notable excep- 
tions observed at Ots7e (both broodlines) and Onelll 
(odd-year only). Genotypic frequencies at all 16 loci 
surveyed typically conformed to those expected under 
Hardy-Weinberg equilibrium (HWE) for populations in 
both broodlines. Greater overall population differen- 
tiation was observed in the odd-year broodline ( F sr = 
0.005) than in the even-year broodline ( F ST =0.002). 
