Nelson et al.: Population structure of Oncorhynchus tshawytscha of the Fraser River 
103 
KL L 
Ots 101 
L 
-300 
-200 
KL L 
Ots 100 
L 
-400 
-300 
K L L 
Ots 102 
L 
-300 
-280 
-260 
-240 
-220 
-200 
-180 
Figure 2 
Photographs of nondenaturing polyacrylamide gels stained with ethidium bro- 
mide showing typical alleles for OfslOl, OfslOO, and Ofsl02. “K” indicates the 
1-kilobase-pair ladder and “L" indicates the 20 base-pair ladder. 
erozygosity values had a wider range at Ots 102, ranging 
from a low of 0.297 in Eagle River to a high of 0.9 in Che- 
halis-red (average of 0.706). The apparently low hetero- 
zygosity found in some populations at Ots 102 may have 
been partially due to the presence of a null allele. With 
the exception of Bridge River, all allele frequencies showed 
significant variation among the different populations. In 
pairwise tests, Bridge River was not significantly differ- 
ent ( P nondifferentiation=0. 00004) from Harrison River, 
Chilliwack-white, Chilliwack-red, Chehalis-red, Coldwater 
River, Middle Shuswap River, Eagle River, Stuart River, 
and Cottonwood River. All other populations were signifi- 
cantly different from each other. 
Hardy-Weinberg equilibrium and treatment 
of the null allele 
We tested each of the 20 populations for significant devi- 
ations from HWE proportions at each locus. Conforma- 
tion to HWE was rejected at the 5% level (P<0. 05/20) in 
four populations (Harrison River, Tete Jaune River, Cot- 
tonwood River, and Eagle River) at OfslOl, in one pop- 
ulation (Bridge River) at Ots 100, and in 12 populations 
at Ots 102 (see Table 1). All rejections of conformation 
to HWE were due to a deficiency of heterozygotes. 
Single locus F ls values for OfslOl, OfslOO, and Ofsl02 
were 0.079, 0.050, and 0.261, respectively, and 0.127 for 
