Beacham et aL: Geographic basis for population structure in Oncorhynchus tshawytscha 



231 



Figure 1 



Locations in the Fraser River drainage where 52 chinook salmon spawning aggregates were 

 sampled at least once during 1988-98. 



protocol of Miller et al. (1996) (early extractions) or the 

 chelex resin protocol of Small et al. (1998) (later extrac- 

 tions). Samples were derived from adults in all areas except 

 the McGregor River where, because of the difficulty of 

 obtaining adults, juveniles were sampled (Fig. 1). Samples 

 of adults were obtained from hatcheries during egg collec- 

 tions, from wild spawning fish or carcasses on the spawning 

 grounds, or in the case of the Chilcotin River sample, from 

 a mixed sample of angled fish from the river. 



For the survey of baseline populations, PCR products at 

 six microsatellite loci— O^siOO, OtslOl, OtslO'I, Otsl04, 

 OtslOV (primers outlined by Nelson and Beacham, 1999) 

 and Ssal97 (O'Reilly et al., 1996) — were size-fractionated 

 on nondenaturing polyacrylamide gels by staining with 



0.5 mg/mL ethidium bromide in water and illuminating 

 with ultraviolet light. Nelson et al. (1998, 2001) have pro- 

 vided a more complete description of gel electrophoretic 

 conditions. Three 20-bp marker lanes (Gensura Labs Inc., 

 Del Mar, CA), 24 population samples, and one standard fish 

 were run on each gel. The size of the amplified alleles were 

 determined from the molecular size grid created with the 

 20-bp markers. Digital images of the resulting gels were 

 analyzed by using Biolmage Whole Band software (Mil- 

 lipore Corp. Imaging Systems, Ann Arbor, MI). Beacham 

 and Wood ( 1999) provided a more complete description of 

 the methods used to identify alleles with this technology. 

 Precision of estimation of allele size with this technology 

 has been outlined for OtslOO, OtslOl, and Otsl02 by Nel- 



